Characterizing the Survey Strategy and Initial Orbit Determination Abilities of the NASA MCAT Telescope for Geosynchronous Orbital Debris Environmental Studies

NASA Astrophysics Data System (ADS)

Frith, J.; Barker, E.; Cowardin, H.; Buckalew, B.; Anz-Meador, P.; Lederer, S.

The National Aeronautics and Space Administration (NASA) Orbital Debris Program Office (ODPO) recently commissioned the Meter Class Autonomous Telescope (MCAT) on Ascension Island with the primary goal of obtaining population statistics of the geosynchronous (GEO) orbital debris environment. To help facilitate this, studies have been conducted using MCAT’s known and projected capabilities to estimate the accuracy and timeliness in which it can survey the GEO environment, including collected weather data and the proposed observational data collection cadence. To optimize observing cadences and probability of detection, on-going work using a simulated GEO debris population sampled at various cadences are run through the Constrained Admissible Region Multi Hypotheses Filter (CAR-MHF). The orbits computed from the results are then compared to the simulated data to assess MCAT’s ability to determine accurately the orbits of debris at various sample rates. The goal of this work is to discriminate GEO and near-GEO objects from GEO transfer orbit objects that can appear as GEO objects in the environmental models due to the short arc observation and an assumed circular orbit. The specific methods and results are presented here.

Acceleration environment of payloads while being handled by the Shuttle Remote Manipulator System

NASA Technical Reports Server (NTRS)

Turnbull, J. F.

1983-01-01

Described in this paper is the method used in the Draper Remote Manipulator System (RMS) Simulation to compute linear accelerations at the point on the SPAS01 payload where its accelerometers are mounted. Simulated accelerometer output for representative on-orbit activities is presented. The objectives of post-flight analysis of SPAS01 data are discussed. Finally, the point is made that designers of acceleration-dependent payloads may have an interest in the capability of simulating the acceleration environment of payloads while under the control of the overall Payload Deployment and retrieval System (PDRS) that includes the Orbiter and its attitude control system as well as the Remote Manipulator Arm.

Study of Kapton Degradation under Simulated Shuttle Environment

NASA Technical Reports Server (NTRS)

Eck, T. G.; Hoffman, R. W.

1985-01-01

Weight loss and severe degradation of the surface of Kapton that occurs in low Earth orbit is studied. Atomic oxygen, the major ambient species at low Earth altitude and incident with approximately 5 eV energy in ram conditions, is the primary suspect, but a thorough study of oxygen-Kapton interactions has not yet been carried out. A low-energy ion source is used to simulate the shuttle low Earth orbit environment. This source, together with diagnostic tools including surface analysis and mass spectroscopic capability, is being used to carry out experiments from which quantum yields may be obtained.

Methods of Helium Injection and Removal for Heat Transfer Augmentation

NASA Technical Reports Server (NTRS)

Haight, Harlan; Kegley, Jeff; Bourdreaux, Meghan

2008-01-01

While augmentation of heat transfer from a test article by helium gas at low pressures is well known, the method is rarely employed during space simulation testing because the test objectives usually involve simulation of an orbital thermal environment. Test objectives of cryogenic optical testing at Marshall Space Flight Center's X-ray Cryogenic Facility (XRCF) have typically not been constrained by orbital environment parameters. As a result, several methods of helium injection have been utilized at the XRCF since 1999 to decrease thermal transition times. A brief synopsis of these injection (and removal) methods including will be presented.

Methods of Helium Injection and Removal for Heat Transfer Augmentation

NASA Technical Reports Server (NTRS)

Kegley, Jeffrey

2008-01-01

While augmentation of heat transfer from a test article by helium gas at low pressures is well known, the method is rarely employed during space simulation testing because the test objectives are to simulate an orbital thermal environment. Test objectives of cryogenic optical testing at Marshall Space Flight Center's X-ray Calibration Facility (XRCF) have typically not been constrained by orbital environment parameters. As a result, several methods of helium injection have been utilized at the XRCF since 1999 to decrease thermal transition times. A brief synopsis of these injection (and removal) methods including will be presented.

Effects of High-Density Impacts on Shielding Capability

NASA Technical Reports Server (NTRS)

Christiansen, Eric L.; Lear, Dana M.

2014-01-01

Spacecraft are shielded from micrometeoroids and orbital debris (MMOD) impacts to meet requirements for crew safety and/or mission success. In the past, orbital debris particles have been considered to be composed entirely of aluminum (medium-density material) for the purposes of MMOD shielding design and verification. Meteoroids have been considered to be low-density porous materials, with an average density of 1 g/cu cm. Recently, NASA released a new orbital debris environment model, referred to as ORDEM 3.0, that indicates orbital debris contains a substantial fraction of high-density material for which steel is used in MMOD risk assessments [Ref.1]. Similarly, an update to the meteoroid environment model is also under consideration to include a high-density component of that environment. This paper provides results of hypervelocity impact tests and hydrocode simulations on typical spacecraft MMOD shields using steel projectiles. It was found that previous ballistic limit equations (BLEs) that define the protection capability of the MMOD shields did not predict the results from the steel impact tests and hydrocode simulations (typically, the predictions from these equations were too optimistic). The ballistic limit equations required updates to more accurately represent shield protection capability from the range of densities in the orbital debris environment. Ballistic limit equations were derived from the results of the work and are provided in the paper.

Computer simulation of on-orbit manned maneuvering unit operations

NASA Technical Reports Server (NTRS)

Stuart, G. M.; Garcia, K. D.

1986-01-01

Simulation of spacecraft on-orbit operations is discussed in reference to Martin Marietta's Space Operations Simulation laboratory's use of computer software models to drive a six-degree-of-freedom moving base carriage and two target gimbal systems. In particular, key simulation issues and related computer software models associated with providing real-time, man-in-the-loop simulations of the Manned Maneuvering Unit (MMU) are addressed with special attention given to how effectively these models and motion systems simulate the MMU's actual on-orbit operations. The weightless effects of the space environment require the development of entirely new devices for locomotion. Since the access to space is very limited, it is necessary to design, build, and test these new devices within the physical constraints of earth using simulators. The simulation method that is discussed here is the technique of using computer software models to drive a Moving Base Carriage (MBC) that is capable of providing simultaneous six-degree-of-freedom motions. This method, utilized at Martin Marietta's Space Operations Simulation (SOS) laboratory, provides the ability to simulate the operation of manned spacecraft, provides the pilot with proper three-dimensional visual cues, and allows training of on-orbit operations. The purpose here is to discuss significant MMU simulation issues, the related models that were developed in response to these issues and how effectively these models simulate the MMU's actual on-orbiter operations.

Simulation of the Effect of Realistic Space Vehicle Environments on Binary Metal Alloys

NASA Technical Reports Server (NTRS)

Westra, Douglas G.; Poirier, D. R.; Heinrich, J. C.; Sung, P. K.; Felicelli, S. D.; Phelps, Lisa (Technical Monitor)

2001-01-01

Simulations that assess the effect of space vehicle acceleration environments on the solidification of Pb-Sb alloys are reported. Space microgravity missions are designed to provide a near zero-g acceleration environment for various types of scientific experiments. Realistically. these space missions cannot provide a perfect environment. Vibrations caused by crew activity, on-board experiments, support systems stems (pumps, fans, etc.), periodic orbital maneuvers, and water dumps can all cause perturbations to the microgravity environment. In addition, the drag on the space vehicle is a source of acceleration. Therefore, it is necessary to predict the impact of these vibration-perturbations and the steady-state drag acceleration on the experiments. These predictions can be used to design mission timelines. so that the experiment is run during times that the impact of the acceleration environment is acceptable for the experiment of interest. The simulations reported herein were conducted using a finite element model that includes mass, species, momentum, and energy conservation. This model predicts the existence of "channels" within the processing mushy zone and subsequently "freckles" within the fully processed solid, which are the effects of thermosolutal convection. It is necessary to mitigate thermosolutal convection during space experiments of metal alloys, in order to study and characterize diffusion-controlled transport phenomena (microsegregation) that are normally coupled with macrosegregation. The model allows simulation of steady-state and transient acceleration values ranging from no acceleration (0 g). to microgravity conditions (10(exp -6) to 10(exp -3) g), to terrestrial gravity conditions (1 g). The transient acceleration environments simulated were from the STS-89 SpaceHAB mission and from the STS-94 SpaceLAB mission. with on-orbit accelerometer data during different mission periods used as inputs for the simulation model. Periods of crew exercise, quiet (no crew activity), and nominal conditions from STS-89 were used as simulation inputs as were periods of nominal. overboard water-dump, and free-drift (no orbit maneuvering operations) from STS-94. Steady-state acceleration environments of 0.0 and 10(exp -6) to 10(exp -1) g were also simulated, to serve as a comparison to the transient data and to assess an acceptable magnitude for the steady-state vehicle drag

A low Earth orbit molecular beam space simulation facility

NASA Technical Reports Server (NTRS)

Cross, J. B.

1984-01-01

A brief synopsis of the low Earth orbit (LEO) satellite environment is presented including neutral and ionic species. Two ground based atomic and molecular beam instruments are described which are capable of simulating the interaction of spacecraft surfaces with the LEO environment and detecting the results of these interactions. The first detects mass spectrometrically low level fluxes of reactively and nonreactively surface scattered species as a function of scattering angle and velocity while the second ultrahigh velocity (UHV) molecular beam, laser induced fluorescence apparatus is capable of measuring chemiluminescence produced by either gas phase or gas-surface interactions. A number of proposed experiments are described.

The Impact of New Trends in Satellite Launches on Orbital Debris Environment

NASA Technical Reports Server (NTRS)

Karacalioglu, Arif Goktug; Stupl, Jan

2016-01-01

The main goal of this study is to examine the impact of new trends in satellite launch activities on the orbital debris environment and collision risk. Starting from the launch of the first artificial satellite in 1957, space borne technology has become an indispensable part of our lives. More than 6,000 satellites have been launched into Earth orbit. Though the annual number of satellites launched stayed flat for many decades, the trend has recently changed. The satellite market has been undergoing a major evolution with new space companies replacing the traditional approach of deploying a few large, complex and costly satellites with an approach to use a multitude of smaller, less complex and cheaper satellites. This new approach creates a sharp increase in the number of satellites and so the historic trends are no longer representative. As a foundation for this study, a scenario for satellite deployments based on the publicly announced future satellite missions has been developed. These constellation-deploying companies include, but are not limited to, Blacksky, CICERO, EROS, Landmapper, Leosat, Northstar, O3b, OmniEarth, OneWeb, Orbcomm, OuterNet, PlanetIQ, Planet Labs, Radarsat, RapidEye Next Generation, Sentinel, Skybox, SpaceX, and Spire. Information such as the annual number of launches, the number of orbital planes to be used by the constellation, as well as apogee, perigee, inclination, spacecraft mass and area were included or approximated. Besides the production of satellites, a widespread ongoing effort to enhance orbital injection capabilities will allow delivery of more spacecraft more accurately into Earth orbits. A long list of companies such as Microcosm, Rocket Lab, Firefly Space Systems, Sierra Nevada Corporation and Arca Space Corporation are developing new launch vehicles dedicated for small satellites. There are other projects which intend to develop interstages with propulsive capabilities which will allow the deployment of satellites into their desired orbits beyond the restrictions of the launch vehicle used. These near future orbital injection technologies are also covered in the developed scenario. Using the above-mentioned background information, this study aims to examine how the orbital debris environment will be affected from the new dynamics of the emerging space markets. We developed a simulation tool that is capable of propagating the objects in a given deployment scenario with variable-sized time-steps as small as one second. Over the course of the run, the software also detects collisions; additional debris objects are then created according to the NASA breakup model and are fed back into the simulation framework. Examining the simulation results, the total number of particles to accumulate in different orbits can be monitored and the number of conjunctions can be tracked to assess the collision risks. The simulation makes it possible to follow the short- and long-term effects of a particular satellite or constellation on the space environment. Likewise, the effects of changes in the debris environment on a particular satellite or constellation can be evaluated. It is authors hope that the results of this paper and further utilization of the developed simulation tool will assist in the investigation of more accurate deorbiting metrics to replace the generic 25-year disposal guidelines, as well as to guide future launches toward more sustainable and safe orbits.

A Sensitivity Study on the Effectiveness of Active Debris Removal in LEO

NASA Technical Reports Server (NTRS)

Liou, J. C.; Johnson, Nicholas L.

2007-01-01

The near-Earth orbital debris population will continue to increase in the future due to ongoing space activities, on-orbit explosions, and accidental collisions among resident space objects. Commonly adopted mitigation measures, such as limiting postmission orbital lifetimes of satellites to less than 25 years, will slow down the population growth, but may be insufficient to stabilize the environment. The nature of the growth, in the low Earth orbit (LEO) region, is further demonstrated by a recent study where no future space launches were conducted in the environment projection simulations. The results indicate that, even with no new launches, the LEO debris population would remain relatively constant for only the next 50 years. Beyond that, the debris population would begin to increase noticeably, due to the production of collisional debris. Therefore, to better limit the growth of future debris population to protect the environment, remediation option, i.e., removing existing large and massive objects from orbit, needs to be considered. This paper does not intend to address the technical or economical issues for active debris removal. Rather, the objective is to provide a sensitivity study to quantify the effectiveness of various remediation options. A removal criterion based upon mass and collision probability is developed to rank objects at the beginning of each projection year. This study includes simulations with removal rates ranging from 2 to 20 objects per year, starting in the year 2020. The outcome of each simulation is analyzed, and compared with others. The summary of the study serves as a general guideline for future debris removal consideration.

Modeling, Simulation, and Control of a Solar Electric Propulsion Vehicle in Near-Earth Vicinity Including Solar Array Degradation

NASA Technical Reports Server (NTRS)

Witzberger, Kevin (Inventor); Hojnicki, Jeffery (Inventor); Manzella, David (Inventor)

2016-01-01

Modeling and control software that integrates the complexities of solar array models, a space environment, and an electric propulsion system into a rigid body vehicle simulation and control model is provided. A rigid body vehicle simulation of a solar electric propulsion (SEP) vehicle may be created using at least one solar array model, at least one model of a space environment, and at least one model of a SEP propulsion system. Power availability and thrust profiles may be determined based on the rigid body vehicle simulation as the SEP vehicle transitions from a low Earth orbit (LEO) to a higher orbit or trajectory. The power availability and thrust profiles may be displayed such that a user can use the displayed power availability and thrust profiles to determine design parameters for an SEP vehicle mission.

Hypersonic Navier Stokes Comparisons to Orbiter Flight Data

NASA Technical Reports Server (NTRS)

Campbell, Charles H.; Nompelis, Ioannis; Candler, Graham; Barnhart, Michael; Yoon, Seokkwan

2009-01-01

Hypersonic chemical nonequilibrium simulations of low earth orbit entry flow fields are becoming increasingly commonplace as software and computational capabilities become more capable. However, development of robust and accurate software to model these environments will always encounter a significant barrier in developing a suite of high quality calibration cases. The US3D hypersonic nonequilibrium Navier Stokes analysis capability has been favorably compared to a number of wind tunnel test cases. Extension of the calibration basis for this software to Orbiter flight conditions will provide an incremental increase in confidence. As part of the Orbiter Boundary Layer Transition Flight Experiment and the Hypersonic Thermodynamic Infrared Measurements project, NASA is performing entry flight testing on the Orbiter to provide valuable aerothermodynamic heating data. An increase in interest related to orbiter entry environments is resulting from this activity. With the advent of this new data, comparisons of the US3D software to the new flight testing data is warranted. This paper will provide information regarding the framework of analyses that will be applied with the US3D analysis tool. In addition, comparisons will be made to entry flight testing data provided by the Orbiter BLT Flight Experiment and HYTHIRM projects. If data from digital scans of the Orbiter windward surface become available, simulations will also be performed to characterize the difference in surface heating between the CAD reference OML and the digitized surface provided by the surface scans.

Orbiter entry aerothermodynamics

NASA Technical Reports Server (NTRS)

Ried, R. C.

1985-01-01

The challenge in the definition of the entry aerothermodynamic environment arising from the challenge of a reliable and reusable Orbiter is reviewed in light of the existing technology. Select problems pertinent to the orbiter development are discussed with reference to comprehensive treatments. These problems include boundary layer transition, leeward-side heating, shock/shock interaction scaling, tile gap heating, and nonequilibrium effects such as surface catalysis. Sample measurements obtained from test flights of the Orbiter are presented with comparison to preflight expectations. Numerical and wind tunnel simulations gave efficient information for defining the entry environment and an adequate level of preflight confidence. The high quality flight data provide an opportunity to refine the operational capability of the orbiter and serve as a benchmark both for the development of aerothermodynamic technology and for use in meeting future entry heating challenges.

Arcing in Leo and Geo Simulated Environments: Comparative Analysis

NASA Technical Reports Server (NTRS)

Vayner, Boris V.; Ferguson, Dale C.; Galofaro, Joel TY.

2006-01-01

Comprehensive tests of two solar array samples in simulated Low Earth Orbit (LEO) and Geosynchronous Orbit (GEO) environments have demonstrated that the arc inception voltage was 2-3 times lower in the LEO plasma than in the GEO vacuum. Arc current pulse wave forms are also essentially different in these environments. Moreover, the wide variations of pulse forms do not allow introducing the definition of a "standard arc wave form" even in GEO conditions. Visual inspection of the samples after testing in a GEO environment revealed considerable damage on coverglass surfaces and interconnects. These harmful consequences can be explained by the discharge energy being one order of magnitude higher in vacuum than in background plasma. The tests also revealed a potential danger of powerful electrostatic discharges that could be initiated on the solar array surface of a satellite in GEO during the ignition of an arcjet thruster.

Subsatellite Orbital Analysis Program (SOAP) user's guide

NASA Astrophysics Data System (ADS)

Castle, K. G.; Voss, J. M.; Gibson, J. S.

1981-07-01

The features and use of the subsatellite operational analysis are examined. The model simulates several Earth-orbiting vehicles, their pilots, control systems, and interaction with the environment. The use of the program, input and output capabilities, executive structures, and properties of the vehicles and environmental effects which it models are described.

Subsatellite Orbital Analysis Program (SOAP) user's guide

NASA Technical Reports Server (NTRS)

Castle, K. G.; Voss, J. M.; Gibson, J. S.

1981-01-01

The features and use of the subsatellite operational analysis are examined. The model simulates several Earth-orbiting vehicles, their pilots, control systems, and interaction with the environment. The use of the program, input and output capabilities, executive structures, and properties of the vehicles and environmental effects which it models are described.

Simulation of charge transfer and orbital rehybridization in molecular and condensed matter systems

NASA Astrophysics Data System (ADS)

Nistor, Razvan A.

The mixing and shifting of electronic orbitals in molecules, or between atoms in bulk systems, is crucially important to the overall structure and physical properties of materials. Understanding and accurately modeling these orbital interactions is of both scientific and industrial relevance. Electronic orbitals can be perturbed in several ways. Doping, adding or removing electrons from systems, can change the bond-order and the physical properties of certain materials. Orbital rehybridization, driven by either thermal or pressure excitation, alters the short-range structure of materials and changes their long-range transport properties. Macroscopically, during bond formation, the shifting of electronic orbitals can be interpreted as a charge transfer phenomenon, as electron density may pile up around, and hence, alter the effective charge of, a given atom in the changing chemical environment. Several levels of theory exist to elucidate the mechanisms behind these orbital interactions. Electronic structure calculations solve the time-independent Schrodinger equation to high chemical accuracy, but are computationally expensive and limited to small system sizes and simulation times. Less fundamental atomistic calculations use simpler parameterized functional expressions called force-fields to model atomic interactions. Atomistic simulations can describe systems and time-scales larger and longer than electronic-structure methods, but at the cost of chemical accuracy. In this thesis, both first-principles and phenomenological methods are addressed in the study of several encompassing problems dealing with charge transfer and orbital rehybridization. Firstly, a new charge-equilibration method is developed that improves upon existing models to allow next-generation force-fields to describe the electrostatics of changing chemical environments. Secondly, electronic structure calculations are used to investigate the doping dependent energy landscapes of several high-temperature superconducting materials in order to parameterize the apparently large nonlinear electron-phonon coupling. Thirdly, ab initio simulations are used to investigate the role of pressure-driven structural re-organization in the crystalline-to-amorphous (or, metallic-to-insulating) transition of a common binary phase-change material composed of Ge and Sb. Practical applications of each topic will be discussed. Keywords. Charge-equilibration methods, molecular dynamics, electronic structure calculations, ab initio simulations, high-temperature superconductors, phase-change materials.

Results of an investigation of jet plume effects on an 0.010-scale model (75-OTS) of the space shuttle integrated vehicle in the 9 x 7-foot leg of the NASA/Ames unitary wind tunnel (IA82B), volume 1. [an exhaust flow simulation

NASA Technical Reports Server (NTRS)

Hawthorne, P. J.

1976-01-01

The base pressure environment was investigated for the first and second stage mated vehicle in a supersonic flow field from Mach 1.55 through 2.20 with simulated rocket engine exhaust plumes. The pressure environment was investigated for the orbiter at various vent port locations at these same freestream conditions. The Mach number environment around the base of the model with rocket plumes simulated was examined. Data were obtained at angles of attack from -4 deg through +4 deg at zero yaw, and at yaw angles from -4 deg through +4 deg at zero angle of attack, with rocket plume sizes varying from smaller than nominal to much greater than nominal. Failed orbiter engine data were also obtained. Elevon hinge moments and wing panel load data were obtained during all runs. Photographs of the tested configurations are shown.

Measuring Small Debris - What You Can't See Can Hurt You

NASA Technical Reports Server (NTRS)

Matney, Mark

2016-01-01

While modeling gives us a tool to better understand the Earth orbit debris environment, it is measurements that give us "ground truth" about what is happening in space. Assets that can detect orbital debris remotely from the surface of the Earth, such as radars and telescopes, give us a statistical view of how debris are distributed in space, how they are being created, and how they are evolving over time. In addition, in situ detectors in space are giving us a better picture of how the small particle environment is actually damaging spacecraft today. IN addition, simulation experiments on the ground help us to understand what we are seeing in orbit. This talk will summarize the history of space debris measurements, how it has changed our view of the Earth orbit environment, and how we are designing the experiments of tomorrow.

Determination of ASPS performance for large payloads in the shuttle orbiter disturbance environment. [digital simulation

NASA Technical Reports Server (NTRS)

Keckler, C. R.; Kibler, K. S.; Powell, L. F.

1979-01-01

A high fidelity simulation of the annular suspension and pointing system (ASPS), its payload, and the shuttle orbiter was used to define the worst case orientations of the ASPS and its payload for the various vehicle disturbances, and to determine the performance capability of the ASPS under these conditions. The most demanding and largest proposed payload, the Solar Optical Telescope was selected for study. It was found that, in all cases, the ASPS more than satisfied the payload's requirements. It is concluded that, to satisfy facility class payload requirements, the ASPS or a shuttle orbiter free-drift mode (control system off) should be utilized.

Characterization of Space Environmental Effects on Candidate Solar Sail Material

NASA Technical Reports Server (NTRS)

Edwards, David; Hubbs, Whitney; Stanaland, Tesia; Munafo, Paul M. (Technical Monitor)

2002-01-01

The National Aeronautics and Space Administration's (NASA) Marshall Space Flight Center (MSFC) is concentrating research into the utilization of photonic materials for spacecraft propulsion. Spacecraft propulsion, using photonic materials, will be achieved using a solar sail. A solar sail operates on the principle that photons, originating from the sun, impart pressure to the sail and therefore provide a source for spacecraft propulsion. The pressure imparted to a solar sail can be increased, up to a factor of two if the sunfacing surface is perfectly reflective. Therefore, these solar sails are generally composed of a highly reflective metallic sun-facing layer, a thin polymeric substrate and occasionally a highly emissive back surface. The Space Environmental Effects Team, at MSFC, is actively characterizing candidate solar sail material to evaluate the thermo-optical and mechanical properties after exposure to radiation environments simulating orbital environments. This paper describes the results of three candidate materials after exposure to a simulated Geosynchronous Transfer Orbit (GTO). This is the first known characterization of solar sail material exposed to space simulated radiation environments. The technique of radiation dose versus material depth profiling was used to determine the orbital equivalent exposure doses. The solar sail exposure procedures and results of the material characterization will be discussed.

A radiant heating test facility for space shuttle orbiter thermal protection system certification

NASA Technical Reports Server (NTRS)

Sherborne, W. D.; Milhoan, J. D.

1980-01-01

A large scale radiant heating test facility was constructed so that thermal certification tests can be performed on the new generation of thermal protection systems developed for the space shuttle orbiter. This facility simulates surface thermal gradients, onorbit cold-soak temperatures down to 200 K, entry heating temperatures to 1710 K in an oxidizing environment, and the dynamic entry pressure environment. The capabilities of the facility and the development of new test equipment are presented.

Constrained Local UniversE Simulations: a Local Group factory

NASA Astrophysics Data System (ADS)

Carlesi, Edoardo; Sorce, Jenny G.; Hoffman, Yehuda; Gottlöber, Stefan; Yepes, Gustavo; Libeskind, Noam I.; Pilipenko, Sergey V.; Knebe, Alexander; Courtois, Hélène; Tully, R. Brent; Steinmetz, Matthias

2016-05-01

Near-field cosmology is practised by studying the Local Group (LG) and its neighbourhood. This paper describes a framework for simulating the `near field' on the computer. Assuming the Λ cold dark matter (ΛCDM) model as a prior and applying the Bayesian tools of the Wiener filter and constrained realizations of Gaussian fields to the Cosmicflows-2 (CF2) survey of peculiar velocities, constrained simulations of our cosmic environment are performed. The aim of these simulations is to reproduce the LG and its local environment. Our main result is that the LG is likely a robust outcome of the ΛCDMscenario when subjected to the constraint derived from CF2 data, emerging in an environment akin to the observed one. Three levels of criteria are used to define the simulated LGs. At the base level, pairs of haloes must obey specific isolation, mass and separation criteria. At the second level, the orbital angular momentum and energy are constrained, and on the third one the phase of the orbit is constrained. Out of the 300 constrained simulations, 146 LGs obey the first set of criteria, 51 the second and 6 the third. The robustness of our LG `factory' enables the construction of a large ensemble of simulated LGs. Suitable candidates for high-resolution hydrodynamical simulations of the LG can be drawn from this ensemble, which can be used to perform comprehensive studies of the formation of the LG.

Space simulation test for thermal control materials

NASA Technical Reports Server (NTRS)

Hardgrove, W. R.

1990-01-01

Tests were run in TRW's Combined Environment Facility to examine the degradation of thermal control materials in a simulated space environment. Thermal control materials selected for the test were those presently being used on spacecraft or predicted to be used within the next few years. The geosynchronous orbit environment was selected as the most interesting. One of the goals was to match degradation of those materials with available flight data. Another aim was to determine if degradation can adequately be determined with accelerated or short term ground tests.

KENNEDY SPACE CENTER, FLA. - In the Launch Control Center, officials monitor the “Mode VII” emergency landing simulation being conducted at Kennedy Space Center and managed and directed from the LCC. From left are Dr. Luis Moreno and Dr. David Reed, with Bionetics Life Sciences, and Dr. Philip Scarpa, with the KSC Safety, Occupational Health and Environment Division. The purpose of the Mode VII is to exercise emergency preparedness personnel, equipment and facilities in rescuing astronauts from a downed orbiter and providing immediate medical attention. This simulation presents an orbiter that has crashed short of the Shuttle Landing Facility in a wooded area 2-1/2 miles south of Runway 33. Emergency crews are responding to the volunteer “astronauts” who are simulating various injuries inside the crew compartment mock-up. Rescuers must remove the crew, provide triage and transport to hospitals those who need further treatment. Local hospitals are participating in the exercise.

NASA Image and Video Library

2004-02-18

KENNEDY SPACE CENTER, FLA. - In the Launch Control Center, officials monitor the “Mode VII” emergency landing simulation being conducted at Kennedy Space Center and managed and directed from the LCC. From left are Dr. Luis Moreno and Dr. David Reed, with Bionetics Life Sciences, and Dr. Philip Scarpa, with the KSC Safety, Occupational Health and Environment Division. The purpose of the Mode VII is to exercise emergency preparedness personnel, equipment and facilities in rescuing astronauts from a downed orbiter and providing immediate medical attention. This simulation presents an orbiter that has crashed short of the Shuttle Landing Facility in a wooded area 2-1/2 miles south of Runway 33. Emergency crews are responding to the volunteer “astronauts” who are simulating various injuries inside the crew compartment mock-up. Rescuers must remove the crew, provide triage and transport to hospitals those who need further treatment. Local hospitals are participating in the exercise.

LightForce: An Update on Orbital Collision Avoidance Using Photon Pressure

NASA Technical Reports Server (NTRS)

Stupl, Jan; Mason, James; De Vries, Willem; Smith, Craig; Levit, Creon; Marshall, William; Salas, Alberto Guillen; Pertica, Alexander; Olivier, Scot; Ting, Wang

2012-01-01

We present an update on our research on collision avoidance using photon-pressure induced by ground-based lasers. In the past, we have shown the general feasibility of employing small orbit perturbations, induced by photon pressure from ground-based laser illumination, for collision avoidance in space. Possible applications would be protecting space assets from impacts with debris and stabilizing the orbital debris environment. Focusing on collision avoidance rather than de-orbit, the scheme avoids some of the security and liability implications of active debris removal, and requires less sophisticated hardware than laser ablation. In earlier research we concluded that one ground based system consisting of a 10 kW class laser, directed by a 1.5 m telescope with adaptive optics, could avoid a significant fraction of debris-debris collisions in low Earth orbit. This paper describes our recent efforts, which include refining our original analysis, employing higher fidelity simulations and performing experimental tracking tests. We investigate the efficacy of one or more laser ground stations for debris-debris collision avoidance and satellite protection using simulations to investigate multiple case studies. The approach includes modeling of laser beam propagation through the atmosphere, the debris environment (including actual trajectories and physical parameters), laser facility operations, and simulations of the resulting photon pressure. We also present the results of experimental laser debris tracking tests. These tests track potential targets of a first technical demonstration and quantify the achievable tracking performance.

Analysis of the charging of the SCATHA (P78-2) satellite

NASA Technical Reports Server (NTRS)

Stannard, P. R.; Katz, I.; Mandell, M. J.; Cassidy, J. J.; Parks, D. E.; Rotenberg, M.; Steen, P. G.

1980-01-01

The charging of a large object in polar Earth orbit was investigated in order to obtain a preliminary indication of the response of the shuttle orbiter to such an environment. Two NASCAP (NASA Charging Analyzer Program) models of SCATHA (Satellite Charging at High Altitudes) were used in simulations of charging events. The properties of the satellite's constituent materials were compiled and representations of the experimentally observed plasma spectra were constructed. Actual charging events, as well as those using test environments, were simulated. Numerical models for the simulation of particle emitters and detectors were used to analyze the operation of these devices onboard SCATHA. The effect of highly charged surface regions on the charging conductivity within a photosheath was used to interpret results from the onboard electric field experiment. Shadowing calculations were carried out for the satellite and a table of effective illuminated areas was compiled.

The influence of solid rocket motor retro-burns on the space debris environment

NASA Astrophysics Data System (ADS)

Stabroth, Sebastian; Homeister, Maren; Oswald, Michael; Wiedemann, Carsten; Klinkrad, Heiner; Vörsmann, Peter

The ESA space debris population model MASTER (Meteoroid and Space Debris Terrestrial Environment Reference) considers firings of solid rocket motors (SRM) as a debris source with the associated generation of slag and dust particles. The resulting slag and dust population is a major contribution to the sub-millimetre size debris environment in Earth orbit. The current model version, MASTER-2005, is based on the simulation of 1076 orbital SRM firings which contributed to the long-term debris environment. A comparison of the modelled flux with impact data from returned surfaces shows that the shape and quantity of the modelled SRM dust distribution matches that of recent Hubble Space Telescope (HST) solar array measurements very well. However, the absolute flux level for dust is under-predicted for some of the analysed Long Duration Exposure Facility (LDEF) surfaces. This points into the direction of some past SRM firings not included in the current event database. The most suitable candidates for these firings are the large number of SRM retro-burns of return capsules. Objects released by those firings have highly eccentric orbits with perigees in the lower regions of the atmosphere. Thus, they produce no long-term effect on the debris environment. However, a large number of those firings during the on-orbit time frame of LDEF might lead to an increase of the dust population for some of the LDEF surfaces. In this paper, the influence of SRM retro-burns on the short- and long-term debris environment is analysed. The existing firing database is updated with gathered information of some 800 Russian retro-firings. Each firing is simulated with the MASTER population generation module. The resulting population is compared against the existing background population of SRM slag and dust particles in terms of spatial density and flux predictions.

Flight Experiment Demonstration System (FEDS): Mathematical specification

NASA Technical Reports Server (NTRS)

Shank, D. E.

1984-01-01

Computational models for the flight experiment demonstration system (FEDS) code 580 were developed. The FEDS is a modification of the automated orbit determination system which was developed during 1981 and 1982. The purpose of FEDS is to demonstrate, in a simulated spacecraft environment, the feasibility of using microprocessors to perform onboard orbit determination with limited ground support.

NASA's Marshall Space Flight Center Recent Studies and Technology Developments in the Area of SSA/Orbital Debris

NASA Technical Reports Server (NTRS)

Wiegmann, Bruce M.; Hovater, Mary; Kos, Larry

2012-01-01

NASA/MSFC has been investigating the various aspects of the growing orbital debris problem since early 2009. Data shows that debris ranging in size from 5 mm to 10 cm presents the greatest threat to operational spacecraft today. Therefore, MSFC has focused its efforts on small orbital debris. Using off-the-shelf analysis packages, like the ESA MASTER software, analysts at MSFC have begun to characterize the small debris environment in LEO to support several spacecraft concept studies and hardware test programs addressing the characterization, mitigation, and ultimate removal, if necessary, of small debris. The Small Orbital Debris Active Removal (SODAR) architectural study investigated the overall effectiveness of removing small orbital debris from LEO using a low power, space-based laser. The Small Orbital Debris Detection, Acquisition, and Tracking (SODDAT) conceptual technology demonstration spacecraft was developed to address the challenges of in-situ small orbital debris environment classification including debris observability and instrument requirements for small debris observation. Work is underway at MSFC in the areas of hardware and testing. By combining off the shelf digital video technology, telescope lenses, and advanced video image FPGA processing, MSFC is building a breadboard of a space based, passive orbital tracking camera that can detect and track faint objects (including small debris, satellites, rocket bodies, and NEOs) at ranges of tens to hundreds of kilometers and speeds in excess of 15 km/sec,. MSFC is also sponsoring the development of a one-of-a-kind Dynamic Star Field Simulator with a high resolution large monochrome display and a custom collimator capable of projecting realistic star images with simple orbital debris spots (down to star magnitude 11-12) into a passive orbital detection and tracking system with simulated real-time angular motions of the vehicle mounted sensor. The dynamic star field simulator can be expanded for multiple sensors (including advanced star trackers), real-time vehicle pointing inputs, and more complex orbital debris images. This system is also adaptable to other sensor optics, missions, and installed sensor testing.

Predicting Material Performance in the Space Environment from Laboratory Test Data, Static Design Environments, and Space Weather Models

NASA Technical Reports Server (NTRS)

Minow, Josep I.; Edwards, David L.

2008-01-01

Qualifying materials for use in the space environment is typically accomplished with laboratory exposures to simulated UV/EUV, atomic oxygen, and charged particle radiation environments with in-situ or subsequent measurements of material properties of interest to the particular application. Choice of environment exposure levels are derived from static design environments intended to represent either mean or extreme conditions that are anticipated to be encountered during a mission. The real space environment however is quite variable. Predictions of the on orbit performance of a material qualified to laboratory environments can be done using information on 'space weather' variations in the real environment. This presentation will first review the variability of space environments of concern for material degradation and then demonstrate techniques for using test data to predict material performance in a variety of space environments from low Earth orbit to interplanetary space using historical measurements and space weather models.

Effects of CubeSat Deployments in Low-Earth Orbit

NASA Technical Reports Server (NTRS)

Matney, M. J.; Vavrin, A. B.; Manis, A. P.

2017-01-01

Long-term models, such as NASA's LEGEND (LEO (Low-Earth Orbit)-to-GEO (Geosynchrous Earth Orbit) Environment Debris) model, are used to make predictions about how space activities will affect the long-term evolution of the debris environment. Part of this process is to predict how spacecraft and rocket bodies will be launched and left in the environment in the future. This has usually been accomplished by repeating past launch history to simulate future launches. It was partially upon the basis of the results of such models that both national and international orbital debris mitigation guidelines - especially the "25-year rule" for post-mission disposal - were determined. The proliferation of Cubesat launches in recent years, however, has raised concerns that we are seeing a fundamental shift in how humans launch satellites into space that may alter the assumptions upon which our current mitigation guidelines are based. The large number of Cubesats, and their short lifetime and general inability to perform collision avoidance, potentially makes them an important new source of debris. The NASA Orbital Debris Program Office (ODPO) has conducted a series of LEGEND computations to investigate the long-term effects of adding Cubesats to the environment. Several possible future scenarios were simulated to investigate the effects of the size of future Cubesat launches and the efficiency of post-mission disposal on the proliferation of catastrophic collisions over the next 200 years. These results are compared to a baseline "business-as-usual" scenario where launches are assumed to continue as in the past without major Cubesat deployments. Using these results, we make observations about the continued use of the 25-year rule and the importance of the universal application of post-mission disposal. We also discuss how the proliferation of Cubesats may affect satellite traffic at lower altitudes.

Effects on Training Using Illumination in Virtual Environments

NASA Technical Reports Server (NTRS)

Maida, James C.; Novak, M. S. Jennifer; Mueller, Kristian

1999-01-01

Camera based tasks are commonly performed during orbital operations, and orbital lighting conditions, such as high contrast shadowing and glare, are a factor in performance. Computer based training using virtual environments is a common tool used to make and keep CTW members proficient. If computer based training included some of these harsh lighting conditions, would the crew increase their proficiency? The project goal was to determine whether computer based training increases proficiency if one trains for a camera based task using computer generated virtual environments with enhanced lighting conditions such as shadows and glare rather than color shaded computer images normally used in simulators. Previous experiments were conducted using a two degree of freedom docking system. Test subjects had to align a boresight camera using a hand controller with one axis of rotation and one axis of rotation. Two sets of subjects were trained on two computer simulations using computer generated virtual environments, one with lighting, and one without. Results revealed that when subjects were constrained by time and accuracy, those who trained with simulated lighting conditions performed significantly better than those who did not. To reinforce these results for speed and accuracy, the task complexity was increased.

Atomic oxygen effects on materials

NASA Technical Reports Server (NTRS)

Banks, Bruce A.; Rutledge, Sharon K.; Brady, Joyce A.; Merrow, James E.

1989-01-01

Understanding of the basic processes of atomic oxygen interaction is currently at a very elementary level. However, measurement of erosion yields, surface morphology, and optical properties for low fluences have brought about much progress in the past decade. Understanding the mechanisms and those factors that are important for proper simulation of low Earth orbit is at a much lower level of understanding. The ability to use laboratory simulations with confidence to quantifiably address the functional performance and durability of materials in low Earth orbit will be necessary to assure long-term survivability to the natural space environment.

Astronaut Russell Schweickart inside simulator for EVA training

NASA Image and Video Library

1968-12-11

S68-55391 (11 Dec. 1968) --- Astronaut Russell L. Schweickart, lunar module pilot of the Apollo 9 (Spacecraft 104/Lunar Module 3/Saturn 504) space mission, is seen inside Chamber "A," Space Environment Simulation Laboratory, Building 32, participating in dry run activity in preparation for extravehicular activity which is scheduled in Chamber "A." The purpose of the scheduled training is to familiarize the crewmen with the operation of EVA equipment in a simulated space environment. In addition, metabolic and workload profiles will be simulated on each crewman. Astronauts Schweickart and Alan L. Bean, backup lunar module pilot, are scheduled to receive thermal-vacuum training simulating Earth-orbital EVA.

Skylab fluid mechanics simulations: Oscillation, rotation, collision and coalescence of water droplets under low-gravity environment

NASA Technical Reports Server (NTRS)

Vaughan, O. H., Jr.; Hung, R. J.

1975-01-01

Skylab 4 crew members performed a series of demonstrations showing the oscillations, rotations, as well as collision coalescence of water droplets which simulate various physical models of fluids under low gravity environment. The results from Skylab demonstrations provide information and illustrate the potential of an orbiting space-oriented research laboratory for the study of more sophisticated fluid mechanic experiments. Experiments and results are discussed.

Low-speed longitudinal orbiter qualities

NASA Technical Reports Server (NTRS)

Powers, B. G.

1985-01-01

The shuttle program took on the challenge of providing a manual landing capability for an operational vehicle returning from orbit. Some complex challenges were encountered in developing the longitudinal flying qualities required to land the orbiter manually in an operational environment. Approach and landing test flights indicated a tendency for pilot-induced oscillation near landing. Changes in the operational procedures reduced the difficulty of the landing task, and an adaptive stick filter was incorporated to reduce the severity of any pilot-induced oscillatory motions. Fixed-base, movingbase, and in-flight simulations were used for the evaluations, and in general, flight simulation was the only reliable means of assessing the low-speed longitudinal flying qualities problems. Overall, the orbiter control system and operational procedures have produced a good capability to routinely perform precise landings with a large, unpowered vehicle with a low lift-to-drag ratio.

ARTEMIS: Ares Real Time Environments for Modeling, Integration, and Simulation

NASA Technical Reports Server (NTRS)

Hughes, Ryan; Walker, David

2009-01-01

This slide presentation reviews the use of ARTEMIS in the development and testing of the ARES launch vehicles. Ares Real Time Environment for Modeling, Simulation and Integration (ARTEMIS) is the real time simulation supporting Ares I hardware-in-the-loop (HWIL) testing. ARTEMIS accurately models all Ares/Orion/Ground subsystems which interact with Ares avionics components from pre-launch through orbit insertion The ARTEMIS System integration Lab, and the STIF architecture is reviewed. The functional components of ARTEMIS are outlined. An overview of the models and a block diagram is presented.

A Process for Comparing Dynamics of Distributed Space Systems Simulations

NASA Technical Reports Server (NTRS)

Cures, Edwin Z.; Jackson, Albert A.; Morris, Jeffery C.

2009-01-01

The paper describes a process that was developed for comparing the primary orbital dynamics behavior between space systems distributed simulations. This process is used to characterize and understand the fundamental fidelities and compatibilities of the modeling of orbital dynamics between spacecraft simulations. This is required for high-latency distributed simulations such as NASA s Integrated Mission Simulation and must be understood when reporting results from simulation executions. This paper presents 10 principal comparison tests along with their rationale and examples of the results. The Integrated Mission Simulation (IMSim) (formerly know as the Distributed Space Exploration Simulation (DSES)) is a NASA research and development project focusing on the technologies and processes that are related to the collaborative simulation of complex space systems involved in the exploration of our solar system. Currently, the NASA centers that are actively participating in the IMSim project are the Ames Research Center, the Jet Propulsion Laboratory (JPL), the Johnson Space Center (JSC), the Kennedy Space Center, the Langley Research Center and the Marshall Space Flight Center. In concept, each center participating in IMSim has its own set of simulation models and environment(s). These simulation tools are used to build the various simulation products that are used for scientific investigation, engineering analysis, system design, training, planning, operations and more. Working individually, these production simulations provide important data to various NASA projects.

Lunar and Planetary Science XXXV: Education

NASA Technical Reports Server (NTRS)

2004-01-01

The session "Education" includes the following topics: 1) Convection, Magnetism, Orbital Resonances, Impacts, and Volcanism: Energies and Processes in the Solar System: Didactic Activities; 2) Knowledge Management in Aerospace-Education and Training Issues; 3) Creating Easy-to-Understand Planetary Maps; 4) Planetary Environment comparison in the Education of Astrobiology; and 5) Design and Construction of a Mechanism for the Orbital Resonances Simulation.

Preliminary Experimental Results for Charge Drag in a Simulated Low Earth Orbit Environment

NASA Astrophysics Data System (ADS)

Azema-Rovira, Monica

Interest in the Low Earth Orbit (LEO) environment is growing in the science community as well as in the private sector. The number of spacecraft launched in these altitudes (150 - 700 km) keeps growing, and this region is accumulating space debris. In this scenario, the precise location of all LEO objects is a key factor to avoid catastrophic collisions and to safely perform station-keeping maneuvers. The detailed study of the atmospheric models in LEO can enhance the disturbances forces calculation of an orbiting object. Recent numerical studies indicate that one of the biggest non-conservative forces on a spacecraft is underestimated, the charge drag phenomenon. Validating these numerical models experimentally, will help to improve the numerical models for future spacecraft mission design. For this reason, the motivation of this thesis is to characterize a plasma source to later be used for charged drag measurements. The characterization has been done at the University of Colorado Colorado Springs in the Chamber for Atmospheric and Orbital Space Simulation. In the characterization process, a nano-Newton Thrust Stand has been characterized as a plasma diagnosis tool and compared with Langmuir Probe data.

Testing and evaluation for astronaut extravehicular activity (EVA) operability.

PubMed

Shields, N; King, L C

1998-09-01

Because it is the human component that defines space mission success, careful planning is required to ensure that hardware can be operated and maintained by crews on-orbit. Several methods exist to allow researchers and designers to better predict how hardware designs will behave under the harsh environment of low Earth orbit, and whether designs incorporate the necessary features for Extra Vehicular Activity (EVA) operability. Testing under conditions of simulated microgravity can occur during the design concept phase when verifying design operability, during mission training, or concurrently with on-orbit mission operations. The bulk of testing is focused on normal operations, but also includes evaluation of credible mission contingencies or "what would happen if" planning. The astronauts and cosmonauts who fly these space missions are well prepared and trained to survive and be productive in Earth's orbit. The engineers, designers, and training crews involved in space missions subject themselves to Earth based simulation techniques that also expose them to extreme environments. Aircraft falling ten thousand feet, alternating g-loads, underwater testing at 45 foot depth, enclosure in a vacuum chamber and subject to thermal extremes, each carries with it inherent risks to the humans preparing for space missions.

Java-based Graphical User Interface for MAVERIC-II

NASA Technical Reports Server (NTRS)

Seo, Suk Jai

2005-01-01

A computer program entitled "Marshall Aerospace Vehicle Representation in C II, (MAVERIC-II)" is a vehicle flight simulation program written primarily in the C programming language. It is written by James W. McCarter at NASA/Marshall Space Flight Center. The goal of the MAVERIC-II development effort is to provide a simulation tool that facilitates the rapid development of high-fidelity flight simulations for launch, orbital, and reentry vehicles of any user-defined configuration for all phases of flight. MAVERIC-II has been found invaluable in performing flight simulations for various Space Transportation Systems. The flexibility provided by MAVERIC-II has allowed several different launch vehicles, including the Saturn V, a Space Launch Initiative Two-Stage-to-Orbit concept and a Shuttle-derived launch vehicle, to be simulated during ascent and portions of on-orbit flight in an extremely efficient manner. It was found that MAVERIC-II provided the high fidelity vehicle and flight environment models as well as the program modularity to allow efficient integration, modification and testing of advanced guidance and control algorithms. In addition to serving as an analysis tool for techno logy development, many researchers have found MAVERIC-II to be an efficient, powerful analysis tool that evaluates guidance, navigation, and control designs, vehicle robustness, and requirements. MAVERIC-II is currently designed to execute in a UNIX environment. The input to the program is composed of three segments: 1) the vehicle models such as propulsion, aerodynamics, and guidance, navigation, and control 2) the environment models such as atmosphere and gravity, and 3) a simulation framework which is responsible for executing the vehicle and environment models and propagating the vehicle s states forward in time and handling user input/output. MAVERIC users prepare data files for the above models and run the simulation program. They can see the output on screen and/or store in files and examine the output data later. Users can also view the output stored in output files by calling a plotting program such as gnuplot. A typical scenario of the use of MAVERIC consists of three-steps; editing existing input data files, running MAVERIC, and plotting output results.

Integrated Simulation Design Challenges to Support TPS Repair Operations

NASA Technical Reports Server (NTRS)

Quiocho, Leslie J.; Crues, Edwin Z.; Huynh, An; Nguyen, Hung T.; MacLean, John

2006-01-01

During the Orbiter Repair Maneuver (OM) operations planned for Return to Flight (RTF), the Shuttle Remote Manipulator System (SRMS) must grapple the International Space Station (ISS), undock the Orbiter, maneuver it through a long duration trajectory, and orient it to an EVA crewman poised at the end of the Space Station Remote Manipulator System (SSRMS) to facilitate the repair of the Thermal Protection System (TPS). Once repair has been completed and confirmed, then the SRMS proceeds back through the trajectory to dock the Orbiter to the Orbiter Docking System. In order to support analysis of the complex dynamic interactions of the integrated system formed by the Orbiter, ISS, SRMS, and SSMS during the ORM, simulation tools used for previous nominal mission support required substantial enhancements. These upgrades were necessary to provide analysts with the capabilities needed to study integrated system performance. Prevalent throughout this ORM operation is a dynamically varying topology. In other words, the ORM starts with the SRMS grappled to the mated Shuttle/ISS stack (closed loop topology), moves to an open loop chain topology consisting of the Shuttle, SRMS, and ISS, and then, at the repair configuration, extends the chain topology to one consisting of the Shuttle, SMS, ISS, and SSRMS/EVA crewman. The resulting long dynamic chain of vehicles and manipulators may exhibit significant motion between the Shuttle worksite and the EVA crewman due to the system flexibility throughout the topology (particularly within the SRMS/SSRMS joints and links). Since the attachment points of both manipulators span the flexible structure of the ISS, simulation analysis may also need to take that into consideration. Moreover, due to the lengthy time duration associated with the maneuver and repair, orbital effects become a factor and require the ISS vehicle control system to maintain active attitude control. Several facets of the ORM operation make the associated analytical efforts different from previous mission support, including: (1) the magnitude of the SRMS handled payload (Le., Orbiter class), (2) the orbital effects induced on the integrated system consisting of the large Shuttle and ISS masses connected by a light flexible SRMS, (3) long duration environmental consequences due to the lengthy operational times associated with the maneuver and repair of the TPS, (4) active attitude control (as opposed to free drift) interacting with the SRMS and SSRMS manipulators (also due to the length of the maneuver and repair), (5) relative dynamics between the EVA crewman and thc worksite influenced by the extended flexible topology. In order to meet these analysis challenges, an O Msi mulation architecture was developed leveraging upon numerous pre-existing simulation elements to analyze the various subsystems individually. For example, core manipulator subsystem simulations for both the SRMS and SSRMS were originally combined to provide the dual-arm dynamics topology simulation (in the absence of orbital dynamics and vehicle control). This capability was later merged with the simulation used to analyze SRMS loading with a heavy payload in the orbital environment with an active payload control system (in this case, the ISS Attitude Control System (ACS)), configured for the ORM. The resulting worksite dynamics simulation, based off of the modified ORM simulation, provided the extended topological chain of vehicles and manipulators, while taking into account the orbital effects of both the Shuttle and ISS (as well as its ACS). Verification and validation (V&V) of these integrated simulations became a challenge in itself. A systematic approach needed to be developed such that integration simulation results could be tested against previous constituent simulations upon which these simulations were built. General V&V categories included: (1) core orbital state propagation, (2), stand-alone SRMS, (3) stand-alone SSRMS, (4) stand-alone ISS ACS, (5)ntegrated Shuttle, SRMS, ISS (with active ACS) in the orbital environment, and (5) dual-arm SRMS/SSRMS dynamics topology. Integrated simulation V&V run suites were created and correlated to verification runs from subsystem simulations, in order to establish the validity of the results. This paper discusses the simulation design challenges encountered while developing simulation capabilities to mirror the ORM operations. The paper also describes the incremental build approach that was utilized, starting with the subsystem simulation elements and integration into increasing more complex simulations until the resulting ORM worksite dynamics simulation had been assembled. Furthermore, the paper presents an overall integrated simulation V&V methodology based upon a subsystem level testing, integrated comparisons, and phased checkout.

Comparison of High-Performance Fiber Materials Properties in Simulated and Actual Space Environments

NASA Technical Reports Server (NTRS)

Finckernor, M. M.

2017-01-01

A variety of high-performance fibers, including Kevlar, Nomex, Vectran, and Spectra, have been tested for durability in the space environment, mostly the low Earth orbital environment. These materials have been tested in yarn, tether/cable, and fabric forms. Some material samples were tested in a simulated space environment, such as the Atomic Oxygen Beam Facility and solar simulators in the laboratory. Other samples were flown on the International Space Station as part of the Materials on International Space Station Experiment. Mass loss due to atomic oxygen erosion and optical property changes due to ultraviolet radiation degradation are given. Tensile test results are also presented, including where moisture loss in a vacuum had an impact on tensile strength.

Material exposure effects in a simulated low-Earth orbit environment

NASA Astrophysics Data System (ADS)

Maldonado, C.; McHarg, G.; Asmolova, O.; Andersen, G.; Rodrigues, S.; Ketsdever, A.

2016-11-01

Spacecraft operating in low-Earth orbit (LEO) are subjected to a number of hazardous environmental constituents that can lead to decreased system performance and reduced operational lifetimes. Due to their thermal, optical, and mechanical properties, polymers are used extensively in space systems; however they are particularly susceptible to material erosion and degradation as a result of exposure to the LEO environment. The focus of this research is to examine the material erosion and mass loss experienced by the Novastrat 500 polyimide due to exposure in a simulated LEO environment. In addition to the polymer samples, chrome, silver and gold specimens will be examined to measure the oxidation rate and act as a control specimen, respectively. A magnetically filtered atomic oxygen plasma source has previously been developed and characterized for the purpose of simulating the low-Earth orbit environment. The plasma source can be operated at a variety of discharge currents and gas flow rates, of which the plasma parameters downstream of the source are dependent. The characteristics of the generated plasma were examined as a function of these operating parameters to optimize the production of O+ ions with energy relevant to LEO applications, where the ram energy of the ions due to the motion of the satellite relative to the LEO plasma is high (e.g. 7800 m/s, which corresponds to approximately 5 eV of kinetic energy for O+ ions). The plasma downstream of the source consists of streaming ions with energy of approximately 5 eV and an ion species fraction that is approximately 90% O+.

A simulation facility for testing Space Station assembly procedures

NASA Technical Reports Server (NTRS)

Hajare, Ankur R.; Wick, Daniel T.; Shehad, Nagy M.

1994-01-01

NASA plans to construct the Space Station Freedom (SSF) in one of the most hazardous environments known to mankind - space. It is of the utmost importance that the procedures to assemble and operate the SSF in orbit are both safe and effective. This paper describes a facility designed to test the integration of the telerobotic systems and to test assembly procedures using a real-world robotic arm grappling space hardware in a simulated microgravity environment.

An overview on Bernese projects in planetary geodesy and deep-space orbit determination

NASA Astrophysics Data System (ADS)

Bertone, S.; Jaeggi, A.; Arnold, D.; Girardin, V.; Hosseini, A.; Desprats, W.; Inamdar, J.

2017-12-01

The Astronomical Institute of the University of Bern (AIUB) is still a rather new player in the field of planetary geodesy and orbit determination using deep-space radio-tracking data. Nevertheless, our latest developments in the in-house Bernese GNSS Software (BSW) and the experience gained with the processing of GRAIL data opened the way to many research and collaboration opportunities. In this presentation, we give an overview on our current projects and advances, as well as on our ongoing collaborations. We will present closed-loop simulations of BepiColombo Mercury Planetary Orbiter (MPO) Doppler and altimetry data, including realistic noise models. We use our newly established simulation environment in the BSW and calibration results of the BepiColombo Laser Altimeter (BELA) performed by the Space Research and Planetary Sciences division of the University of Bern. The ultimate goal of these activities is to test different realistic scenarios of the BELA in-orbit performance to improve the recovery of Mercury geodesy and geophysical parameters. We recently started to work on the combined re-processing of all historical missions to Venus to improve their orbits and hence Venus gravity field using new available data (e.g., new atmospheric models), processing tools and techniques and computational power. We shall present our latest advances in processing Magellan data and towards a rigorous solution for the Venus gravity field, e.g., avoiding a step-wise processing as used by Konopliv et al. (1999). The AIUB is currently involved in the Joint Europa Mission proposal. In this framework we present our results for a realistic orbit and gravity field recovery based on simulated Doppler radio-tracking data from the planned scenario of a three months low altitude polar orbit around Europa. We describe our efforts in adapting our simulation tools to the peculiar environment of the Jovian satellite system. Eventually we briefly present the highlights of our latest results in Moon geodesy, including our latest gravity field and tidal parameters solutions from GRAIL data. A separate presentation will be dedicated to detail our Moon-related activities within this session.

The economics of mitigation and remediation measures - preliminary results

NASA Astrophysics Data System (ADS)

Wiedemann, Carsten; Flegel, Sven Kevin; Vörsmann, Peter; Gelhaus, Johannes; Moeckel, Marek; Braun, Vitali; Kebschull, Christopher; Metz, Manuel

2012-07-01

Today there exists a high spatial density of orbital debris objects at about 800 km altitude. The control of the debris population in this region is important for the long-term evolution of the debris environment. The future debris population is investigated by simulations using the software tool LUCA (Long-Term Orbit Utilization Collision Analysis). It is likely that in the future there will occur more catastrophic collisions. Debris objects generated during such events may again trigger further catastrophic collisions. Current simulations have revealed that the number of debris objects will increase in the future. In a long-term perspective, catastrophic collisions may become the dominating mechanism in generating orbital debris. In this study it is investigated, when the situation will become unstable. To prevent this instability it is necessary to implement mitigation and maybe even remediation measures. It is investigated how these measures affect the future debris environment. It is simulated if the growth of the number of debris objects can be interrupted and how much this may cost. Different mitigation scenarios are considered. Furthermore also one remediation measure, the active removal of high-risk objects, is simulated. Cost drivers for the different measures are identified. It is investigated how selected measures are associated with costs. The goal is to find out which economic benefits may result from mitigation or remediation. First results of a cost benefit analyses are presented.

Thermally Induced Vibrations of the Hubble Space Telescope's Solar Array 3 in a Test Simulated Space Environment

NASA Technical Reports Server (NTRS)

Early, Derrick A.; Haile, William B.; Turczyn, Mark T.; Griffin, Thomas J. (Technical Monitor)

2001-01-01

NASA Goddard Space Flight Center and the European Space Agency (ESA) conducted a disturbance verification test on a flight Solar Array 3 (SA3) for the Hubble Space Telescope using the ESA Large Space Simulator (LSS) in Noordwijk, the Netherlands. The LSS cyclically illuminated the SA3 to simulate orbital temperature changes in a vacuum environment. Data acquisition systems measured signals from force transducers and accelerometers resulting from thermally induced vibrations of the SAI The LSS with its seismic mass boundary provided an excellent background environment for this test. This paper discusses the analysis performed on the measured transient SA3 responses and provides a summary of the results.

Development of a hardware-in-loop attitude control simulator for a CubeSat satellite

NASA Astrophysics Data System (ADS)

Tapsawat, Wittawat; Sangpet, Teerawat; Kuntanapreeda, Suwat

2018-01-01

Attitude control is an important part in satellite on-orbit operation. It greatly affects the performance of satellites. Testing of an attitude determination and control subsystem (ADCS) is very challenging since it might require attitude dynamics and space environment in the orbit. This paper develops a low-cost hardware-in-loop (HIL) simulator for testing an ADCS of a CubeSat satellite. The simulator consists of a numerical simulation part, a hardware part, and a HIL interface hardware unit. The numerical simulation part includes orbital dynamics, attitude dynamics and Earth’s magnetic field. The hardware part is the real ADCS board of the satellite. The simulation part outputs satellite’s angular velocity and geomagnetic field information to the HIL interface hardware. Then, based on this information, the HIL interface hardware generates I2C signals mimicking the signals of the on-board rate-gyros and magnetometers and consequently outputs the signals to the ADCS board. The ADCS board reads the rate-gyro and magnetometer signals, calculates control signals, and drives the attitude actuators which are three magnetic torquers (MTQs). The responses of the MTQs sensed by a separated magnetometer are feedback to the numerical simulation part completing the HIL simulation loop. Experimental studies are conducted to demonstrate the feasibility and effectiveness of the simulator.

Controlling the Growth of Future LEO Debris Populations with Active Debris Removal

NASA Technical Reports Server (NTRS)

Liou, J.-C.; Johnson, N. L.; Hill, N. M.

2008-01-01

Active debris removal (ADR) was suggested as a potential means to remediate the low Earth orbit (LEO) debris environment as early as the 1980s. The reasons ADR has not become practical are due to its technical difficulties and the high cost associated with the approach. However, as the LEO debris populations continue to increase, ADR may be the only option to preserve the near-Earth environment for future generations. An initial study was completed in 2007 to demonstrate that a simple ADR target selection criterion could be developed to reduce the future debris population growth. The present paper summarizes a comprehensive study based on more realistic simulation scenarios, including fragments generated from the 2007 Fengyun-1C event, mitigation measures, and other target selection options. The simulations were based on the NASA long-term orbital debris projection model, LEGEND. A scenario, where at the end of mission lifetimes, spacecraft and upper stages were moved to 25-year decay orbits, was adopted as the baseline environment for comparison. Different annual removal rates and different ADR target selection criteria were tested, and the resulting 200-year future environment projections were compared with the baseline scenario. Results of this parametric study indicate that (1) an effective removal strategy can be developed based on the mass and collision probability of each object as the selection criterion, and (2) the LEO environment can be stabilized in the next 200 years with an ADR removal rate of five objects per year.

Feasibility Study of Laboratory Simulation of Single-Stage-to-Orbit Vehicle Base Heating

NASA Technical Reports Server (NTRS)

Park, Chung Sik; Sharma, Surendra; Edwards, Thomas A. (Technical Monitor)

1995-01-01

The feasibility of simulating in a laboratory the heating environment of the base region of the proposed reusable single-stage-to-orbit vehicle during its ascent is examined. The propellant is assumed to consist of hydrocarbon (RP1), liquid hydrogen (LH2), and liquid oxygen (LO2), which produces CO and H2 as the main combustible components of the exhaust effluent. Since afterburning in the recirculating region can dictate the temperature of the base flowfield and ensuing heating phenomena, laboratory simulation focuses on the thermochemistry of the afterburning. By extrapolating the Saturn V flight data, the Damkohler number, in the base region with afterburning for SSTO vehicle, is estimated to be between 30 and 140. It is shown that a flow with a Damkohler number of 1.8 to 25 can be produced in an impulse ground test facility. Even with such a reduced Damkohler number, the experiment can adequately reproduce the main features of the flight environment.

The simulation of the geosynchronous Earth orbit plasma environment in Chamber A: An assessment of possible experimental investigations

NASA Technical Reports Server (NTRS)

Bernstein, W.

1981-01-01

The possible use of Chamber A for the replication or simulation of space plasma physics processes which occur in the geosynchronous Earth orbit (GEO) environment is considered. It is shown that replication is not possible and that scaling of the environmental conditions is required for study of the important instability processes. Rules for such experimental scaling are given. At the present time, it does not appear technologically feasible to satisfy these requirements in Chamber A. It is, however, possible to study and qualitatively evaluate the problem of vehicle charging at GEO. In particular, Chamber A is sufficiently large that a complete operational spacecraft could be irradiated by beams and charged to high potentials. Such testing would contribute to the assessment of the operational malfunctions expected at GEO and their possible correction. However, because of the many tabulated limitations in such a testing programs, its direct relevance to conditions expected in the geo environment remains questionable.

Corrosion Preventive Compounds Lifetime Testing

NASA Technical Reports Server (NTRS)

Hale, Stephanie M.; Kammerer, Catherine C.; Copp, Tracy L.

2007-01-01

Lifetime Testing of Corrosion Preventive Compounds (CPCs) was performed to quantify performance in the various environments to which the Space Shuttle Orbiter is exposed during a flight cycle. Three CPCs are approved for use on the Orbiter: RD Calcium Grease, Dinitrol AV-30, and Braycote 601 EF. These CPCs have been rigorously tested to prove that they mitigate corrosion in typical environments, but little information is available on how they perform in the unique combination of the coastal environment at the launch pad, the vacuum of low-earth orbit, and the extreme heat of reentry. Currently, there is no lifetime or reapplication schedule established for these compounds that is based on this combination of environmental conditions. Aluminum 2024 coupons were coated with the three CPCs and exposed to conditions that simulate the environments to which the Orbiter is exposed. Uncoated Aluminum 2024 coupons were exposed to the environmental conditions as a control. Visual inspection and Electro- Impedance Spectroscopy (EIS) were performed on the samples in order to determine the effectiveness of the CPCs. The samples were processed through five mission life cycles or until the visual inspection revealed the initiation of corrosion and EIS indicated severe degradation of the coating.

Corrosion Preventive Compounds Lifetime Testing

NASA Technical Reports Server (NTRS)

Hale, Stephanie M.; Kammerer, Catherine C.

2007-01-01

Lifetime Testing of Corrosion Preventive Compounds (CPCs) was performed to quantify performance in the various environments to which the Space Shuttle Orbiter is exposed during a flight cycle. Three CPCs are approved for use on the Orbiter: HD Calcium Grease, Dinitrol AV-30, and Braycote 601 EF. These CPCs have been rigorously tested to prove that they mitigate corrosion in typical environments, but little information is available on how they perform in the unique combination of the coastal environment at the launch pad, the vacuum of low-earth orbit, and the extreme heat of reentry. Currently, there is no lifetime or reapplication schedule established for these compounds that is based on this combination of environmental conditions. Aluminum 2024 coupons were coated with the three CPCs and exposed to conditions that simulate the environments to which the Orbiter is exposed. Uncoated Aluminum 2024 coupons were exposed to the environmental conditions as a control. Visual inspection and Electro- Impedance Spectroscopy (EIS) were performed on the samples in order to determine the effectiveness of the CPCs. The samples were processed through five mission life cycles or until the visual inspection revealed the initiation of corrosion and EIS indicated severe degradation of the coating.

Modeling the space debris environment with MASTER-2009 and ORDEM2010

NASA Astrophysics Data System (ADS)

Flegel, Sven Kevin; Krisko, Paula; Gelhaus, Johannes; Wiedemann, Carsten; Moeckel, Marek; Krag, Holger; Klinkrad, Heiner; Xu, Yu-Lin; Horstman, Matthew; Matney, Mark; Vörsmann, Peter

The two software tools MASTER-2009 and ORDEM2010 are the ESA and NASA reference software tools respectively which describe the earth's debris environment. The primary goal of both programs is to allow users to estimate the object flux onto a target object for mission planning. The current paper describes the basic distinctions in the model philosophies. At the core of each model lies the method by which the object environment is established. Cen-tral to this process is the role played by the results from radar/telescope observations or impact fluxes on surfaces returned from earth orbit. The ESA Meteoroid and Space Debris Terrestrial Environment Reference Model (MASTER) is engineered to give a realistic description of the natural and the man-made particulate environment of the earth. Debris sources are simulated based on detailed lists of known historical events such as fragmentations or solid rocket motor firings or through simulation of secondary debris such as impact ejecta or the release of paint flakes from degrading spacecraft surfaces. The resulting population is then validated against historical telescope/radar campaigns using the ESA Program for Radar and Optical Observa-tion Forecasting (PROOF) and against object impact fluxes on surfaces returned from space. The NASA Orbital Debris Engineering Model (ORDEM) series is designed to provide reliable estimates of orbital debris flux on spacecraft and through telescope or radar fields-of-view. Central to the model series is the empirical nature of the input populations. These are derived from NASA orbital debris modeling but verified, where possible, with measurement data from various sources. The latest version of the series, ORDEM2010, compiles over two decades of data from NASA radar systems, telescopes, in-situ sources, and ground tests that are analyzed by statistical methods. For increased understanding of the application ranges of the two programs, the current paper provides an overview of the two models' main program features and the methods by which simulation results are presented. This paper is written in a combined effort by ESA and NASA.

Thermo-electrochemical analysis of lithium ion batteries for space applications using Thermal Desktop

NASA Astrophysics Data System (ADS)

Walker, W.; Ardebili, H.

2014-12-01

Lithium-ion batteries (LIBs) are replacing the Nickel-Hydrogen batteries used on the International Space Station (ISS). Knowing that LIB efficiency and survivability are greatly influenced by temperature, this study focuses on the thermo-electrochemical analysis of LIBs in space orbit. Current finite element modeling software allows for advanced simulation of the thermo-electrochemical processes; however the heat transfer simulation capabilities of said software suites do not allow for the extreme complexities of orbital-space environments like those experienced by the ISS. In this study, we have coupled the existing thermo-electrochemical models representing heat generation in LIBs during discharge cycles with specialized orbital-thermal software, Thermal Desktop (TD). Our model's parameters were obtained from a previous thermo-electrochemical model of a 185 Amp-Hour (Ah) LIB with 1-3 C (C) discharge cycles for both forced and natural convection environments at 300 K. Our TD model successfully simulates the temperature vs. depth-of-discharge (DOD) profiles and temperature ranges for all discharge and convection variations with minimal deviation through the programming of FORTRAN logic representing each variable as a function of relationship to DOD. Multiple parametrics were considered in a second and third set of cases whose results display vital data in advancing our understanding of accurate thermal modeling of LIBs.

Simulated orbits of heavy planetary ions at Mars for different IMF configurations

NASA Astrophysics Data System (ADS)

Curry, Shannon; Luhmann, Janet; Livi, Roberto; Hara, Takuya; Dong, Chuanfei; Ma, Yingjuan; McFadden, James; Bougher, Stephen

2014-11-01

We present simulated detections of O+, O2+ and CO2+ ions at Mars along a virtual orbit in the Mars space environment. Planetary pick-up ions are formed through the direct interaction of the solar wind with the neutral upper atmosphere, causing the newly created ions to be picked up and accelerated by the background convective electric field. Because previous missions such as Mars Global Surveyor (MGS) and Mars Express (MEX) have not been able to measure the interplanetary magnetic field (IMF) components simultaneously with plasma measurements, the response of heavy planetary pick-up ions to changes in the IMF has not been well characterized. Using a steady-state multi-species MHD model to provide the background electric and magnetic fields, the Mars Test Particle (MTP) simulation can trace each of these particles along field lines in near-Mars space and construct virtual ion detections from a spacecraft orbit. Specifically, we will present energy-time spectrograms and velocity space distributions (VSDs) for a selection of orbits during different IMF configurations and solar cycle conditions. These simulated orbits have broader implications for how to measure ion escape. Using individual particle traces, the origin and trajectories of different ion populations can be analyzed in order to assess how and where they contribute to the total atmospheric escape rate, which is a major objective of the upcoming MAVEN mission.

Space Weathering Experiments on Spacecraft Materials

NASA Technical Reports Server (NTRS)

Engelhart, D. P.; Cooper, R.; Cowardin, H.; Maxwell, J.; Plis, E.; Ferguson, D.; Barton, D.; Schiefer, S.; Hoffmann, R.

2017-01-01

A project to investigate space environment effects on specific materials with interest to remote sensing was initiated in 2016. The goal of the project is to better characterize changes in the optical properties of polymers found in multi-layered spacecraft insulation (MLI) induced by electron bombardment. Previous analysis shows that chemical bonds break and potentially reform when exposed to high energy electrons like those seen in orbit. These chemical changes have been shown to alter a material's optical reflectance, among other material properties. This paper presents the initial experimental results of MLI materials exposed to various fluences of high energy electrons, designed to simulate a portion of the geosynchronous Earth orbit (GEO) space environment. It is shown that the spectral reflectance of some of the tested materials changes as a function of electron dose. These results provide an experimental benchmark for analysis of aging effects on satellite systems which can be used to improve remote sensing and space situational awareness. They also provide preliminary analysis on those materials that are most likely to comprise the high area-to-mass ratio (HAMR) population of space debris in the geosynchronous orbit environment. Finally, the results presented in this paper serve as a proof of concept for simulated environmental aging of spacecraft polymers that should lead to more experiments using a larger subset of spacecraft materials.

Simulation Modeling and Performance Evaluation of Space Networks

NASA Technical Reports Server (NTRS)

Jennings, Esther H.; Segui, John

2006-01-01

In space exploration missions, the coordinated use of spacecraft as communication relays increases the efficiency of the endeavors. To conduct trade-off studies of the performance and resource usage of different communication protocols and network designs, JPL designed a comprehensive extendable tool, the Multi-mission Advanced Communications Hybrid Environment for Test and Evaluation (MACHETE). The design and development of MACHETE began in 2000 and is constantly evolving. Currently, MACHETE contains Consultative Committee for Space Data Systems (CCSDS) protocol standards such as Proximity-1, Advanced Orbiting Systems (AOS), Packet Telemetry/Telecommand, Space Communications Protocol Specification (SCPS), and the CCSDS File Delivery Protocol (CFDP). MACHETE uses the Aerospace Corporation s Satellite Orbital Analysis Program (SOAP) to generate the orbital geometry information and contact opportunities. Matlab scripts provide the link characteristics. At the core of MACHETE is a discrete event simulator, QualNet. Delay Tolerant Networking (DTN) is an end-to-end architecture providing communication in and/or through highly stressed networking environments. Stressed networking environments include those with intermittent connectivity, large and/or variable delays, and high bit error rates. To provide its services, the DTN protocols reside at the application layer of the constituent internets, forming a store-and-forward overlay network. The key capabilities of the bundling protocols include custody-based reliability, ability to cope with intermittent connectivity, ability to take advantage of scheduled and opportunistic connectivity, and late binding of names to addresses. In this presentation, we report on the addition of MACHETE models needed to support DTN, namely: the Bundle Protocol (BP) model. To illustrate the use of MACHETE with the additional DTN model, we provide an example simulation to benchmark its performance. We demonstrate the use of the DTN protocol and discuss statistics gathered concerning the total time needed to simulate numerous bundle transmissions

Additional historical solid rocket motor burns

NASA Astrophysics Data System (ADS)

Wiedemann, Carsten; Homeister, Maren; Oswald, Michael; Stabroth, Sebastian; Klinkrad, Heiner; Vörsmann, Peter

2009-06-01

The use of orbital solid rocket motors (SRM) is responsible for the release of a high number of slag and Al 2O 3 dust particles which contribute to the space debris environment. This contribution has been modeled for the ESA space debris model MASTER (Meteoroid and Space Debris Terrestrial Environment Reference). The current model version, MASTER-2005, is based on the simulation of 1076 orbital SRM firings which mainly contributed to the long-term debris environment. SRM firings on very low earth orbits which produce only short living particles are not considered. A comparison of the modeled flux with impact data from returned surfaces shows that the shape and quantity of the modeled SRM dust distribution matches that of recent Hubble Space Telescope (HST) solar array measurements very well. However, the absolute flux level for dust is under-predicted for some of the analyzed Long Duration Exposure Facility (LDEF) surfaces. This indicates that some past SRM firings are not included in the current event database. Thus it is necessary to investigate, if additional historical SRM burns, like the retro-burn of low orbiting re-entry capsules, may be responsible for these dust impacts. The most suitable candidates for these firings are the large number of SRM retro-burns of return capsules. This paper focuses on the SRM retro-burns of Russian photoreconnaissance satellites, which were used in high numbers during the time of the LDEF mission. It is discussed which types of satellites and motors may have been responsible for this historical contribution. Altogether, 870 additional SRM retro-burns have been identified. An important task is the identification of such missions to complete the current event data base. Different types of motors have been used to de-orbit both large satellites and small film return capsules. The results of simulation runs are presented.

A fully coupled flow simulation around spacecraft in low earth orbit

NASA Technical Reports Server (NTRS)

Justiz, C. R.; Sega, R. M.

1991-01-01

The primary objective of this investigation is to provide a full flow simulation of a spacecraft in low earth orbit (LEO). Due to the nature of the environment, the simulation includes the highly coupled effects of neutral particle flow, free stream plasma flow, nonequilibrium gas dynamics effects, spacecraft charging and electromagnetic field effects. Emphasis is placed on the near wake phenomenon and will be verified in space by the Wake Shield Facility (WSF) and developed for application to Space Station conditions as well as for other spacecraft. The WSF is a metallic disk-type structure that will provide a controlled space platform for highly accurate measurements. Preliminary results are presented for a full flow around a metallic disk.

Demonstration of an Aerocapture GN and C System Through Hardware-in-the-Loop Simulations

NASA Technical Reports Server (NTRS)

Masciarelli, James; Deppen, Jennifer; Bladt, Jeff; Fleck, Jeff; Lawson, Dave

2010-01-01

Aerocapture is an orbit insertion maneuver in which a spacecraft flies through a planetary atmosphere one time using drag force to decelerate and effect a hyperbolic to elliptical orbit change. Aerocapture employs a feedback Guidance, Navigation, and Control (GN&C) system to deliver the spacecraft into a precise postatmospheric orbit despite the uncertainties inherent in planetary atmosphere knowledge, entry targeting and aerodynamic predictions. Only small amounts of propellant are required for attitude control and orbit adjustments, thereby providing mass savings of hundreds to thousands of kilograms over conventional all-propulsive techniques. The Analytic Predictor Corrector (APC) guidance algorithm has been developed to steer the vehicle through the aerocapture maneuver using bank angle control. Through funding provided by NASA's In-Space Propulsion Technology Program, the operation of an aerocapture GN&C system has been demonstrated in high-fidelity simulations that include real-time hardware in the loop, thus increasing the Technology Readiness Level (TRL) of aerocapture GN&C. First, a non-real-time (NRT), 6-DOF trajectory simulation was developed for the aerocapture trajectory. The simulation included vehicle dynamics, gravity model, atmosphere model, aerodynamics model, inertial measurement unit (IMU) model, attitude control thruster torque models, and GN&C algorithms (including the APC aerocapture guidance). The simulation used the vehicle and mission parameters from the ST-9 mission. A 2000 case Monte Carlo simulation was performed and results show an aerocapture success rate of greater than 99.7%, greater than 95% of total delta-V required for orbit insertion is provided by aerodynamic drag, and post-aerocapture orbit plane wedge angle error is less than 0.5 deg (3-sigma). Then a real-time (RT), 6-DOF simulation for the aerocapture trajectory was developed which demonstrated the guidance software executing on a flight-like computer, interfacing with a simulated IMU and simulated thrusters, with vehicle dynamics provided by an external simulator. Five cases from the NRT simulations were run in the RT simulation environment. The results compare well to those of the NRT simulation thus verifying the RT simulation configuration. The results of the above described simulations show the aerocapture maneuver using the APC algorithm can be accomplished reliably and the algorithm is now at TRL-6. Flight validation is the next step for aerocapture technology development.

Characterization of Orbital Debris Photometric Properties Derived from Laboratory-Based Measurements

NASA Technical Reports Server (NTRS)

Cowardin, Heather; Seitzer, Pat; Abercromby, Kira; Barker, Ed; Schildknecht, Thomas

2010-01-01

Capitalizing on optical data products and applying them to generate a more complete understanding of orbital space objects, is a key objective of NASA's Optical Measurement Program, and a primary objective for the creation of the Optical Measurements Center(OMC). The OMC attempts to emulate space-based illumination conditions using equipment and techniques that parallel telescopic observations and source-target-sensor orientations. The data acquired in the OMC are a function of known shape, size, and material. These three physical parameters are key to understanding the orbital debris environment in more depth. For optical observations, one must rely on spectroscopic or photometric measurements to ascertain an object's material type. Determination of an object s shape using remote observations is more complicated due to the various light scattering properties each object present and is a subject that requires more study. It is much easier to look at the periodicity of the light curve and analyze its structure for rotation. In order to best simulate the orbital debris population, three main sources were used as test fragments for optical measurements: flight-ready materials, destructive hypervelocity testing (simulating on-orbit collisions) and destructive pressure testing (simulating on-orbit explosions). Laboratory optical characteristics of fragments were measured, including light curve shape, phase angle dependence, and photometric and spectroscopic color indices. These characteristics were then compared with similar optical measurements acquired from telescopic observations in order to correlate remote and laboratory properties with the intent of ascertaining the intrinsic properties of the observed orbital debris

End-to-end simulation and verification of GNC and robotic systems considering both space segment and ground segment

NASA Astrophysics Data System (ADS)

Benninghoff, Heike; Rems, Florian; Risse, Eicke; Brunner, Bernhard; Stelzer, Martin; Krenn, Rainer; Reiner, Matthias; Stangl, Christian; Gnat, Marcin

2018-01-01

In the framework of a project called on-orbit servicing end-to-end simulation, the final approach and capture of a tumbling client satellite in an on-orbit servicing mission are simulated. The necessary components are developed and the entire end-to-end chain is tested and verified. This involves both on-board and on-ground systems. The space segment comprises a passive client satellite, and an active service satellite with its rendezvous and berthing payload. The space segment is simulated using a software satellite simulator and two robotic, hardware-in-the-loop test beds, the European Proximity Operations Simulator (EPOS) 2.0 and the OOS-Sim. The ground segment is established as for a real servicing mission, such that realistic operations can be performed from the different consoles in the control room. During the simulation of the telerobotic operation, it is important to provide a realistic communication environment with different parameters like they occur in the real world (realistic delay and jitter, for example).

The Orbital Maneuvering Vehicle Training Facility visual system concept

NASA Technical Reports Server (NTRS)

Williams, Keith

1989-01-01

The purpose of the Orbital Maneuvering Vehicle (OMV) Training Facility (OTF) is to provide effective training for OMV pilots. A critical part of the training environment is the Visual System, which will simulate the video scenes produced by the OMV Closed-Circuit Television (CCTV) system. The simulation will include camera models, dynamic target models, moving appendages, and scene degradation due to the compression/decompression of video signal. Video system malfunctions will also be provided to ensure that the pilot is ready to meet all challenges the real-world might provide. One possible visual system configuration for the training facility that will meet existing requirements is described.

Atomic oxygen interaction with spacecraft materials: Relationship between orbital and ground-based testing for materials certification

NASA Technical Reports Server (NTRS)

Cross, Jon B.; Koontz, Steven L.; Lan, Esther H.

1993-01-01

The effects of atomic oxygen on boron nitride (BN), silicon nitride (Si3N4), Intelsat 6 solar cell interconnects, organic polymers, and MoS2 and WS2 dry lubricant, were studied in Low Earth Orbit (LEO) flight experiments and in a ground based simulation facility. Both the inflight and ground based experiments employed in situ electrical resistance measurements to detect penetration of atomic oxygen through materials and Electron Spectroscopy for Chemical Analysis (ESCA) analysis to measure chemical composition changes. Results are given. The ground based results on the materials studied to date show good qualitative correlation with the LEO flight results, thus validating the simulation fidelity of the ground based facility in terms of reproducing LEO flight results. In addition it was demonstrated that ground based simulation is capable of performing more detailed experiments than orbital exposures can presently perform. This allows the development of a fundamental understanding of the mechanisms involved in the LEO environment degradation of materials.

Development of a continuous broad-energy-spectrum electron source

NASA Technical Reports Server (NTRS)

Adamo, R. C.; Nanevicz, J. E.

1985-01-01

The development of a practical prototype, large-area, continuous-spectrum, multienergy electron source to simulate the lower energy (approx = 1 to 30 keV) portion of the geosynchronous orbit electron environment was investigated. The results of future materials-charging tests using this multienergy source should significantly improve the understanding of actual in-orbit charging processes and should help to resolve some of the descrepancies between predicted and observed spacecraft materials performance.

Synthesis of amino acids in earth orbit: proposal

NASA Astrophysics Data System (ADS)

Kobayashi, Kensei; Kaneko, Takeo; Kouchi, Akira; Hashimoto, Hirofumi; Saito, Takeshi; Yamashita, Masamichi

1999-01-01

Organic compounds in comets are of interest since they could be the sources of the terrestrial biosphere. They are supposed to be formed in an interstellar dust (ISD) environment. We performed laboratory simulation of the formation of bioorganic compounds in ISD environments: Amino acid precursors were detected in the products after ice mixture of CO (or CH4, CH3OH), NH3 and H2O. The present results should be confirmed in actual space conditions, such as in an exposed facility of JEM. We are designing an apparatus of such exobiology experiments in earth orbit (EEEO). Basic designs proposed for EEEO, remaining problems, and expected outcome will be discussed.

Relative Positioning Evaluation of a Tetrahedral Flight Formation’s Satellites

NASA Astrophysics Data System (ADS)

Mahler, W. F. C.; Rocco, E. M.; Santos, D. P. S.

2017-10-01

This paper presents a study about the tetrahedral layout of four satellites in a way that every half-orbital period this set groups together while flying in formation. The formation is calculated analyzing the problem from a geometrical perspective and disposed by precisely adjusting the orbital parameters of each satellite. The dynamic modelling considers the orbital motion equations. The results are analyzed, compared and discussed. A detection algorithm is used as flag to signal the regular tetrahedron’s exact moments of occurrence. To do so, the volume calculated during the simulation is compared to the real volume, based on the initial conditions of the exact moment of formation and respecting a tolerance. This tolerance value is stablished arbitrarily depending on the mission and the formation’s geometrical parameters. The simulations will run on a computational environment.

Technology for robotic surface inspection in space

NASA Technical Reports Server (NTRS)

Volpe, Richard; Balaram, J.

1994-01-01

This paper presents on-going research in robotic inspection of space platforms. Three main areas of investigation are discussed: machine vision inspection techniques, an integrated sensor end-effector, and an orbital environment laboratory simulation. Machine vision inspection utilizes automatic comparison of new and reference images to detect on-orbit induced damage such as micrometeorite impacts. The cameras and lighting used for this inspection are housed in a multisensor end-effector, which also contains a suite of sensors for detection of temperature, gas leaks, proximity, and forces. To fully test all of these sensors, a realistic space platform mock-up has been created, complete with visual, temperature, and gas anomalies. Further, changing orbital lighting conditions are effectively mimicked by a robotic solar simulator. In the paper, each of these technology components will be discussed, and experimental results are provided.

Flight Validation of Mars Mission Technologies

NASA Technical Reports Server (NTRS)

Eberspeaker, P. J.

2000-01-01

Effective exploration and characterization of Mars will require the deployment of numerous surface probes, tethered balloon stations and free-flying balloon systems as well as larger landers and orbiting satellite systems. Since launch opportunities exist approximately every two years it is extremely critical that each and every mission maximize its potential for success. This will require significant testing of each system in an environment that simulates the actual operational environment as closely as possible. Analytical techniques and laboratory testing goes a long way in mitigating the inherent risks associated with space exploration, however they fall sort of accurately simulating the unpredictable operational environment in which these systems must function.

Simulation of major space particles toward selected materials in a near-equatorial low earth orbit

NASA Astrophysics Data System (ADS)

Suparta, Wayan; Zulkeple, Siti Katrina

2017-05-01

A low earth orbit near the equator (LEO-NEqO) is exposed to the highest energies from galactic cosmic rays (GCR) and from trapped protons with a wide range of energies. Moreover, GCR fluxes were seen to be the highest in 2009 to 2010 when communication belonging to the RazakSAT-1 satellite was believed to have been lost. Hence, this study aimed to determine the influence of the space environment toward the operation of LEO-NEqO satellites by investigating the behavior of major space particles toward satellite materials. The space environment was referred to GCR protons and trapped protons. Their fluxes were obtained from the Space Environment Information System (SPENVIS) and their tracks were simulated through three materials using a simulation program called Geometry and Tracking (Geant4). The materials included aluminum (Al), gallium arsenide (GaAs) and silicon (Si). Then the total ionizing dose (TID) and non-ionizing dose (NIEL) were calculated for a three-year period. Simulations showed that GCR traveled at longer tracks and produced more secondary radiation than trapped protons. Al turned out to receive the lowest total dose, while GaAs showed to be susceptible toward GCR than Si. However, trapped protons contributed the most in spacecraft doses where Si received the highest doses. Finally, the comparison between two Geant4 programs revealed the estimated doses differed at <18%.

The 11th Space Simulation Conference

NASA Technical Reports Server (NTRS)

Bond, A. C. (Editor)

1980-01-01

Subject areas range from specialized issues dealing with the space and entry environments to the environmental testing of systems and complete spacecraft of present-day vintage. Various papers consider: the test and development of several key systems of the orbiter vehicle; integrated tests of complete satellites; new and unique test facilities developed to meet the demanding requirements of high fidelity simulation of test environments; and contamination species, including the instrumentation for detection and measurement of such. Special topics include improved thermal protection methodologies and approaches, sophisticated sensor developments, and other related testing and development areas.

High temperature antenna development for space shuttle, volume 2. [space environment simulation effects on antenna radiation patterns

NASA Technical Reports Server (NTRS)

Kuhlman, E. A.

1974-01-01

An S-band antenna system and a group of off-the-shelf aircraft antenna were exposed to temperatures simulating shuttle orbital cold soak and entry heating. Radiation pattern and impedance measurements before and after exposure to the thermal environments were used to evaluate the electrical performance. The results of the electrical and thermal testing are given. Test data showed minor changes in electrical performance and established the capability of these antenna to withstand both the low temperatures of space flight and the high temperatures of entry.

Technology, design, simulation, and evaluation for SEP-hardened circuits

NASA Technical Reports Server (NTRS)

Adams, J. R.; Allred, D.; Barry, M.; Rudeck, P.; Woodruff, R.; Hoekstra, J.; Gardner, H.

1991-01-01

This paper describes the technology, design, simulation, and evaluation for improvement of the Single Event Phenomena (SEP) hardness of gate-array and SRAM cells. Through the use of design and processing techniques, it is possible to achieve an SEP error rate less than 1.0 x 10(exp -10) errors/bit-day for a 9O percent worst-case geosynchronous orbit environment.

On-Board Entry Trajectory Planning Expanded to Sub-orbital Flight

NASA Technical Reports Server (NTRS)

Lu, Ping; Shen, Zuojun

2003-01-01

A methodology for on-board planning of sub-orbital entry trajectories is developed. The algorithm is able to generate in a time frame consistent with on-board environment a three-degree-of-freedom (3DOF) feasible entry trajectory, given the boundary conditions and vehicle modeling. This trajectory is then tracked by feedback guidance laws which issue guidance commands. The current trajectory planning algorithm complements the recently developed method for on-board 3DOF entry trajectory generation for orbital missions, and provides full-envelope autonomous adaptive entry guidance capability. The algorithm is validated and verified by extensive high fidelity simulations using a sub-orbital reusable launch vehicle model and difficult mission scenarios including failures and aborts.

Precision orbit raising trajectories. [solar electric propulsion orbital transfer program

NASA Technical Reports Server (NTRS)

Flanagan, P. F.; Horsewood, J. L.; Pines, S.

1975-01-01

A precision trajectory program has been developed to serve as a test bed for geocentric orbit raising steering laws. The steering laws to be evaluated have been developed using optimization methods employing averaging techniques. This program provides the capability of testing the steering laws in a precision simulation. The principal system models incorporated in the program are described, including the radiation environment, the solar array model, the thrusters and power processors, the geopotential, and the solar system. Steering and array orientation constraints are discussed, and the impact of these constraints on program design is considered.

Microgravity science and applications: Apparatus and facilities

NASA Technical Reports Server (NTRS)

1989-01-01

NASA support apparatus and facilities for microgravity research are summarized in fact sheets. The facilities are ground-based simulation environments for short-term experiments, and the shuttle orbiter environment for long duration experiments. The 17 items of the microgravitational experimental apparatus are described. Electronic materials, alloys, biotechnology, fluid dynamics and transport phenomena, glasses and ceramics, and combustion science are among the topics covered.

Assessment of analytical and experimental techniques utilized in conducting plume technology tests 575 and 593. [exhaust flow simulation (wind tunnel tests) of scale model Space Shuttle Orbiter

NASA Technical Reports Server (NTRS)

Baker, L. R.; Sulyma, P. R.; Tevepaugh, J. A.; Penny, M. M.

1976-01-01

Since exhaust plumes affect vehicle base environment (pressure and heat loads) and the orbiter vehicle aerodynamic control surface effectiveness, an intensive program involving detailed analytical and experimental investigations of the exhaust plume/vehicle interaction was undertaken as a pertinent part of the overall space shuttle development program. The program, called the Plume Technology program, has as its objective the determination of the criteria for simulating rocket engine (in particular, space shuttle propulsion system) plume-induced aerodynamic effects in a wind tunnel environment. The comprehensive experimental program was conducted using test facilities at NASA's Marshall Space Flight Center and Ames Research Center. A post-test examination of some of the experimental results obtained from NASA-MSFC's 14 x 14-inch trisonic wind tunnel is presented. A description is given of the test facility, simulant gas supply system, nozzle hardware, test procedure and test matrix. Analysis of exhaust plume flow fields and comparison of analytical and experimental exhaust plume data are presented.

Data Collected During the Post-Flight Survey of Micrometeoroid and Orbital Debris Impact Features on the Hubble Wide Field Planetary Camera 2

NASA Technical Reports Server (NTRS)

Opiela, J. N.; Liou, J.-C.; Anz-Meador, P. D.

2010-01-01

Over a period of five weeks during the summer of 2009, personnel from the NASA's Orbital Debris Program Office and Meteoroid Environment Office performed a post-flight examination of the Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC-2) radiator. The objective was to record details about all micrometeoroid and orbital debris (MMOD) impact features with diameters of 300 micron and larger. The WFPC-2 was located in a clean room at NASA's Goddard Space Flight Center. Using a digital microscope, the team examined and recorded position, diameter, and depth information for each of 685 craters. Taking advantage of the digital microscope's data storage and analysis features, the actual measurements were extracted later from the recorded images, in an office environment at the Johnson Space Center. Measurements of the crater include depth and diameter. The depth was measured from the undisturbed paint surface to the deepest point within the crater. Where features penetrate into the metal, both the depth in metal and the paint thickness were measured. In anticipation of hypervelocity tests and simulations, several diameter measurements were taken: the spall area, the area of any bare metal, the area of any discolored ("burned") metal, and the lips of the central crater. In the largest craters, the diameter of the crater at the surface of the metal was also measured. The location of each crater was recorded at the time of inspection. This paper presents the methods and results of the crater measurement effort, including the size and spatial distributions of the impact features. This effort will be followed by taking the same measurements from hypervelocity impact targets simulating the WFPC-2 radiator. Both data sets, combined with hydrocode simulation, will help validate or improve the MMOD environment in low Earth orbit.

Use of microgravity sensors for quantification of space shuttle orbiter vernier reaction control system induced environments

NASA Technical Reports Server (NTRS)

Friend, Robert B.

1998-01-01

In the modeling of spacecraft dynamics it is important to accurately characterize the environment in which the vehicle operates, including the environments induced by the vehicle itself. On the Space Shuttle these induced environmental factors include reaction control system plume. Knowledge of these environments is necessary for performance of control systems and loads analyses, estimation of disturbances due to thruster firings, and accurate state vector propagation. During the STS-71 mission, while the Orbiter was performing attitude control for the mated Orbiter/Mir stack, it was noted that the autopilot was limit cycling at a rate higher than expected from pre-flight simulations. Investigations during the mission resulted in the conjecture that an unmodelled plume impingement force was acting upon the orbiter elevons. The in-flight investigations were not successful in determining the actual magnitude of the impingement, resulting in several sequential post-flight investigations. Efforts performed to better quantify the vernier reaction control system induced plume impingement environment of the Space Shuttle orbiter are described in this paper, and background detailing circumstances which required the more detailed knowledge of the RCS self impingement forces, as well as a description of the resulting investigations and their results is presented. The investigations described in this paper applied microgravity acceleration data from two shuttle borne microgravity experiments, SAMS and OARE, to the solution of this particular problem. This solution, now used by shuttle analysts and mission planners, results in more accurate propellant consumption and attitude limit cycle estimates in preflight analyses, which are critical for pending International Space Station missions.

NASCAP user's manual, 1978

NASA Technical Reports Server (NTRS)

Cassidy, J. J., III

1978-01-01

NASCAP simulates the charging process for a complex object in either tenuous plasma (geosynchronous orbit) or ground test (electron gun source) environment. Program control words, the structure of user input files, and various user options available are described in this computer programmer's user manual.

Space environment effects on polymers in low earth orbit

NASA Astrophysics Data System (ADS)

Grossman, E.; Gouzman, I.

2003-08-01

Polymers are widely used in space vehicles and systems as structural materials, thermal blankets, thermal control coatings, conformal coatings, adhesives, lubricants, etc. The low earth orbit (LEO) space environment includes hazards such as atomic oxygen, UV radiation, ionizing radiation (electrons, protons), high vacuum, plasma, micrometeoroids and debris, as well as severe temperature cycles. Exposure of polymers and composites to the space environment may result in different detrimental effects via modification of their chemical, electrical, thermal, optical and mechanical properties as well as surface erosion. The high vacuum induces material outgassing (e.g. low-molecular weight residues, plasticizers and additives) and consequent contamination of nearby surfaces. The present work reviews the LEO space environment constituents and their interactions with polymers. Examples of degradation of materials exposed in ground simulation facilities are presented. The issues discussed include the erosion mechanisms of polymers, formation of contaminants and their interaction with the space environment, and protection of materials from the harsh space environment.

A Deep Space Orbit Determination Software: Overview and Event Prediction Capability

NASA Astrophysics Data System (ADS)

Kim, Youngkwang; Park, Sang-Young; Lee, Eunji; Kim, Minsik

2017-06-01

This paper presents an overview of deep space orbit determination software (DSODS), as well as validation and verification results on its event prediction capabilities. DSODS was developed in the MATLAB object-oriented programming environment to support the Korea Pathfinder Lunar Orbiter (KPLO) mission. DSODS has three major capabilities: celestial event prediction for spacecraft, orbit determination with deep space network (DSN) tracking data, and DSN tracking data simulation. To achieve its functionality requirements, DSODS consists of four modules: orbit propagation (OP), event prediction (EP), data simulation (DS), and orbit determination (OD) modules. This paper explains the highest-level data flows between modules in event prediction, orbit determination, and tracking data simulation processes. Furthermore, to address the event prediction capability of DSODS, this paper introduces OP and EP modules. The role of the OP module is to handle time and coordinate system conversions, to propagate spacecraft trajectories, and to handle the ephemerides of spacecraft and celestial bodies. Currently, the OP module utilizes the General Mission Analysis Tool (GMAT) as a third-party software component for highfidelity deep space propagation, as well as time and coordinate system conversions. The role of the EP module is to predict celestial events, including eclipses, and ground station visibilities, and this paper presents the functionality requirements of the EP module. The validation and verification results show that, for most cases, event prediction errors were less than 10 millisec when compared with flight proven mission analysis tools such as GMAT and Systems Tool Kit (STK). Thus, we conclude that DSODS is capable of predicting events for the KPLO in real mission applications.

Coronal mass ejection hits mercury: A.I.K.E.F. hybrid-code results compared to MESSENGER data

NASA Astrophysics Data System (ADS)

Exner, W.; Heyner, D.; Liuzzo, L.; Motschmann, U.; Shiota, D.; Kusano, K.; Shibayama, T.

2018-04-01

Mercury is the closest orbiting planet around the sun and is therefore embedded in an intensive and highly varying solar wind. In-situ data from the MESSENGER spacecraft of the plasma environment near Mercury indicates that a coronal mass ejection (CME) passed the planet on 23 November 2011 over the span of the 12 h MESSENGER orbit. Slavin et al. (2014) derived the upstream parameters of the solar wind at the time of that orbit, and were able to explain the observed MESSENGER data in the cusp and magnetopause segments of MESSENGER's trajectory. These upstream parameters will be used for our first simulation run. We use the hybrid code A.I.K.E.F. which treats ions as individual particles and electrons as a mass-less fluid, to conduct hybrid simulations of Mercury's magnetospheric response to the impact of the CME on ion gyro time scales. Results from the simulation are in agreement with magnetic field measurements from the inner day-side magnetosphere and the bow-shock region. However, at the planet's nightside, Mercury's plasma environment seemed to be governed by different solar wind conditions, in conclusion, Mercury's interaction with the CME is not sufficiently describable by only one set of upstream parameters. Therefore, to simulate the magnetospheric response while MESSENGER was located in the tail region, we use parameters obtained from the MHD solar wind simulation code SUSANOO (Shiota et al. (2014)) for our second simulation run. The parameters of the SUSANOO model achieve a good agreement of the data concerning the plasma tail crossing and the night-side approach to Mercury. However, the polar and closest approach are hardly described by both upstream parameters, namely, neither upstream dataset is able to reproduce the MESSENGER crossing of Mercury's magnetospheric cusp. We conclude that the respective CME was too variable on the timescale of the MESSENGER orbit to be described by only two sets of upstream conditions. Our results suggest locally strong and highly variable dynamics of the CME on timescales of 15 min while MESSENGER was near closest approach.

STS-26 Pilot Covey floats in life raft during JSC WETF exercises

NASA Technical Reports Server (NTRS)

1988-01-01

STS-26 Discovery, Orbiter Vehicle (OV) 103, Pilot Richard O. Covey, wearing newly designed launch and entry suit (LES), floats in single-occupant life raft during simulations in the JSC Weightless Environment Training Facility Bldg 29 pool. During the simulation of escape and rescue operations, the crew escape system (CES) pole mode of egress from the Space Shuttle was utilized.

Effects of CubeSat Deployments in Low-Earth Orbit

NASA Technical Reports Server (NTRS)

Matney, Mark; Vavrin, Andrew; Manis, Alyssa

2017-01-01

Long-term models, such as NASA's LEGEND (LEO-to- GEO Environment Debris) model, are used to make predictions about how space activities will affect the manner in which the debris environment evolves over time. Part of this process predicts how spacecraft and rocket bodies will be launched and remain in the future environment. This has usually been accomplished by repeating past launch history to simulate future launches. The NASA Orbital Debris Program Office (ODPO) has conducted a series of LEGEND computations to investigate the long-term effects of adding CubeSats to the environment. These results are compared to a baseline "business-as-usual" scenario where launches are assumed to continue as in the past without major CubeSat deployments. Using these results, we make observations about the continued use of the 25-year rule and the importance of the universal application of postmission disposal.

Testing of the on-board attitude determination and control algorithms for SAMPEX

NASA Technical Reports Server (NTRS)

Mccullough, Jon D.; Flatley, Thomas W.; Henretty, Debra A.; Markley, F. Landis; San, Josephine K.

1993-01-01

Algorithms for on-board attitude determination and control of the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) have been expanded to include a constant gain Kalman filter for the spacecraft angular momentum, pulse width modulation for the reaction wheel command, an algorithm to avoid pointing the Heavy Ion Large Telescope (HILT) instrument boresight along the spacecraft velocity vector, and the addition of digital sun sensor (DSS) failure detection logic. These improved algorithms were tested in a closed-loop environment for three orbit geometries, one with the sun perpendicular to the orbit plane, and two with the sun near the orbit plane - at Autumnal Equinox and at Winter Solstice. The closed-loop simulator was enhanced and used as a truth model for the control systems' performance evaluation and sensor/actuator contingency analysis. The simulations were performed on a VAX 8830 using a prototype version of the on-board software.

Performance monitor system functional simulator, environmental data, orbiter 101(HFT)

NASA Technical Reports Server (NTRS)

Parker, F. W.

1974-01-01

Information concerning the environment component of the space shuttle performance monitor system simulator (PMSS) and those subsystems operational on the shuttle orbiter 101 used for horizontal flight test (HFT) is provided, along with detailed data for the shuttle performance monitor system (PMS) whose software requirements evolve from three basic PMS functions: (1) fault detection and annunciation; (2) subsystem measurement management; and (3) subsystem configuration management. Information relative to the design and operation of Orbiter systems for HFT is also presented, and the functional paths are identified to the lowest level at which the crew can control the system functions. Measurement requirements are given which are necessary to adequately monitor the health status of the system. PMS process requirements, relative to the measurements which are necessary for fault detection and annunciation of a failed functional path, consist of measurement characteristics, tolerance limits, precondition tests, and correlation measurements.

Space as a Tool for Astrobiology: Review and Recommendations for Experimentations in Earth Orbit and Beyond

NASA Astrophysics Data System (ADS)

Cottin, Hervé; Kotler, Julia Michelle; Billi, Daniela; Cockell, Charles; Demets, René; Ehrenfreund, Pascale; Elsaesser, Andreas; d'Hendecourt, Louis; van Loon, Jack J. W. A.; Martins, Zita; Onofri, Silvano; Quinn, Richard C.; Rabbow, Elke; Rettberg, Petra; Ricco, Antonio J.; Slenzka, Klaus; de la Torre, Rosa; de Vera, Jean-Pierre; Westall, Frances; Carrasco, Nathalie; Fresneau, Aurélien; Kawaguchi, Yuko; Kebukawa, Yoko; Nguyen, Dara; Poch, Olivier; Saiagh, Kafila; Stalport, Fabien; Yamagishi, Akihiko; Yano, Hajime; Klamm, Benjamin A.

2017-07-01

The space environment is regularly used for experiments addressing astrobiology research goals. The specific conditions prevailing in Earth orbit and beyond, notably the radiative environment (photons and energetic particles) and the possibility to conduct long-duration measurements, have been the main motivations for developing experimental concepts to expose chemical or biological samples to outer space, or to use the reentry of a spacecraft on Earth to simulate the fall of a meteorite. This paper represents an overview of past and current research in astrobiology conducted in Earth orbit and beyond, with a special focus on ESA missions such as Biopan, STONE (on Russian FOTON capsules) and EXPOSE facilities (outside the International Space Station). The future of exposure platforms is discussed, notably how they can be improved for better science return, and how to incorporate the use of small satellites such as those built in cubesat format.

Orbit determination error analysis and comparison of station-keeping costs for Lissajous and halo-type libration point orbits and sensitivity analysis using experimental design techniques

NASA Technical Reports Server (NTRS)

Gordon, Steven C.

1993-01-01

Spacecraft in orbit near libration point L1 in the Sun-Earth system are excellent platforms for research concerning solar effects on the terrestrial environment. One spacecraft mission launched in 1978 used an L1 orbit for nearly 4 years, and future L1 orbital missions are also being planned. Orbit determination and station-keeping are, however, required for these orbits. In particular, orbit determination error analysis may be used to compute the state uncertainty after a predetermined tracking period; the predicted state uncertainty levels then will impact the control costs computed in station-keeping simulations. Error sources, such as solar radiation pressure and planetary mass uncertainties, are also incorporated. For future missions, there may be some flexibility in the type and size of the spacecraft's nominal trajectory, but different orbits may produce varying error analysis and station-keeping results. The nominal path, for instance, can be (nearly) periodic or distinctly quasi-periodic. A periodic 'halo' orbit may be constructed to be significantly larger than a quasi-periodic 'Lissajous' path; both may meet mission requirements, but perhaps the required control costs for these orbits are probably different. Also for this spacecraft tracking and control simulation problem, experimental design methods can be used to determine the most significant uncertainties. That is, these methods can determine the error sources in the tracking and control problem that most impact the control cost (output); it also produces an equation that gives the approximate functional relationship between the error inputs and the output.

Background and imaging simulations for the hard X-ray camera of the MIRAX mission

NASA Astrophysics Data System (ADS)

Castro, M.; Braga, J.; Penacchioni, A.; D'Amico, F.; Sacahui, R.

2016-07-01

We report the results of detailed Monte Carlo simulations of the performance expected both at balloon altitudes and at the probable satellite orbit of a hard X-ray coded-aperture camera being developed for the Monitor e Imageador de RAios X (MIRAX) mission. Based on a thorough mass model of the instrument and detailed specifications of the spectra and angular dependence of the various relevant radiation fields at both the stratospheric and orbital environments, we have used the well-known package GEANT4 to simulate the instrumental background of the camera. We also show simulated images of source fields to be observed and calculated the detailed sensitivity of the instrument in both situations. The results reported here are especially important to researchers in this field considering that we provide important information, not easily found in the literature, on how to prepare input files and calculate crucial instrumental parameters to perform GEANT4 simulations for high-energy astrophysics space experiments.

Monte-Carlo background simulations of present and future detectors in x-ray astronomy

NASA Astrophysics Data System (ADS)

Tenzer, C.; Kendziorra, E.; Santangelo, A.

2008-07-01

Reaching a low-level and well understood internal instrumental background is crucial for the scientific performance of an X-ray detector and, therefore, a main objective of the instrument designers. Monte-Carlo simulations of the physics processes and interactions taking place in a space-based X-ray detector as a result of its orbital environment can be applied to explain the measured background of existing missions. They are thus an excellent tool to predict and optimize the background of future observatories. Weak points of a design and the main sources of the background can be identified and methods to reduce them can be implemented and studied within the simulations. Using the Geant4 Monte-Carlo toolkit, we have created a simulation environment for space-based detectors and we present results of such background simulations for XMM-Newton's EPIC pn-CCD camera. The environment is also currently used to estimate and optimize the background of the future instruments Simbol-X and eRosita.

CO-ORBITING PLANES OF SUB-HALOS ARE SIMILARLY UNLIKELY AROUND PAIRED AND ISOLATED HOSTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pawlowski, Marcel S.; McGaugh, Stacy S., E-mail: marcel.pawlowski@case.edu

2014-07-01

Sub-halos in dark-matter-based cosmological simulations tend to be distributed approximately isotropically around their host. The existence of highly flattened, co-orbiting planes of satellite galaxies has therefore been identified as a possible problem for these cosmological models, but so far studies have not considered the hosts' environments. That satellite planes are now known around both major galaxies in the Local Group raises the question whether they are more likely to be found around paired hosts. In a first attempt to investigate this possibility, we focus on the flattening and orbital coherence of the 11 brightest satellite galaxies of the vast polarmore » structure (VPOS) around the Milky Way (MW). We search for VPOS analogs in the ''Exploring the Local Volume in Simulations'' suite of cosmological simulations, which consist of 24 paired and 24 isolated host halos. We do not find significant differences between the properties of sub-halo distributions around paired and isolated hosts. The observed flattening and the observed orbital alignment are each reproduced by only 0.2%-2% of paired and isolated systems incorporating the obscuration of satellites by randomly oriented galactic disks. Only 1 of all 4800 analyzed realizations (0.02%) reproduces both parameters simultaneously, but the average orbital pole of this sub-halo system does not align as well with the normal to the plane fit as observed. That the MW is part of a galaxy pair thus does not help to explain the existence of the VPOS if the satellite galaxies are identified with sub-halos found in dissipationless simulations.« less

Simulated annealing in orbital flight planning

NASA Technical Reports Server (NTRS)

Soller, Jeffrey

1990-01-01

Simulated annealing is used to solve a minimum fuel trajectory problem in the space station environment. The environment is unique because the space station will define the first true multivehicle environment in space. The optimization yields surfaces which are potentially complex, with multiple local minima. Because of the likelihood of these local minima, descent techniques are unable to offer robust solutions. Other deterministic optimization techniques were explored without success. The simulated annealing optimization is capable of identifying a minimum-fuel, two-burn trajectory subject to four constraints. Furthermore, the computational efforts involved in the optimization are such that missions could be planned on board the space station. Potential applications could include the on-site planning of rendezvous with a target craft of the emergency rescue of an astronaut. Future research will include multiwaypoint maneuvers, using a knowledge base to guide the optimization.

Aerospace Test Facilities at NASA LeRC Plumbrook

NASA Technical Reports Server (NTRS)

1992-01-01

An overview of the facilities and research being conducted at LeRC's Plumbrook field station is given. The video highlights four main structures and explains their uses. The Space Power Facility is the world's largest space environment simulation chamber, where spacebound hardware is tested in simulations of the vacuum and extreme heat and cold of the space plasma environment. This facility was used to prepare Atlas 1 rockets to ferry CRRES into orbit; it will also be used to test space nuclear electric power generation systems. The Spacecraft Propulsion Research Facility allows rocket vehicles to be hot fired in a simulated space environment. In the Cryogenic Propellant Tank Facility, researchers are developing technology for storing and transferring liquid hydrogen in space. There is also a Hypersonic Wind Tunnel which can perform flow tests with winds up to Mach 7.

Aerospace test facilities at NASA LERC Plumbrook

NASA Astrophysics Data System (ADS)

1992-10-01

An overview of the facilities and research being conducted at LeRC's Plumbrook field station is given. The video highlights four main structures and explains their uses. The Space Power Facility is the worlds largest space environment simulation chamber, where spacebound hardware is tested in simulations of the vacuum and extreme heat and cold of the space plasma environment. This facility was used to prepare Atlas 1 rockets to ferry CRRES into orbit; it will also be used to test space nuclear electric power generation systems. The Spacecraft Propulsion Research Facility allows rocket vehicles to be hot fired in a simulated space environment. In the Cryogenic Propellant Tank Facility, researchers are developing technology for storing and transferring liquid hydrogen in space. There is also a Hypersonic Wind Tunnel which can perform flow tests with winds up to Mach 7.

NASA welding assessment program

NASA Technical Reports Server (NTRS)

Patterson, R. E.

1985-01-01

A program was conducted to demonstrate the cycle life capability of welded solar cell modules relative to a soldered solar cell module in a simulated low earth orbit thermal environment. A total of five 18-cell welded (parallel gap resistance welding) modules, three 18-cell soldered modules, and eighteen single cell samples were fabricated using 2 x 4 cm silicon solar cells from ASEC, fused silica cover glass from OCLI, silver plated Invar interconnectors, DC 93-500 adhesive, and Kapton-Kevlar-Kapton flexible substrate material. Zero degree pull strength ranged from 2.4 to 5.7 lbs for front welded contacts (40 samples), and 3.5 to 6.2 lbs for back welded contacts (40 samples). Solar cell cross sections show solid state welding on both front and rear contacts. The 18-cell welded modules have a specific power of 124 W/kg and an area power density of 142 W/sq m (both at 28 C). Three welded and one soldered module were thermal cycle tested in a thermal vacuum chamber simulating a low earth orbit thermal environment.

Results of an investigation of jet plume effects on a 0.010-scale model (75-OTS) of the space shuttle integrated vehicle in the 8 x 7-foot leg of the NASA/Ames unitary wind tunnel (IA82C), volume 1. [(an exhaust flow simulation)

NASA Technical Reports Server (NTRS)

Hawthorne, P. J.

1976-01-01

The primary test objective was to define the base pressure environment of the first and second stage mated vehicle in a supersonic flow field from Mach 2.60 through 3.50 with simulated rocket engine exhaust plumes. The secondary objective was to obtain the pressure environment of the Orbiter at various vent port locations at these same freestream conditions. Data were obtained at angles of attack from -4 deg through +4 deg at zero yaw, and at yaw angles from -4 deg through +4 deg at zero angle of attack, with rocket plume sizes varying from smaller than nominal to much greater than nominal. Failed Orbiter engine data were also obtained. Elevon hinge moments and wing panel load data were obtained during all runs. Photographs of test equipment and tested configurations are shown.

The Influence of Solid Rocket Motor Retro-Burns on the Space Debris Environment

NASA Astrophysics Data System (ADS)

Stabroth, S.; Homeister, M.; Oswald, M.; Wiedemann, C.; Klinkrad, H.; Vörsmann, P.

The ESA space debris population model MASTER Meteoroid and Space Debris Terrestrial Environment Reference considers firings of solid rocket motors SRM as a debris source with the associated generation of slag and dust particles The resulting slag and dust population is a major contribution to the sub-millimetre size debris environment in Earth orbit The current model version MASTER-2005 is based on the simulation of 1 076 orbital SRM firings which contributed to the long-term debris environment A comparison of the modelled flux with impact data from returned surfaces shows that the shape and quantity of the modelled SRM dust distribution matches that of recent Hubble Space Telescope HST solar array measurements very well However the absolute flux level for dust is under-predicted for some of the analysed Long Duration Exposure Facility LDEF surfaces This points into the direction of some past SRM firings not included in the current event database The most suitable candidates for these firings are the large number of SRM retro-burns of return capsules Objects released by those firings have highly eccentric orbits with perigees in the lower regions of the atmosphere Thus they produce no long-term effect on the debris environment However a large number of those firings during the on-orbit time frame of LDEF might lead to an increase of the dust population for some of the LDEF surfaces In this paper the influence of SRM retro-burns on the short- and long-term debris environment is analysed The existing firing database is updated with gathered

Materials selection for long life in low earth orbit - A critical evaluation of atomic oxygen testing with thermal atom systems

NASA Technical Reports Server (NTRS)

Koontz, S. L.; Albyn, K.; Leger, L.

1990-01-01

The use of thermal atom test methods as a materials selection and screening technique for low-earth orbit (LEO) spacecraft is critically evaluated. The chemistry and physics of thermal atom environments are compared with the LEO environment. The relative reactivities of a number of materials determined in thermal atom environments are compared with those observed in LEO and in high-quality LEO simulations. Reaction efficiencies (cu cm/atom) measured in a new type of thermal atom apparatus are one-thousandth to one ten-thousandth those observed in LEO, and many materials showing nearly identical reactivities in LEO show relative reactivities differing by as much as a factor of eight in thermal atom systems. A simple phenomenological kinetic model for the reaction of oxygen atoms with organic materials can be used to explain the differences in reactivity in different environments. Certain speciic thermal atom test environments can be used as reliable materials screening tools.

8th Spacecraft Charging Technology Conference

NASA Technical Reports Server (NTRS)

Minor, J. L. (Compiler)

2004-01-01

The 8th Spacecraft Charging Technology Conference was held in Huntsville, Alabama, October 20-24, 2003. Hosted by NASA s Space Environments and Effects (SEE) Program and co-sponsored by the Air Force Research Laboratory (AFRL) and the European Space Agency (ESA), the 2003 conference saw attendance from eleven countries with over 65 oral papers and 18 poster papers. Presentation topics highlighted the latest in spacecraft charging mitigation techniques and on-orbit investigations, including: Plasma Propulsion and Tethers; Ground Testing Techniques; Interactions of Spacecraft and Systems With the Natural and Induced Plasma Environment; Materials Characterizations; Models and Computer Simulations; Environment Specifications; Current Collection and Plasma Probes in Space Plasmas; On-Orbit Investigations. A round-table discussion of international standards regarding electrostatic discharge (ESD) testing was also held with the promise of continued discussions in the off years and an official continuation at the next conference.

The Synergistic Engineering Environment

NASA Technical Reports Server (NTRS)

Cruz, Jonathan

2006-01-01

The Synergistic Engineering Environment (SEE) is a system of software dedicated to aiding the understanding of space mission operations. The SEE can integrate disparate sets of data with analytical capabilities, geometric models of spacecraft, and a visualization environment, all contributing to the creation of an interactive simulation of spacecraft. Initially designed to satisfy needs pertaining to the International Space Station, the SEE has been broadened in scope to include spacecraft ranging from those in low orbit around the Earth to those on deep-space missions. The SEE includes analytical capabilities in rigid-body dynamics, kinematics, orbital mechanics, and payload operations. These capabilities enable a user to perform real-time interactive engineering analyses focusing on diverse aspects of operations, including flight attitudes and maneuvers, docking of visiting spacecraft, robotic operations, impingement of spacecraft-engine exhaust plumes, obscuration of instrumentation fields of view, communications, and alternative assembly configurations. .

Implementation of an Open-Scenario, Long-Term Space Debris Simulation Approach

NASA Technical Reports Server (NTRS)

Nelson, Bron; Yang Yang, Fan; Carlino, Roberto; Dono Perez, Andres; Faber, Nicolas; Henze, Chris; Karacalioglu, Arif Goktug; O'Toole, Conor; Swenson, Jason; Stupl, Jan

2015-01-01

This paper provides a status update on the implementation of a flexible, long-term space debris simulation approach. The motivation is to build a tool that can assess the long-term impact of various options for debris-remediation, including the LightForce space debris collision avoidance concept that diverts objects using photon pressure [9]. State-of-the-art simulation approaches that assess the long-term development of the debris environment use either completely statistical approaches, or they rely on large time steps on the order of several days if they simulate the positions of single objects over time. They cannot be easily adapted to investigate the impact of specific collision avoidance schemes or de-orbit schemes, because the efficiency of a collision avoidance maneuver can depend on various input parameters, including ground station positions and orbital and physical parameters of the objects involved in close encounters (conjunctions). Furthermore, maneuvers take place on timescales much smaller than days. For example, LightForce only changes the orbit of a certain object (aiming to reduce the probability of collision), but it does not remove entire objects or groups of objects. In the same sense, it is also not straightforward to compare specific de-orbit methods in regard to potential collision risks during a de-orbit maneuver. To gain flexibility in assessing interactions with objects, we implement a simulation that includes every tracked space object in Low Earth Orbit (LEO) and propagates all objects with high precision and variable time-steps as small as one second. It allows the assessment of the (potential) impact of physical or orbital changes to any object. The final goal is to employ a Monte Carlo approach to assess the debris evolution during the simulation time-frame of 100 years and to compare a baseline scenario to debris remediation scenarios or other scenarios of interest. To populate the initial simulation, we use the entire space-track object catalog in LEO. We then use a high precision propagator to propagate all objects over the entire simulation duration. If collisions are detected, the appropriate number of debris objects are created and inserted into the simulation framework. Depending on the scenario, further objects, e.g. due to new launches, can be added. At the end of the simulation, the total number of objects above a cut-off size and the number of detected collisions provide benchmark parameters for the comparison between scenarios. The simulation approach is computationally intensive as it involves tens of thousands of objects; hence we use a highly parallel approach employing up to a thousand cores on the NASA Pleiades supercomputer for a single run. This paper describes our simulation approach, the status of its implementation, the approach to developing scenarios and examples of first test runs.

Integrated Vehicle and Trajectory Design of Small Spacecraft with Electric Propulsion for Earth and Interplanetary Missions

NASA Technical Reports Server (NTRS)

Spangelo, Sara; Dalle, Derek; Longmier, Benjamin

2015-01-01

This paper investigates the feasibility of Earth-transfer and interplanetary mission architectures for miniaturized spacecraft using emerging small solar electric propulsion technologies. Emerging small SEP thrusters offer significant advantages relative to existing technologies and will enable U-class systems to perform trajectory maneuvers with significant Delta V requirements. The approach in this paper is unique because it integrates trajectory design with vehicle sizing and accounts for the system and operational constraints of small U-class missions. The modeling framework includes integrated propulsion, orbit, energy, and external environment dynamics and systems-level power, energy, mass, and volume constraints. The trajectory simulation environment models orbit boosts in Earth orbit and flyby and capture trajectories to interplanetary destinations. A family of small spacecraft mission architectures are studied, including altitude and inclination transfers in Earth orbit and trajectories that escape Earth orbit and travel to interplanetary destinations such as Mercury, Venus, and Mars. Results are presented visually to show the trade-offs between competing performance objectives such as maximizing available mass and volume for payloads and minimizing transfer time. The results demonstrate the feasibility of using small spacecraft to perform significant Earth and interplanetary orbit transfers in less than one year with reasonable U-class mass, power, volume, and mission durations.

Low Earth orbit atomic oxygen simulation for durability evaluation of solar reflector surfaces

NASA Technical Reports Server (NTRS)

Degroh, Kim K.; Banks, Bruce A.

1992-01-01

To evaluate the performance and durability of solar reflector surfaces in the atomic oxygen environment typical of low Earth orbit (LEO), one must expose the reflector surface either directly to LEO or to ground-laboratory atomic oxygen environments. Although actual LEO exposures are most desired, such opportunities are typically scarce, expensive, and of limited duration. As a result, ground-laboratory exposures must be relied upon as the most practical long-term durability evaluation technique. Plasma ashers are widely used as LEO simulation facilities by producing atomic oxygen environments for durability evaluation of potential spacecraft materials. Atomic oxygen arrival differs between ground and space exposure in that plasma asher exposure produces isotropic arrival and space solar tracking produces sweeping arrival. Differences in initial impact reaction probability occur, dependent upon the energy and species existing in these environments. Due to the variations in ground-laboratory and space atomic oxygen, quantification of in-space performance based on plasma asher testing is not straightforward. The various atomic oxygen interactions that can occur with reflector surfaces, such as undercutting in organic substrates at protective coating defect sites, ground-laboratory techniques recommended for evaluating the atomic oxygen durability of reflectors based on asher exposures, and computational techniques which make use of ground-laboratory atomic oxygen exposure to predict in-space LEO durability are addressed.

The sensitivity of the ESA DELTA model

NASA Astrophysics Data System (ADS)

Martin, C.; Walker, R.; Klinkrad, H.

Long-term debris environment models play a vital role in furthering our understanding of the future debris environment, and in aiding the determination of a strategy to preserve the Earth orbital environment for future use. By their very nature these models have to make certain assumptions to enable informative future projections to be made. Examples of these assumptions include the projection of future traffic, including launch and explosion rates, and the methodology used to simulate break-up events. To ensure a sound basis for future projections, and consequently for assessing the effectiveness of various mitigation measures, it is essential that the sensitivity of these models to variations in key assumptions is examined. The DELTA (Debris Environment Long Term Analysis) model, developed by QinetiQ for the European Space Agency, allows the future projection of the debris environment throughout Earth orbit. Extensive analyses with this model have been performed under the auspices of the ESA Space Debris Mitigation Handbook and following the recent upgrade of the model to DELTA 3.0. This paper draws on these analyses to present the sensitivity of the DELTA model to changes in key model parameters and assumptions. Specifically the paper will address the variation in future traffic rates, including the deployment of satellite constellations, and the variation in the break-up model and criteria used to simulate future explosion and collision events.

Simulation Based Studies of Low Latency Teleoperations for NASA Exploration Missions

NASA Technical Reports Server (NTRS)

Gernhardt, Michael L.; Crues, Edwin Z.; Bielski, Paul; Dexter, Dan; Litaker, Harry L.; Chappell, Steven P.; Beaton, Kara H.; Bekdash, Omar S.

2017-01-01

Human exploration of Mars will involve both crewed and robotic systems. Many mission concepts involve the deployment and assembly of mission support assets prior to crew arrival on the surface. Some of these deployment and assembly activities will be performed autonomously while others will be performed using teleoperations. However, significant communications latencies between the Earth and Mars make teleoperations challenging. Alternatively, low latency teleoperations are possible from locations in Mars orbit like Mars' moons Phobos and Deimos. To explore these latency opportunities, NASA is conducting a series of studies to investigate the effects of latency on telerobotic deployment and assembly activities. These studies are being conducted in laboratory environments at NASA's Johnson Space Center (JSC), the Human Exploration Research Analog (HERA) at JSC and the NASA Extreme Environment Mission Operations (NEEMO) underwater habitat off the coast of Florida. The studies involve two human-in-the-loop interactive simulations developed by the NASA Exploration Systems Simulations (NExSyS) team at JSC. The first simulation investigates manipulation related activities while the second simulation investigates mobility related activities. The first simulation provides a simple real-time operator interface with displays and controls for a simulated 6 degree of freedom end effector. The initial version of the simulation uses a simple control mode to decouple the robotic kinematic constraints and a communications delay to model latency effects. This provides the basis for early testing with more detailed manipulation simulations planned for the future. Subjects are tested using five operating latencies that represent teleoperation conditions from local surface operations to orbital operations at Phobos, Deimos and ultimately high Martian orbit. Subject performance is measured and correlated with three distance-to-target zones of interest. Each zone represents a target distance ranging from beyond 10m in Zone 1, through 1 cm to contact in Zone 5 with a step size factor of 10. Collected data consists of both objective simulation data (time, distance, hand controller inputs, velocity) and subjective questionnaire data. The second simulation provides a simple real-time operator interface with displays and control of a simulated surface rover. The rover traverses a synthetic Mars-like terrain and must be maneuvered to avoid obstacles while progressing to its destination. Like the manipulator simulation, subjects are tested using five operating latencies that represent teleoperation conditions from local surface operations to orbital operations at Phobos, Deimos and ultimately high Martian orbit. The rover is also operated at three different traverse speeds to assess the correlation between latency and speed. Collected data consisted of both objective simulation data (time, distance, hand controller inputs, braking) and subjective questionnaire data. These studies are exploring relationships between task complexity, operating speeds, operator efficiencies, and communications latencies for low latency teleoperations in support of human planetary exploration. This paper presents early results from these studies along with the current observations and conclusions. These and planned future studies will help to inform NASA on the potential for low latency teleoperations to support human exploration of Mars and inform the design of robotic systems and exploration missions.

Hot planetary winds near a star: dynamics, wind-wind interactions, and observational signatures

NASA Astrophysics Data System (ADS)

Carroll-Nellenback, Jonathan; Frank, Adam; Liu, Baowei; Quillen, Alice C.; Blackman, Eric G.; Dobbs-Dixon, Ian

2017-04-01

Signatures of 'evaporative' winds from exoplanets on short (hot) orbits around their host star have been observed in a number of systems. In this paper, we present global adaptive mesh refinement simulations that track the launching of the winds, their expansion through the circumstellar environment, and their interaction with a stellar wind. We focus on purely hydrodynamic flows including the anisotropy of the wind launching and explore the orbital/fluid dynamics of the resulting flows in detail. In particular, we find that a combination of the tidal and Coriolis forces strongly distorts the planetary 'Parker' wind creating 'up-orbit' and 'down-orbit' streams. We characterize the flows in terms of their orbital elements that change depending on their launch position on the planet. We find that the anisotropy in the atmospheric temperature leads to significant backflow on to the planet. The planetary wind interacts strongly with the stellar wind creating instabilities that may cause eventual deposition of planetary gas on to the star. We present synthetic observations of both transit and absorption line-structure for our simulations. For our initial conditions, we find that the orbiting wind material produces absorption signatures at significant distances from the planet and substantial orbit-to-orbit variability. Lyα absorption shows red- and blueshifted features out to 70 km s-1. Finally, using semi-analytic models we constrain the effect of radiation pressure, given the approximation of uniform stellar absorption.

HABEBEE: habitability of eyeball-exo-Earths.

PubMed

Angerhausen, Daniel; Sapers, Haley; Citron, Robert; Bergantini, Alexandre; Lutz, Stefanie; Queiroz, Luciano Lopes; da Rosa Alexandre, Marcelo; Araujo, Ana Carolina Vieira

2013-03-01

Extrasolar Earth and super-Earth planets orbiting within the habitable zone of M dwarf host stars may play a significant role in the discovery of habitable environments beyond Earth. Spectroscopic characterization of these exoplanets with respect to habitability requires the determination of habitability parameters with respect to remote sensing. The habitable zone of dwarf stars is located in close proximity to the host star, such that exoplanets orbiting within this zone will likely be tidally locked. On terrestrial planets with an icy shell, this may produce a liquid water ocean at the substellar point, one particular "Eyeball Earth" state. In this research proposal, HABEBEE: exploring the HABitability of Eyeball-Exo-Earths, we define the parameters necessary to achieve a stable icy Eyeball Earth capable of supporting life. Astronomical and geochemical research will define parameters needed to simulate potentially habitable environments on an icy Eyeball Earth planet. Biological requirements will be based on detailed studies of microbial communities within Earth analog environments. Using the interdisciplinary results of both the physical and biological teams, we will set up a simulation chamber to expose a cold- and UV-tolerant microbial community to the theoretically derived Eyeball Earth climate states, simulating the composition, atmosphere, physical parameters, and stellar irradiation. Combining the results of both studies will enable us to derive observable parameters as well as target decision guidance and feasibility analysis for upcoming astronomical platforms.

Improving orbit prediction accuracy through supervised machine learning

NASA Astrophysics Data System (ADS)

Peng, Hao; Bai, Xiaoli

2018-05-01

Due to the lack of information such as the space environment condition and resident space objects' (RSOs') body characteristics, current orbit predictions that are solely grounded on physics-based models may fail to achieve required accuracy for collision avoidance and have led to satellite collisions already. This paper presents a methodology to predict RSOs' trajectories with higher accuracy than that of the current methods. Inspired by the machine learning (ML) theory through which the models are learned based on large amounts of observed data and the prediction is conducted without explicitly modeling space objects and space environment, the proposed ML approach integrates physics-based orbit prediction algorithms with a learning-based process that focuses on reducing the prediction errors. Using a simulation-based space catalog environment as the test bed, the paper demonstrates three types of generalization capability for the proposed ML approach: (1) the ML model can be used to improve the same RSO's orbit information that is not available during the learning process but shares the same time interval as the training data; (2) the ML model can be used to improve predictions of the same RSO at future epochs; and (3) the ML model based on a RSO can be applied to other RSOs that share some common features.

SAPT units turn-on in an interference-dominant environment. [Stand Alone Pressure Transducer

NASA Technical Reports Server (NTRS)

Peng, W.-C.; Yang, C.-C.; Lichtenberg, C.

1990-01-01

A stand alone pressure transducer (SAPT) is a credit-card-sized smart pressure sensor inserted between the tile and the aluminum skin of a space shuttle. Reliably initiating the SAPT units via RF signals in a prelaunch environment is a challenging problem. Multiple-source interference may exist if more than one GSE (ground support equipment) antenna is turned on at the same time to meet the simultaneity requirement of 10 ms. A polygon model for orbiter, external tank, solid rocket booster, and tail service masts is used to simulate the prelaunch environment. Geometric optics is then applied to identify the coverage areas and the areas which are vulnerable to multipath and/or multiple-source interference. Simulation results show that the underside areas of an orbiter have incidence angles exceeding 80 deg. For multipath interference, both sides of the cargo bay areas are found to be vulnerable to a worst-case multipath loss exceeding 20 dB. Multiple-source interference areas are also identified. Mitigation methods for the coverage and interference problem are described. It is shown that multiple-source interference can be eliminated (or controlled) using the time-division-multiplexing method or the time-stamp approach.

Skylab

NASA Image and Video Library

1973-05-01

This photograph was taken in the Marshall Space Flight Center (MSFC) Neutral Buoyancy Simulator (NBS) during the testing of an emergency procedure to deploy a twin-pole sunshade to protect the orbiting workshop from overheating due to the loss of its thermal shield. The spacecraft suffered damage to its sunshield during its launch on May 14, 1973. This photograph shows the base plate used to hold the twin-pole in place, the bag to hold the fabric sail, and the lines that were used to draw the sail into place. Extensive testing and many hours of practice in simulators, such as the NBS, helped prepare the Skylab crewmen for extravehicular performance in the weightless environment. This huge water tank simulated the weightless environment that the astronauts would encounter in space.

STS-55 MS3 Harris, wearing EMU and CCA, prepares for EVA simulation at JSC WETF

NASA Technical Reports Server (NTRS)

1991-01-01

STS-55 Columbia, Orbiter Vehicle (OV) 102, Mission Specialist 3 (MS3) Bernard A. Harris, Jr, suited in the extravehicular mobility unit (EMU) upper torso and communications carrier assembly (CCA), smiles as he prepares for an underwater simulation in JSC's Weightless Environment Training Facility (WETF) Bldg 29 pool. This portrait-like view captures Harris as he checks out his communications equipment. Once fully suited, Harris will be lowered into the WETF's 25-foot deep pool for an underwater contingency extravehicular activity (EVA) simulation. There is no scheduled EVA for the 1993 flight but each spaceflight crew includes astronauts trained for a variety of contingency tasks that could require exiting the shirt-sleeve environment of a Shuttle's cabin.

KSC-04PD-0245

NASA Technical Reports Server (NTRS)

2004-01-01

KENNEDY SPACE CENTER, FLA. In the Launch Control Center, officials monitor the Mode VII emergency landing simulation being conducted at Kennedy Space Center and managed and directed from the LCC. From left are Dr. Luis Moreno and Dr. David Reed, with Bionetics Life Sciences, and Dr. Philip Scarpa, with the KSC Safety, Occupational Health and Environment Division. The purpose of the Mode VII is to exercise emergency preparedness personnel, equipment and facilities in rescuing astronauts from a downed orbiter and providing immediate medical attention. This simulation presents an orbiter that has crashed short of the Shuttle Landing Facility in a wooded area 2-1/2 miles south of Runway 33. Emergency crews are responding to the volunteer astronauts who are simulating various injuries inside the crew compartment mock-up. Rescuers must remove the crew, provide triage and transport to hospitals those who need further treatment. Local hospitals are participating in the exercise.

An analysis of the low-earth-orbit communications environment

NASA Astrophysics Data System (ADS)

Diersing, Robert Joseph

Advances in microprocessor technology and availability of launch opportunities have caused interest in low-earth-orbit satellite based communications systems to increase dramatically during the past several years. In this research the capabilities of two low-cost, store-and-forward LEO communications satellites operating in the public domain are examined--PACSAT-1 (operated by the Radio Amateur Satellite Corporation) and UoSAT-3 (operated by the University of Surrey, England, Electrical Engineering Department). The file broadcasting and file transfer facilities are examined in detail and a simulation model of the downlink traffic pattern is developed. The simulator will aid the assessment of changes in design and implementation for other systems. The development of the downlink traffic simulator is based on three major parts. First, is a characterization of the low-earth-orbit operating environment along with preliminary measurements of the PACSAT-1 and UoSAT-3 systems including: satellite visibility constraints on communications, monitoring equipment configuration, link margin computations, determination of block and bit error rates, and establishing typical data capture rates for ground stations using computer-pointed directional antennas and fixed omni-directional antennas. Second, arrival rates for successful and unsuccessful file server connections are established along with transaction service times. Downlink traffic has been further characterized by measuring: frame and byte counts for all data-link layer traffic; 30-second interval average response time for all traffic and for file server traffic only; file server response time on a per-connection basis; and retry rates for information and supervisory frames. Finally, the model is verified by comparison with measurements of actual traffic not previously used in the model building process. The simulator is then used to predict operation of the PACSAT-1 satellite with modifications to the original design.

Theoretical and experimental studies relevant to interpretation of auroral emissions

NASA Technical Reports Server (NTRS)

Keffer, Charles E.

1994-01-01

This report describes the accomplishments of a program designed to develop the tools necessary to interpret auroral emissions measured from a space-based platform. The research was divided into two major areas. The first area was a laboratory study designed to improve our understanding of the space vehicle external environment and how it will affect the space-based measurement of auroral emissions. Facilities have been setup and measurements taken to simulate the gas phase environment around a space vehicle; the radiation environment encountered by an orbiting vehicle that passes through the Earth's radiation belts; and the thermal environment of a vehicle in Earth orbit. The second major area of study was a modeling program to develop the capability of using auroral images at various wavelengths to infer the total energy influx and characteristic energy of the incident auroral particles. An ab initio auroral calculation has been added to the extant ionospheric/thermospheric global modeling capabilities within our group. Once the addition of the code was complete, the combined model was used to compare the relative intensities and behavior of various emission sources (dayglow, aurora, etc.). Attached papers included are: 'Laboratory Facility for Simulation of Vehicle-Environment Interactions'; 'Workshop on the Induced Environment of Space Station Freedom'; 'Radiation Damage Effects in Far Ultraviolet Filters and Substrates'; 'Radiation Damage Effects in Far Ultraviolet Filters, Thin Films, and Substrates'; 'Use of FUV Auroral Emissions as Diagnostic Indicators'; and 'Determination of Ionospheric Conductivities from FUV Auroral Emissions'.

Full-size solar dynamic heat receiver thermal-vacuum tests

NASA Technical Reports Server (NTRS)

Sedgwick, L. M.; Kaufmann, K. J.; Mclallin, K. L.; Kerslake, Thomas W.

1991-01-01

The testing of a full-size, 120 kW, solar dynamic heat receiver utilizing high-temperature thermal energy storage is described. The purpose of the test program was to quantify receiver thermodynamic performance, operating temperatures, and thermal response to changes in environmental and power module interface boundary conditions. The heat receiver was tested in a vacuum chamber with liquid nitrogen cold shrouds and an aperture cold plate to partly simulate a low-Earth-orbit environment. The cavity of the receiver was heated by an infrared quartz lamp heater with 30 independently controllable zones to allow axially and circumferentially varied flux distributions. A closed-Brayton cycle engine simulator conditioned a helium-xenon gas mixture to specific interface conditions to simulate the various operational modes of the solar dynamic power module on the Space Station Freedom. Inlet gas temperature, pressure, and flow rate were independently varied. A total of 58 simulated orbital cycles, each 94 minutes in duration, was completed during the test conduct period.

Full-size solar dynamic heat receiver thermal-vacuum tests

NASA Technical Reports Server (NTRS)

Sedgwick, L. M.; Kaufmann, K. J.; Mclallin, K. L.; Kerslake, T. W.

1991-01-01

The testing of a full-size, 102 kW, solar dynamic heat receiver utilizing high-temperature thermal energy storage is described. The purpose of the test program was to quantify receiver thermodynamic performance, operating temperatures, and thermal response to changes in environmental and power module interface boundary conditions. The heat receiver was tested in a vacuum chamber with liquid nitrogen cold shrouds and an aperture cold plate to partly simulate a low-Earth-orbit environment. The cavity of the receiver was heated by an infrared quartz lamp heater with 30 independently controllable zones to allow axially and circumferentially varied flux distributions. A closed-Brayton cycle engine simulator conditioned a helium-xenon gas mixture to specific interface conditions to simulate the various operational modes of the solar dynamic power module on the Space Station Freedom. Inlet gas temperature, pressure, and flow rate were independently varied. A total of 58 simulated orbital cycles, each 94 minutes in duration, was completed during the test period.

Full-size solar dynamic heat receiver thermal-vacuum tests

NASA Astrophysics Data System (ADS)

Sedgwick, L. M.; Kaufmann, K. J.; McLallin, K. L.; Kerslake, T. W.

The testing of a full-size, 102 kW, solar dynamic heat receiver utilizing high-temperature thermal energy storage is described. The purpose of the test program was to quantify receiver thermodynamic performance, operating temperatures, and thermal response to changes in environmental and power module interface boundary conditions. The heat receiver was tested in a vacuum chamber with liquid nitrogen cold shrouds and an aperture cold plate to partly simulate a low-Earth-orbit environment. The cavity of the receiver was heated by an infrared quartz lamp heater with 30 independently controllable zones to allow axially and circumferentially varied flux distributions. A closed-Brayton cycle engine simulator conditioned a helium-xenon gas mixture to specific interface conditions to simulate the various operational modes of the solar dynamic power module on the Space Station Freedom. Inlet gas temperature, pressure, and flow rate were independently varied. A total of 58 simulated orbital cycles, each 94 minutes in duration, was completed during the test period.

SURVIAC Bulletin: AFRL Research Audit Trail Viewer (ATV). Volume 19, Issue 1, 2003

DTIC Science & Technology

2003-01-01

Trail Viewer, the analyst obtained a close up view of the detailed aircraft model using the Orbit View, enabled the SkyBox , enabled fictional ter...trails and element projections, several simulated terrain types and Skybox environments to help the user maintain perspective, file based

Flight Experiment Demonstration System (FEDS) analysis report

NASA Technical Reports Server (NTRS)

Shank, D. E.

1986-01-01

The purpose of the Flight Experiment Demonstration System (FEDS) was to show, in a simulated spacecraft environment, the feasibility of using a microprocessor to automate the onboard orbit determination functions. The software and hardware configuration used to support FEDS during the demonstration and the results of the demonstration are discussed.

Direct simulation Monte Carlo prediction of on-orbit contaminant deposit levels for HALOE

NASA Technical Reports Server (NTRS)

Woronowicz, Michael S.; Rault, Didier F. G.

1994-01-01

A three-dimensional version of the direct simulation Monte Carlo method is adapted to assess the contamination environment surrounding a highly detailed model of the Upper Atmosphere Research Satellite. Emphasis is placed on simulating a realistic, worst-case set of flow field and surface conditions and geometric orientations for the satellite in order to estimate an upper limit for the cumulative level of volatile organic molecular deposits at the aperture of the Halogen Occultation Experiment. A detailed description of the adaptation of this solution method to the study of the satellite's environment is also presented. Results pertaining to the satellite's environment are presented regarding contaminant cloud structure, cloud composition, and statistics of simulated molecules impinging on the target surface, along with data related to code performance. Using procedures developed in standard contamination analyses, along with many worst-case assumptions, the cumulative upper-limit level of volatile organic deposits on HALOE's aperture over the instrument's 35-month nominal data collection period is estimated at about 13,350 A.

Radiation Protection Effectiveness of Polymeric Based Shielding Materials at Low Earth Orbit

NASA Technical Reports Server (NTRS)

Badavi, Francis F.; Stewart-Sloan, Charlotte R.; Wilson, John W.; Adams, Daniel O.

2008-01-01

Correlations of limited ionizing radiation measurements onboard the Space Transportation System (STS; shuttle) and the International Space Station (ISS) with numerical simulations of charged particle transport through spacecraft structure have indicated that usage of hydrogen rich polymeric materials improves the radiation shielding performance of space structures as compared to the traditionally used aluminum alloys. We discuss herein the radiation shielding correlations between measurements on board STS-81 (Atlantis, 1997) using four polyethylene (PE) spheres of varying radii, and STS-89 (Endeavour, 1998) using aluminum alloy spheres; with numerical simulations of charged particle transport using the Langley Research Center (LaRC)-developed High charge (Z) and Energy TRaNsport (HZETRN) algorithm. In the simulations, the Galactic Cosmic Ray (GCR) component of the ionizing radiation environment at Low Earth Orbit (LEO) covering ions in the 1< or equals Z< or equals 28 range is represented by O'Neill's (2004) model. To compute the transmission coefficient for GCR ions at LEO, O'Neill's model is coupled with the angular dependent LaRC cutoff model. The trapped protons/electrons component of LEO environment is represented by a LaRC-developed time dependent procedure which couples the AP8min/AP8max, Deep River Neutron Monitor (DRNM) and F10.7 solar radio frequency measurements. The albedo neutron environment resulting from interaction of GCR ions with upper atmosphere is modeled through extrapolation of the Atmospheric Ionizing Radiation (AIR) measurements. With the validity of numerical simulations through correlation with PE and aluminum spheres measurements established, we further present results from the expansion of the simulations through the selection of high hydrogen content commercially available polymeric constituents such as PE foam core and Spectra fiber(Registered TradeMark) composite face sheet to assess their radiation shield properties as compared to generic PE.

The Organism/Organic Exposure to Orbital Stresses (O/OREOS) satellite: radiation exposure in low-earth orbit and supporting laboratory studies of iron tetraphenylporphyrin chloride.

PubMed

Cook, Amanda M; Mattioda, Andrew L; Ricco, Antonio J; Quinn, Richard C; Elsaesser, Andreas; Ehrenfreund, Pascale; Ricca, Alessandra; Jones, Nykola C; Hoffmann, Søren V

2014-02-01

We report results from the exposure of the metalloporphyrin iron tetraphenylporphyrin chloride (FeTPPCl) to the outer space environment, measured in situ aboard the Organism/Organic Exposure to Orbital Stresses nanosatellite. FeTPPCl was exposed for a period of 17 months (3700 h of direct solar exposure), which included broad-spectrum solar radiation (∼122 nm to the near infrared). Motivated by the potential role of metalloporphyrins as molecular biomarkers, the exposure of thin-film samples of FeTPPCl to the space environment in low-Earth orbit was monitored in situ via ultraviolet/visible spectroscopy and reported telemetrically. The space data were complemented by laboratory exposure experiments that used a high-fidelity solar simulator covering the spectral range of the spaceflight measurements. We found that thin-film samples of FeTPPCl that were in contact with a humid headspace gas (0.8-2.3% relative humidity) were particularly susceptible to destruction upon irradiation, degrading up to 10 times faster than identical thin films in contact with dry headspace gases; this degradation may also be related to the presence of oxides of nitrogen in those cells. In the companion terrestrial experiments, simulated solar exposure of FeTPPCl films in contact with either Ar or CO2:O2:Ar (10:0.01:1000) headspace gas resulted in growth of a band in the films' infrared spectra at 1961 cm(-1). We concluded that the most likely carriers of this band are allene (C3H4) and chloropropadiene (C3H3Cl), putative molecular fragments of the destruction of the porphyrin ring. The thin films studied in space and in solar simulator-based experiments show qualitatively similar spectral evolution as a function of contacting gaseous species but display significant differences in the time dependence of those changes. The relevance of our findings to planetary science, biomarker research, and the photostability of organic materials in astrobiologically relevant environments is discussed.

Simulation of the synergistic low Earth orbit effects of vacuum thermal cycling, vacuum UV radiation, and atomic oxygen

NASA Technical Reports Server (NTRS)

Dever, Joyce A.; Degroh, Kim K.; Stidham, Curtis R.; Stueber, Thomas J.; Dever, Therese M.; Rodriguez, Elvin; Terlep, Judith A.

1992-01-01

In order to assess the low Earth orbit (LEO) durability of candidate space materials, it is necessary to use ground laboratory facilities which provide LEO environmental effects. A facility combining vacuum thermal cycling and vacuum ultraviolet (VUV) radiation has been designed and constructed at NASA Lewis Research Center for this purpose. This facility can also be operated without the VUV lamps. An additional facility can be used to provide VUV exposure only. By utilizing these facilities, followed by atomic oxygen exposure in an RF plasma asher, the effects of the individual vacuum thermal cycling and VUV environments can be compared to the effect of the combined vacuum thermal cycling/VUV environment on the atomic oxygen durability of materials. The synergistic effects of simulated LEO environmental conditions on materials were evaluated by first exposing materials to vacuum thermal cycling, VUV, and vacuum thermal cycling/VUV environments followed by exposure to atomic oxygen in an RP plasma asher. Candidate space power materials such as atomic oxygen protected polyimides and solar concentrator mirrors were evaluated using these facilities. Characteristics of the Vacuum Thermal Cycling/VUV Exposure Facility which simulates the temperature sequences and solar ultraviolet radiation exposure that would be experienced by a spacecraft surface in LEO are discussed. Results of durability evaluations of some candidate space power materials to the simulated LEO environmental conditions will also be discussed. Such results have indicated that for some materials, atomic oxygen durability is affected by previous exposure to thermal cycling and/or VUV exposure.

Tidal dwarf galaxies in cosmological simulations

NASA Astrophysics Data System (ADS)

Ploeckinger, Sylvia; Sharma, Kuldeep; Schaye, Joop; Crain, Robert A.; Schaller, Matthieu; Barber, Christopher

2018-02-01

The formation and evolution of gravitationally bound, star forming substructures in tidal tails of interacting galaxies, called tidal dwarf galaxies (TDG), has been studied, until now, only in idealized simulations of individual pairs of interacting galaxies for pre-determined orbits, mass ratios and gas fractions. Here, we present the first identification of TDG candidates in fully cosmological simulations, specifically the high-resolution simulations of the EAGLE suite. The finite resolution of the simulation limits their ability to predict the exact formation rate and survival time-scale of TDGs, but we show that gravitationally bound baryonic structures in tidal arms already form in current state-of-the-art cosmological simulations. In this case, the orbital parameter, disc orientations as well as stellar and gas masses and the specific angular momentum of the TDG forming galaxies are a direct consequence of cosmic structure formation. We identify TDG candidates in a wide range of environments, such as multiple galaxy mergers, clumpy high-redshift (up to z = 2) galaxies, high-speed encounters and tidal interactions with gas-poor galaxies. We present selection methods, the properties of the identified TDG candidates and a road map for more quantitative analyses using future high-resolution simulations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nelson, Andrew F.; Marzari, F., E-mail: andy.nelson@lanl.gov, E-mail: francesco.marzari@pd.infn.it

We present two-dimensional hydrodynamic simulations using the Smoothed Particle Hydrodynamic code, VINE, to model a self-gravitating binary system. We model configurations in which a circumbinary torus+disk surrounds a pair of stars in orbit around each other and a circumstellar disk surrounds each star, similar to that observed for the GG Tau A system. We assume that the disks cool as blackbodies, using rates determined independently at each location in the disk by the time dependent temperature of the photosphere there. We assume heating due to hydrodynamical processes and to radiation from the two stars, using rates approximated from a measuremore » of the radiation intercepted by the disk at its photosphere. We simulate a suite of systems configured with semimajor axes of either a = 62 AU (“wide”) or a = 32 AU (“close”), and with assumed orbital eccentricity of either e = 0 or e = 0.3. Each simulation follows the evolution for ∼6500–7500 yr, corresponding to about three orbits of the torus around the center of mass. Our simulations show that strong, sharply defined spiral structures are generated from the stirring action of the binary and that, in some cases, these structures fragment into 1–2 massive clumps. The torus quickly fragments into several dozen such fragments in configurations in which either the binary is replaced by a single star of equal mass, or radiative heating is neglected. The spiral structures extend inwards to the circumstellar environment as large scale material streams for which most material is found on trajectories that return it to the torus on a timescale of 1–200 yr, with only a small fraction accreting into the circumstellar environment. The spiral structures also propagate outwards through the torus, generating net outwards mass flow, and eventually losing coherence at large distances from the stars. The torus becomes significantly eccentric in shape over most of its evolution. In all configurations, accretion onto the stars occurs at a steady rate of a few ×10{sup −8} M {sub ⊙} yr{sup −1}, with the net result that, without replenishment, the disk lifetimes would be shorter than ∼10{sup 4} yr. Our simulations show that only wide orbit configurations are able to retain circumstellar disks, by virtue of accretion driven from the robust material streams generated in wide configurations, which are very weak in close configurations. In wide, eccentric orbit configurations, accretion is episodic and occurs preferentially onto the secondary, with rates strongly peaked near the binary periapse. Based on our results, we conclude that the GG Tau A torus is strongly self gravitating and that a major contribution to its thermal energy input is the shock dissipation associated with spiral structures generated both by self gravitating disturbances and by the stirring action of the binary. We interpret the sharply defined features observed in the torus as manifestations of such spiral structures. We interpret the low density disk surrounding it as an excretion disk created by the outward mass flux generated by the spiral arms as they propagate outwards. Typical eccentricities calculated for the shape of the tori modeled in our simulations are large enough to account for the supposed ∼20° mutual inclination between the stellar orbit plane of GG Tau A and its surrounding torus through a degeneracy between the interpretation of inclination of the torus and its eccentricity. We therefore interpret the observations in favor of a coplanar system with an eccentric torus. Because accretion onto the disks occurs at rates sufficient to sustain them only in wide orbit configurations, we conclude that the gas currently resident in the circumstellar disks of the GG Tau A system has been accreted from the torus within the past few thousand years. Although circumstellar disks will persist over time spans long enough to permit planet formation, the overall environment remains unfavorable due to high temperatures and other conditions. Given the presence of circumstellar disks, robust accretion streams, and our interpretation of the GG Tau A stellar orbit plane as coplanar with the torus surrounding it, we conclude that the GG Tau A system is in an eccentric, a ∼ 62 AU orbit, resolving questions in the literature regarding its orbit parameters.« less

GRACE Mission Design: Impact of Uncertainties in Disturbance Environment and Satellite Force Models

NASA Technical Reports Server (NTRS)

Mazanek, Daniel D.; Kumar, Renjith R.; Seywald, Hans; Qu, Min

2000-01-01

The Gravity Recovery and Climate Experiment (GRACE) primary mission will be performed by making measurements of the inter-satellite range change between two co-planar, low altitude, near-polar orbiting satellites. Understanding the uncertainties in the disturbance environment, particularly the aerodynamic drag and torques, is critical in several mission areas. These include an accurate estimate of the spacecraft orbital lifetime, evaluation of spacecraft attitude control requirements, and estimation of the orbital maintenance maneuver frequency necessitated by differences in the drag forces acting on both satellites. The FREEMOL simulation software has been developed and utilized to analyze and suggest design modifications to the GRACE spacecraft. Aerodynamic accommodation bounding analyses were performed and worst-case envelopes were obtained for the aerodynamic torques and the differential ballistic coefficients between the leading and trailing GRACE spacecraft. These analyses demonstrate how spacecraft aerodynamic design and analysis can benefit from a better understanding of spacecraft surface accommodation properties, and the implications for mission design constraints such as formation spacing control.

Electrostatic Discharge Test of Multi-Junction Solar Array Coupons After Combined Space Environmental Exposures

NASA Technical Reports Server (NTRS)

Wright, Kenneth H.; Schneider, Todd; Vaughn, Jason; Hoang, Bao; Funderburk, Victor V.; Wong, Frankie; Gardiner, George

2010-01-01

A set of multi-junction GaAs/Ge solar array test coupons were subjected to a sequence of 5-year increments of combined environmental exposure tests. The test coupons capture an integrated design intended for use in a geosynchronous (GEO) space environment. A key component of this test campaign is conducting electrostatic discharge (ESD) tests in the inverted gradient mode. The protocol of the ESD tests is based on the ISO/CD 11221, the ISO standard for ESD testing on solar array panels. This standard is currently in its final review with expected approval in 2010. The test schematic in the ISO reference has been modified with Space System/Loral designed circuitry to better simulate the on-orbit operational conditions of its solar array design. Part of the modified circuitry is to simulate a solar array panel coverglass flashover discharge. All solar array coupons used in the test campaign consist of 4 cells. The ESD tests are performed at the beginning of life (BOL) and at each 5-year environment exposure point. The environmental exposure sequence consists of UV radiation, electron/proton particle radiation, thermal cycling, and ion thruster plume. This paper discusses the coverglass flashover simulation, ESD test setup, and the importance of the electrical test design in simulating the on-orbit operational conditions. Results from 5th-year testing are compared to the baseline ESD characteristics determined at the BOL condition.

User modeling techniques for enhanced usability of OPSMODEL operations simulation software

NASA Technical Reports Server (NTRS)

Davis, William T.

1991-01-01

The PC based OPSMODEL operations software for modeling and simulation of space station crew activities supports engineering and cost analyses and operations planning. Using top-down modeling, the level of detail required in the data base can be limited to being commensurate with the results required of any particular analysis. To perform a simulation, a resource environment consisting of locations, crew definition, equipment, and consumables is first defined. Activities to be simulated are then defined as operations and scheduled as desired. These operations are defined within a 1000 level priority structure. The simulation on OPSMODEL, then, consists of the following: user defined, user scheduled operations executing within an environment of user defined resource and priority constraints. Techniques for prioritizing operations to realistically model a representative daily scenario of on-orbit space station crew activities are discussed. The large number of priority levels allows priorities to be assigned commensurate with the detail necessary for a given simulation. Several techniques for realistic modeling of day-to-day work carryover are also addressed.

Development of a Real Time Internal Charging Tool for Geosynchronous Orbit

NASA Technical Reports Server (NTRS)

Posey, Nathaniel A.; Minow, Joesph I.

2013-01-01

The high-energy electron fluxes encountered by satellites in geosynchronous orbit pose a serious threat to onboard instrumentation and other circuitry. A substantial build-up of charge within a satellite's insulators can lead to electric fields in excess of the breakdown strength, which can result in destructive electrostatic discharges. The software tool we've developed uses data on the plasma environment taken from NOAA's GOES-13 satellite to track the resulting electric field strength within a material of arbitrary depth and conductivity and allows us to monitor the risk of material failure in real time. The tool also utilizes a transport algorithm to simulate the effects of shielding on the dielectric. Data on the plasma environment and the resulting electric fields are logged to allow for playback at a variable frame rate.

Orbiter lessons learned: A guide to future vehicle development

NASA Technical Reports Server (NTRS)

Greenberg, Harry Stan

1993-01-01

Topics addressed are: (1) wind persistence loads methodology; (2) emphasize supportability in design of reusable vehicles; (3) design for robustness; (4) improved aerodynamic environment prediction methods for complex vehicles; (5) automated integration of aerothermal, manufacturing, and structures analysis; (6) continued electronic documentation of structural design and analysis; and (7) landing gear rollout load simulations.

Simulation of Attitude and Trajectory Dynamics and Control of Multiple Spacecraft

NASA Technical Reports Server (NTRS)

Stoneking, Eric T.

2009-01-01

Agora software is a simulation of spacecraft attitude and orbit dynamics. It supports spacecraft models composed of multiple rigid bodies or flexible structural models. Agora simulates multiple spacecraft simultaneously, supporting rendezvous, proximity operations, and precision formation flying studies. The Agora environment includes ephemerides for all planets and major moons in the solar system, supporting design studies for deep space as well as geocentric missions. The environment also contains standard models for gravity, atmospheric density, and magnetic fields. Disturbance force and torque models include aerodynamic, gravity-gradient, solar radiation pressure, and third-body gravitation. In addition to the dynamic and environmental models, Agora supports geometrical visualization through an OpenGL interface. Prototype models are provided for common sensors, actuators, and control laws. A clean interface accommodates linking in actual flight code in place of the prototype control laws. The same simulation may be used for rapid feasibility studies, and then used for flight software validation as the design matures. Agora is open-source and portable across computing platforms, making it customizable and extensible. It is written to support the entire GNC (guidance, navigation, and control) design cycle, from rapid prototyping and design analysis, to high-fidelity flight code verification. As a top-down design, Agora is intended to accommodate a large range of missions, anywhere in the solar system. Both two-body and three-body flight regimes are supported, as well as seamless transition between them. Multiple spacecraft may be simultaneously simulated, enabling simulation of rendezvous scenarios, as well as formation flying. Built-in reference frames and orbit perturbation dynamics provide accurate modeling of precision formation control.

Atomic research

NASA Technical Reports Server (NTRS)

Hadaway, James B.; Connatser, Robert; Cothren, Bobby; Johnson, R. B.

1993-01-01

Work performed by the University of Alabama in Huntsville's (UAH) Center for Applied Optics (CAO) entitled Atomic Research is documented. Atomic oxygen (AO) effects on materials have long been a critical concern in designing spacecraft to withstand exposure to the Low Earth Orbit (LEO) environment. The objective of this research effort was to provide technical expertise in the design of instrumentation and experimental techniques for analyzing materials exposed to atomic oxygen in accelerated testing at NASA/MSFC. Such testing was required to answer fundamental questions concerning Space Station Freedom (SSF) candidate materials and materials exposed to atomic oxygen aboard the Long-Duration Exposure Facility (LDEF). The primary UAH task was to provide technical design, review, and analysis to MSFC in the development of a state-of-the-art 5eV atomic oxygen beam facility required to simulate the RAM-induced low earth orbit (LEO) AO environment. This development was to be accomplished primarily at NASA/MSFC. In support of this task, contamination effects and ultraviolet (UV) simulation testing was also to be carried out using NASA/MSFC facilities. Any materials analysis of LDEF samples was to be accomplished at UAH.

Smart active pilot-in-the-loop systems

NASA Astrophysics Data System (ADS)

Thomas, Segun

1995-04-01

Representation of on-orbit microgravity environment in a 1-g environment is a continuing problem in space engineering analysis, procedures development and crew training. A way of adequately depicting weightlessness in the performance of on-orbit tasks is by a realistic (or real-time) computer based representation that provides the look, touch, and feel of on-orbit operation. This paper describes how a facility, the Systems Engineering Simulator at the Johnson Space Center, is utilizing recent advances in computer processing power and multi- processing capability to intelligently represent all systems, sub-systems and environmental elements associated with space flight operations. It first describes the computer hardware and interconnection between processors; the computer software responsible for task scheduling, health monitoring, sub-system and environment representation; control room and crew station. It then describes, the mathematical models that represent the dynamics of contact between the Mir and the Space Shuttle during the upcoming US and Russian Shuttle/Mir space mission. Results are presented comparing the response of the smart, active pilot-in-the-loop system to non-time critical CRAY model. A final example of how these systems are utilized is given in the development that supported the highly successful Hubble Space Telescope repair mission.

Flight test of a synthetic aperture radar antenna using STEP

NASA Technical Reports Server (NTRS)

Zimcik, D. G.; Vigeron, F. R.; Ahmed, S.

1984-01-01

To establish confidence in its overall performance, credible information on the synthetic aperture radar antenna's mechanical properties in orbit must be obtained. However, the antenna's size, design, and operating environment make it difficult to simulate operating conditions under 1-g Earth conditions. The Space Technology Experiments Platform (STEP) offers a timely opportunity to mechanically qualify and characterize the antenna design in a representative environment. The proposed experimental configuration would employ a half-system of the full-scale RADARSAT antenna which would be mounted on the STEP platform in the orbiter cargo bay such that it could be deployed and retracted in orbit (as shown in this figure). The antenna would be subjected to typical environmental exposures while an array of targets and sensors on the antenna support structure and reflecting surface are observed and monitored. In particular, the typical environments would include deployment and retraction, dynamic response to vehicle thruster or base exciter inputs, and thermal soak and transient effects upon entering or exiting Earth eclipse. The proposed experiment would also provide generic information on the properties of large space structures in space and on techniques to obtain the desired information.

The development and testing of the fast imaging plasma spectrometer and its application in the plasma environment at Mercury

NASA Astrophysics Data System (ADS)

Koehn, Patrick Leo

The plasma environment at Mercury is a rich laboratory for studying the interaction of the solar wind with a planet. Three primary populations of ions exist at Mercury: solar wind, magnetospheric particles, and pickup ions. Pickup ions are generated through the ionization of Mercury's exosphere or are sputtered particles from the Mercury surface. A comprehensive mission to Mercury should include a sensor that is able to determine the dynamical properties and composition of all three plasma components. The Fast Imaging Plasma Spectrometer (FIPS) is an instrument to measure the composition of these ion populations and their three-dimensional velocity distribution functions. It is lightweight, fast, and has a very large field of view, and these properties made possible its accommodation within the highly mass- constrained payload of MESSENGER (MErcury: Surface, Space ENvironment, GEochemistry, Ranging) mission, a Mercury orbiter. This work details the development cycle of FIPS, from concept to prototype testing. It begins with science studies of the magnetospheric and pickup ion environments of Mercury, using state-of-the-art computer simulations to produce static and quasi-dynamic magnetospheric systems. Predictions are made of the spatially variable plasma environment at Mercury, and the temporally varying magnetosphere-solar wind interaction is examined. Pickup ion studies provide insights to particle loss mechanisms and the nature of the radar-bright regions at the Hermean poles. These studies produce science requirements for successfully measuring this environment with an orbiting mass spectrometer. With these science requirements in mind, a concept for a new electrostatic analyzer is created. This concept is considered from a theoretical standpoint, and compared with other, similarly performing instruments, both of the past and currently in use. The development cycle continues with instrument simulation, which allows the design to be adjusted to fit within the science requirements of the mission. Finally, a prototype electrostatic is constructed and tested in a space- simulating vacuum chamber system. The results of these tests are compared with the simulation results, and ultimately shown to fit within the science requirements for the MESSENGER mission.

Advanced development receiver thermal vacuum tests with cold wall

NASA Technical Reports Server (NTRS)

Sedgwick, Leigh M.

1991-01-01

The first ever testing of a full size solar dynamic heat receiver using high temperature thermal energy storage was completed. The heat receiver was designed to meet the requirements for operation on the Space Station Freedom. The purpose of the test program was to quantify the receiver thermodynamic performance, its operating temperatures, and thermal response to changes in environmental and power module interface boundary conditions. The heat receiver was tested in a vacuum chamber with liquid nitrogen cold shrouds and an aperture cold plate to partially simulate a low Earth orbit environment. The cavity of the receiver was heated by an infrared quartz lamp heater with 30 independently controllable zones to produce flux distributions typical of candidate concentrators. A closed Brayton cycle engine simulator conditioned a helium xenon gas mixture to specific interface conditions to simulate various operational modes of the solar dynamic power module. Inlet gas temperature, pressure, and flow rate were independently varied. A total of 58 simulated orbital cycles were completed during the test conduct period. The test hardware, execution of testing, test data, and post test inspections are described.

Sheath effects observed on a 10 meter high voltage panel in simulated low earth orbit plasma

NASA Technical Reports Server (NTRS)

Mccox, J. E.; Konradi, A.

1979-01-01

A large (1m x 10m) flat surface of conductive material was biased to high voltage (+ or - 3000 V) to simulate the behavior of a large solar array in low earth orbit. The model array was operated in a plasma environment of 1,000 to 1,000,000/cu cm, with sufficient free space around it for the resulting plasma sheaths to develop unimpeded for 5-10 meters into the surrounding plasma. Measurements of the resulting sheath thickness were obtained. The observed thickness varied approximately as V to the 3/4 power and N to the 1/2 power. This effect appears to limit total current leakage from the test array until sheath dimensions exceed about 1 meter. Total leakage current was also measured with the array.

Numerical Relativity Simulations of Compact Binary Populations in Dense Stellar Environments

NASA Astrophysics Data System (ADS)

Glennon, Derek Ray; Huerta, Eliu; Allen, Gabrielle; Haas, Roland; Seidel, Edward; NCSA Gravity Group

2018-01-01

We present a catalog of numerical relativity simulations that describe binary black hole mergers on eccentric orbits. These simulations have been obtained with the open source, Einstein Toolkit numerical relativity software, using the Blue Waters supercomputer. We use this catalog to quantify observables, such as the mass and spin of black holes formed by binary black hole mergers, as a function of eccentricity. This study is the first of its kind in the literature to quantify these astrophysical observables for binary black hole mergers with mass-ratios q<6, and eccentricities e<0.2. This study is an important step in understanding the properties of eccentric binary black hole mergers, and informs the use of gravitational wave observations to confirm or rule out the existence of compact binary populations in dense stellar environments.

Emboldened by Embodiment: Six Precepts for Research on Embodied Learning and Mixed Reality

ERIC Educational Resources Information Center

Lindgren, Robb; Johnson-Glenberg, Mina

2013-01-01

The authors describe an emerging paradigm of educational research that pairs theories of embodied learning with a class of immersive technologies referred to as "mixed reality" (MR). MR environments merge the digital with the physical, where, for example, students can use their bodies to simulate an orbit around a virtual planet. Recent…

STS-53 MS Clifford, in EMU, dons gloves with technicians' assistance at JSC

NASA Technical Reports Server (NTRS)

1992-01-01

STS-53 Discovery, Orbiter Vehicle (OV) 103, Mission Specialist (MS) Michael R.U. Clifford, wearing extravehicular mobility unit (EMU) and communications carrier assembly (CCA), dons gloves with assistance from two technicians. Clifford is preparing for an underwater contingency extravehicular activity (EVA) simulation in JSC's Weightless Environment Training Facility (WETF) Bldg 29 pool.

STS-53 MS Voss,in EMU, dons gloves with technicians' assistance at JSC's WETF

NASA Technical Reports Server (NTRS)

1992-01-01

STS-53 Discovery, Orbiter Vehicle (OV) 103, Mission Specialist (MS) James S. Voss, wearing extravehicular mobility unit (EMU) and communications carrier assembly (CCA), dons his gloves with assistance from two technicians. Voss is preparing for an underwater contingency extravehicular activity (EVA) simulation in JSC's Weightless Environment Training Facility (WETF) Bldg 29 pool.

Numerical simulation of Ganymede's ionosphere

NASA Astrophysics Data System (ADS)

Carnielli, Gianluca; Galand, Marina; Leblanc, François; Leclercq, Ludivine; Modolo, Ronan

2017-04-01

Ganymede is one of the four Galilean moons that orbit around Jupiter and the key moon targeted by the JUpiter and ICy moons Explorer (JUICE) mission. Other than being the largest moon in the solar system, it is also the only one known to generate internally a magnetic field which is strong enough to overcome the background jovian field; thus, the moon carves out its own magnetosphere inside that of Jupiter. In addition, at Ganymede's orbit the jovian plasma is sub-Alfvénic and subsonic. The interaction of Ganymede's magnetosphere with its surroundings therefore differs from that of planetary magnetospheres resulting from the interaction with the super-Alfvénic and supersonic solar wind. All this makes Ganymede a peculiar celestial body to study. One of the main goals of the JUICE mission is to characterize Ganymede's exosphere, ionosphere, and magnetosphere as well as its interaction with the jovian surrounding in great details. Ahead of the arrival of JUICE at Jupiter, models have been developed to predict Ganymede's environment. Observational constraints are primarily given from Galileo and from Earth-based telescopes. They remain limited, especially in terms of the ionospheric number density and temperature. To address the currently poorly constrained ionospheric environment, we have developed a test particle model of Ganymede's plasma environment. The model is driven by the densities of neutral species from the exospheric model of Leblanc et al. (Icarus, 2016) and the electromagnetic field taken from the hybrid model of Leclercq et al. (PSS, 2016). The simulation follows the motion of millions of test particles in the environment of the moon and allows to generate maps of ion densities, bulk velocities, and temperatures. We will present simulation outcomes for different ions, including H+, O+, and O2+. We will also discuss how the results from the simulations are relevant to MHD and exospheric models and in interpreting plasma and particle data obtained by Galileo during its close flybys of Ganymede.

A charging model for three-axis stabilized spacecraft

NASA Technical Reports Server (NTRS)

Massaro, M. J.; Green, T.; Ling, D.

1977-01-01

A charging model was developed for geosynchronous, three-axis stabilized spacecraft when under the influence of a geomagnetic substorm. The differential charging potentials between the thermally coated or blanketed outer surfaces and metallic structure of a spacecraft were determined when the spacecraft was immersed in a dense plasma cloud of energetic particles. The spacecraft-to-environment interaction was determined by representing the charged particle environment by equivalent current source forcing functions and by representing the spacecraft by its electrically equivalent circuit with respect to the plasma charging phenomenon. The charging model included a sun/earth/spacecraft orbit model that simulated the sum illumination conditions of the spacecraft outer surfaces throughout the orbital flight on a diurnal as well as a seasonal basis. Transient and steady-state numerical results for a three-axis stabilized spacecraft are presented.

Plasma Flowfields Around Low Earth Orbit Objects: Aerodynamics to Underpin Orbit Predictions

NASA Astrophysics Data System (ADS)

Capon, Christopher; Boyce, Russell; Brown, Melrose

2016-07-01

Interactions between orbiting bodies and the charged space environment are complex. The large variation in passive body parameters e.g. size, geometry and materials, makes the plasma-body interaction in Low Earth Orbit (LEO) a region rich in fundamental physical phenomena. The aerodynamic interaction of LEO orbiting bodies with the neutral environment constitutes the largest non-conservative force on the body. However in general, study of the LEO plasma-body interaction has not been concerned with external flow physics, but rather with the effects on surface charging. The impact of ionospheric flow physics on the forces on space debris (and active objects) is not well understood. The work presented here investigates the contribution that plasma-body interactions have on the flow structure and hence on the total atmospheric force vector experienced by a polar orbiting LEO body. This work applies a hybrid Particle-in-Cell (PIC) - Direct Simulation Monte Carlo (DSMC) code, pdFoam, to self-consistently model the electrostatic flowfield about a cylinder with a uniform, fixed surface potential. Flow conditions are representative of the mean conditions experienced by the Earth Observing Satellite (EOS) based on the International Reference Ionosphere model (IRI-86). The electron distribution function is represented by a non-linear Boltzmann electron fluid and ion gas-surface interactions are assumed to be that of a neutralising, conducting, thermally accommodating solid wall with diffuse reflections. The variation in flowfield and aerodynamic properties with surface potential at a fixed flow condition is investigated, and insight into the relative contributions of charged and neutral species to the flow physics experienced by a LEO orbiting body is provided. This in turn is intended to help improve the fidelity of physics-based orbit predictions for space debris and other near-Earth space objects.

Novel ray tracing method for stray light suppression from ocean remote sensing measurements.

PubMed

Oh, Eunsong; Hong, Jinsuk; Kim, Sug-Whan; Park, Young-Je; Cho, Seong-Ick

2016-05-16

We developed a new integrated ray tracing (IRT) technique to analyze the stray light effect in remotely sensed images. Images acquired with the Geostationary Ocean Color Imager show a radiance level discrepancy at the slot boundary, which is suspected to be a stray light effect. To determine its cause, we developed and adjusted a novel in-orbit stray light analysis method, which consists of three simulated phases (source, target, and instrument). Each phase simulation was performed in a way that used ray information generated from the Sun and reaching the instrument detector plane efficiently. This simulation scheme enabled the construction of the real environment from the remote sensing data, with a focus on realistic phenomena. In the results, even in a cloud-free environment, a background stray light pattern was identified at the bottom of each slot. Variations in the stray light effect and its pattern according to bright target movement were simulated, with a maximum stray light ratio of 8.5841% in band 2 images. To verify the proposed method and simulation results, we compared the results with the real acquired remotely sensed image. In addition, after correcting for abnormal phenomena in specific cases, we confirmed that the stray light ratio decreased from 2.38% to 1.02% in a band 6 case, and from 1.09% to 0.35% in a band 8 case. IRT-based stray light analysis enabled clear determination of the stray light path and candidates in in-orbit circumstances, and the correction process aided recovery of the radiometric discrepancy.

Development of the GPM Observatory Thermal Vacuum Test Model

NASA Technical Reports Server (NTRS)

Yang, Kan; Peabody, Hume

2012-01-01

A software-based thermal modeling process was documented for generating the thermal panel settings necessary to simulate worst-case on-orbit flight environments in an observatory-level thermal vacuum test setup. The method for creating such a thermal model involved four major steps: (1) determining the major thermal zones for test as indicated by the major dissipating components on the spacecraft, then mapping the major heat flows between these components; (2) finding the flight equivalent sink temperatures for these test thermal zones; (3) determining the thermal test ground support equipment (GSE) design and initial thermal panel settings based on the equivalent sink temperatures; and (4) adjusting the panel settings in the test model to match heat flows and temperatures with the flight model. The observatory test thermal model developed from this process allows quick predictions of the performance of the thermal vacuum test design. In this work, the method described above was applied to the Global Precipitation Measurement (GPM) core observatory spacecraft, a joint project between NASA and the Japanese Aerospace Exploration Agency (JAXA) which is currently being integrated at NASA Goddard Space Flight Center for launch in Early 2014. From preliminary results, the thermal test model generated from this process shows that the heat flows and temperatures match fairly well with the flight thermal model, indicating that the test model can simulate fairly accurately the conditions on-orbit. However, further analysis is needed to determine the best test configuration possible to validate the GPM thermal design before the start of environmental testing later this year. Also, while this analysis method has been applied solely to GPM, it should be emphasized that the same process can be applied to any mission to develop an effective test setup and panel settings which accurately simulate on-orbit thermal environments.

The fast debris evolution model

NASA Astrophysics Data System (ADS)

Lewis, H. G.; Swinerd, G. G.; Newland, R. J.; Saunders, A.

2009-09-01

The 'particles-in-a-box' (PIB) model introduced by Talent [Talent, D.L. Analytic model for orbital debris environmental management. J. Spacecraft Rocket, 29 (4), 508-513, 1992.] removed the need for computer-intensive Monte Carlo simulation to predict the gross characteristics of an evolving debris environment. The PIB model was described using a differential equation that allows the stability of the low Earth orbit (LEO) environment to be tested by a straightforward analysis of the equation's coefficients. As part of an ongoing research effort to investigate more efficient approaches to evolutionary modelling and to develop a suite of educational tools, a new PIB model has been developed. The model, entitled Fast Debris Evolution (FADE), employs a first-order differential equation to describe the rate at which new objects ⩾10 cm are added and removed from the environment. Whilst Talent [Talent, D.L. Analytic model for orbital debris environmental management. J. Spacecraft Rocket, 29 (4), 508-513, 1992.] based the collision theory for the PIB approach on collisions between gas particles and adopted specific values for the parameters of the model from a number of references, the form and coefficients of the FADE model equations can be inferred from the outputs of future projections produced by high-fidelity models, such as the DAMAGE model. The FADE model has been implemented as a client-side, web-based service using JavaScript embedded within a HTML document. Due to the simple nature of the algorithm, FADE can deliver the results of future projections immediately in a graphical format, with complete user-control over key simulation parameters. Historical and future projections for the ⩾10 cm LEO debris environment under a variety of different scenarios are possible, including business as usual, no future launches, post-mission disposal and remediation. A selection of results is presented with comparisons with predictions made using the DAMAGE environment model. The results demonstrate that the FADE model is able to capture comparable time-series of collisions and number of objects as predicted by DAMAGE in several scenarios. Further, and perhaps more importantly, its speed and flexibility allows the user to explore and understand the evolution of the space debris environment.

Make Movies out of Your Dynamical Simulations with OGRE!

NASA Astrophysics Data System (ADS)

Tamayo, Daniel; Douglas, R. W.; Ge, H. W.; Burns, J. A.

2013-10-01

We have developed OGRE, the Orbital GRaphics Environment, an open-source project comprising a graphical user interface that allows the user to view the output from several dynamical integrators (e.g., SWIFT) that are commonly used for academic work. One can interactively vary the display speed, rotate the view and zoom the camera. This makes OGRE a great tool for students or the general public to explore accurate orbital histories that may display interesting dynamical features, e.g. the destabilization of Solar System orbits under the Nice model, or interacting pairs of exoplanets. Furthermore, OGRE allows the user to choreograph sequences of transformations as the simulation is played to generate movies for use in public talks or professional presentations. The graphical user interface is coded using Qt to ensure portability across different operating systems. OGRE will run on Linux and Mac OS X. The program is available as a self-contained executable, or as source code that the user can compile. We are continually updating the code, and hope that people who find it useful will contribute to the development of new features.

Make Movies out of Your Dynamical Simulations with OGRE!

NASA Astrophysics Data System (ADS)

Tamayo, Daniel; Douglas, R. W.; Ge, H. W.; Burns, J. A.

2014-01-01

We have developed OGRE, the Orbital GRaphics Environment, an open-source project comprising a graphical user interface that allows the user to view the output from several dynamical integrators (e.g., SWIFT) that are commonly used for academic work. One can interactively vary the display speed, rotate the view and zoom the camera. This makes OGRE a great tool for students or the general public to explore accurate orbital histories that may display interesting dynamical features, e.g. the destabilization of Solar System orbits under the Nice model, or interacting pairs of exoplanets. Furthermore, OGRE allows the user to choreograph sequences of transformations as the simulation is played to generate movies for use in public talks or professional presentations. The graphical user interface is coded using Qt to ensure portability across different operating systems. OGRE will run on Linux and Mac OS X. The program is available as a self-contained executable, or as source code that the user can compile. We are continually updating the code, and hope that people who find it useful will contribute to the development of new features.

Earth Satellite Population Instability: Underscoring the Need for Debris Mitigation

NASA Technical Reports Server (NTRS)

Liou, Jer-chyi; Johnson, N. L.

2006-01-01

A recent study by NASA indicates that the implementation of international orbital debris mitigation measures alone will not prevent a significant increase in the artificial Earth satellite population, beginning in the second half of this century. Whereas the focus of the aerospace community for the past 25 years has been on the curtailment of the generation of long-lived orbital debris, active remediation of the current orbital debris population should now be reconsidered to help preserve near-Earth space for future generations. In particular, we show in this paper that even if launch operations were to cease today, the population of space debris would continue to grow. Further, proposed remediation techniques do not appear to offer a viable solution. We therefore recommend that, while the aerospace community maintains the current debris-limiting mission regulations and postmission disposal procedures, future emphasis should be placed on finding new remediation technologies for solving this growing problem. Since the launch of Sputnik 1, space activities have created an orbital debris environment that poses increasing impact risks to existing space systems, including human space flight and robotic missions (1, 2). Currently, more than 9,000 Earth orbiting man-made objects (including many breakup fragments), with a combined mass exceeding 5 million kilograms, are tracked by the US Space Surveillance Network and maintained in the US satellite catalog (3-5). Three accidental collisions between cataloged satellites during the period from late 1991 to early 2005 have already been documented (6), although fortunately none resulted in the creation of large, trackable debris clouds. Several studies conducted during 1991-2001 demonstrated, with assumed future launch rates, the unintended growth potential of the Earth satellite population, resulting from random, accidental collisions among resident space objects (7-13). In some low Earth orbit (LEO) altitude regimes where the number density of satellites is above a critical spatial density, the production rate of new satellites (i.e., debris) due to collisions exceeds the loss of objects due to orbital decay. NASA s evolutionary satellite population model LEGEND (LEO-to-GEO Environment Debris model), developed by the Orbital Debris Program Office at the NASA Lyndon B. Johnson Space Center, is a high fidelity three-dimensional physical model that is capable of simulating the historical satellite environment, as well as the evolution of future debris populations (14, 15). The subject study assumed no rocket bodies and spacecraft were launched after December 2004, and no future disposal maneuvers were allowed for existing spacecraft, few of which currently have such a capability. The rate of satellite explosions would naturally decrease to zero within a few decades as the current satellite population ages. The LEGEND future projection adopts a Monte Carlo approach to simulate future on-orbit explosions and collisions. Within a given projection time step, once the explosion probability is estimated for an intact object, a random number is drawn and compared with the probability to determine if an explosion would occur. A similar procedure is applied to collisions for each pair of target and projectile involved within the same time step. Due to the nature of the Monte Carlo process, multiple projection runs must be performed and analyzed before one can draw reliable and meaningful conclusions from the outcome. A total of fifty, 200-year future projection Monte Carlo simulations were executed and evaluated (16).

Temporal Evolution of the Plasma Sheath Surrounding Solar Cells in Low Earth Orbit

NASA Technical Reports Server (NTRS)

Willis, Emily M.; Pour, Maria Z. A.

2017-01-01

Initial results from the PIC simulation and the LEM simulation have been presented. The PIC simulation results show that more detailed study is required to refine the ISS solar array current collection model and to understand the development of the current collection in time. The initial results from the LEM demonstrate that is it possible the transients are caused by solar array interaction with the environment, but there are presently too many assumptions in the model to be certain. Continued work on the PIC simulation will provide valuable information on the development of the barrier potential, which will allow refinement the LEM simulation and a better understanding of the causes and effects of the transients.

A study of Kapton degradation under simulated shuttle environment

NASA Technical Reports Server (NTRS)

Eck, T. G.; Hoffman, R. W.

1986-01-01

A system was developed which employs a source of low energy oxygen ion to simulate the shuttle low Earth orbit environment. This source, together with diagnostic tools including surface analysis ans mass spectroscopic capability, was used to measure the dependence of ion energy of the oxygen induced CO signals from pyrolytic graphite and Kapton. For graphite the CO signal was examined at energies ranging form 4.5 to 465 eV and for Kapton from 4.5 to 188 eV. While the relative quantum yields inferred from the data are reasonably precise, there are large uncertainties in the absolute yields because of the assumptions necessary to covert the measured signal strengths to quantum yields. These assumptions are discussed in detail.

Valence structures of aromatic bioactive compounds: a combined theoretical and experimental study.

PubMed

Wickrama Arachchilage, Anoja Pushpamali; Feyer, Vitaliy; Plekan, Oksana; Iakhnenko, Marianna; Prince, Kevin C; Wang, Feng

2012-09-01

Valence electronic structures of three recently isolated aryl bioactive compounds, namely 2-phenylethanol (2PE), p-hydroxyphenylethanol (HPE) and 4-hydroxybenzaldehyde (HBA), are studied using a combined theoretical and experimental method. Density functional theory-based calculations indicate that the side chains cause electron charge redistribution and therefore influence the aromaticity of the benzene derivatives. The simulated IR spectra further reveal features induced by the side chains. Solvent effects on the IR spectra are simulated using the polarizable continuum model, which exhibits enhancement of the O-H stretch vibrations with significant red-shift of 464 cm(-1) in 2PE. A significant spectral peak splitting of 94 cm(-1) between O(4)-H and O(8)-H of HPE is revealed in an aqueous environment. Experimental measurements for valence binding energy spectra for 2PE, HPE and HBA are presented and analyzed using outer-valence Green function calculations. The experimental (predicted) first ionization energies are measured as 9.19 (8.79), 8.47 (8.27) and 8.97 (8.82) eV for 2PE, HPE and HBA, respectively. The frontier orbitals (highest occupied molecular orbitals, HOMOs, and lowest unoccupied molecular orbitals, LUMOs) have similar atomic orbital characters although the HOMO-LUMO energy gaps are quite different.

Hybrid simulations of Venus' ionospheric magnetization states

NASA Astrophysics Data System (ADS)

Wiehle, Stefan; Motschmann, Uwe; Fränz, Markus

2013-04-01

The solar wind interaction with the plasma environment of Venus is studied with focus on ionospheric magnetization states using a 3D hybrid simulation code. The plasma environment of Venus was investigated mainly by Pioneer Venus Orbiter (PVO) and the still ongoing Venus Express (VEX) mission. Unlike many other planets, Venus' ionosphere is not shielded by a strong magnetosphere. Hence, data measured by spacecraft like PVO and VEX close to the planet are highly sensitive to solar wind and IMF upstream conditions, which cannot be measured while the spacecraft is inside the magnetosheath region about one hour before and after the closest approach. However, solar wind and IMF are known to change within minutes; ionospheric magnetization states, found by PVO and VEX, are highly dependent on the solar wind upstream pressure and also the magnetic field direction may change rapidly in case of a magnetic sector boundary crossing. When these solar wind induced transition effects occur, the causal change in the solar wind cannot be determined from ionospheric in-situ data. Additionally, with an orbital period of 24 hours, measuring transition timescales of solar wind triggered events is not possible. Our self-consistent simulations aim to provide a global picture of the solar wind interaction with Venus focusing on the effects of upstream fluctuations to the magnetic field in the vicinity of the planet. We use the A.I.K.E.F. (Adaptive Ion Kinetic Electron Fluid) 3D hybrid simulation code to model the entire Venus plasma environment. The simulation grid is refined within the ionosphere in order to resolve strong small-scale gradients of the magnetic field and ion density, a necessity to describe the magnetic field depletion inside the Venus' ionosphere. In contrast to other simulation studies, we apply no boundary conditions for the magnetic field at the planetary surface. Furthermore, we include varying upstream conditions like solar wind velocity and density as well as IMF strength and direction by adjusting these parameters after a first, quasi-stationary state has been reached. This allows for a simulation of dynamic processes like the transition between the magnetized and unmagnetized ionospheric state and fossil fields.

Radiation environment at LEO orbits: MC simulation and experimental data.

NASA Astrophysics Data System (ADS)

Zanini, Alba; Borla, Oscar; Damasso, Mario; Falzetta, Giuseppe

The evaluations of the different components of the radiation environment in spacecraft, both in LEO orbits and in deep space is of great importance because the biological effect on humans and the risk for instrumentation strongly depends on the kind of radiation (high or low LET). That is important especially in view of long term manned or unmanned space missions, (mission to Mars, solar system exploration). The study of space radiation field is extremely complex and not completely solved till today. Given the complexity of the radiation field, an accurate dose evaluation should be considered an indispensable part of any space mission. Two simulation codes (MCNPX and GEANT4) have been used to assess the secondary radiation inside FO-TON M3 satellite and ISS. The energy spectra of primary radiation at LEO orbits have been modelled by using various tools (SPENVIS, OMERE, CREME96) considering separately Van Allen protons, the GCR protons and the GCR alpha particles. This data are used as input for the two MC codes and transported inside the spacecraft. The results of two calculation meth-ods have been compared. Moreover some experimental results previously obtained on FOTON M3 satellite by using TLD, Bubble dosimeter and LIULIN detector are considered to check the performances of the two codes. Finally the same experimental device are at present collecting data on the ISS (ASI experiment BIOKIS -nDOSE) and at the end of the mission the results will be compared with the calculation.

The PocketSpacecraft.com Integrated eXploration Environment (PIXE)

NASA Astrophysics Data System (ADS)

Johnson, Michael

2015-04-01

The PocketSpacecraft.com Integrated eXploration Environment (PIXE) is an integrated generic spacecraft design, simulation, manufacturing, and operations system for the low cost mass exploration of space by amateur and professional Principle Investigators (PIs). PIs use an online tool to design Thin-Film Spacecraft/Lander/Rovers (TF-SLRs) using a library of predefined spacecraft and mission components to specify TF-SLRs in quantities ranging from one to thousands per mission, each with a typical mass <1g, surface area <1m2, and

A Fast Method for Embattling Optimization of Ground-Based Radar Surveillance Network

NASA Astrophysics Data System (ADS)

Jiang, H.; Cheng, H.; Zhang, Y.; Liu, J.

A growing number of space activities have created an orbital debris environment that poses increasing impact risks to existing space systems and human space flight. For the safety of in-orbit spacecraft, a lot of observation facilities are needed to catalog space objects, especially in low earth orbit. Surveillance of Low earth orbit objects are mainly rely on ground-based radar, due to the ability limitation of exist radar facilities, a large number of ground-based radar need to build in the next few years in order to meet the current space surveillance demands. How to optimize the embattling of ground-based radar surveillance network is a problem to need to be solved. The traditional method for embattling optimization of ground-based radar surveillance network is mainly through to the detection simulation of all possible stations with cataloged data, and makes a comprehensive comparative analysis of various simulation results with the combinational method, and then selects an optimal result as station layout scheme. This method is time consuming for single simulation and high computational complexity for the combinational analysis, when the number of stations increases, the complexity of optimization problem will be increased exponentially, and cannot be solved with traditional method. There is no better way to solve this problem till now. In this paper, target detection procedure was simplified. Firstly, the space coverage of ground-based radar was simplified, a space coverage projection model of radar facilities in different orbit altitudes was built; then a simplified objects cross the radar coverage model was established according to the characteristics of space objects orbit motion; after two steps simplification, the computational complexity of the target detection was greatly simplified, and simulation results shown the correctness of the simplified results. In addition, the detection areas of ground-based radar network can be easily computed with the simplified model, and then optimized the embattling of ground-based radar surveillance network with the artificial intelligent algorithm, which can greatly simplifies the computational complexities. Comparing with the traditional method, the proposed method greatly improved the computational efficiency.

A spacecraft's own ambient environment: The role of simulation-based research

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ketsdever, Andrew D.; Gimelshein, Sergey

2014-12-09

Spacecraft contamination has long been a subject of study in the rarefied gas dynamics community. Professor Mikhail Ivanov coined the term a spacecraft's 'own ambient environment' to describe the effects of natural and satellite driven processes on the conditions encountered by a spacecraft in orbit. Outgassing, thruster firings, and gas and liquid dumps all contribute to the spacecraft's contamination environment. Rarefied gas dynamic modeling techniques, such as Direct Simulation Monte Carlo, are well suited to investigate these spacebased environments. However, many advances were necessary to fully characterize the extent of this problem. A better understanding of modeling flows over largemore » pressure ranges, for example hybrid continuum and rarefied numerical schemes, were required. Two-phase flow modeling under rarefied conditions was necessary. And the ability to model plasma flows for a new era of propulsion systems was also required. Through the work of Professor Ivanov and his team, we now have a better understanding of processes that create a spacecraft's own ambient environment and are able to better characterize these environments. Advances in numerical simulation have also spurred on the development of experimental facilities to study these effects. The relationship between numerical results and experimental advances will be explored in this manuscript.« less

Thermal testing by internal IR heating of the FEP module

NASA Technical Reports Server (NTRS)

Nathanson, D. M.; Efromson, R. A.; Lee, E. I.

1986-01-01

A spacecraft module, to be integrated with the FLTSATCOM spacecraft, was tested in a simulated orbit environment separate from the host spacecraft. Thermal vacuum testing of the module was accomplished using internal IR heating rather than conventional external heat sources. For this configuration, the technique produced boundary conditions expected for flight to enable verification of system performance and thermal design details.

STS-52 Commander Wetherbee, in LES/LEH, during JSC WETF bailout exercises

NASA Technical Reports Server (NTRS)

1992-01-01

STS-52 Columbia, Orbiter Vehicle (OV) 102, Commander James D. Wetherbee, fully outfitted in a launch and entry suit (LES) and launch and entry helmet (LEH), prepares for emergency egress (bailout) training exercise in JSC's Weightless Environment Training Facility (WETF) Bldg 29 pool. The WETF's 25-ft deep pool will be used to simulate a water landing.

STS-46 ESA MS Nicollier in life raft during water egress training at JSC WETF

NASA Technical Reports Server (NTRS)

1992-01-01

STS-46 Atlantis, Orbiter Vehicle (OV) 104, European Space Agency (ESA) Mission Specialist (MS) Claude Nicollier, wearing launch and entry suit (LES) and launch and entry helmet (LEH), floats in a one-person life raft during a launch emergency egress (bailout) simulation conducted in JSC's Weightless Environment Training Facility (WETF) Bldg 29 pool.

STS-26 Pilot Covey floats in life raft during JSC WETF exercises

NASA Technical Reports Server (NTRS)

1988-01-01

STS-26 Discovery, Orbiter Vehicle (OV) 103, Pilot Richard O. Covey, wearing the newly designed launch and entry suit (LES), floats in single-occupant life raft in JSC Weightless Environment Training Facility (WETF) Bldg 29 pool. The simulation of the escape and rescue operations utilized the crew escape system (CES) pole method of egress from the Space Shuttle.

STS-46 MS Chang-Diaz floats in life raft during water egress training at JSC

NASA Technical Reports Server (NTRS)

1992-01-01

STS-46 Atlantis, Orbiter Vehicle (OV) 104, Mission Specialist (MS) Franklin R. Chang-Diaz, wearing launch and entry suit (LES) and launch and entry helmet (LEH), relies on a one-person life raft to get him to 'safety' during a launch emergency egress (bailout) simulation conducted in JSC's Weightless Environment Training Facility (WETF) Bldg 29 pool.

Simulation of Electric Propulsion Thrusters

DTIC Science & Technology

2011-01-01

and operational lifetime. The second area of modelling activity concerns the plumes produced by electric thrusters. Detailed information on the plumes ...to reproduce the in-orbit space environment using ground-based laboratory facilities. Device modelling also plays an important role in plume ...of the numerical analysis of other aspects of thruster design, such as thermal and structural processes, is omitted here. There are two fundamental

Degradation of the Adhesive Properties of MD-944 Diode Tape by Simulated Low Earth Orbit Environmental Factors

NASA Technical Reports Server (NTRS)

Albyn, K.; Finckenor, M.

2006-01-01

The International Space Station (ISS) solar arrays utilize MD-944 diode tape with silicone pressure-sensitive adhesive to protect the underlying diodes and also provide a high-emittance surface. On-orbit, the silicone adhesive will be exposed and ultimately convert to a glass-like silicate due to atomic oxygen (AO). The current operational plan is to retract ISS solar array P6 and leave it stored under load for a long duration (6 mo or more). The exposed silicone adhesive must not cause the solar array to stick to itself or cause the solar array to fail during redeployment. The Environmental Effects Branch at Marshall Space Flight Center, under direction from the ISS Program Office Environments Team, performed simulated space environment exposures with 5-eV AO, near ultraviolet radiation and ionizing radiation. The exposed diode tape samples were put under preload and then the resulting blocking force was measured using a tensile test machine. Test results indicate that high-energy AO, ultraviolet radiation, and electron ionizing radiation exposure all reduce the blocking force for a silicone-to-silicone bond. AO exposure produces the most significant reduction in blocking force

Technology Developments Integrating a Space Network Communications Testbed

NASA Technical Reports Server (NTRS)

Kwong, Winston; Jennings, Esther; Clare, Loren; Leang, Dee

2006-01-01

As future manned and robotic space explorations missions involve more complex systems, it is essential to verify, validate, and optimize such systems through simulation and emulation in a low cost testbed environment. The goal of such a testbed is to perform detailed testing of advanced space and ground communications networks, technologies, and client applications that are essential for future space exploration missions. We describe the development of new technologies enhancing our Multi-mission Advanced Communications Hybrid Environment for Test and Evaluation (MACHETE) that enable its integration in a distributed space communications testbed. MACHETE combines orbital modeling, link analysis, and protocol and service modeling to quantify system performance based on comprehensive considerations of different aspects of space missions. It can simulate entire networks and can interface with external (testbed) systems. The key technology developments enabling the integration of MACHETE into a distributed testbed are the Monitor and Control module and the QualNet IP Network Emulator module. Specifically, the Monitor and Control module establishes a standard interface mechanism to centralize the management of each testbed component. The QualNet IP Network Emulator module allows externally generated network traffic to be passed through MACHETE to experience simulated network behaviors such as propagation delay, data loss, orbital effects and other communications characteristics, including entire network behaviors. We report a successful integration of MACHETE with a space communication testbed modeling a lunar exploration scenario. This document is the viewgraph slides of the presentation.

Implementation of an open-scenario, long-term space debris simulation approach

NASA Astrophysics Data System (ADS)

Stupl, J.; Nelson, B.; Faber, N.; Perez, A.; Carlino, R.; Yang, F.; Henze, C.; Karacalioglu, A.; O'Toole, C.; Swenson, J.

This paper provides a status update on the implementation of a flexible, long-term space debris simulation approach. The motivation is to build a tool that can assess the long-term impact of various options for debris-remediation, including the LightForce space debris collision avoidance scheme. State-of-the-art simulation approaches that assess the long-term development of the debris environment use either completely statistical approaches, or they rely on large time steps in the order of several (5-15) days if they simulate the positions of single objects over time. They cannot be easily adapted to investigate the impact of specific collision avoidance schemes or de-orbit schemes, because the efficiency of a collision avoidance maneuver can depend on various input parameters, including ground station positions, space object parameters and orbital parameters of the conjunctions and take place in much smaller timeframes than 5-15 days. For example, LightForce only changes the orbit of a certain object (aiming to reduce the probability of collision), but it does not remove entire objects or groups of objects. In the same sense, it is also not straightforward to compare specific de-orbit methods in regard to potential collision risks during a de-orbit maneuver. To gain flexibility in assessing interactions with objects, we implement a simulation that includes every tracked space object in LEO, propagates all objects with high precision, and advances with variable-sized time-steps as small as one second. It allows the assessment of the (potential) impact of changes to any object. The final goal is to employ a Monte Carlo approach to assess the debris evolution during the simulation time-frame of 100 years and to compare a baseline scenario to debris remediation scenarios or other scenarios of interest. To populate the initial simulation, we use the entire space-track object catalog in LEO. We then use a high precision propagator to propagate all objects over the entire simulation duration. If collisions are detected, the appropriate number of debris objects are created and inserted into the simulation framework. Depending on the scenario, further objects, e.g. due to new launches, can be added. At the end of the simulation, the total number of objects above a cut-off size and the number of detected collisions provide benchmark parameters for the comparison between scenarios. The simulation approach is computationally intensive as it involves ten thousands of objects; hence we use a highly parallel approach employing up to a thousand cores on the NASA Pleiades supercomputer for a single run. This paper describes our simulation approach, the status of its implementation, the approach in developing scenarios and examples of first test runs.

Handover aspects for a Low Earth Orbit (LEO) CDMA Land Mobile Satellite (LMS) system

NASA Technical Reports Server (NTRS)

Carter, P.; Beach, M. A.

1993-01-01

This paper addresses the problem of handoff in a land mobile satellite (LMS) system between adjacent satellites in a low earth orbit (LEO) constellation. In particular, emphasis is placed on the application of soft handoff in a direct sequence code division multiple access (DS-CDMA) LMS system. Soft handoff is explained in terms of terrestrial macroscopic diversity, in which signals transmitted via several independent fading paths are combined to enhance the link quality. This concept is then reconsidered in the context of a LEO LMS system. A two-state Markov channel model is used to simulate the effects of shadowing on the communications path from the mobile to each satellite during handoff. The results of the channel simulation form a platform for discussion regarding soft handoff, highlighting the potential merits of the scheme when applied in a LEO LMS environment.

Instability of the Present LEO Satellite Populations

NASA Technical Reports Server (NTRS)

Liou, Jer-Chyi; Johnson, Nicholas L.

2006-01-01

Several studies conducted during 1991-2001 demonstrated, with some assumed launch rates, the future unintended growth potential of the Earth satellite population, resulting from random, accidental collisions among resident space objects. In some low Earth orbit (LEO) altitude regimes where the number density of satellites is above a critical spatial density, the production rate of new breakup debris due to collisions would exceed the loss of objects due to orbital decay. A new study has been conducted in the Orbital Debris Program Office at the NASA Lyndon B. Johnson Space Center, using higher fidelity models to evaluate the current debris environment. The study assumed no satellites were launched after December 2005. A total of 150 Monte Carlo runs were carried out and analyzed. Each Monte Carlo run simulated the current debris environment and projected it 200 years into the future. The results indicate that the LEO debris environment has reached a point such that even if no further space launches were conducted, the Earth satellite population would remain relatively constant for only the next 50 years or so. Beyond that, the debris population would begin to increase noticeably, due to the production of collisional debris. Detailed analysis shows that this growth is primarily driven by high collision activities around 900 to 1000 km altitude - the region which has a very high concentration of debris at present. In reality, the satellite population growth in LEO will undoubtedly be worse than this study indicates, since spacecraft and their orbital stages will continue to be launched into space. Postmission disposal of vehicles (e.g., limiting postmission orbital lifetimes to less than 25 years) will help, but will be insufficient to constrain the Earth satellite population. To preserve better the near-Earth environment for future space activities, it might be necessary to remove existing large and massive objects from regions where high collision activities are expected.

Simulation of space radiation effects on polyimide film materials for high temperature applications

NASA Technical Reports Server (NTRS)

Fogdall, L. B.; Cannaday, S. S.

1977-01-01

Space environment effects on candidate materials for the solar sail film are determined. Polymers, including metallized polyimides that might be suitable solar radiation receivers, were exposed to combined proton and solar electromagnetic radiation. Each test sample was weighted, to simulate the tension on the polymer when it is stretched into near-planar shape while receiving solar radiation. Exposure rates up to 16 times that expected in Earth orbit were employed, to simulate near-sun solar sailing conditions. Sample appearance, elongation, and shrinkage were monitored, noted, and documented in situ. Thermosetting polyimides showed less degradation or visual change in appearance than thermoplastics.

ViSBARD: Visual System for Browsing, Analysis and Retrieval of Data

NASA Astrophysics Data System (ADS)

Roberts, D. Aaron; Boller, Ryan; Rezapkin, V.; Coleman, J.; McGuire, R.; Goldstein, M.; Kalb, V.; Kulkarni, R.; Luckyanova, M.; Byrnes, J.; Kerbel, U.; Candey, R.; Holmes, C.; Chimiak, R.; Harris, B.

2018-04-01

ViSBARD interactively visualizes and analyzes space physics data. It provides an interactive integrated 3-D and 2-D environment to determine correlations between measurements across many spacecraft. It supports a variety of spacecraft data products and MHD models and is easily extensible to others. ViSBARD provides a way of visualizing multiple vector and scalar quantities as measured by many spacecraft at once. The data are displayed three-dimesionally along the orbits which may be displayed either as connected lines or as points. The data display allows the rapid determination of vector configurations, correlations between many measurements at multiple points, and global relationships. With the addition of magnetohydrodynamic (MHD) model data, this environment can also be used to validate simulation results with observed data, use simulated data to provide a global context for sparse observed data, and apply feature detection techniques to the simulated data.

EUSO@TurLab: An experimental replica of ISS orbits

NASA Astrophysics Data System (ADS)

Bertaina, M.; Bowaire, A.; Cambursano, S.; Caruso, R.; Contino, G.; Cotto, G.; Crivello, F.; Forza, R.; Guardone, N.; Manfrin, M.; Mignone, M.; Mulas, R.; Suino, G.; Tibaldi, P. S.

2015-03-01

The EUSO@TurLab project is an on-going activity aimed to reproduce atmospheric and luminous conditions that JEM-EUSO will encounter on its orbits around the Earth. The use of the TurLab facility, part of the Department of Physics of the University of Torino, allows the simulation of different surface conditions in a very dark and rotating environment in order to test the response of JEM-EUSO's sensors and sensitivity. The experimental setup currently in operation has been used to check the potential of the TurLab facility for the above purposes, and the acquired data will be used to test the concept of JEM-EUSO's trigger system.

Thermal design of the IUE hydrazine auxiliary propulsion system. [International Ultraviolet Explorer

NASA Technical Reports Server (NTRS)

Skladany, J. T.; Kelly, W. H.

1977-01-01

The International Ultraviolet Explorer is a large astronomical observatory scheduled to be placed in a three-axis stabilized synchronous orbit in the fourth quarter of 1977. The Hydrazine Auxiliary Propulsion System (HAPS) must perform a number of spacecraft maneuvers to achieve a successful mission. This paper describes the thermal design which accomplishes temperature control between 5 and 65 C for all orbital conditions by utilizing multilayer insulation and commandable component heaters. A primary design criteria was the minimization of spacecraft power by the selective use of the solar environment. The thermal design was carefully assessed and verified in both spacecraft thermal balance and subsystem solar simulation testing.

Object oriented studies into artificial space debris

NASA Technical Reports Server (NTRS)

Adamson, J. M.; Marshall, G.

1988-01-01

A prototype simulation is being developed under contract to the Royal Aerospace Establishment (RAE), Farnborough, England, to assist in the discrimination of artificial space objects/debris. The methodology undertaken has been to link Object Oriented programming, intelligent knowledge based system (IKBS) techniques and advanced computer technology with numeric analysis to provide a graphical, symbolic simulation. The objective is to provide an additional layer of understanding on top of conventional classification methods. Use is being made of object and rule based knowledge representation, multiple reasoning, truth maintenance and uncertainty. Software tools being used include Knowledge Engineering Environment (KEE) and SymTactics for knowledge representation. Hooks are being developed within the SymTactics framework to incorporate mathematical models describing orbital motion and fragmentation. Penetration and structural analysis can also be incorporated. SymTactics is an Object Oriented discrete event simulation tool built as a domain specific extension to the KEE environment. The tool provides facilities for building, debugging and monitoring dynamic (military) simulations.

Selection considerations between ZERODUR® and silicon carbide for dimensionally-stable spaceborne optical telescopes in two-earth-orbits

NASA Astrophysics Data System (ADS)

Hull, Tony; Westerhoff, Thomas; Weidmann, Gunter

2015-09-01

A key consideration in defining a space telescope mission is definition of the optical materials. This selection defines both the performance of the system and system complexity and cost. Optimal material selection for system stability must consider the thermal environment and its variation. Via numerical simulations, we compare the thermal and structural-mechanical behavior of ZERODUR® and SiC as mirror substrates for telescope assemblies in space. SiC has significantly larger CTE values then ZERODUR®, but also its thermal diffusivity k/(ρcp) is larger, and that helps to homogenize thermal gradients in the mirror. Therefore it is not obvious at first glance which material performs with better dimensional stability under realistic unsteady, inhomogeneous thermal loads. We specifically examine the telescope response to transient, gradient driving, thermal environments representative of low- and high-earth- orbits.

MSFC Thermal Protection System Materials on MISSE-6

NASA Technical Reports Server (NTRS)

Finckenor, Miria M.; Valentine, Peter G.; Gubert, Michael K.

2010-01-01

The Lightweight Nonmetallic Thermal Protection Materials Technology (LNTPMT) program studied a number of ceramic matrix composites, ablator materials, and tile materials for durability in simulated space environment. Materials that indicated low atomic oxygen reactivity and negligible change in thermo-optical properties in ground testing were selected to fly on the Materials on International Space Station Experiment (MISSE)-6. These samples were exposed for 17 months to the low Earth orbit environment on both the ram and wake sides of MISSE-6B. Thermo-optical properties are discussed, along with any changes in mass.

Constraints on the Dynamical Environments of Supermassive Black-Hole Binaries Using Pulsar-Timing Arrays.

PubMed

Taylor, Stephen R; Simon, Joseph; Sampson, Laura

2017-05-05

We introduce a technique for gravitational-wave analysis, where Gaussian process regression is used to emulate the strain spectrum of a stochastic background by training on population-synthesis simulations. This leads to direct Bayesian inference on astrophysical parameters. For pulsar timing arrays specifically, we interpolate over the parameter space of supermassive black-hole binary environments, including three-body stellar scattering, and evolving orbital eccentricity. We illustrate our approach on mock data, and assess the prospects for inference with data similar to the NANOGrav 9-yr data release.

Mission Design and Simulation Considerations for ADReS-A

NASA Astrophysics Data System (ADS)

Peters, S.; Förstner, R.; Fiedler, H.

2016-09-01

Space debris in general has become a major problem for modern space activities. Guidelines to mitigate the threat have been recommended, better prediction models are developed and an advanced observation of objects orbiting Earth is in progress. And still - without the implementation of active debris removal (ADR), the number of debris in space will exponentially increase. To support the ongoing research on ADR-missions, this paper presents the updated mission design of ADReS-A (Autonomous Debris Removal Satellite - #A) - one possible concept for the multiple active removal of large debris in Low Earth orbit, in this case especially of rocket bodies of the SL-8-type. ADReS-A as chaser satellite is supported by at least 5 de-orbit kits, allowing for the same number of targets to be removed. While ADReS-A is conceived for handling of the target, the kit's task is the controlled re-entry of the designated rocket body. The presented mission design forms the basis for the simulation environment in progress. The simulation shall serve as testbed to test multiple scenarios in terms of approach and abort optimization or different tumbling modes of the target. The ultimate goal is the test of autonomous behaviors of the spacecraft in case of unforeseen failures during the approach phase. Considerations to create a simulation for the described mission are presented and discussed. A first visualization of pre-calculated aboard trajectories can be found at the end of this paper.

Orbits: Computer simulation

NASA Technical Reports Server (NTRS)

Muszynska, A.

1985-01-01

In rotating machinery dynamics an orbit (Lissajous curve) represents the dynamic path of the shaft centerline motion during shaft rotation and resulting precession. The orbit can be observed with an oscilloscope connected to XY promixity probes. The orbits can also be simulated by a computer. The software for HP computer simulates orbits for two cases: (1) Symmetric orbit with four frequency components with different radial amplitudes and relative phase angles; and (2) Nonsymmetric orbit with two frequency components with two different vertical/horizontal amplitudes and two different relative phase angles. Each orbit carries a Keyphasor mark (one-per-turn reference). The frequencies, amplitudes, and phase angles, as well as number of time steps for orbit computation, have to be chosen and introduced to the computer by the user. The orbit graphs can be observed on the computer screen.

Comparison of debris flux models

NASA Astrophysics Data System (ADS)

Sdunnus, H.; Beltrami, P.; Klinkrad, H.; Matney, M.; Nazarenko, A.; Wegener, P.

The availability of models to estimate the impact risk from the man-made space debris and the natural meteoroid environment is essential for both, manned and unmanned satellite missions. Various independent tools based on different approaches have been developed in the past years. Due to an increased knowledge of the debris environment and its sources e.g. from improved measurement capabilities, these models could be updated regularly, providing more detailed and more reliable simulations. This paper addresses an in-depth, quantitative comparison of widely distributed debris flux models which were recently updated, namely ESA's MASTER 2001 model, NASA's ORDEM 2000 and the Russian SDPA 2000 model. The comparison was performed in the frame of the work of the 20t h Interagency Debris Coordination (IADC) meeting held in Surrey, UK. ORDEM 2000ORDEM 2000 uses careful empirical estimates of the orbit populations based onthree primary data sources - the US Space Command Catalog, the H ystackaRadar, and the Long Duration Exposure Facility spacecraft returned surfaces.Further data (e.g. HAX and Goldstone radars, impacts on Shuttle windows andradiators, and others) were used to adjust these populations for regions in time,size, and space not covered by the primary data sets. Some interpolation andextrapolation to regions with no data (such as projections into the future) wasprovided by the EVOLVE model. MASTER 2001The ESA MASTER model offers a full three dimensional description of theterrestrial debris distribution reaching from LEO up to the GEO region. Fluxresults relative to an orbiting target or to an inertial volume can be resolved intosource terms, impactor characteristics and orbit, as well as impact velocity anddirection. All relevant debris source terms are considered by the MASTERmodel. For each simulated source, a corresponding debris generation model interms of mass/diameter distribution, additional velocities, and directionalspreading has been developed. A comprehensive perturbation model was used topropagate all objects to a reference epoch. SDPA 2000The Russian Space Debris Prediction and Analysis (SDPA) model is the semi-analytical stochastic tool for medium- and long-term forecast of the man-madedebris environment (with size larger than 1 mm), for construction of spatialdensity and velocity distribution in LEO and GEO as well as for risk evaluation.The last version of SDPA 2000 consists of ten individual modules related to theaforementioned tasks. The total characteristics of space debris of the differentsizes are considered (without partition of these characteristics into specificsources). The current space debris environment is characterised a) by the spatialdensity dependence on the altitude and latitude of a point, as well as on size ofobjects and b) by a statistical distribution of the magnitude and direction of spaceobjects velocities in an inertial geocentric coordinate system. Thesecharacteristics are constructed on the basis of the complex application of theaccessible measuring information and series of a priori data. The comparison is performed by applying the models to a large number of target orbits specified by a grid in terms of impactor size (6 gridpoints), target orbit perigee altitude (16 gridpoints), and target orbit inclination (15 gridpoints). These result provide a characteristic diagram of integral fluxes for all models, which will be compared. Further to this, the models are applied to orbits of particular interest, namely the ISS orbit, and a sun-synchronous orbit. For these cases, the comparison will include the comparison of flux directionality and velocity. References 1. Liou, J.-C., M. J. Matney, P. D. Anz-Meador, D. Kessler, M. Jansen, and J. R.Theall, 2001, "The New NASA Orbital Debris Engineering ModelORDEM2000", NASA/TP-2002-210780. 2. P. Wegener, J. Bendisch, K.D. Bunte, H. Sdunnus; Upgrade of the ESAMASTER Model; Final Report of ESOC/TOS-GMA contract 12318/97/D/IM;May 2000 3. A.I. Nazarenko, I.L. Menchikov. Engineering Model of Space DebrisEnvironment. Third European Conference on Space Debris, Darmstadt,Germany, March 2001.

Plant growth strategies are remodeled by spaceflight.

PubMed

Paul, Anna-Lisa; Amalfitano, Claire E; Ferl, Robert J

2012-12-07

Arabidopsis plants were grown on the International Space Station within specialized hardware that combined a plant growth habitat with a camera system that can capture images at regular intervals of growth. The Imaging hardware delivers telemetric data from the ISS, specifically images received in real-time from experiments on orbit, providing science without sample return. Comparable Ground Controls were grown in a sister unit that is maintained in the Orbital Environment Simulator at Kennedy Space Center. One of many types of biological data that can be analyzed in this fashion is root morphology. Arabidopsis seeds were geminated on orbit on nutrient gel Petri plates in a configuration that encouraged growth along the surface of the gel. Photos were taken every six hours for the 15 days of the experiment. In the absence of gravity, but the presence of directional light, spaceflight roots remained strongly negatively phototropic and grew in the opposite direction of the shoot growth; however, cultivars WS and Col-0 displayed two distinct, marked differences in their growth patterns. First, cultivar WS skewed strongly to the right on orbit, while cultivar Col-0 grew with little deviation away from the light source. Second, the Spaceflight environment also impacted the rate of growth in Arabidopsis. The size of the Flight plants (as measured by primary root and hypocotyl length) was uniformly smaller than comparably aged Ground Control plants in both cultivars. Skewing and waving, thought to be gravity dependent phenomena, occur in spaceflight plants. In the presence of an orienting light source, phenotypic trends in skewing are gravity independent, and the general patterns of directional root growth typified by a given genotype in unit gravity are recapitulated on orbit, although overall growth patterns on orbit are less uniform. Skewing appears independent of axial orientation on the ISS - suggesting that other tropisms (such as for oxygen and temperature) do not influence skewing. An aspect of the spaceflight environment also retards the rate of early Arabidopsis growth.

LEOrbit: A program to calculate parameters relevant to modeling Low Earth Orbit spacecraft-plasma interaction

NASA Astrophysics Data System (ADS)

Marchand, R.; Purschke, D.; Samson, J.

2013-03-01

Understanding the physics of interaction between satellites and the space environment is essential in planning and exploiting space missions. Several computer models have been developed over the years to study this interaction. In all cases, simulations are carried out in the reference frame of the spacecraft and effects such as charging, the formation of electrostatic sheaths and wakes are calculated for given conditions of the space environment. In this paper we present a program used to compute magnetic fields and a number of space plasma and space environment parameters relevant to Low Earth Orbits (LEO) spacecraft-plasma interaction modeling. Magnetic fields are obtained from the International Geophysical Reference Field (IGRF) and plasma parameters are obtained from the International Reference Ionosphere (IRI) model. All parameters are computed in the spacecraft frame of reference as a function of its six Keplerian elements. They are presented in a format that can be used directly in most spacecraft-plasma interaction models. Catalogue identifier: AENY_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AENY_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 270308 No. of bytes in distributed program, including test data, etc.: 2323222 Distribution format: tar.gz Programming language: FORTRAN 90. Computer: Non specific. Operating system: Non specific. RAM: 7.1 MB Classification: 19, 4.14. External routines: IRI, IGRF (included in the package). Nature of problem: Compute magnetic field components, direction of the sun, sun visibility factor and approximate plasma parameters in the reference frame of a Low Earth Orbit satellite. Solution method: Orbit integration, calls to IGRF and IRI libraries and transformation of coordinates from geocentric to spacecraft frame reference. Restrictions: Low Earth orbits, altitudes between 150 and 2000 km. Running time: Approximately two seconds to parameterize a full orbit with 1000 points.

Plant growth strategies are remodeled by spaceflight

PubMed Central

2012-01-01

Background Arabidopsis plants were grown on the International Space Station within specialized hardware that combined a plant growth habitat with a camera system that can capture images at regular intervals of growth. The Imaging hardware delivers telemetric data from the ISS, specifically images received in real-time from experiments on orbit, providing science without sample return. Comparable Ground Controls were grown in a sister unit that is maintained in the Orbital Environment Simulator at Kennedy Space Center. One of many types of biological data that can be analyzed in this fashion is root morphology. Arabidopsis seeds were geminated on orbit on nutrient gel Petri plates in a configuration that encouraged growth along the surface of the gel. Photos were taken every six hours for the 15 days of the experiment. Results In the absence of gravity, but the presence of directional light, spaceflight roots remained strongly negatively phototropic and grew in the opposite direction of the shoot growth; however, cultivars WS and Col-0 displayed two distinct, marked differences in their growth patterns. First, cultivar WS skewed strongly to the right on orbit, while cultivar Col-0 grew with little deviation away from the light source. Second, the Spaceflight environment also impacted the rate of growth in Arabidopsis. The size of the Flight plants (as measured by primary root and hypocotyl length) was uniformly smaller than comparably aged Ground Control plants in both cultivars. Conclusions Skewing and waving, thought to be gravity dependent phenomena, occur in spaceflight plants. In the presence of an orienting light source, phenotypic trends in skewing are gravity independent, and the general patterns of directional root growth typified by a given genotype in unit gravity are recapitulated on orbit, although overall growth patterns on orbit are less uniform. Skewing appears independent of axial orientation on the ISS – suggesting that other tropisms (such as for oxygen and temperature) do not influence skewing. An aspect of the spaceflight environment also retards the rate of early Arabidopsis growth. PMID:23217113

Test and Analysis Capabilities of the Space Environment Effects Team at Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

Finckenor, M. M.; Edwards, D. L.; Vaughn, J. A.; Schneider, T. A.; Hovater, M. A.; Hoppe, D. T.

2002-01-01

Marshall Space Flight Center has developed world-class space environmental effects testing facilities to simulate the space environment. The combined environmental effects test system exposes temperature-controlled samples to simultaneous protons, high- and low-energy electrons, vacuum ultraviolet (VUV) radiation, and near-ultraviolet (NUV) radiation. Separate chambers for studying the effects of NUV and VUV at elevated temperatures are also available. The Atomic Oxygen Beam Facility exposes samples to atomic oxygen of 5 eV energy to simulate low-Earth orbit (LEO). The LEO space plasma simulators are used to study current collection to biased spacecraft surfaces, arcing from insulators and electrical conductivity of materials. Plasma propulsion techniques are analyzed using the Marshall magnetic mirror system. The micro light gas gun simulates micrometeoroid and space debris impacts. Candidate materials and hardware for spacecraft can be evaluated for durability in the space environment with a variety of analytical techniques. Mass, solar absorptance, infrared emittance, transmission, reflectance, bidirectional reflectance distribution function, and surface morphology characterization can be performed. The data from the space environmental effects testing facilities, combined with analytical results from flight experiments, enable the Environmental Effects Group to determine optimum materials for use on spacecraft.

Berthing simulator for space station and orbiter

NASA Technical Reports Server (NTRS)

Veerasamy, Sam

1991-01-01

The development of a real-time man-in-the-loop berthing simulator is in progress at NASA Lyndon B. Johnson Space Center (JSC) to conduct a parametric study and to measure forces during contact conditions of the actual docking mechanisms for the Space Station Freedom and the orbiter. In berthing, the docking ports of the Space Station and the orbiter are brought together using the orbiter robotic arm to control the relative motion of the vehicles. The berthing simulator consists of a dynamics docking test system (DDTS), computer system, simulator software, and workstations. In the DDTS, the Space Station, and the orbiter docking mechanisms are mounted on a six-degree-of-freedom (6 DOF) table and a fixed platform above the table. Six load cells are used on the fixed platform to measure forces during contact conditions of the docking mechanisms. Two Encore Concept 32/9780 computers are used to simulate the orbiter robotic arm and to operate the berthing simulator. A systematic procedure for a real-time dynamic initialization is being developed to synchronize the Space Station docking port trajectory with the 6 DOF table movement. The berthing test can be conducted manually or automatically and can be extended for any two orbiting vehicles using a simulated robotic arm. The real-time operation of the berthing simulator is briefly described.

STS-46 crewmembers during water egress training in JSC's WETF Bldg 29

NASA Technical Reports Server (NTRS)

1992-01-01

STS-46 Atlantis, Orbiter Vehicle (OV) 104, European Space Agency (ESA) Mission Specialist (MS) Claude Nicollier (left) and backup Italian Payload Specialist Umberto Guidoni, seated at the pool's side, relax before participating in a launch emergency egress (bailout) simulation in JSC's Weightless Environment Training Facility (WETF) Bldg 29. The two participants are wearing launch and entry suits (LESs) during the pretest briefing.

STS-47 backup payload specialists participate in JSC WETF bailout exercise

NASA Technical Reports Server (NTRS)

1992-01-01

STS-47 Endeavour, Orbiter Vehicle (OV) 105, backup payload specialists (left to right) Chiaki Naito-Mukai, Takao Doi, and Stan Koszelak, wearing launch and entry suits, sit on the poolside in JSC's Weightless Environment Training Facility (WETF) Bldg 29. These alternates are waiting to participate launch emergency egress (bailout) exercises. The training is conducted in the WETF pool to simulate a water landing.

STS-46 Payload Specialist Malerba in JSC's WETF pool during egress training

NASA Technical Reports Server (NTRS)

1992-01-01

STS-46 Atlantis, Orbiter Vehicle (OV) 104, Italian Payload Specialist Franco Malerba, wearing launch and entry suit (LES) and clamshell helmet, laughes as he floats in JSC's Weightless Environment Training Facility (WETF) Bldg 29 pool. Malerba's flotation vest (life jacket) and two SCUBA-equipped divers keep him afloat after he was dropped into the pool during a launch emergency egress simulation.

STS-52 Commander Wetherbee floats in life raft during JSC bailout exercises

NASA Technical Reports Server (NTRS)

1992-01-01

STS-52 Columbia, Orbiter Vehicle (OV) 102, Commander James D. Wetherbee, wearing launch and entry suit (LES) and launch and entry helmet (LEH), floats in single person life raft during emergency egress (bailout) training exercises in JSC's Weightless Environment Training Facility (WETF) Bldg 29 pool. The bailout exercises utilize the WETF's 25-foot deep pool as the ocean for this water landing simulation.

Space dust and debris; Proceedings of the Topical Meeting of the Interdisciplinary Scientific Commission B (Meetings B2, B3, and B5) of the COSPAR 28th Plenary Meeting, The Hague, Netherlands, June 25-July 6, 1990

NASA Technical Reports Server (NTRS)

Kessler, D. J. (Editor); Zarnecki, J. C. (Editor); Matson, D. L. (Editor)

1991-01-01

The present conference on space dust and debris encompasses orbital debris, in situ measurements and laboratory analysis of space-dust particles, comparative studies of comets, asteroids, and dust, the protection and maneuvering of spacecraft in space-debris environments, and the out-of-elliptic distribution of interplanetary dust derived from near-earth flux. Specific issues addressed include asteroid taxonomy, the optical properties of dust from cometary and interplanetary grains, light scattering by rough surfaces on asteroidal/lunar regoliths, and the first results of particulate impacts and foil perforations on the Long Duration Exposure Facility. Also addressed are collision probability and spacecraft disposition in the geostationary orbit, a flash on the moon caused by orbital debris, the limits of population growth in low earth orbit due to collisional cascading, and the simulation of cosmic man-made dust effects on space-vehicle elements in rocket and laboratory experiments.

A Physical Model of the Proton Radiation Belts of Jupiter inside Europa's Orbit

NASA Astrophysics Data System (ADS)

Nénon, Q.; Sicard, A.; Kollmann, P.; Garrett, H. B.; Sauer, S. P. A.; Paranicas, C.

2018-05-01

A physical model of the Jovian trapped protons with kinetic energies higher than 1 MeV inward of the orbit of the icy moon Europa is presented. The model, named Salammbô, takes into account the radial diffusion process, the absorption effect of the Jovian moons, and the Coulomb collisions and charge exchanges with the cold plasma and neutral populations of the inner Jovian magnetosphere. Preliminary modeling of the wave-particle interaction with electromagnetic ion cyclotron waves near the moon Io is also performed. Salammbô is validated against in situ proton measurements of Pioneer 10, Pioneer 11, Voyager 1, Galileo Probe, and Galileo Orbiter. A prominent feature of the MeV proton intensity distribution in the modeled area is the 2 orders of magnitude flux depletion observed in MeV measurements near the orbit of Io. Our simulations reveal that this is not due to direct interactions with the moon or its neutral environment but results from scattering of the protons by electromagnetic ion cyclotron waves.

Research on liquid sloshing performance in vane type tank under microgravity

NASA Astrophysics Data System (ADS)

Hu, Q.; Li, Y.; Liu, J. T.; Liang, J. Q.

2016-05-01

Propellant management device (PMD) in vane type tank mainly comprises of vane type structure parts, whose performance of restraining liquid sloshing should satisfy spacecraft requirements of high stabilization and fast orbital maneuver. Aiming at liquid sloshing performance in vane type tank under microgravity environment, gas-liquid flow model based on the volume of fluid (VOF) method was put forward, and via numerical simulation liquid sloshing performances of vane type PMD with anti-sloshing baffles and without anti-sloshing baffles in microgravity were analyzed and compared. Simulation results reveal that liquid sloshing performance of vane type PMD with anti-sloshing baffles is markedly superior vane type PMD without anti-sloshing baffles and the baffles make liquid surface become stable fast. Then by comparing between results of microgravity experiments and results of numerical simulations, they are very similar. According to present research, vane type PMD with antisloshing baffles has better effects on restraining liquid sloshing and is able to restrain observably propellant sloshing in tanks in order to satisfy spacecraft requirements of high stabilization and fast orbital maneuver.

An Integrated Approach to Modeling Solar Electric Propulsion Vehicles During Long Duration, Near-Earth Orbit Transfers

NASA Technical Reports Server (NTRS)

Smith, David A.; Hojnicki, Jeffrey S.; Sjauw, Waldy K.

2014-01-01

Recent NASA interest in utilizing solar electronic propulsion (SEP) technology to transfer payloads, e.g. from low-Earth orbit (LEO) to higher energy geostationary-Earth orbit (GEO) or to Earth escape, has necessitated the development of high fidelity SEP vehicle models and simulations. These models and simulations need to be capable of capturing vehicle dynamics and sub-system interactions experienced during the transfer trajectories which are typically accomplished with continuous-burn (potentially interrupted by solar eclipse), long duration "spiral out" maneuvers taking several months or more to complete. This paper presents details of an integrated simulation approach achieved by combining a high fidelity vehicle simulation code with a detailed solar array model. The combined simulation tool gives researchers the functionality to study the integrated effects of various vehicle sub-systems (e.g. vehicle guidance, navigation and control (GN&C), electric propulsion system (EP)) with time varying power production. Results from a simulation model of a vehicle with a 50 kW class SEP system using the integrated tool are presented and compared to the results from another simulation model employing a 50 kW end-of-life (EOL) fixed power level assumption. These models simulate a vehicle under three degree of freedom dynamics (i.e. translational dynamics only) and include the effects of a targeting guidance algorithm (providing a "near optimal" transfer) during a LEO to near Earth escape (C (sub 3) = -2.0 km (sup 2) / sec (sup -2) spiral trajectory. The presented results include the impact of the fully integrated, time-varying solar array model (e.g. cumulative array degradation from traversing the Van Allen belts, impact of solar eclipses on the vehicle and the related temperature responses in the solar arrays due to operating in the Earth's thermal environment, high fidelity array power module, etc.); these are used to assess the impact on vehicle performance (i.e. propellant consumption) and transit times.

An intelligent robot for helping astronauts

NASA Technical Reports Server (NTRS)

Erickson, J. D.; Grimm, K. A.; Pendleton, T. W.

1994-01-01

This paper describes the development status of a prototype supervised intelligent robot for space application for purposes of (1) helping the crew of a spacecraft such as the Space Station with various tasks, such as holding objects and retrieving/replacing tools and other objects from/into storage, and (2) for purposes of retrieving detached objects, such as equipment or crew, that have become separated from their spacecraft. In addition to this set of tasks in this low-Earth-orbiting spacecraft environment, it is argued that certain aspects of the technology can be viewed as generic in approach, thereby offering insight into intelligent robots for other tasks and environments. Candidate software architectures and their key technical issues which enable real work in real environments to be accomplished safely and robustly are addressed. Results of computer simulations of grasping floating objects are presented. Also described are characterization results on the usable reduced gravity environment in an aircraft flying parabola (to simulate weightlessness) and results on hardware performance there. These results show it is feasible to use that environment for evaluative testing of dexterous grasping based on real-time vision of freely rotating and translating objects.

Materials selection for long life in LEO: A critical evaluation of atomic oxygen testing with thermal atom systems

NASA Technical Reports Server (NTRS)

Koontz, S. L.; Kuminecz, J.; Leger, L.; Nordine, P.

1988-01-01

The use of thermal atom test methods as a materials selection and screening technique for low-Earth orbit (LEO) spacecraft is critically evaluated. The chemistry and physics of thermal atom environments are compared with the LEO environment. The relative reactivities of a number of materials determined to be in thermal atom environments are compared to those observed in LEO and in high quality LEO simulations. Reaction efficiencies measured in a new type of thermal atom apparatus are one-hundredth to one-thousandth those observed in LEO, and many materials showing nearly identical reactivities in LEO show relative reactivities differing by as much as a factor of 8 in thermal atom systems. A simple phenomenological kinetic model for the reaction of oxygen atoms with organic materials can be used to explain the differences in reactivity in different environments. Certain specific thermal test environments can be used as reliable materials screening tools. Using thermal atom methods to predict material lifetime in LEO requires direct calibration of the method against LEO data or high quality simulation data for each material.

Space Shuttle Projects

NASA Image and Video Library

1984-04-01

The Long Duration Exposure Facility (LDEF) was designed by the Marshall Space Flight Center (MSFC) to test the performance of spacecraft materials, components, and systems that have been exposed to the environment of micrometeoroids and space debris for an extended period of time. The LDEF proved invaluable to the development of future spacecraft and the International Space Station (ISS). The LDEF carried 57 science and technology experiments, the work of more than 200 investigators. MSFC`s experiments included: Trapped Proton Energy Determination to determine protons trapped in the Earth's magnetic field and the impact of radiation particles; Linear Energy Transfer Spectrum Measurement Experiment which measures the linear energy transfer spectrum behind different shielding configurations; Atomic oxygen-Simulated Out-gassing, an experiment that exposes thermal control surfaces to atomic oxygen to measure the damaging out-gassed products; Thermal Control Surfaces Experiment to determine the effects of the near-Earth orbital environment and the shuttle induced environment on spacecraft thermal control surfaces; Transverse Flat-Plate Heat Pipe Experiment, to evaluate the zero-gravity performance of a number of transverse flat plate heat pipe modules and their ability to transport large quantities of heat; Solar Array Materials Passive LDEF Experiment to examine the effects of space on mechanical, electrical, and optical properties of lightweight solar array materials; and the Effects of Solar Radiation on Glasses. Launched aboard the Space Shuttle Orbiter Challenger's STS-41C mission April 6, 1984, the LDEF remained in orbit for five years until January 1990 when it was retrieved by the Space Shuttle Orbiter Columbia STS-32 mission and brought back to Earth for close examination and analysis.

Long Duration Exposure Facility (LDEF)

NASA Technical Reports Server (NTRS)

1984-01-01

The Long Duration Exposure Facility (LDEF) was designed by the Marshall Space Flight Center (MSFC) to test the performance of spacecraft materials, components, and systems that have been exposed to the environment of micrometeoroids and space debris for an extended period of time. The LDEF proved invaluable to the development of future spacecraft and the International Space Station (ISS). The LDEF carried 57 science and technology experiments, the work of more than 200 investigators. MSFC`s experiments included: Trapped Proton Energy Determination to determine protons trapped in the Earth's magnetic field and the impact of radiation particles; Linear Energy Transfer Spectrum Measurement Experiment which measures the linear energy transfer spectrum behind different shielding configurations; Atomic oxygen-Simulated Out-gassing, an experiment that exposes thermal control surfaces to atomic oxygen to measure the damaging out-gassed products; Thermal Control Surfaces Experiment to determine the effects of the near-Earth orbital environment and the shuttle induced environment on spacecraft thermal control surfaces; Transverse Flat-Plate Heat Pipe Experiment, to evaluate the zero-gravity performance of a number of transverse flat plate heat pipe modules and their ability to transport large quantities of heat; Solar Array Materials Passive LDEF Experiment to examine the effects of space on mechanical, electrical, and optical properties of lightweight solar array materials; and the Effects of Solar Radiation on Glasses. Launched aboard the Space Shuttle Orbiter Challenger's STS-41C mission April 6, 1984, the LDEF remained in orbit for five years until January 1990 when it was retrieved by the Space Shuttle Orbiter Columbia STS-32 mission and brought back to Earth for close examination and analysis.

Oxidation and protection of fiberglass-epoxy composite masts for photovoltaic arrays in the low Earth orbital environment

NASA Technical Reports Server (NTRS)

Rutledge, Sharon K.; Paulsen, Phillip E.; Brady, Joyce A.; Ciancone, Michael L.

1988-01-01

Fiberglass-epoxy composites are considered for use as structural members for the mast of the space station solar array panel. The low Earth orbital environment in which space station is to operate is composed mainly of atomic oxygen, which has been shown to cause erosion of many organic materials and some metals. Ground based testing in a plasma asher was performed to determine the extent of degradation of fiberglass-epoxy composites when exposed to a simulated atomic oxygen environment. During exposure, the epoxy at the surface of the composite was oxidized, exposing individual glass fibers which could easily be removed. Several methods of protecting the composite were evaluated in an atomic oxygen environment and with thermal cycling and flexing. The protection techniques evaluated to date include an aluminum braid covering, an indium-tin eutectic and a silicone based paint. The open aluminum braid offered little protection while the CV-1144 coating offered some initial protection against atomic oxygen, but appears to develop cracks which accelerate degradation when flexed. Coatings such as the In-Sn eutectic may provide adequate protection by containing the glass fibers even though mass loss still occurs.

Age Induced Effects on ESD Characteristics of Solar Array Coupons After Combined Space Environmental Exposures

NASA Technical Reports Server (NTRS)

Wright, Kenneth H.; Schneider, Todd A.; Vaughn, Jason A.; Hoang, Bao; Funderburk, Victor V.; Wong, Frankie; Gardiner, George

2012-01-01

A set of multi-junction GaAs/Ge solar array test coupons provided by Space Systems/Loral were subjected to a sequence of 5-year increments of combined space environment exposure tests. The test coupons capture an integrated design intended for use in a geosynchronous (GEO) space environment. A key component of this test campaign is performing electrostatic discharge (ESD) tests in the inverted gradient mode. The protocol of the ESD tests is based on the ISO standard for ESD testing on solar array panels [ISO-11221]. The test schematic in the ISO reference has been modified with Space System/Loral designed circuitry to better simulate the on-orbit operational conditions of its solar array design. Part of the modified circuitry is to simulate a solar array panel coverglass flashover discharge. All solar array coupons used in the test campaign consist of four cells constructed to form two strings. The ESD tests were performed at the beginning-of-life (BOL) and at each 5-year environment exposure point until end-of-life (EOL) at 15 years. The space environmental exposure sequence consisted of ultra-violet radiation, electron/proton particle radiation, thermal cycling, and Xenon ion thruster plume erosion. This paper describes the ESD test setup and the importance of the electrical test design in simulating the on-orbit operational conditions. Arc inception voltage results along with ESD test behavior from the BOL condition through the 15th year age condition are discussed. In addition, results from a Xenon plasma plume exposure test with an EOL coupon under the full ESD test condition will be discussed.

Forming Circumbinary Planets: N-body Simulations of Kepler-34

NASA Astrophysics Data System (ADS)

Lines, S.; Leinhardt, Z. M.; Paardekooper, S.; Baruteau, C.; Thebault, P.

2014-02-01

Observations of circumbinary planets orbiting very close to the central stars have shown that planet formation may occur in a very hostile environment, where the gravitational pull from the binary should be very strong on the primordial protoplanetary disk. Elevated impact velocities and orbit crossings from eccentricity oscillations are the primary contributors to high energy, potentially destructive collisions that inhibit the growth of aspiring planets. In this work, we conduct high-resolution, inter-particle gravity enabled N-body simulations to investigate the feasibility of planetesimal growth in the Kepler-34 system. We improve upon previous work by including planetesimal disk self-gravity and an extensive collision model to accurately handle inter-planetesimal interactions. We find that super-catastrophic erosion events are the dominant mechanism up to and including the orbital radius of Kepler-34(AB)b, making in situ growth unlikely. It is more plausible that Kepler-34(AB)b migrated from a region beyond 1.5 AU. Based on the conclusions that we have made for Kepler-34, it seems likely that all of the currently known circumbinary planets have also migrated significantly from their formation location with the possible exception of Kepler-47(AB)c.

Quantifying and Improving International Space Station Survivability Following Orbital Debris Penetration

NASA Technical Reports Server (NTRS)

Williamsen, Joel; Evans, Hilary; Bohl, Bill; Evans, Steven; Parker, Nelson (Technical Monitor)

2001-01-01

The increase of the orbital debris environment in low-earth orbit has prompted NASA to develop analytical tools for quantifying and lowering the likelihood of crew loss following orbital debris penetration of the International Space Station (ISS). NASA uses the Manned Spacecraft and Crew Survivability (MSCSurv) computer program to simulate the events that may cause crew loss following orbital debris penetration of ISS manned modules, including: (1) critical cracking (explosive decompression) of the module; (2) critical external equipment penetration (such as hydrazine and high pressure tanks); (3) critical internal system penetration (guidance, control, and other vital components); (4) hazardous payload penetration (furnaces, pressure bottles, and toxic substances); (5) crew injury (from fragments, overpressure, light flash, and temperature rise); (6) hypoxia from loss of cabin pressure; and (7) thrust from module hole causing high angular velocity (occurring only when key Guidance, Navigation, and Control (GN&C) equipment is damaged) and, thus, preventing safe escape vehicle (EV) departure. MSCSurv is also capable of quantifying the 'end effects' of orbital debris penetration, such as the likelihood of crew escape, the probability of each module depressurizing, and late loss of station control. By quantifying these effects (and their associated uncertainties), NASA is able to improve the likelihood of crew survivability following orbital debris penetration due to improved crew operations and internal designs.

Space Operations Analysis Using the Synergistic Engineering Environment

NASA Technical Reports Server (NTRS)

Angster, Scott; Brewer, Laura

2002-01-01

The Synergistic Engineering Environment has been under development at the NASA Langley Research Center to aid in the understanding of the operations of spacecraft. This is accomplished through the integration of multiple data sets, analysis tools, spacecraft geometric models, and a visualization environment to create an interactive virtual simulation of the spacecraft. Initially designed to support the needs of the International Space Station, the SEE has broadened the scope to include spacecraft ranging from low-earth orbit to deep space missions. Analysis capabilities within the SEE include rigid body dynamics, kinematics, orbital mechanics, and payload operations. This provides the user the ability to perform real-time interactive engineering analyses in areas including flight attitudes and maneuvers, visiting vehicle docking scenarios, robotic operations, plume impingement, field of view obscuration, and alternative assembly configurations. The SEE has been used to aid in the understanding of several operational procedures related to the International Space Station. This paper will address the capabilities of the first build of the SEE, present several use cases of the SEE, and discuss the next build of the SEE.

UAV-guided navigation for ground robot tele-operation in a military reconnaissance environment.

PubMed

Chen, Jessie Y C

2010-08-01

A military reconnaissance environment was simulated to examine the performance of ground robotics operators who were instructed to utilise streaming video from an unmanned aerial vehicle (UAV) to navigate his/her ground robot to the locations of the targets. The effects of participants' spatial ability on their performance and workload were also investigated. Results showed that participants' overall performance (speed and accuracy) was better when she/he had access to images from larger UAVs with fixed orientations, compared with other UAV conditions (baseline- no UAV, micro air vehicle and UAV with orbiting views). Participants experienced the highest workload when the UAV was orbiting. Those individuals with higher spatial ability performed significantly better and reported less workload than those with lower spatial ability. The results of the current study will further understanding of ground robot operators' target search performance based on streaming video from UAVs. The results will also facilitate the implementation of ground/air robots in military environments and will be useful to the future military system design and training community.

Orbital Electron Capture Rates in Extreme Astrophysical Environments

NASA Astrophysics Data System (ADS)

Martin, Matthew; McDonald, William; Leach, Kyle

2017-09-01

In an attempt to better understand EC decay rates in hot environments, we have developed a program to examine and parse all evaluated atomic and nuclear data. Taking into account the effects of ionization on accessible decay states and electron capture probabilities, half lives across the nuclear chart can be investigated without the need for theoretical estimates. Part of the ongoing project will include isolating stable isotopes that become unstable due to ionization and estimating their stability in these new environments. In addition, we hope to account for a thermal population of excited states to better simulate these environments. This should aide in the complete understanding of nuclear processes in these extreme astrophysical environments. This work is supported in part by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics.

Satellite quenching time-scales in clusters from projected phase space measurements matched to simulated orbits

NASA Astrophysics Data System (ADS)

Oman, Kyle A.; Hudson, Michael J.

2016-12-01

We measure the star formation quenching efficiency and time-scale in cluster environments. Our method uses N-body simulations to estimate the probability distribution of possible orbits for a sample of observed Sloan Digital Sky Survey galaxies in and around clusters based on their position and velocity offsets from their host cluster. We study the relationship between their star formation rates and their likely orbital histories via a simple model in which star formation is quenched once a delay time after infall has elapsed. Our orbit library method is designed to isolate the environmental effect on the star formation rate due to a galaxy's present-day host cluster from `pre-processing' in previous group hosts. We find that quenching of satellite galaxies of all stellar masses in our sample (109-10^{11.5}M_{⊙}) by massive (> 10^{13} M_{⊙}) clusters is essentially 100 per cent efficient. Our fits show that all galaxies quench on their first infall, approximately at or within a Gyr of their first pericentric passage. There is little variation in the onset of quenching from galaxy-to-galaxy: the spread in this time is at most ˜2 Gyr at fixed M*. Higher mass satellites quench earlier, with very little dependence on host cluster mass in the range probed by our sample.

The use of real-time, hardware-in-the-loop simulation in the design and development of the new Hughes HS601 spacecraft attitude control system

NASA Technical Reports Server (NTRS)

Slafer, Loren I.

1989-01-01

Realtime simulation and hardware-in-the-loop testing is being used extensively in all phases of the design, development, and testing of the attitude control system (ACS) for the new Hughes HS601 satellite bus. Realtime, hardware-in-the-loop simulation, integrated with traditional analysis and pure simulation activities is shown to provide a highly efficient and productive overall development program. Implementation of high fidelity simulations of the satellite dynamics and control system algorithms, capable of real-time execution (using applied Dynamics International's System 100), provides a tool which is capable of being integrated with the critical flight microprocessor to create a mixed simulation test (MST). The MST creates a highly accurate, detailed simulated on-orbit test environment, capable of open and closed loop ACS testing, in which the ACS design can be validated. The MST is shown to provide a valuable extension of traditional test methods. A description of the MST configuration is presented, including the spacecraft dynamics simulation model, sensor and actuator emulators, and the test support system. Overall system performance parameters are presented. MST applications are discussed; supporting ACS design, developing on-orbit system performance predictions, flight software development and qualification testing (augmenting the traditional software-based testing), mission planning, and a cost-effective subsystem-level acceptance test. The MST is shown to provide an ideal tool in which the ACS designer can fly the spacecraft on the ground.

An Overview of NASA's Oribital Debris Environment Model

NASA Technical Reports Server (NTRS)

Matney, Mark

2010-01-01

Using updated measurement data, analysis tools, and modeling techniques; the NASA Orbital Debris Program Office has created a new Orbital Debris Environment Model. This model extends the coverage of orbital debris flux throughout the Earth orbit environment, and includes information on the mass density of the debris as well as the uncertainties in the model environment. This paper will give an overview of this model and its implications for spacecraft risk analysis.

LDEF data: Comparisons with existing models

NASA Astrophysics Data System (ADS)

Coombs, Cassandra R.; Watts, Alan J.; Wagner, John D.; Atkinson, Dale R.

1993-04-01

The relationship between the observed cratering impact damage on the Long Duration Exposure Facility (LDEF) versus the existing models for both the natural environment of micrometeoroids and the man-made debris was investigated. Experimental data was provided by several LDEF Principal Investigators, Meteoroid and Debris Special Investigation Group (M&D SIG) members, and by the Kennedy Space Center Analysis Team (KSC A-Team) members. These data were collected from various aluminum materials around the LDEF satellite. A PC (personal computer) computer program, SPENV, was written which incorporates the existing models of the Low Earth Orbit (LEO) environment. This program calculates the expected number of impacts per unit area as functions of altitude, orbital inclination, time in orbit, and direction of the spacecraft surface relative to the velocity vector, for both micrometeoroids and man-made debris. Since both particle models are couched in terms of impact fluxes versus impactor particle size, and much of the LDEF data is in the form of crater production rates, scaling laws have been used to relate the two. Also many hydrodynamic impact computer simulations were conducted, using CTH, of various impact events, that identified certain modes of response, including simple metallic target cratering, perforations and delamination effects of coatings.

Understanding Skill in EVA Mass Handling. Volume 1; Theoretical and Operational Foundations

NASA Technical Reports Server (NTRS)

Riccio, Gary; McDonald, Vernon; Peters, Brian; Layne, Charles; Bloomberg, Jacob

1997-01-01

This report describes the theoretical and operational foundations for our analysis of skill in extravehicular mass handling. A review of our research on postural control, human-environment interactions, and exploratory behavior in skill acquisition is used to motivate our analysis. This scientific material is presented within the context of operationally valid issues concerning extravehicular mass handling. We describe the development of meaningful empirical measures that are relevant to a special class of nested control systems: manual interactions between an individual and the substantial environment. These measures are incorporated into a unique empirical protocol implemented on NASA's principal mass handling simulator, the precision air-bearing floor, in order to evaluate skill in extravehicular mass handling. We discuss the components of such skill with reference to the relationship between postural configuration and controllability of an orbital replacement unit, the relationship between orbital replacement unit control and postural stability, the relationship between antecedent and consequent movements of an orbital replacement unit, and the relationship between antecedent and consequent postural movements. Finally, we describe our expectations regarding the operational relevance of the empirical results as it pertains to extravehicular activity tools, training, monitoring, and planning.

LDEF data: Comparisons with existing models

NASA Technical Reports Server (NTRS)

Coombs, Cassandra R.; Watts, Alan J.; Wagner, John D.; Atkinson, Dale R.

1993-01-01

The relationship between the observed cratering impact damage on the Long Duration Exposure Facility (LDEF) versus the existing models for both the natural environment of micrometeoroids and the man-made debris was investigated. Experimental data was provided by several LDEF Principal Investigators, Meteoroid and Debris Special Investigation Group (M&D SIG) members, and by the Kennedy Space Center Analysis Team (KSC A-Team) members. These data were collected from various aluminum materials around the LDEF satellite. A PC (personal computer) computer program, SPENV, was written which incorporates the existing models of the Low Earth Orbit (LEO) environment. This program calculates the expected number of impacts per unit area as functions of altitude, orbital inclination, time in orbit, and direction of the spacecraft surface relative to the velocity vector, for both micrometeoroids and man-made debris. Since both particle models are couched in terms of impact fluxes versus impactor particle size, and much of the LDEF data is in the form of crater production rates, scaling laws have been used to relate the two. Also many hydrodynamic impact computer simulations were conducted, using CTH, of various impact events, that identified certain modes of response, including simple metallic target cratering, perforations and delamination effects of coatings.

Simulation and Analyses of Multi-Body Separation in Launch Vehicle Staging Environment

NASA Technical Reports Server (NTRS)

Pamadi, Bandu N.; Hotchko, Nathaniel J.; Samareh, Jamshid; Covell, Peter F.; Tartabini, Paul V.

2006-01-01

The development of methodologies, techniques, and tools for analysis and simulation of multi-body separation is critically needed for successful design and operation of next generation launch vehicles. As a part of this activity, ConSep simulation tool is being developed. ConSep is a generic MATLAB-based front-and-back-end to the commercially available ADAMS. solver, an industry standard package for solving multi-body dynamic problems. This paper discusses the 3-body separation capability in ConSep and its application to the separation of the Shuttle Solid Rocket Boosters (SRBs) from the External Tank (ET) and the Orbiter. The results are compared with STS-1 flight data.

In situ Orbit Extraction from Live, High Precision Collisionless Simulations of Systems Formed by Cold Collapse

NASA Astrophysics Data System (ADS)

Noriega-Mendoza, H.; Aguilar, L. A.

2018-04-01

We performed high precision, N-body simulations of the cold collapse of initially spherical, collisionless systems using the GYRFALCON code of Dehnen (2000). The collapses produce very prolate spheroidal configurations. After the collapse, the systems are simulated for 85 and 170 half-mass radius dynamical timescales, during which energy conservation is better than 0.005%. We use this period to extract individual particle orbits directly from the simulations. We then use the TAXON code of Carpintero and Aguilar (1998) to classify 1 to 1.5% of the extracted orbits from our final, relaxed configurations: less than 15% are chaotic orbits, 30% are box orbits and 60% are tube orbits (long and short axis). Our goal has been to prove that direct orbit extraction is feasible, and that there is no need to "freeze" the final N-body system configuration to extract a time-independent potential.

Characterization of the catalog Fengyun-1C fragments and their long-term effect on the LEO environment

NASA Astrophysics Data System (ADS)

Liou, J.-C.

The intentional breakup of Fengyun-1C on 11 January 2007 created the most severe orbital debris cloud in history. More than 2500 large fragments were identified and tracked by the U.S. Space Surveillance Network by the end of the year. The altitude where the event occurred was probably the worst location for a major breakup in the low Earth orbit (LEO) region, since it was already highly populated with operational satellites and debris generated from previous breakups. The addition of so many fragments not only poses a realistic threat to operational satellites in the region, but also increases the instability (i.e., collision cascade effect) of the debris population there. Preliminary analysis of the large Fengyun-1C fragments indicates that their size and area-tomass ratio (A/M) distributions are very different from those of other known events. About half of the fragments appear to be composed of light-weight materials and more than 100 of them have A/M values exceeding 1 m2 /kg, consistent with thermal blanket pieces. In addition, the orbital elements of the fragments suggest non-trivial velocity gain by the fragment cloud during the impact. These important characteristics were incorporated into a numerical simulation to assess the long-term impact of the Fengyun-1C fragments to the LEO debris environment. The main objectives of the simulation were to evaluate (1) the collision probabilities between the Fengyun-1C fragments and the rest of the catalog population and (2) the collision activities and population growth in the region in the next 100 years.

Aeroheating Analysis for the Mars Reconnaissance Orbiter with Comparison to Flight Data

NASA Technical Reports Server (NTRS)

Liechty, Derek S.

2006-01-01

The aeroheating environment of the Mars Reconnaissance Orbiter (MRO) has been analyzed using the Direct Simulation Monte Carlo and free-molecular techniques. The results of these analyses were used to develop an aeroheating database to be used for the pre-flight planning and the in-flight operations support for the aerobraking phase of the MRO mission. The aeroheating predictions calculated for the MRO include the heat transfer coefficient (C(H)) over a range of angles-of-attack, side-slip angles, and number densities. The effects of flow chemistry were also investigated. Flight heat flux data deduced from surface temperature sensors have been compared to pre-flight predictions and agree favorably.

Integrating Existing Simulation Components into a Cohesive Simulation System

NASA Technical Reports Server (NTRS)

McLaughlin, Brian J.; Barrett, Larry K.

2012-01-01

A tradition of leveraging the re-use of components to help manage costs has evolved in the development of complex system. This tradition continues on in the Joint Polar Satellite System (JPSS) Program with the cloning of the Suomi National Polar-orbiting Partnership (NPP) satellite for the JPSS-1 mission, including the instrument complement. One benefit of re-use on a mission is the availability of existing simulation assets from the systems that were previously built. An issue arises in the continual shift of technology over a long mission, or multi-mission, lifecycle. As the missions mature, the requirements for the observatory simulations evolve. The challenge in this environment becomes re-using the existing components in that ever-changing landscape. To meet this challenge, the system must: establish an operational architecture that minimizes impacts on the implementation of individual components, consolidate the satisfaction of new high-impact requirements into system-level infrastructure, and build in a long-term view of system adaptation that spans the full lifecycle of the simulation system. The Flight Vehicle Test Suite (FVTS) within the JPSS Program is defining and executing this approach to ensure a robust simulation capability for the JPSS multi-mission environment

On Directional Measurement Representation in Orbit Determination

DTIC Science & Technology

2016-09-13

representations. The three techniques are then compared experimentally for a geostationary and a low Earth orbit satellite using simulated data to evaluate their...Earth Orbit (LEO) and a Geostationary Earth Orbit (GEO) satellite. Section IV discusses the results from the numerical simulations and finally Section V... Geostationary Earth Orbit (GEO) satellite with the initial orbital parameters shown in Table 1. Different ground sites are used for the LEO and ahttps

An Astrobiological Experiment to Explore the Habitability of Tidally Locked M-Dwarf Planets

NASA Astrophysics Data System (ADS)

Angerhausen, Daniel; Sapers, Haley; Simoncini, Eugenio; Lutz, Stefanie; Alexandre, Marcelo da Rosa; Galante, Douglas

2014-04-01

We present a summary of a three-year academic research proposal drafted during the Sao Paulo Advanced School of Astrobiology (SPASA) to prepare for upcoming observations of tidally locked planets orbiting M-dwarf stars. The primary experimental goal of the suggested research is to expose extremophiles from analogue environments to a modified space simulation chamber reproducing the environmental parameters of a tidally locked planet in the habitable zone of a late-type star. Here we focus on a description of the astronomical analysis used to define the parameters for this climate simulation.

An orbit simulation study of a geopotential research mission including satellite-to-satellite tracking and disturbance compensation systems

NASA Technical Reports Server (NTRS)

Antreasian, Peter G.

1988-01-01

Two orbit simulations, one representing the actual Geopotential Research Mission (GRM) orbit and the other representing the orbit estimated from orbit determination techniques, are presented. A computer algorithm was created to simulate GRM's drag compensation mechanism so the fuel expenditure and proof mass trajectories relative to the spacecraft centroid could be calculated for the mission. The results of the GRM DISCOS simulation demonstrated that the spacecraft can essentially be drag-free. The results showed that the centroid of the spacecraft can be controlled so that it will not deviate more than 1.0 mm in any direction from the centroid of the proof mass.

The international environment UNISPACE '82 and the ITU: A relationship between orbit-spectrum resource allocation and orbital debris

NASA Technical Reports Server (NTRS)

Olmstead, D.

1985-01-01

The 1985 Space WARC will examine and potentially modify the current geostationary orbit spectrum resource allocation methodology. Discussions in this international political environment could likely associate the geostationary orbital debris issue with the politicized issue of orbit spectrum allocation.

Single-Frequency GPS Relative Navigation in a High Ionosphere Orbital Environment

NASA Technical Reports Server (NTRS)

Conrad, Patrick R.; Naasz, Bo J.

2007-01-01

The Global Positioning System (GPS) provides a convenient source for space vehicle relative navigation measurements, especially for low Earth orbit formation flying and autonomous rendezvous mission concepts. For single-frequency GPS receivers, ionospheric path delay can be a significant error source if not properly mitigated. In particular, ionospheric effects are known to cause significant radial position error bias and add dramatically to relative state estimation error if the onboard navigation software does not force the use of measurements from common or shared GPS space vehicles. Results from GPS navigation simulations are presented for a pair of space vehicles flying in formation and using GPS pseudorange measurements to perform absolute and relative orbit determination. With careful measurement selection techniques relative state estimation accuracy to less than 20 cm with standard GPS pseudorange processing and less than 10 cm with single-differenced pseudorange processing is shown.

Aeroheating Analysis for the Mars Reconnaissance Orbiter with Comparison to Flight Data

NASA Technical Reports Server (NTRS)

Liechty, Derek S.

2007-01-01

The aeroheating environment of the Mars Reconnaissance Orbiter (MRO) has been analyzed using the direct simulation Monte Carlo and free-molecular techniques. The results of these analyses were used to develop an aeroheating database to be used for the preflight planning and the in-flight operations support for the aerobraking phase of the MRO mission. The aeroheating predictions calculated for the MRO include the heat transfer coefficient (CH) over a range of angles-of-attack, sideslip angles, and number densities. The effects of flow chemistry, surface temperature, and surface grid resolution were also investigated to determine the aeroheating database uncertainties. Flight heat flux data has been calculated from surface temperature sensor data returned to Earth from the MRO in orbit around Mars during the aerobraking phase of its mission. The heat flux data have been compared to the aeroheating database and agree favorably.

Fuzzy logic in autonomous orbital operations

NASA Technical Reports Server (NTRS)

Lea, Robert N.; Jani, Yashvant

1991-01-01

Fuzzy logic can be used advantageously in autonomous orbital operations that require the capability of handling imprecise measurements from sensors. Several applications are underway to investigate fuzzy logic approaches and develop guidance and control algorithms for autonomous orbital operations. Translational as well as rotational control of a spacecraft have been demonstrated using space shuttle simulations. An approach to a camera tracking system has been developed to support proximity operations and traffic management around the Space Station Freedom. Pattern recognition and object identification algorithms currently under development will become part of this camera system at an appropriate level in the future. A concept to control environment and life support systems for large Lunar based crew quarters is also under development. Investigations in the area of reinforcement learning, utilizing neural networks, combined with a fuzzy logic controller, are planned as a joint project with the Ames Research Center.

Surface Penetrating Radar Simulations for Europa

NASA Technical Reports Server (NTRS)

Markus, T.; Gogineni, S. P.; Green, J. L.; Fung, S. F.; Cooper, J. F.; Taylor, W. W. L.; Garcia, L.; Reinisch, B. W.; Song, P.; Benson, R. F.

2004-01-01

The space environment above the icy surface of Europa is a source of radio noise in this frequency range from natural sources in the Jovian magnetosphere. The ionospheric and magnetospheric plasma environment of Europa affects propagation of transmitted and return signals between the spacecraft and the solid surface in a frequency-dependent manner. The ultimate resolution of the subsurface sounding measurements will be determined, in part, by a capability to mitigate these effects. We discuss an integrated multi-frequency approach to active radio sounding of the Europa ionospheric and local magnetospheric environments, based on operational experience from the Radio Plasma Imaging @PI) experiment on the IMAGE spacecraft in Earth orbit, in support of the subsurface measurement objectives.

Large space system: Charged particle environment interaction technology

NASA Technical Reports Server (NTRS)

Stevens, N. J.; Roche, J. C.; Grier, N. T.

1979-01-01

Large, high voltage space power systems are proposed for future space missions. These systems must operate in the charged-particle environment of space and interactions between this environment and the high voltage surfaces are possible. Ground simulation testing indicated that dielectric surfaces that usually surround biased conductors can influence these interactions. For positive voltages greater than 100 volts, it has been found that the dielectrics contribute to the current collection area. For negative voltages greater than-500 volts, the data indicates that the dielectrics contribute to discharges. A large, high-voltage power system operating in geosynchronous orbit was analyzed. Results of this analysis indicate that very strong electric fields exist in these power systems.

Is ram-pressure stripping an efficient mechanism to remove gas in galaxies?

NASA Astrophysics Data System (ADS)

Quilis, Vicent; Planelles, Susana; Ricciardelli, Elena

2017-07-01

We study how the gas in a sample of galaxies (M* > 109 M⊙) in clusters, obtained in a cosmological simulation, is affected by the interaction with the intracluster medium (ICM). The dynamical state of each elemental parcel of gas is studied using the total energy. At z ˜ 2, the galaxies in the simulation are evenly distributed within clusters, later moving towards more central locations. In this process, gas from the ICM is accreted and mixed with the gas in the galactic halo. Simultaneously, the interaction with the environment removes part of the gas. A characteristic stellar mass around M* ˜ 1010 M⊙ appears as a threshold marking two differentiated behaviours. Below this mass, galaxies are located at the external part of clusters and have eccentric orbits. The effect of the interaction with the environment is marginal. Above, galaxies are mainly located at the inner part of clusters with mostly radial orbits with low velocities. In these massive systems, part of the gas, strongly correlated with the stellar mass of the galaxy, is removed. The amount of removed gas is subdominant compared with the quantity of retained gas, which is continuously influenced by the hot gas coming from the ICM. The analysis of individual galaxies reveals the existence of a complex pattern of flows, turbulence and a constant fuelling of gas to the hot corona from the ICM, which could mean that the global effect of the interaction of galaxies with their environment is substantially less dramatic than previously expected.

The Hydrodynamics of Galaxy Transformation in Extreme Cluster Environments

NASA Astrophysics Data System (ADS)

Vijayaraghavan, Rukmani

2017-08-01

Cluster of galaxies are hostile environments. Infalling cluster galaxies are stripped of their dark matter, stars, and hot and cold interstellar medium gas. The ISM, in addition to tidal and ram pressure stripping, can evaporate due to thermal conduction. Gas loss and the subsequent suppression of star formation is not straightforward: magnetic fields in the ISM and ICM shield galaxies and their stripped tails from shear instabilities and conduction, radiative cooling can inhibit gas loss, and feedback from stars and AGN can replenish the ISM. While there is observational evidence that these processes operate, a theoretical understanding of the physics controlling the energy cycle in cluster galaxies remains elusive. Additionally, galaxies have a significant impact on ICM evolution: orbiting galaxies stir up and stretch ICM magnetic field lines, inject turbulence into the ICM via their wakes and g-waves, and infuse metals into the ICM. Quantifying the balance between processes that remove, retain, and replenish the ISM, and the impact of galaxies on the ICM require specialized hydrodynamic simulations of the cluster environment and its galaxies. I will present results from some of these simulations that include ram pressure stripping of galaxies' hot ISM, the effect of magnetic fields on this process, and the effectiveness of isotropic and anisotropic thermal conduction in removing and retaining the ISM. I will also quantify magnetic field amplification and turbulence injection due to orbiting galaxies, and implications for X-ray and radio observations and measurements of galactic coronae, tails, magnetic fields, and turbulence.

STS-26 Pilot Covey floats in life raft during JSC WETF exercises

NASA Image and Video Library

1988-07-08

S88-42425 (20 July 1988) --- STS-26 Discovery, Orbiter Vehicle (OV) 103, Pilot Richard O. Covey, wearing the newly designed launch and entry suit (LES), floats in single-occupant life raft in JSC Weightless Environment Training Facility (WETF) Bldg 29 pool. The simulation of the escape and rescue operations utilized the crew escape system (CES) pole method of egress from the Space Shuttle.

STS-45 backup Payload Specialist Chappell during water egress training at JSC

NASA Technical Reports Server (NTRS)

1991-01-01

STS-45 Atlantis, Orbiter Vehicle (OV) 104, backup Payload Specialist Charles R. Chappell, wearing launch and entry suit (LES), is suspended via his parachute harness above JSC's Weightless Environment Training Facility (WETF) Bldg 29 pool. Chappell will be dropped into the pool during the exercise which simulates a parachute landing into a body of water. SCUBA-equipped divers swimming in the pool will assist during the training.

STS-52 backup Payload Specialist Tryggvason during JSC bailout exercises

NASA Technical Reports Server (NTRS)

1992-01-01

STS-52 Columbia, Orbiter Vehicle (OV) 102, backup Payload Specialist Bjarni V. Tryggvason, wearing launch and entry suit (LES), checks his launch and entry helmet (LEH) fitting prior to participating in emergency egress (bailout) training exercises in JSC's Weightless Environment Training Facility (WETF) Bldg 29. The WETF's 25-ft deep pool will serve as the ocean during this water landing simulation. Tryggvason represents the Canadian Space Agency (CSA).

STS-45 Payload Specialist Frimout prepares for water egress training at JSC

NASA Technical Reports Server (NTRS)

1991-01-01

STS-45 Atlantis, Orbiter Vehicle (OV) 104, Payload Specialist Dirk D. Frimout, a European Space Agency (ESA) crewmember from Belgium, smiles while taking a break from water egress exercises in JSC's Weightless Environment Training Facility (WETF) Bldg 29. Frimout along with other STS-45 is participating a launch emergency egress simulation during which the crewmembers will be dropped from their parachute harnesses into the pool.

STS-26 Pilot Covey floats in life raft during JSC WETF exercises

NASA Technical Reports Server (NTRS)

1988-01-01

STS-26 Discovery, Orbiter Vehicle (OV) 103, Pilot Richard O. Covey, wearing the newly designed launch and entry suit (LES), floats in single-occupant life raft in JSC Weightless Environment Training Facility (WETF) Bldg 29 pool. Covey has paddle-like gloves on his hands. The simulation of the escape and rescue operations utilized the crew escape system (CES) pole method of egress from the Space Shuttle.

STS-46 Pilot Allen and Payload Specialist Malerba in life rafts at JSC's WEFT

NASA Technical Reports Server (NTRS)

1992-01-01

STS-46 Atlantis, Orbiter Vehicle (OV) 104, Pilot Andrew M. Allen (foreground) and Italian Payload Specialist Franco Malerba, wearing launch and entry suits (LESs) and launch and entry helmets (LEHs), float in one-person life rafts during a launch emergency egress (bailout) simulation in JSC's Weightless Environment Training Facility (WETF) Bldg 29 pool. A SCUBA-equipped diver assists in the training activity.

In-flight crew training

NASA Technical Reports Server (NTRS)

Gott, Charles; Galicki, Peter; Shores, David

1990-01-01

The Helmet Mounted Display system and Part Task Trainer are two projects currently underway that are closely related to the in-flight crew training concept. The first project is a training simulator and an engineering analysis tool. The simulator's unique helmet mounted display actually projects the wearer into the simulated environment of 3-D space. Miniature monitors are mounted in front of the wearers eyes. Partial Task Trainer is a kinematic simulator for the Shuttle Remote Manipulator System. The simulator consists of a high end graphics workstation with a high resolution color screen and a number of input peripherals that create a functional equivalent of the RMS control panel in the back of the Orbiter. It is being used in the training cycle for Shuttle crew members. Activities are underway to expand the capability of the Helmet Display System and the Partial Task Trainer.

Premission and postmission simulation studies of the foot-controlled maneuvering unit for Skylab experiment T-020. [astronaut maneuvering equipment - space environment simulation

NASA Technical Reports Server (NTRS)

Hewes, D. E.; Glover, K. E.

1975-01-01

A Skylab experiment was conducted to study the maneuvering capabilities of astronauts using a relatively simple self-locomotive device, referred to as the foot-controlled maneuvering unit, and to evaluate the effectiveness of ground-based facilities simulating the operation of this device in weightless conditions of space. Some of the special considerations given in the definition and development of the experiment as related to the two ground-based simulators are reviewed. These simulators were used to train the test subjects and to obtain baseline data which could be used for comparison with the in-flight tests that were performed inside the Skylab orbital workshop. The results of both premission and postmission tests are discussed, and subjective comparisons of the in-flight and ground-based test conditions are presented.

Estimating the Geocenter from GNSS Observations

NASA Astrophysics Data System (ADS)

Dach, Rolf; Michael, Meindl; Beutler, Gerhard; Schaer, Stefan; Lutz, Simon; Jäggi, Adrian

2014-05-01

The satellites of the Global Navigation Satellite Systems (GNSS) are orbiting the Earth according to the laws of celestial mechanics. As a consequence, the satellites are sensitive to the coordinates of the center of mass of the Earth. The coordinates of the (ground) tracking stations are referring to the center of figure as the conventional origin of the reference frame. The difference between the center of mass and center of figure is the instantaneous geocenter. Following this definition the global GNSS solutions are sensitive to the geocenter. Several studies demonstrated strong correlations of the GNSS-derived geocenter coordinates with parameters intended to absorb radiation pressure effects acting on the GNSS satellites, and with GNSS satellite clock parameters. One should thus pose the question to what extent these satellite-related parameters absorb (or hide) the geocenter information. A clean simulation study has been performed to answer this question. The simulation environment allows it in particular to introduce user-defined shifts of the geocenter (systematic inconsistencies between the satellite's and station's reference frames). These geocenter shifts may be recovered by the mentioned parameters - provided they were set up in the analysis. If the geocenter coordinates are not estimated, one may find out which other parameters absorb the user-defined shifts of the geocenter and to what extent. Furthermore, the simulation environment also allows it to extract the correlation matrix from the a posteriori covariance matrix to study the correlations between different parameter types of the GNSS analysis system. Our results show high degrees of correlations between geocenter coordinates, orbit-related parameters, and satellite clock parameters. These correlations are of the same order of magnitude as the correlations between station heights, troposphere, and receiver clock parameters in each regional or global GNSS network analysis. If such correlations are accepted in a GNSS analysis when estimating station coordinates, geocenter coordinates must be considered as mathematically estimable in a global GNSS analysis. The geophysical interpretation may of course become difficult, e.g., if insufficient orbit models are used.

Effect of the metal environment on the ferromagnetic interaction in the Co-NC-W pairs of octacyanotungstate(V)-Cobalt(II) three-dimensional networks.

PubMed

Clima, Sergiu; Hendrickx, Marc F A; Chibotaru, Liviu F; Soncini, Alessandro; Mironov, Vladimir; Ceulemans, Arnout

2007-04-02

State of the art CASSCF and CASPT2 calculations have been performed to elucidate the nature of ferromagnetism of CoII-NC-WV pairs in the three-dimensional compound [[WV(CN)2]2[(micro-CN)4CoII(H2O)2]3.4H2O]n, which has been recently synthesized and investigated by a number of experimental techniques (Herrera, J. M.; Bleuzen, A.; Dromzée, Y.; Julve, M.; Lloret, F.; Verdaguer, M. Inorg. Chem. 2003, 42, 7052-7059). In this network, the Co ions are in the high-spin (S = 3/2) state, while the single unpaired electron on the W centers occupies the lowest orbital of the dz2 type of the 5d shell. In agreement with the suggestion made by Herrera et al., we find that the ferromagnetism is due to a certain occupation scheme of the orbitals from the parent octahedral t2g shell on CoII sites, in which the orbital accommodating the unpaired electron is orthogonal to the dz2 orbitals of the surrounding W ions. We investigate the stabilization of such an orbital configuration on the Co sites and find that it cannot be achieved in the ground state of isolated mononuclear fragments [CoII(NC)4(OH2)2]2- for any conformations of the coordinated water molecules and Co-N-C bond angles. On the other hand, it is stabilized by the interaction of the complex with neighboring W ions, which are simulated here by effective potentials. The calculated exchange coupling constants for the CoII-NC-WV binuclear fragments are in reasonable agreement with the measured Curie-Weiss constant for this compound. As additional evidence for the inferred electronic configuration on the Co sites, the ligand-field transitions, the temperature-dependent magnetic susceptibility, and the field-dependent low-temperature magnetization, simulated ab initio for the mononuclear Co fragments, are in agreement with the available data for another compound [WIV[(micro-CN)4-CoII(H2O)2]2.4H2O]n containing diamagnetic W and high-spin Co ions in an isostructural environment.

Monte Carlo simulations of the secondary neutron ambient and effective dose equivalent rates from surface to suborbital altitudes and low Earth orbit

NASA Astrophysics Data System (ADS)

El-Jaby, Samy; Richardson, Richard B.

2015-07-01

Occupational exposures from ionizing radiation are currently regulated for airline travel (<20 km) and for missions to low-Earth orbit (∼300-400 km). Aircrew typically receive between 1 and 6 mSv of occupational dose annually, while aboard the International Space Station, the area radiation dose equivalent measured over just 168 days was 106 mSv at solar minimum conditions. It is anticipated that space tourism vehicles will reach suborbital altitudes of approximately 100 km and, therefore, the annual occupational dose to flight crew during repeated transits is expected to fall somewhere between those observed for aircrew and astronauts. Unfortunately, measurements of the radiation environment at the high altitudes reached by suborbital vehicles are sparse, and modelling efforts have been similarly limited. In this paper, preliminary MCNPX radiation transport code simulations are developed of the secondary neutron flux profile in air from surface altitudes up to low Earth orbit at solar minimum conditions and excluding the effects of spacecraft shielding. These secondary neutrons are produced by galactic cosmic radiation interacting with Earth's atmosphere and are among the sources of radiation that can pose a health risk. Associated estimates of the operational neutron ambient dose equivalent, used for radiation protection purposes, and the neutron effective dose equivalent that is typically used for estimates of stochastic health risks, are provided in air. Simulations show that the neutron radiation dose rates received at suborbital altitudes are comparable to those experienced by aircrew flying at 7 to 14 km. We also show that the total neutron dose rate tails off beyond the Pfotzer maximum on ascension from surface up to low Earth orbit.

Monte Carlo simulations of the secondary neutron ambient and effective dose equivalent rates from surface to suborbital altitudes and low Earth orbit.

PubMed

El-Jaby, Samy; Richardson, Richard B

2015-07-01

Occupational exposures from ionizing radiation are currently regulated for airline travel (<20 km) and for missions to low-Earth orbit (∼300-400 km). Aircrew typically receive between 1 and 6 mSv of occupational dose annually, while aboard the International Space Station, the area radiation dose equivalent measured over just 168 days was 106 mSv at solar minimum conditions. It is anticipated that space tourism vehicles will reach suborbital altitudes of approximately 100 km and, therefore, the annual occupational dose to flight crew during repeated transits is expected to fall somewhere between those observed for aircrew and astronauts. Unfortunately, measurements of the radiation environment at the high altitudes reached by suborbital vehicles are sparse, and modelling efforts have been similarly limited. In this paper, preliminary MCNPX radiation transport code simulations are developed of the secondary neutron flux profile in air from surface altitudes up to low Earth orbit at solar minimum conditions and excluding the effects of spacecraft shielding. These secondary neutrons are produced by galactic cosmic radiation interacting with Earth's atmosphere and are among the sources of radiation that can pose a health risk. Associated estimates of the operational neutron ambient dose equivalent, used for radiation protection purposes, and the neutron effective dose equivalent that is typically used for estimates of stochastic health risks, are provided in air. Simulations show that the neutron radiation dose rates received at suborbital altitudes are comparable to those experienced by aircrew flying at 7 to 14 km. We also show that the total neutron dose rate tails off beyond the Pfotzer maximum on ascension from surface up to low Earth orbit. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

Report on orbital debris

NASA Technical Reports Server (NTRS)

1989-01-01

The success of space endeavors depends upon a space environment sufficiently free of debris to enable the safe and dependable operation of spacecraft. An environment overly cluttered with debris would threaten the ability to utilize space for a wide variety of scientific, technological, military, and commercial purposes. Man made space debris (orbital debris) differs from natural meteoroids because it remains in earth orbit during its lifetime and is not transient through the space around the Earth. The orbital debris environment is considered. The space environment is described along with sources of orbital debris. The current national space policy is examined, along with ways to minimize debris generation and ways to survive the debris environment. International efforts, legal issues and commercial regulations are also examined.

SUPL support for mobile devices

NASA Astrophysics Data System (ADS)

Narisetty, Jayanthi; Soghoyan, Arpine; Sundaramurthy, Mohanapriya; Akopian, David

2012-02-01

Conventional Global Positioning System (GPS) receivers operate well in open-sky environments. But their performance degrades in urban canyons, indoors and underground due to multipath, foliage, dissipation, etc. To overcome such situations, several enhancements have been suggested such as Assisted GPS (A-GPS). Using this approach, orbital parameters including ephemeris and almanac along with reference time and coarse location information are provided to GPS receivers to assist in acquisition of weak signals. To test A-GPS enabled receivers high-end simulators are used, which are not affordable by many academic institutions. This paper presents an economical A-GPS supplement for inexpensive simulators which operates on application layer. Particularly proposed solution is integrated with National Instruments' (NI) GPS Simulation Toolkit and implemented using NI's Labview environment. This A-GPS support works for J2ME and Android platforms. The communication between the simulator and the receiver is in accordance with the Secure User Plane Location (SUPL) protocol encapsulated with Radio Resource Location Protocol (RRLP) applies to Global System for Mobile Communications (GSM) and Universal Mobile Telecommunications System (UMTS) cellular networks.

Development in the SONNE Instrument, a Solar Neutron Spectrometer for Solar Orbiter and Solar Sentinels

NASA Astrophysics Data System (ADS)

Ryan, J. M.; Bravar, U.; Macri, J. R.; McConnell, M. L.; Woolf, R.; Moser, M.; Flueckiger, E.; Pirard, B.; MacKinnon, A.; Mallik, P.; Bruillard, P.

2007-12-01

We report on the technical development of SONNE (Solar Neutron Experiment), a solar neutron spectrometer intended for use on the ESA Solar Orbiter and/or the NASA Solar Sentinels Missions. Development has taken place on three fronts, (1) simulations of a flight instrument, including the spacecraft radiation environment, (2) calibrating a prototype instrument in a monoenergetic neutron beam and (3) mechanical and electrical design of a deep space mission instrument. SONNE will be sensitive to fast neutrons up to 20 MeV, using double scatter imaging techniques to dramatically reduce background. Preliminary beam measurement analysis, conducted just before this abstract, supports advertised design goals in terms of sensitivity and energy resolution, meaning that time stamping neutron emission from the Sun will be possible. Combined with gamma ray measurements, new insight into particle acceleration will emerge when deployed on an inner heliospheric mission. Progress will be reported on simulations and physical design as well as calibrations.

Optical Modeling Activities for NASA's James Webb Space Telescope (JWST): V. Operational Alignment Updates

NASA Technical Reports Server (NTRS)

Howard, Joseph M.; Ha, Kong Q.; Shiri, Ron; Smith, J. Scott; Mosier, Gary; Muheim, Danniella

2008-01-01

This paper is part five of a series on the ongoing optical modeling activities for the James Webb Space Telescope (JWST). The first two papers discussed modeling JWST on-orbit performance using wavefront sensitivities to predict line of sight motion induced blur, and stability during thermal transients. The third paper investigates the aberrations resulting from alignment and figure compensation of the controllable degrees of freedom (primary and secondary mirrors), which may be encountered during ground alignment and on-orbit commissioning of the observatory, and the fourth introduced the software toolkits used to perform much of the optical analysis for JWST. The work here models observatory operations by simulating line-of-sight image motion and alignment drifts over a two-week period. Alignment updates are then simulated using wavefront sensing and control processes to calculate and perform the corrections. A single model environment in Matlab is used for evaluating the predicted performance of the observatory during these operations.

Results of a space shuttle pulme impingement investigation at stage separation in the NASA-MSFC impulse base flow facility

NASA Technical Reports Server (NTRS)

Mccanna, R. W.; Sims, W. H.

1972-01-01

Results are presented for an experimental space shuttle stage separation plume impingement program conducted in the NASA-Marshall Space Flight Center's impulse base flow facility (IBFF). Major objectives of the investigation were to: (1)determine the degree of dual engine exhaust plume simulation obtained using the equivalent engine; (2) determine the applicability of the analytical techniques; and (3) obtain data applicable for use in full-scale studies. The IBFF tests determined the orbiter rocket motor plume impingement loads, both pressure and heating, on a 3 percent General Dynamics B-15B booster configuration in a quiescent environment simulating a nominal staging altitude of 73.2 km (240,00 ft). The data included plume surveys of two 3 percent scale orbiter nozzles, and a 4.242 percent scaled equivalent nozzle - equivalent in the sense that it was designed to have the same nozzle-throat-to-area ratio as the two 3 percent nozzles and, within the tolerances assigned for machining the hardware, this was accomplished.

ATTDES: An Expert System for Satellite Attitude Determination and Control. 2

NASA Technical Reports Server (NTRS)

Mackison, Donald L.; Gifford, Kevin

1996-01-01

The design, analysis, and flight operations of satellite attitude determintion and attitude control systems require extensive mathematical formulations, optimization studies, and computer simulation. This is best done by an analyst with extensive education and experience. The development of programs such as ATTDES permit the use of advanced techniques by those with less experience. Typical tasks include the mission analysis to select stabilization and damping schemes, attitude determination sensors and algorithms, and control system designs to meet program requirements. ATTDES is a system that includes all of these activities, including high fidelity orbit environment models that can be used for preliminary analysis, parameter selection, stabilization schemes, the development of estimators covariance analyses, and optimization, and can support ongoing orbit activities. The modification of existing simulations to model new configurations for these purposes can be an expensive, time consuming activity that becomes a pacing item in the development and operation of such new systems. The use of an integrated tool such as ATTDES significantly reduces the effort and time required for these tasks.

Ejecta cloud from the AIDA space project kinetic impact on the secondary of a binary asteroid: I. mechanical environment and dynamical model

NASA Astrophysics Data System (ADS)

Yu, Yang; Michel, Patrick; Schwartz, Stephen R.; Naidu, Shantanu P.; Benner, Lance A. M.

2017-01-01

An understanding of the post-impact dynamics of ejecta clouds are crucial to the planning of a kinetic impact mission to an asteroid, and also has great implications for the history of planetary formation. The purpose of this article is to track the evolution of ejecta produced by AIDA mission, which targets for kinetic impact the secondary of near-Earth binary asteroid (65803) Didymos on 2022, and to feedback essential informations to AIDA's ongoing phase-A study. We present a detailed dynamic model for the simulation of an ejecta cloud from a binary asteroid that synthesizes all relevant forces based on a previous analysis of the mechanical environment. We apply our method to gain insight into the expected response of Didymos to the AIDA impact, including the subsequent evolution of debris and dust. The crater scaling relations from laboratory experiments are employed to approximate the distributions of ejecta mass and launching speed. The size distribution of fragments is modeled with a power law fitted from observations of real asteroid surface. A full-scale demonstration is simulated using parameters specified by the mission. We report the results of the simulation, which include the computed spread of the ejecta cloud and the recorded history of ejecta accretion and escape. The violent period of the ejecta evolution is found to be short, and is followed by a stage where the remaining ejecta is gradually cleared. Solar radiation pressure proves to be efficient in cleaning dust-size ejecta, and the simulation results after two weeks shows that large debris on polar orbits (perpendicular to the binary orbital plane) has a survival advantage over smaller ejecta and ejecta that keeps to low latitudes.

Progress in Spacecraft Environment Interactions: International Space Station (ISS) Development and Operations

NASA Technical Reports Server (NTRS)

Koontz, Steve; Suggs, Robb; Schneider, Todd; Minow, Joe; Alred, John; Cooke, Bill; Mikatarian, Ron; Kramer, Leonard; Boeder, paul; Soares, Carlos

2007-01-01

The set of spacecraft interactions with the space flight environment that have produced the largest impacts on the design, verification, and operation of the International Space Station (ISS) Program during the May 2000 to May 2007 time frame are the focus of this paper. In-flight data, flight crew observations, and the results of ground-based test and analysis directly supporting programmatic and operational decision-making are reported as are the analysis and simulation efforts that have led to new knowledge and capabilities supporting current and future space explorations programs. The specific spacecraft-environment interactions that have had the greatest impact on ISS Program activities during the first several years of flight are: 1) spacecraft charging, 2) micrometeoroids and orbital debris effects, 3) ionizing radiation (both total dose to materials and single event effects [SEE] on avionics), 4) hypergolic rocket engine plume impingement effects, 5) venting/dumping of liquids, 6) spacecraft contamination effects, 7) neutral atmosphere and atomic oxygen effects, 8) satellite drag effects, and 9) solar ultraviolet effects. Orbital inclination (51.6deg) and altitude (nominally between 350 km and 460 km) determine the set of natural environment factors affecting the performance and reliability of materials and systems on ISS. ISS operates in the F2 region of Earth s ionosphere in well-defined fluxes of atomic oxygen, other ionospheric plasma species, solar UV, VUV, and x-ray radiation as well as galactic cosmic rays, trapped radiation, and solar cosmic rays. The micrometeoroid and orbital debris environment is an important determinant of spacecraft design and operations in any orbital inclination. The induced environment results from ISS interactions with the natural environment as well as environmental factors produced by ISS itself and visiting vehicles. Examples include ram-wake effects, hypergolic thruster plume impingement, materials out-gassing, venting and dumping of fluids, and specific photovoltaic (PV) power system interactions with the ionospheric plasma. Vehicle size (L) and velocity (v), combined with the magnitude and direction of the geomagnetic field (B) produce operationally significant magnetic induction voltages (VxB.L) in ISS conducting structure during high latitude flight (>+/- 45deg) during each orbit. In addition, ISS is a large vehicle and produces a deep wake structure from which both ionospheric plasma and neutrals species are largely excluded. ISS must fly in a very limited number of approved flight attitudes, so that exposure of a particular material or system to environmental factors depends upon: 1) location on ISS, 2) ISS flight configuration, 3) ISS flight attitude, and 4) variation of solar exposure (Beta angle), and hence thermal environment, with time. Finally, an induced ionizing radiation environment is produced by trapped radiation and solar/cosmic ray interactions with the relatively massive ISS structural shielding.

Compendium of Information for Interpreting the Microgravity Environment of the Orbiter Spacecraft

NASA Technical Reports Server (NTRS)

DeLombard, Richard

1996-01-01

Science experiments are routinely conducted on the NASA shuttle orbiter vehicles. Primarily, these experiments are operated on such missions to take advantage of the microgravity (low-level acceleration) environment conditions during on-orbit operations. Supporting accelerometer instruments are operated with the experiments to measure the microgravity acceleration environment in which the science experiments were operated. Tne Principal Investigator Microgravity Services (PIMS) Project at NASA Lewis Research Center interprets these microgravity acceleration data and prepares mission summary reports to aid the principal investigators of the scientific experiments in understanding the microgravity environment. Much of the information about the orbiter vehicle and the microgravity environment remains the same for each mission. Rather than repeat that information in each mission summary report, reference information is presented in this report to assist users in understanding the microgravity-acceleration data. The characteristics of the microgravity acceleration environment are first presented. The methods of measurement and common instruments used on orbiter missions are described. The coordinate systems utilized in the orbiter and accelerometers are described. Some of the orbiter attitudes utilized in microgravity related missions are illustrated. Methods of data processing are described and illustrated. The interpretation of the microgravity acceleration data is included with an explanation of common disturbance sources. Instructions to access some of the acceleration data and a description of the orbiter thrusters are explained in the appendixes. A microgravity environment bibliography is also included.

Creating the Deep Space Environment for Testing the James Webb Space Telescope (JWST) at NASA Johnson Space Center's Chamber A

NASA Technical Reports Server (NTRS)

Homan, Jonathan L.; Cerimele, Mary P.; Montz, Michael E.; Bachtel, Russell; Speed, John; O'Rear, Patrick

2013-01-01

Chamber A is the largest thermal vacuum chamber at the Johnson Space Center and is one of the largest space environment chambers in the world. The chamber is 19.8 m (65 ft) in diameter and 36.6 m (120 ft) tall and is equipped with cryogenic liquid nitrogen panels (shrouds) and gaseous helium shrouds to create a simulated space environment. It was originally designed and built in the mid 1960 s to test the Apollo Command and Service Module and several manned tests were conducted on that spacecraft, contributing to the success of the program. The chamber has been used since that time to test spacecraft active thermal control systems, Shuttle DTO, DOD, and ESA hardware in simulated Low Earth Orbit (LEO) conditions. NASA is now moving from LEO towards exploration of locations with environments approaching those of deep space. Therefore, Chamber A has undergone major modifications to enable it to simulate these deeper space environments. Environmental requirements were driven, and modifications were funded by the James Webb Space Telescope program, and this telescope which will orbit Solar/Earth L2, will be the first test article to benefit from the chamber s new capabilities. To accommodate JWST, the Chamber A high vacuum system has been modernized, additional LN2 shrouds have been installed, the liquid nitrogen system has been modified to remove dependency on electrical power and increase its reliability, a new helium shroud/refrigeration system has been installed to create a colder more stable and uniform heat sink, and the controls have been updated to increase the level of automation and improve operator interfaces. Testing of these major modifications was conducted in August of 2012 and this initial test was very successful, with all major systems exceeding their performance requirements. This paper will outline the changes in overall environmental requirements, discuss the technical design data that was used in the decisions leading to the extensive modifications, and describe the new capabilities of the chamber.

Creating the Deep Space Environment for Testing the James Webb Space Telescope at NASA Johnson Space Center's Chamber A

NASA Technical Reports Server (NTRS)

Homan, Jonathan L.; Cerimele, Mary P.; Montz, Michael E.; Bachtel, Russell; Speed, John; O'Rear, Patrick

2013-01-01

Chamber A is the largest thermal vacuum chamber at the Johnson Space Center and is one of the largest space environment chambers in the world. The chamber is 19.8 m (65 ft.) in diameter and 36.6 m (120 ft.) tall and is equipped with cryogenic liquid nitrogen panels (shrouds) and gaseous helium shrouds to create a simulated space environment. It was originally designed and built in the mid 1960 s to test the Apollo Command and Service Module and several manned tests were conducted on that spacecraft, contributing to the success of the program. The chamber has been used since that time to test spacecraft active thermal control systems, Shuttle DTO, DOD, and ESA hardware in simulated Low Earth Orbit (LEO) conditions. NASA is now moving from LEO towards exploration of locations with environments approaching those of deep space. Therefore, Chamber A has undergone major modifications to enable it to simulate these deeper space environments. Environmental requirements were driven, and modifications were funded by the James Webb Space Telescope program, and this telescope, which will orbit Solar/Earth L2, will be the first test article to benefit from the chamber s new capabilities. To accommodate JWST, the Chamber A high vacuum system has been modernized, additional LN2 shrouds have been installed, the liquid nitrogen system has been modified to minimize dependency on electrical power and increase its reliability, a new helium shroud/refrigeration system has been installed to create a colder more stable and uniform heat sink, and the controls have been updated to increase the level of automation and improve operator interfaces. Testing of these major modifications was conducted in August of 2012 and this initial test was very successful, with all major systems exceeding their performance requirements. This paper will outline the changes in overall environmental requirements, discuss the technical design data that was used in the decisions leading to the extensive modifications, and describe the new capabilities of the chamber.

Creating the Deep Space Environment for Testing the James Webb Space Telescope at the Johnson Space Center's Chamber A

NASA Technical Reports Server (NTRS)

Homan, Jonathan L.; Cerimele, Mary P.; Montz, Michael E.

2012-01-01

Chamber A is the largest thermal vacuum chamber at the Johnson Space Center and is one of the largest space environment chambers in the world. The chamber is 19.8 m (65 ft) in diameter and 36.6 m (120 ft) tall and is equipped with cryogenic liquid nitrogen panels (shrouds) and gaseous helium shrouds to create a simulated space environment. It was originally designed and built in the mid 1960's to test the Apollo Command and Service Module and several manned tests were conducted on that spacecraft, contributing to the success of the program. The chamber has been used since that time to test spacecraft active thermal control systems, Shuttle DTO, DOD, and ESA hardware in simulated Low Earth Orbit (LEO) conditions. NASA is now moving from LEO towards exploration of locations with environments approaching those of deep space. Therefore, Chamber A has undergone major modifications to enable it to simulate these deeper space environments. Environmental requirements were driven, and the modifications were funded, by the James Webb Space Telescope program, and this telescope which will orbit Solar/Earth L2, will be the first test article to benefit from the chamber s new capabilities. To accommodate JWST, the Chamber A high vacuum system has been modernized, additional LN2 shrouds have been installed, the liquid nitrogen system has been modified to remove dependency on electrical power and increase its reliability, a new helium shroud/refrigeration system has been installed to create a colder more stable and uniform heat sink and, the controls have been updated to increase the level of automation and improve operator interfaces. Testing of these major modifications was conducted in August 2012 and this initial test was very successful, with all major systems exceeding their performance requirements. This paper will outline the changes in the overall environmental requirements, discuss the technical design data that was used in the decisions leading to the extensive modifications, and describe the new capabilities of the chamber.

The Fast Debris Evolution Model

NASA Astrophysics Data System (ADS)

Lewis, Hugh G.; Swinerd, Graham; Newland, Rebecca; Saunders, Arrun

The ‘Particles-in-a-box' (PIB) model introduced by Talent (1992) removed the need for computerintensive Monte Carlo simulation to predict the gross characteristics of an evolving debris environment. The PIB model was described using a differential equation that allows the stability of the low Earth orbit (LEO) environment to be tested by a straightforward analysis of the equation's coefficients. As part of an ongoing research effort to investigate more efficient approaches to evolutionary modelling and to develop a suite of educational tools, a new PIB model has been developed. The model, entitled Fast Debris Evolution (FaDE), employs a first-order differential equation to describe the rate at which new objects (˜ 10 cm) are added and removed from the environment. Whilst Talent (1992) based the collision theory for the PIB approach on collisions between gas particles and adopted specific values for the parameters of the model from a number of references, the form and coefficients of the FaDE model equations can be inferred from the outputs of future projections produced by high-fidelity models, such as the DAMAGE model. The FaDE model has been implemented as a client-side, web-based service using Javascript embedded within a HTML document. Due to the simple nature of the algorithm, FaDE can deliver the results of future projections immediately in a graphical format, with complete user-control over key simulation parameters. Historical and future projections for the ˜ 10 cm low Earth orbit (LEO) debris environment under a variety of different scenarios are possible, including business as usual, no future launches, post-mission disposal and remediation. A selection of results is presented with comparisons with predictions made using the DAMAGE environment model. The results demonstrate that the FaDE model is able to capture comparable time-series of collisions and number of objects as predicted by DAMAGE in several scenarios. Further, and perhaps more importantly, its speed and flexibility allows the user to explore and understand the evolution of the space debris environment.

Global Precipitation Measurement (GPM) Orbit Design and Autonomous Maneuvers

NASA Technical Reports Server (NTRS)

Folta, David; Mendelsohn, Chad

2003-01-01

The NASA Goddard Space Flight Center's Global Precipitation Measurement (GPM) mission will meet a challenge of measuring worldwide precipitation every three hours. The GPM spacecraft, part of a constellation, will be required to maintain a circular orbit in a high drag environment to accomplish this challenge. Analysis by the Flight Dynamics Analysis Branch has shown that the prime orbit altitude of 40% is necessary to prevent ground track repeating. Combined with goals to minimize maneuver impacts to science data collection and enabling reasonable long-term orbit predictions, the GPM project has decided to fly an autonomous maneuver system. This system is a derivative of the successful New Millennium Program technology flown onboard the Earth Observing-1 mission. This paper presents the driving science requirements and goals of the mission and shows how they will be met. Analysis of the orbit optimization and the AV requirements for several ballistic properties are presented. The architecture of the autonomous maneuvering system to meet the goals and requirements is presented along with simulations using a GPM prototype. Additionally, the use of the GPM autonomous system to mitigate possible collision avoidance and to aid other spacecraft systems during navigation outages is explored.

Generation of a Circumstellar Gas Disk by Hot Jupiter WASP-12b

NASA Astrophysics Data System (ADS)

Debrecht, Alex; Carroll-Nellenback, Jonathan; Frank, Adam; Fossati, Luca; Blackman, Eric G.; Dobbs-Dixon, Ian

2018-05-01

Observations of transiting extra-solar planets provide rich sources of data for probing the in-system environment. In the WASP-12 system, a broad depression in the usually-bright MgII h&k lines has been observed, in addition to atmospheric escape from the extremely hot Jupiter WASP-12b. It has been hypothesized that a translucent circumstellar cloud is formed by the outflow from the planet, causing the observed signatures. We perform 3D hydrodynamic simulations of the full system environment of WASP-12, injecting a planetary wind and stellar wind from their respective surfaces. We find that a torus of density high enough to account for the lack of MgII h&k line core emission in WASP-12 can be formed in approximately 13 years. We also perform synthetic observations of the Lyman-alpha spectrum at different points in the planet's orbit, which demonstrate that significant absorption occurs at all points in the orbit, not just during transits, as suggested by the observations.

An electrically conductive thermal control surface for spacecraft encountering Low-Earth Orbit (LEO) atomic oxygen indium tin oxide-coated thermal blankets

NASA Technical Reports Server (NTRS)

Bauer, J. L.

1987-01-01

An organic black thermal blanket material was coated with indium tin oxide (ITO) to prevent blanket degradation in the low Earth orbit (LEO) atomic oxygen environment. The blankets were designed for the Galileo spacecraft. Galileo was initially intended for space shuttle launch and would, therefore, have been exposed to atomic oxygen in LEO for between 10 and 25 hours. Two processes for depositing ITO are described. Thermooptical, electrical, and chemical properties of the ITO film are presented as a function of the deposition process. Results of exposure of the ITO film to atomic oxygen (from a shuttle flight) and radiation exposure (simulated Jovian environment) are also presented. It is shown that the ITO-protected thermal blankets would resist the anticipated LEO oxygen and Jovian radiation yet provide adequate thermooptical and electrical resistance. Reference is made to the ESA Ulysses spacecraft, which also used ITO protection on thermal control surfaces.

Environmental Durability Issues for Solar Power Systems in Low Earth Orbit

NASA Technical Reports Server (NTRS)

Degroh, Kim K.; Banks, Bruce A.; Smith, Daniela C.

1994-01-01

Space solar power systems for use in the low Earth orbit (LEO) environment experience a variety of harsh environmental conditions. Materials used for solar power generation in LEO need to be durable to environmental threats such as atomic oxygen, ultraviolet (UV) radiation, thermal cycling, and micrometeoroid and debris impact. Another threat to LEO solar power performance is due to contamination from other spacecraft components. This paper gives an overview of these LEO environmental issues as they relate to space solar power system materials. Issues addressed include atomic oxygen erosion of organic materials, atomic oxygen undercutting of protective coatings, UV darkening of ceramics, UV embrittlement of Teflon, effects of thermal cycling on organic composites, and contamination due to silicone and organic materials. Specific examples of samples from the Long Duration Exposure Facility (LDEF) and materials returned from the first servicing mission of the Hubble Space Telescope (HST) are presented. Issues concerning ground laboratory facilities which simulate the LEO environment are discussed along with ground-to-space correlation issues.

State-of-the-Art Technologies for Construction in Space: a Review.

DTIC Science & Technology

1987-09-01

reinforcing fiber or fiber mat. Investigations of bonding, thermal stress, forming tech- niques, specific strengths, specific moduli, and microfracture...diameter and about 15 ft long. The graphite fibers follow the length of the tube and the polymer compound used as the matrix is applied over the graphite...combination of Sthese approaches to obtain the best simulation of the low-Earth orbit environment. Most materials tested to date are polymers such as

'Weightless' acrylic painting by Jack Kroehnke

NASA Technical Reports Server (NTRS)

1987-01-01

'Weightless' acrylic painting by Jack Kroehnke depicts STS-26 Discovery, Orbiter Vehicle (OV) 103, Mission Specialist (MS) David C. Hilmers participating in extravehicular activity (EVA) simulation in JSC Weightless Environment Training Facility (WETF) Bldg 29. In the payload bay (PLB) mockup, Hilmers, wearing extravehicular mobility unit (EMU), holds onto the mission-peculiar equipment support structure in foreground while SCUBA-equipped diver monitors activity overhead and camera operator records EVA procedures. Copyrighted art work for use by NASA.

STS-50 Payload Specialist Trinh during JSC WETF Bailout Exercises in Bldg 29

NASA Technical Reports Server (NTRS)

1992-01-01

STS-50 Columbia, Orbiter Vehicle (OV) 102, United States Microgravity Laboratory 1 (USML-1) Payload Specialist Eugene H. Trinh, wearing launch and entry suit (LES), listens to instructions prior to participating in launch emergency egress (bailout) exercises in JSC's Weightless Environment Training Facility (WETF) Bldg 29. The WETF's 25-foot deep pool will simulate the ocean as crewmembers familiarize themselves with procedures associated with a bailout and subsequent water landing.

STS-52 Pilot Baker, in LES, dons parachute during JSC WETF bailout exercises

NASA Technical Reports Server (NTRS)

1992-01-01

STS-52 Columbia, Orbiter Vehicle (OV) 102, Pilot Michael A. Baker is assisted with a training version of his Shuttle partial-pressure launch and entry suit (LES). A technician adjusts his parachute harness prior to the emergency egress (bailout) training exercise in JSC's Weightless Environment Training Facility (WETF) Bldg 29 pool. The WETF's 25-ft deep pool will be used in this simulation of a water landing.

STS-52 Mission Specialist Veach, in LES/LEH, during JSC WETF bailout exercise

NASA Technical Reports Server (NTRS)

1992-01-01

STS-52 Columbia, Orbiter Vehicle (OV) 102, Mission Specialist (MS) Charles Lacy Veach, wearing launch and entry suit (LES) and launch and entry helmet (LEH), smiles as he observes emergency egress (bailout) training exercise in JSC's Weightless Environment Training Facility (WETF) Bldg 29 pool. Veach waits his turn to be dropped into the WETF's 25-ft deep pool which will simulate the ocean during of his water landing.

STS-26 Pilot Covey floats in life raft during JSC WETF exercises

NASA Technical Reports Server (NTRS)

1988-01-01

STS-26 Discovery, Orbiter Vehicle (OV) 103, Pilot Richard O. Covey, wearing the newly designed launch and entry suit (LES), floats in single-occupant life raft in JSC Weightless Environment Training Facility (WETF) Bldg 29 pool. Covey pulls and fastens life raft protective cover over himself. The simulation of the escape and rescue operations utilized the crew escape system (CES) pole method of egress from the Space Shuttle.

STS-52 Mission Specialist Veach in life raft during JSC bailout exercises

NASA Technical Reports Server (NTRS)

1992-01-01

STS-52 Columbia, Orbiter Vehicle (OV) 102, Mission Specialist (MS) Charles Lacy Veach, wearing launch and entry suit (LES) and launch and entry helmet (LEH), floats in a single person life raft during emergency egress (bailout) training exercises in JSC's Weightless Environment Training Facility (WETF) Bldg 29 pool. SCUBA-equipped divers look on. The bailout exercises utilize the WETF's 25-foot deep pool as the ocean for this water landing simulation.

Pose Measurement Performance of the Argon Relative Navigation Sensor Suite in Simulated Flight Conditions

NASA Technical Reports Server (NTRS)

Galante, Joseph M.; Eepoel, John Van; Strube, Matt; Gill, Nat; Gonzalez, Marcelo; Hyslop, Andrew; Patrick, Bryan

2012-01-01

Argon is a flight-ready sensor suite with two visual cameras, a flash LIDAR, an on- board flight computer, and associated electronics. Argon was designed to provide sensing capabilities for relative navigation during proximity, rendezvous, and docking operations between spacecraft. A rigorous ground test campaign assessed the performance capability of the Argon navigation suite to measure the relative pose of high-fidelity satellite mock-ups during a variety of simulated rendezvous and proximity maneuvers facilitated by robot manipulators in a variety of lighting conditions representative of the orbital environment. A brief description of the Argon suite and test setup are given as well as an analysis of the performance of the system in simulated proximity and rendezvous operations.

Natural orbital environment definition guidelines for use in aerospace vehicle development

NASA Technical Reports Server (NTRS)

Anderson, B. Jeffrey (Editor); Smith, Robert E. (Compiler)

1994-01-01

This document provides definitions of the natural near-Earth space environment suitable for use in the initial development/design phase of any space vehicle. The natural environment includes the neutral atmosphere, plasma, charged particle radiation, electromagnetic radiation (EMR), meteoroids, orbital debris, magnetic field, physical and thermal constants, and gravitational field. Communications and other unmanned satellites operate in geosynchronous-Earth orbit (GEO); therefore, some data are given for GEO, but emphasis is on altitudes from 200 km to 1000 km (low-Earth orbit (LEO)). This document does not cover the induced environment of other effects resulting from presence of the space vehicle. Manmade factors are included as part of the ambient natural environment; i.e., orbital debris and radio frequency (RF) noise generated on Earth, because they are not caused by the presence of the space vehicle but form part of the ambient environment that the space vehicle experiences.

The Particle Accelerator Simulation Code PyORBIT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gorlov, Timofey V; Holmes, Jeffrey A; Cousineau, Sarah M

2015-01-01

The particle accelerator simulation code PyORBIT is presented. The structure, implementation, history, parallel and simulation capabilities, and future development of the code are discussed. The PyORBIT code is a new implementation and extension of algorithms of the original ORBIT code that was developed for the Spallation Neutron Source accelerator at the Oak Ridge National Laboratory. The PyORBIT code has a two level structure. The upper level uses the Python programming language to control the flow of intensive calculations performed by the lower level code implemented in the C++ language. The parallel capabilities are based on MPI communications. The PyORBIT ismore » an open source code accessible to the public through the Google Open Source Projects Hosting service.« less

Temporal Evolution of the Plasma Sheath Surrounding Solar Cells in Low Earth Orbit

NASA Technical Reports Server (NTRS)

Willis, Emily M.; Pour, Maria Z. A.

2017-01-01

High voltage solar array interactions with the space environment can have a significant impact on array performance and spacecraft charging. Over the past 10 years, data from the International Space Station has allowed for detailed observations of these interactions over long periods of time. Some of the surprising observations have been floating potential transients, which were not expected and are not reproduced by existing models. In order to understand the underlying processes producing these transients, the temporal evolution of the plasma sheath surrounding the solar cells in low Earth orbit is being investigated. This study includes lumped element modeling and particle-in-cell simulation methods. This presentation will focus on recent results from the on-going investigations.

An analysis of the booster plume impingement environment during the space shuttle nominal staging maneuver

NASA Technical Reports Server (NTRS)

Wojciechowski, C. J.; Penny, M. M.; Greenwood, T. F.; Fossler, I. H.

1972-01-01

An experimental study of the plume impingement heating on the space shuttle booster afterbody resulting from the space shuttle orbiter engine plumes was conducted. The 1/100-scale model tests consisted of one and two orbiter engine firings on a flat plate, a flat plate with a fin, and a cylinder model. The plume impingement heating rates on these surfaces were measured using thin film heat transfer gages. Results indicate the engine simulation is a reasonable approximation to the two engine configuration, but more tests are needed to verify the plume model of the main engine configuration. For impingment, results show models experienced laminar boundary layer convective heating. Therefore, tests at higher Reynolds numbers are needed to determine impingment heating.

Simulation platform of LEO satellite communication system based on OPNET

NASA Astrophysics Data System (ADS)

Zhang, Yu; Zhang, Yong; Li, Xiaozhuo; Wang, Chuqiao; Li, Haihao

2018-02-01

For the purpose of verifying communication protocol in the low earth orbit (LEO) satellite communication system, an Optimized Network Engineering Tool (OPNET) based simulation platform is built. Using the three-layer modeling mechanism, the network model, the node model and the process model of the satellite communication system are built respectively from top to bottom, and the protocol will be implemented by finite state machine and Proto-C language. According to satellite orbit parameters, orbit files are generated via Satellite Tool Kit (STK) and imported into OPNET, and the satellite nodes move along their orbits. The simulation platform adopts time-slot-driven mode, divides simulation time into continuous time slots, and allocates slot number for each time slot. A resource allocation strategy is simulated on this platform, and the simulation results such as resource utilization rate, system throughput and packet delay are analyzed, which indicate that this simulation platform has outstanding versatility.

DSMC Simulations in Support of the Columbia Shuttle Orbiter Accident Investigation

NASA Technical Reports Server (NTRS)

Boyles, Katie; LeBeau, Gerald J.; Gallis, Michael A.

2004-01-01

Three-dimensional Direct Simulation Monte Carlo simulations of Columbia Shuttle Orbiter flight STS-107 are presented. The aim of this work is to determine the aerodynamic and heating behavior of the Orbiter during aerobraking maneuvers and to provide piecewise integration of key scenario events to assess the plausibility of the candidate failure scenarios. The flight of the Orbiter is examined at two altitudes: 350-kft and 300-kft. The flowfield around the Orbiter and the heat transfer to it are calculated for the undamaged configuration. The flow inside the wing for an assumed damage to the leading edge in the form of a 10- inch hole is studied.

Test and training simulator for ground-based teleoperated in-orbit servicing

NASA Technical Reports Server (NTRS)

Schaefer, Bernd E.

1989-01-01

For the Post-IOC(In-Orbit Construction)-Phase of COLUMBUS it is intended to use robotic devices for the routine operations of ground-based teleoperated In-Orbit Servicing. A hardware simulator for verification of the relevant in-orbit operations technologies, the Servicing Test Facility, is necessary which mainly will support the Flight Control Center for the Manned Space-Laboratories for operational specific tasks like system simulation, training of teleoperators, parallel operation simultaneously to actual in-orbit activities and for the verification of the ground operations segment for telerobotics. The present status of definition for the facility functional and operational concept is described.

Development of the CSI phase-3 evolutionary model testbed

NASA Technical Reports Server (NTRS)

Gronet, M. J.; Davis, D. A.; Tan, M. K.

1994-01-01

This report documents the development effort for the reconfiguration of the Controls-Structures Integration (CSI) Evolutionary Model (CEM) Phase-2 testbed into the CEM Phase-3 configuration. This step responds to the need to develop and test CSI technologies associated with typical planned earth science and remote sensing platforms. The primary objective of the CEM Phase-3 ground testbed is to simulate the overall on-orbit dynamic behavior of the EOS AM-1 spacecraft. Key elements of the objective include approximating the low-frequency appendage dynamic interaction of EOS AM-1, allowing for the changeout of components, and simulating the free-free on-orbit environment using an advanced suspension system. The fundamentals of appendage dynamic interaction are reviewed. A new version of the multiple scaling method is used to design the testbed to have the full-scale geometry and dynamics of the EOS AM-1 spacecraft, but at one-tenth the weight. The testbed design is discussed, along with the testing of the solar array, high gain antenna, and strut components. Analytical performance comparisons show that the CEM Phase-3 testbed simulates the EOS AM-1 spacecraft with good fidelity for the important parameters of interest.

Low Earth Orbital Atomic Oxygen Interactions With Materials

NASA Technical Reports Server (NTRS)

Banks, Bruce A.; Miller, Sharon K.; deGroh, Kim K.

2004-01-01

Atomic oxygen is formed in the low Earth orbital environment (LEO) by photo dissociation of diatomic oxygen by short wavelength (< 243 nm) solar radiation which has sufficient energy to break the 5.12 eV O2 diatomic bond in an environment where the mean free path is sufficiently long ( 108 meters) that the probability of reassociation or the formation of ozone (O3) is small. As a consequence, between the altitudes of 180 and 650 km, atomic oxygen is the most abundant species. Spacecraft impact the atomic oxygen resident in LEO with sufficient energy to break hydrocarbon polymer bonds, causing oxidation and thinning of the polymers due to loss of volatile oxidation products. Mitigation techniques, such as the development of materials with improved durability to atomic oxygen attack, as well as atomic oxygen protective coatings, have been employed with varying degrees of success to improve durability of polymers in the LEO environment. Atomic oxygen can also oxidize silicones and silicone contamination to produce non-volatile silica deposits. Such contaminants are present on most LEO missions and can be a threat to performance of optical surfaces. The LEO atomic oxygen environment, its interactions with materials, results of space testing, computational modeling, mitigation techniques, and ground laboratory simulation procedures and issues are presented.

SPICE Module for the Satellite Orbit Analysis Program (SOAP)

NASA Technical Reports Server (NTRS)

Coggi, John; Carnright, Robert; Hildebrand, Claude

2008-01-01

A SPICE module for the Satellite Orbit Analysis Program (SOAP) precisely represents complex motion and maneuvers in an interactive, 3D animated environment with support for user-defined quantitative outputs. (SPICE stands for Spacecraft, Planet, Instrument, Camera-matrix, and Events). This module enables the SOAP software to exploit NASA mission ephemeris represented in the JPL Ancillary Information Facility (NAIF) SPICE formats. Ephemeris types supported include position, velocity, and orientation for spacecraft and planetary bodies including the Sun, planets, natural satellites, comets, and asteroids. Entire missions can now be imported into SOAP for 3D visualization, playback, and analysis. The SOAP analysis and display features can now leverage detailed mission files to offer the analyst both a numerically correct and aesthetically pleasing combination of results that can be varied to study many hypothetical scenarios. The software provides a modeling and simulation environment that can encompass a broad variety of problems using orbital prediction. For example, ground coverage analysis, communications analysis, power and thermal analysis, and 3D visualization that provide the user with insight into complex geometric relations are included. The SOAP SPICE module allows distributed science and engineering teams to share common mission models of known pedigree, which greatly reduces duplication of effort and the potential for error. The use of the software spans all phases of the space system lifecycle, from the study of future concepts to operations and anomaly analysis. It allows SOAP software to correctly position and orient all of the principal bodies of the Solar System within a single simulation session along with multiple spacecraft trajectories and the orientation of mission payloads. In addition to the 3D visualization, the user can define numeric variables and x-y plots to quantitatively assess metrics of interest.

Characterization of the Catalog Fengyun-1C Fragments and Their Long-term Effect on the LEO Environment

NASA Technical Reports Server (NTRS)

Liou, J.-C.; Johnson, N. L.

2008-01-01

The intentional breakup of Fengyun-1C on 11 January 2007 created the most severe orbital debris cloud in history. More than 2500 large fragments were identified and tracked by the U.S. Space Surveillance Network by the end of the year. The altitude where the event occurred was probably the worst location for a major breakup in the low Earth orbit (LEO) region, since it was already highly populated with operational satellites and debris generated from previous breakups. The addition of so many fragments not only poses a realistic threat to operational satellites in the region, but also increases the instability (i.e., collision cascade effect) of the debris population there. Preliminary analysis of the large Fengyun-1C fragments indicates that their size and area-to-mass ratio (A/M) distributions are very different from those of other known events. About half of the fragments appear to be composed of light-weight materials and more than 100 of them have A/M values exceeding 1 square meter per kilogram, consistent with thermal blanket pieces. In addition, the orbital elements of the fragments suggest nontrivial velocity gain by the fragment cloud during the impact. These important characteristics were incorporated into a numerical simulation to assess the long-term impact of the Fengyun-1C fragments to the LEO debris environment. The main objectives of the simulation were to evaluate (1) the collision probabilities between the Fengyun-1C fragments and the rest of the catalog population and (2) the collision activities and population growth in the region in the next 100 years.

A Methodology for Training International Space Station Crews to Respond to On-Orbit Emergencies

NASA Technical Reports Server (NTRS)

Balmain, Clinton; Fleming, Mark

2009-01-01

Most spaceflight crewmembers agree that emergency training is among the most important training they receive. If an emergency event occurs on-orbit crewmembers want to be able to rely on a thorough and proficient knowledge of emergency operations and procedures. The inherent complexity of ISS and the international nature of the onboard operations have resulted in emergency procedures that are complex by any measure; as a result, a very robust apparatus has been developed to give crewmembers initial training on emergency procedures and ensure proficiency up to (and even after) launch. One of the most important aspects of complex onboard operations in general, and emergency operations specifically, is learning how to coordinate roles and responsibilities with fellow crewmembers. A primary goal of NASA s emergency training program is to allow the crewmembers who will actually be together on-orbit to practice executing the emergency responses together before they fly. As with any operation that includes the use of software and hardware, the fidelity of the simulation environment is a critical element to successful training. The NASA training division has spent considerable time and effort to develop a simulator that addresses the most important aspects of emergency response, working within very difficult space and budgetary constraints.

Evaluation and Selection of Replacement Thermal Control Materials for the Hubble Space Telescope

NASA Technical Reports Server (NTRS)

Townsend, Jacqueline A.; Hansen, Patricia A.; McClendon, Mark W.; Dever, Joyce A.; Triolo, Jack J.

1998-01-01

The mechanical and optical properties of the metallized Teflon(Registered Trademark) FEP thermal control materials on the Hubble Space Telescope (HST) have degraded over the nearly seven years the telescope has been in orbit. Given the damage to the outer layer of the multi-layer insulation (MLI) that was apparent during the second servicing mission (SM2), the decision was made to replace the outer layer during subsequent servicing missions. A Failure Review Board was established to investigate the damage to the MLI and identify a replacement material. The replacement material had to meet the stringent thermal requirements of the spacecraft and maintain structural integrity for at least ten years. Ten candidate materials were selected and exposed to ten-year HST-equivalent doses of simulated orbital environments. Samples of the candidates were exposed sequentially to low and high energy electrons and protons, atomic oxygen, x-ray radiation, ultraviolet radiation and thermal cycling. Following the exposures, the mechanical integrity and optical properties of the candidates were investigated using Optical Microscopy, Scanning Electron Microscopy (SEM), and a Laboratory Portable Spectroreflectometer (LPSR). Based on the results of these simulations and analyses, the FRB selected a replacement material and two alternates that showed the highest likelihood of providing the requisite thermal properties and surviving for ten years in orbit.q

Solid film lubricants and thermal control coatings flown aboard the EOIM-3 MDA sub-experiment

NASA Technical Reports Server (NTRS)

Murphy, Taylor J.; David, Kaia E.; Babel, Hank W.

1995-01-01

Additional experimental data were desired to support the selection of candidate thermal control coatings and solid film lubricants for the McDonnell Douglas Aerospace (MDA) Space Station hardware. The third Evaluation of Oxygen Interactions With Materials Mission (EOIM-3) flight experiment presented an opportunity to study the effects of the low Earth orbit environment on thermal control coatings and solid film lubricants. MDA provided five solid film lubricants and two anodic thermal control coatings for EOIM-3. The lubricant sample set consisted of three solid film lubricants with organic binders one solid film lubricant with an inorganic binder, and one solid film lubricant with no binder. The anodize coating sample set consisted of undyed sulfuric acid anodize and cobalt sulfide dyed sulfuric acid anodize, each on two different substrate aluminum alloys. The organic and inorganic binders in the solid film lubricants experienced erosion, and the lubricating pigments experienced oxidation. MDA is continuing to assess the effect of exposure to the low Earth orbit environment on the life and friction properties of the lubricants. Results to date support the design practice of shielding solid film lubricants from the low Earth orbit environment. Post-flight optical property analysis of the anodized specimens indicated that there were limited contamination effects and some atomic oxygen and ultraviolet radiation effects. These effects appeared to be within the values predicted by simulated ground testing and analysis of these materials, and they were different for each coating and substrate.

Lightning Effects in the Payload Changeout Room

NASA Technical Reports Server (NTRS)

Thomas, Garland L.; Fisher, Franklin A.; Collier, Richard S.; Medelius, Pedro J.

1997-01-01

Analytical and empirical studies have been performed to provide better understanding of the electromagnetic environment inside the Payload Changeout Room and Orbiter payload bay resulting from lightning strikes to the launch pad lightning protection system. The analytical studies consisted of physical and mathematical modeling of the pad structure and the Payload Changeout Room. Empirical testing was performed using a lightning simulator to simulate controlled (8 kA) lightning strikes to the catenary wire lightning protection system. In addition to the analyses and testing listed above, an analysis of the configuration with the vehicle present was conducted, in lieu of testing, by the Finite Difference, Time Domain method.

Collisional cascading - The limits of population growth in low earth orbit

NASA Technical Reports Server (NTRS)

Kessler, Donald J.

1991-01-01

Random collisions between made-made objects in earth orbit will lead to a significant source of orbital debris, but there are a number of uncertainties in these models, and additional analysis and data are required to fully characterize the future environment. However, the nature of these uncertainties are such that while the future environment is uncertain, the fact that collisions will control the future environment is less uncertain. The data that already exist is sufficient to show that cascading collisions will control the future debris environment with no, or very minor increases in the current low-earth-orbit population. Two populations control this process: explosion fragments and expended rocket bodies and payloads. Practices are already changing to limit explosions in low earth orbit; it is necessary to begin limiting the number of expended rocket bodies and payloads in orbit.

Algorithms for Autonomous GPS Orbit Determination and Formation Flying: Investigation of Initialization Approaches and Orbit Determination for HEO

NASA Technical Reports Server (NTRS)

Axelrad, Penina; Speed, Eden; Leitner, Jesse A. (Technical Monitor)

2002-01-01

This report summarizes the efforts to date in processing GPS measurements in High Earth Orbit (HEO) applications by the Colorado Center for Astrodynamics Research (CCAR). Two specific projects were conducted; initialization of the orbit propagation software, GEODE, using nominal orbital elements for the IMEX orbit, and processing of actual and simulated GPS data from the AMSAT satellite using a Doppler-only batch filter. CCAR has investigated a number of approaches for initialization of the GEODE orbit estimator with little a priori information. This document describes a batch solution approach that uses pseudorange or Doppler measurements collected over an orbital arc to compute an epoch state estimate. The algorithm is based on limited orbital element knowledge from which a coarse estimate of satellite position and velocity can be determined and used to initialize GEODE. This algorithm assumes knowledge of nominal orbital elements, (a, e, i, omega, omega) and uses a search on time of perigee passage (tau(sub p)) to estimate the host satellite position within the orbit and the approximate receiver clock bias. Results of the method are shown for a simulation including large orbital uncertainties and measurement errors. In addition, CCAR has attempted to process GPS data from the AMSAT satellite to obtain an initial estimation of the orbit. Limited GPS data have been received to date, with few satellites tracked and no computed point solutions. Unknown variables in the received data have made computations of a precise orbit using the recovered pseudorange difficult. This document describes the Doppler-only batch approach used to compute the AMSAT orbit. Both actual flight data from AMSAT, and simulated data generated using the Satellite Tool Kit and Goddard Space Flight Center's Flight Simulator, were processed. Results for each case and conclusion are presented.

Characterization of the cataloged Fengyun-1C fragments and their long-term effect on the LEO environment

NASA Astrophysics Data System (ADS)

Liou, J.-C.; Johnson, N. L.

2009-05-01

The intentional breakup of Fengyun-1C on 11 January 2007 created the most severe orbital debris cloud in history. The altitude where the event occurred was probably the worst location for a major breakup in the low Earth orbit (LEO) region, since it was already highly populated with operational satellites and debris generated from previous breakups. The addition of so many fragments not only poses a realistic threat to operational satellites in the region, but also increases the instability (i.e., collision cascade effect) of the debris population there. Detailed analysis of the large Fengyun-1C fragments indicates that their size and area-to-mass ratio (A/M) distributions are very different from those of other known events. About half of the fragments appear to be composed of light-weight materials and more than 100 of them have A/M values exceeding 1 m 2/kg, consistent with thermal blanket and solar panel pieces. In addition, the orbital elements of the fragments suggest non-trivial velocity gain by the fragment cloud during the impact. These important characteristics were incorporated into numerical simulations to assess the long-term impact of the Fengyun-1C fragments to the LEO debris environment. The collision probabilities between the Fengyun-1C fragments and the rest of the catalog population and the population growth in the low Earth orbit region in the next 100 years are summarized in the paper.

Proton Upset Monte Carlo Simulation

NASA Technical Reports Server (NTRS)

O'Neill, Patrick M.; Kouba, Coy K.; Foster, Charles C.

2009-01-01

The Proton Upset Monte Carlo Simulation (PROPSET) program calculates the frequency of on-orbit upsets in computer chips (for given orbits such as Low Earth Orbit, Lunar Orbit, and the like) from proton bombardment based on the results of heavy ion testing alone. The software simulates the bombardment of modern microelectronic components (computer chips) with high-energy (.200 MeV) protons. The nuclear interaction of the proton with the silicon of the chip is modeled and nuclear fragments from this interaction are tracked using Monte Carlo techniques to produce statistically accurate predictions.

Modeling of the Orbital Debris Environment Risks in the Past, Present, and Future

NASA Technical Reports Server (NTRS)

Matney, Mark

2016-01-01

Despite of the tireless work by space surveillance assets, much of the Earth debris environment is not easily measured or tracked. For every object that is in an orbit we can track, there are hundreds of small debris that are too small to be tracked but still large enough to damage spacecraft. In addition, even if we knew today's environment with perfect knowledge, the debris environment is dynamic and would change tomorrow. Therefore, orbital debris scientists rely on numerical modeling to understand the nature of the debris environment and its risk to space operations throughout Earth orbit and into the future. This talk will summarize the ways in which modeling complements measurements to help give us a better picture of what is occurring in Earth orbit, and helps us to better conduct current and future space operations.

Comparison of Orbiter PRCS Plume Flow Fields Using CFD and Modified Source Flow Codes

NASA Technical Reports Server (NTRS)

Rochelle, Wm. C.; Kinsey, Robin E.; Reid, Ethan A.; Stuart, Phillip C.; Lumpkin, Forrest E.

1997-01-01

The Space Shuttle Orbiter will use Reaction Control System (RCS) jets for docking with the planned International Space Station (ISS). During approach and backout maneuvers, plumes from these jets could cause high pressure, heating, and thermal loads on ISS components. The object of this paper is to present comparisons of RCS plume flow fields used to calculate these ISS environments. Because of the complexities of 3-D plumes with variable scarf-angle and multi-jet combinations, NASA/JSC developed a plume flow-field methodology for all of these Orbiter jets. The RCS Plume Model (RPM), which includes effects of scarfed nozzles and dual jets, was developed as a modified source-flow engineering tool to rapidly generate plume properties and impingement environments on ISS components. This paper presents flow-field properties from four PRCS jets: F3U low scarf-angle single jet, F3F high scarf-angle single jet, DTU zero scarf-angle dual jet, and F1F/F2F high scarf-angle dual jet. The RPM results compared well with plume flow fields using four CFD programs: General Aerodynamic Simulation Program (GASP), Cartesian (CART), Unified Solution Algorithm (USA), and Reacting and Multi-phase Program (RAMP). Good comparisons of predicted pressures are shown with STS 64 Shuttle Plume Impingement Flight Experiment (SPIFEX) data.

The Solid Rocket Motor Slag Population: Results of a Radar-based Regressive Statistical Evaluation

NASA Technical Reports Server (NTRS)

Horstman, Matthew F.; Xu, Yu-Lin

2008-01-01

Solid rocket motor (SRM) slag has been identified as a significant source of man-made orbital debris. The propensity of SRMs to generate particles of 100 m and larger has caused concern regarding their contribution to the debris environment. Radar observation, rather than in-situ gathered evidence, is currently the only measurable source for the NASA/ODPO model of the on-orbit slag population. This simulated model includes the time evolution of the resultant orbital populations using a historical database of SRM launches, propellant masses, and estimated locations and times of tail-off. However, due to the small amount of observational evidence, there can be no direct comparison to check the validity of this model. Rather than using the assumed population developed from purely historical and physical assumptions, a regressional approach was used which utilized the populations observed by the Haystack radar from 1996 to present. The estimated trajectories from the historical model of slag sources, and the corresponding plausible detections by the Haystack radar, were identified. Comparisons with observational data from the ensuing years were made, and the SRM model was altered with respect to size and mass production of slag particles to reflect the historical data obtained. The result is a model SRM population that fits within the bounds of the observed environment.

Skylab Shroud in the Space Power Facility

NASA Image and Video Library

1970-12-21

The 56-foot tall, 24,400-pound Skylab shroud installed in the Space Power Facility’s vacuum chamber at the National Aeronautics and Space Administration’s (NASA) Plum Brook Station. The Space Power Facility, which began operations in 1969, is the largest high vacuum chamber ever built. The chamber is 100 feet in diameter and 120 feet high. It can produce a vacuum deep enough to simulate the conditions at 300 miles altitude. The Space Power Facility was originally designed to test nuclear-power sources for spacecraft during long durations in a space atmosphere, but it was never used for that purpose. Payload shrouds are aerodynamic fairings to protect the payload during launch and ascent to orbit. The Skylab mission utilized the largest shroud ever attempted. Unlike previous launches, the shroud would not be jettisoned until the spacecraft reached orbit. NASA engineers designed these tests to verify the dynamics of the jettison motion in a simulated space environment. Fifty-four runs and three full-scale jettison tests were conducted from mid-September 1970 to June 1971. The shroud behaved as its designers intended, the detonators all fired, and early design issues were remedied by the final test. The Space Power Facility continues to operate today. The facility can sustain a high vacuum; simulate solar radiation via a 4-megawatt quartz heat lamp array, solar spectrum by a 400-kilowatt arc lamp, and cold environments. Test programs at the facility include high-energy experiments, shroud separation tests, Mars Lander system tests, deployable Solar Sail tests and International Space Station hardware tests.

Orbiting Rainbows Simulation

NASA Image and Video Library

2015-04-22

This simulated image shows how a cloud of glitter in geostationary orbit would be illuminated and controlled by two laser beams. As the cloud orbits Earth, grains scatter the sun's light at different angles like many tiny prisms, similar to how rainbows are produced from light being dispersed by water droplets. That is why the project concept is called "Orbiting Rainbows." The cloud functions like a reflective surface, allowing the exoplanet (displayed in the bottom right) to be imaged. The orbit path is shown in the top right. On the bottom left, Earth's image is seen behind the cloud. To image an exoplanet, the cloud would need to have a diameter of nearly 98 feet (30 meters). This simulation confines the cloud to a 3.3 x 3.3 x 3.3 foot volume (1 x 1 x 1 meter volume) to simplify the computations. The elements of the orbiting telescope are not to scale. Orbiting Rainbows is currently in Phase II development through the NASA Innovative Advanced Concepts (NIAC) Program. It was one of five technology proposals chosen for continued study in 2014. In the current phase, Orbiting Rainbows researchers are conducting small-scale ground experiments to demonstrate how granular materials can be manipulated using lasers and simulations of how the imaging system would behave in orbit. http://photojournal.jpl.nasa.gov/catalog/PIA19318

Virtual Environment User Interfaces to Support RLV and Space Station Simulations in the ANVIL Virtual Reality Lab

NASA Technical Reports Server (NTRS)

Dumas, Joseph D., II

1998-01-01

Several virtual reality I/O peripherals were successfully configured and integrated as part of the author's 1997 Summer Faculty Fellowship work. These devices, which were not supported by the developers of VR software packages, use new software drivers and configuration files developed by the author to allow them to be used with simulations developed using those software packages. The successful integration of these devices has added significant capability to the ANVIL lab at MSFC. In addition, the author was able to complete the integration of a networked virtual reality simulation of the Space Shuttle Remote Manipulator System docking Space Station modules which was begun as part of his 1996 Fellowship. The successful integration of this simulation demonstrates the feasibility of using VR technology for ground-based training as well as on-orbit operations.

Radiation model predictions and validation using LDEF satellite data

NASA Technical Reports Server (NTRS)

Armstrong, T. W.; Colborn, B. L.

1993-01-01

Predictions and comparisons with the radiation dose measurements on Long Duration Exposure Facility (LDEF) by thermoluminescent dosimeters were made to evaluate the accuracy of models currently used in defining the ionizing radiation environment for low Earth orbit missions. The calculations include a detailed simulation of the radiation exposure (altitude and solar cycle variations, directional dependence) and shielding effects (three-dimensional LDEF geometry model) so that differences in the predicted and observed doses can be attributed to environment model uncertainties. The LDEF dose data are utilized to assess the accuracy of models describing the trapped proton flux, the trapped proton directionality, and the trapped electron flux.

Investigation of high voltage spacecraft system interactions with plasma environments

NASA Technical Reports Server (NTRS)

Stevens, N. J.; Berkopec, F. D.; Purvis, C. K.; Grier, N.; Staskus, J. V.

1978-01-01

An experimental investigation was undertaken for insulator and conductor test surfaces biased up to + or - 1kV in a simulated low earth orbit charged particle environment. It was found that these interactions are controlled by the insulator surfaces surrounding the biased conductors. For positive applied voltages the electron current collection can be enhanced by the insulators. For negative applied voltages the insulator surface confines the voltage to the conductor region. Understanding these interactions and the technology to control their impact on system operation is essential to the design of solar cell arrays for ion drive propulsion applications that use direct drive power processing.

Planetary and Space Simulation Facilities PSI at DLR for Astrobiology

NASA Astrophysics Data System (ADS)

Rabbow, E.; Rettberg, P.; Panitz, C.; Reitz, G.

2008-09-01

Ground based experiments, conducted in the controlled planetary and space environment simulation facilities PSI at DLR, are used to investigate astrobiological questions and to complement the corresponding experiments in LEO, for example on free flying satellites or on space exposure platforms on the ISS. In-orbit exposure facilities can only accommodate a limited number of experiments for exposure to space parameters like high vacuum, intense radiation of galactic and solar origin and microgravity, sometimes also technically adapted to simulate extraterrestrial planetary conditions like those on Mars. Ground based experiments in carefully equipped and monitored simulation facilities allow the investigation of the effects of simulated single environmental parameters and selected combinations on a much wider variety of samples. In PSI at DLR, international science consortia performed astrobiological investigations and space experiment preparations, exposing organic compounds and a wide range of microorganisms, reaching from bacterial spores to complex microbial communities, lichens and even animals like tardigrades to simulated planetary or space environment parameters in pursuit of exobiological questions on the resistance to extreme environments and the origin and distribution of life. The Planetary and Space Simulation Facilities PSI of the Institute of Aerospace Medicine at DLR in Köln, Germany, providing high vacuum of controlled residual composition, ionizing radiation of a X-ray tube, polychromatic UV radiation in the range of 170-400 nm, VIS and IR or individual monochromatic UV wavelengths, and temperature regulation from -20°C to +80°C at the sample size individually or in selected combinations in 9 modular facilities of varying sizes are presented with selected experiments performed within.

Effects on the orbital debris environment due to solar activity

NASA Technical Reports Server (NTRS)

Kessler, Donald J.; Anz-Meador, Phillip D.

1990-01-01

The rate that earth-orbiting debris is removed from the environment is dependent on a number of factors which include orbital altitude and solar activity. It is generally believed that at lower altitudes and especially during periods of high solar activity, debris generated in the past will be eliminated from the environment. While some debris is eliminated, most is replaced by old debris from higher altitudes or new debris from recent launches. Some low altitude debris, which would reenter if the debris were in circular orbits, does not reenter because the debris is in higher-energy elliptical orbits.

Real-time tracking of objects for a KC-135 microgravity experiment

NASA Technical Reports Server (NTRS)

Littlefield, Mark L.

1994-01-01

The design of a visual tracking system for use on the Extra-Vehicular Activity Helper/Retriever (EVAHR) is discussed. EVAHR is an autonomous robot designed to perform numerous tasks in an orbital microgravity environment. Since the ability to grasp a freely translating and rotating object is vital to the robot's mission, the EVAHR must analyze range image generated by the primary sensor. This allows EVAHR to locate and focus its sensors so that an accurate set of object poses can be determined and a grasp strategy planned. To test the visual tracking system being developed, a mathematical simulation was used to model the space station environment and maintain dynamics on the EVAHR and any other free floating objects. A second phase of the investigation consists of a series of experiments carried out aboard a KC-135 aircraft flying a parabolic trajectory to simulate microgravity.

Effect of magnetically simulated zero-gravity and enhanced gravity on the walk of the common fruitfly†

PubMed Central

Hill, Richard J. A.; Larkin, Oliver J.; Dijkstra, Camelia E.; Manzano, Ana I.; de Juan, Emilio; Davey, Michael R.; Anthony, Paul; Eaves, Laurence; Medina, F. Javier; Marco, Roberto; Herranz, Raul

2012-01-01

Understanding the effects of gravity on biological organisms is vital to the success of future space missions. Previous studies in Earth orbit have shown that the common fruitfly (Drosophila melanogaster) walks more quickly and more frequently in microgravity, compared with its motion on Earth. However, flight preparation procedures and forces endured on launch made it difficult to implement on the Earth's surface a control that exposed flies to the same sequence of major physical and environmental changes. To address the uncertainties concerning these behavioural anomalies, we have studied the walking paths of D. melanogaster in a pseudo-weightless environment (0g*) in our Earth-based laboratory. We used a strong magnetic field, produced by a superconducting solenoid, to induce a diamagnetic force on the flies that balanced the force of gravity. Simultaneously, two other groups of flies were exposed to a pseudo-hypergravity environment (2g*) and a normal gravity environment (1g*) within the spatially varying field. The flies had a larger mean speed in 0g* than in 1g*, and smaller in 2g*. The mean square distance travelled by the flies grew more rapidly with time in 0g* than in 1g*, and slower in 2g*. We observed no other clear effects of the magnetic field, up to 16.5 T, on the walks of the flies. We compare the effect of diamagnetically simulated weightlessness with that of weightlessness in an orbiting spacecraft, and identify the cause of the anomalous behaviour as the altered effective gravity. PMID:22219396

Effect of magnetically simulated zero-gravity and enhanced gravity on the walk of the common fruitfly.

PubMed

Hill, Richard J A; Larkin, Oliver J; Dijkstra, Camelia E; Manzano, Ana I; de Juan, Emilio; Davey, Michael R; Anthony, Paul; Eaves, Laurence; Medina, F Javier; Marco, Roberto; Herranz, Raul

2012-07-07

Understanding the effects of gravity on biological organisms is vital to the success of future space missions. Previous studies in Earth orbit have shown that the common fruitfly (Drosophila melanogaster) walks more quickly and more frequently in microgravity, compared with its motion on Earth. However, flight preparation procedures and forces endured on launch made it difficult to implement on the Earth's surface a control that exposed flies to the same sequence of major physical and environmental changes. To address the uncertainties concerning these behavioural anomalies, we have studied the walking paths of D. melanogaster in a pseudo-weightless environment (0g*) in our Earth-based laboratory. We used a strong magnetic field, produced by a superconducting solenoid, to induce a diamagnetic force on the flies that balanced the force of gravity. Simultaneously, two other groups of flies were exposed to a pseudo-hypergravity environment (2g*) and a normal gravity environment (1g*) within the spatially varying field. The flies had a larger mean speed in 0g* than in 1g*, and smaller in 2g*. The mean square distance travelled by the flies grew more rapidly with time in 0g* than in 1g*, and slower in 2g*. We observed no other clear effects of the magnetic field, up to 16.5 T, on the walks of the flies. We compare the effect of diamagnetically simulated weightlessness with that of weightlessness in an orbiting spacecraft, and identify the cause of the anomalous behaviour as the altered effective gravity.

An Independent Orbit Determination Simulation for the OSIRIS-REx Asteroid Sample Return Mission

NASA Technical Reports Server (NTRS)

Getzandanner, Kenneth; Rowlands, David; Mazarico, Erwan; Antreasian, Peter; Jackman, Coralie; Moreau, Michael

2016-01-01

After arriving at the near-Earth asteroid (101955) Bennu in late 2018, the OSIRIS-REx spacecraft will execute a series of observation campaigns and orbit phases to accurately characterize Bennu and ultimately collect a sample of pristine regolith from its surface. While in the vicinity of Bennu, the OSIRIS-REx navigation team will rely on a combination of ground-based radiometric tracking data and optical navigation (OpNav) images to generate and deliver precision orbit determination products. Long before arrival at Bennu, the navigation team is performing multiple orbit determination simulations and thread tests to verify navigation performance and ensure interfaces between multiple software suites function properly. In this paper, we will summarize the results of an independent orbit determination simulation of the Orbit B phase of the mission performed to test the interface between the OpNav image processing and orbit determination software packages.

A Review of Microgravity Levels on Ten OARE Shuttle Missions

NASA Technical Reports Server (NTRS)

McPherson, Kevin M.

1998-01-01

The Orbital Acceleration Research Experiment (OARE) is an accelerometer package with nano-g sensitivity and on-orbit bias calibration capabilities. The OARE consists of a three axis miniature electrostatic accelerometer (MESA), a full in-flight bias and scale factor calibration station, and an on-board microprocessor for experiment control and data storage. Originally designed to measure and record the aerodynamic acceleration environment of the NASA Space Shuttles during re-entry, the OARE has been used on ten shuttle missions to measure the quasi-steady acceleration environment (<1 Hz) of the Orbiter while in low-Earth orbit. The effects on the quasi-steady acceleration environment from Orbiter systems, Orbiter attitude, Orbiter altitude, and crew activity are well understood as a result of these ten shuttle missions. This knowledge of the quasi-steady acceleration realm has direct application to understanding the quasi-steady acceleration environment expected for the International Space Station (ISS). This paper will summarize the more salient aspects of this quasi-steady acceleration knowledge base.

Extensive Radiation Shielding Analysis for Different Spacecraft Orbits

NASA Astrophysics Data System (ADS)

Çay, Yiǧit; Kaymaz, Zerefsan

2016-07-01

Radiation environment around Earth poses a great danger for spacecraft and causes immature de-orbiting or loss of the spacecraft in near Earth space environment. In this study, a student project has been designed to build a CubeSat, PolarBeeSail (PBS), with an orbit having inclination of 80°, 4 Re in perigee and 20 Re in apogee to study the polar magnetospheric environment. An extensive radiation dose analyses were carried out for PBS orbit, and integral and differential fluxes were calculated using SPENVIS tools. A shielding analysis was performed and an optimum Aluminum thickness, 3 mm, was obtained. These results for PBS were then compared for other orbits at different altitudes both for polar and equatorial orbits. For this purpose, orbital characteristics of POES-19 and GOES-15 were used. The resulting proton flux analyses, TID analyses, and further shielding studies were conducted; comparisons and recommendations were made for future design of spacecraft that will use these environments.

Mathematical modeling and SAR simulation multifunction SAR technology efforts

NASA Technical Reports Server (NTRS)

Griffin, C. R.; Estes, J. M.

1981-01-01

The orbital SAR (synthetic aperture radar) simulation data was used in several simulation efforts directed toward advanced SAR development. Efforts toward simulating an operational radar, simulation of antenna polarization effects, and simulation of SAR images at serveral different wavelengths are discussed. Avenues for improvements in the orbital SAR simulation and its application to the development of advanced digital radar data processing schemes are indicated.

Advanced simulation and analysis of a geopotential research mission

NASA Technical Reports Server (NTRS)

Schutz, B. E.

1988-01-01

Computer simulations have been performed for an orbital gradiometer mission to assist in the study of high degree and order gravity field recovery. The simulations were conducted for a satellite in near-circular, frozen orbit at a 160-km altitude using a gravitational field complete to degree and order 360. The mission duration is taken to be 32 days. The simulation provides a set of measurements to assist in the evaluation of techniques developed for the determination of the gravity field. Also, the simulation provides an ephemeris to study available tracking systems to satisfy the orbit determination requirements of the mission.

Improved Estimation of Orbits and Physical Properties of Objects in GEO

NASA Astrophysics Data System (ADS)

Bradley, B.; Axelrad, P.

2013-09-01

Orbital debris is a major concern for satellite operators, both commercial and military. Debris in the geosynchronous (GEO) belt is of particular concern because this unique region is such a valuable, limited resource, and, from the ground we cannot reliably track and characterize GEO objects smaller than 1 meter in diameter. Space-based space surveillance (SBSS) is required to observe GEO objects without weather restriction and with improved viewing geometry. SBSS satellites have thus far been placed in Sun-synchronous orbits. This paper investigates the benefits to GEO orbit determination (including the estimation of mass, area, and shape) that arises from placing observing satellites in geosynchronous transfer orbit (GTO) and a sub-GEO orbit. Recently, several papers have reported on simulation studies to estimate orbits and physical properties; however, these studies use simulated objects and ground-based measurements, often with dense and long data arcs. While this type of simulation provides valuable insight into what is possible, as far as state estimation goes, it is not a very realistic observing scenario and thus may not yield meaningful accuracies. Our research improves upon simulations published to date by utilizing publicly available ephemerides for the WAAS satellites (Anik F1R and Galaxy 15), accurate at the meter level. By simulating and deliberately degrading right ascension and declination observations, consistent with these ephemerides, a realistic assessment of the achievable orbit determination accuracy using GTO and sub-GEO SBSS platforms is performed. Our results show that orbit accuracy is significantly improved as compared to a Sun-synchronous platform. Physical property estimation is also performed using simulated astrometric and photometric data taken from GTO and sub-GEO sensors. Simulations of SBSS-only as well as combined SBSS and ground-based observation tracks are used to study the improvement in area, mass, and shape estimation gained by the proposed systems. Again our work improves upon previous research by investigating realistic observation scheduling scenarios to gain insight into achievable accuracies.

STS-52 MS Jemison, in LES/LEH, during JSC WETF bailout exercise

NASA Technical Reports Server (NTRS)

1992-01-01

STS-52 Columbia, Orbiter Vehicle (OV) 102, Mission Specialist (MS) Tamara E. Jernigan, wearing launch and entry suit (LES) and launch and entry helmet (LEH), listens to a briefing about water landings during an emergency egress (bailout) training exercise in JSC's Weightless Environment Training Facility (WETF) Bldg 29 pool. Jernigan waits her turn to be dropped into the WETF's 25-ft deep pool which will simulate the ocean during of her water landing.

STS-47 Commander Gibson and MS Apt in JSC WETF for bailout exercises

NASA Technical Reports Server (NTRS)

1992-01-01

STS-47 Endeavour, Orbiter Vehicle (OV) 105, Commander Robert L. Gibson, wearing launch and entry suit (LES) and launch and entry helmet (LEH), listens to instructions before participating in launch emergency egress (bailout) exercises in JSC's Weightless Environment Trainining Facility (WETF) Bldg 29. Mission Specialist (MS) Jerome Apt, wearing LES and LES parachute, is seen in the background. This exercise is conducted in the WETF pool to simulate a water landing.

STS-52 Payload Specialist MacLean floats in pool during JSC bailout exercises

NASA Technical Reports Server (NTRS)

1992-01-01

STS-52 Columbia, Orbiter Vehicle (OV) 102, Payload Specialist Steven G. MacLean, wearing launch and entry suit (LES) and clamshell helmet, is assisted by SCUBA-equipped divers as he floats in pool during emergency egress (bailout) training exercises in JSC's Weightless Environment Training Facility Bldg 29. Bailout exercises utilize the WETF's 25-foot deep pool as the ocean during this water landing simulation. MacLean represents the Canadian Space Agency (CSA).

STS-55 MS3 Harris listens to technician during JSC WETF egress exercises

NASA Technical Reports Server (NTRS)

1992-01-01

STS-55 Columbia, Orbiter Vehicle (OV) 102, Mission Specialist 3 (MS3) Bernard A. Harris, Jr, wearing launch and entry suit (LES), launch and entry helmet (LEH), and parachute, listens to technician Karen Porter's instructions prior to launch emergency egress (bailout) exercises. The session, held in JSC's Weightless Environment Training Facility (WETF) Bldg 29, used the facility's 25-foot deep pool to simulate the ocean as Harris and other crewmembers practiced water bailout procedures.

KENNEDY SPACE CENTER, FLA. - A helicopter approaches an orbiter crew compartment mock-up as part of a “Mode VII” emergency landing simulation at Kennedy Space Center. The purpose is to exercise emergency preparedness personnel, equipment and facilities in rescuing astronauts from a downed orbiter and providing immediate medical attention. This simulation presents an orbiter that has crashed short of the Shuttle Landing Facility in a wooded area 2-1/2 miles south of Runway 33. Emergency crews will respond to the volunteer “astronauts” simulating various injuries. Rescuers must remove the crew, provide triage and transport to hospitals those who need further treatment. Local hospitals are participating in the exercise.

NASA Image and Video Library

2004-02-18

KENNEDY SPACE CENTER, FLA. - A helicopter approaches an orbiter crew compartment mock-up as part of a “Mode VII” emergency landing simulation at Kennedy Space Center. The purpose is to exercise emergency preparedness personnel, equipment and facilities in rescuing astronauts from a downed orbiter and providing immediate medical attention. This simulation presents an orbiter that has crashed short of the Shuttle Landing Facility in a wooded area 2-1/2 miles south of Runway 33. Emergency crews will respond to the volunteer “astronauts” simulating various injuries. Rescuers must remove the crew, provide triage and transport to hospitals those who need further treatment. Local hospitals are participating in the exercise.

A navigation and control system for an autonomous rescue vehicle in the space station environment

NASA Technical Reports Server (NTRS)

Merkel, Lawrence

1991-01-01

A navigation and control system was designed and implemented for an orbital autonomous rescue vehicle envisioned to retrieve astronauts or equipment in the case that they become disengaged from the space station. The rescue vehicle, termed the Extra-Vehicular Activity Retriever (EVAR), has an on-board inertial measurement unit ahd GPS receivers for self state estimation, a laser range imager (LRI) and cameras for object state estimation, and a data link for reception of space station state information. The states of the retriever and objects (obstacles and the target object) are estimated by inertial state propagation which is corrected via measurements from the GPS, the LRI system, or the camera system. Kalman filters are utilized to perform sensor fusion and estimate the state propagation errors. Control actuation is performed by a Manned Maneuvering Unit (MMU). Phase plane control techniques are used to control the rotational and translational state of the retriever. The translational controller provides station-keeping or motion along either Clohessy-Wiltshire trajectories or straight line trajectories in the LVLH frame of any sufficiently observed object or of the space station. The software was used to successfully control a prototype EVAR on an air bearing floor facility, and a simulated EVAR operating in a simulated orbital environment. The design of the navigation system and the control system are presented. Also discussed are the hardware systems and the overall software architecture.

MCC level C formulation requirements. Shuttle TAEM guidance and flight control, STS-1 baseline

NASA Technical Reports Server (NTRS)

Carman, G. L.; Montez, M. N.

1980-01-01

The TAEM guidance and body rotational dynamics models required for the MCC simulation of the TAEM mission phase are defined. This simulation begins at the end of the entry phase and terminates at TAEM autoland interface. The logic presented is the required configuration for the first shuttle orbital flight (STS-1). The TAEM guidance is simulated in detail. The rotational dynamics simulation is a simplified model that assumes that the commanded rotational rates can be achieved in the integration interval. Thus, the rotational dynamics simulation is essentially a simulation of the autopilot commanded rates and integration of these rates to determine orbiter attitude. The rotational dynamics simulation also includes a simulation of the speedbrake deflection. The body flap and elevon deflections are computed in the orbiter aerodynamic simulation.

CONSTELL: NASA's Satellite Constellation Model

NASA Technical Reports Server (NTRS)

Theall, Jeffrey R.; Krisko, Paula H.; Opiela, John N.; McKay, Gordon A. (Technical Monitor)

1999-01-01

The CONSTELL program represents an initial effort by the orbital debris modeling group at NASA/JSC to address the particular issues and problems raised by the presence of LEO satellite constellations. It was designed to help NASA better understand the potential orbital debris consequences of having satellite constellations operating in the future in LEO. However, it could also be used by constellation planners to evaluate architecture or design alternatives that might lessen debris consequences for their constellation or lessen the debris effects on other users of space. CONSTELL is designed to perform debris environment projections rapidly so it can support parametric assessments involving either the constellations themselves or the background environment which represents non-constellation users of the space. The projections need to be calculated quickly because a number of projections are often required to adequately span the parameter space of interest. To this end CONSTELL uses the outputs of other NASA debris environment models as inputs, thus doing away with the need for time consuming upfront calculations. Specifically, CONSTELL uses EVOLVE or ORDEM96 debris spatial density results as its background environment, debris cloud snapshot templates to simulate debris cloud propagation, and time dependent orbit profiles of the intact non- functional constellation spacecraft and upper stages. In this paper the environmental consequences of the deployment of particular LEO satellite constellations using the CONSTELL model will be evaluated. Constellations that will undergo a parametric assessment will reflect realistic parameter values. Among other results the increase in loss rate of non-constellation spacecraft, the number of collisions involving constellation elements, and the replacement rate of constellation satellites as a result of debris impact will be presented.

System results from FRECOPA

NASA Technical Reports Server (NTRS)

Durin, Christian; Berthoud, Lucinda; Mandeville, Jean-Claude

1995-01-01

The work carried out over the past three years on FRECOPA and the LDEF has enabled a large quantity of information to be collected, part of which has already been exploited. As far as CNES is concerned, the major spin-offs of this mission mainly focus on the orbital environment and the behavior of materials in such an environment. With respect to the environment, the authors shall develop the lessons learned from expert appraisals on impacts by microparticles, which are the main feature observed in this area. As for the materials, the results show a variety of behavior when subjected to the space environment and even now constitute a wealth of information for the designing and validation of future mechanical systems. Apart from these direct spin-offs, there are repercussions on in-flight and ground testing, the calibration of test benches and improvements to simulation models.

Integrated Simulation Design Challenges to Support TPS Repair Operations

NASA Technical Reports Server (NTRS)

Quiocho, Leslie J.; Crues, Edwin Z.; Huynh, An; Nguyen, Hung T.; MacLean, John

2005-01-01

During the Orbiter Repair Maneuver (ORM) operations planned for Return to Flight (RTF), the Shuttle Remote Manipulator System (SRMS) must grapple the International Space Station (ISS), undock the Orbiter, maneuver it through a long duration trajectory, and orient it to an EVA crewman poised at the end of the Space Station Remote Manipulator System (SSRMS) to facilitate the repair of the Thermal Protection System (TPS). Once repair has been completed and confirmed, then the SRMS proceeds back through the trajectory to dock the Orbiter to the Orbiter Docking System. In order to support analysis of the complex dynamic interactions of the integrated system formed by the Orbiter, ISS, SRMS, and SSRMS during the ORM, simulation tools used for previous 'nominal' mission support required substantial enhancements. These upgrades were necessary to provide analysts with the capabilities needed to study integrated system performance. This paper discusses the simulation design challenges encountered while developing simulation capabilities to mirror the ORM operations. The paper also describes the incremental build approach that was utilized, starting with the subsystem simulation elements and integration into increasing more complex simulations until the resulting ORM worksite dynamics simulation had been assembled. Furthermore, the paper presents an overall integrated simulation V&V methodology based upon a subsystem level testing, integrated comparisons, and phased checkout.

Simulation of interference between Earth stations and Earth-orbiting satellites

NASA Technical Reports Server (NTRS)

Bishop, D. F.

1994-01-01

It is often desirable to determine the potential for radio frequency interference between earth stations and orbiting spacecraft. This information can be used to select frequencies for radio systems to avoid interference or it can be used to determine if coordination between radio systems is necessary. A model is developed that will determine the statistics of interference between earth stations and elliptical orbiting spacecraft. The model uses orbital dynamics, detailed antenna patterns, and spectral characteristics to obtain accurate levels of interference at the victim receiver. The model is programmed into a computer simulation to obtain long-term statistics of interference. Two specific examples are shown to demonstrate the model. The first example is a simulation of interference from a fixed-satellite earth station to an orbiting scatterometer receiver. The second example is a simulation of interference from earth-exploration satellites to a deep-space earth station.

A system for simulating aerial or orbital TV observations of geographic patterns

NASA Technical Reports Server (NTRS)

Latham, J. P.

1972-01-01

A system which simulates observation of the earth surface by aerial or orbiting television devices has been developed. By projecting color slides of photographs taken by aircraft and orbiting sensors upon a rear screen system, and altering scale of projected image, screen position, or TV camera position, it is possible to simulate alternatives of altitude, or optical systems. By altering scan line patterns in COHU 3200 series camera from 525 to 945 scan lines, it is possible to study implications of scan line resolution upon the detection and analysis of geographic patterns observed by orbiting TV systems.

Aerothermal Analysis and Design of the Gravity Recovery and Climate Experiment (GRACE) Spacecraft

NASA Technical Reports Server (NTRS)

Mazanek, Daniel D.; Kumar, Renjith R.; Qu, Min; Seywald, Hans

2000-01-01

The Gravity Recovery and Climate Experiment (GRACE) primary mission will be performed by making measurements of the inter-satellite range change between two co-planar, low altitude near-polar orbiting satellites. Understanding the uncertainties in the disturbance environment, particularly the aerodynamic drag and torques, is critical in several mission areas. These include an accurate estimate of the spacecraft orbital lifetime, evaluation of spacecraft attitude control requirements, and estimation of the orbital maintenance maneuver frequency necessitated by differences in the drag forces acting on both satellites. The FREEMOL simulation software has been developed and utilized to analyze and suggest design modifications to the GRACE spacecraft. Aerodynamic accommodation bounding analyses were performed and worst-case envelopes were obtained for the aerodynamic torques and the differential ballistic coefficients between the leading and trailing GRACE spacecraft. These analyses demonstrate how spacecraft aerodynamic design and analysis can benefit from a better understanding of spacecraft surface accommodation properties, and the implications for mission design constraints such as formation spacing control.

Ecology of dark matter haloes - II. Effects of interactions on the alignment of halo pairs

NASA Astrophysics Data System (ADS)

L'Huillier, Benjamin; Park, Changbom; Kim, Juhan

2017-04-01

We use the Horizon Run 4 cosmological N-body simulation to study the effects of distant and close interactions on the alignments of the shapes, spins and orbits of targets haloes with their neighbours, and their dependence on the local density environment and neighbour separation. Interacting targets have a significantly lower spin and higher sphericity and oblateness than all targets. Interacting pairs initially have antiparallel spins, but the spins develop parallel alignment as time goes on. Neighbours tend to evolve in the plane of rotation of the target, and in the direction of the major axis of prolate haloes. Moreover, interactions are preferentially radial, while pairs with non-radial orbits are preferentially prograde. The alignment signals are stronger at high mass and for close separations, and independent of the large-scale density. Positive alignment signals are found at redshifts up to 4, and increase with decreasing redshifts. Moreover, the orbits tend to become prograde at low redshift, while no alignment is found at high redshift (z = 4).

Trajectory Design for the Phobos and Deimos & Mars Environment Spacecraft

NASA Technical Reports Server (NTRS)

Genova, Anthony L.; Korsmeyer, David J.; Loucks, Michel E.; Yang, Fan Yang; Lee, Pascal

2016-01-01

The presented trajectory design and analysis was performed for the Phobos and Deimos & Mars Environment (PADME) mission concept as part of a NASA proposal submission managed by NASA Ames Research Center in the 2014-2015 timeframe. The PADME spacecraft would be a derivative of the successfully flown Lunar Atmosphere & Dust Environment Explorer (LADEE) spacecraft. While LADEE was designed to enter low-lunar orbit, the PADME spacecraft would instead enter an elliptical Mars orbit of 2-week period. This Mars orbit would pass by Phobos near periapsis on successive orbits and then raise periapsis to yield close approaches of Deimos every orbit thereafter.

X-Ray Imaging Study

NASA Technical Reports Server (NTRS)

OBrien, Susan K.; Workman, Gary L.

1996-01-01

The space environment in which the Space Station Freedom and other space platforms will orbit is truly a hostile environment. For example, the currently estimated integral fluence for electrons above 1 Mev at 2000 nautical miles is above 2 x 1O(exp 10) electrons/sq cm/day and the proton integral fluence is above 1 x 10(exp 9) protons/sq cm/day. At the 200 - 400 nautical miles, which is more representative of the altitude which will provide the environment for the Space Station, each of these fluences will be proportionally less; however, the data indicates that the radiation environment will obviously have an effect on structural materials exposed to the environment for long durations. The effects of this combined environment is the issue which needs to be understood for the long term exposure of structures in space. At the same time, there will be substantial potential for collisions between the space platforms and space debris. The current NASA catalogue contains over 4500 objects floating in space which are not considered payloads. This debris can have significant effects on collision with orbiting spacecraft. In order to better understand the effect of these hostile phenomena on spacecraft, several types of studies are being performed to simulate at some level the effect of the environment. In particular the study of debris clouds produced by hypervelocity impact on the various surfaces anticipated on the Space Station is very important at this point in time. The need to assess the threat of such debris clouds on space structures is an on-going activity. The Space Debris Impact facility in Building 4612 provides a test facility to monitor the types of damage produced with hypervelocity impact. These facilities are used to simulate space environmental effects from energetic particles. Flash radiography or x-ray imaging has traditionally provided such information and as such has been an important tool for recording damage in situ with the event. The proper operation of the system can provide much useful information with respect to parametric analysis of the hypervelocity experiment. The following report outlines the procedures developed to optimize the operation of the x-ray imaging system and its operational characteristics.

Robotic space simulation integration of vision algorithms into an orbital operations simulation

NASA Technical Reports Server (NTRS)

Bochsler, Daniel C.

1987-01-01

In order to successfully plan and analyze future space activities, computer-based simulations of activities in low earth orbit will be required to model and integrate vision and robotic operations with vehicle dynamics and proximity operations procedures. The orbital operations simulation (OOS) is configured and enhanced as a testbed for robotic space operations. Vision integration algorithms are being developed in three areas: preprocessing, recognition, and attitude/attitude rates. The vision program (Rice University) was modified for use in the OOS. Systems integration testing is now in progress.

The use of computer graphic simulation in the development of on-orbit tele-robotic systems

NASA Technical Reports Server (NTRS)

Fernandez, Ken; Hinman, Elaine

1987-01-01

This paper describes the use of computer graphic simulation techniques to resolve critical design and operational issues for robotic systems used for on-orbit operations. These issues are robot motion control, robot path-planning/verification, and robot dynamics. The major design issues in developing effective telerobotic systems are discussed, and the use of ROBOSIM, a NASA-developed computer graphic simulation tool, to address these issues is presented. Simulation plans for the Space Station and the Orbital Maneuvering Vehicle are presented and discussed.

Retrieved Products from Simulated Hyperspectral Observations of a Hurricane

NASA Technical Reports Server (NTRS)

Susskind, Joel; Kouvaris, Louis; Iredell, Lena; Blaisdell, John

2015-01-01

Demonstrate via Observing System Simulation Experiments (OSSEs) the potential utility of flying high spatial resolution AIRS class IR sounders on future LEO and GEO missions.The study simulates and analyzes radiances for 3 sounders with AIRS spectral and radiometric properties on different orbits with different spatial resolutions: 1) Control run 13 kilometers AIRS spatial resolution at nadir on LEO in Aqua orbit; 2) 2 kilometer spatial resolution LEO sounder at nadir ARIES; 3) 5 kilometers spatial resolution sounder on a GEO orbit, radiances simulated every 72 minutes.

Intelligent Launch and Range Operations Virtual Test Bed (ILRO-VTB)

NASA Technical Reports Server (NTRS)

Bardina, Jorge; Rajkumar, T.

2003-01-01

Intelligent Launch and Range Operations Virtual Test Bed (ILRO-VTB) is a real-time web-based command and control, communication, and intelligent simulation environment of ground-vehicle, launch and range operation activities. ILRO-VTB consists of a variety of simulation models combined with commercial and indigenous software developments (NASA Ames). It creates a hybrid software/hardware environment suitable for testing various integrated control system components of launch and range. The dynamic interactions of the integrated simulated control systems are not well understood. Insight into such systems can only be achieved through simulation/emulation. For that reason, NASA has established a VTB where we can learn the actual control and dynamics of designs for future space programs, including testing and performance evaluation. The current implementation of the VTB simulates the operations of a sub-orbital vehicle of mission, control, ground-vehicle engineering, launch and range operations. The present development of the test bed simulates the operations of Space Shuttle Vehicle (SSV) at NASA Kennedy Space Center. The test bed supports a wide variety of shuttle missions with ancillary modeling capabilities like weather forecasting, lightning tracker, toxic gas dispersion model, debris dispersion model, telemetry, trajectory modeling, ground operations, payload models and etc. To achieve the simulations, all models are linked using Common Object Request Broker Architecture (CORBA). The test bed provides opportunities for government, universities, researchers and industries to do a real time of shuttle launch in cyber space.

Intelligent launch and range operations virtual testbed (ILRO-VTB)

NASA Astrophysics Data System (ADS)

Bardina, Jorge; Rajkumar, Thirumalainambi

2003-09-01

Intelligent Launch and Range Operations Virtual Test Bed (ILRO-VTB) is a real-time web-based command and control, communication, and intelligent simulation environment of ground-vehicle, launch and range operation activities. ILRO-VTB consists of a variety of simulation models combined with commercial and indigenous software developments (NASA Ames). It creates a hybrid software/hardware environment suitable for testing various integrated control system components of launch and range. The dynamic interactions of the integrated simulated control systems are not well understood. Insight into such systems can only be achieved through simulation/emulation. For that reason, NASA has established a VTB where we can learn the actual control and dynamics of designs for future space programs, including testing and performance evaluation. The current implementation of the VTB simulates the operations of a sub-orbital vehicle of mission, control, ground-vehicle engineering, launch and range operations. The present development of the test bed simulates the operations of Space Shuttle Vehicle (SSV) at NASA Kennedy Space Center. The test bed supports a wide variety of shuttle missions with ancillary modeling capabilities like weather forecasting, lightning tracker, toxic gas dispersion model, debris dispersion model, telemetry, trajectory modeling, ground operations, payload models and etc. To achieve the simulations, all models are linked using Common Object Request Broker Architecture (CORBA). The test bed provides opportunities for government, universities, researchers and industries to do a real time of shuttle launch in cyber space.

Hardware in-the-Loop Demonstration of Real-Time Orbit Determination in High Earth Orbits

NASA Technical Reports Server (NTRS)

Moreau, Michael; Naasz, Bo; Leitner, Jesse; Carpenter, J. Russell; Gaylor, Dave

2005-01-01

This paper presents results from a study conducted at Goddard Space Flight Center (GSFC) to assess the real-time orbit determination accuracy of GPS-based navigation in a number of different high Earth orbital regimes. Measurements collected from a GPS receiver (connected to a GPS radio frequency (RF) signal simulator) were processed in a navigation filter in real-time, and resulting errors in the estimated states were assessed. For the most challenging orbit simulated, a 12 hour Molniya orbit with an apogee of approximately 39,000 km, mean total position and velocity errors were approximately 7 meters and 3 mm/s respectively. The study also makes direct comparisons between the results from the above hardware in-the-loop tests and results obtained by processing GPS measurements generated from software simulations. Care was taken to use the same models and assumptions in the generation of both the real-time and software simulated measurements, in order that the real-time data could be used to help validate the assumptions and models used in the software simulations. The study makes use of the unique capabilities of the Formation Flying Test Bed at GSFC, which provides a capability to interface with different GPS receivers and to produce real-time, filtered orbit solutions even when less than four satellites are visible. The result is a powerful tool for assessing onboard navigation performance in a wide range of orbital regimes, and a test-bed for developing software and procedures for use in real spacecraft applications.

Tidal deformation, Orbital Dynamics and JIMO

NASA Astrophysics Data System (ADS)

Ratcliff, J. T.; Wu, X.; Williams, J. G.

2003-12-01

Observations of Europa, Ganymede and Callisto obtained from encounters by the Galileo spacecraft strongly suggest the possibility of liquid oceans under the icy shells of these Jovian satellites. The strong tidal environments in which these moons are found and the fact that a planetary body with internal fluid undergoes greater deformation than an otherwise solid body make a compelling case for using tidal observations as a method for ocean detection. Given the high degree of uncertainty in our knowledge of the interiors of these moons, a comprehensive geodetic program measuring different physical signatures related to tidal deformation and interior structure is preferred to using separate and various interior parameters that may not be as closely tied to actual measurable quantities. Potential and displacement tidal Love numbers, libration amplitudes of the surface ice shell and rocky mantle, static topography and gravity fields and other quantities should all be included in the measurement objectives. Many geodetic techniques rely heavily upon orbital positions of the spacecraft. Their accurate determination depend on factors such as the orbital configuration, the gravity fields of the icy moons, as well as the duration and geometry of tracking. Given the competing science, engineering and planetary protection demands, orbital accuracy subject to constraints has become a critical mission design issue. Orbit determination simulations and covariance analyses will be used to investigate the achievable accuracies of spacecraft position and geodetic signatures under different orbital and tracking scenarios.

Preliminary Orbit Determination System (PODS) for Tracking and Data Relay Satellite System (TDRSS)-tracked target Spacecraft using the homotopy continuation method

NASA Technical Reports Server (NTRS)

Kirschner, S. M.; Samii, M. V.; Broaddus, S. R.; Doll, C. E.

1988-01-01

The Preliminary Orbit Determination System (PODS) provides early orbit determination capability in the Trajectory Computation and Orbital Products System (TCOPS) for a Tracking and Data Relay Satellite System (TDRSS)-tracked spacecraft. PODS computes a set of orbit states from an a priori estimate and six tracking measurements, consisting of any combination of TDRSS range and Doppler tracking measurements. PODS uses the homotopy continuation method to solve a set of nonlinear equations, and it is particularly effective for the case when the a priori estimate is not well known. Since range and Doppler measurements produce multiple states in PODS, a screening technique selects the desired state. PODS is executed in the TCOPS environment and can directly access all operational data sets. At the completion of the preliminary orbit determination, the PODS-generated state, along with additional tracking measurements, can be directly input to the differential correction (DC) process to generate an improved state. To validate the computational and operational capabilities of PODS, tests were performed using simulated TDRSS tracking measurements for the Cosmic Background Explorer (COBE) satellite and using real TDRSS measurements for the Earth Radiation Budget Satellite (ERBS) and the Solar Mesosphere Explorer (SME) spacecraft. The effects of various measurement combinations, varying arc lengths, and levels of degradation of the a priori state vector on the PODS solutions were considered.

Fuzzy attitude control for a nanosatellite in leo orbit

NASA Astrophysics Data System (ADS)

Calvo, Daniel; Laverón-Simavilla, Ana; Lapuerta, Victoria; Aviles, Taisir

Fuzzy logic controllers are flexible and simple, suitable for small satellites Attitude Determination and Control Subsystems (ADCS). In this work, a tailored fuzzy controller is designed for a nanosatellite and is compared with a traditional Proportional Integrative Derivative (PID) controller. Both control methodologies are compared within the same specific mission. The orbit height varies along the mission from injection at around 380 km down to a 200 km height orbit, and the mission requires pointing accuracy over the whole time. Due to both the requirements imposed by such a low orbit, and the limitations in the power available for the attitude control, a robust and efficient ADCS is required. For these reasons a fuzzy logic controller is implemented as the brain of the ADCS and its performance and efficiency are compared to a traditional PID. The fuzzy controller is designed in three separated controllers, each one acting on one of the Euler angles of the satellite in an orbital frame. The fuzzy memberships are constructed taking into account the mission requirements, the physical properties of the satellite and the expected performances. Both methodologies, fuzzy and PID, are fine-tuned using an automated procedure to grant maximum efficiency with fixed performances. Finally both methods are probed in different environments to test their characteristics. The simulations show that the fuzzy controller is much more efficient (up to 65% less power required) in single maneuvers, achieving similar, or even better, precision than the PID. The accuracy and efficiency improvement of the fuzzy controller increase with orbit height because the environmental disturbances decrease, approaching the ideal scenario. A brief mission description is depicted as well as the design process of both ADCS controllers. Finally the validation process and the results obtained during the simulations are described. Those results show that the fuzzy logic methodology is valid for small satellites' missions benefiting from a well-developed artificial intelligence theory.

Interaction of hydraulic and buckling mechanisms in blowout fractures.

PubMed

Nagasao, Tomohisa; Miyamoto, Junpei; Jiang, Hua; Tamaki, Tamotsu; Kaneko, Tsuyoshi

2010-04-01

The etiology of blowout fractures is generally attributed to 2 mechanisms--increase in the pressure of the orbital contents (the hydraulic mechanism) and direct transmission of impacts on the orbital walls (the buckling mechanism). The present study aims to elucidate whether or not an interaction exists between these 2 mechanisms. We performed a simulation experiment using 10 Computer-Aided-Design skull models. We applied destructive energy to the orbits of the 10 models in 3 different ways. First, to simulate pure hydraulic mechanism, energy was applied solely on the internal walls of the orbit. Second, to simulate pure buckling mechanism, energy was applied solely on the inferior rim of the orbit. Third, to simulate the combined effect of the hydraulic and buckling mechanisms, energy was applied both on the internal wall of the orbit and inferior rim of the orbit. After applying the energy, we calculated the areas of the regions where fracture occurred in the models. Thereafter, we compared the areas among the 3 energy application patterns. When the hydraulic and buckling mechanisms work simultaneously, fracture occurs on wider areas of the orbital walls than when each of these mechanisms works separately. The hydraulic and buckling mechanisms interact, enhancing each other's effect. This information should be taken into consideration when we examine patients in whom blowout fracture is suspected.

Aerocapture Performance Analysis of A Venus Exploration Mission

NASA Technical Reports Server (NTRS)

Starr, Brett R.; Westhelle, Carlos H.

2005-01-01

A performance analysis of a Discovery Class Venus Exploration Mission in which aerocapture is used to capture a spacecraft into a 300km polar orbit for a two year science mission has been conducted to quantify its performance. A preliminary performance assessment determined that a high heritage 70 sphere-cone rigid aeroshell with a 0.25 lift to drag ratio has adequate control authority to provide an entry flight path angle corridor large enough for the mission s aerocapture maneuver. A 114 kilograms per square meter ballistic coefficient reference vehicle was developed from the science requirements and the preliminary assessment s heating indicators and deceleration loads. Performance analyses were conducted for the reference vehicle and for sensitivity studies on vehicle ballistic coefficient and maximum bank rate. The performance analyses used a high fidelity flight simulation within a Monte Carlo executive to define the aerocapture heating environment and deceleration loads and to determine mission success statistics. The simulation utilized the Program to Optimize Simulated Trajectories (POST) that was modified to include Venus specific atmospheric and planet models, aerodynamic characteristics, and interplanetary trajectory models. In addition to Venus specific models, an autonomous guidance system, HYPAS, and a pseudo flight controller were incorporated in the simulation. The Monte Carlo analyses incorporated a reference set of approach trajectory delivery errors, aerodynamic uncertainties, and atmospheric density variations. The reference performance analysis determined the reference vehicle achieves 100% successful capture and has a 99.87% probability of attaining the science orbit with a 90 meters per second delta V budget for post aerocapture orbital adjustments. A ballistic coefficient trade study conducted with reference uncertainties determined that the 0.25 L/D vehicle can achieve 100% successful capture with a ballistic coefficient of 228 kilograms per square meter and that the increased ballistic coefficient increases post aerocapture V budget to 134 meters per second for a 99.87% probability of attaining the science orbit. A trade study on vehicle bank rate determined that the 0.25 L/D vehicle can achieve 100% successful capture when the maximum bank rate is decreased from 30 deg/s to 20 deg/s. The decreased bank rate increases post aerocapture delta V budget to 102 meters per second for a 99.87% probability of attaining the science orbit.

Thermal math model analysis of FRSI test article subjected to cold soak and entry environments. [Flexible Reuseable Surface Insulation in Space Shuttle Orbiter

NASA Technical Reports Server (NTRS)

Gallegos, J. J.

1978-01-01

A multi-objective test program was conducted at the NASA/JSC Radiant Heat Test Facility in which an aluminum skin/stringer test panel insulated with FRSI (Flexible Reusable Surface Insulation) was subjected to 24 simulated Space Shuttle Orbiter ascent/entry heating cycles with a cold soak in between in the 10th and 20th cycles. A two-dimensional thermal math model was developed and utilized to predict the thermal performance of the FRSI. Results are presented which indicate that the modeling techniques and property values have been proven adequate in predicting peak structure temperatures and entry thermal responses from both an ambient and cold soak condition of an FRSI covered aluminum structure.

Pest control through viral disease: mathematical modeling and analysis.

PubMed

Bhattacharyya, S; Bhattacharya, D K

2006-01-07

This paper deals with the mathematical modeling of pest management under viral infection (i.e. using viral pesticide) and analysis of its essential mathematical features. As the viral infection induces host lysis which releases more virus into the environment, on the average 'kappa' viruses per host, kappain(1,infinity), the 'virus replication parameter' is chosen as the main parameter on which the dynamics of the infection depends. We prove that there exists a threshold value kappa(0) beyond which the endemic equilibrium bifurcates from the free disease one. Still for increasing kappa values, the endemic equilibrium bifurcates towards a periodic solution. We further analyse the orbital stability of the periodic orbits arising from bifurcation by applying Poor's condition. A concluding discussion with numerical simulation of the model is then presented.

Electron-correlated fragment-molecular-orbital calculations for biomolecular and nano systems.

PubMed

Tanaka, Shigenori; Mochizuki, Yuji; Komeiji, Yuto; Okiyama, Yoshio; Fukuzawa, Kaori

2014-06-14

Recent developments in the fragment molecular orbital (FMO) method for theoretical formulation, implementation, and application to nano and biomolecular systems are reviewed. The FMO method has enabled ab initio quantum-mechanical calculations for large molecular systems such as protein-ligand complexes at a reasonable computational cost in a parallelized way. There have been a wealth of application outcomes from the FMO method in the fields of biochemistry, medicinal chemistry and nanotechnology, in which the electron correlation effects play vital roles. With the aid of the advances in high-performance computing, the FMO method promises larger, faster, and more accurate simulations of biomolecular and related systems, including the descriptions of dynamical behaviors in solvent environments. The current status and future prospects of the FMO scheme are addressed in these contexts.

The Threatening Magnetic and Plasma Environment of the TRAPPIST-1 Planets

NASA Astrophysics Data System (ADS)

Garraffo, Cecilia; Drake, Jeremy J.; Cohen, Ofer; Alvarado-Gómez, Julian D.; Moschou, Sofia P.

2017-07-01

Recently, four additional Earth-mass planets were discovered orbiting the nearby ultracool M8 dwarf, TRAPPIST-1, making a remarkable total of seven planets with equilibrium temperatures compatible with the presence of liquid water on their surface. Temperate terrestrial planets around an M-dwarf orbit close to their parent star, rendering their atmospheres vulnerable to erosion by the stellar wind and energetic electromagnetic and particle radiation. Here, we use state-of-the-art 3D magnetohydrodynamic models to simulate the wind around TRAPPIST-1 and study the conditions at each planetary orbit. All planets experience a stellar wind pressure between 103 and 105 times the solar wind pressure on Earth. All orbits pass through wind pressure changes of an order of magnitude and most planets spend a large fraction of their orbital period in the sub-Alfvénic regime. For plausible planetary magnetic field strengths, all magnetospheres are greatly compressed and undergo much more dynamic change than that of the Earth. The planetary magnetic fields connect with the stellar radial field over much of the planetary surface, allowing the direct flow of stellar wind particles onto the planetary atmosphere. These conditions could result in strong atmospheric stripping and evaporation and should be taken into account for any realistic assessment of the evolution and habitability of the TRAPPIST-1 planets.

Survival of spores of the UV-resistant Bacillus subtilis strain MW01 after exposure to low-earth orbit and simulated martian conditions: data from the space experiment ADAPT on EXPOSE-E.

PubMed

Wassmann, Marko; Moeller, Ralf; Rabbow, Elke; Panitz, Corinna; Horneck, Gerda; Reitz, Günther; Douki, Thierry; Cadet, Jean; Stan-Lotter, Helga; Cockell, Charles S; Rettberg, Petra

2012-05-01

In the space experiment "Molecular adaptation strategies of microorganisms to different space and planetary UV climate conditions" (ADAPT), bacterial endospores of the highly UV-resistant Bacillus subtilis strain MW01 were exposed to low-Earth orbit (LEO) and simulated martian surface conditions for 559 days on board the European Space Agency's exposure facility EXPOSE-E, mounted outside the International Space Station. The survival of B. subtilis MW01 spores from both assays (LEO and simulated martian conditions) was determined by a colony-formation assay after retrieval. It was clearly shown that solar extraterrestrial UV radiation (λ≥110 nm) as well as the martian UV spectrum (λ≥200 nm) was the most deleterious factor applied; in some samples only a few spore survivors were recovered from B. subtilis MW01 spores exposed in monolayers. However, if shielded from solar irradiation, about 8% of MW01 spores survived in LEO conditions, and 100% survived in simulated martian conditions, compared to the laboratory controls. The results demonstrate the effect of shielding against the high inactivation potential of extraterrestrial solar UV radiation, which limits the chances of survival of even the highly UV-resistant strain of B. subtilis MW01 in the harsh environments of outer space and the martian surface.

Extracting More Information from Passive Optical Tracking Observations for Reliable Orbit Element Generation

NASA Astrophysics Data System (ADS)

Bennett, J.; Gehly, S.

2016-09-01

This paper presents results from a preliminary method for extracting more orbital information from low rate passive optical tracking data. An improvement in the accuracy of the observation data yields more accurate and reliable orbital elements. A comparison between the orbit propagations from the orbital element generated using the new data processing method is compared with the one generated from the raw observation data for several objects. Optical tracking data collected by EOS Space Systems, located on Mount Stromlo, Australia, is fitted to provide a new orbital element. The element accuracy is determined from a comparison between the predicted orbit and subsequent tracking data or reference orbit if available. The new method is shown to result in a better orbit prediction which has important implications in conjunction assessments and the Space Environment Research Centre space object catalogue. The focus is on obtaining reliable orbital solutions from sparse data. This work forms part of the collaborative effort of the Space Environment Management Cooperative Research Centre which is developing new technologies and strategies to preserve the space environment (www.serc.org.au).

Direct Simulation Monte Carlo Calculations in Support of the Columbia Shuttle Orbiter Accident Investigation

NASA Technical Reports Server (NTRS)

Gallis, Michael A.; LeBeau, Gerald J.; Boyles, Katie A.

2003-01-01

The Direct Simulation Monte Carlo method was used to provide 3-D simulations of the early entry phase of the Shuttle Orbiter. Undamaged and damaged scenarios were modeled to provide calibration points for engineering "bridging function" type of analysis. Currently the simulation technology (software and hardware) are mature enough to allow realistic simulations of three dimensional vehicles.

High Speed PC Based Data Acquisition and Instrumentation for Measurement of Simulated Low Earth Orbit Thermally Induced Disturbances

NASA Technical Reports Server (NTRS)

Sills, Joel W., Jr.; Griffin, Thomas J. (Technical Monitor)

2001-01-01

The Hubble Space Telescope (HST) Disturbance Verification Test (DVT) was conducted to characterize responses of the Observatory's new set of rigid solar array's (SA3) to thermally induced 'creak' or stiction releases. The data acquired in the DVT were used in verification of the HST Pointing Control System on-orbit performance, post-Servicing Mission 3B (SM3B). The test simulated the on-orbit environment on a deployed SA3 flight wing. Instrumentation for this test required pretest simulations in order to select the correct sensitivities. Vacuum compatible, highly accurate accelerometers and force gages were used for this test. The complexity of the test, as well as a short planning schedule, required a data acquisition system that was easy to configure, highly flexible, and extremely robust. A PC Windows oriented data acquisition system meets these requirements, allowing the test engineers to minimize the time required to plan and perform complex environmental test. The SA3 DVT provided a direct practical and complex demonstration of the versatility that PC based data acquisition systems provide. Two PC based data acquisition systems were assembled to acquire, process, distribute, and provide real time processing for several types of transducers used in the SA3 DVT. A high sample rate digital tape recorder was used to archive the sensor signals. The two systems provided multi-channel hardware and software architecture and were selected based on the test requirements. How these systems acquire and processes multiple data rates from different transducer types is discussed, along with the system hardware and software architecture.

Dynamical Sequestration of the Moon-Forming Impactor in Co-Orbital Resonance with Earth

NASA Astrophysics Data System (ADS)

Kortenkamp, Stephen J.; Hartmann, William J.

2015-11-01

Recent concerns about the giant impact hypothesis for the origin of the moon, and an associated “isotope crisis” are assuaged if the impactor was a local object that formed near Earth and the impact occurred relatively late. We investigated a scenario that may meet these criteria, with the moon-forming impactor originating in 1:1 co-orbital resonance with Earth. Using N-body numerical simulations we explored the dynamical consequences of placing Mars-mass companions in various co-orbital configurations with a proto-Earth having 90% of its current mass. We modeled configurations that include the four terrestrial planets as well as configurations that also include the four giant planets. In both the 4- and 8-planet models we found that a single additional Mars-mass companion typically remains a stable co-orbital of Earth for the entire 250 million year (Myr) duration of our simulations (33 of 34 simulations). In an effort to destabilize such a system we carried out an additional 45 simulations that included a second Mars-mass co-orbital companion. Even with two Mars-mass companions sharing Earth’s orbit most of these models (28) also remained stable for the entire 250 Myr duration of the simulations. Of the 17 two-companion models that eventually became unstable 12 impacts were observed between Earth and an escaping co-orbital companion. The average delay we observed for an impact of a Mars-mass companion with Earth was 101 Myr, and the longest delay was 221 Myr. Several of the stable simulations involved unusual 3-planet co-orbital configurations that could exhibit interesting observational signatures in plantetary transit surveys.

Pre-processing and post-processing in group-cluster mergers

NASA Astrophysics Data System (ADS)

Vijayaraghavan, R.; Ricker, P. M.

2013-11-01

Galaxies in clusters are more likely to be of early type and to have lower star formation rates than galaxies in the field. Recent observations and simulations suggest that cluster galaxies may be `pre-processed' by group or filament environments and that galaxies that fall into a cluster as part of a larger group can stay coherent within the cluster for up to one orbital period (`post-processing'). We investigate these ideas by means of a cosmological N-body simulation and idealized N-body plus hydrodynamics simulations of a group-cluster merger. We find that group environments can contribute significantly to galaxy pre-processing by means of enhanced galaxy-galaxy merger rates, removal of galaxies' hot halo gas by ram pressure stripping and tidal truncation of their galaxies. Tidal distortion of the group during infall does not contribute to pre-processing. Post-processing is also shown to be effective: galaxy-galaxy collisions are enhanced during a group's pericentric passage within a cluster, the merger shock enhances the ram pressure on group and cluster galaxies and an increase in local density during the merger leads to greater galactic tidal truncation.

A Design Study of Onboard Navigation and Guidance During Aerocapture at Mars. M.S. Thesis

NASA Technical Reports Server (NTRS)

Fuhry, Douglas Paul

1988-01-01

The navigation and guidance of a high lift-to-drag ratio sample return vehicle during aerocapture at Mars are investigated. Emphasis is placed on integrated systems design, with guidance algorithm synthesis and analysis based on vehicle state and atmospheric density uncertainty estimates provided by the navigation system. The latter utilizes a Kalman filter for state vector estimation, with useful update information obtained through radar altimeter measurements and density altitude measurements based on IMU-measured drag acceleration. A three-phase guidance algorithm, featuring constant bank numeric predictor/corrector atmospheric capture and exit phases and an extended constant altitude cruise phase, is developed to provide controlled capture and depletion of orbital energy, orbital plane control, and exit apoapsis control. Integrated navigation and guidance systems performance are analyzed using a four degree-of-freedom computer simulation. The simulation environment includes an atmospheric density model with spatially correlated perturbations to provide realistic variations over the vehicle trajectory. Navigation filter initial conditions for the analysis are based on planetary approach optical navigation results. Results from a selection of test cases are presented to give insight into systems performance.

Evaluation of Low Earth Orbit Environmental Effects on International Space Station Thermal Control Materials

NASA Technical Reports Server (NTRS)

Dever, Joyce A.; Rutledge, Sharon K.; Hasegawa, Mark M.; Reed, Charles K.

1998-01-01

Samples of International Space Station (ISS) thermal control coatings were exposed to simulated low Earth orbit (LEO) environmental conditions to determine effects on optical properties. In one test, samples of the white paint coating Z-93P were coated with outgassed products from Tefzel(R) (ethylene tetrafluoroethylene copolymer) power cable insulation as-may occur on ISS. These samples were then exposed, along with an uncontaminated Z-93P witness sample, to vacuum ultraviolet (VUV) radiation to determine solar absorptance degradation. The Z-93P samples coated with Tefzel(R) outgassing products experienced greater increases in solar absorptance than witness samples not coated with Tefzel(R) outgassing products. In another test, samples of second surface silvered Teflon(R) FEP (fluorinated ethylene propylene), SiO. (where x=2)-coated silvered Teflon(R) FEP, and Z-93P witness samples were exposed to the combined environments of atomic oxygen and VLTV radiation to determine optical properties changes due to these simulated ISS environmental effects. This test verified the durability of these materials in the absence of contaminants.

Atomic Oxygen Exposure of Polyimide Foam for International Space Station Solar Array Wing Blanket Box

NASA Technical Reports Server (NTRS)

Finckenor, M. M.; Albyn, K. C.; Watts, E. W.

2006-01-01

Onorbit photos of the International Space Station (ISS) solar array blanket box foam pad assembly indicate degradation of the Kapton film covering the foam, leading to atomic oxygen (AO) exposure of the foam. The purpose of this test was to determine the magnitude of particulate generation caused by low-Earth orbital environment exposure of the foam and also by compression of the foam during solar array wing retraction. The polyimide foam used in the ISS solar array wing blanket box assembly is susceptible to significant AO erosion. The foam sample in this test lost one-third of its mass after exposure to the equivalent of 22 mo onorbit. Some particulate was generated by exposure to simulated orbital conditions and the simulated solar array retraction (compression test). However, onorbit, these particles would also be eroded by AO. The captured particles were generally <1 mm, and the particles shaken free of the sample had a maximum size of 4 mm. The foam sample maintained integrity after a compression load of 2.5 psi.

JSC Orbital Debris Website Description

NASA Technical Reports Server (NTRS)

Johnson, Nicholas L.

2006-01-01

Purpose: The website provides information about the NASA Orbital Debris Program Office at JSC, which is the lead NASA center for orbital debris research. It is recognized world-wide for its leadership in addressing orbital debris issues. The NASA Orbital Debris Program Office has taken the international lead in conducting measurements of the environment and in developing the technical consensus for adopting mitigation measures to protect users of the orbital environment. Work at the center continues with developing an improved understanding of the orbital debris environment and measures that can be taken to control its growth. Major Contents: Orbital Debris research is divided into the following five broad efforts. Each area of research contains specific information as follows: 1) Modeling - NASA scientists continue to develop and upgrade orbital debris models to describe and characterize the current and future debris environment. Evolutionary and engineering models are described in detail. Downloadable items include a document in PDF format and executable software. 2) Measurements - Measurements of near-Earth orbital debris are accomplished by conducting ground-based and space-based observations of the orbital debris environment. The data from these sources provide validation of the environment models and identify the presence of new sources. Radar, optical and surface examinations are described. External links to related topics are provided. 3) Protection - Orbital debris protection involves conducting hypervelocity impact measurements to assess the risk presented by orbital debris to operating spacecraft and developing new materials and new designs to provide better protection from the environment with less weight penalty. The data from this work provides the link between the environment defined by the models and the risk presented by that environment to operating spacecraft and provides recommendations on design and operations procedures to reduce the risk as required. These data also help in the analysis and interpretation of impact features on returned spacecraft surfaces. 4) Mitigation - Controlling the growth of the orbital debris population is a high priority for NASA, the United States, and the major space-faring nations of the world to preserve near-Earth space for future generations. Mitigation measures can take the form of curtailing or preventing the creation of new debris, designing satellites to withstand impacts by small debris, and implementing operational procedures ranging from utilizing orbital regimes with less debris, adopting specific spacecraft attitudes, and even maneuvering to avoid collisions with debris. Downloadable items include several documents in PDF format and executable software.and 5) Reentry - Because of the increasing number of objects in space, NASA has adopted guidelines and assessment procedures to reduce the number of non-operational spacecraft and spent rocket upper stages orbiting the Earth. One method of postmission disposal is to allow reentry of these spacecraft, either from orbital decay (uncontrolled entry) or with a controlled entry. Orbital decay may be achieved by firing engines to lower the perigee altitude so that atmospheric drag will eventually cause the spacecraft to enter. However, the surviving debris impact footprint cannot be guaranteed to avoid inhabited landmasses. Controlled entry normally occurs by using a larger amount of propellant with a larger propulsion system to drive the spacecraft to enter the atmosphere at a steeper flight path angle. It will then enter at a more precise latitude, longitude, and footprint in a nearly uninhabited impact region, generally located in the ocean.

The Los Alamos dynamic radiation environment assimilation model (DREAM) for space weather specification and forecasting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reeves, Geoffrey D; Friedel, Reiner H W; Chen, Yue

2008-01-01

The Dynamic Radiation Environment Assimilation Model (DREAM) was developed at Los Alamos National Laboratory to assess, quantify, and predict the hazards from the natural space environment and the anthropogenic environment produced by high altitude nuclear explosions (HANE). DREAM was initially developed as a basic research activity to understand and predict the dynamics of the Earth's Van Allen radiation belts. It uses Kalman filter techniques to assimilate data from space environment instruments with a physics-based model of the radiation belts. DREAM can assimilate data from a variety of types of instruments and data with various levels of resolution and fidelity bymore » assigning appropriate uncertainties to the observations. Data from any spacecraft orbit can be assimilated but DREAM was designed to function with as few as two spacecraft inputs: one from geosynchronous orbit and one from GPS orbit. With those inputs, DREAM can be used to predict the environment at any satellite in any orbit whether space environment data are available in those orbits or not. Even with very limited data input and relatively simple physics models, DREAM specifies the space environment in the radiation belts to a high level of accuracy. DREAM has been extensively tested and evaluated as we transition from research to operations. We report here on one set of test results in which we predict the environment in a highly-elliptical polar orbit. We also discuss long-duration reanalysis for spacecraft design, using DREAM for real-time operations, and prospects for 1-week forecasts of the radiation belt environment.« less

Space Transfer Concepts and Analyses for Exploration Missions. Technical Directive 12: Beamed Power Systems Study

NASA Technical Reports Server (NTRS)

Eder, D.

1992-01-01

Parametric models were constructed for Earth-based laser powered electric orbit transfer from low Earth orbit to geosynchronous orbit. These models were used to carry out performance, cost/benefit, and sensitivity analyses of laser-powered transfer systems including end-to-end life cycle cost analyses for complete systems. Comparisons with conventional orbit transfer systems were made indicating large potential cost savings for laser-powered transfer. Approximate optimization was done to determine best parameter values for the systems. Orbit transfer flights simulations were conducted to explore effects of parameters not practical to model with a spreadsheet. The simulations considered view factors that determine when power can be transferred from ground stations to an orbit transfer vehicle and conducted sensitivity analyses for numbers of ground stations, Isp including dual-Isp transfers, and plane change profiles. Optimal steering laws were used for simultaneous altitude and plane change. Viewing geometry and low-thrust orbit raising were simultaneously simulated. A very preliminary investigation of relay mirrors was made.

Simulation and analyses of the aeroassist flight experiment attitude update method

NASA Technical Reports Server (NTRS)

Carpenter, J. R.

1991-01-01

A method which will be used to update the alignment of the Aeroassist Flight Experiment's Inertial Measuring Unit is simulated and analyzed. This method, the Star Line Maneuver, uses measurements from the Space Shuttle Orbiter star trackers along with an extended Kalman filter to estimate a correction to the attitude quaternion maintained by an Inertial Measuring Unit in the Orbiter's payload bay. This quaternion is corrupted by on-orbit bending of the Orbiter payload bay with respect to the Orbiter navigation base, which is incorporated into the payload quaternion when it is initialized via a direct transfer of the Orbiter attitude state. The method of updating this quaternion is examined through verification of baseline cases and Monte Carlo analysis using a simplified simulation, The simulation uses nominal state dynamics and measurement models from the Kalman filter as its real world models, and is programmed on Microvax minicomputer using Matlab, and interactive matrix analysis tool. Results are presented which confirm and augment previous performance studies, thereby enhancing confidence in the Star Line Maneuver design methodology.

Formation Algorithms and Simulation Testbed

NASA Technical Reports Server (NTRS)

Wette, Matthew; Sohl, Garett; Scharf, Daniel; Benowitz, Edward

2004-01-01

Formation flying for spacecraft is a rapidly developing field that will enable a new era of space science. For one of its missions, the Terrestrial Planet Finder (TPF) project has selected a formation flying interferometer design to detect earth-like planets orbiting distant stars. In order to advance technology needed for the TPF formation flying interferometer, the TPF project has been developing a distributed real-time testbed to demonstrate end-to-end operation of formation flying with TPF-like functionality and precision. This is the Formation Algorithms and Simulation Testbed (FAST) . This FAST was conceived to bring out issues in timing, data fusion, inter-spacecraft communication, inter-spacecraft sensing and system-wide formation robustness. In this paper we describe the FAST and show results from a two-spacecraft formation scenario. The two-spacecraft simulation is the first time that precision end-to-end formation flying operation has been demonstrated in a distributed real-time simulation environment.

KENNEDY SPACE CENTER, FLA. - Emergency crew members assess medical needs on “injured” astronauts removed from the orbiter crew compartment mock-up during a “Mode VII” emergency landing simulation at Kennedy Space Center. The purpose of the Mode VII is to exercise emergency preparedness personnel, equipment and facilities in rescuing astronauts from a downed orbiter and providing immediate medical attention. This simulation presents an orbiter that has crashed short of the Shuttle Landing Facility in a wooded area 2-1/2 miles south of Runway 33. Emergency crews are responding to the volunteer astronauts who are simulating various injuries. Rescuers must remove the crew, provide triage and transport to hospitals those who need further treatment. Local hospitals are participating in the exercise.

NASA Image and Video Library

2004-02-18

KENNEDY SPACE CENTER, FLA. - Emergency crew members assess medical needs on “injured” astronauts removed from the orbiter crew compartment mock-up during a “Mode VII” emergency landing simulation at Kennedy Space Center. The purpose of the Mode VII is to exercise emergency preparedness personnel, equipment and facilities in rescuing astronauts from a downed orbiter and providing immediate medical attention. This simulation presents an orbiter that has crashed short of the Shuttle Landing Facility in a wooded area 2-1/2 miles south of Runway 33. Emergency crews are responding to the volunteer astronauts who are simulating various injuries. Rescuers must remove the crew, provide triage and transport to hospitals those who need further treatment. Local hospitals are participating in the exercise.

Protective coatings for composite tubes in space applications

NASA Technical Reports Server (NTRS)

Dursch, Harry W.; Hendricks, Carl L.

1987-01-01

Protective coatings for graphite/epoxy (Gr/Ep) tubular structures for a manned Space Station truss structure were evaluated. The success of the composite tube truss structure depends on its stability to long-term exposure to the low earth orbit (LEO) environment, with particular emphasis placed on atomic oxygen. Concepts for protectively coating Gr/Ep tubes include use of inorganic coated metal foils and electroplating. These coatings were applied to Gr/Ep tubes and then subjected to simulated LEO environment to evaluate survivability of coatings and coated tubes. Evaluation included: atomic oxygen resistance, changes in optical properties and adhesion, abrasion resistance, surface preparation required, coating uniformity, and formation of microcracks in the Gr/Ep tubes caused by thermal cycling. Program results demonstrated that both phosphoric and chromic acid anodized Al foil provided excellent adhesion to Gr/Ep tubes and exhibited stable optical properties when subjected to simulated LEO environment. The SiO2/Al coatings sputtered onto Al foils also resulted in an excellent protective coating. Electroplated Ni exhibited unacceptable adhesion loss to Gr/Ep tubes during atomic oxygen exposure.

Application of EVA guidelines and design criteria. Volume 1: EVA selection/systems design considerations

NASA Technical Reports Server (NTRS)

Brown, N. E.

1973-01-01

Parameters that require consideration by the planners and designers when planning for man to perform functions outside the vehicle are presented in terms of the impact the extravehicular crewmen and major EV equipment items have on the mission, vehicle, and payload. Summary data on man's performance capabilities in the weightless space environment are also provided. The performance data are based on orbital and transearth EVA from previous space flight programs and earthbound simulations, such as water immersion and zero-g aircraft.

2001 Flight Mechanics Symposium

NASA Technical Reports Server (NTRS)

Lynch, John P. (Editor)

2001-01-01

This conference publication includes papers and abstracts presented at the Flight Mechanics Symposium held on June 19-21, 2001. Sponsored by the Guidance, Navigation and Control Center of Goddard Space Flight Center, this symposium featured technical papers on a wide range of issues related to attitude/orbit determination, prediction and control; attitude simulation; attitude sensor calibration; theoretical foundation of attitude computation; dynamics model improvements; autonomous navigation; constellation design and formation flying; estimation theory and computational techniques; Earth environment mission analysis and design; and, spacecraft re-entry mission design and operations.

STS-42 crewmembers in LESs prepare for egress exercises in JSC's WETF Bldg 29

NASA Technical Reports Server (NTRS)

1991-01-01

STS-42 Discovery, Orbiter Vehicle (OV) 103, crewmembers, (left to right) Commander Ronald J. Grabe, Payload Specialist Roberta L. Bondar, and Pilot Stephen S. Oswald, participate in launch emergency egress (bailout) exercises in JSC's Weightless Environment Training Facility (WETF) Bldg 29. The crewmembers are outfitted in their launch and entry suits (LESs) and launch and entry helmets (LEHs) as they prepare for the simulated water landing using the WETF's 25 ft deep pool as the ocean.

STS-52 Pilot Baker, in LES/LEH, during JSC WETF bailout exercises

NASA Technical Reports Server (NTRS)

1992-01-01

STS-52 Columbia, Orbiter Vehicle (OV) 102, Pilot Michael A. Baker smiles from under his launch and entry helmet (LEH) and from behind the communications carrier assembly (CCA) microphones as he adjusts his parachute harness. Baker, fully outfitted in a launch and entry suit (LES), prepares for emergency egress (bailout) training exercise in JSC's Weightless Environment Training Facility (WETF) Bldg 29 pool. The WETF's 25-ft deep pool will be used in this simulation of a water landing.

STS-45 MS Foale dons EMU with technicians' help in JSC's WETF Bldg 29

NASA Technical Reports Server (NTRS)

1991-01-01

STS-45 Atlantis, Orbiter Vehicle (OV) 104, Mission Specialist (MS) C. Michael Foale stands on a platform as technicians help him don his extravehicular mobility unit (EMU). The technicians are preparing to connect the EMU upper and lower torsos at the waist ring. When fully suited, Foale will be lowered into a nearby 25 ft deep pool for an underwater simulation of contingency extravehicular activity (EVA) procedures. The pool is located in JSC's Weightless Environment Training Facility (WETF) Bldg 29.

STS-26 MS Hilmers floats in life raft during JSC WETF exercises

NASA Technical Reports Server (NTRS)

1988-01-01

STS-26 Discovery, Orbiter Vehicle (OV) 103, Mission Specialist (MS) David C. Hilmers, wearing the newly designed launch and entry suit (LES), floats in single-occupant life raft in JSC Weightless Environment Training Facility (WETF) Bldg 29 pool. Hilmers pulls his legs into the inflating raft while he is assisted by two SCUBA-equipped divers. The simulation of the escape and rescue operations utilized the crew escape system (CES) pole method of egress from the Space Shuttle.

STS-26 Commander Hauck floats in life raft during JSC WETF exercises

NASA Technical Reports Server (NTRS)

1988-01-01

STS-26 Discovery, Orbiter Vehicle (OV) 103, Commander Frederick H. Hauck, wearing the newly designed launch and entry suit (LES), floats in single-occupant life raft in JSC Weightless Environment Training Facility (WETF) Bldg 29 pool. Removing water from his raft, Hauck awaits the assistance of SCUBA-equipped divers (one of whom is partially visible at bottom right). The simulation of the escape and rescue operations utilized the crew escape system (CES) pole method of egress from the Space Shuttle.

Influence of Atomic Oxygen Exposure on Friction Behavior of 321 Stainless Steel

NASA Astrophysics Data System (ADS)

Liu, Y.; Yang, J.; Ye, Z.; Dong, S.; Zhang, L.; Zhang, Z.

Atomic oxygen (AO) exposure testing has been conducted on a 321 stainless steel rolled 1 mm thick sheet to simulate the effect of AO environment on steel in low Earth orbit (LEO). An atomic oxygen exposure facility was employed to carry out AO experiments with the fluence up to ~1021 atom/cm2. The AO exposed specimens were evaluated in air at room temperature using a nanoindenter and a tribological system. The exposed surfaces were analyzed usign XPS technique.

2-kW Solar Dynamic Space Power System Tested in Lewis' Thermal Vacuum Facility

NASA Technical Reports Server (NTRS)

1995-01-01

Working together, a NASA/industry team successfully operated and tested a complete solar dynamic space power system in a large thermal vacuum facility with a simulated sun. This NASA Lewis Research Center facility, known as Tank 6 in building 301, accurately simulates the temperatures, high vacuum, and solar flux encountered in low-Earth orbit. The solar dynamic space power system shown in the photo in the Lewis facility, includes the solar concentrator and the solar receiver with thermal energy storage integrated with the power conversion unit. Initial testing in December 1994 resulted in the world's first operation of an integrated solar dynamic system in a relevant environment.

Characterization and modeling of radiation effects NASA/MSFC semiconductor devices

NASA Technical Reports Server (NTRS)

Kerns, D. V., Jr.; Cook, K. B., Jr.

1978-01-01

A literature review of the near-Earth trapped radiation of the Van Allen Belts, the radiation within the solar system resulting from the solar wind, and the cosmic radiation levels of deep space showed that a reasonable simulation of space radiation, particularly the Earth orbital environment, could be simulated in the laboratory by proton bombardment. A 3 MeV proton accelerator was used to irradiate CMOS integrated circuits fabricated from three different processes. The drain current and output voltage for three inverters was recorded as the input voltage was swept from zero to ten volts after each successive irradiation. Device parameters were extracted. Possible damage mechanisms are discussed and recommendations for improved radiation hardness are suggested.

A channel simulator design study

NASA Technical Reports Server (NTRS)

Devito, D. M.; Goutmann, M. M.; Harper, R. C.

1971-01-01

A propagation path simulator was designed for the channel between a Tracking and Data Relay Satellite in geostationary orbit and a user spacecraft orbiting the earth at an altitude between 200 and 4000 kilometers. The simulator is required to duplicate the time varying parameters of the propagation channel.

Using parallel computing for the display and simulation of the space debris environment

NASA Astrophysics Data System (ADS)

Möckel, M.; Wiedemann, C.; Flegel, S.; Gelhaus, J.; Vörsmann, P.; Klinkrad, H.; Krag, H.

2011-07-01

Parallelism is becoming the leading paradigm in today's computer architectures. In order to take full advantage of this development, new algorithms have to be specifically designed for parallel execution while many old ones have to be upgraded accordingly. One field in which parallel computing has been firmly established for many years is computer graphics. Calculating and displaying three-dimensional computer generated imagery in real time requires complex numerical operations to be performed at high speed on a large number of objects. Since most of these objects can be processed independently, parallel computing is applicable in this field. Modern graphics processing units (GPUs) have become capable of performing millions of matrix and vector operations per second on multiple objects simultaneously. As a side project, a software tool is currently being developed at the Institute of Aerospace Systems that provides an animated, three-dimensional visualization of both actual and simulated space debris objects. Due to the nature of these objects it is possible to process them individually and independently from each other. Therefore, an analytical orbit propagation algorithm has been implemented to run on a GPU. By taking advantage of all its processing power a huge performance increase, compared to its CPU-based counterpart, could be achieved. For several years efforts have been made to harness this computing power for applications other than computer graphics. Software tools for the simulation of space debris are among those that could profit from embracing parallelism. With recently emerged software development tools such as OpenCL it is possible to transfer the new algorithms used in the visualization outside the field of computer graphics and implement them, for example, into the space debris simulation environment. This way they can make use of parallel hardware such as GPUs and Multi-Core-CPUs for faster computation. In this paper the visualization software will be introduced, including a comparison between the serial and the parallel method of orbit propagation. Ways of how to use the benefits of the latter method for space debris simulation will be discussed. An introduction to OpenCL will be given as well as an exemplary algorithm from the field of space debris simulation.

Using parallel computing for the display and simulation of the space debris environment

NASA Astrophysics Data System (ADS)

Moeckel, Marek; Wiedemann, Carsten; Flegel, Sven Kevin; Gelhaus, Johannes; Klinkrad, Heiner; Krag, Holger; Voersmann, Peter

Parallelism is becoming the leading paradigm in today's computer architectures. In order to take full advantage of this development, new algorithms have to be specifically designed for parallel execution while many old ones have to be upgraded accordingly. One field in which parallel computing has been firmly established for many years is computer graphics. Calculating and displaying three-dimensional computer generated imagery in real time requires complex numerical operations to be performed at high speed on a large number of objects. Since most of these objects can be processed independently, parallel computing is applicable in this field. Modern graphics processing units (GPUs) have become capable of performing millions of matrix and vector operations per second on multiple objects simultaneously. As a side project, a software tool is currently being developed at the Institute of Aerospace Systems that provides an animated, three-dimensional visualization of both actual and simulated space debris objects. Due to the nature of these objects it is possible to process them individually and independently from each other. Therefore, an analytical orbit propagation algorithm has been implemented to run on a GPU. By taking advantage of all its processing power a huge performance increase, compared to its CPU-based counterpart, could be achieved. For several years efforts have been made to harness this computing power for applications other than computer graphics. Software tools for the simulation of space debris are among those that could profit from embracing parallelism. With recently emerged software development tools such as OpenCL it is possible to transfer the new algorithms used in the visualization outside the field of computer graphics and implement them, for example, into the space debris simulation environment. This way they can make use of parallel hardware such as GPUs and Multi-Core-CPUs for faster computation. In this paper the visualization software will be introduced, including a comparison between the serial and the parallel method of orbit propagation. Ways of how to use the benefits of the latter method for space debris simulation will be discussed. An introduction of OpenCL will be given as well as an exemplary algorithm from the field of space debris simulation.

Ground based ISS payload microgravity disturbance assessments.

PubMed

McNelis, Anne M; Heese, John A; Samorezov, Sergey; Moss, Larry A; Just, Marcus L

2005-01-01

In order to verify that the International Space Station (ISS) payload facility racks do not disturb the microgravity environment of neighboring facility racks and that the facility science operations are not compromised, a testing and analytical verification process must be followed. Currently no facility racks have taken this process from start to finish. The authors are participants in implementing this process for the NASA Glenn Research Center (GRC) Fluids and Combustion Facility (FCF). To address the testing part of the verification process, the Microgravity Emissions Laboratory (MEL) was developed at GRC. The MEL is a 6 degree of freedom inertial measurement system capable of characterizing inertial response forces (emissions) of components, sub-rack payloads, or rack-level payloads down to 10(-7) g's. The inertial force output data, generated from the steady state or transient operations of the test articles, are utilized in analytical simulations to predict the on-orbit vibratory environment at specific science or rack interface locations. Once the facility payload rack and disturbers are properly modeled an assessment can be made as to whether required microgravity levels are achieved. The modeling is utilized to develop microgravity predictions which lead to the development of microgravity sensitive ISS experiment operations once on-orbit. The on-orbit measurements will be verified by use of the NASA GRC Space Acceleration Measurement System (SAMS). The major topics to be addressed in this paper are: (1) Microgravity Requirements, (2) Microgravity Disturbers, (3) MEL Testing, (4) Disturbance Control, (5) Microgravity Control Process, and (6) On-Orbit Predictions and Verification. Published by Elsevier Ltd.

Standalone GPS L1 C/A Receiver for Lunar Missions.

PubMed

Capuano, Vincenzo; Blunt, Paul; Botteron, Cyril; Tian, Jia; Leclère, Jérôme; Wang, Yanguang; Basile, Francesco; Farine, Pierre-André

2016-03-09

Global Navigation Satellite Systems (GNSSs) were originally introduced to provide positioning and timing services for terrestrial Earth users. However, space users increasingly rely on GNSS for spacecraft navigation and other science applications at several different altitudes from the Earth surface, in Low Earth Orbit (LEO), Medium Earth Orbit (MEO), Geostationary Earth Orbit (GEO), and feasibility studies have proved that GNSS signals can even be tracked at Moon altitude. Despite this, space remains a challenging operational environment, particularly on the way from the Earth to the Moon, characterized by weaker signals with wider gain variability, larger dynamic ranges resulting in higher Doppler and Doppler rates and critically low satellite signal availability. Following our previous studies, this paper describes the proof of concept "WeakHEO" receiver; a GPS L1 C/A receiver we developed in our laboratory specifically for lunar missions. The paper also assesses the performance of the receiver in two representative portions of an Earth Moon Transfer Orbit (MTO). The receiver was connected to our GNSS Spirent simulator in order to collect real-time hardware-in-the-loop observations, and then processed by the navigation module. This demonstrates the feasibility, using current technology, of effectively exploiting GNSS signals for navigation in a MTO.

Analysis of orbital perturbations acting on objects in orbits near geosynchronous earth orbit

NASA Technical Reports Server (NTRS)

Friesen, Larry J.; Jackson, Albert A., IV; Zook, Herbert A.; Kessler, Donald J.

1992-01-01

The paper presents a numerical investigation of orbital evolution for objects started in GEO or in orbits near GEO in order to study potential orbital debris problems in this region. Perturbations simulated include nonspherical terms in the earth's geopotential field, lunar and solar gravity, and solar radiation pressure. Objects simulated include large satellites, for which solar radiation pressure is insignificant, and small particles, for which solar radiation pressure is an important force. Results for large satellites are largely in agreement with previous GEO studies that used classical perturbation techniques. The orbit plane of GEO satellites placed in a stable plane orbit inclined approximately 7.3 deg to the equator experience very little precession, remaining always within 1.2 percent of their initial orientation. Solar radiation pressure generates two major effects on small particles: an orbital eccentricity oscillation anticipated from previous research, and an oscillation in orbital inclination.

Dusty disc-planet interaction with dust-free simulations

NASA Astrophysics Data System (ADS)

Chen, Jhih-Wei; Lin, Min-Kai

2018-05-01

Protoplanets may be born into dust-rich environments if planetesimals formed through streaming or gravitational instabilities, or if the protoplanetary disc is undergoing mass loss due to disc winds or photoevaporation. Motivated by this possibility, we explore the interaction between low mass planets and dusty protoplanetary discs with focus on disc-planet torques. We implement Lin & Youdin's newly developed, purely hydrodynamic model of dusty gas into the PLUTO code to simulate dusty protoplanetary discs with an embedded planet. We find that for imperfectly coupled dust and high metallicity, e.g. Stokes number 10-3 and dust-to-gas ratio Σd/Σg = 0.5, a `bubble' develops inside the planet's co-orbital region, which introduces unsteadiness in the flow. The resulting disc-planet torques sustain large amplitude oscillations that persists well beyond that in simulations with perfectly coupled dust or low dust-loading, where co-rotation torques are always damped. We show that the desaturation of the co-rotation torques by finite-sized particles is related to potential vorticity generation from the misalignment of dust and gas densities. We briefly discuss possible implications for the orbital evolution of protoplanets in dust-rich discs. We also demonstrate Lin & Youdin's dust-free framework reproduces previous results pertaining to dusty protoplanetary discs, including dust-trapping by pressure bumps, dust settling, and the streaming instability.

The Turbulent Origin of Spin-Orbit Misalignment in Planetary Systems

DOE PAGES

Fielding, Drummond B.; McKee, Christopher F.; Socrates, Aristostle; ...

2015-05-13

The turbulent environment from which stars form may lead to misalignment between the stellar spin and the remnant protoplanetary disk. By using hydrodynamic and magnetohydrodynamic simulations, we demonstrate that a wide range of stellar obliquities may be produced as a by-product of forming a star within a turbulent environment. We present a simple semi-analytic model that reveals this connection between the turbulent motions and the orientation of a star and its disk. Our results are consistent with the observed obliquity distribution of hot Jupiters. Migration of misaligned hot Jupiters may, therefore, be due to tidal dissipation in the disk, rathermore » than tidal dissipation of the star-planet interaction.« less

Technology developments integrating a space network communications testbed

NASA Technical Reports Server (NTRS)

Kwong, Winston; Jennings, Esther; Clare, Loren; Leang, Dee

2006-01-01

As future manned and robotic space explorations missions involve more complex systems, it is essential to verify, validate, and optimize such systems through simulation and emulation in a low cost testbed environment. The goal of such a testbed is to perform detailed testing of advanced space and ground communications networks, technologies, and client applications that are essential for future space exploration missions. We describe the development of new technologies enhancing our Multi-mission Advanced Communications Hybrid Environment for Test and Evaluation (MACHETE) that enables its integration in a distributed space communications testbed. MACHETE combines orbital modeling, link analysis, and protocol and service modeling to quantify system performance based on comprehensive considerations of different aspects of space missions.

Ground-Based Testing of Replacement Thermal Control Materials for the Hubble Space Telescope

NASA Technical Reports Server (NTRS)

Townsend, Jacqueline A.; Hansen, Patricia A.; McClendon, Mark W.; deGroh, Kim K.; Banks, Bruce A.; Triolo, Jack J.

1998-01-01

The mechanical and optical properties of the metallized Teflon FEP thermal control materials on the Hubble Space Telescope (HST) have degraded over the nearly seven years the telescope has been in orbit. Given the damage to the outer layer of the multi-layer insulation (MLI) that was apparent during the second servicing mission (SM2), the decision was made to replace the outer layer during subsequent servicing missions. A Failure Review Board was established to investigate the damage to the MLI and identify a replacement material. The replacement material had to meet the stringent thermal requirements of the spacecraft and maintain mechanical integrity for at least ten years. Ten candidate materials were selected and exposed to ten-year HST-equivalent doses of simulated orbital environments. Samples of the candidates were exposed sequentially to low and high energy electrons and protons, atomic oxygen, x-ray radiation, ultraviolet radiation and thermal cycling. Following the exposures, the mechanical integrity and optical properties of the candidates were investigated using Optical Microscopy, Scanning Electron Microscopy (SEM), a Laboratory Portable Spectroreflectometer (LPSR) and a Lambda 9 Spectroreflectometer. Based on the results of these simulations and analyses, the Failure Review Board selected a replacement material and two alternates that showed the highest likelihood of providing the requisite thermal properties and surviving for ten years in orbit.

Stability of Moons in the Trappist-1 System

NASA Astrophysics Data System (ADS)

Allen, John; Becker, Christopher; Fuse, Christopher

2018-01-01

In the last 20 years, numerous exoplanets have been discovered and it has become clear that habitable bodies are rare. Exomoons mark the next stage in identifying habitable environs. In our own Solar system, several moons have been identified as having features suitable to sustain life. The Trappist-1 system (Gillon et al. 2017) is a compact configuration of seven Earth-like planets orbiting a M-type dwarf star. The presence of moons cannot be confirmed in the transit data. Kane et al. (2017) suggests that it would be highly improbable for a moon to maintain a stable orbit around any Trappist-1 planet. The current study investigates the claim by Kane et al. (2017), examining the stability of the Trappist-1 system in the presence of forming satellites. Moon disks are simulated by distributing 100 bodies, each with mass 5.26 x 1018 kg randomly within 10% - 90% of the exoplanet’s Hill sphere. Utilizing N-body simulations, the planets and theoretical moons were tracked for 500 kyrs, allowing for gravitational interactions and mergers. Instabilities in the orbital parameters of the Trappist-1 planets was detected, in agreement with previous authors (Burgasser & Mamajerk 2017). Some of the planets are found to retain at least a single satellite for the same duration as the planetary stability. These data suggest that additional observation of the Trappist-1 system may yield the first detection of an exomoon.

Data Acquisition, Management, and Analysis in Support of the Audiology and Hearing Conservation and the Orbital Debris Program Office

NASA Technical Reports Server (NTRS)

Dicken, Todd

2012-01-01

My internship at Johnson Space Center, Houston TX comprised of working simultaneously in the Space Life Science Directorate (Clinical Services Branch, SD3) in Audiology and Hearing Conservation and in the Astromaterials Research and Exploration Sciences Directorate in the Orbital Debris Program Office (KX). The purpose of the project done to support the Audiology and Hearing Conservation Clinic (AuHCon) is to organize and analyze auditory test data that has been obtained from tests conducted onboard the International Space Station (ISS) and in Johnson Space Center's clinic. Astronauts undergo a special type of auditory test called an On-Orbit Hearing Assessment (OOHA), which monitors hearing function while crewmembers are exposed to noise and microgravity during long-duration spaceflight. Data needed to be formatted to assist the Audiologist in studying, analyzing and reporting OOHA results from all ISS missions, with comparison to conventional preflight and post-flight audiometric test results of crewmembers. Orbital debris is the #1 threat to manned spacecraft; therefore NASA is investing in different measurement techniques to acquire information on orbital debris. These measurements are taken with telescopes in different parts of the world to acquire brightness variations over time, from which size, rotation rates and material information can be determined for orbital debris. Currently many assumptions are taken to resolve size and material from observed brightness, therefore a laboratory (Optical Measurement Center) is used to simulate the space environment and acquire information of known targets suited to best model the orbital debris population. In the Orbital Debris Program Office (ODPO) telescopic data were acquired and analyzed to better assess the orbital debris population.

Baryonic impact on the dark matter orbital properties of Milky Way-sized haloes

NASA Astrophysics Data System (ADS)

Zhu, Qirong; Hernquist, Lars; Marinacci, Federico; Springel, Volker; Li, Yuexing

2017-04-01

We study the orbital properties of dark matter haloes by combining a spectral method and cosmological simulations of Milky Way-sized Galaxies. We compare the dynamics and orbits of individual dark matter particles from both hydrodynamic and N-body simulations, and find that the fraction of box, tube and resonant orbits of the dark matter halo decreases significantly due to the effects of baryons. In particular, the central region of the dark matter halo in the hydrodynamic simulation is dominated by regular, short-axis tube orbits, in contrast to the chaotic, box and thin orbits dominant in the N-body run. This leads to a more spherical dark matter halo in the hydrodynamic run compared to a prolate one as commonly seen in the N-body simulations. Furthermore, by using a kernel-based density estimator, we compare the coarse-grained phase-space densities of dark matter haloes in both simulations and find that it is lower by ˜0.5 dex in the hydrodynamic run due to changes in the angular momentum distribution, which indicates that the baryonic process that affects the dark matter is irreversible. Our results imply that baryons play an important role in determining the shape, kinematics and phase-space density of dark matter haloes in galaxies.

Neutral Buoyancy Simulator: MSFC-Langley joint test of large space structures component assembly:

NASA Technical Reports Server (NTRS)

1978-01-01

Once the United States' space program had progressed from Earth's orbit into outerspace, the prospect of building and maintaining a permanent presence in space was realized. To accomplish this feat, NASA launched a temporary workstation, Skylab, to discover the effects of low gravity and weightlessness on the human body, and also to develop tools and equipment that would be needed in the future to build and maintain a more permanent space station. The structures, techniques, and work schedules had to be carefully designed to fit this unique construction site. The components had to be lightweight for transport into orbit, yet durable. The station also had to be made with removable parts for easy servicing and repairs by astronauts. All of the tools necessary for service and repairs had to be designed for easy manipulation by a suited astronaut. And construction methods had to be efficient due to limited time the astronauts could remain outside their controlled environment. In lieu of all the specific needs for this project, an environment on Earth had to be developed that could simulate a low gravity atmosphere. A Neutral Buoyancy Simulator (NBS) was constructed by NASA Marshall Space Flight Center (MSFC) in 1968. Since then, NASA scientists have used this facility to understand how humans work best in low gravity and also provide information about the different kinds of structures that can be built. Another facet of the space station would be electrical cornectors which would be used for powering tools the astronauts would need for construction, maintenance and repairs. Shown is an astronaut training during an underwater electrical connector test in the NBS.

Neutral Buoyancy Simulator-NB32-Assembly of Large Space Structure

NASA Technical Reports Server (NTRS)

1980-01-01

Once the United States' space program had progressed from Earth's orbit into outerspace, theprospect of building and maintaining a permanent presence in space was realized. To accomplish this feat, NASA launched a temporary workstation, Skylab, to discover the effects of low gravity and weightlessness on the human body, and also to develop tools and equipment that would be needed in the future to build and maintain a more permanent space station. The structures, techniques, and work schedules had to be carefully designed to fit this unique construction site. The components had to be lightweight for transport into orbit, yet durable. The station also had to be made with removable parts for easy servicing and repairs by astronauts. All of the tools necessary for service and repairs had to be designed for easy manipulation by a suited astronaut. Construction methods had to be efficient due to the limited time the astronauts could remain outside their controlled environment. In lieu of all the specific needs for this project, an environment on Earth had to be developed that could simulate a low gravity atmosphere. A Neutral Buoyancy Simulator (NBS) was constructed by NASA's Marshall Space Flight Center (MSFC) in 1968. Since then, NASA scientists have used this facility to understand how humans work best in low gravity and also provide information about the different kinds of structures that can be built. Pictured is a Massachusetts Institute of Technology (MIT) student working in a spacesuit on the Experimental Assembly of Structures in Extravehicular Activity (EASE) project which was developed as a joint effort between MFSC and MIT. The EASE experiment required that crew members assemble small components to form larger components, working from the payload bay of the space shuttle. The MIT student in this photo is assembling two six-beam tetrahedrons.

Development And Test of A Digitally Steered Antenna Array for The Navigator GPS Receiver

NASA Technical Reports Server (NTRS)

Pinto, Heitor David; Valdez, Jennifer E.; Winternitz, Luke M. B.; Hassouneh, Munther A.; Price, Samuel R.

2012-01-01

Global Positioning System (GPS)-based navigation has become common for low-Earth orbit spacecraft as the signal environment is similar to that on the Earth s surface. The situation changes abruptly, however, for spacecraft whose orbital altitudes exceed that of the GPS constellation. Visibility is dramatically reduced and signals that are present may be very weak and more susceptible to interference. GPS receivers effective at these altitudes require increased sensitivity, which often requires a high-gain antenna. Pointing such an antenna can pose a challenge. One efficient approach to mitigate these problems is the use of a digitally steered antenna array. Such an antenna can optimally allocate gain toward desired signal sources and away from interferers. This paper presents preliminary results in the development and test of a digitally steered antenna array for the Navigator GPS research program at NASA s Goddard Space Flight Center. In particular, this paper highlights the development of an array and front-end electronics, the development and test of a real-time software GPS receiver, and implementation of three beamforming methods for combining the signals from the array. Additionally, this paper discusses the development of a GPS signal simulator which produces digital samples of the GPS L1C/A signals as they would be received by an arbitrary antenna array configuration. The simulator models transmitter and receiver dynamics, near-far and multipath interference, and has been a critical component in both the development and test of the GPS receiver. The GPS receiver system was tested with real and simulated GPS signals. Preliminary results show that performance improvement was achieved in both the weak signal and interference environments, matching analytical predictions. This paper summarizes our initial findings and discusses the advantages and limitations of the antenna array and the various beamforming methods.

Atomic Oxygen Durability Testing of an International Space Station Solar Array Validation Coupon

NASA Technical Reports Server (NTRS)

Forkapa, Mark J.; Stidham, Curtis; Banks, Bruce A.; Rutledge, Sharon K.; Ma, David H.; Sechkar, Edward A.

1996-01-01

An International Space Station solar array validation coupon was exposed in a directed atomic oxygen beam for space environment durability testing at the NASA Lewis Research Center. Exposure to atomic oxygen and intermittent tensioning of the solar array were conducted to verify the solar array#s durability to low Earth orbital atomic oxygen and to the docking threat of plume loading both of which are anticipated over its expected mission life of fifteen years. The validation coupon was mounted on a specially designed rotisserie. The rotisserie mounting enabled the solar and anti-solar facing side of the array to be exposed to directed atomic oxygen in a sweeping arrival process replicating space exposure. The rotisserie mounting also enabled tensioning, in order to examine the durability of the array and its hinge to simulated plume loads. Flash testing to verify electrical performance of the solar array was performed with a solar simulator before and after the exposure to atomic oxygen and tensile loading. Results of the flash testing indicated little or no degradation in the solar array#s performance. Photographs were also taken of the array before and after the durability testing and are included along with comparisons and discussions in this report. The amount of atomic oxygen damage appeared minor with the exception of a very few isolated defects. There were also no indications that the simulated plume loadings had weakened or damaged the array, even though there was some erosion of Kapton due to atomic oxygen attack. Based on the results of this testing, it is apparent that the International Space Station#s solar arrays should survive the low Earth orbital atomic oxygen environment and docking threats which are anticipated over its expected mission life.

Scripting Module for the Satellite Orbit Analysis Program (SOAP)

NASA Technical Reports Server (NTRS)

Carnright, Robert; Paget, Jim; Coggi, John; Stodden, David

2008-01-01

This add-on module to the SOAP software can perform changes to simulation objects based on the occurrence of specific conditions. This allows the software to encompass simulation response of scheduled or physical events. Users can manipulate objects in the simulation environment under programmatic control. Inputs to the scripting module are Actions, Conditions, and the Script. Actions are arbitrary modifications to constructs such as Platform Objects (i.e. satellites), Sensor Objects (representing instruments or communication links), or Analysis Objects (user-defined logical or numeric variables). Examples of actions include changes to a satellite orbit ( v), changing a sensor-pointing direction, and the manipulation of a numerical expression. Conditions represent the circumstances under which Actions are performed and can be couched in If-Then-Else logic, like performing v at specific times or adding to the spacecraft power only when it is being illuminated by the Sun. The SOAP script represents the entire set of conditions being considered over a specific time interval. The output of the scripting module is a series of events, which are changes to objects at specific times. As the SOAP simulation clock runs forward, the scheduled events are performed. If the user sets the clock back in time, the events within that interval are automatically undone. This script offers an interface for defining scripts where the user does not have to remember the vocabulary of various keywords. Actions can be captured by employing the same user interface that is used to define the objects themselves. Conditions can be set to invoke Actions by selecting them from pull-down lists. Users define the script by selecting from the pool of defined conditions. Many space systems have to react to arbitrary events that can occur from scheduling or from the environment. For example, an instrument may cease to draw power when the area that it is tasked to observe is not in view. The contingency of the planetary body blocking the line of sight is a condition upon which the power being drawn is set to zero. It remains at zero until the observation objective is again in view. Computing the total power drawn by the instrument over a period of days or weeks can now take such factors into consideration. What makes the architecture especially powerful is that the scripting module can look ahead and behind in simulation time, and this temporal versatility can be leveraged in displays such as x-y plots. For example, a plot of a satellite s altitude as a function of time can take changes to the orbit into account.

Simulation of Mercury's magnetosheath with a combined hybrid-paraboloid model

NASA Astrophysics Data System (ADS)

Parunakian, David; Dyadechkin, Sergey; Alexeev, Igor; Belenkaya, Elena; Khodachenko, Maxim; Kallio, Esa; Alho, Markku

2017-08-01

In this paper we introduce a novel approach for modeling planetary magnetospheres that involves a combination of the hybrid model and the paraboloid magnetosphere model (PMM); we further refer to it as the combined hybrid model. While both of these individual models have been successfully applied in the past, their combination enables us both to overcome the traditional difficulties of hybrid models to develop a self-consistent magnetic field and to compensate the lack of plasma simulation in the PMM. We then use this combined model to simulate Mercury's magnetosphere and investigate the geometry and configuration of Mercury's magnetosheath controlled by various conditions in the interplanetary medium. The developed approach provides a unique comprehensive view of Mercury's magnetospheric environment for the first time. Using this setup, we compare the locations of the bow shock and the magnetopause as determined by simulations with the locations predicted by stand-alone PMM runs and also verify the magnetic and dynamic pressure balance at the magnetopause. We also compare the results produced by these simulations with observational data obtained by the magnetometer on board the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft along a dusk-dawn orbit and discuss the signatures of the magnetospheric features that appear in these simulations. Overall, our analysis suggests that combining the semiempirical PMM with a self-consistent global kinetic model creates new modeling possibilities which individual models cannot provide on their own.

Modeling of space environment impact on nanostructured materials. General principles

NASA Astrophysics Data System (ADS)

Voronina, Ekaterina; Novikov, Lev

2016-07-01

In accordance with the resolution of ISO TC20/SC14 WG4/WG6 joint meeting, Technical Specification (TS) 'Modeling of space environment impact on nanostructured materials. General principles' which describes computer simulation methods of space environment impact on nanostructured materials is being prepared. Nanomaterials surpass traditional materials for space applications in many aspects due to their unique properties associated with nanoscale size of their constituents. This superiority in mechanical, thermal, electrical and optical properties will evidently inspire a wide range of applications in the next generation spacecraft intended for the long-term (~15-20 years) operation in near-Earth orbits and the automatic and manned interplanetary missions. Currently, ISO activity on developing standards concerning different issues of nanomaterials manufacturing and applications is high enough. Most such standards are related to production and characterization of nanostructures, however there is no ISO documents concerning nanomaterials behavior in different environmental conditions, including the space environment. The given TS deals with the peculiarities of the space environment impact on nanostructured materials (i.e. materials with structured objects which size in at least one dimension lies within 1-100 nm). The basic purpose of the document is the general description of the methodology of applying computer simulation methods which relate to different space and time scale to modeling processes occurring in nanostructured materials under the space environment impact. This document will emphasize the necessity of applying multiscale simulation approach and present the recommendations for the choice of the most appropriate methods (or a group of methods) for computer modeling of various processes that can occur in nanostructured materials under the influence of different space environment components. In addition, TS includes the description of possible approximations and limitations of proposed simulation methods as well as of widely used software codes. This TS may be used as a base for developing a new standard devoted to nanomaterials applications for spacecraft.

Image based SAR product simulation for analysis

NASA Technical Reports Server (NTRS)

Domik, G.; Leberl, F.

1987-01-01

SAR product simulation serves to predict SAR image gray values for various flight paths. Input typically consists of a digital elevation model and backscatter curves. A new method is described of product simulation that employs also a real SAR input image for image simulation. This can be denoted as 'image-based simulation'. Different methods to perform this SAR prediction are presented and advantages and disadvantages discussed. Ascending and descending orbit images from NASA's SIR-B experiment were used for verification of the concept: input images from ascending orbits were converted into images from a descending orbit; the results are compared to the available real imagery to verify that the prediction technique produces meaningful image data.

Around Marshall

NASA Image and Video Library

1977-04-12

Once the United States' space program had progressed from Earth's orbit into outerspace, the prospect of building and maintaining a permanent presence in space was realized. To accomplish this feat, NASA launched a temporary workstation, Skylab, to discover the effects of low gravity and weightlessness on the human body, and also to develop tools and equipment that would be needed in the future to build and maintain a more permanent space station. The structures, techniques, and work schedules had to be carefully designed to fit this unique construction site. The components had to be lightweight for transport into orbit, yet durable. The station also had to be made with removable parts for easy servicing and repairs by astronauts. All of the tools necessary for service and repairs had to be designed for easy manipulation by a suited astronaut. And construction methods had to be efficient due to limited time the astronauts could remain outside their controlled environment. In lieu of all the specific needs for this project, an environment on Earth had to be developed that could simulate a low gravity atmosphere. A Neutral Buoyancy Simulator (NBS) was constructed by NASA Marshall Space Flight Center (MSFC) in 1968. Since then, NASA scientists have used this facility to understand how humans work best in low gravity and also provide information about the different kinds of structures that can be built.Pictured is an experiment where the astronaut is required to move a large object which weighed 19,000 pounds. It was moved with realitive ease once the astronaut became familiar with his environment and his near weightless condition. Experiments of this nature provided scientists with the information needed regarding weight and mass allowances astronauts could manage in preparation for building a permanent space station in the future.

Neutral Buoyancy Test NB-14 Large Space Structure Assembly

NASA Technical Reports Server (NTRS)

1977-01-01

Once the United States' space program had progressed from Earth's orbit into outerspace, the prospect of building and maintaining a permanent presence in space was realized. To accomplish this feat, NASA launched a temporary workstation, Skylab, to discover the effects of low gravity and weightlessness on the human body, and also to develop tools and equipment that would be needed in the future to build and maintain a more permanent space station. The structures, techniques, and work schedules had to be carefully designed to fit this unique construction site. The components had to be lightweight for transport into orbit, yet durable. The station also had to be made with removable parts for easy servicing and repairs by astronauts. All of the tools necessary for service and repairs had to be designed for easy manipulation by a suited astronaut. And construction methods had to be efficient due to limited time the astronauts could remain outside their controlled environment. In lieu of all the specific needs for this project, an environment on Earth had to be developed that could simulate a low gravity atmosphere. A Neutral Buoyancy Simulator (NBS) was constructed by NASA Marshall Space Flight Center (MSFC) in 1968. Since then, NASA scientists have used this facility to understand how humans work best in low gravity and also provide information about the different kinds of structures that can be built.Pictured is an experiment where the astronaut is required to move a large object which weighed 19,000 pounds. It was moved with realitive ease once the astronaut became familiar with his environment and his near weightless condition. Experiments of this nature provided scientists with the information needed regarding weight and mass allowances astronauts could manage in preparation for building a permanent space station in the future.

The INAF/IAPS Plasma Chamber for ionospheric simulation experiment

NASA Astrophysics Data System (ADS)

Diego, Piero

2016-04-01

The plasma chamber is particularly suitable to perform studies for the following applications: - plasma compatibility and functional tests on payloads envisioned to operate in the ionosphere (e.g. sensors onboard satellites, exposed to the external plasma environment); - calibration/testing of plasma diagnostic sensors; - characterization and compatibility tests on components for space applications (e.g. optical elements, harness, satellite paints, photo-voltaic cells, etc.); - experiments on satellite charging in a space plasma environment; - tests on active experiments which use ion, electron or plasma sources (ion thrusters, hollow cathodes, field effect emitters, plasma contactors, etc.); - possible studies relevant to fundamental space plasma physics. The facility consists of a large volume vacuum tank (a cylinder of length 4.5 m and diameter 1.7 m) equipped with a Kaufman type plasma source, operating with Argon gas, capable to generate a plasma beam with parameters (i.e. density and electron temperature) close to the values encountered in the ionosphere at F layer altitudes. The plasma beam (A+ ions and electrons) is accelerated into the chamber at a velocity that reproduces the relative motion between an orbiting satellite and the ionosphere (≈ 8 km/s). This feature, in particular, allows laboratory simulations of the actual compression and depletion phenomena which take place in the ram and wake regions around satellites moving through the ionosphere. The reproduced plasma environment is monitored using Langmuir Probes (LP) and Retarding Potential Analyzers (RPA). These sensors can be automatically moved within the experimental space using a sled mechanism. Such a feature allows the acquisition of the plasma parameters all around the space payload installed into the chamber for testing. The facility is currently in use to test the payloads of CSES satellite (Chinese Seismic Electromagnetic Satellite) devoted to plasma parameters and electric field measurements in a polar orbit at 500 km altitude.

Design Concept for a Reusable/Propellantless MXER Tether Space Transportation System

NASA Technical Reports Server (NTRS)

McCandless, B., II; Kustas, F. m.; Marshall, L. S.; Lytle, W. B.; Hansen, N. P.

2005-01-01

The Momentum Exchange/Electrodynamic Reboost (MXER) tether facility is a transformational concept that significantly reduces the fuel requirements (and associated costs) in transferring payloads above low earth orbit (LEO). Facility reboost is accomplished without propellant by driving current against a voltage created by a conducting tether's interaction with the Earth's magnetic field (electrodynamic reboost). This system can be used for transferring a variety of payloads (scientific, cargo, and human space vehicles) to multiple destinations including geosynchronous transfer orbit, the Moon or Mars. MXER technology advancement requires development in two key areas: survivable, high tensile strength non-conducting tethers and reliable, lightweight payload catch/release mechanisms. Fundamental requirements associated with the MXER non-conducting strength tether and catch mechanism designs will be presented. Key requirements for the tether design include high specific-strength (tensile strength/material density), material survivability to the space environment (atomic oxygen and ultraviolet radiation), and structural survivability to micrometeoroid/orbital debris (MM/OD) impacts. The driving mechanism key,gequirements include low mass-to-capture-volume ratio, positional and velocity error tolerance, and operational reliability. Preliminary tether and catch mechanism design criteria are presented, which have been used as guidelines to "screen" and down-select initial concepts. Candidate tether materials and protective coatings are summarized along with their performance in simulated space environments (e.g., oxygen plasma, thermal cycling). A candidate catch mechanism design concept is presented along with examples of demonstration hardware.

PLANETARY EMBRYO BOW SHOCKS AS A MECHANISM FOR CHONDRULE FORMATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mann, Christopher R.; Boley, Aaron C.; Morris, Melissa A.

2016-02-20

We use radiation hydrodynamics with direct particle integration to explore the feasibility of chondrule formation in planetary embryo bow shocks. The calculations presented here are used to explore the consequences of a Mars-size planetary embryo traveling on a moderately excited orbit through the dusty, early environment of the solar system. The embryo’s eccentric orbit produces a range of supersonic relative velocities between the embryo and the circularly orbiting gas and dust, prompting the formation of bow shocks. Temporary atmospheres around these embryos, which can be created via volatile outgassing and gas capture from the surrounding nebula, can non-trivially affect thermalmore » profiles of solids entering the shock. We explore the thermal environment of solids that traverse the bow shock at different impact radii, the effects that planetoid atmospheres have on shock morphologies, and the stripping efficiency of planetoidal atmospheres in the presence of high relative winds. Simulations are run using adiabatic and radiative conditions, with multiple treatments for the local opacities. Shock speeds of 5, 6, and 7 km s{sup −1} are explored. We find that a high-mass atmosphere and inefficient radiative conditions can produce peak temperatures and cooling rates that are consistent with the constraints set by chondrule furnace studies. For most conditions, the derived cooling rates are potentially too high to be consistent with chondrule formation.« less

Galactic star formation enhanced and quenched by ram pressure in groups and clusters

NASA Astrophysics Data System (ADS)

Bekki, Kenji

2014-02-01

We investigate how ram pressure of intragroup and intracluster medium can influence the spatial and temporal variations of star formation (SF) of disc galaxies with halo masses (Mh) ranging from 1010 to 1012 M⊙ (i.e. from dwarf irregular to Milky Way-type) in groups and clusters with 1013 ≤ Mh/M⊙ ≤ 1015 by using numerical simulations with a new model for time-varying ram pressure. The long-term evolution of SF rates and Hα morphologies corresponding to the distributions of star-forming regions are particularly investigated for different model parameters. The principal results are as follows. Whether ram pressure can enhance or reduce SF depends on Mh of disc galaxies and inclination angles of gas discs with respect to their orbital directions for a given orbit and a given environment. For example, SF can be moderately enhanced in disc galaxies with Mh = 1012 M⊙ at the pericentre passages in a cluster with Mh = 1014 M⊙ whereas it can be completely shut down (`quenching') for low-mass discs with Mh = 1010 M⊙. Ram pressure can reduce the Hα-to-optical-disc-size ratios of discs and the level of the reduction depends on Mh and orbits of disc galaxies for a given environment. Disc galaxies under strong ram pressure show characteristic Hα morphologies such as ring-like, one-sided and crescent-like distributions.

Optical and Chemical Characterization of Polyimide in a GEO-like Environment

NASA Astrophysics Data System (ADS)

Engelhart, D.; Plis, E.; Ferguson, D.; Cooper, R.; Hoffmann, R.

2016-09-01

Ground- and space-based optical observations of space objects rely on knowledge about how spacecraft materials interact with light. However, this is not a static property. Each material's optical fingerprint changes continuously throughout a spacecraft's orbital lifetime. These changes in optical signature occur because energetic particles break bonds within a material and new bonds subsequently form. The newly formed bonds can be identical to the original bonds or different, resulting in a new material. The chemical bonds comprising the material dictate which wavelengths of light are absorbed. Understanding the processes of material damage and recovery individually will allow development of a predictive model for materials' optical properties as a function of exposure to the space environment. In order to characterize the properties, we have exposed samples of polyimide to high energy electrons comparable to those found in a geostationary earth orbit in order to simulate damage on orbit. The resultant changes in the material's optical fingerprint were then characterized in the wavelength range of 0.2 to 25 microns. The chemical modifications to the material that result in these optical changes have also been identified. After initial electron-induced damage, the rate and mechanism of material recovery have been monitored and found to be extremely sensitive to the exposure of the damaged material to air. The implications of that fact and experimental progress toward complete in vacuo characterization will be discussed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herdiwijaya, Dhani, E-mail: dhani@as.itb.ac.id; Rachman, Abdul

Any man-made object in Earth's orbit that no longer serves a useful purpose is classified as orbital debris. Debris objects come from a variety of sources. The majority is related to satellite fragmentation. Other major sources of debris are propulsion systems, and fragmentation of spent upper stages, payload and mission related debris. Serious concern about orbital debris has been growing. Knowledge of the future debris environment is important to both satellite designers, and mission planners, who need to know what hazards a satellite might encounter during the course of its mission. Therefore, it is important to know how much debrismore » is in orbit, where it is located, and when it will decay. The debris environment is complex and dynamically evolving. Objects of different shape and size behave differently in orbit. The geoeffectiveness space environments include solar flux at 10.7 cm, solar energetic particles flux or speed, solar wind flow pressure, electric field, and geomagnetic indices. We study the decaying orbital debris from Tracking and Impact Prediction (TIP) messages in conjuction with geoeffectiveness space environments through time epoch correlation. We found that the decaying and reentry orbital debris are triggered by space environment enhancement within at least one week before reentry. It is not necessary a transient or high energetic and severe solar storm events are needed in decaying processes. We propose that the gradual enhancement processes of space environment will cause satellite surface charging due to energetic electron and enhance drag force.« less

Computer program determines thermal environment and temperature history of lunar orbiting space vehicles

NASA Technical Reports Server (NTRS)

Head, D. E.; Mitchell, K. L.

1967-01-01

Program computes the thermal environment of a spacecraft in a lunar orbit. The quantities determined include the incident flux /solar and lunar emitted radiation/, total radiation absorbed by a surface, and the resulting surface temperature as a function of time and orbital position.

Meteoroids and Orbital Debris: Effects on Spacecraft

NASA Technical Reports Server (NTRS)

Belk, Cynthia A.; Robinson, Jennifer H.; Alexander, Margaret B.; Cooke, William J.; Pavelitz, Steven D.

1997-01-01

The natural space environment is characterized by many complex and subtle phenomena hostile to spacecraft. The effects of these phenomena impact spacecraft design, development, and operations. Space systems become increasingly susceptible to the space environment as use of composite materials and smaller, faster electronics increases. This trend makes an understanding of the natural space environment essential to accomplish overall mission objectives, especially in the current climate of better/cheaper/faster. Meteoroids are naturally occurring phenomena in the natural space environment. Orbital debris is manmade space litter accumulated in Earth orbit from the exploration of space. Descriptions are presented of orbital debris source, distribution, size, lifetime, and mitigation measures. This primer is one in a series of NASA Reference Publications currently being developed by the Electromagnetics and Aerospace Environments Branch, Systems Analysis and Integration Laboratory, Marshall Space Flight Center, National Aeronautics and Space Administration.

Highlights of Recent Research Activities at the NASA Orbital Debris Program Office

NASA Technical Reports Server (NTRS)

Liou, J - C.

2017-01-01

The NASA Orbital Debris Program Office (ODPO) was established at the NASA Johnson Space Center in 1979. The ODPO has initiated and led major orbital debris research activities over the past 38 years, including developing the first set of the NASA orbital debris mitigation requirements in 1995 and supporting the establishment of the U.S. Government Orbital Debris Mitigation Standard Practices in 2001. This paper is an overview of the recent ODPO research activities, ranging from ground-based and in-situ measurements, to laboratory tests, and to engineering and long-term orbital debris environment modeling. These activities highlight the ODPO's commitment to continuously improve the orbital debris environment definition to better protect current and future space missions from the low Earth orbit to the geosynchronous Earth orbit regions.

CCSDS Advanced Orbiting Systems Virtual Channel Access Service for QoS MACHETE Model

NASA Technical Reports Server (NTRS)

Jennings, Esther H.; Segui, John S.

2011-01-01

To support various communications requirements imposed by different missions, interplanetary communication protocols need to be designed, validated, and evaluated carefully. Multimission Advanced Communications Hybrid Environment for Test and Evaluation (MACHETE), described in "Simulator of Space Communication Networks" (NPO-41373), NASA Tech Briefs, Vol. 29, No. 8 (August 2005), p. 44, combines various tools for simulation and performance analysis of space networks. The MACHETE environment supports orbital analysis, link budget analysis, communications network simulations, and hardware-in-the-loop testing. By building abstract behavioral models of network protocols, one can validate performance after identifying the appropriate metrics of interest. The innovators have extended the MACHETE model library to include a generic link-layer Virtual Channel (VC) model supporting quality-of-service (QoS) controls based on IP streams. The main purpose of this generic Virtual Channel model addition was to interface fine-grain flow-based QoS (quality of service) between the network and MAC layers of the QualNet simulator, a commercial component of MACHETE. This software model adds the capability of mapping IP streams, based on header fields, to virtual channel numbers, allowing extended QoS handling at link layer. This feature further refines the QoS v existing at the network layer. QoS at the network layer (e.g. diffserv) supports few QoS classes, so data from one class will be aggregated together; differentiating between flows internal to a class/priority is not supported. By adding QoS classification capability between network and MAC layers through VC, one maps multiple VCs onto the same physical link. Users then specify different VC weights, and different queuing and scheduling policies at the link layer. This VC model supports system performance analysis of various virtual channel link-layer QoS queuing schemes independent of the network-layer QoS systems.

Three dimensional Particle-in-Cell (PIC) simulations of the 67P environment

NASA Astrophysics Data System (ADS)

Divin, Andrey; Deca, Jan; Henri, Pierre; Horanyi, Mihaly; Markidis, Stefano; Lapenta, Giovanni; Olshevsky, Vyacheslav; Eriksson, Anders

2017-04-01

ESA's Rosetta orbiter spacecraft escorted comet 67P/Churyumov-Gerasimenko for two years, carrying 21 scientific instruments. Five of those were dedicated to plasma measurements. The mission revealed for the first time, and in unprecedented detail, the fascinating evolution of a comet and its interaction with our Sun as it races along its 6.45yr elliptical orbit around the Sun. Using a self-consistent 3-D fully kinetic electromagnetic particle-in-cell approach, we focus on the global cometary environment and, in particular, on the collisionless electron-kinetic interaction. We include cometary ions and electrons produced by the ionization of the outgassing cometary atmosphere in addition to the solar wind ion and electron plasma flow. We approximate mass-loading of the cold cometary ion and electron populations using a 1/r relation with distance to the comet with a total neutral production rate of Q = 1026 s-1. Our simulation results disentangle for the first time the kinetic ion and electron dynamics of the solar wind interaction with a weakly outgassing comet. The simulated global structure of the solar wind-comet interaction confirms the results reported in hybrid simulations of the induced cometary magnetosphere. Moreover, we show that cometary and solar wind electrons neutralize the solar wind protons and cometary ions, respectively, in the region of influence around the comet, representing to first order a four-fluid behavior. The electron energy distribution close to the comet is shown to be a mix of cometary and solar wind electrons that appear as, respectively, a thermal and a suprathermal components. Analyzing ion and electron energy distribution functions, and comparing with plasma measurements from ESA's Rosetta mission to comet 67P/Churyumov-Gerasimenko, we conclude that a detailed kinetic treatment of the electron dynamics is critical to fully capture the complex physics of mass-loading plasmas.

Feasibility Study of SSTO Base Heating Simulation in Pulsed-Type Facilities

NASA Technical Reports Server (NTRS)

Park, Chung Sik; Sharma, Surendra; Edwards, Thomas A. (Technical Monitor)

1995-01-01

A laboratory simulation of the base heating environment of the proposed reusable Single-Stage-To-Orbit vehicle during its ascent flight was proposed. The rocket engine produces CO2 and H2, which are the main combustible components of the exhaust effluent. The burning of these species, known as afterburning, enhances the base region gas temperature as well as the base heating. To determine the heat flux on the SSTO vehicle, current simulation focuses on the thermochemistry of the afterburning, thermophysical properties of the base region gas, and ensuing radiation from the gas. By extrapolating from the Saturn flight data, the Damkohler number for the afterburning of SSTO vehicle is estimated to be of the order of 10. The limitations on the material strengths limit the laboratory simulation of the flight Damkohler number as well as other flow parameters. A plan is presented in impulse facilities using miniature rocket engines which generate the simulated rocket plume by electric ally-heating a H2/CO2 mixture.

Integration of communications and tracking data processing simulation for space station

NASA Technical Reports Server (NTRS)

Lacovara, Robert C.

1987-01-01

A simplified model of the communications network for the Communications and Tracking Data Processing System (CTDP) was developed. It was simulated by use of programs running on several on-site computers. These programs communicate with one another by means of both local area networks and direct serial connections. The domain of the model and its simulation is from Orbital Replaceable Unit (ORU) interface to Data Management Systems (DMS). The simulation was designed to allow status queries from remote entities across the DMS networks to be propagated through the model to several simulated ORU's. The ORU response is then propagated back to the remote entity which originated the request. Response times at the various levels were investigated in a multi-tasking, multi-user operating system environment. Results indicate that the effective bandwidth of the system may be too low to support expected data volume requirements under conventional operating systems. Instead, some form of embedded process control program may be required on the node computers.

Research on orbit prediction for solar-based calibration proper satellite

NASA Astrophysics Data System (ADS)

Chen, Xuan; Qi, Wenwen; Xu, Peng

2018-03-01

Utilizing the mathematical model of the orbit mechanics, the orbit prediction is to forecast the space target's orbit information of a certain time based on the orbit of the initial moment. The proper satellite radiometric calibration and calibration orbit prediction process are introduced briefly. On the basis of the research of the calibration space position design method and the radiative transfer model, an orbit prediction method for proper satellite radiometric calibration is proposed to select the appropriate calibration arc for the remote sensor and to predict the orbit information of the proper satellite and the remote sensor. By analyzing the orbit constraint of the proper satellite calibration, the GF-1solar synchronous orbit is chose as the proper satellite orbit in order to simulate the calibration visible durance for different satellites to be calibrated. The results of simulation and analysis provide the basis for the improvement of the radiometric calibration accuracy of the satellite remote sensor, which lays the foundation for the high precision and high frequency radiometric calibration.

Spin-orbit scattering visualized in quasiparticle interference

NASA Astrophysics Data System (ADS)

Kohsaka, Y.; Machida, T.; Iwaya, K.; Kanou, M.; Hanaguri, T.; Sasagawa, T.

2017-03-01

In the presence of spin-orbit coupling, electron scattering off impurities depends on both spin and orbital angular momentum of electrons—spin-orbit scattering. Although some transport properties are subject to spin-orbit scattering, experimental techniques directly accessible to this effect are limited. Here we show that a signature of spin-orbit scattering manifests itself in quasiparticle interference (QPI) imaged by spectroscopic-imaging scanning tunneling microscopy. The experimental data of a polar semiconductor BiTeI are well reproduced by numerical simulations with the T -matrix formalism that include not only scalar scattering normally adopted but also spin-orbit scattering stronger than scalar scattering. To accelerate the simulations, we extend the standard efficient method of QPI calculation for momentum-independent scattering to be applicable even for spin-orbit scattering. We further identify a selection rule that makes spin-orbit scattering visible in the QPI pattern. These results demonstrate that spin-orbit scattering can exert predominant influence on QPI patterns and thus suggest that QPI measurement is available to detect spin-orbit scattering.

KENNEDY SPACE CENTER, FLA. - Emergency crew members lower a volunteer “astronaut” from the top of the orbiter crew compartment mock-up that is the scene of a “Mode VII” emergency landing simulation at Kennedy Space Center. The purpose of the Mode VII is to exercise emergency preparedness personnel, equipment and facilities in rescuing astronauts from a downed orbiter and providing immediate medical attention. This simulation presents an orbiter that has crashed short of the Shuttle Landing Facility in a wooded area 2-1/2 miles south of Runway 33. Emergency crews are responding to the volunteer “astronauts” who are simulating various injuries. Rescuers must remove the crew, provide triage and transport to hospitals those who need further treatment. Local hospitals are participating in the exercise.

NASA Image and Video Library

2004-02-18

KENNEDY SPACE CENTER, FLA. - Emergency crew members lower a volunteer “astronaut” from the top of the orbiter crew compartment mock-up that is the scene of a “Mode VII” emergency landing simulation at Kennedy Space Center. The purpose of the Mode VII is to exercise emergency preparedness personnel, equipment and facilities in rescuing astronauts from a downed orbiter and providing immediate medical attention. This simulation presents an orbiter that has crashed short of the Shuttle Landing Facility in a wooded area 2-1/2 miles south of Runway 33. Emergency crews are responding to the volunteer “astronauts” who are simulating various injuries. Rescuers must remove the crew, provide triage and transport to hospitals those who need further treatment. Local hospitals are participating in the exercise.

Space tug geosynchronous mission simulation

NASA Technical Reports Server (NTRS)

Lang, T. J.

1973-01-01

Near-optimal three dimensional trajectories from a low earth park orbit inclined at 28.5 deg to a synchronous-equatorial mission orbit were developed for both the storable (thrust = 28,912 N (6,500 lbs), I sub sp = 339 sec) and cryogenic (thrust = 44,480 N (10,000 lbs), I sub sp = 470 sec) space tug using the iterative cost function minimization technique contained within the modularized vehicle simulation (MVS) program. The finite burn times, due to low thrust-to-weight ratios, and the associated gravity losses are accounted for in the trajectory simulation and optimization. The use of an ascent phasing orbit to achieve burnout in synchronous orbit at any longitude is investigated. The ascent phasing orbit is found to offer the additional advantage of significantly reducing the overall delta velocity by splitting the low altitude burn into two parts and thereby reducing gravity losses.

Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics (ROCKE-3D) 1.0: A General Circulation Model for Simulating the Climates of Rocky Planets

NASA Astrophysics Data System (ADS)

Way, M. J.; Aleinov, I.; Amundsen, David S.; Chandler, M. A.; Clune, T. L.; Del Genio, A. D.; Fujii, Y.; Kelley, M.; Kiang, N. Y.; Sohl, L.; Tsigaridis, K.

2017-07-01

Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics (ROCKE-3D) is a three-dimensional General Circulation Model (GCM) developed at the NASA Goddard Institute for Space Studies for the modeling of atmospheres of solar system and exoplanetary terrestrial planets. Its parent model, known as ModelE2, is used to simulate modern Earth and near-term paleo-Earth climates. ROCKE-3D is an ongoing effort to expand the capabilities of ModelE2 to handle a broader range of atmospheric conditions, including higher and lower atmospheric pressures, more diverse chemistries and compositions, larger and smaller planet radii and gravity, different rotation rates (from slower to more rapid than modern Earth’s, including synchronous rotation), diverse ocean and land distributions and topographies, and potential basic biosphere functions. The first aim of ROCKE-3D is to model planetary atmospheres on terrestrial worlds within the solar system such as paleo-Earth, modern and paleo-Mars, paleo-Venus, and Saturn’s moon Titan. By validating the model for a broad range of temperatures, pressures, and atmospheric constituents, we can then further expand its capabilities to those exoplanetary rocky worlds that have been discovered in the past, as well as those to be discovered in the future. We also discuss the current and near-future capabilities of ROCKE-3D as a community model for studying planetary and exoplanetary atmospheres.

Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics (ROCKE-3D) 1.0: A General Circulation Model for Simulating the Climates of Rocky Planets

NASA Technical Reports Server (NTRS)

Way, M. J.; Aleinov, I.; Amundsen, David S.; Chandler, M. A.; Clune, T. L.; Del Genio, A.; Fujii, Y.; Kelley, M.; Kiang, N. Y.; Sohl, L.;

Guidance and control 1991; Proceedings of the Annual Rocky Mountain Guidance and Control Conference, Keystone, CO, Feb. 2-6, 1991

NASA Astrophysics Data System (ADS)

Culp, Robert D.; McQuerry, James P.

1991-07-01

The present conference on guidance and control encompasses advances in guidance, navigation, and control, storyboard displays, approaches to space-borne pointing control, international space programs, recent experiences with systems, and issues regarding navigation in the low-earth-orbit space environment. Specific issues addressed include a scalable architecture for an operational spaceborne autonavigation system, the mitigation of multipath error in GPS-based attitude determination, microgravity flight testing of a laboratory robot, and the application of neural networks. Other issues addressed include image navigation with second-generation Meteosat, Magellan star-scanner experiences, high-precision control systems for telescopes and interferometers, gravitational effects on low-earth orbiters, experimental verification of nanometer-level optical pathlengths, and a flight telerobotic servicer prototype simulator. (For individual items see A93-15577 to A93-15613)

Low Earth orbital atomic oxygen and ultraviolet radiation effects on polymers

NASA Technical Reports Server (NTRS)

Dever, Joyce A.

1991-01-01

Because atomic oxygen and solar ultraviolet radiation present in the low earth orbital (LEO) environment can alter the chemistry of polymers resulting in degradation, their effects and mechanisms of degradation must be determined in order to determine the long term durability of polymeric surfaces to be exposed on missions such as Space Station Freedom. The effects of atomic oxygen on polymers which contain protective coatings must also be explored, since unique damage mechanisms can occur in areas where the protective coatings has failed. Mechanisms can be determined by utilizing results from previous LEO missions, by performing ground based LEO simulation tests and analysis, and by carrying out focussed space experiments. A survey is presented of the interactions and possible damage mechanisms for environmental atomic oxygen and UV radiation exposure of polymers commonly used in LEO.

Evaluation of fluid behavior in spinning toroidal tanks

NASA Technical Reports Server (NTRS)

Anderson, J. E.; Fester, D. A.; Dugan, D. W.

1976-01-01

An experimental study was conducted to evaluate propellant behavior in spinning toroidal tanks that could be used in a retro-propulsion system of an advanced outer-planet Pioneer orbiter. Information on propellant slosh and settling and on ullage orientation and stability was obtained. The effects of axial acceleration, spin rate, spin rate change, and spacecraft wobble, both singly and in combination, were evaluated using a 1/8-scale transparent tank in one-g and low-g environments. Liquid loadings ranged from 5% to 96% full. The impact of a surface tension acquisition device was assessed. Testing simulated the behavior of F2/N2H4 and N2O4/MMH propellants. Results are presented which indicate no major fluid behavior problems would be encountered with any of the four propellants in the toroidal tanks of a spin-stabilized orbiter spacecraft.

Fluid interaction with spinning toroidal tanks

NASA Technical Reports Server (NTRS)

Fester, D. A.; Anderson, J. E.

1977-01-01

An experimental study was conducted to evaluate propellant behavior in spinning torroidal tanks that could be used in a retropropulsion system of an advanced outer-planet Pioneer orbiter. Information on propellant slosh and settling and on ullage orientation and stability was obtained. The effects of axial acceleration, spin rate, spin-rate change, and spacecraft wobble, both singly and in combination, were evaluated using a one-eighth scale transparent tank in one-g and low-g environments. Liquid loadings ranged from 5% to 96% full. The impact of a surface tension acquisition device was assessed by comparison with bare-tank results. The testing simulated the behavior of the fluorine/hydrazine and nitrogen textroxide/monomethylhydrazine propellants. Results are presented that indicate that no major fluid behavior problems would be encountered with any of the four propellants in the toroidal tanks of a spin-stabilized orbiter spacecraft.

Noise-induced errors in geophysical parameter estimation from retarding potential analyzers in low Earth orbit

NASA Astrophysics Data System (ADS)

Debchoudhury, Shantanab; Earle, Gregory

2017-04-01

Retarding Potential Analyzers (RPA) have a rich flight heritage. Standard curve-fitting analysis techniques exist that can infer state variables in the ionospheric plasma environment from RPA data, but the estimation process is prone to errors arising from a number of sources. Previous work has focused on the effects of grid geometry on uncertainties in estimation; however, no prior study has quantified the estimation errors due to additive noise. In this study, we characterize the errors in estimation of thermal plasma parameters by adding noise to the simulated data derived from the existing ionospheric models. We concentrate on low-altitude, mid-inclination orbits since a number of nano-satellite missions are focused on this region of the ionosphere. The errors are quantified and cross-correlated for varying geomagnetic conditions.

Business intelligence modeling in launch operations

NASA Astrophysics Data System (ADS)

Bardina, Jorge E.; Thirumalainambi, Rajkumar; Davis, Rodney D.

2005-05-01

The future of business intelligence in space exploration will focus on the intelligent system-of-systems real-time enterprise. In present business intelligence, a number of technologies that are most relevant to space exploration are experiencing the greatest change. Emerging patterns of set of processes rather than organizational units leading to end-to-end automation is becoming a major objective of enterprise information technology. The cost element is a leading factor of future exploration systems. This technology project is to advance an integrated Planning and Management Simulation Model for evaluation of risks, costs, and reliability of launch systems from Earth to Orbit for Space Exploration. The approach builds on research done in the NASA ARC/KSC developed Virtual Test Bed (VTB) to integrate architectural, operations process, and mission simulations for the purpose of evaluating enterprise level strategies to reduce cost, improve systems operability, and reduce mission risks. The objectives are to understand the interdependency of architecture and process on recurring launch cost of operations, provide management a tool for assessing systems safety and dependability versus cost, and leverage lessons learned and empirical models from Shuttle and International Space Station to validate models applied to Exploration. The systems-of-systems concept is built to balance the conflicting objectives of safety, reliability, and process strategy in order to achieve long term sustainability. A planning and analysis test bed is needed for evaluation of enterprise level options and strategies for transit and launch systems as well as surface and orbital systems. This environment can also support agency simulation based acquisition process objectives. The technology development approach is based on the collaborative effort set forth in the VTB's integrating operations, process models, systems and environment models, and cost models as a comprehensive disciplined enterprise analysis environment. Significant emphasis is being placed on adapting root cause from existing Shuttle operations to exploration. Technical challenges include cost model validation, integration of parametric models with discrete event process and systems simulations, and large-scale simulation integration. The enterprise architecture is required for coherent integration of systems models. It will also require a plan for evolution over the life of the program. The proposed technology will produce long-term benefits in support of the NASA objectives for simulation based acquisition, will improve the ability to assess architectural options verses safety/risk for future exploration systems, and will facilitate incorporation of operability as a systems design consideration, reducing overall life cycle cost for future systems.

Business Intelligence Modeling in Launch Operations

NASA Technical Reports Server (NTRS)

Bardina, Jorge E.; Thirumalainambi, Rajkumar; Davis, Rodney D.

2005-01-01

This technology project is to advance an integrated Planning and Management Simulation Model for evaluation of risks, costs, and reliability of launch systems from Earth to Orbit for Space Exploration. The approach builds on research done in the NASA ARC/KSC developed Virtual Test Bed (VTB) to integrate architectural, operations process, and mission simulations for the purpose of evaluating enterprise level strategies to reduce cost, improve systems operability, and reduce mission risks. The objectives are to understand the interdependency of architecture and process on recurring launch cost of operations, provide management a tool for assessing systems safety and dependability versus cost, and leverage lessons learned and empirical models from Shuttle and International Space Station to validate models applied to Exploration. The systems-of-systems concept is built to balance the conflicting objectives of safety, reliability, and process strategy in order to achieve long term sustainability. A planning and analysis test bed is needed for evaluation of enterprise level options and strategies for transit and launch systems as well as surface and orbital systems. This environment can also support agency simulation .based acquisition process objectives. The technology development approach is based on the collaborative effort set forth in the VTB's integrating operations. process models, systems and environment models, and cost models as a comprehensive disciplined enterprise analysis environment. Significant emphasis is being placed on adapting root cause from existing Shuttle operations to exploration. Technical challenges include cost model validation, integration of parametric models with discrete event process and systems simulations. and large-scale simulation integration. The enterprise architecture is required for coherent integration of systems models. It will also require a plan for evolution over the life of the program. The proposed technology will produce long-term benefits in support of the NASA objectives for simulation based acquisition, will improve the ability to assess architectural options verses safety/risk for future exploration systems, and will facilitate incorporation of operability as a systems design consideration, reducing overall life cycle cost for future systems. The future of business intelligence of space exploration will focus on the intelligent system-of-systems real-time enterprise. In present business intelligence, a number of technologies that are most relevant to space exploration are experiencing the greatest change. Emerging patterns of set of processes rather than organizational units leading to end-to-end automation is becoming a major objective of enterprise information technology. The cost element is a leading factor of future exploration systems.

Development of HWIL Testing Capabilities for Satellite Target Emulation at AEDC

NASA Astrophysics Data System (ADS)

Lowry, H.; Crider, D.; Burns, J.; Thompson, R.; Goldsmith, G., II; Sholes, W.

Programs involved in Space Situational Awareness (SSA) need the capability to test satellite sensors in a Hardware-in-the-Loop (HWIL) environment. Testing in a ground system avoids the significant cost of on-orbit test targets and the resulting issues such as debris mitigation, and in-space testing implications. The space sensor test facilities at AEDC consist of cryo-vacuum chambers that have been developed to project simulated targets to air-borne, space-borne, and ballistic platforms. The 7V chamber performs calibration and characterization of surveillance and seeker systems, as well as some mission simulation. The 10V chamber is being upgraded to provide real-time target simulation during the detection, acquisition, discrimination, and terminal phases of a seeker mission. The objective of the Satellite Emulation project is to upgrade this existing capability to support the ability to discern and track other satellites and orbital debris in a HWIL capability. It would provide a baseline for realistic testing of satellite surveillance sensors, which would be operated in a controlled environment. Many sensor functions could be tested, including scene recognition and maneuvering control software, using real interceptor hardware and software. Statistically significant and repeatable datasets produced by the satellite emulation system can be acquired during such test and saved for further analysis. In addition, the robustness of the discrimination and tracking algorithms can be investigated by a parametric analysis using slightly different scenarios; this will be used to determine critical points where a sensor system might fail. The radiometric characteristics of satellites are expected to be similar to the targets and decoys that make up a typical interceptor mission scenario, since they are near ambient temperature. Their spectral reflectivity, emissivity, and shape must also be considered, but the projection systems employed in the 7V and 10V chambers should be capable of providing the simulation of satellites as well. There may also be a need for greater radiometric intensity or shorter time response. An appropriate satellite model is integral to the scene generation process to meet the requirements of SSA programs. The Kinetic Kill Vehicle Hardware-in-the-Loop Simulator (KHILS) facility and the Guided Weapons Evaluation Facility (GWEF), both at Eglin Air Force Base, FL are assisting in developing the scene projection hardware, based on their significant test experience using resistive emitter arrays to test interceptors in a real-time environment. Army Aviation and Missile Research & Development Command (AMRDEC) will develop the Scene Generation System for the real-time mission simulation.

Innocent Bystanders: Orbital Dynamics of Exomoons During Planet–Planet Scattering

NASA Astrophysics Data System (ADS)

Hong, Yu-Cian; Raymond, Sean N.; Nicholson, Philip D.; Lunine, Jonathan I.

2018-01-01

Planet–planet scattering is the leading mechanism to explain the broad eccentricity distribution of observed giant exoplanets. Here we study the orbital stability of primordial giant planet moons in this scenario. We use N-body simulations including realistic oblateness and evolving spin evolution for the giant planets. We find that the vast majority (∼80%–90% across all our simulations) of orbital parameter space for moons is destabilized. There is a strong radial dependence, as moons past ∼ 0.1 {R}{Hill} are systematically removed. Closer-in moons on Galilean-moon-like orbits (<0.04 R Hill) have a good (∼20%–40%) chance of survival. Destabilized moons may undergo a collision with the star or a planet, be ejected from the system, be captured by another planet, be ejected but still orbiting its free-floating host planet, or survive on heliocentric orbits as “planets.” The survival rate of moons increases with the host planet mass but is independent of the planet’s final (post-scattering) orbits. Based on our simulations, we predict the existence of an abundant galactic population of free-floating (former) moons.

True orbit simulation of piecewise linear and linear fractional maps of arbitrary dimension using algebraic numbers

NASA Astrophysics Data System (ADS)

Saito, Asaki; Yasutomi, Shin-ichi; Tamura, Jun-ichi; Ito, Shunji

2015-06-01

We introduce a true orbit generation method enabling exact simulations of dynamical systems defined by arbitrary-dimensional piecewise linear fractional maps, including piecewise linear maps, with rational coefficients. This method can generate sufficiently long true orbits which reproduce typical behaviors (inherent behaviors) of these systems, by properly selecting algebraic numbers in accordance with the dimension of the target system, and involving only integer arithmetic. By applying our method to three dynamical systems—that is, the baker's transformation, the map associated with a modified Jacobi-Perron algorithm, and an open flow system—we demonstrate that it can reproduce their typical behaviors that have been very difficult to reproduce with conventional simulation methods. In particular, for the first two maps, we show that we can generate true orbits displaying the same statistical properties as typical orbits, by estimating the marginal densities of their invariant measures. For the open flow system, we show that an obtained true orbit correctly converges to the stable period-1 orbit, which is inherently possessed by the system.

Orbital Dynamics of Exomoons During Planet–Planet Scattering

NASA Astrophysics Data System (ADS)

Hong, Yu-Cian; Lunine, Jonathan I.; Nicholson, Philip; Raymond, Sean N.

2018-04-01

Planet–planet scattering is the leading mechanism to explain the broad eccentricity distribution of observed giant exoplanets. Here we study the orbital stability of primordial giant planet moons in this scenario. We use N-body simulations including realistic oblateness and evolving spin evolution for the giant planets. We find that the vast majority (~80%–90% across all our simulations) of orbital parameter space for moons is destabilized. There is a strong radial dependence, as moons past are systematically removed. Closer-in moons on Galilean-moon-like orbits (<0.04 R Hill) have a good (~20%–40%) chance of survival. Destabilized moons may undergo a collision with the star or a planet, be ejected from the system, be captured by another planet, be ejected but still orbiting its free-floating host planet, or survive on heliocentric orbits as "planets." The survival rate of moons increases with the host planet mass but is independent of the planet's final (post-scattering) orbits. Based on our simulations, we predict the existence of an abundant galactic population of free-floating (former) moons.

An Orbit And Dispersion Correction Scheme for the PEP II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, Y.; Donald, M.; Shoaee, H.

2011-09-01

To achieve optimum luminosity in a storage ring it is vital to control the residual vertical dispersion. In the original PEP storage ring, a scheme to control the residual dispersion function was implemented using the ring orbit as the controlling element. The 'best' orbit not necessarily giving the lowest vertical dispersion. A similar scheme has been implemented in both the on-line control code and in the simulation code LEGO. The method involves finding the response matrices (sensitivity of orbit/dispersion at each Beam-Position-Monitor (BPM) to each orbit corrector) and solving in a least squares sense for minimum orbit, dispersion function ormore » both. The optimum solution is usually a subset of the full least squares solution. A scheme of simultaneously correcting the orbits and dispersion has been implemented in the simulation code and on-line control system for PEP-II. The scheme is based on the eigenvector decomposition method. An important ingredient of the scheme is to choose the optimum eigenvectors that minimize the orbit, dispersion and corrector strength. Simulations indicate this to be a very effective way to control the vertical residual dispersion.« less

Mid- and long-term debris environment projections using the EVOLVE and CHAIN models

NASA Astrophysics Data System (ADS)

Eichler, Peter; Reynolds, Robert C.

1995-06-01

Results of debris environment projections are of great importance for the evaluation of the necessity and effectiveness of debris mitigation measures. EVOLVE and CHAIN are two models for debris environment projections that have been developed independently using different conceptual approaches. A comparison of results from these two models therefore provides a means of validating debris environment projections which they have made. EVOLVE is a model that requires mission model projections to describe future space operation; these projections include launch date, mission orbit altitude and inclimation, mission duration, vehicle size and mass, and classification as an object capable of experiencing breakup from on-board stored energy. EVOLVE describes the orbital debris environment by the orbital elements of the objects in the environment. CHAIN is an analytic model that bins the debris environemnt in size and altitude rather than following the orbit evolution of individual debris fragments. The altitude/size bins are coupled by the initial spreading of fragments by collisions and the following orbital decay behavior. A set of test cases covering a variety of space usage scenarios have been defined for the two models. In this paper, a comparison of the results will be presented and sources of disagreement identified and discussed. One major finding is that despite differences in the results of the two models, the basic tendencies of the environment projections are independent of modeled uncertainties, leading to the demand of debris mitigation measures--explosion suppression and de-orbit of rocket bodies and payloads after mission completion.

High Level Architecture Distributed Space System Simulation for Simulation Interoperability Standards Organization Simulation Smackdown

NASA Technical Reports Server (NTRS)

Li, Zuqun

2011-01-01

Modeling and Simulation plays a very important role in mission design. It not only reduces design cost, but also prepares astronauts for their mission tasks. The SISO Smackdown is a simulation event that facilitates modeling and simulation in academia. The scenario of this year s Smackdown was to simulate a lunar base supply mission. The mission objective was to transfer Earth supply cargo to a lunar base supply depot and retrieve He-3 to take back to Earth. Federates for this scenario include the environment federate, Earth-Moon transfer vehicle, lunar shuttle, lunar rover, supply depot, mobile ISRU plant, exploratory hopper, and communication satellite. These federates were built by teams from all around the world, including teams from MIT, JSC, University of Alabama in Huntsville, University of Bordeaux from France, and University of Genoa from Italy. This paper focuses on the lunar shuttle federate, which was programmed by the USRP intern team from NASA JSC. The shuttle was responsible for provide transportation between lunar orbit and the lunar surface. The lunar shuttle federate was built using the NASA standard simulation package called Trick, and it was extended with HLA functions using TrickHLA. HLA functions of the lunar shuttle federate include sending and receiving interaction, publishing and subscribing attributes, and packing and unpacking fixed record data. The dynamics model of the lunar shuttle was modeled with three degrees of freedom, and the state propagation was obeying the law of two body dynamics. The descending trajectory of the lunar shuttle was designed by first defining a unique descending orbit in 2D space, and then defining a unique orbit in 3D space with the assumption of a non-rotating moon. Finally this assumption was taken away to define the initial position of the lunar shuttle so that it will start descending a second after it joins the execution. VPN software from SonicWall was used to connect federates with RTI during testing and the Smackdown event. HLA software from Pitch Technology and MAK Technology were used to edit and extend FOM and provide HLA services for federation execution. The SISO Smackdown event for 2011 was held in Boston, Massachusetts. The federation execution lasted for one hour, and the event was very successful in catching the attention of university students and faculties.

Development of a nanosatellite de-orbiting system by reliability based design optimization

NASA Astrophysics Data System (ADS)

Nikbay, Melike; Acar, Pınar; Aslan, Alim Rüstem

2015-12-01

This paper presents design approaches to develop a reliable and efficient de-orbiting system for the 3USAT nanosatellite to provide a beneficial orbital decay process at the end of a mission. A de-orbiting system is initially designed by employing the aerodynamic drag augmentation principle where the structural constraints of the overall satellite system and the aerodynamic forces are taken into account. Next, an alternative de-orbiting system is designed with new considerations and further optimized using deterministic and reliability based design techniques. For the multi-objective design, the objectives are chosen to maximize the aerodynamic drag force through the maximization of the Kapton surface area while minimizing the de-orbiting system mass. The constraints are related in a deterministic manner to the required deployment force, the height of the solar panel hole and the deployment angle. The length and the number of layers of the deployable Kapton structure are used as optimization variables. In the second stage of this study, uncertainties related to both manufacturing and operating conditions of the deployable structure in space environment are considered. These uncertainties are then incorporated into the design process by using different probabilistic approaches such as Monte Carlo Simulation, the First-Order Reliability Method and the Second-Order Reliability Method. The reliability based design optimization seeks optimal solutions using the former design objectives and constraints with the inclusion of a reliability index. Finally, the de-orbiting system design alternatives generated by different approaches are investigated and the reliability based optimum design is found to yield the best solution since it significantly improves both system reliability and performance requirements.

Reducing orbital eccentricity of precessing black-hole binaries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buonanno, Alessandra; Taracchini, Andrea; Kidder, Lawrence E.

2011-05-15

Building initial conditions for generic binary black-hole evolutions which are not affected by initial spurious eccentricity remains a challenge for numerical-relativity simulations. This problem can be overcome by applying an eccentricity-removal procedure which consists of evolving the binary black hole for a couple of orbits, estimating the resulting eccentricity, and then restarting the simulation with corrected initial conditions. The presence of spins can complicate this procedure. As predicted by post-Newtonian theory, spin-spin interactions and precession prevent the binary from moving along an adiabatic sequence of spherical orbits, inducing oscillations in the radial separation and in the orbital frequency. For single-spinmore » binary black holes these oscillations are a direct consequence of monopole-quadrupole interactions. However, spin-induced oscillations occur at approximately twice the orbital frequency, and therefore can be distinguished and disentangled from the initial spurious eccentricity which occurs at approximately the orbital frequency. Taking this into account, we develop a new eccentricity-removal procedure based on the derivative of the orbital frequency and find that it is rather successful in reducing the eccentricity measured in the orbital frequency to values less than 10{sup -4} when moderate spins are present. We test this new procedure using numerical-relativity simulations of binary black holes with mass ratios 1.5 and 3, spin magnitude 0.5, and various spin orientations. The numerical simulations exhibit spin-induced oscillations in the dynamics at approximately twice the orbital frequency. Oscillations of similar frequency are also visible in the gravitational-wave phase and frequency of the dominant l=2, m=2 mode.« less

Solar and Heliospheric Observatory (SOHO) Flight Dynamics Simulations Using MATLAB (R)

NASA Technical Reports Server (NTRS)

Headrick, R. D.; Rowe, J. N.

1996-01-01

This paper describes a study to verify onboard attitude control laws in the coarse Sun-pointing (CSP) mode by simulation and to develop procedures for operational support for the Solar and Heliospheric Observatory (SOHO) mission. SOHO was launched on December 2, 1995, and the predictions of the simulation were verified with the flight data. This study used a commercial off the shelf product MATLAB(tm) to do the following: Develop procedures for computing the parasitic torques for orbital maneuvers; Simulate onboard attitude control of roll, pitch, and yaw during orbital maneuvers; Develop procedures for predicting firing time for both on- and off-modulated thrusters during orbital maneuvers; Investigate the use of feed forward or pre-bias torques to reduce the attitude handoff during orbit maneuvers - in particular, determine how to use the flight data to improve the feed forward torque estimates for use on future maneuvers. The study verified the stability of the attitude control during orbital maneuvers and the proposed use of feed forward torques to compensate for the attitude handoff. Comparison of the simulations with flight data showed: Parasitic torques provided a good estimate of the on- and off-modulation for attitude control; The feed forward torque compensation scheme worked well to reduce attitude handoff during the orbital maneuvers. The work has been extended to prototype calibration of thrusters from observed firing time and observed reaction wheel speed changes.

Modelling and simulation of Space Station Freedom berthing dynamics and control

NASA Technical Reports Server (NTRS)

Cooper, Paul A.; Garrison, James L., Jr.; Montgomery, Raymond C.; Wu, Shih-Chin; Stockwell, Alan E.; Demeo, Martha E.

1994-01-01

A large-angle, flexible, multibody, dynamic modeling capability has been developed to help validate numerical simulations of the dynamic motion and control forces which occur during berthing of Space Station Freedom to the Shuttle Orbiter in the early assembly flights. This paper outlines the dynamics and control of the station, the attached Shuttle Remote Manipulator System, and the orbiter. The simulation tool developed for the analysis is described and the results of two simulations are presented. The first is a simulated maneuver from a gravity-gradient attitude to a torque equilibrium attitude using the station reaction control jets. The second simulation is the berthing of the station to the orbiter with the station control moment gyros actively maintaining an estimated torque equilibrium attitude. The influence of the elastic dynamic behavior of the station and of the Remote Manipulator System on the attitude control of the station/orbiter system during each maneuver was investigated. The flexibility of the station and the arm were found to have only a minor influence on the attitude control of the system during the maneuvers.

Landsat-7 Simulation and Testing Environments

NASA Technical Reports Server (NTRS)

Holmes, E.; Ha, K.; Hawkins, K.; Lombardo, J.; Ram, M.; Sabelhaus, P.; Scott, S.; Phillips, R.

1999-01-01

A spacecraft Attitude Control and Determination Subsystem (ACDS) is heavily dependent upon simulation throughout its entire development, implementation and ground test cycle. Engineering simulation tools are typically developed to design and analyze control systems to validate the design and software simulation tools are required to qualify the flight software. However, the need for simulation does not end here. Operating the ACDS of a spacecraft on the ground requires the simulation of spacecraft dynamics, disturbance modeling and celestial body motion. Sensor data must also be simulated and substituted for actual sensor data on the ground so that the spacecraft will respond by sending commands to the actuators as they will on orbit. And finally, the simulators is the primary training tool and test-bed for the Flight Operations Team. In this paper various ACDS simulation, developed for or used by the Landsat 7 project will be described. The paper will include a description of each tool, its unique attributes, and its role in the overall development and testing of the ACDS. Finally, a section is included which discusses how the coordinated use of these simulation tools can maximize the probability of uncovering software, hardware and operations errors during the ground test process.

An innovative exercise method to simulate orbital EVA work - Applications to PLSS automatic controls

NASA Technical Reports Server (NTRS)

Lantz, Renee; Vykukal, H.; Webbon, Bruce

1987-01-01

An exercise method has been proposed which may satisfy the current need for a laboratory simulation representative of muscular, cardiovascular, respiratory, and thermoregulatory responses to work during orbital extravehicular activity (EVA). The simulation incorporates arm crank ergometry with a unique body support mechanism that allows all body position stabilization forces to be reacted at the feet. By instituting this exercise method in laboratory experimentation, an advanced portable life support system (PLSS) thermoregulatory control system can be designed to more accurately reflect the specific work requirements of orbital EVA.

Thermal environments for Space Shuttle payloads

NASA Technical Reports Server (NTRS)

Fu, J. H.; Graves, G. R.

1985-01-01

The thermal environment of the Space Shuttle payload bay during the on-orbit phase of the STS flights is presented. The STS Thermal Flight Instrumentation System and various substructures of the Orbiter and the payload are described, as well as the various on-orbit attitudes encountered in the STS flights (the tail to sun, nose to sun, payload bay to sun, etc.). Included are the temperature profiles obtained during the on-orbit STS 1-5 flights (with the payload bay door open), recorded in various substructures of the Orbiter's midsection at different flight attitudes, as well as schematic illustrations of the Space Shuttle system, a typical mission profile, and the Orbiter's substructures.

LightForce Photon-pressure Collision Avoidance: Efficiency Analysis in the Current Debris Environment and Long-Term Simulation Perspective

NASA Technical Reports Server (NTRS)

Yang, Fan Y.; Nelson, Bron; Carlino, Roberto; Perez, Andres D.; Faber, Nicolas; Henze, Chris; Karacahoglu, Arif G.; O'Toole, Conor; Swenson, Jason; Stupl, Jan

2015-01-01

This work provides an efficiency analysis of the LightForce space debris collision avoidance scheme in the current debris environment and describes a simulation approach to assess its impact on the long-term evolution of the space debris environment. LightForce aims to provide just-in-time collision avoidance by utilizing photon pressure from ground-based industrial lasers. These ground stations impart minimal accelerations to increase the miss distance for a predicted conjunction between two objects. In the first part of this paper we will present research that investigates the short-term effect of a few systems consisting of 10kW class lasers directed by 1.5 m diameter telescopes using adaptive optics. The results found such a network of ground stations to mitigate more than 85 percent of conjunctions and could lower the expected number of collisions in Low Earth Orbit (LEO) by an order of magnitude. While these are impressive numbers that indicate LightForce's utility in the short-term, the remaining 15 percent of possible collisions contain (among others) conjunctions between two massive objects that would add large amount of debris if they collide. Still, conjunctions between massive objects and smaller objects can be mitigated. Hence we choose to expand the capabilities of the simulation software to investigate the overall effect of a network of LightForce stations on the long-term debris evolution. In the second part of this paper, we will present the planed simulation approach for that effort.

STS-1 mission contamination evaluation approach

NASA Technical Reports Server (NTRS)

Jacobs, S.; Ehlers, H.; Miller, E. R.

1980-01-01

The space transportation system 1 mission will be the first opportunity to assess the induced environment of the orbiter payload bay region. Two tools were developed to aid in this assessment. The shuttle payload contamination evaluation computer program was developed to provide an analytical tool for prediction of the induced molecular contamination environment of the space shuttle orbiter during its onorbit operations. An induced environment contamination monitor was constructed and tested to measure the space shuttle orbiter contamination environment inside the payload bay during ascent and descent and inside and outside the payload bay during the onorbit phase. Measurements are to be performed during the four orbital flight test series. Measurements planned for the first flight are described and predicted environmental data are discussed. The results indicate that the expected data are within the measurement range of the induced environment contamination monitor instruments evaluated, and therefore it is expected that useful contamination environmental data will be available after the first flight.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trippe, J. M.; Reed, R. A.; Austin, R. A.

In this study, we present experimental evidence of single electron-induced upsets in commercial 28 nm and 45 nm CMOS SRAMs from a monoenergetic electron beam. Upsets were observed in both technology nodes when the SRAM was operated in a low power state. The experimental cross section depends strongly on both bias and technology node feature size, consistent with previous work in which SRAMs were irradiated with low energy muons and protons. Accompanying simulations demonstrate that δ-rays produced by the primary electrons are responsible for the observed upsets. Additional simulations predict the on-orbit event rates for various Earth and Jovian environmentsmore » for a set of sensitive volumes representative of current technology nodes. The electron contribution to the total upset rate for Earth environments is significant for critical charges as high as 0.2 fC. This value is comparable to that of sub-22 nm bulk SRAMs. Similarly, for the Jovian environment, the electron-induced upset rate is larger than the proton-induced upset rate for critical charges as high as 0.3 fC.« less

Radiation-induced rotation of small celestial bodies

NASA Technical Reports Server (NTRS)

Misconi, N. Y.; Oliver, John; Mzariegos, Roberto

1992-01-01

The rotation was studied of particles in a simulated space environment via a technique known as Laser Particle Levitation. The combination of both a high vacuum and optical laser levitation to negate the effects of Earth's gravity, simulate the space environment. The rotation mechanism under study is known as the 'Windmill Effect,' which is a spin mechanism that suggests that the interaction of the photon field from a star with the surface irregularities of cosmic dust will cause them to spin due to the imbalance in the directionality of the scattered photons which necessitates a non-zero angular momentum. This conclusion is based on the random nature of the orientation of the sites of surface irregularities. The general object is to study the behavior of particles in orbits around the Earth, both natural and man made, as well as interplanetary and circumstellar particles. To meet this objective, an apparatus was constructed which was designed to allow optical levitation in a vacuum.

Star tracker operation in a high density proton field

NASA Technical Reports Server (NTRS)

Miklus, Kenneth J.; Kissh, Frank; Flynn, David J.

1993-01-01

Algorithms that reject transient signals due to proton effects on charge coupled device (CCD) sensors have been implemented in the HDOS ASTRA-l Star Trackers to be flown on the TOPEX mission scheduled for launch in July 1992. A unique technique for simulating a proton-rich environment to test trackers is described, as well as the test results obtained. Solar flares or an orbit that passes through the South Atlantic Anomaly can subject the vehicle to very high proton flux levels. There are three ways in which spurious proton generated signals can impact tracker performance: the many false signals can prevent or extend the time to acquire a star; a proton-generated signal can compromise the accuracy of the star's reported magnitude and position; and the tracked star can be lost, requiring reacquisition. Tests simulating a proton-rich environment were performed on two ASTRA-1 Star Trackers utilizing these new algorithms. There were no false acquisitions, no lost stars, and a significant reduction in reported position errors due to these improvements.

Observational Constraints on the Orbit and Location of Planet Nine in the Outer Solar System

NASA Astrophysics Data System (ADS)

Brown, Michael E.; Batygin, Konstantin

2016-06-01

We use an extensive suite of numerical simulations to constrain the mass and orbit of Planet Nine, the recently proposed perturber in a distant eccentric orbit in the outer solar system. We compare our simulations to the observed population of aligned eccentric high semimajor axis Kuiper belt objects (KBOs) and determine which simulation parameters are statistically compatible with the observations. We find that only a narrow range of orbital elements can reproduce the observations. In particular, the combination of semimajor axis, eccentricity, and mass of Planet Nine strongly dictates the semimajor axis range of the orbital confinement of the distant eccentric KBOs. Allowed orbits, which confine KBOs with semimajor axis beyond 380 au, have perihelia roughly between 150 and 350 au, semimajor axes between 380 and 980 au, and masses between 5 and 20 Earth masses. Orbitally confined objects also generally have orbital planes similar to that of the planet, suggesting that the planet is inclined approximately 30°to the ecliptic. We compare the allowed orbital positions and estimated brightness of Planet Nine to previous and ongoing surveys which would be sensitive to the planet’s detection and use these surveys to rule out approximately two-thirds of the planet’s orbit. Planet Nine is likely near aphelion with an approximate brightness of 22< V< 25. At opposition, its motion, mainly due to parallax, can easily be detected within 24 hours.

Correlation of Amine Swingbed On-Orbit CO2 Performance with a Hardware Independent Predictive Model

NASA Technical Reports Server (NTRS)

Papale, William; Sweterlitsch, Jeffery

2015-01-01

The Amine Swingbed Payload is an experimental system deployed on the International Space Station (ISS) that includes a two-bed, vacuum regenerated, amine-based carbon dioxide (CO2) removal subsystem as the principal item under investigation. The aminebased subsystem, also described previously in various publications as CAMRAS 3, was originally designed, fabricated and tested by Hamilton Sundstrand Space Systems International, Inc. (HSSSI) and delivered to NASA in November 2008. The CAMRAS 3 unit was subsequently designed into a flight payload experiment in 2010 and 2011, with flight test integration activities accomplished on-orbit between January 2012 and March 2013. Payload activation was accomplished in May 2013 followed by a 1000 hour experimental period. The experimental nature of the Payload and the interaction with the dynamic ISS environment present unique scientific and engineering challenges, in particular to the verification and validation of the expected Payload CO2 removal performance. A modeling and simulation approach that incorporates principles of chemical reaction engineering has been developed for the amine-based system to predict the dynamic cabin CO2 partial pressure with given inputs of sorbent bed size, process air flow, operating temperature, half-cycle time, CO2 generation rate, cabin volume and the magnitude of vacuum available. Simulation runs using the model to predict ambient CO2 concentrations show good correlation to on-orbit performance measurements and ISS dynamic concentrations for the assumed operating conditions. The dynamic predictive modelling could benefit operational planning to help ensure ISS CO2 concentrations are maintained below prescribed limits and for the Orion vehicle to simulate various operating conditions, scenarios and transients.

Use of Human Modeling Simulation Software in the Task Analysis of the Environmental Control and Life Support System Component Installation Procedures

NASA Technical Reports Server (NTRS)

Estes, Samantha; Parker, Nelson C. (Technical Monitor)

2001-01-01

Virtual reality and simulation applications are becoming widespread in human task analysis. These programs have many benefits for the Human Factors Engineering field. Not only do creating and using virtual environments for human engineering analyses save money and time, this approach also promotes user experimentation and provides increased quality of analyses. This paper explains the human engineering task analysis performed on the Environmental Control and Life Support System (ECLSS) space station rack and its Distillation Assembly (DA) subsystem using EAI's human modeling simulation software, Jack. When installed on the International Space Station (ISS), ECLSS will provide the life and environment support needed to adequately sustain crew life. The DA is an Orbital Replaceable Unit (ORU) that provides means of wastewater (primarily urine from flight crew and experimental animals) reclamation. Jack was used to create a model of the weightless environment of the ISS Node 3, where the ECLSS is housed. Computer aided drawings of the ECLSS rack and DA system were also brought into the environment. Anthropometric models of a 95th percentile male and 5th percentile female were used to examine the human interfaces encountered during various ECLSS and DA tasks. The results of the task analyses were used in suggesting modifications to hardware and crew task procedures to improve accessibility, conserve crew time, and add convenience for the crew. This paper will address some of those suggested modifications and the method of presenting final analyses for requirements verification.

The Threatening Magnetic and Plasma Environment of the TRAPPIST-1 Planets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garraffo, Cecilia; Drake, Jeremy J.; Cohen, Ofer

2017-07-10

Recently, four additional Earth-mass planets were discovered orbiting the nearby ultracool M8 dwarf, TRAPPIST-1, making a remarkable total of seven planets with equilibrium temperatures compatible with the presence of liquid water on their surface. Temperate terrestrial planets around an M-dwarf orbit close to their parent star, rendering their atmospheres vulnerable to erosion by the stellar wind and energetic electromagnetic and particle radiation. Here, we use state-of-the-art 3D magnetohydrodynamic models to simulate the wind around TRAPPIST-1 and study the conditions at each planetary orbit. All planets experience a stellar wind pressure between 10{sup 3} and 10{sup 5} times the solar windmore » pressure on Earth. All orbits pass through wind pressure changes of an order of magnitude and most planets spend a large fraction of their orbital period in the sub-Alfvénic regime. For plausible planetary magnetic field strengths, all magnetospheres are greatly compressed and undergo much more dynamic change than that of the Earth. The planetary magnetic fields connect with the stellar radial field over much of the planetary surface, allowing the direct flow of stellar wind particles onto the planetary atmosphere. These conditions could result in strong atmospheric stripping and evaporation and should be taken into account for any realistic assessment of the evolution and habitability of the TRAPPIST-1 planets.« less

End-To-End Simulation of Launch Vehicle Trajectories Including Stage Separation Dynamics

NASA Technical Reports Server (NTRS)

Albertson, Cindy W.; Tartabini, Paul V.; Pamadi, Bandu N.

2012-01-01

The development of methodologies, techniques, and tools for analysis and simulation of stage separation dynamics is critically needed for successful design and operation of multistage reusable launch vehicles. As a part of this activity, the Constraint Force Equation (CFE) methodology was developed and implemented in the Program to Optimize Simulated Trajectories II (POST2). The objective of this paper is to demonstrate the capability of POST2/CFE to simulate a complete end-to-end mission. The vehicle configuration selected was the Two-Stage-To-Orbit (TSTO) Langley Glide Back Booster (LGBB) bimese configuration, an in-house concept consisting of a reusable booster and an orbiter having identical outer mold lines. The proximity and isolated aerodynamic databases used for the simulation were assembled using wind-tunnel test data for this vehicle. POST2/CFE simulation results are presented for the entire mission, from lift-off, through stage separation, orbiter ascent to orbit, and booster glide back to the launch site. Additionally, POST2/CFE stage separation simulation results are compared with results from industry standard commercial software used for solving dynamics problems involving multiple bodies connected by joints.

ESTL tracking and data relay satellite /TDRSS/ simulation system

NASA Technical Reports Server (NTRS)

Kapell, M. H.

1980-01-01

The Tracking Data Relay Satellite System (TDRSS) provides single access forward and return communication links with the Shuttle/Orbiter via S-band and Ku-band frequency bands. The ESTL (Electronic Systems Test Laboratory) at Lyndon B. Johnson Space Center (JSC) utilizes a TDRS satellite simulator and critical TDRS ground hardware for test operations. To accomplish Orbiter/TDRSS relay communications performance testing in the ESTL, a satellite simulator was developed which met the specification requirements of the TDRSS channels utilized by the Orbiter. Actual TDRSS ground hardware unique to the Orbiter communication interfaces was procured from individual vendors, integrated in the ESTL, and interfaced via a data bus for control and status monitoring. This paper discusses the satellite simulation hardware in terms of early development and subsequent modifications. The TDRS ground hardware configuration and the complex computer interface requirements are reviewed. Also, special test hardware such as a radio frequency interference test generator is discussed.

Numerical simulations of particle orbits around 2060 Chiron

NASA Technical Reports Server (NTRS)

Stern, S. A.; Jackson, A. A.; Boice, D. C.

1994-01-01

Scattered light from orbiting or coorbiting dust is a primary signature by which Earth-based observers study the activity and atmosphere of the unusual outer solar system object 2060 Chiron. Therefore, it is important to understand the lifetime, dynamics, and loss rates of dust in its coma. We report here dynamical simulations of particles in Chiron's collisionless coma. The orbits of 17,920 dust particles were numerically integrated under the gravitational influence of Chiron, the Sun, and solar radiation pressure. These simulations show that particles ejected from Chiron are more likely to follow suborbital trajectories, or to escape altogether, than to enter quasistable orbits. Significant orbital lifetimes can only be achieved for very specific launch conditions. These results call into question models of a long-term, bound coma generated by discrete outbursts, and instead suggest that Chiron's coma state is closely coupled to the nearly instantaneous level of Chiron's surface activity.

Natural environment design requirements for the space tug

NASA Technical Reports Server (NTRS)

West, G. S., Jr.

1973-01-01

The natural environment design requirements for the space tug are presented. Since the Space Tug is carried as cargo to orbital altitudes in the space shuttle bay, orbital environmental impacts and short-period atmospheric density variations are the main concerns. The subjects discussed are: (1) natural environment, (2) neutral environment, (3) charged particles, (4) radiation, and (5) meteoroid hazards.

Harnessing Adaptive Optics for Space Debris Collision Mitigation

NASA Astrophysics Data System (ADS)

Zovaro, A.; Bennet, F.; Copeland, M.; Rigaut, F.; d'Orgeville, C.; Grosse, D.

2016-09-01

Human kind's continued use of space depends upon minimising the build-up of debris in low Earth-orbit (LEO). Preventing collisions between satellites and debris is essential given that a single collision can generate thousands of new debris objects. However, in-orbit manoeuvring of satellites is extremely expensive and shortens their operational life. Adjusting the orbits of debris objects instead of satellites would shift the responsibility of collision avoidance away from satellite operators altogether, thereby offering a superior solution. The Research School of Astronomy and Astrophysics at the Australian National University, partnered with Electro Optic Systems (EOS) Space Systems, Lockheed Martin Corporation and the Space Environment Research Centre (SERC) Limited, are developing the Adaptive Optics Tracking and Pushing (AOTP) system. AOTP will be used to perturb the orbits of debris objects using photon pressure from a 10 kW IR laser beam launched from the 1.8 m telescope at Mount. Stromlo Observatory, Australia. Initial simulations predict that AOTP will be able to displace debris objects 10 cm in size by up to 100 m with several overhead passes. An operational demonstrator is planned for 2019. Turbulence will distort the laser beam as it propagates through the atmosphere, resulting in a lower photon flux on the target and reduced pointing accuracy. To mitigate these effects, adaptive optics (AO) will be used to apply wavefront correction to the beam prior to launch. A unique challenge in designing the AO system arises from the high slew rate needed to track objects in LEO, which in turn requires laser guide star AO for satisfactory wavefront correction. The optical design and results from simulations of estimated performance of AOTP will be presented. In particular, design considerations associated with the high-power laser will be detailed.

The Space Shuttle Orbiter molecular environment induced by the supplemental flash evaporator system

NASA Technical Reports Server (NTRS)

Ehlers, H. K. F.

1985-01-01

The water vapor environment of the Space Shuttle Orbiter induced by the supplemental flash evaporator during the on-orbit flight phase has been analyzed based on Space II model predictions and orbital flight measurements. Model data of local density, column density, and return flux are presented. Results of return flux measurements with a mass spectrometer during STS-2 and of direct flux measurements during STS-4 are discussed and compared with model predictions.

System Engineering Issues for Avionics Survival in the Space Environment

NASA Technical Reports Server (NTRS)

Pavelitz, Steven

1999-01-01

This paper examines how the system engineering process influences the design of a spacecraft's avionics by considering the space environment. Avionics are susceptible to the thermal, radiation, plasma, and meteoroids/orbital debris environments. The environment definitions for various spacecraft mission orbits (LEO/low inclination, LEO/Polar, MEO, HEO, GTO, GEO and High ApogeeElliptical) are discussed. NASA models and commercial software used for environment analysis are reviewed. Applicability of technical references, such as NASA TM-4527 "Natural Orbital Environment Guidelines for Use in Aerospace Vehicle Development" is discussed. System engineering references, such as the MSFC System Engineering Handbook, are reviewed to determine how the environments are accounted for in the system engineering process. Tools and databases to assist the system engineer and avionics designer in addressing space environment effects on avionics are described and usefulness assessed.

A simulation study of emergency lunar escape to orbit using several simplified manual guidance and control techniques

NASA Technical Reports Server (NTRS)

Middleton, D. B.; Hurt, G. J., Jr.

1971-01-01

A fixed-base piloted simulator investigation has been made of the feasibility of using any of several manual guidance and control techniques for emergency lunar escape to orbit with very simplified, lightweight vehicle systems. The escape-to-orbit vehicles accommodate two men, but one man performs all of the guidance and control functions. Three basic attitude-control modes and four manually executed trajectory-guidance schemes were used successfully during approximately 125 simulated flights under a variety of conditions. These conditions included thrust misalinement, uneven propellant drain, and a vehicle moment-of-inertia range of 250 to 12,000 slugs per square foot. Two types of results are presented - orbit characteristics and pilot ratings of vehicle handling qualities.

Debris Albedo from Laser Ablation in Low and High Vacuum: Comparisons to Hypervelocity Impact

NASA Astrophysics Data System (ADS)

Radhakrishnan, G.; Adams, P. M.; Alaan, D. R.; Panetta, C. J.

The albedo of orbital debris fragments in space is a critical parameter used in the derivation of their physical sizes from optical measurements. The change in albedo results from scattering due to micron and sub-micron particles on the surface. There are however no known hypervelocity collision ground tests that simulate the high-vacuum conditions on-orbit. While hypervelocity impact experiments at a gun range can offer a realistic representation of the energy of impact and fragmentation, and can aid the understanding of albedo, they are conducted in low-pressure air that is not representative of the very high vacuum of 10-8 Torr or less that exists in the Low Earth Orbit environment. Laboratory simulation using laser ablation with a high power laser, on the same target materials as used in current satellite structures, is appealing because it allows for well-controlled investigations that can be coupled to optical albedo (reflectance) measurements of the resultant debris. This relatively low-cost laboratory approach can complement the significantly more elaborate and expensive field-testing of single-shot hypervelocity impact on representative satellite structures. Debris generated is optically characterized with UV-VIS-NIR reflectance, and particle size distributions can be measured. In-situ spectroscopic diagnostics (nanosecond time frame) provide an identification of atoms and ions in the plume, and plasma temperatures, allowing a correlation of the energetics of the ablated plume with resulting albedo and particle size distributions of ablated debris. Our laboratory experiments offer both a high-vacuum environment, and selection of any gaseous ambient, at any controlled pressure, thus allowing for comparison to the hypervelocity impact experiments in low-pressure air. Initial results from plume analysis, and size distribution and microstructure of debris collected on witness plates show that laser ablations in low-pressure air offer many similarities to the recent DebrisLV and DebriSat hypervelocity impact experiments, while ablations in high-vacuum provide critical distinctions.

Predicting Instability Timescales in Closely-Packed Planetary Systems

NASA Astrophysics Data System (ADS)

Tamayo, Daniel; Hadden, Samuel; Hussain, Naireen; Silburt, Ari; Gilbertson, Christian; Rein, Hanno; Menou, Kristen

2018-04-01

Many of the multi-planet systems discovered around other stars are maximally packed. This implies that simulations with masses or orbital parameters too far from the actual values will destabilize on short timescales; thus, long-term dynamics allows one to constrain the orbital architectures of many closely packed multi-planet systems. A central challenge in such efforts is the large computational cost of N-body simulations, which preclude a full survey of the high-dimensional parameter space of orbital architectures allowed by observations. I will present our recent successes in training machine learning models capable of reliably predicting orbital stability a million times faster than N-body simulations. By engineering dynamically relevant features that we feed to a gradient-boosted decision tree algorithm (XGBoost), we are able to achieve a precision and recall of 90% on a holdout test set of N-body simulations. This opens a wide discovery space for characterizing new exoplanet discoveries and for elucidating how orbital architectures evolve through time as the next generation of spaceborne exoplanet surveys prepare for launch this year.

Description of the plasma diagnostics package (PDP) for the OSS-1 Shuttle mission and JSC plasma chamber test in conjunction with the fast pulse electron gun (FPEG)

NASA Technical Reports Server (NTRS)

Shawhan, S. D.

1982-01-01

The objectives, equipment, and techniques for the plasma diagnostics package (PDP) carried by the OSS-1 instrument payload of the STS-4 and scheduled for the Spacelab-2 mission are described. The goals of the first flight were to examine the Orbiter-magnetoplasma interactions by measuring the electric and magnetic field strengths, the ionized particle wakes, and the generated waves. The RMS was employed to lift the unit out of the bay in order to allow characterization of the fields, EM interference, and plasma contamination within 15 m of the Orbiter. The PDP will also be used to examine plasma depletion, chemical reaction rates, waves, and energized plasma produced by firing of the Orbiter thrusters. Operation of the PDP was carried out in the NASA Space Environment Simulation Laboratory test chamber, where the PDP was used to assay the fields, fluxes, wave amplitudes, and particle energy spectra. The PDP instrumentation is also capable of detecting thermal ions, thermal electrons suprathermal particles, VHF/UHF EMI levels, and the S-band field strength.

Shuttle antenna radome technology test program. Volume 2: Development of S-band antenna interface design

NASA Technical Reports Server (NTRS)

Kuhlman, E. A.; Baranowski, L. C.

1977-01-01

The effects of the Thermal Protection Subsystem (TPS) contamination on the space shuttle orbiter S band quad antenna due to multiple mission buildup are discussed. A test fixture was designed, fabricated and exposed to ten cycles of simulated ground and flight environments. Radiation pattern and impedance tests were performed to measure the effects of the contaminates. The degradation in antenna performance was attributed to the silicone waterproofing in the TPS tiles rather than exposure to the contaminating sources used in the test program. Validation of the accuracy of an analytical thermal model is discussed. Thermal vacuum tests with a test fixture and a representative S band quad antenna were conducted to evaluate the predictions of the analytical thermal model for two orbital heating conditions and entry from each orbit. The results show that the accuracy of predicting the test fixture thermal responses is largely dependent on the ability to define the boundary and ambient conditions. When the test conditions were accurately included in the analytical model, the predictions were in excellent agreement with measurements.

Ground test challenges in the development of the Space Shuttle orbiter auxiliary power unit

NASA Technical Reports Server (NTRS)

Chaffee, N. H.; Lance, R. J.; Weary, D. P.

1984-01-01

A conventional aircraft hydraulic system design approach was selected to provide fluid power for the Space Shuttle Orbiter. Developing the power unit, known as the Auxiliary Power Unit (APU), to drive the hydraulic pumps presented a major technological challenge. A small, high speed turbine drive unit powered by catalytically decomposed hydrazine and operating in the pulse mode was selected to meet the requirement. Because of limitations of vendor test facilities, significant portions of the development, flight qualification, and postflight anomaly testing of the Orbiter APU were accomplished at the Johnson Space Center (JSC) test facilities. This paper discusses the unique requirements of attitude, gravity forces, pressure profiles, and thermal environments which had to be satisfied by the APU, and presents the unique test facility and simulation techniques employed to meet the ground test requirements. In particular, the development of the zero-g lubrication system, the development of necessary APU thermal control techniques, the accomplishment of integrated systems tests, and the postflight investigation of the APU lube oil cooler behavior are discussed.

Simulating The Dynamical Evolution Of Galaxies In Group And Cluster Environments

NASA Astrophysics Data System (ADS)

Vijayaraghavan, Rukmani

2015-07-01

Galaxy clusters are harsh environments for their constituent galaxies. A variety of physical processes effective in these dense environments transform gas-rich, spiral, star-forming galaxies to elliptical or spheroidal galaxies with very little gas and therefore minimal star formation. The consequences of these processes are well understood observationally. Galaxies in progressively denser environments have systematically declining star formation rates and gas content. However, a theoretical understanding of of where, when, and how these processes act, and the interplay between the various galaxy transformation mechanisms in clusters remains elusive. In this dissertation, I use numerical simulations of cluster mergers as well as galaxies evolving in quiescent environments to develop a theoretical framework to understand some of the physics of galaxy transformation in cluster environments. Galaxies can be transformed in smaller groups before they are accreted by their eventual massive cluster environments, an effect termed `pre-processing'. Galaxy cluster mergers themselves can accelerate many galaxy transformation mechanisms, including tidal and ram pressure stripping of galaxies and galaxy-galaxy collisions and mergers that result in reassemblies of galaxies' stars and gas. Observationally, cluster mergers have distinct velocity and phase-space signatures depending on the observer's line of sight with respect to the merger direction. Using dark matter only as well as hydrodynamic simulations of cluster mergers with random ensembles of particles tagged with galaxy models, I quantify the effects of cluster mergers on galaxy evolution before, during, and after the mergers. Based on my theoretical predictions of the dynamical signatures of these mergers in combination with galaxy transformation signatures, one can observationally identify remnants of mergers and quantify the effect of the environment on galaxies in dense group and cluster environments. The presence of long-lived, hot X-ray emitting coronae observed in a large fraction of group and cluster galaxies is not well-understood. These coronae are not fully stripped by ram pressure and tidal forces that are efficient in these environments. Theoretically, this is a fascinating and challenging problem that involves understanding and simulating the multitude of physical processes in these dense environments that can remove or replenish galaxies' hot coronae. To solve this problem, I have developed and implemented a robust simulation technique where I simulate the evolution of a realistic cluster environment with a population of galaxies and their gas. With this technique, it is possible to isolate and quantify the importance of the various cluster physical processes for coronal survival. To date, I have performed hydrodynamic simulations of galaxies being ram pressure stripped in quiescent group and cluster environments. Using these simulations, I have characterized the physics of ram pressure stripping and investigated the survival of these coronae in the presence of tidal and ram pressure stripping. I have also generated synthetic X-ray observations of these simulated systems to compare with observed coronae. I have also performed magnetohydrodynamic simulations of galaxies evolving in a magnetized intracluster medium plasma to isolate the effect of magnetic fields on coronal evolution, as well the effect of orbiting galaxies in amplifying magnetic fields. This work is an important step towards understanding the effect of cluster environments on galactic gas, and consequently, their long term evolution and impact on star formation rates.

KENNEDY SPACE CENTER, FLA. - Emergency crew members on the ground take hold of a volunteer “astronaut” lowered from the top of the orbiter crew compartment mock-up that is the scene of a “Mode VII” emergency landing simulation at Kennedy Space Center. The purpose of the Mode VII is to exercise emergency preparedness personnel, equipment and facilities in rescuing astronauts from a downed orbiter and providing immediate medical attention. This simulation presents an orbiter that has crashed short of the Shuttle Landing Facility in a wooded area 2-1/2 miles south of Runway 33. Emergency crews are responding to the volunteer astronauts who are simulating various injuries. Rescuers must remove the crew, provide triage and transport to hospitals those who need further treatment. Local hospitals are participating in the exercise.

NASA Image and Video Library

2004-02-18

KENNEDY SPACE CENTER, FLA. - Emergency crew members on the ground take hold of a volunteer “astronaut” lowered from the top of the orbiter crew compartment mock-up that is the scene of a “Mode VII” emergency landing simulation at Kennedy Space Center. The purpose of the Mode VII is to exercise emergency preparedness personnel, equipment and facilities in rescuing astronauts from a downed orbiter and providing immediate medical attention. This simulation presents an orbiter that has crashed short of the Shuttle Landing Facility in a wooded area 2-1/2 miles south of Runway 33. Emergency crews are responding to the volunteer astronauts who are simulating various injuries. Rescuers must remove the crew, provide triage and transport to hospitals those who need further treatment. Local hospitals are participating in the exercise.

KENNEDY SPACE CENTER, FLA. - Emergency crew members help a volunteer “astronaut” onto the ground after being lowered from the top of the orbiter crew compartment mock-up that is the scene of a “Mode VII” emergency landing simulation at Kennedy Space Center. The purpose of the Mode VII is to exercise emergency preparedness personnel, equipment and facilities in rescuing astronauts from a downed orbiter and providing immediate medical attention. This simulation presents an orbiter that has crashed short of the Shuttle Landing Facility in a wooded area 2-1/2 miles south of Runway 33. Emergency crews are responding to the volunteer astronauts who are simulating various injuries. Rescuers must remove the crew, provide triage and transport to hospitals those who need further treatment. Local hospitals are participating in the exercise.

NASA Image and Video Library

2004-02-18

KENNEDY SPACE CENTER, FLA. - Emergency crew members help a volunteer “astronaut” onto the ground after being lowered from the top of the orbiter crew compartment mock-up that is the scene of a “Mode VII” emergency landing simulation at Kennedy Space Center. The purpose of the Mode VII is to exercise emergency preparedness personnel, equipment and facilities in rescuing astronauts from a downed orbiter and providing immediate medical attention. This simulation presents an orbiter that has crashed short of the Shuttle Landing Facility in a wooded area 2-1/2 miles south of Runway 33. Emergency crews are responding to the volunteer astronauts who are simulating various injuries. Rescuers must remove the crew, provide triage and transport to hospitals those who need further treatment. Local hospitals are participating in the exercise.

A Geostationary Earth Orbit Satellite Model Using Easy Java Simulation

ERIC Educational Resources Information Center

Wee, Loo Kang; Goh, Giam Hwee

2013-01-01

We develop an Easy Java Simulation (EJS) model for students to visualize geostationary orbits near Earth, modelled using a Java 3D implementation of the EJS 3D library. The simplified physics model is described and simulated using a simple constant angular velocity equation. We discuss four computer model design ideas: (1) a simple and realistic…

Detecting a Subsurface Ocean From Periodic Orbits at Enceladus

NASA Astrophysics Data System (ADS)

Casotto, S.; Padovan, S.; Russell, R. P.; Lara, M.

2008-12-01

Enceladus is a small icy satellite of Saturn which has been observed by the Cassini orbiter to eject plumes mainly consisting of water vapor from the "tiger stripes" located near its South pole. While tidal heating has been ruled out as an inadequate energy source to drive these eruptions, tidally induced shear stress both along and across the stripes appears to be sufficiently powerful. The internal constitution of Enceladus that fits this model is likely to entail a thin crust and a subcrustal water layer above an undifferentiated interior. Apart from the lack of a core/mantle boundary, the situation is similar to the current hypothetical models of Europa's interior. The determination of the existence of a subsurface fluid layer can therefore be pursued with similar methods, including the study of the gravitational perturbations of tidal origin on an Enceladus orbiter, and the use of altimeter measurements to the tidally deformed surface. The dynamical environment of an Enceladus orbiter is made very unstable by the overwhelming presence of nearby Saturn. The Enceladus sphere of influence is roughly twice its radius. This makes it considerably more difficult to orbit than Europa, whose sphere of influence is ~six times its radius. While low-altitude, near-polar Enceladus orbits suffer extreme instability, recent works have extended the inclination envelope for long-term stable orbits at Enceladus. Several independent methods suggest that ~65 degrees inclination is the maximum attainable for stable, perturbed Keplerian motion. These orbits are non-circular and exist with altitude variations from ~200 to ~300 km. We propose a nominal reference orbit that enjoys long term stability and is favorable for long-term mapping and other scientific experiments. A brief excursion to a lower altitude, slightly higher inclined, yet highly unstable orbit is proposed to improve gravity signatures and enable high resolution, nadir-pointing experiments on the geysers emanating from the tiger- stripes. Near-circular, low altitude highly inclined orbits with arbitrary initial conditions will impact Enceladus if uncontrolled in about 1 to 2 days. To reduce risk and station-keeping requirements we choose periodic orbits in the Hill's plus non-spherical Enceladus model. Despite the instability, the repeat ground track solutions represent equilibria in the dominant terms of the dynamics and therefore extend the uncontrolled lifetimes to ~7 to ~10 days. Round-trip transfers between the two orbital phases is expected to conservatively cost between ~50 and ~100 m/s. We use orbits of different altitudes and inclinations to simulate Earth-based ranging to the orbiter and altimeter measurements to the surface of Enceladus. The simulations are made assuming different tidal responses by adopting different values of the Love numbers. The synthetic measurements are then inverted and the tidal parameters h2 and k2 estimated. Results will be presented in terms of sensitivity of detection of Love numbers to the different orbital geometries. Indications will thus be provided for optimized orbit planning of future exploration missions aimed at investigating the internal structure of the satellite and the detection of its putative subcrustal ocean.

Orbiter aborts from boost: Presimulation report

NASA Technical Reports Server (NTRS)

Backman, H. D.; Brechka, K. G.

1972-01-01

A description of a hybrid simulation of the 040C orbiter aborting from boost to specified landing site is provided. The simulation starts when the abort is initiated and continues until a terminal energy state (associated with the selected landing site) is reached. At abort it is assumed that all SRM's are jettisoned with the external tank remaining with the orbiter. The simulation described has six degrees of freedom with the vehicle simulated as a rigid body. A conventional form of autopilot is provided to control engine gimbaling during powered flight. An ideal form of an autopilot is provided to test conventional autopilot function and provide pseudo RCS function during coasting flight. The simulation is proposed to provide means for studies of abort guidance function and to gain information concerning ability to control the abort trajectory.

An Orbital Trap Mass Analyzer Using a Hybrid Magnetic-Electric Field: A Simulation Study

NASA Astrophysics Data System (ADS)

Xu, Chongsheng; Wu, Fangling; Ding, Li; Ding, Chuan-Fan

2018-03-01

An orbital ion trap mass analyzer employing hybrid magnetic-electric field was designed and simulated. The trap has a rotational symmetrical structure and the hybrid trapping field was created in a toroidal space between 12 pairs of sector detection electrodes. Ion injection and ion orbital motion inside the trap were simulated using SIMION 8.1 with a user Lua program, and the required electric and magnetic field were investigated. The image charge signal can be picked up by the 12 pairs of detection electrodes and the mass resolution was evaluated using FFT. The simulated resolving power for the optimized configuration over 79,000 FWHM was obtained at the magnetic induction intensity of 0.5 Tesla in the simulation. [Figure not available: see fulltext.

Habitability in different Milky Way stellar environments: a stellar interaction dynamical approach.

PubMed

Jiménez-Torres, Juan J; Pichardo, Bárbara; Lake, George; Segura, Antígona

2013-05-01

Every Galactic environment is characterized by a stellar density and a velocity dispersion. With this information from literature, we simulated flyby encounters for several Galactic regions, numerically calculating stellar trajectories as well as orbits for particles in disks; our aim was to understand the effect of typical stellar flybys on planetary (debris) disks in the Milky Way Galaxy. For the solar neighborhood, we examined nearby stars with known distance, proper motions, and radial velocities. We found occurrence of a disturbing impact to the solar planetary disk within the next 8 Myr to be highly unlikely; perturbations to the Oort cloud seem unlikely as well. Current knowledge of the full phase space of stars in the solar neighborhood, however, is rather poor; thus we cannot rule out the existence of a star that is more likely to approach than those for which we have complete kinematic information. We studied the effect of stellar encounters on planetary orbits within the habitable zones of stars in more crowded stellar environments, such as stellar clusters. We found that in open clusters habitable zones are not readily disrupted; this is true if they evaporate in less than 10(8) yr. For older clusters the results may not be the same. We specifically studied the case of Messier 67, one of the oldest open clusters known, and show the effect of this environment on debris disks. We also considered the conditions in globular clusters, the Galactic nucleus, and the Galactic bulge-bar. We calculated the probability of whether Oort clouds exist in these Galactic environments.

STS-53 MS Voss, in EMU, in lowered into JSC's WETF pool for EVA simulation

NASA Image and Video Library

1992-08-07

S92-43335 (28 July 1992) --- STS-53 Discovery, Orbiter Vehicle (OV) 103, Mission Specialist James S. Voss, wearing extravehicular mobility unit (EMU), is lowered into JSC?s Weightless Environment Training Facility (WETF) Bldg. 29 pool. Voss waves to his daughter standing on the poolside as the platform he is positioned in is submerged in the pool. Technicians on the poolside and scuba equipped divers in the water monitor activities. Once underwater, Voss will participate in contingency extravehicular activity (EVA) procedures.

Software technology testbed softpanel prototype

NASA Technical Reports Server (NTRS)

1991-01-01

The following subject areas are covered: analysis of using Ada for the development of real-time control systems for the Space Station; analysis of the functionality of the Application Generator; analysis of the User Support Environment criteria; analysis of the SSE tools and procedures which are to be used for the development of ground/flight software for the Space Station; analysis if the CBATS tutorial (an Ada tutorial package); analysis of Interleaf; analysis of the Integration, Test and Verification process of the Space Station; analysis of the DMS on-orbit flight architecture; analysis of the simulation architecture.

STS-55 Payload Specialist Schlegel with technicians during JSC WETF bailout

NASA Technical Reports Server (NTRS)

1992-01-01

STS-55 Columbia, Orbiter Vehicle (OV) 102, Payload Specialist 2 Hans Schlegel, wearing launch and entry suit (LES), launch and entry helmet (LEH), and parachute, discusses procedures with technicians Karen Porter and Todd Bailey prior to launch emergency egress (bailout) exercises. The session, held in JSC's Weightless Environment Training Facility (WETF) Bldg 29, used the facility's 25-foot deep pool to simulate the ocean as Schlegel and other crewmembers practiced water bailout procedures. Schlegel represents the DLR for the upcoming Spacelab Deutsche 2 (SL-D2) mission.

STS-55 backup Payload Specialist Thiele with technician in JSC's WETF

NASA Technical Reports Server (NTRS)

1992-01-01

STS-55 Columbia, Orbiter Vehicle (OV) 102, backup German Payload Specialist Dr. P. Gerhard Thiele, wearing launch and entry suit (LES), launch and entry helmet (LEH), and parachute, seated on the poolside waits his turn to participate in launch emergency egress (bailout) exercises. The session, held in JSC's Weightless Environment Training Facility (WETF) Bldg 29, used the facility's 25-foot deep pool to simulate the ocean as Thiele and other crewmembers practiced water bailout procedures. Thiele represents the DLR for the upcoming Spacelab Deutsche 2 (SL-D2) mission.

Validation and Verification of LADEE Models and Software

NASA Technical Reports Server (NTRS)

Gundy-Burlet, Karen

2013-01-01

The Lunar Atmosphere Dust Environment Explorer (LADEE) mission will orbit the moon in order to measure the density, composition and time variability of the lunar dust environment. The ground-side and onboard flight software for the mission is being developed using a Model-Based Software methodology. In this technique, models of the spacecraft and flight software are developed in a graphical dynamics modeling package. Flight Software requirements are prototyped and refined using the simulated models. After the model is shown to work as desired in this simulation framework, C-code software is automatically generated from the models. The generated software is then tested in real time Processor-in-the-Loop and Hardware-in-the-Loop test beds. Travelling Road Show test beds were used for early integration tests with payloads and other subsystems. Traditional techniques for verifying computational sciences models are used to characterize the spacecraft simulation. A lightweight set of formal methods analysis, static analysis, formal inspection and code coverage analyses are utilized to further reduce defects in the onboard flight software artifacts. These techniques are applied early and often in the development process, iteratively increasing the capabilities of the software and the fidelity of the vehicle models and test beds.

Feasibility study of a zero-gravity (orbital) atmospheric cloud physics experiments laboratory

NASA Technical Reports Server (NTRS)

Hollinden, A. B.; Eaton, L. R.

1972-01-01

A feasibility and concepts study for a zero-gravity (orbital) atmospheric cloud physics experiment laboratory is discussed. The primary objective was to define a set of cloud physics experiments which will benefit from the near zero-gravity environment of an orbiting spacecraft, identify merits of this environment relative to those of groundbased laboratory facilities, and identify conceptual approaches for the accomplishment of the experiments in an orbiting spacecraft. Solicitation, classification and review of cloud physics experiments for which the advantages of a near zero-gravity environment are evident are described. Identification of experiments for potential early flight opportunities is provided. Several significant accomplishments achieved during the course of this study are presented.

Approaches to dealing with meteoroid and orbital debris protection on the Space Station

NASA Technical Reports Server (NTRS)

Kessler, Donald J.

1990-01-01

Viewgraphs and discussion on approaches to dealing with meteoroid and orbital debris protection on the space station are presented. The National Space Policy of February, 1988, included the following: 'All sectors will seek to minimize the creation of space debris. Design and operations of space tests, experiments, and systems will strive to minimize or reduce accumulation of space debris consistent with mission requirements and cost effectiveness.' The policy also tasked the National Security Council, which established an Interagency Group, which in turn produced an Interagency Report. NASA and DoD tasks to establish a joint plan to determine techniques to measure the environment, and techniques to reduce the environment are addressed. Topics covered include: orbital debris environment, meteoroids, orbital debris population, cataloged earth satellite population, USSPACECOM cataloged objects, and orbital debris radar program.

Acoustic fatigue and sound transmission characteristics of a ram composite panel design

NASA Technical Reports Server (NTRS)

Cockburn, J. A.; Chang, K. Y.; Kao, G. C.

1972-01-01

An experimental study to determine the acoustic fatigue characteristics of a flat multi-layered structural panel is described. The test panel represented a proposed design for the outer skin of a research application module to be housed within the space shuttle orbiter vehicle. The test specimen was mounted in one wall of the Wyle 100,000 cu ft reverberation room and exposed to a broadband acoustic environment having an overall level of 145 db. The test panel was exposed to nine separate applications of the acoustic environment, each application consisting of 250 seconds duration. Upon completion of the ninth test run, the specimen was exposed to a simulated micrometeoroid impact near the panel center. One additional test run of 250 seconds duration was then performed to complete the overall simulation of 50 flight missions. The experimental results show that no significant fatigue damage occurred until the test specimen was exposed to a simulated micrometeoroid impact. The intermediate foam layer forming the core of the test specimen suffered considerable damage due to this impact, causing a marked variation in the dynamic characteristics of the overall test panel. During the final application of the acoustic environment, the strain and acceleration response spectra showed considerable variation from those spectra obtained prior to impact of the panel. Fatigue damage from acoustic loading however, was limited to partial de-bonding around the edges of the composite panel.

Advancements of in-flight mass moment of inertia and structural deflection algorithms for satellite attitude simulators

NASA Astrophysics Data System (ADS)

Wright, Jonathan W.

Experimental satellite attitude simulators have long been used to test and analyze control algorithms in order to drive down risk before implementation on an operational satellite. Ideally, the dynamic response of a terrestrial-based experimental satellite attitude simulator would be similar to that of an on-orbit satellite. Unfortunately, gravitational disturbance torques and poorly characterized moments of inertia introduce uncertainty into the system dynamics leading to questionable attitude control algorithm experimental results. This research consists of three distinct, but related contributions to the field of developing robust satellite attitude simulators. In the first part of this research, existing approaches to estimate mass moments and products of inertia are evaluated followed by a proposition and evaluation of a new approach that increases both the accuracy and precision of these estimates using typical on-board satellite sensors. Next, in order to better simulate the micro-torque environment of space, a new approach to mass balancing satellite attitude simulator is presented, experimentally evaluated, and verified. Finally, in the third area of research, we capitalize on the platform improvements to analyze a control moment gyroscope (CMG) singularity avoidance steering law. Several successful experiments were conducted with the CMG array at near-singular configurations. An evaluation process was implemented to verify that the platform remained near the desired test momentum, showing that the first two components of this research were effective in allowing us to conduct singularity avoidance experiments in a representative space-like test environment.

Ultra Low Outgassing silicone performance in a simulated space ionizing radiation environment

NASA Astrophysics Data System (ADS)

Velderrain, M.; Malave, V.; Taylor, E. W.

2010-09-01

The improvement of silicone-based materials used in space and aerospace environments has garnered much attention for several decades. Most recently, an Ultra Low Outgassing™ silicone incorporating innovative reinforcing and functional fillers has shown that silicone elastomers with unique and specific properties can be developed to meet applications requiring stringent outgassing requirements. This paper will report on the next crucial step in qualifying these materials for spacecraft applications requiring chemical and physical stability in the presence of ionizing radiation. As a first step in this process, selected materials were irradiated with Co-60 gamma-rays to simulate the total dose received in near- Earth orbits. The paper will present pre-and post-irradiation response data of Ultra Low Outgassing silicone samples exposed under ambient air environment coupled with measurements of collected volatile condensable material (CVCM) and total mass loss (TML) per the standard conditions in ASTM E 595. The data will show an insignificant effect on the CVCMs and TMLs after exposure to various dosages of gamma radiation. This data may favorably impact new applications for these silicone materials for use as an improved sealant for space solar cell systems, space structures, satellite systems and aerospace systems.

Radiation Testing at Sandia National Laboratories: Sandia – JPL Collaboration for Europa Lander

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hattar, Khalid Mikhiel; Olszewska-Wasiolek, Maryla Aleksandra

Sandia National Laboratories (SNL) is assisting Jet Propulsion Laboratory in undertaking feasibility studies and performance assessments for the Planetary Protection aspect of the Europa Lander mission. The specific areas of interest for this project are described by task number. This white paper presents the evaluation results for Task 2, Radiation Testing, which was stated as follows: Survey SNL facilities and capabilities for simulating the Europan radiation environment and assess suitability for: A. Testing batteries, electronics, and other component and subsystems B. Exposing biological organisms to assess their survivability metrics. The radiation environment the Europa Lander will encounter on route andmore » in orbit upon arrival at its destination consists primarily of charged particles, energetic protons and electrons with the energies up to 1 GeV. The charged particle environments can be simulated using the accelerators at the Ion Beam Laboratory. The Gamma Irradiation Facility and its annex, the Low Dose Rate Irradiation Facility, offer irradiations using Co-60 gamma sources (1.17 and 1.33 MeV), as well as Cs-137 gamma (0.661 MeV) AmBe neutron (0-10 MeV) sources.« less

Simulation of high-energy radiation belt electron fluxes using NARMAX-VERB coupled codes

PubMed Central

Pakhotin, I P; Drozdov, A Y; Shprits, Y Y; Boynton, R J; Subbotin, D A; Balikhin, M A

2014-01-01

This study presents a fusion of data-driven and physics-driven methodologies of energetic electron flux forecasting in the outer radiation belt. Data-driven NARMAX (Nonlinear AutoRegressive Moving Averages with eXogenous inputs) model predictions for geosynchronous orbit fluxes have been used as an outer boundary condition to drive the physics-based Versatile Electron Radiation Belt (VERB) code, to simulate energetic electron fluxes in the outer radiation belt environment. The coupled system has been tested for three extended time periods totalling several weeks of observations. The time periods involved periods of quiet, moderate, and strong geomagnetic activity and captured a range of dynamics typical of the radiation belts. The model has successfully simulated energetic electron fluxes for various magnetospheric conditions. Physical mechanisms that may be responsible for the discrepancies between the model results and observations are discussed. PMID:26167432

Simulating Valence-to-Core X-ray Emission Spectroscopy of Transition Metal Complexes with Time-Dependent Density Functional Theory.

PubMed

Zhang, Yu; Mukamel, Shaul; Khalil, Munira; Govind, Niranjan

2015-12-08

Valence-to-core (VtC) X-ray emission spectroscopy (XES) has emerged as a powerful technique for the structural characterization of complex organometallic compounds in realistic environments. Since the spectrum represents electronic transitions from the ligand molecular orbitals to the core holes of the metal centers, the approach is more chemically sensitive to the metal-ligand bonding character compared with conventional X-ray absorption techniques. In this paper we study how linear-response time-dependent density functional theory (LR-TDDFT) can be harnessed to simulate K-edge VtC X-ray emission spectra reliably. LR-TDDFT allows one to go beyond the single-particle picture that has been extensively used to simulate VtC-XES. We consider seven low- and high-spin model complexes involving chromium, manganese, and iron transition metal centers. Our results are in good agreement with experiment.

Coevolution of Binaries and Circumbinary Gaseous Disks

NASA Astrophysics Data System (ADS)

Fleming, David; Quinn, Thomas R.

2018-04-01

The recent discoveries of circumbinary planets by Kepler raise questions for contemporary planet formation models. Understanding how these planets form requires characterizing their formation environment, the circumbinary protoplanetary disk, and how the disk and binary interact. The central binary excites resonances in the surrounding protoplanetary disk that drive evolution in both the binary orbital elements and in the disk. To probe how these interactions impact both binary eccentricity and disk structure evolution, we ran N-body smooth particle hydrodynamics (SPH) simulations of gaseous protoplanetary disks surrounding binaries based on Kepler 38 for 10^4 binary orbital periods for several initial binary eccentricities. We find that nearly circular binaries weakly couple to the disk via a parametric instability and excite disk eccentricity growth. Eccentric binaries strongly couple to the disk causing eccentricity growth for both the disk and binary. Disks around sufficiently eccentric binaries strongly couple to the disk and develop an m = 1 spiral wave launched from the 1:3 eccentric outer Lindblad resonance (EOLR). This wave corresponds to an alignment of gas particle longitude of periastrons. We find that in all simulations, the binary semi-major axis decays due to dissipation from the viscous disk.

Evaluation of Low-Earth-Orbit Environmental Effects on International Space Station Thermal Control Materials

NASA Technical Reports Server (NTRS)

Dever, Joyce A.

1998-01-01

Many spacecraft thermal control coatings in low Earth orbit (LEO) can be affected by solar ultraviolet radiation and atomic oxygen. Ultraviolet radiation can darken some polymers and oxides commonly used in thermal control materials. Atomic oxygen can erode polymer materials, but it may reverse the ultraviolet-darkening effect on oxides. Maintaining the desired solar absorptance for thermal control coatings is important to assure the proper operating temperature of the spacecraft. Thermal control coatings to be used on the International Space Station (ISS) were evaluated for their performance after exposure in the NASA Lewis Research Center's Atomic Oxygen-Vacuum Ultraviolet Exposure (AO-VUV) facility. This facility simulated the LEO environments of solar vacuum ultraviolet (VUV) radiation (wavelength range, 115 to 200 nanometers (nm)) and VUV combined with atomic oxygen. Solar absorptance was measured in vacuo to eliminate the "bleaching" effects of ambient oxygen on VUV-induced degradation. The objective of these experiments was to determine solar absorptance increases of various thermal control materials due to exposure to simulated LEO conditions similar to those expected for ISS. Work was done in support of ISS efforts at the requests of Boeing Space and Defense Systems and Lockheed Martin Vought Systems.

Daytime Solar Heating of Photovoltaic Arrays in Low Density Plasmas

NASA Technical Reports Server (NTRS)

Galofaro, J.; Vayner, B.; Ferguson, D.

2003-01-01

The purpose of the current work is to determine the out-gassing rate of H2O molecules for a solar array placed under daytime solar heating (full sunlight) conditions typically encountered in a Low Earth Orbital (LEO) environment. Arc rates are established for individual arrays held at 14 C and are used as a baseline for future comparisons. Radiated thermal solar flux incident to the array is simulated by mounting a stainless steel panel equipped with resistive heating elements several centimeters behind the array. A thermal plot of the heater plate temperature and the array temperature as a function of heating time is then obtained. A mass spectrometer is used to record the levels of partial pressure of water vapor in the test chamber after each of the 5 heating/cooling cycles. Each of the heating cycles was set to time duration of 40 minutes to simulate the daytime solar heat flux to the array over a single orbit. Finally the array is cooled back to ambient temperature after 5 complete cycles and the arc rates of the solar arrays is retested. A comparison of the various data is presented with rather some unexpected results.

Ground test program for a full-size solar dynamic heat receiver

NASA Technical Reports Server (NTRS)

Sedgwick, L. M.; Kaufmann, K. J.; Mclallin, K. L.; Kerslake, T. W.

1991-01-01

Test hardware, facilities, and procedures were developed to conduct ground testing of a full-size, solar dynamic heat receiver in a partially simulated, low earth orbit environment. The heat receiver was designed to supply 102 kW of thermal energy to a helium and xenon gas mixture continuously over a 94 minute orbit, including up to 36 minutes of eclipse. The purpose of the test program was to quantify the receiver thermodynamic performance, its operating temperatures, and thermal response to changes in environmental and power module interface boundary conditions. The heat receiver was tested in a vacuum chamber using liquid nitrogen cold shrouds and an aperture cold plate. Special test equipment was designed to provide the required ranges in interface boundary conditions that typify those expected or required for operation as part of the solar dynamic power module on the Space Station Freedom. The support hardware includes an infrared quartz lamp heater with 30 independently controllable zones and a closed-Brayton cycle engine simulator to circulate and condition the helium-xenon gas mixture. The test article, test support hardware, facilities, and instrumentation developed to conduct the ground test program are all described.

Ground test program for a full-size solar dynamic heat receiver

NASA Technical Reports Server (NTRS)

Sedgwick, L. M.; Kaufmann, K. J.; Mclallin, K. L.; Kerslake, T. W.

1991-01-01

Test hardware, facilities, and procedures were developed to conduct ground testing of a full size, solar dynamic heat receiver in a partially simulated, low Earth orbit environment. The heat receiver was designed to supply 102 kW of thermal energy to a helium and xenon gas mixture continuously over a 94 minute orbit, including up to 36 minutes of eclipse. The purpose of the test program was to quantify the receiver thermodynamic performance, its operating temperatures, and thermal response to changes in environmental and power module interface boundary conditions. The heat receiver was tested in a vacuum chamber using liquid nitrogen cold shrouds and an aperture cold plate. Special test equipment were designed to provide the required ranges in interface boundary conditions that typify those expected or required for operation as part of the solar dynamic power module on the Space Station Freedom. The support hardware includes an infrared quartz lamp heater with 30 independently controllable zones and a closed Brayton cycle engine simulator to circulate and condition the helium xenon gas mixture. The test article, test support hardware, facilities, and instrumentation developed to conduct the ground test program are all described.

Maximizing photovoltaic power generation of a space-dart configured satellite

NASA Astrophysics Data System (ADS)

Lee, Dae Young; Cutler, James W.; Mancewicz, Joe; Ridley, Aaron J.

2015-06-01

Many small satellites are power constrained due to their minimal solar panel area and the eclipse environment of low-Earth orbit. As with larger satellites, these small satellites, including CubeSats, use deployable power arrays to increase power production. This presents a design opportunity to develop various objective functions related to energy management and methods for optimizing these functions over a satellite design. A novel power generation model was created, and a simulation system was developed to evaluate various objective functions describing energy management for complex satellite designs. The model uses a spacecraft-body-fixed spherical coordinate system to analyze the complex geometry of a satellite's self-induced shadowing with computation provided by the Open Graphics Library. As an example design problem, a CubeSat configured as a space-dart with four deployable panels is optimized. Due to the fast computation speed of the solution, an exhaustive search over the design space is used to find the solar panel deployment angles which maximize total power generation. Simulation results are presented for a variety of orbit scenarios. The method is extendable to a variety of complex satellite geometries and power generation systems.

Ground test program for a full-size solar dynamic heat receiver

NASA Astrophysics Data System (ADS)

Sedgwick, L. M.; Kaufmann, K. J.; McLallin, K. L.; Kerslake, T. W.

Test hardware, facilities, and procedures were developed to conduct ground testing of a full-size, solar dynamic heat receiver in a partially simulated, low earth orbit environment. The heat receiver was designed to supply 102 kW of thermal energy to a helium and xenon gas mixture continuously over a 94 minute orbit, including up to 36 minutes of eclipse. The purpose of the test program was to quantify the receiver thermodynamic performance, its operating temperatures, and thermal response to changes in environmental and power module interface boundary conditions. The heat receiver was tested in a vacuum chamber using liquid nitrogen cold shrouds and an aperture cold plate. Special test equipment was designed to provide the required ranges in interface boundary conditions that typify those expected or required for operation as part of the solar dynamic power module on the Space Station Freedom. The support hardware includes an infrared quartz lamp heater with 30 independently controllable zones and a closed-Brayton cycle engine simulator to circulate and condition the helium-xenon gas mixture. The test article, test support hardware, facilities, and instrumentation developed to conduct the ground test program are all described.

Neutral Buoyancy Simulator - SADE NBS Test

NASA Technical Reports Server (NTRS)

1983-01-01

One of the main components of the Hubble Space Telescope (HST) is the Solar Array Drive Electronics (SADE) system. This system interfaces with the Support System Module (SSM) for exchange of operational commands and telemetry data. SADE operates and controls the Solar Array Drive Mechanisms (SADM) for the orientation of the Solar Array Drive (SAD). It also monitors the position of the arrays and the temperature of the SADM. During the first HST servicing mission, the astronauts replaced the SADE component because of some malfunctions. This turned out to be a very challenging extravehicular activity (EVA). Two transistors and two diodes had been thermally stressed with the conformal coating discolored and charred. Soldered cornections became molten and reflowed between the two diodes. The failed transistors gave no indication of defective construction. All repairs were made and the HST was redeposited into orbit. Prior to undertaking this challenging mission, the orbiter's crew trained at Marshall Space Flight Center's (MSFC) Neutral Buoyancy Simulator (NBS) to prepare themselves for working in a low gravity environment. They also practiced replacing HST parts and exercised maneuverability and equipment handling. Pictured is an astronaut practicing climbing a space platform that was necessary in making repairs on the HST.

Neutral Buoyancy Simulator-NB50B-SADE Training Exercises

NASA Technical Reports Server (NTRS)

1983-01-01

One of the main components of the Hubble Space Telescope (HST) is the Solar Array Drive Electronics (SADE) system. This system interfaces with the Support System Module (SSM) for exchange of operational commands and telemetry data. SADE operates and controls the Solar Array Drive Mechanisms (SADM) for the orientation of the Solar Array Drive (SAD). It also monitors the position of the arrays and the temperature of the SADM. During the first HST servicing mission, the astronauts replaced the SADE component because of some malfunctions. This turned out to be a very challenging extravehicular activity (EVA). Two transistors and two diodes had been thermally stressed with the conformal coating discolored and charred. Soldered cornections became molten and reflowed between the two diodes. The failed transistors gave no indication of defective construction. All repairs were made and the HST was redeposited into orbit. Prior to undertaking this challenging mission, the orbiter's crew trained at Marshall Space Flight Center's (MSFC) Neutral Buoyancy Simulator (NBS) to prepare themselves for working in a low gravity environment. They also practiced replacing HST parts and exercised maneuverability and equipment handling. Pictured are crew members practicing on a space platform.

Skylab

NASA Image and Video Library

1970-11-18

After the end of the Apollo missions, NASA's next adventure into space was the marned spaceflight of Skylab. Using an S-IVB stage of the Saturn V launch vehicle, Skylab was a two-story orbiting laboratory, one floor being living quarters and the other a work room. The objectives of Skylab were to enrich our scientific knowledge of the Earth, the Sun, the stars, and cosmic space; to study the effects of weightlessness on living organisms, including man; to study the effects of the processing and manufacturing of materials utilizing the absence of gravity; and to conduct Earth resource observations. At the Marshall Space Flight Center (MSFC), astronauts and engineers spent hundreds of hours in an MSFC Neutral Buoyancy Simulator (NBS) rehearsing procedures to be used during the Skylab mission, developing techniques, and detecting and correcting potential problems. The NBS was a 40-foot deep water tank that simulated the weightlessness environment of space. This photograph shows astronaut Ed Gibbon (a prime crew member of the Skylab-4 mission) during the neutral buoyancy Skylab extravehicular activity training at the Apollo Telescope Mount (ATM) mockup. One of Skylab's major components, the ATM was the most powerful astronomical observatory ever put into orbit to date.