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Sample records for electrodynamic tether system

  1. Electrodynamic Tether Propulsion System

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This picture is an artist's concept of an orbiting vehicle using the Electrodynamic Tethers Propulsion System. Relatively short electrodynamic tethers can use solar power to push against a planetary magnetic field to achieve propulsion without the expenditure of propellant.

  2. Electrodynamic tether system study

    NASA Technical Reports Server (NTRS)

    1987-01-01

    The purpose of this program is to define an Electrodynamic Tether System (ETS) that could be erected from the space station and/or platforms to function as an energy storage device. A schematic representation of the ETS concept mounted on the space station is presented. In addition to the hardware design and configuration efforts, studies are also documented involving simulations of the Earth's magnetic fields and the effects this has on overall system efficiency calculations. Also discussed are some preliminary computer simulations of orbit perturbations caused by the cyclic/night operations of the ETS. System cost estimates, an outline for future development testing for the ETS system, and conclusions and recommendations are also provided.

  3. Systems analysis of electrodynamic tethers

    SciTech Connect

    Samantha, R.I.; Hastings, D.E.; Ahedo, E. )

    1992-06-01

    A dynamic simulation model is developed and employed in a new system study to investigate the performance of electrodynamic tethers, both as power generators and thrusters. The electron collection performance of a contactor and a bare wire tether, both separately and in combination, are compared and contrasted. The power and thrust generated by a bare wire tether is found to have a higher dependence on the geomagnetic and ionospheric fluctuations. However, depending on the performance of the contactor, the combination of a bare tether and contactor can substantially boost performance for power generation. As a pure thruster, the contactor tether is examined at constant current, voltage, thrust, and power. It is found that the best mode of operation is with constant power, with resulting power/thrust ratios better than those for ion or magnetoplasmadynamic engines. It is concluded that tethers offer greater potential than previously envisioned. 13 refs.

  4. Combination Solar Sail and Electrodynamic Tether Propulsion System

    NASA Technical Reports Server (NTRS)

    Johnson, Charles L. (Inventor); Matloff, Gregory L. (Inventor)

    2003-01-01

    A propulsion system for a spacecraft includes a solar sail system and an electrodynamic tether system is presented. The solar sail system is used to generate propulsion to propel the spacecraft through space using solar photons and the electrodynamic tether system is used to generate propulsion to steer the spacecraft into orbit and to perform orbital maneuvers around a planet using the planet's magnetic field. The electrodynamic tether system can also be used to generate power for the spacecraft using the planet's magnetic field.

  5. Electrodynamic Tether

    NASA Technical Reports Server (NTRS)

    Johnson, Charles L. (Inventor); Ballance, Judy L. (Inventor); Welzyn, Kenneth J. (Inventor); Vaughn, Jason A. (Inventor); Lorenzini, Enrico (Inventor); Schuler, Peter S. (Inventor)

    2006-01-01

    A tether system for providing thrust to or power subsystems of an artificial satellite in a low earth orbit. The tether has three main sections, an insulated section connected to the satellite, a conducting section connected to the insulating section for drawing in and releasing electrons from the space plasma and a non-conducting section for providing a tension to the other sections of the tether. An oxygen resistant coating is applied to the bare wire of the conducting section as well as the insulated wires of the insulated section that prevents breakdown during tether operations in the space plasma. The insulated and bare wire sections also surround a high tensile flexible polymer core to prevent any debris from breaking the tether during use.

  6. Lyapunov Orbits in the Jupiter System Using Electrodynamic Tethers

    NASA Technical Reports Server (NTRS)

    Bokelmann, Kevin; Russell, Ryan P.; Lantoine, Gregory

    2013-01-01

    Various researchers have proposed the use of electrodynamic tethers for power generation and capture from interplanetary transfers. The effect of tether forces on periodic orbits in Jupiter-satellite systems are investigated. A perturbation force is added to the restricted three-body problem model and a series of simplifications allows development of a conservative system that retains the Jacobi integral. Expressions are developed to find modified locations of equilibrium positions. Modified families of Lyapunov orbits are generated as functions of tether size and Jacobi integral. Zero velocity curves and stability analyses are used to evaluate the dynamical properties of tether-modified orbits.

  7. Electrodynamic Bare Tether Systems as a Thruster for the Momentum-Exchange/Electrodynamic Reboost(MXER)Project

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Krivorutsky, E. N.; Gallagher, D. L.

    2006-01-01

    The concept of electrodynamic tether propulsion has a number of attractive features and has been widely discussed for different applications. Different system designs have been proposed and compared during the last 10 years. In spite of this, the choice of proper design for any particular mission is a unique problem. Such characteristics of tether performance as system acceleration, efficiency, etc., should be calculated and compared on the basis of the known capability of a tether to collect electrical current. We discuss the choice of parameters for circular and tape tethers with regard to the Momentum-Exchange/Electrodynamic Reboost (MXER) tether project.

  8. Conductive Tether Coating for Electrodynamic Tethers

    NASA Technical Reports Server (NTRS)

    Vaughn, Jason A.; Schuler, Pete

    2000-01-01

    The Propulsive Small Expendable Deployer System (ProSEDS), which is an on-orbit demonstration of the propulsion capabilities of electrodynamic tethers in space, is a secondary payload on a Delta 11 unmanned expendable booster. The ProSEDS tether consists of a 5 km bare electrodynamic tether and a 1 0-km non-conductive leader tether. Near the Delta 11, 160 m of the conductive tether is insulated to prevent plasma electron collection from the plasma contactor and for other science requirements. The remainder of the 5-km conductive tether is coated with a new conductive coating to collect plasma electrons. A bare metal tether easily collects electrons from the plasma, but thermal concerns preclude this design. A highly emissive conductive polymer developed by Triton Systems, Inc. has been optimized for both conductivity and thermo-optical properties. The current design for the ProSEDS conductive tether is seven individually coated strands of 28 AWG aluminum wire, coated with an atomic oxygen-resistant conductive polymer composed of a mixture of COR (Colorless Oxygen Resistant) and polyanaline (PANI) known as C-COR (Conductive-Colorless Oxygen Resistant). The conductive-coated wire strands are cold-welded to individually coated strands of the insulated tether. The insulated tether is coated with 1 mil of polyimide and an atomic oxygen resistant polymer TOR-BP. The insulated tether must stand off the entire voltage of the tether (1 200 V) at various times during the mission. All seven wires are twisted around a Kevlar-29 core using the Hi-wire design. Extensive testing has been performed at the Marshall Space Flight Center to qualify both the conductive coating and insulating coating for use on the ProSEDS tether. The conductive coating has been exposed to a plasma to verify the coatings ability to collect electrons from the space plasma from 0 to 1500 V, and to verify the coatings ability to collect electrons after atomic oxygen exposure. The insulated coating has been

  9. Electrodynamic Propulsion System Tether Experiment (T-REX)

    NASA Technical Reports Server (NTRS)

    Johnson, L.; Fujii, H. A.; Sanmartin, J. R.

    2010-01-01

    A Japanese-led international team is developing a suborbital test of orbital-motion-limited (OML) bare wire anode current collection for application to electrodynamic tether (EDT) propulsion. The tether is a tape with a width of 25 mm, thickness of 0.05 mm, and is 300 m in length. This will be the first space test of OML theory. The mission will launch in the summer of 2010 using an S520 Sounding Rocket. During ascent, and above approximately 100 km in attitude, the tape tether will be deployed at a rate of approximately8 m/s. Once deployed, the tape tether will serve as an anode, collecting ionospheric electrons. The electrons will be expelled into space by a hollow cathode device, thereby completing the circuit and allowing current to flow. The total amount of current collected will be used to assess the validity of OML theory. This paper will describe the objectives of the proposed mission, the technologies to be employed, and the application of the results to future space missions using EDTs for propulsion or power generation

  10. The tethered satellite electrodynamics experiment project

    NASA Technical Reports Server (NTRS)

    Price, John M.

    1988-01-01

    NASA and Italy's PSN have undertaken the Tethered Satellite Electrodynamics Experiment, in which two tethered bodies will be equipped with data-collecting scientific instruments, as the first stage of the development of the Tethered Satellite System that can be deployed by the Space Shuttle. The experiment will give attention to the electromagnetic interaction between the satellite/tether/orbiter system and the ambient space plasma, and should demonstrate the operation of both satellite- and Shuttle-borne electrodynamic instruments with a conductive tether.

  11. The PROPEL Electrodynamic Tether Demonstration Mission

    NASA Technical Reports Server (NTRS)

    Bilen, Sven G.; Johnson, C. Les; Wiegmann, Bruce M.; Alexander, Leslie; Gilchrist, Brian E.; Hoyt, Robert P.; Elder, Craig H.; Fuhrhop, Keith P.; Scadera, Michael

    2012-01-01

    The PROPEL ("Propulsion using Electrodynamics") mission will demonstrate the operation of an electrodynamic tether propulsion system in low Earth orbit and advance its technology readiness level for multiple applications. The PROPEL mission has two primary objectives: first, to demonstrate the capability of electrodynamic tether technology to provide robust and safe, near-propellantless propulsion for orbit-raising, de-orbit, plane change, and station keeping, as well as to perform orbital power harvesting and formation flight; and, second, to fully characterize and validate the performance of an integrated electrodynamic tether propulsion system, qualifying it for infusion into future multiple satellite platforms and missions with minimal modification. This paper provides an overview of the PROPEL system and design reference missions; mission goals and required measurements; and ongoing PROPEL mission design efforts.

  12. Calculating the electromagnetic field on the earth due to an electrodynamic tethered system in the ionosphere

    NASA Technical Reports Server (NTRS)

    Estes, Robert D.

    1989-01-01

    A method is presented for calculating the electromagnetic wave field on the earth's surface associated with the operation of an electrodynamic tethered satellite system of constant or slowly varying current in the upper ionosphere. The wave field at the ionospheric boundary and on the earth's surface is obtained by numerical integration. The results suggest that the ionospheric waves do not propagate into the atmosphere and that the image of the Alfven wings from a steady-current tether should be greatly broadened on the earth's surface.

  13. Polymeric Coatings for Electrodynamic Tethers

    NASA Technical Reports Server (NTRS)

    Vaughn, Jason A.; Kamenetzky, Rachel R.; Finckenor, Miria M.; Schuler, Peter

    2000-01-01

    Two polymeric coatings have been developed for the Propulsive Small Expendable Deployer System (ProSEDS) mission. ProSEDS is designed to provide an on-orbit demonstration of the electrodynamic propulsion capabilities of tethers in space. The ProSEDS experiment will be a secondary payload on a Delta II unmanned expendable booster scheduled for launch in August 2000. A 5-km conductive tether is attached to the Delta 11 second stage and collects current from the low Earth orbit (LEO) plasma to facilitate de-orbit of the spent stage. The conductive tether is attached to a 10-km non-conductive tether, the other end of which is attached to an endmass containing several scientific instruments. A bare metal tether would have the best conductivity but thermal concerns preclude this design. A conductive polymer developed by Triton Systems has been optimized for conductivity and thermo-optical properties. The current design for the ProSEDS conductive tether is seven strands of 28 AWG aluminum wire individually coated with 8.7 micrometers (0.35 mil) of an atomic oxygen-resistant conductive polymer composed of a mixture of 87% Clear Oxygen-Resistant polymer (COR) and 13% polyanaline (PANi), wrapped around a braided Kevlar (TM) 49 core. Extensive testing has been performed at the Marshall Space Flight Center (MSFC) to qualify this material for flight on ProSEDS. Atomic oxygen exposure was performed, with solar absorptance and infrared emittance measured before and after exposure. Conductivity was measured before and after atomic oxygen exposure. High voltage tests, up to 1500 V, of the current collecting ability of the COR/PANi have been completed. Approximately 160 meters of the conductive tether closest to the Delta 11 second stage is insulated to prevent any electron reconnection to the tether from the plasma contactor. The insulation is composed of polyimide overcoated with TOR-BP, another polymeric coating developed by Triton for this mission. TOR-BP acts as both insulator

  14. An electrodynamic tether system for propulsion and power generation in a Jovian mission

    NASA Astrophysics Data System (ADS)

    Castronuovo, M. M.; Laneve, G.; Ulivieri, C.

    2002-01-01

    The paper concerns an innovative propulsive/power system exploiting the magnetic field and the charged atmosphere present on some planets of our solar system. In fact a conductive tether moving in the above mentioned environment is able to provide a low thrust for orbital control and/or power generation for on-board systems. This solution is considered particularly promising for the exploration of outer planets where the low solar luminosity makes the use of solar panels unsuitable. On the other end the use of radioactive thermoelectric generators (RTG) might be ruled out on future missions due to the finite risk of releasing plutonium into the terrestrial environment. The main objective of the present paper is the assessment of the feasibility and applicability of an electrodynamic tether system to missions devoted to the exploration of the Jovian system. Among the outer planets, at the present stage of knowledge, Jupiter is by far the most promising target for the proposed system application. In fact, it has a large and energetic magnetosphere ideally suited for electrodynamic tether operations and due to its rapid rotation, its magnetic field sweeps the tether rather than being swept by it (as in the Earth case). The net effect will be the increase of spacecraft momentum, thus allowing the raise of its orbit, and/or on-board power generation, without any expenditure of propellants. .

  15. Space Station Reboost with Electrodynamic Tethers

    NASA Technical Reports Server (NTRS)

    Vas, Irwin E.; Kelly, Thomas J.; Scarl, Ethan A.

    1999-01-01

    This paper presents the results of a study of an electrodynamic tether system to reboost the International Space Station (ISS). One recommendation is to use a partially bare tether for electron collection. Locations are suggested as to where the tether system is to be attached at the space station. The effects of the tether system on the microgravity environment may actually be beneficial, because the system can neutralize aerodrag during quiescent periods and, if deployed from a movable boom, can permit optimization of laboratory positioning with respect to acceleration contours. Alternative approaches to tether deployment and retrieval are discussed. It is shown that a relatively short tether system, 7 km long, operating at a power level of 5 kW could provide cumulative savings or over a billion dollars during a 10-year period ending in 2012. This savings is the direct result of a reduction in the number or nights that would otherwise be required to deliver propellant for reboost, with larger cost savings for higher tether usage. In addition to economic considerations, an electrodynamic tether promises a practical backup system that could ensure ISS survival in the event of an (otherwise) catastrophic delay in propellant delivery.

  16. Dynamics of an Electrodynamic Tether System in a Varying Space-Plasma Environment

    NASA Astrophysics Data System (ADS)

    Janeski, John A.

    Electrodynamic tethers have a wide range of proposed applications in the fields of satellite propulsion and space plasma research. The fundamental purpose of this dissertation is to improve the understanding of the behavior of an electrodynamic tether (EDT) system in Earth's ionosphere. An electrodynamic tether system consists of two satellites connected by a long tether that generates current to produce either power or thrust via the system's electromagnetic interaction with the space environment. Previous electrodynamic tether investigations decouple the interaction between the tether and the constantly changing plasma environment. The limiting factor inhibiting the development of a full system model that has an accurate characterization of the tether/plasma interaction is that the understanding of that interaction is not well developed over a wide range of system parameters. The EDT system model developed in this study uses a high fidelity dynamics model that includes a tether current described by an analytical current collection model whose plasma parameters are determine by the International Reference Ionosphere. It is first shown that new instabilities are induced in the system dynamics under a basic analytical current model versus a constant current model. A 2-D3v Particle-in-Cell (PIC) code has been developed to study the plasma dynamics near a positively charged EDT system end-body and their impact on the current collected. Simulations are run over a range of system parameters that occur throughout a LEO orbit. The azimuthal current structures observed during the TSS-1R mission are found to enhance the current collected by the satellite when the magnetic field is slightly off of perpendicular to the orbital velocity. When the in-plane component of the magnetic field becomes large, the electrons are not able to easily cross the field lines causing plasma lobes form above and below the satellite. The lobes limit the current arriving to the satellite and also

  17. Electrodynamic Tethers for Novel LEO Missions

    NASA Technical Reports Server (NTRS)

    Kantner, Michael; Hoyt, Robert; Scardera, Michael; Johnson, Charles

    2011-01-01

    The exponential increase of launch system size - and cost - with deltaV makes missions requiring large total impulse cost prohibitive. Northrop Grumman and partners have matured a fundamentally different method for generating propulsion using electrodynamic tethers (EDTs) that escapes the limitations of the rocket equation. With essentially unlimited delta V, we can perform new classes of missions that are currently unaffordable or unfeasible.

  18. Electrodynamics of the Getaway Tether Experiment

    NASA Technical Reports Server (NTRS)

    Greene, Michael; Baginski, Michael; Wheelock, Douglas

    1989-01-01

    An electrodynamic circuit model of the interaction of a pair of small tethered satellites and the ionosphere is developed and analyzed. The system under study, the Getaway Tether Experiment (GATE), is composed of two small satellites and 1 km of insulated conducting tether. The nonlinear model has elements representing the emission, collection, and resistive flow of charge through an electrically conductive tether, plasma contactors, and the ionosphere. The circuit model is incorporated into a dynamic orbital simulation to predict mission performance. Simulation results show the feasibility to bilaterally transfer energy between stored electrical energy and orbital momentum. A transient model is also developed using the circuit model and a string of N lumped-parameter modules, each consisting of resistance, capacitance, and induced potential for the tether. Transients are shown via simulation to occur over millisecond intervals.

  19. Implementation Options for the PROPEL Electrodynamic Tether Demonstration Mission

    NASA Technical Reports Server (NTRS)

    Bilen, Sven G.; Johnson, Les; Gilchrist, Brian E.; Hoyt, Robert P.; Elder, Craig H.; Fuhrhop, Keith P.; Scadera, Michael P.; Stone, Nobie H.

    2014-01-01

    The PROPEL flight mission concept will demonstrate the safe use of an electrodynamic tether for generating thrust. PROPEL is being designed to be a versatile electrodynamic-tether system for multiple end users and to be flexible with respect to platform. As such, several implementation options are being explored, including a comprehensive mission design for PROPEL with a mission duration of six months; a space demonstration mission concept design with configuration of a pair of tethered satellites, one of which is the Japanese H-II Transfer Vehicle; and an ESPA-based system. We report here on these possible implementation options for PROPEL. electrodynamic tether; PROPEL demonstration mission; propellantless propulsion

  20. Spacecraft Solar Sails Containing Electrodynamic Tethers

    NASA Technical Reports Server (NTRS)

    Johnson, Les; Matloff, Greg

    2005-01-01

    A report discusses a proposal to use large, lightweight solar sails embedded with electrodynamic tethers (essentially, networks of wires) to (1) propel robotic spacecraft to distant planets, then (2) exploit the planetary magnetic fields to capture the spacecraft into orbits around the planets. The purpose of the proposal is, of course, to make it possible to undertake long interplanetary missions without incurring the large cost and weight penalties of conventional rocket-type propulsion systems. Through transfer of momentum from reflected solar photons, a sail would generate thrust outward from the Sun. Upon arrival in the vicinity of a planet, the electrodynamic tethers would be put to use: Motion of the spacecraft across the planetary magnetic field would induce electric currents in the tether wires, giving rise to an electromagnetic drag force that would be exploited to brake the spacecraft for capture into orbit. The sail with embedded tethers would be made to spin to provide stability during capture. Depending upon the requirements of a particular application, it could be necessary to extend the tether to a diameter greater than that of the sail.

  1. Optimal Electrodynamic Tether Phasing Maneuvers

    NASA Technical Reports Server (NTRS)

    Bitzer, Matthew S.; Hall, Christopher D.

    2007-01-01

    We study the minimum-time orbit phasing maneuver problem for a constant-current electrodynamic tether (EDT). The EDT is assumed to be a point mass and the electromagnetic forces acting on the tether are always perpendicular to the local magnetic field. After deriving and non-dimensionalizing the equations of motion, the only input parameters become current and the phase angle. Solution examples, including initial Lagrange costates, time of flight, thrust plots, and thrust angle profiles, are given for a wide range of current magnitudes and phase angles. The two-dimensional cases presented use a non-tilted magnetic dipole model, and the solutions are compared to existing literature. We are able to compare similar trajectories for a constant thrust phasing maneuver and we find that the time of flight is longer for the constant thrust case with similar initial thrust values and phase angles. Full three-dimensional solutions, which use a titled magnetic dipole model, are also analyzed for orbits with small inclinations.

  2. International Space Station Electrodynamic Tether Reboost Study

    NASA Technical Reports Server (NTRS)

    Johnson, L.; Herrmann, M.

    1998-01-01

    The International Space Station (ISS) will require periodic reboost due to atmospheric aerodynamic drag. This is nominally achieved through the use of thruster firings by the attached Progress M spacecraft. Many Progress flights to the ISS are required annually. Electrodynamic tethers provide an attractive alternative in that they can provide periodic reboost or continuous drag cancellation using no consumables, propellant, nor conventional propulsion elements. The system could also serve as an emergency backup reboost system used only in the event resupply and reboost are delayed for some reason.

  3. Conjunctions and Collision Avoidance with Electrodynamic Tethers

    NASA Astrophysics Data System (ADS)

    Levin, E.

    2013-09-01

    Electrodynamic propulsion technology is currently in development by NASA, ESA, and JAXA for the purpose of affordable removal of large debris objects from LEO. At the same time, the Naval Research Laboratory is preparing a 3U CubeSat with a 1-km electrodynamic tether for a flight demonstration of electrodynamic propulsion. This type of propulsion does not require fuel. The electrodynamic thrust is the Lorentz force acting on the electric current in a long conductor (tether) in the geomagnetic field. Electrons are collected from the ambient plasma on one end and emitted back into the plasma from the other end. The electric current loop is closed through the ionosphere, as demonstrated in two previous flights. The vehicle is solar powered. To support safe navigation of electrodynamic tethers, proper conjunction analysis and collision avoidance strategies are needed. The typical lengths of electrodynamic tethers for near-term applications are measured in kilometers, and the conjunction geometry is very different from the geometry of conjunctions between compact objects. It is commonly thought that the collision cross-section in a conjunction between a tether and a compact object is represented by the product of the tether length and the size of the object. However, rigorous analysis shows that this is not the case, and that the above assumption leads to grossly overestimated collision probabilities. The paper will present the results of a detailed mathematical analysis of the conjunction geometry and collision probabilities in close approaches between electrodynamic tethers and compact objects, such as satellites, rocket bodies, and debris fragments. Electrodynamic spacecraft will not require fuel, and therefore, can thrust constantly. Their orbit transfers can take many days, but can result in major orbit changes, including large rotations of the orbital plane, both in the inclination and the node. During these orbit transfers, the electrodynamic spacecraft will

  4. The effects of a realistic hollow cathode plasma contactor model on the simulation of bare electrodynamic tether systems

    NASA Astrophysics Data System (ADS)

    Blash, Derek M.

    The region known as Low-Earth Orbit (LEO) has become populated with artificial satellites and space debris since humanities initial venture into the region. This has turned LEO into a hazardous region. Since LEO is very valuable to many different countries, there has been a push to prevent further buildup and talk of even deorbiting spent satellites and debris already in LEO. One of the more attractive concepts available for deorbiting debris and spent satellites is a Bare Electrodynamic Tether (BET). A BET is a propellantless propulsion technique in which two objects are joined together by a thin conducting material. When these tethered objects are placed in LEO, the tether sweeps across the magnetic field lines of the Earth and induces an electromotive force (emf) along the tether. Current from the space plasma is collected on the bare tether under the action of the induced emf, and this current interacts with the Earth's magnetic field to create a drag force that can be used to deorbit spent satellites and space debris. A Plasma Contactor (PC) is used to close the electrical circuit between the BET and the ionospheric plasma. The PC requires a voltage and, depending on the device, a gas flow to emit electrons through a plasma bridge to the ionospheric plasma. The PC also can require a plasma discharge electrode and a heater to condition the PC for operation. These parameters as well as the PC performance are required to build an accurate simulation of a PC and, therefore, a BET deorbiting system. This thesis focuses on the development, validation, and implementation of a simulation tool to model the effects of a realistic hollow cathode PC system model on a BET deorbit system.

  5. Plasma Motor Generator (PMG) electrodynamic tether experiment

    NASA Technical Reports Server (NTRS)

    Grossi, Mario D.

    1995-01-01

    The Plasma Motor Generator (PMG) flight of June 26, 1993 has been the most sophisticated and most successful mission that has been carried out thus far with an electrodynamic tether. Three papers from the Smithsonian Astrophysical Observatory, Washington, DC concerned with the PMG, submitted at the Fourth International Space Conference on Tethers in Space, in Washington, DC, in April 1995, are contained in this document. The three papers are (1) Electromagnetic interactions between the PMG tether and the magneto-ionic medium of the Ionosphere; (2) Tether-current-voltage characteristics, as determined by the Hollow Cathode Operation Modes; and (3) Hawaii-Hilo ground observations on the occasion for the PMG flight of June 23, 1993.

  6. Tethered satellite system

    NASA Technical Reports Server (NTRS)

    Sisson, J.

    1986-01-01

    A reusable system is to be developed to enable a variety of scientific investigations to be accomplished from the shuttle, considering the use of a tethered system with manual or automated control, deployment of a satellite toward or away from the Earth, up to 100 km, and conducting or nonconducting tether. Experiments and scientific investigations are to be performed using the tether system for applications such as magnetometry, electrodynamics, atmospheric science, and chemical release. A program is being implemented as a cooperative U.S./Italian activity. The proposed systems, investigations, and the program are charted and briefly discussed.

  7. Electrodynamic Tether as a Thruster for LEO Mission Applications

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V; Krivorutsky, E. N.; Johnson, L.

    2006-01-01

    Electrodynamic tether propulsion has a number of attractive features and has been widely discussed for different low earth orbit applications. Despite the commonality of application, the choice of the proper design for any particular mission is a unique problem. The flight trajectory, duration, available power and voltage, and drag force should be taken into consideration with other mission requirements. Characteristics of tether performance such as system acceleration and electrical efficiency should be calculated and assessed based on the system's capability to collect electrical current. We discuss the choice of parameters for circular, tape, and grid-sphere tether anodes and their applicability to International Space Station (ISS) reboost and Momentum Exchange Electrodynamic Reboost (MXER) applications.

  8. Electrodynamic Tether Propulsion and Power Generation at Jupiter

    NASA Technical Reports Server (NTRS)

    Gallagher, D. L.; Johnson, L.; Moore, J.; Bagenal, F.

    1998-01-01

    The results of a study performed to evaluate the feasibility and merits of using an electrodynamic tether for propulsion and power generation for a spacecraft in the Jovian system are presented. The environment of the Jovian system has properties which are particularly favorable for utilization of an electrodynamic tether. Specifically, the planet has a strong magnetic field and the mass of the planet dictates high orbital velocities which, when combined with the planet's rapid rotation rate, can produce very large relative velocities between the magnetic field and the spacecraft. In a circular orbit close to the planet, tether propulsive forces are found to be as high as 50 N and power levels as high as 1 MW.

  9. The PROPEL Electrodynamic Tether Mission and Connecting to the Ionosphere

    NASA Technical Reports Server (NTRS)

    Gilchrist, Brian; Bilen, Sven; Hoyt, Rob; Stone,Nobie; Vaughn, Jason; Fuhrhop, Keith; Krause, Linda; Khazanov, George; Johnson, Les

    2012-01-01

    The exponential increase of launch system size.and cost.with delta-V makes missions that require large total impulse cost prohibitive. Led by NASA's Marshall Space Flight Center, a team from government, industry, and academia has developed a flight demonstration mission concept of an integrated electrodynamic (ED) tethered satellite system called PROPEL: "Propulsion using Electrodynamics". The PROPEL Mission is focused on demonstrating a versatile configuration of an ED tether to overcome the limitations of the rocket equation, enable new classes of missions currently unaffordable or infeasible, and significantly advance the Technology Readiness Level (TRL) to an operational level. We are also focused on establishing a far deeper understanding of critical processes and technologies to be able to scale and improve tether systems in the future. Here, we provide an overview of the proposed PROPEL mission. One of the critical processes for efficient ED tether operation is the ability to inject current to and collect current from the ionosphere. Because the PROPEL mission is planned to have both boost and deboost capability using a single tether, the tether current must be capable of flowing in both directions and at levels well over 1 A. Given the greater mobility of electrons over that of ions, this generally requires that both ends of the ED tether system can both collect and emit electrons. For example, hollow cathode plasma contactors (HCPCs) generally are viewed as state-of-the-art and high TRL devices; however, for ED tether applications important questions remain of how efficiently they can operate as both electron collectors and emitters. Other technologies will be highlighted that are being investigated as possible alternatives to the HCPC such as Solex that generates a plasma cloud from a solid material (Teflon) and electron emission (only) technologies such as cold-cathode electron field emission or photo-electron beam generation (PEBG) techniques.

  10. Laboratory experiments on the electrodynamic behavior of tethers in space

    NASA Technical Reports Server (NTRS)

    Stenzel, Reiner L.; Urrutia, Manuel J.

    1991-01-01

    The transient current systems between tethered plasmas in a large magnetoplasma are investigated experimentally for extrapolation to electrodynamic tethers in space. The studies measure the perturbed magnetic fields and the current density associated with pulsed currents to electrodes in three-dimensional space and time. The electrodes excite electron whistlers because they produce fields that dominantly couple to electrons, allowing pulsed currents to propagate and disperse as whistler wave packets. The wave packets evolve into force-free, flux-ropelike field configurations, and a whistler 'wedge' is formed in the plasma due to 'eddy' currents caused by insulated tethers with dc currents. Substantial radiation into the whistler mode happens with moving VLF antennas as well as tethers, and the wave spread within the ray cone is the most significant characteristic event. The wave spread widens the current channel, incites current closure, and is also associated with a 'phantom loop' phenomenon.

  11. Electrodynamics of long metallic tethers in the ionospheric plasma

    NASA Technical Reports Server (NTRS)

    Dobrowolny, M.

    1978-01-01

    A study is presented of the electrodynamic interactions of long metallic tethers (lengths up to 100 km) with the ionospheric plasma. The study, which is of interest in view of possible future experiments using long tethers in space, includes the derivation of current and potential distribution along the tether, taking also the effects of internal resistance into account. Electrostatic and electrodynamic drag forces are computed and compared with aerodynamic drag.

  12. Power Generation for a JUNO-type Mission using Electrodynamic Tethers

    NASA Astrophysics Data System (ADS)

    Bombardelli, C.; Lorenzini, E. C.; Sanmartin, J. R.

    2008-09-01

    Electrodynamic tethers are known to exhibit high performance in the Jupiter environment , both as propellantless propulsion devices and as power generating systems. In spite of the considerable amount of research work of electrodynamic tethers in the Jupiter environment the case involving high inclination orbit has never been addressed so far. We present a power generation scheme for rotating electrodynamic tethers which can be applied to a generic Jupiter science missions employing polar orbits. We show that when the orbit inclination reaches 90 degrees and the tether rotates in the orbital plane the effect of the tether electrodynamic force does not impact orbital energy but orbit inclination. Thanks to favorable environmental conditions at Jupiter (i.e. strong magnetic field and fast rotating plasmasphere) relatively high power levels can be obtained with tethers of modest length when the tether transits the low altitude regions around the planet. In addition the impact on orbit inclination is minimal thanks to the high specific angular momentum of jovian orbits. As a numerical example we consider an electrodynamic tether subsystem consisting of two 3- km-long 5-cm wide and 0.05-mm-thick tape tether arms deployed radially from a main central spacecraft whose orbit has the characteristic of the current baseline JUNO orbit. The tether subsystem, whose total mass is less than 50 kg, can provide kW level average power along a 120 degrees orbital arc around the equatorial plane crossing. The inclination variation induced by the Lorentz force in this case is below 1/1000 of a degree per orbit. Applications of the concept to future Jupiter exploration missions are discussed.

  13. Implementation Options for the PROPEL Electrodynamic Tether Demonstration Mission

    NASA Technical Reports Server (NTRS)

    Bilen, Sven G.; Johnson, C. Les; Gilchrist, Brian E.; Hoyt, Robert P.; Elder, Craig H.; Fuhrhop, Keith P.; Scadera, Michael; Stone, Nobie

    2014-01-01

    The PROPEL ("Propulsion using Electrodynamics") flight demonstration mission concept will demonstrate the use of an electrodynamic tether (EDT) for generating thrust, which will allow the propulsion system to overcome the limitations of the rocket equation. The mission concept has been developed by a team of government, industry, and academia partners led by NASA Marshall Space Flight Center (MSFC). PROPEL is being designed for versatility of the EDT system with multiple end users in mind and to be flexible with respect to platform. Previously, we reported on a comprehensive mission design for PROPEL with a mission duration of six months or longer with multiple mission goals including demonstration of significant boost, deboost, inclination change, and drag make-up activities. To explore a range of possible configurations, primarily driven by cost considerations, other mission concept designs have been pursued. In partnership with the NASA's Office of Chief Technologist (OCT) Game Changing Program, NASA MSFC Leadership, and the MSFC Advanced Concepts Office, a mission concept design was developed for a near-term EDT propulsion flight validation mission. The Electrodynamic Tether Propulsion Study (ETPS) defined an EDT propulsion system capable of very large delta-V for use on future missions developed by NASA, DoD, and commercial customers. To demonstrate the feasibility of an ETPS, the study focused on a space demonstration mission concept design with configuration of a pair of tethered satellite busses, one of which is the Japanese H-II Transfer Vehicle (HTV). The HTV would fly its standard ISS resupply mission. When resupply mission is complete, the ISS reconfigures and releases the HTV to perform the EDT experiment at safe orbital altitudes below the ISS. Though the focus of this particular mission concept design addresses a scenario involving the HTV or a similar vehicle, the propulsion system's capability is relevant to a number of applications, as noted above

  14. Plasma Interactions With a Negative Biased Electrodynamic Tether

    NASA Technical Reports Server (NTRS)

    Vaughn, Jason A.; Curtis, Leslie; Welzyn, Ken J.

    2004-01-01

    The ProSEDS conductive tether design incorporates two distinct types of tethers from a plasma interaction viewpoint. The 200 m closest to the Delta II spacecraft is insulated from the plasma, and the remaining 4800 m is semi-bare. This latter portion is considered semi-bare because a conductive coating, which is designed to collect electrons from the plasma, was applied to the wires to regulate the overall tether temperature. Because the tether has both insulating and conductive tether sections, a transition point exists between the two that forms a triple point with the space plasma. Also, insulated tethers can arc to the space plasma if the insulation is weakened or breached by pinholes caused by either improper handling or small meteoroid and orbital debris strikes. Because electrodynamic tethers are typically long, they have a high probability of these impacts. The particles, which strike the tether, may not have sufficient size to severe the tether, but they can easily penetrate the tether insulation producing a plasma discharge to the ambient plasma. Samples of both the ProSEDS tether transition region and the insulated tether section with various size of pinholes were placed into the MSFC plasma chamber and biased to typical ProSEDS open circuit tether potentials (-500 V to -1600 V). The results of the testing showed that the transition region of the tether (i.e. the triple point) arced to the ambient plasma at -900 V, and the tethers damaged by a pinhole or simulated debris strike arced to the plasma between -700 V and -900 V. Specific design steps were taken to eliminate the triple point issue in the ProSEDS tether design and make it ready for flight. To reduce the pinhole arcing risk, ProSEDS mission operations were changed to eliminate the high negative potential on the insulated tether. The results of the testing campaign and the design changes implemented to ensure a successful flight are described.

  15. Plasma Interactions with a Negative Biased Electrodynamic Tether

    NASA Technical Reports Server (NTRS)

    Vaughn, Jason A.; Welzyn, Ken J.; Curtis, Leslie

    2003-01-01

    The ProSEDS conductive tether design incorporates two distinct types of tethers from a plasma interaction viewpoint. The 200 m closest to the Delta 11 spacecraft is insulated from the plasma, and the remaining 5000 m is semi-bare. This latter portion is semi-bare because it has a conductive coating applied to the wires to permit electron collection while also regulating the overall tether temperature. Because the tether possesses these two distinct types of tethers, a transition point exists between the two types that form a triple point with the space plasma. Insulated tethers can suffer from a second plasma interaction if the insulation is weakened or breached, such as by pinholes caused by small particle debris strikes. Because electrodynamic tethers are typically long, they have a high probability of such impacts. These impacting particles may not be of sufficient size to severe the tether, but they can easily be of sufficient size to damage the tether insulation. Samples of both the ProSEDS tether transition region and the insulated tether section (with various degrees of pinhole damage) were placed into the MSFC plasma chamber and biased to typical ProSEDS open circuit tether potentials (-500 V to -1600 V). The results of the testing showed that the transition region of the tether (i.e. the triple point) arced and burned the tether in two at -900 V, and the damaged insulated sections arced and burned in two between -1000 V and -1600, depending on the pinhole damage geometry. tether design and make the tether ready for flight. To reduce the pinhole arcing risk, ProSEDS mission operations were changed to eliminate the negative potential on the tether. The results of the testing campaign and the design changes implemented to ensure a successful flight will be described.

  16. Electrodynamic-tether time-domain reflectometer for analyzing tether faults and degradation

    NASA Astrophysics Data System (ADS)

    Bilén, Sven G.; Gilchrist, Brian E.

    2001-02-01

    We propose using time-domain-reflectometry (TDR) systems to locate and track faults along electrodynamic tether (EDT) systems. Inclusion of a TDR on long-duration EDT missions would facilitate tracking of the expected performance degradation due to faults caused by hazards such as micrometeors. The TDR technique has long been an effective tool for determining the location of loads and faults along common transmission lines (TLs) such as coaxial cables. Also sometimes known as pulse reflectometry, TDR works by sending an impulse down a TL and recording the reflected energy as a function of time. Measurement of the reflected TDR waveform provides insight into the physical structure of the TL and any loads, i.e., faults, along its length. In addition, the delay between launched and reflected signals determines the location of the load or fault. Hence, the TDR technique requires knowledge of the propagation characteristics of the TL under test. To examine the feasibility of extending the technique to EDTs we use a previously developed model for the tether transmission line. This model has temporal, and hence spatial, limitations, which may be overcome with enhancements to the tether TL model. We present some general parameters governing the development of such a tether TDR system as well as computer simulations of the TDR system's response. .

  17. System engineering study of electrodynamic tether as a spaceborne generator and radiator of electromagnetic waves in the ULF/ELF frequency band

    NASA Technical Reports Server (NTRS)

    Estes, Robert D.

    1987-01-01

    An electrodynamic tether deployed from a satellite in low-Earth orbit can perform, if properly instrumented, as a partially self-powered generator of electromagnetic waves in the ULF/ELF band, potentially at power levels high enough to be of practical use. Two basic problems are examined. The first is that of the level of wave power that the system can be expected to generate in the ULF/ELF radiation band. The second major question is whether an electrodynamic tethered satellite system for transmitting waves can be made partially self-powering so that power requirements for drag compensation can be met within economical constraints of mass, cost, and complexity. The theoretical developments and the system applications study are presented. The basic design criteria, the drag-compensation method, the effects on the propagation paths from orbit to Earth surface of high-altitude nuclear debris patches, and the estimate of masses and sizes are covered. An outline of recommended analytical work, to be performed as a follow-on to the present study, is contained.

  18. Exploration of the Galilean Moons using Electrodynamic Tethers for Propellantless Maneuvers and Self-Powering

    NASA Astrophysics Data System (ADS)

    Lorenzini, E. C.; Curreli, D.; Zanutto, D.

    2010-01-01

    Recent studies have demonstrated the benefits of using electrodynamic tethers (EDT) for the exploration of the inner region of the Jovian system. Intense planetary magnetic field and reasonable environmental plasma density make the electrodynamic interaction of the conductive tether with the plasmasphere strong. The interaction is responsible for a Lorentz force that can be conveniently used for propellantless maneuvers and extraction of electrical power for on board use. Jupiter and the four Galilean Moons represent an exceptional gravitational environment for the study of the orbital dynamics of an EDT. The dynamics of such a system was analyzed using a 3-body model, consisting of the planet plus one of its moons (Io in this work) and the EDT itself. New and interesting features appear, like for example the possibility to place the tether in equilibrium with respect to a frame co-rotating with the moon at points that do not coincide with the classical Lagrangian points for non-null electrodynamic forces.

  19. Electrodynamic Tether Operations beyond the Ionosphere in the Low-Density Magnetosphere

    NASA Technical Reports Server (NTRS)

    Stone, Nobie H.

    2007-01-01

    In the classical concept for the operation of electrodynamic tethers in space, a voltage is generated across the tether, either by the tether's orbital motion through the earth's planetary magnetic field or by a power supply; electrons are then collected from the ionospheric plasma at the positive pole; actively emitted back into space at the negative pole; and the circuit is closed by currents driven through the ambient conducting ionosphere. This concept has been proven to work in space by the Tethered Satellite System TSS-1 and TSS-1R Space Shuttle missions; and the Plasma Motor-Generator (PMG) tether flight experiment. However, it limits electrodynamic tether operations to the F-region of the ionosphere where the plasma density is sufficient to conduct the required currents--in other words, between altitudes of approximately 200 to 1000 km in sunlight. In the earth's shadow, the ionospheric density drops precipitously and tether operations, using the above approach, are not effective--even within this altitude range. There are numerous missions that require in-space propulsion in the Earth's shadow and/or outside of the above altitude range. This paper will, therefore, present the fundamentals of a concept that would allow electrodynamic tethers to operate almost anywhere within the magnetosphere, the region of space containing the earth's planetary magnetic field. In other words, because operations would be virtually independent of any ambient plasma, the range of electrodynamic operations would be extended into the earth's shadow and out to synchronous orbit--forty times the present operational range. The key to this concept is the active generation of plasma at each pole of the tether so that current generation ,does not depend on the conductivity of the ambient ionosphere. Arguments will be presented, based on ,existing flight data, which shed light on the behavior of charge emissions in space and show the plausibility of the concept.

  20. The investigation of tethered satellite system dynamics

    NASA Technical Reports Server (NTRS)

    Lorenzini, E.

    1984-01-01

    Tethered satellite system (TSS) dynamics were studied. The dynamic response of the TSS during the entire stationkeeping phase for the first electrodynamic mission was investigated. An out of plane swing amplitude and the tether's bowing were observed. The dynamics of the slack tether was studied and computer code, SLACK2, was improved both in capabilities and computational speed. Speed hazard related to tether breakage or plasma contactor failure was examined. Preliminary values of the potential difference after the failure and of the drop of the electric field along the tether axis have been computed. The update of the satellite rotational dynamics model is initiated.

  1. Benefits and risks of using electrodynamic tethers to de-orbit spacecraft

    NASA Astrophysics Data System (ADS)

    Pardini, Carmen; Hanada, Toshiya; Krisko, Paula H.

    2009-03-01

    By using electrodynamic drag to greatly increase the orbital decay rate, an electrodynamic space tether can remove spent or dysfunctional spacecraft from low Earth orbit (LEO) rapidly and safely. Moreover, the low mass requirements of such tether devices make them highly advantageous compared to conventional rocket-based de-orbit systems. However, a tether system is much more vulnerable to space debris impacts than a typical spacecraft and its design must be proved to be safe up to a certain confidence level before being adopted for potential applications. To assess space debris related concerns, in March 2001 a new task (Action Item 19.1) on the "Potential Benefits and Risks of Using Electrodynamic Tethers for End-of-life De-orbit of LEO Spacecraft" was defined by the Inter-Agency Space Debris Coordination Committee (IADC). Two tests were proposed to compute the fatal impact rate of meteoroids and orbital debris on space tethers in circular orbits, at different altitudes and inclinations, as a function of the tether diameter to assess the survival probability of an electrodynamic tether system during typical de-orbiting missions. IADC members from three agencies, the Italian Space Agency (ASI), the Japan Aerospace Exploration Agency (JAXA) and the US National Aeronautics and Space Administration (NASA), participated in the study and different computational approaches were specifically developed within the framework of the IADC task. This paper summarizes the content of the IADC AI 19.1 Final Report. In particular, it introduces the potential benefits and risks of using tethers in space, it describes the assumptions made in the study plan, it compares and discusses the results obtained by ASI, JAXA and NASA for the two tests proposed. Some general conclusions and recommendations are finally extrapolated from this massive and intensive piece of research.

  2. Command Generation and Control of Momentum Exchange Electrodynamic Reboost Tethered Satellite

    NASA Technical Reports Server (NTRS)

    Robertson, Michael J.

    2005-01-01

    The research completed for this NASA Graduate Student Research Program Fellowship sought to enhance the current state-of-the-art dynamic models and control laws for Momentum Exchange Electrodynamic Reboost satellite systems by utilizing command generation, specifically Input Shaping. The precise control of tethered spacecraft with flexible appendages is extremely difficult. The complexity is magnified many times when the satellite must interact with other satellites as in a momentum exchange via a tether. The Momentum Exchange Electronic Reboost Tether (MXER) concept encapsulates all of these challenging tasks [l]. Input Shaping is a command generation technique that allows flexible spacecraft to move without inducing residual vibration [2], limit transient deflection [3] and utilize fuel-efficient actuation [4]. Input shaping is implemented by convolving a sequence of impulses, known as the input shaper, with a desired system command to produce a shaped input that is then used to drive the system. This process is demonstrated in Figure 1. The shaped command is then use to drive the system without residual vibration while meeting many other performance specifications. The completed work developed tether control algorithms for retrieval. A simple model of the tether response has been developed and command shaping was implemented to minimize unwanted dynamics. A model of a flexible electrodynamic tether has been developed to investigate the tether s response during reboost. Command shaping techniques have been developed to eliminate the tether oscillations and reduce the tether s deflection to pre-specified levels during reboost. Additionally, a model for the spin-up of a tethered system was developed. This model was used in determining the parameters for optimization the resulting angular velocity.

  3. 2006 Status of the Momentum eXchange Electrodynamic Re-Boost (MXER) Tether Development

    NASA Technical Reports Server (NTRS)

    Bonometti, Joseph A.; Sorensen, Kirk F.; Dankanich, John W.; Frame, Kyle L.

    2006-01-01

    The MXER Tether technology development is a high-payoff/high-risk investment area within the NASA In-Space Propulsion Technology (ISPT) Program. The ISPT program is managed by the NASA Headquarters Science Mission Directorate and implemented by the Marshall Space Flight Center in Huntsville, Alabama. The MXER concept was identified and competitively ranked within NASA's comprehensive Integrated In-Space Transportation Plan (IISTP); an agency-wide technology assessment activity. The objective of the MXER tether project within ISPT is to advance the technological maturation level for the MXER system, and its subsystems, as well as other space and terrestrial tether applications. Recent hardware efforts have focused on the manufacturability of space-survivable high-strength tether material and coatings, high-current electrodynamic tether, lightweight catch mechanism, high-accuracy propagator/predictor code, and efficient electron collection/current generation. Significant technical progress has been achieved with modest ISPT funding to the extent that MXER has evolved to a well-characterized system with greater capability as the design has been matured. Synergistic efforts in high-current electrodynamic tethers and efficient electron collection/current generation have been made possible through SBIR and STTR support. The entire development endeavor was orchestrated as a collaborative team effort across multiple individual contracts and has established a solid technology resource base, which permits a wide variety of future space cable/tether applications to be realized.

  4. Plasma issues associated with the use of electrodynamic tethers

    NASA Technical Reports Server (NTRS)

    Hastings, D. E.

    1986-01-01

    The use of an electrodynamic tether to generate power or thrust on the space station raises important plasma issues associted with the current flow. In addition to the issue of current closure through the space station, high power tethers (equal to or greater than tens of kilowatts) require the use of plasma contactors to enhance the current flow. They will generate large amounts of electrostatic turbulence in the vicinity of the space station. This is because the contactors work best when a large amount of current driven turbulence is excited. Current work is reviewed and future directions suggested.

  5. Applications of the Electrodynamic Tether to Interstellar Travel

    NASA Technical Reports Server (NTRS)

    Matloff, Gregory L.; Johnson, Les

    2005-01-01

    After considering relevant properties of the local interstellar medium and defining a sample interstellar mission, this paper considers possible interstellar applications of the electrodynamic tether, or EDT. These include use of the EDT to provide on-board power and affect trajectory modifications and direct application of the EDT to starship acceleration. It is demonstrated that comparatively modest EDTs can provide substantial quantities of on-board power, if combined with a large-area electron-collection device such as the Cassenti toroidal-field ramscoop. More substantial tethers can be used to accomplish large-radius thrustless turns. Direct application of the EDT to starship acceleration is apparently infeasible.

  6. The investigation of tethered satellite system dynamics

    NASA Technical Reports Server (NTRS)

    Lorenzini, E.

    1985-01-01

    Progress in tethered satellite system dynamics research is reported. A retrieval rate control law with no angular feedback to investigate the system's dynamic response was studied. The initial conditions for the computer code which simulates the satellite's rotational dynamics were extended to a generic orbit. The model of the satellite thrusters was modified to simulate a pulsed thrust, by making the SKYHOOK integrator suitable for dealing with delta functions without loosing computational efficiency. Tether breaks were simulated with the high resolution computer code SLACK3. Shuttle's maneuvers were tested. The electric potential around a severed conductive tether with insulator, in the case of a tether breakage at 20 km from the Shuttle, was computed. The electrodynamic hazards due to the breakage of the TSS electrodynamic tether in a plasma are evaluated.

  7. The Momentum-eXchange/Electrodynamic Reboost (MXER) Tether Concept

    NASA Astrophysics Data System (ADS)

    Sorenson, K. F.

    2004-12-01

    Within NASA's In-Space Propulsion Technology Projects Office exists Emerging Propulsion Technologies (EPT) Investment Area that is advancing emerging propulsion concepts that have potential to lower the cost of space transportation, enable new missions, and/or increase the payload capability. The current, primary investment of EPT is the Momentum-eXchange/Electrodynamic Reboost (MXER) tether concept. The MXER tether is a long, rotating cable in an elliptical Earth orbit whose rapid rotation allows it to catch a payload in a low Earth orbit and throw it to a high-energy orbit. The orbital energy transferred by the MXER tether to the payload is restored to the tether via electrodynamic tether propulsion. This technique uses solar power to drive electrical current collected from the ionosphere through the tether, resulting in a magnetic interaction with the terrestrial field. Since the Earth itself serves as the reaction mass, the thrust force is generated without propellant, and allows the MXER facility to be repeatedly reused without resupply. Essentially, the MXER facility is a `propellantless' upper stage that could assist nearly every mission going beyond low Earth orbit. Payloads to interplanetary destinations would especially benefit from the boost provided by the MXER facility, resulting in launch vehicle cost reductions, increased payload fractions, and more frequent mission opportunities. Some of the benefits to space exploration include: (1) Multi-use, in-space, `propellantless' infrastructure, (2) Useable by essentially all missions beyond LEO, (3) Lowers overall mission costs and/or enables larger payloads, (4) ``Panama Canal" of space transportation, (5) A spiral development for future generations, (6) Readily scales up or down, (7) Future transportation to and from Lunar surface.

  8. Application of the NASCAP Spacecraft Simulation Tool to Investigate Electrodynamic Tether Current Collection in LEO

    NASA Technical Reports Server (NTRS)

    Adams, Mitzi; HabashKrause, Linda

    2012-01-01

    Recent interest in using electrodynamic tethers (EDTs) for orbital maneuvering in Low Earth Orbit (LEO) has prompted the development of the Marshall ElectroDynamic Tether Orbit Propagator (MEDTOP) model. The model is comprised of several modules which address various aspects of EDT propulsion, including calculation of state vectors using a standard orbit propagator (e.g., J2), an atmospheric drag model, realistic ionospheric and magnetic field models, space weather effects, and tether librations. The natural electromotive force (EMF) attained during a radially-aligned conductive tether results in electrons flowing down the tether and accumulating on the lower-altitude spacecraft. The energy that drives this EMF is sourced from the orbital energy of the system; thus, EDTs are often proposed as de-orbiting systems. However, when the current is reversed using satellite charged particle sources, then propulsion is possible. One of the most difficult challenges of the modeling effort is to ascertain the equivalent circuit between the spacecraft and the ionospheric plasma. The present study investigates the use of the NASA Charging Analyzer Program (NASCAP) to calculate currents to and from the tethered satellites and the ionospheric plasma. NASCAP is a sophisticated set of computational tools to model the surface charging of three-dimensional (3D) spacecraft surfaces in a time-varying space environment. The model's surface is tessellated into a collection of facets, and NASCAP calculates currents and potentials for each one. Additionally, NASCAP provides for the construction of one or more nested grids to calculate space potential and time-varying electric fields. This provides for the capability to track individual particles orbits, to model charged particle wakes, and to incorporate external charged particle sources. With this study, we have developed a model of calculating currents incident onto an electrodynamic tethered satellite system, and first results are shown

  9. System engineering study of electrodynamic tether as a spaceborne generator and radiator of electromagnetic waves in the ULF/ELF frequency band

    NASA Technical Reports Server (NTRS)

    Estes, R. D.; Grossi, M. D.; Lorenzini, E. C.

    1986-01-01

    The transmission and generation by orbiting tethered satellite systems of information carrying electromagnetic waves in the ULF/ELF frequency band to the Earth at suitably high signal intensities was examined and the system maintaining these intensities in their orbits for long periods of time without excessive onboard power requirements was investigated. The injection quantity power into electromagnetic waves as a function of system parameters such as tether length and orbital height was estimated. The basic equations needed to evaluate alternataing current tethered systems for external energy requirements are presented. The energy equations to tethered systems with various lengths, tether resistances, and radiation resistances, operating at different current values are applied. Radiation resistance as a function of tether length and orbital height is discussed. It is found that ULF/ELF continuously radiating systems could be maintained in orbit with moderate power requirements. The effect of tether length on the power going into electromagnetic waves and whether a single or dual tether system is preferable for the self-driven mode is discussed. It is concluded that the single tether system is preferable over the dual system.

  10. Investigation of electrodynamic stabilization and control of long orbiting tethers

    NASA Technical Reports Server (NTRS)

    Colombo, G.; Arnold, D.

    1984-01-01

    The state-of-the-art in tether modelling among participants in the Tethered Satellite System (TSS) Program, the slack tether and its behavior, and certain advanced applications of the tether to problems in orbital mechanics are identified. The features and applications of the TSS software set are reviewed. Modelling the slack tether analytically with as many as 50 mass points and the application of this new model to a study of the behavior of a broken tether near the Shuttle are described. A reel control algorithm developed by SAO and examples of its use are described, including an example which also demonstrates the use of the tether in transferring a heavy payload from a low-orbiting Shuttle to a high circular orbit. Capture of a low-orbiting payload by a Space Station in high circular orbit is described. Energy transfer within a dumbbell-type spacecraft by cyclical reeling operations or gravitational effects on the natural elasticity of the connecting tether, it is shown, can circularize the orbit of the spacecraft.

  11. Practicality of using a Tether for electrodynamic reboost of the International Space Station

    NASA Astrophysics Data System (ADS)

    Blumer, John H.; Donahue, Benjamin B.; Bangham, Michal E.

    2001-02-01

    ElectroDynamic (ED) Tethers can generate continuous low thrust in a low Earth orbit. An induced current running through the length of the tether reacts with the geomagnetic field to produce thrust. The amount of thrust scales with tether length and current. The International Space Station (ISS) requires periodic reboost to maintain an approximately circular orbit above the Earth. The baseline reboost method is a traditional bi-propellant rocket thruster and tankage system which must to be refueled via Soyuz/Progress or other launch vehicle. The estimated propellant costs associated with keeping ISS in the designated orbit over a 10-year life have been extremely high. The ED Tether would draw energy from the renewable ISS Solar Array electrical power system. Propulsion requirements for ISS vary depending on solar wind and other conditions. It is projected that a ED Tether could provide the majority of the required reboost thrust for ISS for a nominal solar year. For above nominal solar wind years the ISS would have to use the rocket reboost system, but at a greatly reduced level. Thus resulting in substantial cost savings, via the reduction in the number of Earth-to-orbit launch vehicle flights to the ISS that must bring reboost propellant. However, the purposes of this paper is to further previous research on an ISS ED Tether and examine the operational and technical issues working against using a ED Tether on ISS. Issues such as Shuttle rendezvous and flight path concerns raise serious safety concerns and restrictions on tether use. Tether issues such as tether librations and off angle thrust raise concerns about impacts to microgravity payloads and the long-term effect on ISS orbital path and inclination. Operational issues such as peak power available to an ED Tether and allowable duty cycle may impose severe restrictions on tether design and ultimately limit the practicality of an ED Tether on ISS. Thus while at first glance the cost numbers appear to be

  12. Grid Sphere Electrodes used for Current Collection at the Positive Pole of Electrodynamic Tethers

    NASA Technical Reports Server (NTRS)

    Stone, N. H.; Moore, J. D.

    2004-01-01

    The generation of either electrical power or propulsive thrust with an electrodynamic tether system necessarily depends on driving a return current through the system's ambient space plasma environment. An electrical connection is, therefore, required between the plasma and each end of the tether. The voltage required to drive current through the system is derived either from the orbital motion of the conducting tether through the magnetic field of the Earth, or from a high-voltage power supply that taps into an external energy source (e.g., the sun). In either case, one end of the tether will receive a positive bias. This positive bias, between the tether and the ambient plasma, allows electrons to be collected effectively with a simple, passive electrode. Passive electrode contactors offer several important advantages, including simplification of the upper end-body design and operations, minimization of system mass, and an increase of system reliability and robustness. A preliminary analysis of an inflatable Grid-Sphere end-body concept is presented that is interesting because of the potential for collecting arbitrarily large currents independent of tether length, while the device has the physical characteristics of a high area-to-mass ratio, a low drag coefficient, and simplicity. In particular, we will discuss the physics of current collection by a biased Grid-Sphere and the present state-of-the-art of materials, attainable area-to-mass ratios, and deployment techniques.

  13. From the Rocket Equation to Maxwell's Equations: Electrodynamic Tether Propulsion Nears Space Test

    NASA Technical Reports Server (NTRS)

    Johnson, Les; Estes, Robert

    1999-01-01

    The US space program is facing a growing challenge to its decades-long, global leadership position, as current launch costs consume valuable resources and limit achievements in science, exploration, and commercial development. More than 40% of projected launches over the next 10 years have payloads with intended destinations beyond low-Earth orbit. Therefore, more cost-effective upper stages and on-board propulsion systems are critical elements in reducing total space transportation costs. A new type of space propulsion, using electrodynamic tethers, may be capable of performing multiple sequential missions without resupply and have a potential usable lifetime of several years. They may provide an in-space infrastructure that has a very low life cycle cost and greatly enhanced mission flexibility, thus supporting the goal of reducing the cost of access to space. Electrodynamic tether thrusters work by virtue of the force the Earth's magnetic field exerts on a wire carrying an electrical current. The effect is the basis for electric motors and generators. The Propulsive Small Expendable Deployer System (ProSEDS) experiment, planned for launch in the summer of 2000, will demonstrate the use electrodynamic tether thrust by lowering the altitude of a Delta-H rocket's upper stage on which it will be flying. Applications of the technology include a passive deorbit system for spacecraft at their end-of-life, reusable Orbit Transfer Vehicles, propellantless reboost of the International Space Station, and propulsion and power generation for future missions to Jupiter.

  14. Tethers

    NASA Technical Reports Server (NTRS)

    Cutler, Andrew Hall; Carroll, Joseph A.

    1992-01-01

    A tether of sufficient strength, capable of being lengthened or shortened and having appropriate apparatuses for capturing and releasing bodies at its ends, may be useful in propulsion applications. For example, a tether could allow rendezvous between spacecraft in substantially different orbits without using propellant. A tether could also allow co-orbiting spacecraft to exchange momentum and separate. Thus, a reentering spacecraft (such as the Shuttle) could give its momentum to one remaining on orbit (such as the space station). Similarly, a tether facility could gain momentum from a high I(sub sp)/low thrust mechanism (which could be an electrodynamics tether) and transfer than momentum by means of a tether to payloads headed for many different orbits. Such a facility would, in effect, combine high I(sub sp) with high thrust, although only briefly. An electrodynamic tether could propel a satellite from its launch inclination to a higher or lower inclination. Tethers could also allow samples to be taken from bodies such as the Moon. Three types of tether operations are illustrated. The following topics are discussed: (1) tether characteristics; (2) tether propulsion methods--basics, via momentum transfer, and electrodynamic tether propulsion; and (3) their use in planetary exploration.

  15. The TSS-1R Electrodynamic Tether Experiment: Scientific and Technological Results

    NASA Technical Reports Server (NTRS)

    Stone, Nobie H.; Raitt, John

    1998-01-01

    The bi-national, US-Italian, Tethered Satellite System (TSS) program was designed to provide a unique opportunity to explore certain space plasma- electrodynamic processes and the orbital mechanics of a gravity-gradient stabilized system of two satellites linked by a long conducting tether. The second flight, TSS-LR, was launched February 22, 1996 on STS-75 and satellite deployment began at MET 3/00:27. A unique data set was obtained over the next five hours, as the tether was deployed to a length of 19695 meters, which has allowed significant science to be accomplished. This presentation will focus on electrodynamic processes generated by the tether--in particular, the collection of electrical current from the ionospheric plasma. Of particular significance is an apparent transition of the physics of current collection when the potential of the collecting body becomes greater than the ram energy of the ionospheric atomic oxygen ions. Previous theoretical models of current collection were electrostatic--assuming that the orbital motion of the system, which is highly subsonic with respect to electron thermal motion, was un- important. This may still be acceptable for the case of relatively slow-moving sounding rockets. However, the TSS-LR results show that motion relative to the plasma must be accounted for in orbiting systems.

  16. Dynamics analysis of electrodynamic satellite tethers. Equations of motion and numerical solution algorithms for the tether

    NASA Technical Reports Server (NTRS)

    Nacozy, P. E.

    1984-01-01

    The equations of motion are developed for a perfectly flexible, inelastic tether with a satellite at its extremity. The tether is attached to a space vehicle in orbit. The tether is allowed to possess electrical conductivity. A numerical solution algorithm to provide the motion of the tether and satellite system is presented. The resulting differential equations can be solved by various existing standard numerical integration computer programs. The resulting differential equations allow the introduction of approximations that can lead to analytical, approximate general solutions. The differential equations allow more dynamical insight of the motion.

  17. Tethered Satellite System (TSS) core equipment

    NASA Technical Reports Server (NTRS)

    Bonifazi, C.

    1986-01-01

    To date, three Tethered Satellite System (TSS) missions of the Italian provided scientific satellite orbiting in the ionosphere connected to U.S. Space Shuttle is foreseen. The first mission will use an electrically conductive tether of 20 km deployed upward from the orbiter flying at 300 km altitude. This mission will allow investigation of the TSS electrodynamic interaction with the ionosphere due to the high voltage induced across the two terminators of the system during its motion throughout the geomagnetic field. The second mission will use a dielectric tether of 100 km deployed downward from the Orbiter flying at 230 km altitude. Tethered-vehicle access to altitude as low as 120 to 150 km from the Orbiter would permit direct long term observation of phenomena in the lower thermosphere and determination of other dynamical physical processes. The third mission would use the same configuration of the first electrodynamic mission with the complete Core Equipment. Study of power generation by tethered systems would be possible by operating the Core Equipment in the inverted current mode. This mode of operation would allow ion current collection upon the TSS satellite by controlling its potential with respect to the ambient ionospheric plasma. The main requirements of the Core Equipment configuration to date foreseen for the first TSS electrodynamic mission is described. Besides the Core Equipment purposes, its hardware and operational sub-modes of operation are described.

  18. Proceedings of a Workshop on the Applications of Tethers in Space, Volume 1

    NASA Astrophysics Data System (ADS)

    1983-12-01

    Project overview; tether deployment; satellite system description; tether fundamentals; science applications; electrodynamic interactions; transportation; artificial gravity; and constellations; were described.

  19. Proceedings of a Workshop on the Applications of Tethers in Space, Volume 1

    NASA Technical Reports Server (NTRS)

    1983-01-01

    Project overview; tether deployment; satellite system description; tether fundamentals; science applications; electrodynamic interactions; transportation; artificial gravity; and constellations; were described.

  20. Plasma motor generator tether system for orbit reboost

    NASA Technical Reports Server (NTRS)

    Hulkower, Neal D.; Rusch, Roger J.

    1988-01-01

    This paper describes a comprehensive study of an electrodynamic tether used as a Plasma Motor Generator (PMG). The paper summarizes the work performed in the study and includes: (1) a detailed design of a 2 kW PMG tether system to be used for orbit reboost, (2) the selection of the Orbiting Maneuvering Vehicle (OMV) and the European Retrievable Carrier (EURECA) as the primary candidate spacecraft to host the experimental system, (3) analysis of the integration of the PMG tether system with these two spacecraft, (4) the simulation of the deployment of the tether, and (5) an engineering design and development plan leading to a flight demonstration of this PMG tether.

  1. Applications of Tethers in Space, Volume 2

    NASA Technical Reports Server (NTRS)

    Cron, A. C. (Compiler)

    1985-01-01

    Topics discussed include tethered satellites, tether deployment, satellite systems, science applications, electrodynamic interactions, transportation applications, artificial gravity, constellations, and technology and testing.

  2. The TSS-1R Electrodynamic Tether Experiment: Scientific and Technological Results

    NASA Technical Reports Server (NTRS)

    Stone, Nobie H.; Raitt, W. J.

    1998-01-01

    The Tethered Satellite System (TSS) program was designed to provide the opportunity to explore certain space plasma-electrodynamic processes (associated with high-voltage bodies and electrical currents in space) and the orbital mechanics of a gravity-gradient stabilized system of two satellites linked by a long conducting tether. A unique data set was obtained during the TSS-1 R mission in which the tether emf and current reached values in excess of 3500 volts and 1 amp, respectively. The insight this has allowed into the current collection process and the physics of high-voltage plasma sheaths is significant. Previous theoretical models of current collection were electro-static assuming that the orbital motion of the system, which is highly sub-sonic with respect to electron thermal motion, was unimportant. This may still be acceptable for the case of relatively slow-moving sounding rockets. However, the TSS-1 R results show that motion relative to the plasma does affect current collection and must be accounted for in orbiting systems.

  3. Tether Transportation System Study

    NASA Technical Reports Server (NTRS)

    Bangham, M. E.; Lorenzini, E.; Vestal, L.

    1998-01-01

    The projected traffic to geostationary earth orbit (GEO) is expected to increase over the next few decades. At the same time, the cost of delivering payloads from the Earth's surface to low earth orbit (LEO) is projected to decrease, thanks in part to the Reusable Launch Vehicle (RLV). A comparable reduction in the cost of delivering payloads from LEO to GEO is sought. The use of in-space tethers, eliminating the requirement for traditional chemical upper stages and thereby reducing the launch mass, has been identified as such an alternative. Spinning tethers are excellent kinetic energy storage devices for providing the large delta vee's required for LEO to GEO transfer. A single-stage system for transferring payloads from LEO to GEO was proposed some years ago. The study results presented here contain the first detailed analyses of this proposal, its extension to a two-stage system, and the likely implementation of the operational system.

  4. Modeling of induced currents from electrodynamic tethers in a laboratory plasma

    NASA Technical Reports Server (NTRS)

    Urrutia, J. M.; Stenzel, R. L.

    1990-01-01

    The presently accepted picture of the current path for electrodynamic tethers envisions a quasi-dc current flow in a 'phantom loop' consisting of the tether, two field-aligned current channels into the ionosphere and a cross-field closing current in the E-layer. Predictions are made on the establishment and maintenance of a current loop in space based on observations of time-dependent currents between tethered electrodes in a large laboratory magnetoplasma. In addition to radiation from the contactors ('whistler wings'), the insulated tether is observed to emit waves (a 'whistler wedge'). The 'wedge' provides closure during loop formation by carrying cross-field polarization currents. Whistler spread within the ray cone leads to overlapping of the current wings not far from the tether hence minimizing the role of the ionospheric closure. Maintenance of the loop requires the continuous emission of whistler waves by the entire tether thereby providing severe radiation losses.

  5. The investigation of tethered satellite system dynamics

    NASA Technical Reports Server (NTRS)

    Lorenzini, E.

    1985-01-01

    The tether control law to retrieve the satellite was modified in order to have a smooth retrieval trajectory of the satellite that minimizes the thruster activation. The satellite thrusters were added to the rotational dynamics computer code and a preliminary control logic was implemented to simulate them during the retrieval maneuver. The high resolution computer code for modelling the three dimensional dynamics of untensioned tether, SLACK3, was made fully operative and a set of computer simulations of possible tether breakages was run. The distribution of the electric field around an electrodynamic tether in vacuo severed at some length from the shuttle was computed with a three dimensional electrodynamic computer code.

  6. Study of certain tether safety issues. Continuation of investigation of electrodynamic stabilization and control of long orbiting tethers, volume 1

    NASA Technical Reports Server (NTRS)

    Colombo, G.; Grossi, M. D.; Arnold, D.

    1982-01-01

    The behavior of long tethers (10-100 km) in space are addressed under two failure situations with potential safety impact: instantaneous jamming of the reel controlling the tether during deployment and cutting of the tether due to a meteor strike or other similar phenomena. Dual and multiple mass point models were used in the SAO SKYHOOK program to determine this behavior. The results of the program runs were verified analytically or by comparison with previously verified results. The study included the effects of tether damping and air drag where appropriate. Most runs were done with the tether system undamped since we believe this best represents the true behavior of the tether. Means for controlling undesirable behavior of the tether, such as viscous dampers in the subsatellite, were also studied.

  7. Near Space Environments: Tethering Systems

    NASA Technical Reports Server (NTRS)

    Lucht, Nolan R.

    2013-01-01

    Near Space Environments, the Rocket University (Rocket U) program dealing with high altitude balloons carrying payloads into the upper earth atmosphere is the field of my project. The tethering from balloon to payload is the specific system I am responsible for. The tethering system includes, the lines that tie the payload to the balloon, as well as, lines that connect payloads together, if they are needed, as well as how to sever the tether to release payloads from the balloon. My objective is to design a tethering system that will carry a payload to any desired altitude and then sever by command at any given point during flight.

  8. Free Re-boost Electrodynamic Tether on the International Space Station

    NASA Technical Reports Server (NTRS)

    Bonometti, Joseph A.; Sorenson, Kirk F.; Jansen, Ralph H.; Dankanich, John W.; Frame, Kyle L.

    2005-01-01

    The International Space Station (ISS) currently experiences significant orbital drag that requires constant make up propulsion or the Station will quickly reenter the Earth's Atmosphere. The reboost propulsion is presently achieved through the firing of hydrazine rockets at the cost of considerable propellant mass. The problem will inevitably grow much worse as station components continue to be assembled, particularly when the full solar panel arrays are deployed. This paper discusses many long established themes on electrodynamic propulsion in the context of Exploration relevance, shows how to couple unique ISS electrical power system characteristics and suggests a way to tremendously impact ISS's sustainability. Besides allowing launch mass and volume presently reserved for reboost propellant to be reallocated for science experiments and other critically needed supplies, there are a series of technology hardware demonstrations steps that can be accomplished on ISS, which are helpful to NASA s Exploration mission. The suggested ElectroDynamic (ED) tether and flywheel approach is distinctive in its use of free energy currently unusable, yet presently available from the existing solar array panels on ISS. The ideas presented are intended to maximize the utility of Station and radically increase orbital safety.

  9. Power and charge dissipation from an electrodynamic tether

    NASA Technical Reports Server (NTRS)

    Hite, Gerald E.

    1987-01-01

    The Plasma Motor-Generator project utilizes the influence of the geomagnetic field on a conductive tether attached to a LEO spacecraft to provide a reversible conversion of orbital energy into electrical energy. The behavior of the current into the ionospheric plasma under the influence of the geomagnetic field is of significant experimental and theoretical interest. Theoretical calculations are reviewed which start from Maxwell's equations and treat the ionospheric plasma as a linear dielectric medium. These calculations show a charge emitting tether moving in a magnetic field will generate electromagnetic waves in the plasma which carry the charge in the direction of the magnetic field. The ratio of the tether's speed to the ion cyclotron frequency which is about 25 m for a LEO is a characteristic length for the phenomena. Whereas for the dimensions of the contact plasma much larger than this value the waves are the conventional Alfven waves, when the dimensions are comparable or smaller, diffraction effects occur similar to those associated with Fresnel diffraction in optics. The power required to excite these waves for a given tether current is used to estimate the impedance associated with this mode of charge dissipation.

  10. Space Station tethered elevator system

    NASA Technical Reports Server (NTRS)

    Haddock, Michael H.; Anderson, Loren A.; Hosterman, K.; Decresie, E.; Miranda, P.; Hamilton, R.

    1989-01-01

    The optimized conceptual engineering design of a space station tethered elevator is presented. The tethered elevator is an unmanned, mobile structure which operates on a ten-kilometer tether spanning the distance between Space Station Freedom and a platform. Its capabilities include providing access to residual gravity levels, remote servicing, and transportation to any point along a tether. The report discusses the potential uses, parameters, and evolution of the spacecraft design. Emphasis is placed on the elevator's structural configuration and three major subsystem designs. First, the design of elevator robotics used to aid in elevator operations and tethered experimentation is presented. Second, the design of drive mechanisms used to propel the vehicle is discussed. Third, the design of an onboard self-sufficient power generation and transmission system is addressed.

  11. Orbital Propagation of Momentum Exchange Tether Systems

    NASA Technical Reports Server (NTRS)

    Westerhoff, John

    2002-01-01

    An advanced concept in in-space transportation currently being studied is the Momentum-Exchange/Electrodynamic Reboost Tether System (MXER). The system acts as a large momentum wheel, imparting a Av to a payload in low earth orbit (LEO) at the expense of its own orbital energy. After throwing a payload, the system reboosts itself using an electrodynamic tether to push against Earth's magnetic field and brings itself back up to an operational orbit to prepare for the next payload. The ability to reboost itself allows for continued reuse of the system without the expenditure of propellants. Considering the cost of lifting propellant from the ,ground to LEO to do the same Av boost at $10000 per pound, the system cuts the launch cost of the payload dramatically, and subsequently, the MXER system pays for itself after a small number of missions.1 One of the technical hurdles to be overcome with the MXER concept is the rendezvous maneuver. The rendezvous window for the capture of the payload is on the order of a few seconds, as opposed to traditional docking maneuvers, which can take as long ets necessary to complete a precise docking. The payload, therefore, must be able to match its orbit to meet up with the capture device on the end of the tether at a specific time and location in the future. In order to be able to determine that location, the MXER system must be numerically propagated forward in time to predict where the capture device will be at that instant. It should be kept in mind that the propagation computation must be done faster than real-time. This study focuses on the efforts to find and/or build the tools necessary to numerically propagate the motion of the MXER system as accurately as possible.

  12. Investigation of EM Emissions by the Electrodynamic Tether, Inclusive of an Observational Program (EMET)

    NASA Technical Reports Server (NTRS)

    Estes, Robert D.

    1998-01-01

    Our TSS-1/R investigation, which we shall refer to as EMET in this report, was an integral part of the effort by the TSS-1/R Investigators' Working Group (IWG) to come to an understanding of the complex interaction between the tethered satellite system and the ionosphere. All of the space-borne experiments were designed to collect data relevant to the local interaction. Only the ground- based experiments, EMET and its Italian counterpart Observations on the Earth's Surface of Electromagnetic Emissions (OESEE), held out any hope of characterizing the long range effects of the interaction. This was to be done by detecting electromagnetic waves generated by the system in the ionosphere, assuming the signal reached the Earth's surface with sufficient amplitude. As the type of plasma waves excited to carry charge away from the charge-exchange regions of the system at each end of the tether is one of the theoretical points about which there is greatest disagreement, a definitive identification of tether-generated waves could mark significant progress in the so-called current closure problem of electrodynamic tethers. Dr. Mario Grossi of the Smithsonian Astrophysical Observatory (SAO) initiated the investigation, and his experience in the field of ULF-ELF waves and their detection was invaluable throughout its course. Rice University had the responsibility of setting up the EMET ULF-VLF ground stations under a subcontract from SAO. Principal Investigator (PI) for the Rice effort was Prof. William E. Gordon, who was primary observer at the Arecibo Observatory during TSS-LR. Dr. Steve Noble handled major day-to-day operations, training, and planning for the ground-based measurements. Dr. James McCoy of NASA JSC, a member of the Mona/Arecibo team, was pilot for the numerous flights ferrying personnel and equipment between Puerto Rico and Mona Island. Final responsibility for the measurements rested with SAO, and the activities of field personnel and SAO investigators were

  13. Preliminary investigation of the electrodynamics of a conducting tether

    NASA Technical Reports Server (NTRS)

    Thompson, W. B.

    1985-01-01

    An introductory study of the properties of an electrically conducting tether flown from the shuttle is presented. Only a single configuration is considered: a vertical conductor moving normally across the Earth's field, connecting the shuttle to a large conducting balloon that passively extracts electrons from the ionosphere. The distortions in the plasma at maximum current collection are described, as are the local and distant wakes. Numerical values are given.

  14. Theoretical investigation of EM wave generation and radiation in the ULF, ELF, and VLF bands by the electrodynamic orbiting tether

    NASA Technical Reports Server (NTRS)

    Estes, Robert D.; Grossi, Mario D.

    1989-01-01

    The problem of electromagnetic wave generation by an electrodynamic tethered satellite system is important both for the ordinary operation of such systems and for their possible application as orbiting transmitters. The tether's ionospheric circuit closure problem is closely linked with the propagation of charge-carrying electromagnetic wave packets away from the tethered system. Work is reported which represents a step towards a solution to the problem that takes into account the effects of boundaries and of vertical variations in plasma density, collision frequencies, and ion species. The theory of Alfen wave packet generation by an electrodynamic tethered system in an infinite plasma medium is reviewed, and brief summary of previous work on the problem is given. The consequences of the presence of the boundaries and the vertical nonuniformity are then examined. One of the most significant new features to emerge when ion-neutral collisions are taken into account is the coupling of the Alfven waves to the fast magnetosonic wave. This latter wave is important, as it may be confined by vertical variations in the Alfven speed to a sort of leaky ionospheric wave guide, the resonances of which could be of great importance to the signal received on the Earth's surface. The infinite medium solution for this case where the (uniform) geomagnetic field makes an arbitrary angle with the vertical is taken as the incident wave-packet. Even without a full solution, a number of conclusions can be drawn, the most important of which may be that the electromagnetic field associated with the operation of a steady-current tethered system will probably be too weak to detect on the Earth's surface, even for large tethered currents. This is due to the total reflection of the incident wave at the atmospheric boundary and the inability of a steady-current tethered system to excite the ionospheric wave-guide. An outline of the approach to the numerical problem is given. The use of

  15. Electrodynamic Tethers. 1: Power Generator in LEO. 2: Thrust for Propulsion and Power Storage

    NASA Technical Reports Server (NTRS)

    Mccoy, J. E.

    1984-01-01

    An electrodynamic tether consists of a long insulated wire in space whose orbital motion cuts across lines of magnetic flux to produce an induce voltage that in typical low orbits averages about 200 v/km. Such a system should be capable of generating substantial electrical power, at the expense of IXB drag acting on its orbital energy. If a reverse current is driven against the induced voltage, the system should act as a motor producing IXB thrust. A reference system was designed, capable of generating 20 KW of power into an electrical load located anywhere along the wire at the expense of 2.6N (20,000 J/sec) drag on the wire. In an ideal system, the conversion between mechanical and electrical energy would reach 100% efficiency. In the actual system part of the 20 KW is lost to internal resistance of the wire, plasma and ionosphere, while the drag force is increased by residual air drag. The 20 KW PMG system as designed is estimated to provide 18.7 KW net power to the load at total drag loss of 20.4 KJ/sec, or an overall efficiency of 92%. Similar systems using heavier wire appear capable of producing power levels in excess of 1 Megawatt at voltages of 2-4 KV, with conversion efficiency between mechanical and electrical power better than 95%. The hollow cathode based system should be readily reversible from generator to motor operation by driving a reverse current using onboard power.

  16. Tethered Satellite System Tip Canister - Thermal design and test

    NASA Technical Reports Server (NTRS)

    Chapter, John J.

    1992-01-01

    The Tethered Satellite System (TSS) is scheduled for launch, on STS-46 in mid-1992. The major mission objective is to investigate electrodynamic phenomena associated with long electrically conductive tether, in the earth orbital environment. A spherical Satellite (1.6-m diameter), remains connected to the Orbiter throughout TSS-1 mission by a conductive tether. The Satellite operates at up to 20 km above the Orbiter during the TSS mission. The Tip Canister (TPC), that is mounted on the end of a 12-m retractable boom, contains mechanisms that control and monitor tether movement. The TPC is an independent thermal system from the base 'Deployer/Spacelab Pallet'. This paper presents the TPC thermal design verification approach that includes a description of thermal design and thermal balance testing. Flight TPC temperature predictions are also presented.

  17. Survivability to Hypervelocity Impacts of Electrodynamic Tape Tethers for Deorbiting Spacecraft in LEO

    NASA Astrophysics Data System (ADS)

    Francesconi, A.; Giacomuzzo, C.; Lorenzini, E. C.

    2013-08-01

    This paper reports the results of 16 hypervelocity impact experiments on a composite flat electrodynamic tether for LEO spacecraft end-of-life deorbiting. The system is being developed within the EU FP7 BETs program. Impact tests were carried out at CISAS impact facility, with the aim of deriving failure equations that include the impact angle dependence up to grazing incidence. Experiments were realised with 1.5 and 2.3 mm aluminium spheres, at velocities between 3 and 5 km/s and impact angle from 0° to 90° from the tape normal. After a preliminary post-impact inspection of the target, the damage extension on the tape was evaluated using an automatic image processing technique. Ballistic limit equations were developed in the experimental range using a procedure that allows to estimate the uncertainty in the failure predictions starting from the measurement of the damage area. Experiments showed that the impact damage is very close to the projectile size in case of normal impact, while it increases significantly at highly oblique impact angles.

  18. The Tethered Satellite System: Scientific and Technological Results

    NASA Technical Reports Server (NTRS)

    Stone, Nobie H.

    1997-01-01

    The bi-national, US-Italian, Tethered Satellite System (TSS) program was designed to provide a unique opportunity to explore certain space plasma- electrodynamic processes and the orbital mechanics of a gravity-gradient stabilized system of two satellites linked by a long conducting tether. The second flight, TSS-LR, was launched February 22, 1996 on STS-75 and satellite deployment began at MET 3/00:27. A unique data set was obtained over the next five hours as the tether was deployed to a length of 19695 meters, which has allowed significant science to be accomplished. This presentation will focus on results from the TSS-LR mission that are most important to the future technological applications of electrodynamic tethers in space - in particular, the current collection process. Of particular significance is an apparent transition of the physics of current collection when the potential of the collecting body becomes greater than the ram energy of the ionospheric atomic oxygen ions. Previous theoretical models of current collection were electro- static - assuming that the orbital motion of the system, which is highly sub-sonic with respect to electron thermal motion, was unimportant. This may still be acceptable for the case of relatively slow-moving sounding rockets. However, the TSS-LR results show that motion relative to the plasma must be accounted for in orbiting systems.

  19. Three-dimensional currents of electrodynamic tethers obtained from laboratory models

    SciTech Connect

    Urrutia, J.M.; Stenzel, R.L.; Rousculp, C.L.

    1994-03-01

    Magnetic probe measurements in three dimensions (greater than 15,000 positions) and time in a large laboratory plasma (n(sub e) greater than or equal to 10(exp 11)/cc, kTe greater than or equal to 1eV, B(sub 0) = 20 G, 1 m diam. x 2.5 m length) reveal the plasma currents J = del(vector differential operator) x B/mu(sub 0) excited by a pulsed (delta-t = 100 ns), stationary, tethered pair of electrodes (approximately equals 1 cm diam., 20 cm spacing perpendicular to B(sub 0)). The plasma currents for a moving, dc-current carrying electrodynamic tether are obtained by a superposition of delayed pulses emitted at successively displaced tether positions. The transient plasma currents are carried by low-frequency whistlers instead of Alfven waves and form a 3D wing structure but no long phantom loop due to cross-field Hall current shunting.

  20. Three-dimensional currents of electrodynamic tethers obtained from laboratory models

    NASA Technical Reports Server (NTRS)

    Urrutia, J. M.; Stenzel, R. L.; Rousculp, C. L.

    1994-01-01

    Magnetic probe measurements in three dimensions (greater than 15,000 positions) and time in a large laboratory plasma (n(sub e) greater than or equal to 10(exp 11)/cc, kTe greater than or equal to 1eV, B(sub 0) = 20 G, 1 m diam. x 2.5 m length) reveal the plasma currents J = del(vector differential operator) x B/mu(sub 0) excited by a pulsed (delta-t = 100 ns), stationary, tethered pair of electrodes (approximately equals 1 cm diam., 20 cm spacing perpendicular to B(sub 0)). The plasma currents for a moving, dc-current carrying electrodynamic tether are obtained by a superposition of delayed pulses emitted at successively displaced tether positions. The transient plasma currents are carried by low-frequency whistlers instead of Alfven waves and form a 3D wing structure but no long phantom loop due to cross-field Hall current shunting.

  1. Theoretical investigation of EM wave generation and radiation in the ULF, ELF and VLF bands by the electrodynamic orbiting tether

    NASA Technical Reports Server (NTRS)

    Estes, Robert D.

    1988-01-01

    The goal is to extend the previous analysis of electromagnetic wave generation by an electrodynamic tethered satellite system to a more realistic model that includes the effects on wave propagation and reflection to the boundaries between ionosphere, atmosphere, and earth. One of the major activities was searching the scientific literature for publications that might be relevant to the problem. The software developed as SAO to follow the path of waves along field lines through the ionosphere to the atmosphere starting from an arbitary position in the atmosphere is described. Some preliminary results are presented from applying the code to the location of wave reception hot spots on the earth's surface for satellites operating at 300 and 600 km altitudes. A generalization of the Alfven wing analysis is presented to allow for arbitrary angles between the velocity vector, geomagnetic field, and the veritcal. This will be utilized in the modeling of the problem with boundaries included.

  2. Tethered Satellite System (TSS-1R)-Post Flight (STS-75) Engineering Performance Report

    NASA Technical Reports Server (NTRS)

    Lavoie, Anthony R.

    1996-01-01

    The first mission of the Tethered Satellite deployer was flown onboard Atlantis in 1992 during the Space Transportation System (STS) flight STS-46. Due to a mechanical interference with the level wind mechanism the satellite was only Deployed to 256 m rather than the planned 20,000 m. Other problems were also experienced during the STS-46 flight and several modifications were made to the Deployer and Satellite. STS-75 was a reflight of the Tethered Satellite System 1 (TSS-1) designated as Tethered Satellite System 1 Reflight (TSS-1 R) onboard Columbia. As on STS-46, the TSS payload consisted of the Deployer, the Satellite, 3 cargo bay mounted experiments: Shuttle Electrodynamic Tether System (SETS), Shuttle Potential and Return Electron Experiment (SPREE), Deployer Core Equipment (DCORE) 4 Satellite mounted experiments: Research on Electrodynamics Tether Effects (RETE), Research on Orbital Plasma Electrodynamics (ROPE), Satellite Core Instruments (SCORE), Tether Magnetic Field Experiment (TEMAG) and an aft flight deck camera: Tether Optical Phenomena Experiment (TOP). Following successful pre-launch, launch and pre-deployment orbital operations, the Deployer deployed the Tethered Satellite to 19,695 m at which point the tether broke within the Satellite Deployment Boom (SDB). The planned length for On-Station I (OST1) was 20,700 m The Satellite flew away from the Orbiter with the tether attached. The satellite was "safed" and placed in a limited power mode via the RF link. The Satellite was contacted periodically during overflights of ground stations. Cargo bay science activities continued for the period of time allocated to TSS-1 R operations.

  3. Active Space Debris Removal using European Modified Launch Vehicle Upper Stages Equipped with Electrodynamic Tethers

    NASA Astrophysics Data System (ADS)

    Nasseri, Ali S.; Emanuelli, Matteo; Raval, Siddharth; Turconi, Andrea; Becker, Cristoph

    2013-08-01

    During the past few years, several research programs have assessed the current state and future evolution of the Low Earth Orbit region. These studies indicate that space debris density could reach a critical level such that there will be a continuous increase in the number of debris objects, primarily driven by debris-debris collision activity known as the Kessler effect. This cascade effect can be even more significant when intact objects as dismissed rocket bodies are involved in the collision. The majority of the studies until now have highlighted the urgency for active debris removal in the next years. An Active Debris Removal System (ADRS) is a system capable of approaching the debris object through a close-range rendezvous, establishing physical connection, stabilizing its attitude and finally de-orbiting the debris object using a type of propulsion system in a controlled manoeuvre. In its previous work, this group showed that a modified Fregat (Soyuz FG's 4th stage) or Breeze-M upper stage (Proton-M) launched from Plesetsk (Russian Federation) and equipped with an electro-dynamic tether (EDT) system can be used, after an opportune inclination's change, to de-orbit a Kosmos-3M second stage rocket body while also delivering an acceptable payload to orbit. In this paper, we continue our work on the aforementioned concept, presented at the 2012 Beijing Space Sustainability Conference, by comparing its performance to ADR missions using only chemical propulsion from the upper stage for the far approach and the de-orbiting phase. We will also update the EDT model used in our previous work and highlight some of the methods for creating physical contact with the object. Moreover, we will assess this concept also with European launch vehicles (Vega and Soyuz 2-1A) to remove space debris from space. In addition, the paper will cover some economic aspects, like the cost for the launches' operator in term of payload mass' loss at the launch. The entire debris removal

  4. Current-voltage characteristics of a cathodic plasma contactor with discharge chamber for application in electrodynamic tether propulsion

    NASA Astrophysics Data System (ADS)

    Xie, Kan; Martinez, Rafael A.; Williams, John D.

    2014-04-01

    This paper focuses on the net electron-emission current as a function of bias voltage of a plasma source that is being used as the cathodic element in a bare electrodynamic tether system. An analysis is made that enables an understanding of the basic issues determining the current-voltage (C-V) behaviour. This is important for the efficiency of the electrodynamic tether and for low impedance performance without relying on the properties of space plasma for varying orbital altitudes, inclinations, day-night cycles or the position of the plasma contactor relative to the wake of the spacecraft. The cathodic plasma contactor considered has a cylindrical discharge chamber (10 cm in diameter and ˜11 cm in length) and is driven by a hollow cathode. Experiments and a 1D spherical model are both used to study the contactor's C-V curves. The experiments demonstrate how the cathodic contactor would emit electrons into space for anode voltages in the range of 25-40 V, discharge currents in the range of 1-2.5 A, and low xenon gas flows of 2-4 sccm. Plasma properties are measured and compared with (3 A) and without net electron emission. A study of the dependence of relevant parameters found that the C-V behaviour strongly depends on electron temperature, initial ion energy and ion emission current at the contactor exit. However, it depended only weakly on ambient plasma density. The error in the developed model compared with the experimental C-V curves is within 5% at low electron-emission currents (0-2 A). The external ionization processes and high ion production rate caused by the discharge chamber, which dominate the C-V behaviour at electron-emission currents over 2 A, are further highlighted and discussed.

  5. Tethered Satellite System Contingency Investigation Board

    NASA Technical Reports Server (NTRS)

    1992-01-01

    The Tethered Satellite System (TSS-1) was launched aboard the Space Shuttle Atlantis (STS-46) on July 31, 1992. During the attempted on-orbit operations, the Tethered Satellite System failed to deploy successfully beyond 256 meters. The satellite was retrieved successfully and was returned on August 6, 1992. The National Aeronautics and Space Administration (NASA) Associate Administrator for Space Flight formed the Tethered Satellite System (TSS-1) Contingency Investigation Board on August 12, 1992. The TSS-1 Contingency Investigation Board was asked to review the anomalies which occurred, to determine the probable cause, and to recommend corrective measures to prevent recurrence. The board was supported by the TSS Systems Working group as identified in MSFC-TSS-11-90, 'Tethered Satellite System (TSS) Contingency Plan'. The board identified five anomalies for investigation: initial failure to retract the U2 umbilical; initial failure to flyaway; unplanned tether deployment stop at 179 meters; unplanned tether deployment stop at 256 meters; and failure to move tether in either direction at 224 meters. Initial observations of the returned flight hardware revealed evidence of mechanical interference by a bolt with the level wind mechanism travel as well as a helical shaped wrap of tether which indicated that the tether had been unwound from the reel beyond the travel by the level wind mechanism. Examination of the detailed mission events from flight data and mission logs related to the initial failure to flyaway and the failure to move in either direction at 224 meters, together with known preflight concerns regarding slack tether, focused the assessment of these anomalies on the upper tether control mechanism. After the second meeting, the board requested the working group to complete and validate a detailed integrated mission sequence to focus the fault tree analysis on a stuck U2 umbilical, level wind mechanical interference, and slack tether in upper tether

  6. Electrodynamics panel presentation

    NASA Technical Reports Server (NTRS)

    Mccoy, J.

    1986-01-01

    The Plasma Motor Generator (PMG) concept is explained in detail. The PMG tether systems being used to calculate the estimated performance data is described. The voltage drops and current contact geometries involved in the operation of an electrodynamic tether are displayed illustrating the comparative behavior of hollow cathodes, electron guns, and passive collectors for current coupling into the ionosphere. The basic PMG design involving the massive tether cable with little or no satellite mass at the far end(s) are also described. The Jupiter mission and its use of electrodynamic tethers are given. The need for demonstration experiments is stressed.

  7. 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.

  8. A two-dimensional theory of plasma contactor clouds used in the ionosphere with an electrodynamic tether

    NASA Technical Reports Server (NTRS)

    Hastings, D. E.; Gatsonis, N. A.; Rivas, D. A.

    1988-01-01

    Plasma contactors have been proposed as a means of making good electrical contact between biased surfaces such as found at the ends of an electrodynamic tether and the space environment. A plasma contactor is a plasma source which emits a plasma cloud which facilitates the electrical connection. The physics of this plasma cloud is investigated for contactors used as electron collectors and it is shown that contactor clouds in space will consist of a spherical core possibly containing a shock wave. Outside of the core the cloud will expand anisotropically across the magnetic field leading to a turbulent cigar shape structure along the field. This outer region is itself divided into two regions by the ion response to the electric field. A two-dimensional theory of the motion of the cloud across the magnetic field is developed. The current voltage characteristic of an Argon plasma contactor cloud is estimated for several ion currents in the range of 1-100 Amperes. It is shown that small ion current contactors are more efficient than large ion current contactors. This suggests that if a plasma contactor is used on an electrodynamic tether then a miltiple tether array will be more efficient than a single tether.

  9. Tether Elevator Crawler Systems (TECS)

    NASA Technical Reports Server (NTRS)

    Swenson, Frank R.

    1987-01-01

    One of the needs of the experimenters on the space station is access to steady and controlled-variation microgravity environments. A method of providing these environments is to place the experiment on a tether attached to the space station. This provides a high degree of isolation from structural oscillations and vibrations. Crawlers can move these experiments along the tethers to preferred locations, much like an elevator. This report describes the motion control laws developed for these crawlers and the testing of laboratory models of these tether elevator crawlers.

  10. The investigation of tethered satellite system dynamics

    NASA Technical Reports Server (NTRS)

    Lorenzini, E.

    1985-01-01

    A progress report is presented that deals with three major topics related to Tethered Satellite System Dynamics. The SAO rotational dynamics computer code was updated. The program is now suitable to deal with inclined orbits. The output has been also modified in order to show the satellite Euler angles referred to the rotating orbital frame. The three-dimensional high resolution computer program SLACK3 was developed. The code simulates the three-dimensional dynamics of a tether going slack taking into account the effect produced by boom rotations. Preliminary simulations on the three-dimensional dynamics of a recoiling slack tether are shown in this report. A program to evaluate the electric potential around a severed tether is immersed in a plasma. The potential is computed on a three-dimensional grid axially symmetric with respect to the tether longitudinal axis. The electric potential variations due to the plasma are presently under investigation.

  11. Orbital transfer and release of tethered payloads. Continuation of investigation of electrodynamic stabilization and control of long orbiting tethers Martinez-Sanchez, Manuel

    NASA Technical Reports Server (NTRS)

    Colombo, G.; Grossi, M. D.; Arnold, D.

    1983-01-01

    The effect of reeling operations on the orbital altitude of the tether system and the development of control laws to minimize tether rebound upon payload release were studied. The use of the tether for LEO/GEO payload orbital transfer was also investigated. It was concluded that (1) reeling operations can contribute a significant amount of energy to the orbit of the system and should be considered in orbit calculations and predictions, (2) deployment of payloads, even very large payloads, using tethers is a practical and fully stable operation, (3) tether augmented LEO/GEO transfer operations yield useful payload gains under the practical constraint of fixed size OTV's, and (4) orbit to orbit satellite retrieval is limited by useful revisit times to orbital inclinations of less than forty-five degrees.

  12. MSFC MXER Tether Study

    NASA Technical Reports Server (NTRS)

    Polsgrove, Tara; Alexander, Reginald; Bonometti, Joseph; Chapman, Jack; Garza, Lucas; Glaese, John; Glasgow, Shaun; Guendel, Herb; Houston, Vance; Johnson, Paul

    2003-01-01

    This viewgraph presentation provides an overview of the proposed Momentum-eXchange/Electrodynamic Reboost (MXER) space hardware system. The tether system would be position cart-wheeling cables above the Earth and then, rotating like a giant sling, would capture spacecraft or payloads from space shuttles in low Earth orbits and launch them into higher orbits. This study focuses on system validation and structural design issues for MXER. Topics examined include: tether facility design, ED tether system, payload capture/catch mechanism, payload accomodations assembly (PAA), PAA rendezvous capability, and PAA capability to correct tether misthrows.

  13. Tethered satellite system dynamics and control

    NASA Technical Reports Server (NTRS)

    Musetti, B.; Cibrario, B.; Bussolino, L.; Bodley, C. S.; Flanders, H. A.; Mowery, D. K.; Tomlin, D. D.

    1990-01-01

    The first tethered satellite system, scheduled for launch in May 1991, is reviewed. The system dynamics, dynamics control, and dynamics simulations are discussed. Particular attention is given to in-plane and out-of-plane librations; tether oscillation modes; orbiter and sub-satellite dynamics; deployer control system; the sub-satellite attitude measurement and control system; the Aeritalia Dynamics Model; the Martin-Marietta and NASA-MSFC Dynamics Model; and simulation results.

  14. The space station tethered elevator system

    NASA Technical Reports Server (NTRS)

    Anderson, Loren A.

    1989-01-01

    The optimized conceptual engineering design of a space station tethered elevator is presented. The elevator is an unmanned mobile structure which operates on a ten kilometer tether spanning the distance between the Space Station and a tethered platform. Elevator capabilities include providing access to residual gravity levels, remote servicing, and transportation to any point along a tether. The potential uses, parameters, and evolution of the spacecraft design are discussed. Engineering development of the tethered elevator is the result of work conducted in the following areas: structural configurations; robotics, drive mechanisms; and power generation and transmission systems. The structural configuration of the elevator is presented. The structure supports, houses, and protects all systems on board the elevator. The implementation of robotics on board the elevator is discussed. Elevator robotics allow for the deployment, retrieval, and manipulation of tethered objects. Robotic manipulators also aid in hooking the elevator on a tether. Critical to the operation of the tethered elevator is the design of its drive mechanisms, which are discussed. Two drivers, located internal to the elevator, propel the vehicle along a tether. These modular components consist of endless toothed belts, shunt-wound motors, regenerative power braking, and computer controlled linear actuators. The designs of self-sufficient power generation and transmission systems are reviewed. Thorough research indicates all components of the elevator will operate under power provided by fuel cells. The fuel cell systems will power the vehicle at seven kilowatts continuously and twelve kilowatts maximally. A set of secondary fuel cells provides redundancy in the unlikely event of a primary system failure. Power storage exists in the form of Nickel-Hydrogen batteries capable of powering the elevator under maximum loads.

  15. Applications of Tethers in Space, Volume 1

    NASA Technical Reports Server (NTRS)

    Cron, A. C. (Compiler)

    1985-01-01

    The tethered satellite system is described including tether fundamentals. Applications of very long tethers in space to a broad spectrum of future space missions are explored. Topics covered include: science, transportation, constellations, artificial gravity, technology and test, and electrodynamic interactions. Recommendations to NASA are included.

  16. Membrane Tethering Complexes in the Endosomal System

    PubMed Central

    Spang, Anne

    2016-01-01

    Vesicles that are generated by endocytic events at the plasma membrane are destined to early endosomes. A prerequisite for proper fusion is the tethering of two membrane entities. Tethering of vesicles to early endosomes is mediated by the class C core vacuole/endosome tethering (CORVET) complex, while fusion of late endosomes with lysosomes depends on the homotypic fusion and vacuole protein sorting (HOPS) complex. Recycling through the trans-Golgi network (TGN) and to the plasma membrane is facilitated by the Golgi associated retrograde protein (GARP) and endosome-associated recycling protein (EARP) complexes, respectively. However, there are other tethering functions in the endosomal system as there are multiple pathways through which proteins can be delivered from endosomes to either the TGN or the plasma membrane. Furthermore, proteins that may be part of novel tethering complexes have been recently identified. Thus, it is likely that more tethering factors exist. In this review, I will provide an overview of different tethering complexes of the endosomal system and discuss how they may provide specificity in membrane traffic. PMID:27243003

  17. Tether deployment monitoring system, phase 2

    NASA Technical Reports Server (NTRS)

    1989-01-01

    An operational Tether Deployment Monitoring System (TEDEMS) was constructed that would show system functionality in a terrestrial environment. The principle function of the TEDEMS system is the launching and attachment of reflective targets onto the tether during its deployment. These targets would be tracked with a radar antenna that was pointed towards the targets by a positioning system. A spring powered launcher for the targets was designed and fabricated. An instrumentation platform and launcher were also developed. These modules are relatively heavy and will influence tether deployment scenarios, unless they are released with a velocity and trajectory closely matching that of the tether. Owing to the tracking range limitations encountered during field trails of the Radar system, final TEDEMS system integration was not completed. The major module not finished was the system control computer. The lack of this device prevented any subsystem testing or field trials to be conducted. Other items only partially complete were the instrumentation platform launcher and modules and the radar target launcher. The work completed and the tests performed suggest that the proposed system continues to be a feasible approach to tether monitoring, although additional effort is still necessary to increase the range at which modules can be detected. The equipment completed and tested, to the extent stated, is available to NASA for use on any future program that requires tether tracking capability.

  18. Tether dynamics and control results for tethered satellite system's initial flight

    NASA Technical Reports Server (NTRS)

    Chapel, Jim D.; Flanders, Howard

    1993-01-01

    The recent Tethered Satellite System-1 (TSS-1) mission has provided a wealth of data concerning the dynamics of tethered systems in space and has demonstrated the effectiveness of operational techniques designed to control these dynamics. In this paper, we review control techniques developed for managing tether dynamics, and discuss the results of using these techniques for the Tethered Satellite System's maiden flight on STS-46. In particular, the flight results of controlling libration dynamics, string dynamics, and slack tether are presented. These results show that tether dynamics can be safely managed. The overall stability of the system was found to be surprisingly good even at relatively short tether lengths. In fact, the system operated in passive mode at a tether length of 256 meters for over 9 hours. Only monitoring of the system was required during this time. Although flight anomalies prevented the planned deployment to 20 km, the extended operations at shorter tether lengths have proven the viability of using tethers in space. These results should prove invaluable in preparing for future missions with tethered objects in space.

  19. Overview of the National Aeronautics and Space Administration tether activities

    NASA Technical Reports Server (NTRS)

    Penzo, Paul A.

    1989-01-01

    NASA research concerning the use of tethers in space is reviewed, including joint research with the Italian Space Agency. Tether applications under consideration are described, such as a tethered fuel depot and a tethered gravity laboratory platform for the Space Station, providing artificial gravity to and from Mars, payload recovery and waste management, aerothermodynamic magnetospheric physics, and electrodynamic propulsion, braking, and power generation for the Space Shuttle. Also, tether flight demonstrations are examined, including the Small Expendable Deployer System, the Get-Away Tether Experiment, the Tether Elevator Crawler System, and the Kinetic Isolation Tether Experiment.

  20. UAH/NASA Workshop on The Uses of a Tethered Satellite System

    NASA Technical Reports Server (NTRS)

    Wu, S. T. (Editor)

    1978-01-01

    Potential applications of the system are categorized into four areas: geological applications, atmospheric applications, electrodynamics and plasma studies, and technology applications. The multiple-use tethered system with feedback control, will be capable of supporting a payload or satellite suspended from the Shuttle cargo bay, at distances up to 100 kilometers from the Shuttle. Experiments proposed include: geomagnetic mapping, lower atmospheric measurements, ionospheric interactions with large space structures, solar wind transport, and magnetohydrodynamic measurements.

  1. Tethered Lubricants for Small Systems

    SciTech Connect

    Lynden A. Archer

    2006-01-09

    The objective of this research project is two-fold. First, to fundamentally understand friction and relaxation dynamics of polymer chains near surfaces; and second, to develop novel self-lubricated substrates suitable for MEMS devices. During the three-year performance period of this study the PI and his students have shown using theory and experiments that systematic introduction of disorder into tethered lubricant coatings (e.g. by using self-assembled monolayer (SAM) mixtures or SAMs with nonlinear, branched architectures) can be used to significantly reduce the friction coefficient of a surface. They have also developed a simple procedure based on dielectric spectroscopy for quantifying the effect of surface disorder on molecular relaxation in lubricant coatings. Details of research accomplishments in each area of the project are described in the body of the report.

  2. The first mission of the Tethered Satellite System

    NASA Technical Reports Server (NTRS)

    Powers, C. Blake (Editor); Shea, Charlotte; Mcmahan, Tracy

    1992-01-01

    The era of space-age tethered operations moves toward reality with the launch of Tethered Satellite System-1 (TSS-1). The primary objective of this mission is to demonstrate the technology of long tethered systems in space and to demonstrate, through scientific investigations, that such systems are useful for research.

  3. Modeling tether-ballast asteroid diversion systems, including tether mass and elasticity

    NASA Astrophysics Data System (ADS)

    French, David B.; Mazzoleni, Andre P.

    2014-10-01

    The risk of an impact between a large asteroid and the Earth has been significant enough to attract the attention of many researchers. This paper focuses on a mitigation technique that involves the use of a long tether and ballast mass to divert an asteroid. When such a tether is modeled as massless and inelastic, results show that the method may be viable for diverting asteroids away from a collision with the Earth; the next step towards demonstrating the viability of the approach is to conduct a study which uses a more realistic tether model. This paper presents such a study, in which the tether models include tether mass and elasticity. These models verify that a tether-ballast system is capable of diverting Earth-threatening asteroids. Detailed parametric studies are presented which illustrate how system performance depends on tether mass and elasticity. Also, case studies are presented which show how more realistic models can aid in the design of tether-ballast asteroid mitigation systems. Key findings include the dangers imposed by periods during which the tether goes slack and ways to preclude this.

  4. Investigation of electrodynamic stabilization and control of long orbiting tethers. [space shuttle payloads

    NASA Technical Reports Server (NTRS)

    Arnold, D. A.; Dobrowolny, M.

    1981-01-01

    An algorithm for using electric currents to control pendular oscillations induced by various perturbing forces on the Skyhook wire is considered. Transverse and vertical forces on the tether; tether instability modes and causes during retrieval by space shuttle; simple and spherical pendulum motion and vector damping; and current generation and control are discussed. A computer program for numerical integration of the in-plane and out-of-plane displacements of the tether vs time was developed for heuristic study. Some techniques for controlling instabilities during payload retrieval and methods for employing the tether for launching satellites from the space shuttle are considered. Derivations and analyses of a general nature used in all of the areas studied are included.

  5. Overview of Future NASA Tether Applications

    NASA Technical Reports Server (NTRS)

    Johnson, Les; Gilchrist, Brian; Estes, Robert D.; Lorenzini, Enrico

    1998-01-01

    The groundwork has been laid for tether applications in space. NASA has developed tether technology for space applications since the 1960's. Important recent milestones include retrieval of a tether in space (TSS-1, 1992), successful deployment of a 20-km-long tether in space (SEDS-1, 1993), and operation of an electrodynamic tether with tether current driven in both directions-power and thrust modes (PMG, 1993). Various types of tethers and systems can be used for space transportation. Short electrodynamic tethers can use solar power to 'push' against a planetary magnetic field to achieve propulsion without the expenditure of propellant. The planned Propulsive Small Expendable Deployer System (ProSEDS) experiment will demonstrate electrodynamic tether thrust during its flight in early 2000. Utilizing completely different physical principles, long non-conducting tethers can exchange momentum between two masses in orbit to place one body into a higher orbit or a transfer orbit for lunar and planetary missions. Recently completed system studies of this concept indicate that it would be a relatively low-cost in-space asset with long-term multi-mission capability. Tethers can also be used to support space science by providing a mechanism for precision formation flying and for reaching regions of the upper atmosphere that were previously inaccessible.

  6. Report of the Electrodynamic Interactions Panel

    NASA Technical Reports Server (NTRS)

    Stone, N. H.; Taylor, R. S.; Benford, S.; Binsack, J. H.; Dobrowolny, M.; Finnegan, P.; Grossi, M. D.; Hudson, M.; Intriligator, D.; Kaminskas, R.

    1985-01-01

    A wide range of opportunities is provided by the electrodynamic tether to more fully understand the generation of waves in plasmas, the behavior of field aligned currents, the behavior of large body-space plasma interactions, and for process simulation, using the electrodynamic tether to study processes and phenomena relevant to solar system and astrophysics plasma physics. The electrodynamic tether offers a means of study and experimentation in space which will provide a rich yield in new scientific results and will enhance the understanding of space plasma physics. It also has promising technological applications (e.g., the generation of electrical power and thrust) which may be highly significant to future space operations.

  7. Tethered Forth system for FPGA applications

    NASA Astrophysics Data System (ADS)

    Goździkowski, Paweł; Zabołotny, Wojciech M.

    2013-10-01

    This paper presents the tethered Forth system dedicated for testing and debugging of FPGA based electronic systems. Use of the Forth language allows to interactively develop and run complex testing or debugging routines. The solution is based on a small, 16-bit soft core CPU, used to implement the Forth Virtual Machine. Thanks to the use of the tethered Forth model it is possible to minimize usage of the internal RAM memory in the FPGA. The function of the intelligent terminal, which is an essential part of the tethered Forth system, may be fulfilled by the standard PC computer or by the smartphone. System is implemented in Python (the software for intelligent terminal), and in VHDL (the IP core for FPGA), so it can be easily ported to different hardware platforms. The connection between the terminal and FPGA may be established and disconnected many times without disturbing the state of the FPGA based system. The presented system has been verified in the hardware, and may be used as a tool for debugging, testing and even implementing of control algorithms for FPGA based systems.

  8. Tether Technologies for Future Space Applications

    NASA Technical Reports Server (NTRS)

    Frame, Kyle L.; Dankanich, John W.; Bonometti, Joseph A.

    2005-01-01

    This viewgraph presentation provides information on several types of spacecraft tethers, and possible applications for them. The tethers profiled include: 1) Mechanical tethers; 2) Electrodynamic (ED) tethers; 3) Momentum eXchange Electrodynamic Reboost (MXER) tethers; 4) Synergistic technologies. Tethers can have low Earth orbit (LEO), lunar, and interplanetary applications.

  9. Shuttle/tethered satellite system conceptual design study

    NASA Technical Reports Server (NTRS)

    1976-01-01

    A closed-loop control system was added to the tether reel which improves control over the tethered satellite. In addition to increasing the stability of the tethered satellite along local vertical, this control system is used for deployment and retrieval of tethered satellites. This conceptual design study describes a tether system for suspending a science payload at an altitude of 120 km from space shuttle orbiter flying at an altitude of 200 km. In addition to the hardware conceptual designs, various aspects concerning Orbiter accommodations are discussed.

  10. On vibration control of tethered satellite systems

    NASA Technical Reports Server (NTRS)

    Xu, D. M.; Misra, A. K.; Modi, V. J.

    1983-01-01

    The general dynamics of a shuttle supported tethered subsatellite system taking into account the longitudinal and three dimensional transverse vibrations is considered. It is noted that control of inherently unstable dynamics during retrieval of the subsatellite can be carried out by letting the rate of change length depend on the state variables in an appropriate manner. Control laws using linear feedback of inplane state variables and nonlinear feedback of out-of-plane state variables are proposed.

  11. Summary Presentation of the Electrodynamics Interactions Panel

    NASA Technical Reports Server (NTRS)

    Stone, N. H.

    1985-01-01

    Technological and scientific uses of electrodynamic tethers in space are considered. Areas of concern for such applications of electrodynamic tethers are enumerated. Thrust and power generation using tethers are discussed.

  12. GTOSS: Generalized Tethered Object Simulation System

    NASA Technical Reports Server (NTRS)

    Lang, David D.

    1987-01-01

    GTOSS represents a tether analysis complex which is described by addressing its family of modules. TOSS is a portable software subsystem specifically designed to be introduced into the environment of any existing vehicle dynamics simulation to add the capability of simulating multiple interacting objects (via multiple tethers). These objects may interact with each other as well as with the vehicle into whose environment TOSS is introduced. GTOSS is a stand alone tethered system analysis program, representing an example of TOSS having been married to a host simulation. RTOSS is the Results Data Base (RDB) subsystem designed to archive TOSS simulation results for future display processing. DTOSS is a display post processors designed to utilize the RDB. DTOSS extracts data from the RDB for multi-page printed time history displays. CTOSS is similar to DTOSS, but is designed to create ASCII plot files. The same time history data formats provided for DTOSS (for printing) are available via CTOSS for plotting. How these and other modules interact with each other is discussed.

  13. The use of tethers for payload orbital transfer. Continuation of investigation of electrodynamic stabilization and control of long orbiting tethers, volume 2

    NASA Technical Reports Server (NTRS)

    Colombo, G.; Martinez-Sanchez, M.; Arnold, D.

    1982-01-01

    The SKYHOOK program was used to do simulations of two cases of the use of the tether for payload orbital transfer. The transport of a payload along the tether from a heavy lower platform to an upper launching platform is considered. A numerical example of the Shuttle launching a payload using an orbital tether facility is described.

  14. Electrodynamics of long conducting tethers in the near-earth environment. [in the ionosphere

    NASA Technical Reports Server (NTRS)

    Dobrowolny, M.; Colombo, G.; Grossi, M. D.

    1976-01-01

    An analytical approach was developed to evaluate the electrodynamic interactions affecting a thin, bare metallic wire moving in the ionosphere. The wire's diameter was smaller than the Debye length; therefore, the plasma sheath around the wire was taken into account in computing inducing drag force and torque. Computer programs were prepared for the numerical evaluation of mathematical functions that were required to compute the distribution of the potential along the wire and of the current in the wire. Numerical calculations based on this software are shown.

  15. TESSX: A Mission for Space Exploration with Tethers

    NASA Technical Reports Server (NTRS)

    Cosmo, Mario L.; Lorenzini, Enrico C.; Gramer, Daniel J.; Hoffman, John H.; Mazzoleni, Andre P.

    2005-01-01

    Tethers offer significant potential for substantially increasing payload mass fraction, increasing spacecraft lifetime, enhancing long-term space travel, and enabling the understanding and development of gravity-dependent technologies required for Moon and Mars exploration. The development of the Tether Electrodynamic Spin-up and Survivability Experiment (TESSX) will support applications relevant to NASA's new exploration initiative, including: artificial gravity generation, formation flying, electrodynamic propulsion, momentum exchange, and multi-amp current collection and emission. Under the broad term TESSX, we are currently evaluating several different tether system configurations and operational modes. The initial results of this work are presented, including hardware development, orbital dynamics simulations, and electrodynamics design and analysis.

  16. Development testing of TSS-1 Deployer tether control system mechanisms

    NASA Technical Reports Server (NTRS)

    Bentley, D. P.; Tisdale, D.

    1989-01-01

    Successful tether deployment and retrieval, consistent with established control laws, is predicated upon statusing real time tether dynamic conditions. This paper reports on the initial phase of engineering tests performed on various components and subassemblies integral to the TSS-1 tether control system as part of the TSS Deployer. The tests were conducted as part of the tether control system development and verification plan to confirm the functionality and map the performance of the hardware in both ambient and environmental test conditions. The result of this development effort is a lessons-learned list and design upgrades to both the flight and test hardware and to the test methods and procedures.

  17. Guidebook for analysis of tether applications

    NASA Technical Reports Server (NTRS)

    Carroll, J. A.

    1985-01-01

    This guidebook is intended as a tool to facilitate initial analyses of proposed tether applications in space. Topics disscussed include: orbit and orbit transfer equations; orbital perturbations; aerodynamic drag; thermal balance; micrometeoroids; gravity gradient effects; tether control strategies; momentum transfer; orbit transfer by tethered release/rendezvous; impact hazards for tethers; electrodynamic tether principles; and electrodynamic libration control issues.

  18. Mission-function control of tethered satellite/climber system

    NASA Astrophysics Data System (ADS)

    Kojima, Hirohisa; Fukatsu, Kosei; Trivailo, Pavel M.

    2015-01-01

    Because the tether of a tethered satellite system (TSS) can be extremely long, it would be difficult to inspect the damage to the tether. The ultimate configuration of a TSS could be a space elevator (SE). The tether needs to carry a crawler or climber to inspect damage to the tether or transport travelers on the SE. Coriolis force due to the climber motion causes librational motion of the tether. The numerical simulations have shown that the original mission-function (MF) control is not applicable to a TSS with a climber because it was intended for subsatellite deployment and retrieval control using a tether, not for a climber on the tether. This paper proposes a new MF control to suppress the librational motion of a tether with a climber. The proposed MF control is a modified version of the original MF control. The active force to drive the climber is determined from the MF. A simplified dynamic model of a TSS with a single climber is used to evaluate the derived controller. The effectiveness of the proposed method is verified through numerical simulations.

  19. Project 'VOLCANO': Electronics of tethered satellite system

    NASA Astrophysics Data System (ADS)

    Savich, N. A.

    The main goal of the 'VOLCANO' project developed jointly by the Institute of Radio Engineering and Electronics and space concern 'ENERGIA' is experimental investigation of the current-voltage characteristics of the 'Collector-Boom-Emitter' system simulating the long Tethered Satellite System (TSS) in the real space flight conditions on the transport ship 'PROGRESS'. These measurements will allow scientists to determine the attainable current values for different combinations of collectors and emitters (passive metallic sphere, thermocathode, hollow cathodes and show up some prospects of active TSS. The report is concerned with the concept, purpose and tasks of the project, the planned set up of the measurement equipment on the 'PROGRESS' ship and in the container extended on the deployable 100 m long boom end.

  20. TETHERED BALLOON SAMPLING SYSTEMS FOR MONITORING AIR POLLUTION

    EPA Science Inventory

    The paper is an overview of recent studies in which balloons, usually tethered, have been used to investigate the structure and air quality of the planetary boundary layer. It also describes a number of lightweight tethered balloon sampling systems, developed to investigate parti...

  1. Multi-Tethered Space-Based Interferometers: Particle System Model

    NASA Technical Reports Server (NTRS)

    Gates, Stephen S.

    2001-01-01

    Dynamics models are presented for a class of space-based interferometers comprised of multiple component bodies, interconnected in various arrangements, by low-mass flexible tethers of variable length. The tethered constellations are to perform coordinated rotational scanning accompanied by baseline dimensional changes, as well as spin axis realignments and spin-up/spin-down maneuvers. The mechanical idealization is a system of N point masses interconnected by massless tethers of variable length. Both extensible and inextensible tethers are considered. Expressions for system angular and linear momenta are developed. The unrestricted nonlinear motion equations are derived via Lagranges equations. Rheonomic constraints are introduced to allow prescribed motion of any degrees of freedom, and the associated physical forces are determined. The linearized equations of motion are obtained for the steady rotation of a system with extensible tethers of constant unstrained length.

  2. Why Not Space Tethers?

    NASA Technical Reports Server (NTRS)

    Stone, Noble H.

    2007-01-01

    The Tethered Satellite System Space Shuttle missions, TSS-1 in 1993 and TSS-1R in 1996, were the height of space tether technology development. Since NASA's investment of some $200M and two Shuttle missions in those two pioneering missions, there have been several smaller tether flight experiments, but interest in this promising technology has waned within NASA as well as the DOD agencies. This is curious in view of the unique capabilities of space tether systems and the fact that they have been flight validated and shown to perform as, or better than, expected in earth orbit. While it is true that the TSS-1, TSS-1R and SEDS-2 missions experienced technical difficulties, the causes of these early developmental problems are now known to be design or materials flaws that are (1) unrelated to the basic viability of space tether technology, and (2) they are readily corrected. The purpose of this paper is to review the dynamic and electrodynamic fundamentals of space tethers and the unique capabilities they afford (that are enabling to certain types of space missions); to elucidate the nature, cause, and solution of the early developmental problems; and to provide an update on progress made in development of the technology. Finally, it is shown that (1) all problems experienced during early development of the technology now have solutions; and (2) the technology has been matured by advances made in strength and robustness of tether materials, high voltage engineering in the space environment, tether health and status monitoring, and the elimination of the broken tether hazard. In view of this, it is inexplicable why this flight-validated technology has not been utilized in the past decade, considering the powerful and unique capabilities that space tethers can afford that are, not only required to carryout, otherwise, unobtainable missions, but can also greatly reduce the cost of certain on-going space operations.

  3. Study of tethered satellite active attitude control

    NASA Technical Reports Server (NTRS)

    Colombo, G.

    1982-01-01

    Existing software was adapted for the study of tethered subsatellite rotational dynamics, an analytic solution for a stable configuration of a tethered subsatellite was developed, the analytic and numerical integrator (computer) solutions for this "test case' was compared in a two mass tether model program (DUMBEL), the existing multiple mass tether model (SKYHOOK) was modified to include subsatellite rotational dynamics, the analytic "test case,' was verified, and the use of the SKYHOOK rotational dynamics capability with a computer run showing the effect of a single off axis thruster on the behavior of the subsatellite was demonstrated. Subroutines for specific attitude control systems are developed and applied to the study of the behavior of the tethered subsatellite under realistic on orbit conditions. The effect of all tether "inputs,' including pendular oscillations, air drag, and electrodynamic interactions, on the dynamic behavior of the tether are included.

  4. Tether Technology Interchange Meeting

    NASA Technical Reports Server (NTRS)

    Harrison, James K. (Compiler)

    1998-01-01

    This is a compilation of 25 papers presented at a tether technical interchange meeting in Huntsville, AL, on September 9-10, 1997. After each presentation, a technical discussion was held to clarify and expand the salient points. A wide range of subjects was covered including tether dynamics, electrodynamics, space power generation, plasma physics, ionospheric physics, towing tethers, tethered reentry schemes, and future tether missions.

  5. Tethered airfoil wind energy conversion system

    SciTech Connect

    Biscomb, L.I.

    1982-01-05

    A generally toric lighter-than-air gas bag-type airfoil is tethered to the ground at a plurality of angularly widely distributed points about the periphery of the gas bag. A wind turbine is mounted at the entrance to the axially central vent. The tether lines are entrained about individually operable power winches, preferably controlled by a microprocessor which takes in wind direction and tether line tension data and operates the winches and inflation gas inlet and outlet valves to orient the wind turbine into the wind for maximum power output.

  6. The Italian participation to the Tethered Satellite System

    NASA Astrophysics Data System (ADS)

    Colombo, G.; Bergamaschi, S.; Bevilacqua, F.

    1981-09-01

    The Tethered Satellite System (TSS), a device whereby measurement platforms and other objects can be deployed by means of a connecting tether to station points as far as 100 km from the Space Shuttle, is discussed. In connection with the agreement between the U.S. and Italy, it is noted that NASA will be responsible for the design and development of the deployer and CNR will be responsible for the design and development of the subsatellite. Scientific applications of the TSS include those which use the tether as a means of carrying instrumentation to a suitable distance from the Shuttle and those which use the tether as a part of the instrumentation. Among the low-altitude scientific applications are studies of the earth's magnetic and gravitational fields, aeronomy, research on the problem of re-entry, earth observations, and plasma physics. The technological applications of the TSS are those in which the tether is used as a structure or a crane

  7. Get-Away tether experiment - Experimental plans

    NASA Technical Reports Server (NTRS)

    Greene, Michael; Walls, Justin; Carter, J. Theron; Rupp, Charles C.

    1988-01-01

    The experimental capabilities of the Get-Away Tether Experiment (GATE) are presented and a series of demonstration mission are proposed. The GATE is a free-flying tether system that will develop or demonstrate technology in the areas of tether dynamics (deployment and stabilization, retrieval, stationkeeping, and severance), tether electrodynamics, micrometeor hazards to tethers, and disturbance rejection. The system consists of two subsatellites connected by 1 km of tether. The free-flying system is ejected from the Orbiter via a Getaway Special (GAS) canister. Two dynamics missions are profiled along with a description of electrodynamic mission capabilities. The dynamic interactions of the end body and tether may be observed from the Orbiter or from an on-board video tracking system. Hence, GATE provides a unique, low cost capability to demonstrate various tether technologies, and address critical design and safety issues associated with future tether applications. An assessment of the significant measurable parameters and associated instrumentation is given. Future work and system development projection schedules are also outlined.

  8. Artificial or variable gravity attained by tether systems

    NASA Technical Reports Server (NTRS)

    Lundquist, C. A.

    1986-01-01

    The simplest orbiting tethered system demands for stability that the mass centers of two end bodies be displaced above and below the position of zero acceleration. Therefore, the contents of the end bodies are subjected necessarily to acceleration fields or artificial gravity whose magnitudes depend on the dimensions and masses of the system. If the length of the tether changes, so do the fields. Even for a fixed tether length, the acceleration field at a location in the system may be somewhat variable unless special means are employed to maintain a constant value. These fundamental properties of a tethered system can be used to advantage if small or variable acceleration fields are desired for experimental or operational reasons. This potential use involves a few expressions from a formulation of tether system dynamics. Some of these formulae were collected for convenient use. Two and three body tethered equilibrium equations are explained. A special application of acceleration field control using a tether system is attainment of near-zero gravity. In this applicaition, even small variations about zero become a critical matter.

  9. Theory of plasma contactors for electrodynamic tethered satellite systems

    NASA Technical Reports Server (NTRS)

    Parks, D. E.; Katz, I.

    1987-01-01

    Recent data from ground and space experiments indicate that plasma releases from an object dramatically reduce the sheath impedance between the object and the ambient plasma surrounding it. Available data is in qualitative accord with the theory developed to quantify the flow of current in the sheath. Electron transport in the theory is based on a fluid model of a collisionless plasma with an effective collision frequency comparable to frequencies of plasma oscillations. The theory leads to low effective impedances varying inversely with the square root of the injected plasma density. To support such a low impedance mode of operation using an argon plasma source, for example, requires that only one argon ion be injected for each thirty electrons extracted from the ambient plasma. The required plasma flow rates are quite low; to extract one ampere of electron current requires a mass flow rate of about one gram of argon per day.

  10. Enhanced current flow through a plasma cloud by induction of plasma turbulence. [electrodynamic tethers for generating power for spacecraft in low earth orbit

    NASA Technical Reports Server (NTRS)

    Hastings, D. E.; Gioulekas, A.

    1987-01-01

    Electrodynamic tethers have been proposed as a means of generating power in low earth orbit. One of the limitations on the power generated is the relatively low electron current that can be collected. It is proposed that the electron current can be significantly enhanced by means of current induced plasma turbulence in a plasma cloud around the collecting anode. This is examined for the specific case of lower hybrid turbulence. An important conclusion is that the use of plasma clouds in the ionosphere will entail a high impedance (no instability) and a low impedance (lower hybrid instability) mode of operation depending on the current density.

  11. STEP Tether Dynamics Preliminary Analysis

    NASA Technical Reports Server (NTRS)

    Glaese, John R.

    2000-01-01

    The General Tethered Object Simulation System (GTOSS) has been successfully converted to the PC environment. GTOSS has been run under Microsoft Windows 95, 98 and NT4.0 with no problems noted. Adaptation to the PC environment and definition of the 3 three body configuration required resizing some of the GTOSS internal data arrays. To allow studies of the tether dynamics accompanying electrodynamic thrust, a tether current flow model has also been developed for GTOSS. This model includes effects due to the earth's magnetic field and ionosphere, tether conductivity, temperature, motion, shape and available power. Sample cases have been defined for a proposed STEP-AIRSEDS (Space Transfer using Electrodynamic Propulsion-The Michigan Technic Corporation proposed tether missions for commercial applications) three body configuration. This required definition of a 6th power scenario for GTOSS. This power scenario allows a user to specify whether orbit raising or orbit lowering is to be performed by selecting the number of the tether. Orbit raising and orbit lowering sample cases have been run successfully. Results from these runs have been included in this report. Results have only been generated so far for a three body configuration. Only point end masses have been represented. No attitude dynamics have been included. Initial results suggest that tether current can have significant and detrimental effects on tether dynamics and provisions will have to be made for control of it. This control will have to be considered in connection with desired target orbits for electrodynamic thrusting, as well as end body attitude control, momentum management of proposed control moment gyros, solar array pointing. All of these items will interact and thus, any system simulation will have to have each of these effects modeled in sufficient detail to display these interactions.

  12. Analysis of an electrodynamic maglev system

    SciTech Connect

    Davey, K.

    1999-09-01

    Electrodynamic systems (EDS's) for maglev have an advantage over electromagnetic systems (EMS's) in that the stability is built into the system. EDS's induce the currents used for levitation and guidance, while EMS's impose those currents with controlled feedback. The movement of a magnet over properly designed EDS coils results in forces to keep the system fixed in the lowest energy or null flux spot. In the past such systems have been examined through two-dimensional boundary element techniques. An approximation to the full three-dimensional time harmonic problem is obtained through LaPlace transform theory after using boundary element methods to predict the mutual coupling of the magnets with the track coils. The analytic solution offers helpful design and operation guidelines.

  13. Dual-keel electrodynamic Maglev system

    SciTech Connect

    He, Jianliang; Rote, D.M.; Wang, Zian; Coffey, H.T.

    1995-12-31

    This paper introduces a new concept for an electrodynamic-suspension maglev system that has a dual-keel arrangement. Each keel consists of a row of superconducting magnets aboard the vehicle. The keels move in troughs in the guideway that are each lined with pairs of figure-eight-shaped null-flux coils. Each pair of null-flux coils is cross-connected to produce null-flux suspension and guidance force. The cross-connected figure-eight null-flux coils in each trough are also energized by a three-phase power supply to produce propulsive force. Preliminary analysis shows that the new system has many advantages over other EDS systems in terms of system performance and dynamic stability.

  14. Tethered lifting systems for measurements in the lower atmosphere

    NASA Astrophysics Data System (ADS)

    Jensen, Michael Lamar

    2000-10-01

    This work defines a Tethered Lifting System for measurements in the lower atmosphere, its design and development, and applications for its use. Using historical kite research and the unique capabilities of tethered lifting platforms as motivation, a complete system has been created offering the complementary benefits of parafoil kites and tethered balloons as lifting platforms. Support systems including tethers, winching systems and payload data collection and telemetry systems round out the Tethered Lifting System to provide a complete atmospheric measurement system. The kite platforms have been enhanced by the invention and development of a wind-powered Tether Rover for Atmospheric Research (WindTRAM), providing rapid profiling and precise positioning capabilities. Design of the WindTRAM and implementation of onboard feedback control are covered in detail, as they comprise the most novel contribution of this research. The breadth of possible applications for these technologies is touched upon by examination of some of the specific research applications undertaken by the researchers at the Cooperative Institute for Research in the Environmental Sciences during the last decade.

  15. On tethered sample and mooring systems near irregular asteroids

    NASA Astrophysics Data System (ADS)

    Ren, Yuan; Shan, Jinjun

    2014-10-01

    A tethered asteroid sample and mooring system is investigated in this paper. In this system the spacecraft is moored to the surface of an irregular asteroid such as 216 Kleopatra by using a rocket-propelled anchor with a cable. The rocket-propelled anchor is a kind of space penetrator, which can inject into asteroids at high speeds generated by its own rocket engine. It can be used to explore the interior structure of asteroids, and it can also be used as a sample collector. When the sampling mission is done, the sample can be pulled back to the spacecraft with the anchor. Using this method, the spacecraft can be kept in a safe region in which it cannot be trapped by the gravitational field of the asteroid. This work is concerned with the dynamics of the tethered system near irregular asteroids. First, a shape model and gravitational field model of irregular asteroids are built. Then, the configuration and the stability of the tethered system are investigated, and the quasi-periodic motion near the equilibrium point of the tethered system is analyzed. Finally, the non-uniform density distribution of the asteroids is considered. The deployment process and the oscillation of the tethered system in the uncertain asteroid gravity field are simulated using the Monte Carlo method. The feasibility of the tethered asteroid sample and mooring system is proved.

  16. Applications of Tethers in Space: Workshop Proceedings, Volume 2

    NASA Technical Reports Server (NTRS)

    Baracat, W. A. (Compiler)

    1986-01-01

    Topics addressed include: tethered orbital transfer vehicle operations, Centaur and Shuttle tether technology; tethered constellations, gravitational effects; Shuttle continuous open wind tunnel; optimal control laws, electrodynamic tether technology; and space station facilities.

  17. Applications of Tethers in Space: Workshop proceedings, volume 2

    SciTech Connect

    Baracat, W.A.

    1986-06-01

    Topics addressed include: tethered orbital transfer vehicle operations, Centaur and Shuttle tether technology; tethered constellations, gravitational effects; Shuttle continuous open wind tunnel; optimal control laws, electrodynamic tether technology; and space station facilities.

  18. The investigation of tethered satellite system dynamics

    NASA Technical Reports Server (NTRS)

    Lorenzini, E. C.

    1986-01-01

    The analysis of the rotational dynamics of the satellite was focused on the rotational amplitude increase of the satellite, with respect to the tether, during retrieval. The dependence of the rotational amplitude upon the tether tension variation to the power 1/4 was thoroughly investigated. The damping of rotational oscillations achievable by reel control was also quantified while an alternative solution that makes use of a lever arm attached with a universal joint to the satellite was proposed. Comparison simulations between the Smithsonian Astrophysical Observatory and the Martin Marietta (MMA) computer code of reteival maneuvers were also carried out. The agreement between the two, completely independent, codes was extremely close, demonstrating the reliability of the models. The slack tether dynamics during reel jams was analytically investigated in order to identify the limits of applicability of the SLACK3 computer code to this particular case. Test runs with SLACK3 were also carried out.

  19. Tethering Complexes in the Arabidopsis Endomembrane System.

    PubMed

    Vukašinović, Nemanja; Žárský, Viktor

    2016-01-01

    Targeting of endomembrane transport containers is of the utmost importance for proper land plant growth and development. Given the immobility of plant cells, localized membrane vesicle secretion and recycling are amongst the main processes guiding proper cell, tissue and whole plant morphogenesis. Cell wall biogenesis and modification are dependent on vectorial membrane traffic, not only during normal development, but also in stress responses and in plant defense against pathogens and/or symbiosis. It is surprising how little we know about these processes in plants, from small GTPase regulation to the tethering complexes that act as their effectors. Tethering factors are single proteins or protein complexes mediating first contact between the target membrane and arriving membrane vesicles. In this review we focus on the tethering complexes of the best-studied plant model-Arabidopsis thaliana. Genome-based predictions indicate the presence of all major tethering complexes in plants that are known from a hypothetical last eukaryotic common ancestor (LECA). The evolutionary multiplication of paralogs of plant tethering complex subunits has produced the massively expanded EXO70 family, indicating a subfunctionalization of the terminal exocytosis machinery in land plants. Interpretation of loss of function (LOF) mutant phenotypes has to consider that related, yet clearly functionally-specific complexes often share some common core subunits. It is therefore impossible to conclude with clarity which version of the complex is responsible for the phenotypic deviations observed. Experimental interest in the analysis of plant tethering complexes is growing and we hope to contribute with this review by attracting even more attention to this fascinating field of plant cell biology. PMID:27243010

  20. Tethering Complexes in the Arabidopsis Endomembrane System

    PubMed Central

    Vukašinović, Nemanja; Žárský, Viktor

    2016-01-01

    Targeting of endomembrane transport containers is of the utmost importance for proper land plant growth and development. Given the immobility of plant cells, localized membrane vesicle secretion and recycling are amongst the main processes guiding proper cell, tissue and whole plant morphogenesis. Cell wall biogenesis and modification are dependent on vectorial membrane traffic, not only during normal development, but also in stress responses and in plant defense against pathogens and/or symbiosis. It is surprising how little we know about these processes in plants, from small GTPase regulation to the tethering complexes that act as their effectors. Tethering factors are single proteins or protein complexes mediating first contact between the target membrane and arriving membrane vesicles. In this review we focus on the tethering complexes of the best-studied plant model—Arabidopsis thaliana. Genome-based predictions indicate the presence of all major tethering complexes in plants that are known from a hypothetical last eukaryotic common ancestor (LECA). The evolutionary multiplication of paralogs of plant tethering complex subunits has produced the massively expanded EXO70 family, indicating a subfunctionalization of the terminal exocytosis machinery in land plants. Interpretation of loss of function (LOF) mutant phenotypes has to consider that related, yet clearly functionally-specific complexes often share some common core subunits. It is therefore impossible to conclude with clarity which version of the complex is responsible for the phenotypic deviations observed. Experimental interest in the analysis of plant tethering complexes is growing and we hope to contribute with this review by attracting even more attention to this fascinating field of plant cell biology. PMID:27243010

  1. Selected tether applications in space: Phase 2. Executive summary

    NASA Technical Reports Server (NTRS)

    Thorson, M. H.; Lippy, L. J.

    1985-01-01

    The application of tether technology has the potential to increase the overall performance efficiency and capability of the integrated space operations and transportation systems through the decade of the 90s. The primary concepts for which significant economic benefits were identified are dependent on the space station as a storage device for angular momentum and as an operating base for the tether system. Concepts examined include: (1) tether deorbit of shuttle from space station; (2) tethered orbit insertion of a spacecraft from shuttle; (3) tethered platform deployed from space station; (4) tether-effected rendezvous of an OMV with a returning OTV; (5) electrodynamic tether as an auxiliary power source for space station; and (6) tether assisted launch of an OTV mission from space station.

  2. In-orbit experimentation with the Small Expendable-Tether Deployment System

    NASA Technical Reports Server (NTRS)

    Lorenzini, Enrico C.; Carroll, Joseph A.

    1990-01-01

    The Small Expendable-Tether Deployment System (SEDS) is a light-weight deployer capable of deploying instrumented packages and other tethered payloads up to a distance of 20 km. The system is simple and inexpensive because it does not retrieve the tethered payloads. The deployer is attached to the second stage of a Delta II which acts as a stabilized platform for the deployment of tethered payloads. SEDS is particularly suitable for complementing the Tethered Satellite missions by providing a flexible system for experimenting with the tether-in-space technology. SEDS can also provide a convenient way for testing instruments and/or procedures which require the use of long tethers.

  3. The ElectroDynamic Delivery Experiment (EDDE)

    NASA Astrophysics Data System (ADS)

    Pearson, Jerome; Levin, Eugene; Oldson, John; Carroll, Joseph

    2001-02-01

    The ElectroDynamic Delivery Experiment (EDDE) is proposed for a space demonstration. EDDE consists of an autonomous space vehicle powered by lightweight solar arrays, a bi-directional electrodynamic tether, and batteries for power leveling. The EDDE vehicle can modify its orbit repeatedly without rocket fuel, and can change all six orbital parameters by modulating and reversing the current flow in the conducting tether. The base spacecraft is connected to the service module by a 6-km-long electrodynamic tether, and is designed for 2 kW of power and a total mass of 180 kg. Tether lifetime of several years is achieved with a two-strand caduceus, with the strands connected every few meters. Tether libration is minimized by mass distribution and by active current control. The vehicle and tether system concepts are developed, the operational envelopes are examined, and potential applications are evaluated. The EDDE vehicle is about twice as fast as ion rockets for high-inclination orbital plane changes, and has much higher maximum delta-V capability. A proof-of-concept experiment is proposed for a low-cost space demonstration. This on-orbit experiment could include additional secondary payloads; for example, EDDE could place low-ΔV, free-flying inspectors into arbitrary orbits from which they could approach selected objects without concern for tether dynamics or interference. .

  4. Shuttle-tethered satellite system definition study extension

    NASA Technical Reports Server (NTRS)

    1980-01-01

    A system requirements definition and configuration study (Phase B) of the Tethered Satellite System (TSS) was conducted during the period 14 November 1977 to 27 February 1979. Subsequently a study extension was conducted during the period 13 June 1979 to 30 June 1980, for the purpose of refining the requirements identified during the main phase of the study, and studying in some detail the implications of accommodating various types of scientific experiments on the initial verification flight mission. An executive overview is given of the Tethered Satellite System definition developed during the study. The results of specific study tasks undertaken in the extension phase of the study are reported. Feasibility of the Tethered Satellite System has been established with reasonable confidence and the groundwork laid for proceeding with hardware design for the verification mission.

  5. A low earth orbit skyhook tether transportation system

    NASA Technical Reports Server (NTRS)

    Penzo, Paul A.

    1988-01-01

    This paper discusses the design concept of a structure, called the Skyhook Tether Transportation System (STTS) which may be used to transport mass to higher or lower orbits or to capture objects from higher or lower orbits. An analysis is presented for the possibility of the STTS to perform the function of transporting masses suborbitally, capturing the objects, and then releasing them to a higher orbit, the GEO, the moon, or for an escape. It is shown that, although the possibility of such a system is limited by the tether strength, even a modest system can yield considerable benefits in propellant savings if it is used in combination with chemical propulsion.

  6. Analytical investigation of the dynamics of tethered constellations in Earth orbit, phase 2

    NASA Technical Reports Server (NTRS)

    Lorenzini, Enrico C.; Gullahorn, Gordon E.; Cosmo, Mario L.; Estes, Robert D.; Grossi, Mario D.

    1994-01-01

    This final report covers nine years of research on future tether applications and on the actual flights of the Small Expendable Deployment System (SEDS). Topics covered include: (1) a description of numerical codes used to simulate the orbital and attitude dynamics of tethered systems during station keeping and deployment maneuvers; (2) a comparison of various tethered system simulators; (3) dynamics analysis, conceptual design, potential applications and propagation of disturbances and isolation from noise of a variable gravity/microgravity laboratory tethered to the Space Station; (4) stability of a tethered space centrifuge; (5) various proposed two-dimensional tethered structures for low Earth orbit for use as planar array antennas; (6) tethered high gain antennas; (7) numerical calculation of the electromagnetic wave field on the Earth's surface on an electrodynamically tethered satellite; (8) reentry of tethered capsules; (9) deployment dynamics of SEDS-1; (10) analysis of SEDS-1 flight data; and (11) dynamics and control of SEDS-2.

  7. Tethered aerostat VLF/LF transmitter system design considerations

    NASA Astrophysics Data System (ADS)

    Crawford, Richard L.; Lamanna, Thomas C.; Jordon, Kenneth L.

    1993-05-01

    A tethered aerostat VLF/LF transmitter (TAVT) system is a cost-effective, survivable alternative for reconstituting VLF/LF communications connectivity to strategic forces in a post-attack environment. This paper describes the tradeoff design considerations that led to recommending a TAVT system with a 50,000-cubic-foot aerostat and a 5,000-foot tether used as the transmitting radio antenna. The major tradeoff factors considered in choosing this design were: survivability, transportability, coverage area, operating frequency range, maximum effective radiated power, cost, and corona avoidance.

  8. Application of the Trio-Tri-Star Carpal Wrist for use in a Solar Array Tracking Mechanism for the Momentum-eXchange/Electrodynamic Reboost (MXER) Tether Concept

    NASA Technical Reports Server (NTRS)

    Robertson, Jeffrey

    2006-01-01

    This paper describes the application of the Trio-Tri-Star Carpal Wrist to the Momentum Exchange Electro-Dynamic Re-boost (MXER) tether, an advanced space transportation concept being developed by the In-Space Propulsion Technology Office at NASA s Marshall Space Flight Center in Huntsville, Alabama. Dr. Joseph Bonometti and Mr. Kirk Sorensen are the principal engineers. In the paper, a brief overview of the MXER concept is given, with an emphasis on the design problem that this wrist is designed to address. The Trio-Tri-Star Carpal Wrist, a three degree of freedom parallel manipulator, invented by Dr. Stephen J. Canfield of Tennessee Tech University, is described with an overview of wrist geometry, kinematics, and stress analysis. A working model of the wrist was assembled at MSFC using Dr. Canfield s prototype to demonstrate its operation. Finally, a design description and supporting analysis of a MXER flight concept wrist is given, with recommendations for future development work.

  9. Tethered satellite system control using electromagnetic forces and reaction wheels

    NASA Astrophysics Data System (ADS)

    Alandi Hallaj, Mohammad Amin; Assadian, Nima

    2015-12-01

    In this paper a novel non-rotating space tethered configuration is introduced which its relative positions controlled using electromagnetic forces. The attitude dynamics is controlled by three reaction wheels in the body axes. The nonlinear coupled orbital dynamics of a dumbbell tethered satellite formation flight are derived through a constrained Lagrangian approach. These equations are presented in the leader satellite orbital frame. The tether is assumed to be mass-less and straight, and the J2 perturbation is included to the analysis. The forces and the moments of the electromagnetic coils are modeled based on the far-filed model of the magnetic dipoles. A guidance scheme for generating the desired positions as a function of time in Cartesian form is presented. The satellite tethered formation with variable length is controlled utilizing a linear controller. This approach is applied to a specified scenario and it is shown that the nonlinear guidance method and the linear controller can control the nonlinear system of the tethered formation and the results are compared with optimal control approach.

  10. Dynamics and control of the tether elevator/crawler system

    NASA Technical Reports Server (NTRS)

    Lorenzini, E. C.; Cosmo, M.; Vetrella, S.; Moccia, A.

    1989-01-01

    This paper investigates the dynamics and acceleration levels of a new tethered system for micro- and variable-gravity applications. The system consists of two platforms tethered on opposite sides to the Space Station. A fourth platform, the elevator, is placed in between the Space Station and the upper platform. Variable-g levels on board the elevator are obtained by moving this facility along the upper tether, while microgravity experiments are carried out on board the Space Station. By controlling the length of the lower tether the position of the system center of mass can be maintained on board the Space Station despite variations of the system's distribution of mass. The paper illustrates the mathematical model, the environmental perturbations and the control techniques which have been adopted for the simulation and control of the system dynamics. Two sets of results from two different simulation runs are shown. The first set shows the system dynamics and the acceleration spectra on board the Space Station and the elevator during station-keeping. The second set of results demonstrates the capability of the elevator to attain a preselected g-level.

  11. Satellite Particle Collection During Active States of the Tethered Satellite System (TSS)

    NASA Technical Reports Server (NTRS)

    Wright, K. H., Jr.; Stone, N. H.; Winningham, J. D.; Gurgiolo, C.; Bonifazi, C.; Gilchrist, B.; Mariani, F.; Hardy, D.

    1996-01-01

    The reflight of the Tethered Satellite System (TSS-1R) was carried aboard the Space Shuttle Columbia on February 22, 1996. After deploying a day later than planned, the satellite almost reached its full deployed distance before the tether broke. Data was collected for over 5 hours during deployment out to a distance of 19.7 km. Maximum emf attained during deployment was 3700 V while the maximum current achieved was just under 0.5 A. The current collected was factors of 2 to 4 greater than the predictions of the conventional Parker-Murphy theory. The microscopic view of the collection process at the satellite showed exotic behavior with the existence of 100 - 200 eV suprathermal electrons and significant spin phase modulation of the electron fluxes. Although the data set acquired from TSS- 1R was considerably less than planned, the quality of the data allows one of the main goals of the mission to be met--characterizing the system I-V response. A "quick look" assessment of the data has already shown that an understanding of the TSS-1R electrodynamic behavior will require modification of the standard picture of current collection in space plasmas

  12. Applications of Tethers in Space

    NASA Technical Reports Server (NTRS)

    Cron, A. C.

    1985-01-01

    The proceedings of the first workshop on applications of tethers in space are summarized. The workshop gathered personalities from industry, academic institutions and government to discuss the relatively new area of applied technology of very long tethers in space to a broad spectrum of future space missions. A large number of tethered concepts and configurations was presented covering electrodynamic interaction tethers, tethered transportation through angular momentum exchange, tethered constellations, low gravity utilization, applicable technology, and tethered test facilities. Specific recommendations were made to NASA in each area.

  13. The tethered satellite system for low density aerothermodynamics studies

    NASA Technical Reports Server (NTRS)

    Carlomagno, Giovanni M.; De Luca, Luigi; Siemers, P. M., III; Wood, George M., Jr.

    1986-01-01

    The feasibility of the operation of the Tethered Satellite System (TSS) as a continuous open wind tunnel for low-density aerothermodynamic studies (applicable to the design of hypersonic space vehicles including STARFAC, AOTV, and ERV) is considered. The Shuttle Continuous Open Wind Tunnel (SCOWT) program, for the study of the energy and momentum transfer between the tethered satellite and its environmental medium during the TSS/2 mission, is described. Instrumentation and TSS design requirements to meet SCOWT objectives are also considered. SCOWT will provide information on the gasdynamic processes occurring downstream of the bow wave standing in front of the TS, the chemistry and physics of the upper atmosphere related to satellite aerothermodynamics, and TSS's overall experimental envelope of operation.

  14. Tethered Vehicle Control and Tracking System

    NASA Technical Reports Server (NTRS)

    North, David D. (Inventor); Aull, Mark J. (Inventor)

    2014-01-01

    A kite system includes a kite and a ground station. The ground station includes a sensor that can be utilized to determine an angular position and velocity of the kite relative to the ground station. A controller utilizes a fuzzy logic control system to autonomously fly the kite. The system may include a ground station having powered winding units that generate power as the lines to the kite are unreeled. The control system may be configured to fly the kite in a crosswind trajectory to increase line tension for power generation. The sensors for determining the position of the kite are preferably ground-based.

  15. Operator's Manual for SHEBA Powered Tether Balloon System

    NASA Technical Reports Server (NTRS)

    Lappen, Cara-Lyn; Randall, David A.

    1998-01-01

    The Surface Heat and Energy Budget of the Arctic (SHEBA) was an intensive field project which took place in the Arctic Ocean from October 1997 through October 1998. Its purpose was to measure as many facets of the Arctic environment as possible so that we would be able to better understand the interaction between the ice, atmosphere, and ocean and their interactions with global climate. One aspect of the atmospheric field component was launching tethered balloons to monitor the profiles of temperature, wind, pressure, and humidity, as well as examine the vertical structure of cloud droplet sizes and distributions. The tethered balloon that we used was one specially designed for use in freezing climates by SPEC Corporation in Boulder, Colorado. A special winch that was able to withstand Arctic temperature and weather became necessary when the testing of simple winch systems used in warmer climates failed under these extreme conditions. The purpose of this manual is to acquaint any new user to the powered tethered balloon system deployed at the The Surface Heat and Energy Budget of the Arctic (SHEBA ice camp. It includes a description of the preparations necessary to get ready for a launch, the mechanics of the actual launch, and an account of the proper procedure for taking down the equipment when finished. It will also include tips on how to minimize potential equipment failures, some trouble shooting, and some safety ideas. This manual is designed so that new operators can use the system with minimal previous training. At the end of this manual, the reader will find a quick checklist.

  16. Membrane tethering

    PubMed Central

    Chia, Pei Zhi Cheryl

    2014-01-01

    Membrane trafficking depends on transport vesicles and carriers docking and fusing with the target organelle for the delivery of cargo. Membrane tethers and small guanosine triphosphatases (GTPases) mediate the docking of transport vesicles/carriers to enhance the efficiency of the subsequent SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor)-mediated fusion event with the target membrane bilayer. Different classes of membrane tethers and their specific intracellular location throughout the endomembrane system are now well defined. Recent biochemical and structural studies have led to a deeper understanding of the mechanism by which membrane tethers mediate docking of membrane carriers as well as an appreciation of the role of tethers in coordinating the correct SNARE complex and in regulating the organization of membrane compartments. This review will summarize the properties and roles of membrane tethers of both secretory and endocytic systems. PMID:25343031

  17. The development of optimal control laws for orbiting tethered platform systems

    NASA Technical Reports Server (NTRS)

    Bainum, P. M.; Woodard, S.; Juang, J.-N.

    1986-01-01

    A mathematical model of the open and closed loop in-orbit plane dynamics of a space platform-tethered-subsatellite system is developed. The system consists of a rigid platform from which an (assumed massless) tether is deploying (retrieving) a subsatellite from an attachment point which is, in general, offset from the platform's mass center. A Lagrangian formulation yields equations describing platform pitch, subsatellite tether-line swing, and varying tether length motions. These equations are linearized about the nominal station keeping motion. Control can be provided by both modulation of the tether tension level and by a momentum type platform-mounted device; system controllability depends on the presence of both control inputs. Stability criteria are developed in terms of the control law gains, the platform inertia ratio, and tether offset parameter. Control law gains are obtained based on linear quadratic regulator techniques. Typical transient responses of both the state and required control effort are presented.

  18. Prospective of tethered system in space station operations

    NASA Astrophysics Data System (ADS)

    Vallerani, E.; Manarini, G.; Lorenzini, E.

    1983-10-01

    The use of satellite tethers for satellite launching and space station constellations is described. The tethers permit exploitation of the gravity gradient effect for stabilization, and also serve as momentum transfer devices between spacecraft at either end. Satellites can be launched into higher orbits when released outwards (away from the earth) by the unreeling of the tether line. The tether can also serve for rendezvous with a satellite in a higher orbit, allowing soft-docking to occur and enhancing the safety of the Orbiter. Modules of a space station can be separated and stabilized in constellations through the use of tethers. Spinning the tethers about their vertical axis will keep the tethers stretched. Free-flying platforms can be raised or lowered to proper orbits without propulsive maneuvers. Finally, fluid can be pumped downward between spacecraft without using on-board power.

  19. Study of Plasma Motor Generator (PMG) tether system for orbit reboost

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Detailed designs were produced for a 2 kW plasma motor generator tether system based largely on existing hardware and hardware designs. Specifically, the hollow cathode design and electronics are derived from ion propulsion equipment. A prototype tether was constructed and will be tested for deployment, strength, resistance to breakage and abrasion and electrical properties. In addition, laboratory development models of the electronics will be used to operate two plasma motor generator hollow cathode assemblies with this tether to verify electrical performance parameters for the complete system. Results show that a low cost demonstration of a plasma motor generator tether system appears to be feasible by the middle of the 1990s.

  20. Prospective lunar, planetary and deep space applications of tethers

    NASA Technical Reports Server (NTRS)

    Penzo, Paul A.

    1987-01-01

    Projected flights of an internationally managed Tethered Satellite System from the Space Shuttle in the early 1990s will investigate the behavior, first, of an insulated conducting wire 20 km long as it travels at orbital speeds through the ionosphere and earth magnetic field; subsequently, a nonconducting tether will be used to lower an instrumented 'subsatellite' 100 km downward to investigate upper-atmosphere conditions. Further consideration is presently given to other scientific, electrodynamic, transportational, and artificial gravity-generating applications of the tether concept.

  1. Configuration maintaining control of three-body ring tethered system based on thrust compensation

    NASA Astrophysics Data System (ADS)

    Huang, Panfeng; Liu, Binbin; Zhang, Fan

    2016-06-01

    Space multi-tethered systems have shown broad prospects in remote observation missions. This paper mainly focuses on the dynamics and configuration maintaining control of space spinning three-body ring tethered system for such mission. Firstly, we establish the spinning dynamic model of the three-body ring tethered system considering the elasticity of the tether using Newton-Euler method, and then validate the suitability of this model by numerical simulation. Subsequently, LP (Likins-Pringle) initial equilibrium conditions for the tethered system are derived based on rigid body's equilibrium theory. Simulation results show that tether slack, snapping and interaction between the tethers exist in the three-body ring system, and its' configuration can not be maintained without control. Finally, a control strategy based on thrust compensation, namely thrust to simulate tether compression under LP initial equilibrium conditions is designed to solve the configuration maintaining control problem. Control effects are verified by numerical simulation compared with uncontrolled situation. Simulation results show that the configuration of the three-body ring tethered system could maintain under this active control strategy.

  2. Catalyst system comprising a first catalyst system tethered to a supported catalyst

    DOEpatents

    Angelici, Robert J.; Gao, Hanrong

    1998-08-04

    The present invention provides new catalyst formats which comprise a supported catalyst tethered to a second and different catalyst by a suitable tethering ligand. A preferred system comprises a heterogeneous supported metal catalyst tethered to a homogeneous catalyst. This combination of homogeneous and heterogeneous catalysts has a sufficient lifetime and unusually high catalytic activity in arene hydrogenations, and potentially many other reactions as well, including, but not limited to hydroformylation, hydrosilation, olefin oxidation, isomerization, hydrocyanation, olefin metathesis, olefin polymerization, carbonylation, enantioselective catalysis and photoduplication. These catalysts are easily separated from the products, and can be reused repeatedly, making these systems very economical.

  3. Catalyst system comprising a first catalyst system tethered to a supported catalyst

    DOEpatents

    Angelici, R.J.; Gao, H.

    1998-08-04

    The present invention provides new catalyst formats which comprise a supported catalyst tethered to a second and different catalyst by a suitable tethering ligand. A preferred system comprises a heterogeneous supported metal catalyst tethered to a homogeneous catalyst. This combination of homogeneous and heterogeneous catalysts has a sufficient lifetime and unusually high catalytic activity in arene hydrogenations, and potentially many other reactions as well, including, but not limited to hydroformylation, hydrosilication, olefin oxidation, isomerization, hydrocyanidation, olefin metathesis, olefin polymerization, carbonylation, enantioselective catalysis and photoduplication. These catalysts are easily separated from the products, and can be reused repeatedly, making these systems very economical. 2 figs.

  4. Selected tether applications in space: An analysis of five selected concepts

    NASA Astrophysics Data System (ADS)

    1984-07-01

    Ground rules and assumptions; operations; orbit considerations/dynamics; tether system design and dynamics; functional requirements; hardware concepts; and safety factors are examined for five scenarios: tethered effected separation of an Earth bound shuttle from the space station; tether effected orbit boost of a spacecraft (AXAF) into its operational orbit from the shuttle; an operational science/technology platform tether deployed from space station; a tether mediated rendezvous involving an OMV tether deployed from space station to rendezvous with an aerobraked OTV returning to geosynchronous orbit from a payload delivery mission; and an electrodynamic tether used in a dual motor/generator mode to serve as the primary energy storage facility for space station.

  5. Selected tether applications in space: An analysis of five selected concepts

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Ground rules and assumptions; operations; orbit considerations/dynamics; tether system design and dynamics; functional requirements; hardware concepts; and safety factors are examined for five scenarios: tethered effected separation of an Earth bound shuttle from the space station; tether effected orbit boost of a spacecraft (AXAF) into its operational orbit from the shuttle; an operational science/technology platform tether deployed from space station; a tether mediated rendezvous involving an OMV tether deployed from space station to rendezvous with an aerobraked OTV returning to geosynchronous orbit from a payload delivery mission; and an electrodynamic tether used in a dual motor/generator mode to serve as the primary energy storage facility for space station.

  6. Applications of tethers for planetary missions

    NASA Technical Reports Server (NTRS)

    Penzo, P.

    1986-01-01

    Ideas of deep space exploration are considered. The role of tethers in deep space is of most concern. A proposal of a tethered instrument package in orbit about the Moon is explored. The idea of a sling on the surface of the Moon which would take solar energy and build up momentum of the sling is studied. The NASA idea of a Mars Aeronomy Orbiter which would use a tether to enhance the planned Mars Orbiter is reviewed. It is also proposed that a tether can be attached to an asteroid during a spacecraft flyby. The possibility of using tethers to provide a transportation system for payloads which are coming to the surface from escape, and which are leaving Mars and escaping from Mars itself is also studied. A proposal from the Jet Propulsion Lab. on collecting comet or asteroid samples and returning them to Earth is reviewed. A tethered penetrator which could collect core samples is the proposed way. Also considered is the area of electrodynamic tethers at Jupiter.

  7. Effects of damping on the control dynamics of the space shuttle based on tethered systems

    NASA Technical Reports Server (NTRS)

    Modi, V. J.

    1986-01-01

    The analysis of the effects of damping on the control dynamics of the space shuttle based on tethered systems suggest that a relatively simple point mass model can provide useful information concering librational dynamics during development and retrieval of the tethered satellites. The results show that a nonlinear tension control strategy in conjunction with a suitable choice of gains and realistic damping can lead to stable retrieval maneuver with amplitudes in pitch and roll limited to acceptable values. Longitudinal and lateral vibrations of the tether are strongly coupled and can lead to the slackening of the tether. Tether vibrations can be controlled quite effectively by speeding up the retrieval at smaller tether length and/or using thruster.

  8. Dynamics of a Tether System Connected to an Irregularly Shaped Celestial Body

    NASA Astrophysics Data System (ADS)

    Jalali Mashayekhi, Mohammad; K. Misra, Arun; Keshmiri, Mehdi

    2016-04-01

    The problem of pendular oscillations of a tether attached to an irregularly shaped celestial body is studied in this paper. The dynamic analysis of the system is performed by examining the phase plane trajectories. The effect of the tether length as well as the higher order terms in the gravitational potential of the celestial body on the tether dynamics is investigated. It is demonstrated that consideration of the finite size of the celestial body can have significant effects on the tether dynamics, while the effect of the asphericity of the celestial body on the tether dynamics is negligible. This study is of practical relevance for asteroid deflection using tethers, as well as for the development of space elevators on small planets/moons.

  9. Dynamics of a Tether System Connected to an Irregularly Shaped Celestial Body

    NASA Astrophysics Data System (ADS)

    Jalali Mashayekhi, Mohammad; Misra, Arun K.; Keshmiri, Mehdi

    2016-09-01

    The problem of pendular oscillations of a tether attached to an irregularly shaped celestial body is studied in this paper. The dynamic analysis of the system is performed by examining the phase plane trajectories. The effect of the tether length as well as the higher order terms in the gravitational potential of the celestial body on the tether dynamics is investigated. It is demonstrated that consideration of the finite size of the celestial body can have significant effects on the tether dynamics, while the effect of the asphericity of the celestial body on the tether dynamics is negligible. This study is of practical relevance for asteroid deflection using tethers, as well as for the development of space elevators on small planets/moons.

  10. Tethered elevator and platforms as space station facilities: Systems studies and demonstrative experiments

    NASA Technical Reports Server (NTRS)

    1986-01-01

    Several key concepts of the science and applications tethered platforms were studied. Some conclusions reached are herein listed. Tether elevator and platform could improve the space station scientific and applicative capabilities. The space elevator presents unique characteristics as microgravity facility and as a tethered platform servicing vehicle. Pointing platforms could represent a new kind of observation facility for large class of payloads. The dynamical, control and technological complexity of these concepts advised demonstrative experiments. The on-going tethered satellite system offers the opportunity to perform such experiments. And feasibility studies are in progress.

  11. Out-of-plane librations of spinning tethered satellite systems

    NASA Astrophysics Data System (ADS)

    Ellis, Joshua R.; Hall, Christopher D.

    2010-01-01

    We analyze the out-of-plane librations of a tethered satellite system that is nominally rotating in the orbit plane. To isolate the librational dynamics, the system is modeled as two point masses connected by a rigid rod with the system mass center constrained to an unperturbed circular orbit. For small out-of-plane librations, the in-plane motion is unaffected by the out-of-plane librations and a solution for the in-plane motion is determined in terms of Jacobi elliptic functions. This solution is used in the linearized equation for the out-of-plane librations, resulting in a Hill's equation. Floquet theory is used to analyze the Hill's equation, and we show that the out-of-plane librations are unstable for certain ranges of in-plane spin rate. For relatively high in-plane spin rates, the out-of-plane librations are stable, and the Hill's equation can be approximated by a Mathieu's equation. Approximate solutions to the Mathieu's equation are determined, and we analyze the dominant characteristics of the out-of-plane librations for high in-plane spin rates. The results obtained from the analysis of the linearized equations of motion are compared to numerical simulations of the nonlinear equations of motion, as well as numerical simulations of a more realistic system model that accounts for tether flexibility. The instabilities discovered from the linear analysis are present in both the nonlinear system and the more realistic system model. The approximate solutions for the out-of-plane librations compare well to the nonlinear system for relatively high in-plane rotation rates, and also capture the significant qualitative behavior of the flexible system.

  12. On the dynamics and control of tethered satellite systems

    NASA Technical Reports Server (NTRS)

    Modi, Vinod J.; Misra, Arun K.; Ng, Alfred C.; Lakshmanan, Prem K.

    1992-01-01

    The rigid body dynamics and control of the tether, subsatellite and space platform are analyzed, during deployment, stationkeeping and retrieval phases using the Linear Quadratic Regulator (LQR) approach, accounting for the mass of the tether as well as a three dimensional offset of its point of attachment. The strategies employ tension in the tether line, thrusters, motion of the offset of the tether attachment point or their hybrid combinations. An assessment of the relative merit suggests the thruster-offset hybrid controller to be the most effective in damping given disturbances.

  13. Evaluation of a six-DOF electrodynamic shaker system.

    SciTech Connect

    Gregory, Danny Lynn; Smallwood, David Ora

    2009-03-01

    The paper describes the preliminary evaluation of a 6 degree of freedom electrodynamic shaker system. The 8 by 8 inch (20.3 cm) table is driven by 12 electrodynamic shakers producing motion in all 6 rigid body modes. A small electrodynamic shaker system suitable for small component testing is described. The principal purpose of the system is to demonstrate the technology. The shaker is driven by 12 electrodynamic shakers each with a force capability of about 50 lbs (220 N). The system was developed through an informal cooperative agreement between Sandia National Laboratories, Team Corp. and Spectral Dynamics Corporation. Sandia provided the laboratory space and some development funds. Team provided the mechanical system, and Spectral Dynamics provided the control system. Spectral Dynamics was chosen to provide the control system partly because of their experience in MIMO control and partly because Sandia already had part of the system in house. The shaker system was conceived and manufactured by TEAM Corp. Figure 1 shows the overall system. The vibration table, electrodynamic shakers, hydraulic pumps, and amplifiers are all housed in a single cabinet. Figure 2 is a drawing showing how the electrodynamic shakers are coupled to the table. The shakers are coupled to the table through a hydraulic spherical pad bearing providing 5 degrees of freedom and one stiff degree of freedom. The pad bearing must be preloaded with a static force as they are unable to provide any tension forces. The horizontal bearings are preloaded with steel springs. The drawing shows a spring providing the vertical preload. This was changed in the final design. The vertical preload is provided by multiple strands of an O-ring material as shown in Figure 4. Four shakers provide excitation in each of the three orthogonal axes. The specifications of the shaker are outlined in Table 1. Four shakers provide inputs in each of the three orthogonal directions. By choosing the phase relationships

  14. Dynamic stability of electrodynamic maglev systems

    SciTech Connect

    Cai, Y.; Chen, S.S.; Mulcahy, T.M.; Rote, D.M.

    1997-01-01

    Because dynamic instabilities are not acceptable in any commercial maglev system, it is important to consider dynamic instability in the development of all maglev systems. This study considers the stability of maglev systems based on mathematical models and experimental data. Divergence and flutter are obtained for coupled vibration of a three-degree-of-freedom maglev vehicle on a guideway consisting of double L-shaped aluminum segments. The theory and analysis for motion-dependent magnetic-force-induced instability developed in this study provides basic stability characteristics and identifies future research needs for maglev systems.

  15. Gravito-electrodynamics and the structure of planetary ring systems

    NASA Technical Reports Server (NTRS)

    Mendis, D. A.

    1984-01-01

    Recent spacecraft observations of the Saturnian and Jovian ring systems have highlighted a plethora of interesting new phenomena associated with those regions containing fine (micron and sub-micron sized) dust. Recognizing that these dust grains, by virtue of being immersed within the planetary magnetospheres, are electrostatically charged to the point that they experience comparable gravitational and electric forces, a new 'gravito-electrodynamic' theory has been developed to describe their dynamics. This theory has been successful in explaining all these phenomena in a systematic way. In this review, the basic model and its range of validity are outlined, and its application to the Saturnian and Jovian ring systems are discussed.

  16. Gravito-electrodynamics and the structure of planetary ring systems

    NASA Astrophysics Data System (ADS)

    Mendis, D. A.

    1984-08-01

    Recent spacecraft observations of the Saturnian and Jovian ring systems have highlighted a plethora of interesting new phenomena associated with those regions containing fine (micron and sub-micron sized) dust. Recognizing that these dust grains, by virtue of being immersed within the planetary magnetospheres, are electrostatically charged to the point that they experience comparable gravitational and electric forces, a new 'gravito-electrodynamic' theory has been developed to describe their dynamics. This theory has been successful in explaining all these phenomena in a systematic way. In this review, the basic model and its range of validity are outlined, and its application to the Saturnian and Jovian ring systems are discussed.

  17. Tethers in space handbook

    NASA Technical Reports Server (NTRS)

    Reese, T. G.; Baracat, W. A.; Butner, C. L.

    1986-01-01

    The handbook provides a list and description of ongoing tether programs. This includes the joint U.S.-Italy demonstration project, and individual U.S. and Italian studies and demonstration programs. An overview of the current activity level and areas of emphasis in this emerging field is provided. The fundamental physical principles behind the proposed tether applications are addressed. Four basic concepts of gravity gradient, rotation, momentum exchange, and electrodynamics are discussed. Information extracted from literature, which supplements and enhances the tether applications is also presented. A bibliography is appended.

  18. The development of optimal control laws for orbiting tethered platform systems

    NASA Technical Reports Server (NTRS)

    Bainum, P. M.

    1986-01-01

    A mathematical model of the open and closed loop in orbit plane dynamics of a space platform-tethered-subsatellite system is developed. The system consists of a rigid platform from which an (assumed massless) tether is deploying (retrieving) a subsatellite from an attachment point which is, in general, offset from the platform's mass center. A Langrangian formulation yields equations describing platform pitch, subsatellite tetherline swing, and varying tether length motions. These equations are linearized about the nominal station keeping motion. Control can be provided by both modulation of the tether tension level and by a momentum type platform-mounted device; system controllability depends on the presence of both control inputs. Stability criteria are developed in terms of the control law gains, the platform inertia ratio, and tether offset parameter. Control law gains are obtained based on linear quadratic regulator techniques. Typical transient responses of both the state and required control effort are presented.

  19. Dual-keel electrodynamic maglev system

    SciTech Connect

    He, J.; Wang, Z.; Rote, D.M.; Coffey, H.T.; Hull, J.R.; Mulcahy, T.M.; Cai, Y.

    1995-12-31

    A propulsion and stabilization system with a plurality of superconducting magnetic devices affixed to the dual-keels of a vehicle, where the superconducting magnetic devices produce a magnetic field when energized. The system also includes a plurality of figure-eight shaped null-flux coils affixed to opposing vertical sides of slots in a guideway. The figure-eight shaped null-flux coils are vertically oriented, laterally cross-connected in parallel, longitudinally connected in series, and continue the length of the vertical slots providing levitation and guidance force. An external power source energizes the figure-eight shaped null-flux coils to create a magnetic traveling wave that interacts with the magnetic field produced by the superconducting magnets to impart motion to the vehicle.

  20. Dual-keel electrodynamic maglev system

    DOEpatents

    He, Jianliang; Wang, Zian; Rote, Donald M.; Coffey, Howard T.; Hull, John R.; Mulcahy, Thomas M.; Cal, Yigang

    1996-01-01

    A propulsion and stabilization system with a plurality of superconducting magnetic devices affixed to the dual-keels of a vehicle, where the superconducting magnetic devices produce a magnetic field when energized. The system also includes a plurality of figure-eight shaped null-flux coils affixed to opposing vertical sides of slots in a guideway. The figure-eight shaped null-flux coils are vertically oriented, laterally cross-connected in parallel, longitudinally connected in series, and continue the length of the vertical slots providing levitation and guidance force. An external power source energizes the figure-eight shaped null-flux coils to create a magnetic traveling wave that interacts with the magnetic field produced by the superconducting magnets to impart motion to the vehicle.

  1. Dual-keel electrodynamic maglev system

    DOEpatents

    He, J.L.; Wang, Z.; Rote, D.M.; Coffey, H.T.; Hull, J.R.; Mulcahy, T.M.; Cal, Y.

    1996-12-24

    A propulsion and stabilization system is disclosed with a plurality of superconducting magnetic devices affixed to the dual-keels of a vehicle, where the superconducting magnetic devices produce a magnetic field when energized. The system also includes a plurality of figure-eight shaped null-flux coils affixed to opposing vertical sides of slots in a guideway. The figure-eight shaped null-flux coils are vertically oriented, laterally cross-connected in parallel, longitudinally connected in series, and continue the length of the vertical slots providing levitation and guidance force. An external power source energizes the figure-eight shaped null-flux coils to create a magnetic traveling wave that interacts with the magnetic field produced by the superconducting magnets to impart motion to the vehicle. 6 figs.

  2. Electrodynamics of strongly correlated electron systems

    NASA Astrophysics Data System (ADS)

    Dordevic, Sasa V.

    2002-09-01

    In this thesis we study a variety of condensed matter systems with strongly correlated electrons, i.e. systems in which the electron-electron interactions cannot be ignored like in conventional metals, (gold, aluminum, copper, etc.). Infrared spectroscopy has proven to be a powerful tool for studying such systems. The latter experimental technique probes all excitations is solids that have a dipole moment associated with them, such as gap excitations, interband transitions, phonons, polarons, magnons etc. Strong electron correlations lead to a variety of interesting physical phenomena at low temperatures. In copper ox ides superconductivity sets in below an unprecedently high critical temperature, Tc. The mechanism of this unusual phenomenon is still unclear. In this thesis we discuss energy scales from which the superconducting condensate is collected and the response of cuprates to an external magnetic field applied parallel to the CuO2 planes. In so-called heavy fermion metals a coherent ground state develops at low temperatures where the electrons appear to have large effective mass, typically 50--1,000 free electron masses. We show that magnetic interactions play an important role for the mass renormalization in heavy fermion metals. In transition metal dichalcogenides reduced dimensionality of the electron gas leads to significant anisotropy of the electron-phonon interaction.

  3. Spin Pumping in Electrodynamically Coupled Magnon-Photon Systems.

    PubMed

    Bai, Lihui; Harder, M; Chen, Y P; Fan, X; Xiao, J Q; Hu, C-M

    2015-06-01

    We use electrical detection, in combination with microwave transmission, to investigate both resonant and nonresonant magnon-photon coupling at room temperature. Spin pumping in a dynamically coupled magnon-photon system is found to be distinctly different from previous experiments. Characteristic coupling features such as modes anticrossing, linewidth evolution, peculiar line shape, and resonance broadening are systematically measured and consistently analyzed by a theoretical model set on the foundation of classical electrodynamic coupling. Our experimental and theoretical approach paves the way for pursuing microwave coherent manipulation of pure spin current via the combination of spin pumping and magnon-photon coupling. PMID:26196640

  4. Electrodynamic processes in the ring system of Saturn

    NASA Technical Reports Server (NTRS)

    Mendis, D. A.; Hill, J. R.; Ip, W.-H.; Goertz, C. K.; Gruen, E.

    1984-01-01

    A number of recently observed Saturn ring phenomena are discussed in terms of their electrodynamic implications. Voyager 1 and 2 observations of the rotating near-radial spokes in the B Ring, waves and braids of the F Ring, and discrete episodic bursts of broadband radio emission, claimed by some to originate in a ring, are addressed. Several other phenomena are considered, including the origin and evolution of the diffuse E Ring and G Ring (which appear to be composed of fine dust), as well as the existence of a number of sharp discontinuities in the main ring system, within the context of gravitoelectrodynamics of charged dust in the magnetosphere.

  5. Study of Japanese electrodynamic-suspension maglev systems

    NASA Astrophysics Data System (ADS)

    He, J. L.; Rote, D. M.; Coffey, H. T.

    1994-04-01

    This report presents the results of a study of the Japanese MLU magnetic levitation (maglev) system. The development of the MLU system is reviewed, and the dynamic circuit model then is introduced and applied to the figure-eight-shaped null-flux coil suspension system. Three different types of figure-eight-shaped null-flux suspension systems are discussed in detail: (1) the figure-eight-shaped null-flux coil suspension system without cross-connection; (2) the combined suspension and guidance system; and (3) the combined propulsion, levitation, and guidance system. The electrodynamic suspension maglev systems developed in Japan seem to be very promising and could result in a commercial application in the near future.

  6. Study of Japanese electrodynamic-suspension maglev systems

    SciTech Connect

    He, J.L.; Rote, D.M.; Coffey, H.T.

    1994-04-01

    This report presents the results of a study of the Japanese MLU magnetic-levitation (maglev) system. The development of the MLU system is reviewed, and the dynamic circuit model then is introduced and applied to the figure-eight-shaped null-flux coil suspension system. Three different types of figure-eight-shaped null-flux suspension systems are discussed in detail: (1) the figure-eight-shaped null-flux coil suspension system without cross-connection; (2) the combined suspension and guidance system; and (3) the combined propulsion, levitation, and guidance system. The electrodynamic-suspension maglev systems developed in Japan seem to be very promising and could result in a commercial application in the near future.

  7. Spin pumping in electrodynamically coupled magnon-photon systems

    NASA Astrophysics Data System (ADS)

    Bai, Lihui

    The electronics industry is quickly approaching the limitation of Moore's Law due to Joule heating in high density-integrated devices. To achieve new higher-speed devices and reduce energy consumption, researchers are turning to spintronics where the intrinsic spin, rather than the charge of electrons, is used to carry information in devices. Advances in spintronics have led to the discovery of giant magnetoresistance (GMR), spin transfer torque etc. Another subject, cavity electrodynamics, promises a completely new quantum algorithm by studying the properties of a single electron interacting with photons inside of a cavity. By merging both spintronics and cavity electrodynamics, a new cutting edge field called Cavity Spintronics is forming, which draws on the advantages of both subjects to develop new spintronics devices utilizing light-matter interaction. In this work, we use electrical detection, in combination with microwave transmission, to investigate both resonant and nonresonant magnon-photon coupling in a microwave cavity at room temperature. Spin pumping in a dynamically coupled magnon-photon system is found to be distinctly different from previous experiments. Characteristic coupling features such as modes anticrossing, linewidth evolution, peculiar line shape, and resonance broadening are systematically measured and consistently analyzed by a theoretical model set on the foundation of classical electrodynamic coupling. Our experimental and theoretical approach paves the way for pursuing microwave coherent manipulation of pure spin current via the combination of spin pumping and magnon-photon coupling. Co-authored with M. Harder, C.-M. Hu from University of Manitoba, Y. P. Chen, J. Q. Xiao from University of Delaware, and X. Fan from Univeristy of Denver.

  8. Tether System for Exchanging Payloads Between the International Space Station and the Lunar Surface

    NASA Technical Reports Server (NTRS)

    Hoyt, Robert P.

    1998-01-01

    Systems composed of several rotating and/or hanging tethers may provide a means of exchanging supplies between low Earth orbit facilities and lunar bases without requiring the use of propellant. This work develops methods for designing a tether system capable of repeatedly exchanging payloads between a LEO facility such as the International Space Station or a Space Business Park and a base on the lunar surface. In this system, a hanging tether extended upwards from the LEO facility, places a payload into a slightly elliptical orbit, where it is caught by a rotating tether in a higher elliptical orbit. This rotating tether then tosses the payload to the moon. At the moon, a long rotating "Lunavator" tether catches the payload and deposits it on the surface of the moon. By transporting an equal mass of lunar materials such as oxygen back down to the LEO facility through the tether transport system, the momentum and energy of the system is conserved, allowing frequent traffic between LEO and the lunar surface with minimal propellant requirements.

  9. A three-mass tethered system for micro-g/variable-g applications

    NASA Technical Reports Server (NTRS)

    Lorenzini, E. C.

    1986-01-01

    This paper describes a Space-Station attached tethered system for micro-g/variable-g applications. The system consists of three platforms: the Space Station, an end mass anchored at the end of a 10 km long kevlar tether and a micro-g/variable-g laboratory with the capability of crawling along the tether. Control strategies are devised for performing both the deployment and the station-keeping maneuvers of the system. Effective algorithms are identified for damping out the major vibrational modes.

  10. A Magnetic Bumper-Tether System Using ZFC Y123

    NASA Technical Reports Server (NTRS)

    Weinstein, Roy; Parks, Drew; Sawh, Ravi-Persad; Obot, Victor; Liu, Jianxiong; Arndt, G. D.

    1996-01-01

    We consider the use of magnetic forces in a bumper system, to soften docking procedures. We investigate a system which exhibits no magnetic field except during the docking process, which, if desired, can automatically tether two craft together, and which provides lateral stability during docking. A system composed of zero field cooled Y(1.7)Ba2Cu3O(7-delta) (Y123) tiles and electromagnets is proposed. The Y123 high temperature superconductor (HTS) is mounted on one craft, and the electromagnet on the other. Results of small prototype laboratory experiments are reported. The electromagnet has, for convenience, been replaced by a permanent SmCo ferromagnet in these measurements. When the two craft approach, a mirror image of the ferromagnet is induced in the Y123, and a repulsive bumper force, F(sub B), results. F(sub B) is velocity dependent, and increases with v. For presently available HTS materials, bumper pressure of approx. 3.7 N/cm(exp 2) is achieved using SmCo. This extrapolates to approx. 18 N/cm(exp 2) for an electromagnet, or a force of up to 20 tons for a 1 m(exp 2) system. After reaching a minimum distance of approach, the two colliding craft begin to separate. However, the consequent change of SmCo magnetic field at the Y123 results in a reversal of current in the Y123 so that the Y123 is attractive to the SmCo. The attractive (tether) force, F(sub T), is a function of R = B(sub Fe)/B(sub t, max), where B(sub Fe) is the field at the surface of the ferromagnet, and B(sub t, max) is the maximum trapped field of the Y123, i.e., the trapped field in the so-called critical state. For R greater than or equal to 2, F(sub T) saturates at a value comparable to F(sub B). For a range of initial approach velocities the two craft are tethered following the bumper sequence. Most of the kinetic energy of the collision is first converted to magnetic field energy in the Y123, and then into heat via the creep mechanism. About 15% of the work done against magnetic forces

  11. Electrodynamic Tether Operations and Control

    NASA Technical Reports Server (NTRS)

    Glaese, John R.

    2001-01-01

    This Final Report is organized by tasks from the statement of work (SOW). A brief statement of each task with its task description followed by a discussion of the work performed is presented. The period of performance for this contract phase was from July 21, 2000 to March 19, 2001.

  12. Tethers and debris mitigation

    NASA Astrophysics Data System (ADS)

    van der Heide, Erik Jan; Kruijff, Michiel

    2001-03-01

    In recent years, the use of tethers has been proposed for reduction of space debris either through momentum transfer or use of electrodynamic effects. Tethers have been shown to at least theoretically allow for quick, elegant and cost-effective deorbit of defunct satellites or spent stages. On the other hand, the large risk that tethers themselves may pose to other satellites in orbit has been recognized as well. The large collision area of tethers, combined with operational hazards and meteoroid risk may result in a large orbital exposure. For example, in 1997, the ESA/Dutch 35-km tether deployment of YES from TEAMSAT was inhibited after an analysis of the collision risk for the case the tether operation would fail. The question rises how these two points of view compare to eachother. This paper intends to highlight a representative selection of the proposed tether applications while taking into account the added risks caused by the tethers themselves. Typical applications from recent literature will be briefly described, such as an Ariane 502 spent stage re-entry from GTO and the concept of deboost of defunct satellites by interaction of a conductive tether with the Earth magnetic field. Mass savings of the tethered sytems versus conventional equivalents will be evaluated. Based on a crude risk analysis, involving elements such as mission complexity, dynamic stability, meteoroid risk and orbital life time, a general outline of limiting factors can be given for the various applications. Special attention is reserved for implementation of mechanisms that help reduce this tether risk, such as the DUtether (Tether Degradable by Ultraviolet), utilization of airdrag and solar pressure, the effect of residual current in bare tethers, tether retrieval etc. It is proposed how a net tether-induced mitigation can be compared to that of conventional alternatives, i.e. deboost by rocket engine or a completely passive approach. This comparison is put in the perspective of an

  13. Attitude dynamics of the Tether Elevator/Crawler System for micro-gravity applications

    NASA Technical Reports Server (NTRS)

    Vetrella, S.; Moccia, A.; Lorenzini, E. C.; Cosmo, M.

    1989-01-01

    The Tether Elevator/Crawler System (TECS) consists of two end platforms tethered to opposite sides of the Space Station. A variable gravity laboratory is located on board an elevator which can crawl along the upper tether. This paper analyzes the elevator's attitude dynamics in order to evaluate its effect on microgravity applications. To this end, a simulation model is described and numerical results are given for a steady state case. It is shown that the elevator attitude dynamics, without attitude control, contributes additional spectral lines to the acceleration noise.

  14. Dynamic Analysis of Capture Devices for Momentum Exchange with Tethers

    NASA Technical Reports Server (NTRS)

    Canfield, Stephen

    2002-01-01

    One of the significant challenges in developing a momentum exchange / electrodynamic reboost tether system is in the analysis and design of the capture device and its effects on the overall dynamics of the system. The goal of this work is to develop appropriate tether momentum exchange models that can simulate and evaluate the requirements of such a system, and be used to create specifications on the design of a capture device. This report briefly describes dynamic model development, simulation of the momentum exchange process, evaluation of dynamic effects of errors in the momentum exchange process, and the development of guidelines in selecting dynamic properties in the design of a capture device.

  15. Anti-sway control of tethered satellite systems using attitude control of the main satellite

    NASA Astrophysics Data System (ADS)

    Yousefian, Peyman; Salarieh, Hassan

    2015-06-01

    In this study a new method is introduced to suppress libration of a tethered satellite system (TSS). It benefits from coupling between satellites and tether libration dynamics. The control concept uses the main satellite attitude maneuvers to suppress librational motion of the tether, and the main satellite's actuators for attitude control are used as the only actuation in the system. The study considers planar motion of a two body TSS system in a circular orbit and it is assumed that the tether's motion will not change it. Governing dynamic equations of motion are derived using the extended Lagrange method. Controllability of the system around the equilibrium state is studied and a linear LQG controller is designed to regulate libration of the system. Tether tension and satellite attitude are assumed as only measurable outputs of the system. The Extended Kalman Filter (EKF) is used to estimate states of the system to be used as feedback to the controller. The designed controller and observer are implemented to the nonlinear plant and simulations demonstrate that the controller lead to reduction of the tether libration propoerly. By the way, because the controller is linear, it is applicable only at low amplitudes in the vicinity of equilibrium point. To reach global stability, a nonlinear controller is demanded.

  16. The use of the Tethered Satellite System to perform low density aerothermodynamics studies

    NASA Technical Reports Server (NTRS)

    Carlomagno, Giovanni M.; De Luca, Luigi; Siemers, Paul M.; Wood, George M., Jr.

    1988-01-01

    The Tethered Satellite System (TSS) is a cooperative space system development activity being carried out by USA and Italy. Within TSS, the Shuttle Tethered Aerothermodynamic Research Facility (STARFAC) concept has the potential to provide access to vast portions of the upper atmosphere for the purpose of atmospheric and aerothermodynamic research. The implementation of this capability will push Tether System (TS) state of the art to its limits; the primary problems being tether/satellite drag, heating, tension control, deployment/retrieval control. In this paper parametric studies are accomplished to assess some of these problems and to delineate the tradeoffs available to missions design to meet the engineering constraints. The utilization of aerodynamic rather than spherical shapes - (TSS) - as well as elementary satellite thrusting and lift are included in the present study.

  17. The use of the tethered satellite system to perform low density aerothermodynamics studies

    NASA Technical Reports Server (NTRS)

    Carlomagno, Giovanni M.; Deluca, Luigi; Siemers, Paul M.; Wood, George M., Jr.

    1988-01-01

    The Tethered Satellite System (TSS) is a cooperative space system development activity of the U.S.A. and Italy. It is comprised of the Tether Satellite (TS) and the deployer. Within TSS, the Shuttle Tethered Aerothermodynamic Research Facility (STARFAC) concept has the potential to provide access to vast portions of the upper atmosphere for atmospheric and aerothermodynamic research. The feasibility and capability of the TSS to operate as a continuous open wind tunnel and to perform low density aerothermodynamic studies are investigated. This is accomplished through a modified version of the TS simulation program (SKYHOOK). The results indicate that STARFAC concept is both feasible and practical. The TS can go below 100 km but, if thrust is used, large velocity variation (delta V) maneuvers and an attitude control are required; if a satellite lift is considered, large tether tension is produced and an attitude control is required.

  18. Ground-Based Experiment of Current Collection to Bare Tether in High-Speed and High-Density Plasma Generated by Hall Thrusters

    SciTech Connect

    Kohori, Tatsuya; Ikeda, Tomoyuki; Shimizu, Masaharu; Takagi, Hiroki; Yamada, Minetsugu; Tahara, Hirokazu

    2008-12-31

    Bare-tether systems are one of the greatest-efficiency electrodynamic tethered systems. The system with an uninsulated portion of the metallic tether itself to collect electrons from the space plasma is operated as a thruster or a power generator on a satellite. Ground-based experiments were carried out to understand phenomena of electron collection by a bare tether in space. Metallic tether samples were exposed to a simulating Low-Earth-Orbit plasma flow as varying tether sample diameter and length, and plasma velocity. A magnetic field was also applied. The normalized collection current increased with normalized tether sample potential. The tether sample diameter did not influence the normalized collection current characteristics although an increase in tether sample length decreased the normalized collection current in this experiment. The collection current characteristics were independent of plasma velocity under meso-thermal conditions. The existence of magnetic field raised the collection current because of the three-dimensional current collection effect at the edge of a tether sample under the magnetic field. Although the existence of magnetic field may raise the collection current, the effect will be small with a long tether. Accordingly, the dependence of tether diameter and length, plasma velocity and magnetic field on collection current characteristics of a bare tether in space might be small. The collection current may not exceed the OML current.

  19. Tethered gravity laboratories study

    NASA Technical Reports Server (NTRS)

    Lucchetti, F.

    1989-01-01

    The use is studied of tether systems to improve the lowest possible steady gravity level on the Space Station. Particular emphasis is placed by the microgravity community on the achievement of high quality microgravity conditions. The tether capability is explored for active control of the center of gravity and the analysis of possible tethered configurations.

  20. Multiple wind turbine tethered airfoil wind energy conversion system

    SciTech Connect

    Biscomb, L.I.

    1981-08-25

    A plurality of wind turbines are supported aloft on the same tethered airfoil which is provided with devices for orienting the wind turbines into the wind. Various ways and devices are described for converting the wind energy into electrical power and for connecting and providing the plural outputs to the same electrical power grid. The principles are applicable whether there are a small number of relatively large wind turbines, a large number of relatively small wind turbines or some of each.

  1. Advanced propulsion for LEO-Moon transport. 2: Tether configurations in the LEO-Moon system

    NASA Technical Reports Server (NTRS)

    Arnold, J. R.; Thompson, W. B.

    1992-01-01

    This brief work discusses a possible application of a tether as a dynamical element in a low Earth orbit (LEO)-Moon transport system, and is a part of the Cal Space study of that transport system. To be specific, that study concentrated on the downward transport of O2 from the Moon to LEO, where it is stored for use as a rocket propellant, thus reducing Earth liftoff mass requirements by a factor of about 8. Moreover, in order to display clearly the role of advanced technology, only one novel technology was introduced at a single node in the transport system, the rest being 'conventional' rocket transport. Tethers were found useful in several different roles: hanging from platforms in lunar orbits, as supports for elevators, spinning in LEO, or spinning in a tether transport orbit, an elliptical orbit with perigee at approximately 600 km. This last use is considered here. Presented are the usefulness of the tether, nature of the tether system, the apparatus needed to support, deploy, and control it, and a discussion of needed developments.

  2. Tether electrical characteristics design report

    SciTech Connect

    Lucas, J.H.

    1989-03-24

    The design of a tether system for use in electric and magnetic fields requires an analysis of the equivalent electrical circuit of the baboon and tether. The response of this equivalent circuit to an electric or magnetic field is dependent on the connection of the tether system to the baboon. The tether will be designed so that the currents induced in the tethered baboon are approximately the same as those induce in an untethered baboon. 6 figs., 3 tabs.

  3. Developing Capture Mechanisms and High-Fidelity Dynamic Models for the MXER Tether System

    NASA Technical Reports Server (NTRS)

    Canfield, Steven L.

    2007-01-01

    A team consisting of collaborators from Tennessee Technological University (TTU), Marshall Space Flight Center, BD Systems, and the University of Delaware (herein called the TTU team) conducted specific research and development activities in MXER tether systems during the base period of May 15, 2004 through September 30, 2006 under contract number NNM04AB13C. The team addressed two primary topics related to the MXER tether system: 1) Development of validated high-fidelity dynamic models of an elastic rotating tether and 2) development of feasible mechanisms to enable reliable rendezvous and capture. This contractor report will describe in detail the activities that were performed during the base period of this cycle-2 MXER tether activity and will summarize the results of this funded activity. The primary deliverables of this project were the quad trap, a robust capture mechanism proposed, developed, tested, and demonstrated with a high degree of feasibility and the detailed development of a validated high-fidelity elastic tether dynamic model provided through multiple formulations.

  4. Dynamics Simulation Model for Space Tethers

    NASA Technical Reports Server (NTRS)

    Levin, E. M.; Pearson, J.; Oldson, J. C.

    2006-01-01

    This document describes the development of an accurate model for the dynamics of the Momentum Exchange Electrodynamic Reboost (MXER) system. The MXER is a rotating tether about 100-km long in elliptical Earth orbit designed to catch payloads in low Earth orbit and throw them to geosynchronous orbit or to Earth escape. To ensure successful rendezvous between the MXER tip catcher and a payload, a high-fidelity model of the system dynamics is required. The model developed here quantifies the major environmental perturbations, and can predict the MXER tip position to within meters over one orbit.

  5. High fidelity microelectromechanical system electrodynamic micro-speaker characterization

    NASA Astrophysics Data System (ADS)

    Sturtzer, E.; Shahosseini, I.; Pillonnet, G.; Lefeuvre, E.; Lemarquand, G.

    2013-06-01

    This paper deals with the heterogeneous characterization of a microelectromechanical system (MEMS) electrodynamic micro-speaker. This MEMS micro-speaker consists of an optimized silicon structure based on a very light but very stiff membrane. The mobile part is suspended using soft suspension beams, also made of silicon, which enable large out-of-plane displacement. The electromagnetic motor is composed of a micro-assembly permanent ring magnet and of a deposit mobile planar coil fixed on the top of the silicon membrane. Previous publications have presented the MEMS as theoretically able to produce high fidelity and high efficiency over a wide bandwidth. The present study intends to validate the electrical, the mechanical, and the acoustic performance improvements. The characterization of the microfabricated micro-speaker showed that the electric impedance is flat over the entire audio bandwidth. Some results validates the performance improvements in terms of audio quality as compared to state of the art of the MEMS micro-speakers, such as the high out-of-plane membrane displacement over ±400 μm, the 80 dBSPL sound pressure level at 10 cm, the 2% maximal distortion level, and the useful bandwidth from 335 Hz to cutoff frequency.

  6. Quantum electrodynamics of resonance energy transfer in nanowire systems

    NASA Astrophysics Data System (ADS)

    Weeraddana, Dilusha; Premaratne, Malin; Andrews, David L.

    2016-02-01

    Nonradiative resonance energy transfer (RET) provides the ability to transfer excitation energy between contiguous nanowires (NWs) with high efficiency under certain conditions. Nevertheless, the well-established Förster formalism commonly used to represent RET was developed for energy transfer primarily between molecular blocks (i.e., from one molecule, or part of a molecule, to another). Although deviations from Förster theory for functional blocks such as NWs have been studied previously, the role of the relative distance, the orientation of transition dipole moment pairs, and the passively interacting matter on electronic energy transfer are to a large extent unknown. Thus, a comprehensive theory that models RET in NWs is required. In this context, analytical insights to give a deeper and more intuitive understanding of the distance and orientation dependence of RET in NWs is presented within the framework of quantum electrodynamics. Additionally, the influence of an included intermediary on the rate of excitation energy transfer is illustrated, embracing indirect energy transfer rate and quantum interference. The results deliver equations that afford new intuitions into the behavior of virtual photons. In particular, results indicate that RET efficiency in a NW system can be explicitly expedited or inhibited by a neighboring mediator, depending on the relative spacing and orientation of NWs.

  7. Getaway Tether Experiment (GATE): A free flying tether experiment

    NASA Technical Reports Server (NTRS)

    Greene, M.

    1986-01-01

    Orbital reboost and power generation using electrodynamic tethers has been suggested as a means of increasing the operational flexibility and orbital lifetime of satellites. Excess energy generated by solar arrays can be stored as orbital energy and later extracted form the orbit during peak power demands. The Getaway Tether Experiment (GATE) will demonstrate this practical tether application and will measure the dynamic circuit impedance. The micrometeoroid hazard to tension members will be studied as will radio frequency propagation. The radar cross section of long wires will be calculated considering the effects of resistance.

  8. The optimal control for the tethered system formed by an asteroid and a solar sail

    NASA Astrophysics Data System (ADS)

    Gao, Youtao; Wu, Jingyun

    2016-02-01

    This paper focuses on a method of changing the orbit of an asteroid by attaching a solar sail to the asteroid. First, the dynamic model of the tethered system is derived. Legendre pseudospectral method is then used to discretize the system, and the sequence of two quadratic programming is utilized to obtain the optimal control law. Simulation results show that the tethered solar sail can efficiently change the asteroid's orbit. Moreover, the problem of the tether twining around the asteroid caused by the relative orbit motion between the solar sail and the asteroid can be avoided. Finally, the effectiveness of altering an asteroid's orbit by different solar sails is analyzed. Simulation results show that when the area of the solar sail is 106 m2, the asteroid can be deflected at 1.227 × 108 m by the solar sail after about 20 years, which is better than the effect of a gravitational tractor.

  9. Activation of Immobilized Lipase in Non-Aqueous Systems by Hydrophobic Poly-DL-Tryptophan Tethers

    PubMed Central

    Schilke, Karl F.; Kelly, Christine

    2014-01-01

    Many industrially important reactions use immobilized enzymes in non-aqueous, organic systems, particularly for the production of chiral compounds such as pharmaceutical precursors. The addition of a spacer molecule (“tether”) between a supporting surface and enzyme often substantially improves the activity and stability of enzymes in aqueous solution. Most “long” linkers (e.g. polyethylene oxide derivatives) are relatively hydrophilic, improving the solubility of the linker-enzyme conjugate in polar environments, but this provides little benefit in non-polar environments such as organic solvents. We present a novel method for the covalent immobilization of enzymes on solid surfaces using a long, hydrophobic polytryptophan tether. Candida antarctica lipase B (CALB) was covalently immobilized on non-porous, functionalized 1-μm silica microspheres, with and without an intervening hydrophobic poly-DL-tryptophan tether (n ≈ 78). The polytryptophan-tethered enzyme exhibited 35 times greater esterification of n-propanol with lauric acid in the organic phase and five times the hydrolytic activity against pnitrophenol palmitate, compared to the activity of the same enzyme immobilized without tethers. In addition, the hydrophobic tethers caused the silica microspheres to disperse more readily in the organic phase, while the surface-immobilized control treatment was less lipophilic and quickly settled out of the organic phase when the suspensions were not vigorously mixed. PMID:18393315

  10. A ``Spring-mass'' model of tethered satellite systems: properties of planar periodic motions

    NASA Astrophysics Data System (ADS)

    Sidorenko, Vladislav V.; Celletti, Alessandra

    2010-06-01

    This paper is devoted to the dynamics in a central gravity field of two point masses connected by a massless tether (the so called “spring-mass” model of tethered satellite systems). Only the motions with straight strained tether are studied, while the case of “slack” tether is not considered. It is assumed that the distance between the point masses is substantially smaller than the distance between the system’s center of mass and the field center. This assumption allows us to treat the motion of the center of mass as an unperturbed Keplerian one, so to focus our study on attitude dynamics. A particular attention is given to the family of planar periodic motions in which the center of mass moves on an elliptic orbit, and the point masses never leave the orbital plane. If the eccentricity tends to zero, the corresponding family admits as a limit case the relative equilibrium in which the tether is elongated along the line joining the center of mass with the field center. We study the bifurcations and the stability of these planar periodic motions with respect to in-plane and out-of-plane perturbations. Our results show that the stable motions take place if the eccentricity of the orbit is sufficiently small.

  11. Hyperbolic Injection Issues for MXER Tethers

    NASA Technical Reports Server (NTRS)

    Sorensen, Kirk

    2003-01-01

    Momentum-exchange/electrodynamic reboost (MXER) tether technology is currently being pursued to dramatically lower the launch mass and cost of interplanetary scientific spacecraft. A spacecraft boosted from LEO to a high-energy orbit by a MXER tether has most of the orbital energy it needs to escape the Earth's gravity well. However, the final targeting of the spacecraft to its eventual trajectory, and some of the unique issues brought on by the tether boost, are the subjects of this paper.

  12. Posture evaluations of tethering and loose-housing systems in dairy farms.

    PubMed

    Hwang, Jaejin; Kong, Yong-Ku; Jung, Myung-Chul

    2010-12-01

    The purpose of this study was to evaluate the most common simultaneous and individual segment postures in terms of body and finger posture classifications. Observations were made at three dairy farms. One employed a tethering system and the other two used loose-housing systems. The evaluations of the tethering system were performed through six processes that were subdivided into 11 operations, whereas only one process of 'milking' was investigated in loose-housing systems. Generally, farmers who worked in both systems bent and/or twisted their upper-body segments and continuously used a power grasp to wrap an object with all five fingers. Posture analyses of the tethering system revealed that 'moving corn' seemed less stressful, whereas 'cleaning udders,' 'attaching the machine,' 'washing the machine,' and 'sweeping the floor' were more stressful than other operations. Postural workloads on the trunk and head were greater in the tethering system than in the loose-housing systems due to differences in implements, the working height, and the working distance. PMID:20427034

  13. Low density aerothermodynamics studies performed by means of the tethered satellite system

    NASA Technical Reports Server (NTRS)

    Carlomagno, Giovanni M.; De Luca, Luigi; Siemers, Paul M.; Wood, George M., Jr.

    1986-01-01

    Low density gas flow modeling and current ground wind-tunnel technologies are not presently able to produce fully reliable data concerning low density flow regimes. In order to answer some of these issues, the Shuttle Continuous Open Wind Tunnel (SCOWT) program has been proposed, which makes use of the tethered satellite system (TSS). SCOWT's objective is to investigate the energy and momentum transfer between the tethered satellite and its environmental medium within the range of the thermofluid-dynamic conditions experienced by TSS during its atmospheric flights. The feasibility and capability of SCOWT to perform low density aerothermodynamics studies are investigated. Some of the results, obtained by means of a tether simulation program, and the instrumentation and TSS design main requirements to meet SCOWT objectives are described.

  14. Tether applications

    NASA Technical Reports Server (NTRS)

    1986-01-01

    For a range of tether lengths, end masses, and orbits, tether deployment concepts were defined and/or analyzed from the Orbiter for steady state/dynamic and up/down deployments and from circular/elliptical orbits. Orbits were defined and/or analyzed for end mass releasing concepts with steady state and dynamic releases taking into account tether and end mass motion before and after release. For a range of tether lengths, end masses, and orbits, tether retrieving or disposing concepts were defined and/or analyzed for both reusable and disposable tethers. Tether programs were installed or updated on the MSFC VAX 11/780 computer.

  15. In-Space Transportation with Tethers

    NASA Technical Reports Server (NTRS)

    Lorenzini, Enrico; Estes, Robert D.; Cosmo, Mario L.

    1998-01-01

    The annual report covers the research conducted on the following topics related to the use of spaceborne tethers for in-space transportation: ProSEDS tether modeling (current collection analyses, influence of a varying tether temperature); proSEDS mission analysis and system dynamics (tether thermal model, thermo-electro-dynamics integrated simulations); proSEDS-tether development and testing (tether requirements, deployment test plan, tether properties testing, deployment tests); and tethers for reboosting the space-based laser (mission analysis, tether system preliminary design, evaluation of attitude constraints).

  16. STS-46 Tethered Satellite System 1 (TSS-1) satellite deployment from OV-104

    NASA Technical Reports Server (NTRS)

    1992-01-01

    STS-46 Tethered Satellite System 1 (TSS-1) satellite is reeled out via its thin Kevlar tether into the blackness of space during deployment operations from the payload bay (PLB) of Atlantis, Orbiter Vehicle (OV) 104. At the bottom of the frame is the satellite upper boom including (bottom to top) the 12-m deployment boom, tip can, the docking ring, and concentric ring damper. The Langmuir probe and the dipole-field antenna are stowed at either side of the TSS-1 satellite.

  17. Tethered satellite system dynamics and control review panel and related activities, phase 3

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Two major tests of the Tethered Satellite System (TSS) engineering and flight units were conducted to demonstrate the functionality of the hardware and software. Deficiencies in the hardware/software integration tests (HSIT) led to a recommendation for more testing to be performed. Selected problem areas of tether dynamics were analyzed, including verification of the severity of skip rope oscillations, verification or comparison runs to explore dynamic phenomena observed in other simulations, and data generation runs to explore the performance of the time domain and frequency domain skip rope observers.

  18. Cavity quantum electrodynamics of nanoscale two-level systems

    NASA Astrophysics Data System (ADS)

    Sarabi, Bahman

    In this dissertation, I introduce a novel method for measuring individual nanoscale two-level systems (TLSs) in amorphous solids based on strong direct coupling between a TLS and a cavity. I describe power- and temperature-dependent analysis of individual TLSs using a theoretical model based on cavity quantum electrodynamics (CQED). This method allows for measuring individual TLSs in different insulators and over a wide range of film thicknesses. For a silicon nitride film at 25 mK and a lumped-element cavity resonance at 6.9 GHz, I find TLSs with coherence times on the order of microseconds which can potentially be used as coherent resources. Furthermore, I introduce a device which enables spectroscopy of TLSs in insulating films by DC-tuning the TLSs. I present measurement results on 60 TLSs accompanied by theoretical analysis and extraction of distribution statistics of the TLS parameters. I find evidence for at least two TLS dipole sizes. I also investigate the role of RF-induced DC bias voltage on the growth of titanium nitride films on silicon (100) substrates deposited by DC magnetron reactive sputtering. I present hybrid designs of TiN coplanar resonators which were fabricated with an aluminum transmission line to avoid impedance mismatches due to large kinetic inductance of TiN films. I observe remarkably large kinetic inductance at certain substrate DC bias voltages. Finally, I describe several trilayer resonators designed to measure TLS ensembles within atomic layer deposition (ALD) grown aluminum oxide. Each resonator is unique in trilayer capacitor perimeter and hence the alumina air-exposed cross section. I compare the measured loss tangents of the resonators and investigate the effect of the capacitor perimeter on TLS defect density at different temperatures.

  19. Orbital Winch for High-Strength, Space-Survivable Tethers

    NASA Technical Reports Server (NTRS)

    Hoyt, Robert; Barnes, Ian; Slostad, Jeffrey; Frank, Scott

    2010-01-01

    An Orbital Winch mechanism enables high-load, multi-line tethers to be deployed and retracted without rotating the spool on which the tether is wound. To minimize damage to the tether and the wound package during retraction or deployment under load, it can incorporate a Tension Management Module that reduces the infeed tension by a factor of 15 through the use of a powered capstan with guide rollers. This design eliminates the need for rotating high-voltage electrical connections in tether systems that use propellantless electro-dynamic propulsion. It can also eliminate the need for rotating optical connections in applications where the tether contains optical fibers. This winch design was developed to deploy a 15-km-long, 15-kg high-strength Hoytether structure incorporating conductive wires as part of the MXER-1 demonstration mission concept. Two slewing rings that orbit around the tether spool, combined with translation of one of the slewing rings back and forth along the spool axis to traverse the wind point, enables the winch to wind the tether. Variations of the traverse motion of the slewing ring can accomplish level winds and conical pirn winds. By removing the non-traversing slewing ring, and adding an actuated guide arm, the winch can manage rapid, low-drag deployment of a tether off the end of a pirn-wound spool, followed by controlled retraction and rewinding, in a manner very similar to a spin-casting reel. The winch requires at least two motor driver controller units to coordinate the action of two stepper motors to accomplish tether deployment or retraction.

  20. Development of Polymer Coatings for the ProSEDS Tether

    NASA Technical Reports Server (NTRS)

    Vaughn, Jason A.; Kamenetsky, Rachel R.; Finckenor, Miria; Wright, Ken

    2000-01-01

    The ProSEDS mission is designed to provide an on-orbit demonstration of the electrodynamic propulsion capabilities of tethers in space. The ProSEDS experiment will be a secondary payload on a Delta 11 unmanned, expendable booster. A 5 km conductive tether is attached to the deployer baseplate on the Delta 11 second stage and collects current from the low Earth orbit (LEO) plasma to facilitate de-orbit of the Delta II second stage. The conductive tether is attached to a 10-15 km non-conductive tether, which in turn is attached to an endmass. A bare metal tether would have the best conductivity but thermal concerns preclude this design. A conductive polymer developed by Triton Systems has been optimized for optimum conductivity and thermo-optical properties. The current design for the ProSEDS conductive tether is seven individually coated strands of 28 AWG aluminum wire, coated with 12.7 micrometers (0.5 mil) atomic oxygen-resistant conductive polymer composed of a mixture of COR and PANi, wrapped around a braided Kevlar 29 core. Extensive testing has been performed at the Marshall Space Flight Center to qualify this material for flight on ProSEDS. Atomic oxygen exposure has been performed, with solar absorptance and infrared emittance measured before and after exposure. Plasma chamber tests have been completed, as well as tether deployment tests. Also developed for the ProSEDS mission was the insulating polymer TOR-BP. Approximately 200 meters of the conductive tether closest to the Delta II second stage is insulated to prevent any electron reconnection to the tether from the plasma contactor. The insulating material is TOR-BP with a dielectric strength of TBD.

  1. Tether de-orbiting of satellites at end of mission

    NASA Astrophysics Data System (ADS)

    Sanmartin, Juan R.; Sánchez-Torres, Antonio

    2012-07-01

    The accumulation of space debris around the Earth has become critical for Space security. The BETs project, financed by the European Commission through its FP7-Space program, is focusing on preventing generation of new debris by de-orbiting satellites at end of mission. The de-orbiting system considered, involving an electrodynamic bare tape-tether, uses no propellant and no power supply, while generating power for on-board use during de-orbiting. As an example, preliminary results are here presented on a specific orbit/satellite case: 1300 km altitude and 65 degrees inclination, and 500 kg mass. Design tether dimensions are 8 km length, 1.5 cm width, and 0.05 mm thickness; subsystem masses are limited to twice tether mass. Simple calculations, using orbit-averaging, solar mid-cycle phase, and ionospheric and geomagnetic field models, yield 2.6 months time for de-orbiting down to 200 km, with a probability of about 1 percent of debris cutting the tape. References: Sanmartin, J.R., Lorenzini, E.C., and Martinez-Sanchez, M., Electrodynamic Tether Applications and Constraints, J. Space. Rockets 47, 442-456, 2010. Sanmartin, J.R. et al., A universal system to de-orbit satellites at end of life, Journal of Space Technology and Science, to appear.

  2. Changes in Polymeric Tether Properties Due to Atomic Oxygen

    NASA Technical Reports Server (NTRS)

    Finckenor, Miria M.; Vaughn, Jason A.; Watts, Edward W.

    2003-01-01

    The Propulsive Small Expendable Deployer System (ProSEDS) mission is designed to provide an on-orbit demonstration of the electrodynamic propulsion capabilities of tethers in space. The ProSEDS experiment will be a secondary payload on a Delta II unmanned expendable booster. A 5-km conductive tether is attached to the Delta II second stage and collects current fiom the low Earth orbit (LEO) plasma to facilitate de-orbit of the spent stage. The conductive tether is attached to a 10-km non-conductive tether, which is then attached to an endmass containing several scientific instruments. Atomic oxygen (AO) erodes most organic materials. As the orbit of the Delta II second stage decas, the AO flux (atoms/sq cm sec) increases. A nominal AO fluence of 1 x l0(exp 21) atoms/sq cm was agreed upon by the investigators as an adequate level for evaluating the performance of the tether materials. A test series was performed to determine the effect of atomic oxygen (AO) on the mechanical integrity and possible strength loss of ProSEDS tether materials. The tether materials in this study were Dyneema, an ultra-high molecular weight polyethylene material used as the non-conducting portion of the ProSEDS tether, and the Kevlar core strength fiber used in the conductive tether. Samples of Dyneema and Kevlar were exposed to various levels of atomic oxygen up to 1.07 x 10(exp 21) atoms/sq cm in the Marshall Space Flight Center Atomic Oxygen Beam Facility (AOBF). Changes in mass were noted after AO exposure. The tethers were then tensile-tested until failure. AO affected both the Dyneema and Kevlar tether material strength. Dyneema exposed to 1.07 x 10(exp 21) atoms/sq cm of atomic oxygen failed due to normal handling when removed fiom the AOBF and was not tensile-tested. Another test series was performed to determine the effect of AO on the electrical properties of the ProSEDS conductive tether. The conductive tether consists of seven individually coated strands of 28 AWG 1350

  3. Astronaut Maurizio Cheli, mission specialist, works with the Tether Optical Phenomenon System (TOPS)

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Astronaut Maurizio Cheli, mission specialist, works with the Tether Optical Phenomenon System (TOPS) on the flight deck of the Earth-orbiting Space Shuttle Columbia. Cheli, representing the European Space Agency (ESA), joined four other astronauts and an international payload specialists for 16 days of scientific research in Earth-orbit.

  4. Technical and economical assessment on tethered wind-energy systems (TWES)

    SciTech Connect

    Furuya, O.; Maekawa, S.

    1982-06-01

    The objective of the work reported was to establish the potential of tethered wind energy systems for energy conversion in the upper atmosphere. Of the concepts investigated, the Vertical Takeoff and Landing (VTOL) lift generation concept had the highest potential as compared to balloon, wind and hybrid concepts.

  5. Evaluation of surgery for the tethered cord syndrome using a new grading system.

    PubMed

    Kirollos, R W; Van Hille, P T

    1996-06-01

    A new grading system is presented to assess the degree of untethering achieved at surgery for the 'tethered cord syndrome' based on intraoperative observation at the end of the procedure. Various pathophysiological mechanisms responsible for the 'tethered cord syndrome', as well as possible factors causing retethering were considered in developing this grading system. In Grade I the cord is considered to be fully untethered and the factors potentially responsible for retethering are eliminated, in Grade II partial untethering is performed and in Grade III untethering is unsuccessful. This grading system was used to assess the results of 22 consecutive operations performed to release a tethered cord between June 1991 and February 1995. The tethering factors encountered at surgery were: spinal lipoma in 14, diastematomyelia in five, a tight filum terminale in 10 and intradural adhesions in three instances. The grade of untethering was correlated with the type of pathology encountered, postoperative results, and whether previous surgery was performed or not. Previous surgery was found not to affect the rate of subsequent successful untethering. PMID:8799535

  6. Study of the triple-mass Tethered Satellite System under aerodynamic drag and J2 perturbations

    NASA Astrophysics Data System (ADS)

    Razzaghi, Pourya; Assadian, Nima

    2015-11-01

    The dynamics of multi-tethered satellite formations consisting of three masses are studied in this paper. The triple-mass triple-tethered satellite system is modeled under the low Earth orbit perturbations of drag and Earth's oblateness and its equilibrium conditions are derived. It is modeled as three equal end-masses connected by a uniform-mass straight tether. The lengths of tethers are supposed to be constant and in this manner the angles of the plane consisting the masses are taken as the state variables of the system. The governing equations of motion are derived using Lagrangian approach. The aerodynamic drag perturbation is expressed as an external non-conservative force and the Earth oblateness (J2 perturbation) is considered as a term of potential energy. The equilibrium conditions of this system are found and their stability is investigated through the linear stability theory. Then, the results are verified by using a nonlinear simulation for three types of equilibrium conditions.

  7. Study of Plasma Motor Generator (PMG) tether system for orbit reboost

    NASA Technical Reports Server (NTRS)

    1988-01-01

    A progress report is given on a system study by TRW begun in January 1987 of a 2 kW Plasma Motor Generator Tether to be used for orbit reboost. Following the completion of the initial phase in September 1987, additional tasks were agreed on and work on them begun in March 1988. These tasks fell into three categories: tests on the prototype tether fabricated during the first phase, simulations of the spacecraft and tether system after deployment using GTOSS, and a brief investigation of the impact and feasibility of increasing the system to 20 kW and hosting it on the Orbital Maneuvering Vehicle. The subcontractor, Energy Sciences Laboratory, was assigned the responsibility of performing the simulations and some mechanical tests on the prototype tether to supplement those done at TRW. A summary of the significant findings and issues from each task follows. Recommendations for future work constitutes the third section. A copy of the final briefing is in Appendix A, plus additional reports for each task and additional analysis.

  8. Tethered subsatellite study

    NASA Technical Reports Server (NTRS)

    Baker, W. P.; Dunkin, J. A.; Galaboff, Z. J.; Johnston, K. D.; Kissel, R. R.; Rheinfurth, M. H.; Siebel, M. P. L.

    1976-01-01

    The results are presented of studies performed relating to the feasibility of deploying a subsatellite from the shuttle by means of a tether. The dynamics, the control laws, the aerodynamics, the heating, and some communication considerations of the tethered subsatellite system are considered. Nothing was found that prohibits the use of a subsatellite joined to the shuttle by a long (100 km) tether. More detailed studies directed at specific applications are recommended.

  9. Control systems for membrane fusion in the ancestral eukaryote; evolution of tethering complexes and SM proteins

    PubMed Central

    Koumandou, V Lila; Dacks, Joel B; Coulson, Richard MR; Field, Mark C

    2007-01-01

    Background In membrane trafficking, the mechanisms ensuring vesicle fusion specificity remain to be fully elucidated. Early models proposed that specificity was encoded entirely by SNARE proteins; more recent models include contributions from Rab proteins, Syntaxin-binding (SM) proteins and tethering factors. Most information on membrane trafficking derives from an evolutionarily narrow sampling of model organisms. However, considering factors from a wider diversity of eukaryotes can provide both functional information on core systems and insight into the evolutionary history of the trafficking machinery. For example, the major Qa/syntaxin SNARE families are present in most eukaryotic genomes and likely each evolved via gene duplication from a single ancestral syntaxin before the existing eukaryotic groups diversified. This pattern is also likely for Rabs and various other components of the membrane trafficking machinery. Results We performed comparative genomic and phylogenetic analyses, when relevant, on the SM proteins and components of the tethering complexes, both thought to contribute to vesicle fusion specificity. Despite evidence suggestive of secondary losses amongst many lineages, the tethering complexes are well represented across the eukaryotes, suggesting an origin predating the radiation of eukaryotic lineages. Further, whilst we detect distant sequence relations between GARP, COG, exocyst and DSL1 components, these similarities most likely reflect convergent evolution of similar secondary structural elements. No similarity is found between the TRAPP and HOPS complexes and the other tethering factors. Overall, our data favour independent origins for the various tethering complexes. The taxa examined possess at least one homologue of each of the four SM protein families; since the four monophyletic families each encompass a wide diversity of eukaryotes, the SM protein families very likely evolved before the last common eukaryotic ancestor (LCEA

  10. Clustering of tethered satellite system simulation data by an adaptive neuro-fuzzy algorithm

    NASA Technical Reports Server (NTRS)

    Mitra, Sunanda; Pemmaraju, Surya

    1992-01-01

    Recent developments in neuro-fuzzy systems indicate that the concepts of adaptive pattern recognition, when used to identify appropriate control actions corresponding to clusters of patterns representing system states in dynamic nonlinear control systems, may result in innovative designs. A modular, unsupervised neural network architecture, in which fuzzy learning rules have been embedded is used for on-line identification of similar states. The architecture and control rules involved in Adaptive Fuzzy Leader Clustering (AFLC) allow this system to be incorporated in control systems for identification of system states corresponding to specific control actions. We have used this algorithm to cluster the simulation data of Tethered Satellite System (TSS) to estimate the range of delta voltages necessary to maintain the desired length rate of the tether. The AFLC algorithm is capable of on-line estimation of the appropriate control voltages from the corresponding length error and length rate error without a priori knowledge of their membership functions and familarity with the behavior of the Tethered Satellite System.

  11. Cluster filtering/control of bending/torsional vibrations of a tape tether using smart-film sensors/actuators

    NASA Astrophysics Data System (ADS)

    Kojima, Hirohisa; Kunugi, Kouta; Trivailo, Pavel M.

    2016-06-01

    Tape tethers show great promise for application in space debris removal because they possess a large collecting area, which is crucial for the collection of electrons from a plasma environment in space. Tape tethers are therefore preferred over string tethers in electrodynamic tethered systems (EDTS), which operate based on the Lorentz force derived from the interaction between the electric current on the tether and the Earth's magnetic field. Vibrations of the tether may disturb the attitude of the mother satellite and the subsatellite, and are difficult to damp in space because the damping would be minimal owing to the almost zero drag force in space. Due to their relatively large width, tape tethers experience torsional deformation and therefore cannot be treated as a string tether. If torsional deformation of tape tethers is not avoided, the advantage of tape tethers as the materials for EDT systems will be deteriorated. Point-type sensors and actuators are usually used to sense and control vibrations. However, it is difficult to apply such sensors and actuators to tape tethers because of the substantial length of the tether as well as the need for a deployment mechanism, such as a reel. In order to overcome the difficulties related to vibrations, the use of smart-film sensors and actuators for sensing and controlling vibrations of tape tethers is considered in this study. In a previous study, we presented an application of smart film for sensing vibrations of tape tethers, but the actuation of tape tethers using smart-film actuators has not yet been reported. In the present paper, we mathematically derive suitable configurations of smart-film attachment to a tape tether for cluster filtering and actuation of bending and torsional vibrations of the tape tether, and carried out cluster actuation experiments. The experimental results reveal that the bending and torsional vibrations of a tape tether can be reduced by cluster actuation control based on direct

  12. A Model for Dynamic Simulation and Analysis of Tether Momentum Exchange

    NASA Technical Reports Server (NTRS)

    Canfield, Stephen; Johnson, David; Sorensen, Kirk; Welzyn, Ken; Rodgers, Stephen L. (Technical Monitor)

    2002-01-01

    Momentum-exchange/electrodynamic reboost (MXER) tether systems may enable high-energy missions to the Moon, Mars, and beyond by serving as an 'upper stage in space'. Existing rockets that use an MXER tether station could double their capability to launch communications satellites and help improve US competitiveness. A MXER tether station would boost spacecraft from low Earth orbit to a high-energy orbit quickly, like a high-thrust rocket. Then, using the same principles that make an electric motor work, it would slowly rebuild its orbital momentum by pushing against the Earth's magnetic field-without using any propellant. One of the significant challenges in developing a momentum-exchange/electrodynamic reboost tether systems is in the analysis and design of the capture mechanism and its effects on the overall dynamics of the system. This paper will present a model for a momentum-exchange tether system that can simulate and evaluate the performance and requirements of such a system.

  13. Theory and Modeling in Support of Tether

    NASA Technical Reports Server (NTRS)

    Chang, C. L.; Bergeron, G.; Drobot, A. D.; Papadopoulos, K.; Riyopoulos, S.; Szuszczewicz, E.

    1999-01-01

    This final report summarizes the work performed by SAIC's Applied Physics Operation on the modeling and support of Tethered Satellite System missions (TSS-1 and TSS-1R). The SAIC team, known to be Theory and Modeling in Support of Tether (TMST) investigation, was one of the original twelve teams selected in July, 1985 for the first TSS mission. The accomplishments described in this report cover the period December 19, 1985 to September 31, 1999 and are the result of a continuous effort aimed at supporting the TSS missions in the following major areas. During the contract period, the SAIC's TMST investigation acted to: Participate in the planning and the execution on both of the TSS missions; Provide scientific understanding on the issues involved in the electrodynamic tether system operation prior to the TSS missions; Predict ionospheric conditions encountered during the re-flight mission (TSS-lR) based on realtime global ionosounde data; Perform post mission analyses to enhance our understanding on the TSS results. Specifically, we have 1) constructed and improved current collection models and enhanced our understanding on the current-voltage data; 2) investigated the effects of neutral gas in the current collection processes; 3) conducted laboratory experiments to study the discharge phenomena during and after tether-break; and 4) perform numerical simulations to understand data collected by plasma instruments SPES onboard the TSS satellite; Design and produce multi-media CD that highlights TSS mission achievements and convey the knowledge of the tether technology to the general public. Along with discussions of this work, a list of publications and presentations derived from the TMST investigation spanning the reporting period is compiled.

  14. Decentralized adaptive sliding mode control for beam synchronization of tethered InSAR system

    NASA Astrophysics Data System (ADS)

    Zhang, Jinxiu; Zhang, Zhigang; Wu, Baolin

    2016-10-01

    Beam synchronization problem of tethered interferometric synthetic aperture radar (InSAR) is addressed in this paper. Two antennas of the system are carried by separate satellites connected through a tether to obtain a preferable baseline. A Total Zero Doppler Steering (TZDS) is implemented to mother-satellite to cancel the residual Doppler. Subsequently attitude reference trajectories for the two satellites are generated to achieve the beam synchronization and TZDS. Thereafter, a decentralized adaptive sliding mode control law is proposed to track these reference trajectories in the presence of model uncertainties and external disturbances. Finally, the stability of closed-loop system is proved by the corollary of Barbalat's Lemma. Simulation results show the proposed control law is effective to achieve beam synchronization of the system.

  15. The motion of tethered tug-debris system with fuel residuals

    NASA Astrophysics Data System (ADS)

    Aslanov, Vladimir S.; Yudintsev, Vadim V.

    2015-10-01

    Active debris removal using a space tug with a tether is one of the promising techniques to decrease the population of large non-functional satellites and orbital stages in near Earth orbits. Properties of debris should be taken into account in the development of the space tugs. In this paper we consider the motion of a debris objects with fuel residuals that can affect the safety of the debris transportation process. The equations of the attitude motion of the tug-debris system in a central gravitational field are derived. Stationary solutions of the equations are found. The system of linearized equations are introduced that can be used for short term analysis. The numerical simulation results are provided that show good accuracy of the linearized equations. Proposed equations can be used to analyze the attitude motion of the tug-debris system and to determine the conventional parameters for safe tethered transportation of space debris.

  16. Shuttle-tethered satellite system definition study. Volume 1: Executive study

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The Tethered Satellite System has great prospects for extending orbital operations capability of the Space Transportation System to science, applications, and technology projects not otherwise attainable. The system will installed in the Shuttle Orbiter and will have the capability to deploy a captive satellite up to 100 km away from the Orbiter. Control and retrieval of the satellite are accomplished by means of a tether line connecting the satellite and the cargo bay mounted equipment in the Orbiter. At low satellite altitudes, the system will permit investigations of a duration that could not be pursued with sounding rockets of free-flying spacecraft. The propose of the Shuttle/Tethered Satellite System Definition Study was to produce the preliminary design, preliminary specifications, gross program plans, and program cost estimate for a 1982 operational verification flight. This was accomplished during a fifteen month effort under by the NASA George C. Marshall Space Flight Center (MSFC). The MSFC Phase 1 and related studies demonstrated the feasibility of the system and served as a starting point for the Phase 2 definition study.

  17. Multibody dynamics driving GNC and system design in tethered nets for active debris removal

    NASA Astrophysics Data System (ADS)

    Benvenuto, Riccardo; Lavagna, Michèle; Salvi, Samuele

    2016-07-01

    Debris removal in Earth orbits is an urgent issue to be faced for space exploitation durability. Among different techniques, tethered-nets present appealing benefits and some open points to fix. Former and latter are discussed in the paper, supported by the exploitation of a multibody dynamics tool. With respect to other proposed capture mechanisms, tethered-net solutions are characterised by a safer capturing distance, a passive angular momentum damping effect and the highest flexibility to unknown shape, material and attitude of the target to interface with. They also allow not considering the centre of gravity alignment with thrust axis as a constraint, as it is for any rigid link solution. Furthermore, the introduction of a closing thread around the net perimeter ensures safer and more reliable grasping and holding. In the paper, a six degrees of freedom multibody dynamics simulator is presented: it was developed at Politecnico di Milano - Department of Aerospace Science and Technologies - and it is able to describe the orbital and attitude dynamics of tethered-nets systems and end-bodies during different phases, with great flexibility in dealing with different topologies and configurations. Critical phases as impact and wrapping are analysed by simulation to address the tethered-stack controllability. It is shown how the role of contact modelling is fundamental to describe the coupled dynamics: it is demonstrated, as a major novel contribution, how friction between the net and a tumbling target allows reducing its angular motion, stabilizing the system and allowing safer towing operations. Moreover, the so-called tethered space tug is analysed: after capture, the two objects, one passive and one active, are connected by the tethered-net flexible link, the motion of the system being excited by the active spacecraft thrusters. The critical modes prevention during this phase, by means of a closed-loop control synthesis is shown. Finally, the connection between

  18. Dynamics of a flexible tethered satellite system utilising various materials for coplanar and non-coplanar models

    NASA Astrophysics Data System (ADS)

    Hong, Aaron Aw Teik; Varatharajoo, Renuganth

    2015-08-01

    This paper discusses the development of mathematical models for a flexible tethered satellite system (TSS) in both planar and co-planar states. The flexible tethered satellite system consists of three rigid bodies with two flexible tethers, each connecting two rigid bodies with one located in the centre and serving as the mothership. The TSS motion includes tether deformations, rotational dynamics, and orbital mechanics. The three materials that are possible to be used for a space tether are tungsten wire, Spectra-2000, and diamond; it should be noted that the diamond used here is in a form of a nanotube thread. The tether will undergo a spinning motion as well in the motorised option. In addition, the air drag perturbation is also considered since the entire TSS is flown around the Low Earth Orbit (LEO), where the air-drag perturbation is dominant. A survival analysis was then performed for planar and non-coplanar models in order to establish a dynamic performance envelope with respect to the tether's tension at different altitudes under the air-drag perturbation. The proposed models were treated numerically and analysed accordingly. Then a comparison study between the coplanar and non-coplanar models were conducted and the difference in their performances was observed and discussed. Although all materials have their own safe operation boundaries, the flexible TSS using tungsten shows a better dynamic performance than the other TSS options in a non-coplanar model.

  19. Lifting options for stratospheric aerosol geoengineering: advantages of tethered balloon systems.

    PubMed

    Davidson, Peter; Burgoyne, Chris; Hunt, Hugh; Causier, Matt

    2012-09-13

    The Royal Society report 'Geoengineering the Climate' identified solar radiation management using albedo-enhancing aerosols injected into the stratosphere as the most affordable and effective option for geoengineering, but did not consider in any detail the options for delivery. This paper provides outline engineering analyses of the options, both for batch-delivery processes, following up on previous work for artillery shells, missiles, aircraft and free-flying balloons, as well as a more lengthy analysis of continuous-delivery systems that require a pipe connected to the ground and supported at a height of 20 km, either by a tower or by a tethered balloon. Towers are shown not to be practical, but a tethered balloon delivery system, with high-pressure pumping, appears to have much lower operating and capital costs than all other delivery options. Instead of transporting sulphuric acid mist precursors, such a system could also be used to transport slurries of high refractive index particles such as coated titanium dioxide. The use of such particles would allow useful experiments on opacity, coagulation and atmospheric chemistry at modest rates so as not to perturb regional or global climatic conditions, thus reducing scale-up risks. Criteria for particle choice are discussed, including the need to minimize or prevent ozone destruction. The paper estimates the time scales and relatively modest costs required if a tethered balloon system were to be introduced in a measured way with testing and development work proceeding over three decades, rather than in an emergency. The manufacture of a tether capable of sustaining the high tensions and internal pressures needed, as well as strong winds, is a significant challenge, as is the development of the necessary pumping and dispersion technologies. The greatest challenge may be the manufacture and launch of very large balloons, but means have been identified to significantly reduce the size of such balloons or aerostats

  20. Constrained tension control of a tethered space-tug system with only length measurement

    NASA Astrophysics Data System (ADS)

    Wen, Hao; Zhu, Zheng H.; Jin, Dongping; Hu, Haiyan

    2016-02-01

    The paper presents a tension control law to stabilize the motions of a Tethered Space-Tug system during its deorbiting process by regulating the tension in the tether. The tension control law is designed on a basis of two straightforward ideas, i.e., the potential energy shaping and the damping injection. The law is expressed in an analytical feedback form in terms of only the tether length without the need of the feedback of full state information. Meanwhile, the requirements of measuring velocities are removed with the aid of a dynamic extension technique based on the feedback interconnection of Euler-Lagrange systems. The positive and bounded tension constraint is taken into consideration explicitly by including a pair of special saturation terms in the feedback control law. The relative motions of the space-tug and the debris are described with respect to a local non-inertial orbital frame of reference, whereas the orbital motion equations of the system are formulated in terms of the modified equinoctial elements of the orbit. Finally, the effectiveness of the proposed scheme is demonstrated via numerical case studies.

  1. Tethered Satellites as an Enabling Platform for Operational Space Weather Monitoring Systems

    NASA Technical Reports Server (NTRS)

    Gilchrist, Brian E.; Krause, Linda Habash; Gallagher, Dennis Lee; Bilen, Sven Gunnar; Fuhrhop, Keith; Hoegy, Walt R.; Inderesan, Rohini; Johnson, Charles; Owens, Jerry Keith; Powers, Joseph; Voronka, Nestor; Williams, Scott

    2013-01-01

    Tethered satellites offer the potential to be an important enabling technology to support operational space weather monitoring systems. Space weather "nowcasting" and forecasting models rely on assimilation of near-real-time (NRT) space environment data to provide warnings for storm events and deleterious effects on the global societal infrastructure. Typically, these models are initialized by a climatological model to provide "most probable distributions" of environmental parameters as a function of time and space. The process of NRT data assimilation gently pulls the climate model closer toward the observed state (e.g., via Kalman smoothing) for nowcasting, and forecasting is achieved through a set of iterative semi-empirical physics-based forward-prediction calculations. Many challenges are associated with the development of an operational system, from the top-level architecture (e.g., the required space weather observatories to meet the spatial and temporal requirements of these models) down to the individual instruments capable of making the NRT measurements. This study focuses on the latter challenge: we present some examples of how tethered satellites (from 100s of m to 20 km) are uniquely suited to address certain shortfalls in our ability to measure critical environmental parameters necessary to drive these space weather models. Examples include long baseline electric field measurements, magnetized ionospheric conductivity measurements, and the ability to separate temporal from spatial irregularities in environmental parameters. Tethered satellite functional requirements are presented for two examples of space environment observables.

  2. A tethering system for direct measurement of cardiovascular function in the caged baboon

    NASA Technical Reports Server (NTRS)

    Byrd, L. D.

    1979-01-01

    A device suitable for the continuous measurement of physiological activity in large, conscious monkeys has permitted the direct recording of systemic arterial blood pressure and heart rate in caged baboons. The device comprises a lightweight fiberglass backpack, retained in place on the baboon by a thoracic elastic band and shoulder straps, and a flexible stainless steel tether connecting the pack to an electrocannular slip-ring in the top center of the baboon's cage. A chronically indwelling arterial catheter inserted retrograde into the abdominal aorta via the internal iliac artery and connected to a small pressure transducer on the pack provides direct measurement of blood pressure and heart rate. Body fluids can be sampled or drugs administered via an indwelling catheter in the inferior vena cava. Electrical and fluid connections between the fiberglass pack and recording and infusion equipment located outside the cage pass through the flexible tether and remain protected from the subject. The reliability of the tethering system has been demonstrated in physiological, pharmacological, and behavioral experiments with baboons.

  3. Space Environmental Effects on Coated Tether Materials

    NASA Technical Reports Server (NTRS)

    Gittemeier, Keith A.; Hawk, Clark W.; Finckenor, Miria M.; Watts, Ed

    2005-01-01

    The University of Alabama in Huntsville s Propulsion Research Center has teamed with NASA's Marshall Space Flight Center (MSFC) to research the effects of atomic oxygen (AO) bombardment on coated tether materials. Tethers Unlimited Inc. has provided several candidate tether materials with various coatings for AO exposure in MSFC s Atomic Oxygen Beam Facility. Additional samples were exposed to ultraviolet (UV) radiation at MSFC. AO erodes most organic materials, and ultraviolet radiation embrittles polymers. This test series was performed to determine the effect of AO and UV on the mechanical integrity of tether materials that were treated with AO-protective coatings, such as polyhedral oligomeric silsesquioxane (POSS) or metallization. Both TUI's Multi-Application Survivable Tether (MAST) Experiment and Marshall Space Flight Center s Momentum Exchange Electrodynamic Reboost (MXER) programs will benefit from this research by helping to determine tether materials and coatings that give the longest life with the lowest mass penalty.

  4. Atomic Oxygen Effects on Coated Tether Materials

    NASA Technical Reports Server (NTRS)

    Gittemeier, Keith A.; Hawk, Clark W.; Finckenor, Miria M.; Watts, Ed

    2005-01-01

    The University of Alabama in Huntsville s Propulsion Research Center has teamed with NASA's Marshall Space Flight Center (MSFC) to research the effects of atomic oxygen (AO) bombardment on coated tether materials. Tethers Unlimited Inc. has provided several candidate tether materials with various coatings for (AO) exposure in MSFC's Atomic Oxygen Beam Facility. Additional samples were exposed to ultraviolet (UV) radiation at MSFC. AO erodes most organic materials, and ultraviolet radiation embrittles polymers. This test series was performed to determine the effect of AO and UV on the mechanical integrity of tether materials that were treated with AO-protective coatings, such as Photosil or metallization. Both TUI's Multi-Application Survivable Tether (MAST) Experiment and Marshall Space Flight Center's Momentum Exchange Electrodynamic Reboost (MXER) programs will benefit from this research by helping to determine tether materials and coatings that give the longest life with the lowest mass penalty.

  5. Establishing a Dynamics Performance Envelope of a Flexible Tethered Satellite System for Planar and Non-Coplanar Models.

    NASA Astrophysics Data System (ADS)

    Teik Hong, Aaron Aw; Varatharajoo, Renuganth

    A Tethered Satellite System (TSS) can be considered as a flexible in-orbit system. However, TSS is typically modelled as a rigid tethered system due to the complexity of its mathematical treatments. In this paper, mathematical models for a flexible tethered satellite system in both planar and co-planar states are developed. The flexible tethered satellite system consists of three rigid bodies with two flexible tethers each connecting two rigid bodies with one located in the centre serving as the mothership. The TSS motion includes tether deformations, rotational dynamics, and orbital mechanics. Three materials (e.g., tungsten wire, Spectra-2000, and diamond) that are commonly used for the tether are proposed as the reference materials; and it should be noted that the tether will undergo a spinning motion as well in the motorized option. In addition, the air drag perturbation is also considered since the entire TSS is flown around Low Earth Orbit (LEO), whereby the air-drag perturbation is dominant. A comprehensive analysis was performed for planar and non-coplanar models in order to establish a dynamics performance envelope with respect to the tether’s tension at different altitudes and air-drag. Bubnov-Galerkin method was employed in order to linearize the non-linear governing equations of elastic vibrations; and once the modal coordinates were obtained, they were substituted according to the equations corresponding to the energy conservation principle. Further, Lagrangian dynamics was utilized to establish the equations of motion of the entire TSS based on the chosen generalized coordinates. The proposed models were treated numerically and analysed accordingly. Then, a comparison study between the coplanar and non-coplanar models was done and the differences in their performances were observed and discussed. Although all materials have their own safe operation boundaries, the flexible TSS using Diamond shows a better dynamics performance than the other TSS

  6. First evaluation of the main parameters in the dynamics of the Small Expendable Deployer System (SEDS) for a tethered satellite

    NASA Technical Reports Server (NTRS)

    Deluca, Luigi

    1990-01-01

    The dynamics of the motion of the Small Expendable Deployer System (SEDS) is studied by using a simplified model in which no external forces (except the gravity gradient field) are applied on the tethered body and the tether is assumed massless. The dynamics of SEDS operation is modeled as a sequence of two phases: the deployment phase and the swing phase. For the first one the velocity dependent forces are found to force the tether forward from the local vertical. When the deployment ends, Coriolis effects vanish and the swing phase begins, which is characterized by a wide free libration. The time duration as well as velocity, acceleration and tension of the tethered body are estimated for both deployment and swing phases.

  7. An Automated System for Measuring Microphysical and Radiative Cloud Characteristics from a Tethered Balloon

    SciTech Connect

    Dr. Paul Lawson

    2004-03-15

    OAK-B135 The rate of climate change in polar regions is now felt to be a harbinger of possible global warming. Long-lived, relatively thin stratus clouds play a predominant role in transmitting solar radiation and trapping long wave radiation emitted from open water and melt ponds. In situ measurements of microphysical and radiative properties of Arctic and Antarctic stratus clouds are needed to validate retrievals from remote measurements and simulations using numerical models. While research aircraft can collect comprehensive microphysical and radiative data in clouds, the duration of these aircraft is relatively short (up to about 12 hours). During the course of the Phase II research, a tethered balloon system was developed that supports miniaturized meteorological, microphysical and radiation sensors that can collect data in stratus clouds for days at a time. The tethered balloon system uses a 43 cubic meter balloon to loft a 17 kg sensor package to altitudes u p to 2 km. Power is supplied to the instrument package via two copper conductors in the custom tether. Meteorological, microphysical and radiation data are recorded by the sensor package. Meteorological measurements include pressure, temperature, humidity, wind speed and wind direction. Radiation measurements are made using a 4-pi radiometer that measures actinic flux at 500 and 800 nm. Position is recorded using a GPS receiver. Microphysical data are obtained using a miniaturized version of an airborne cloud particle imager (CPI). The miniaturized CPI measures the size distribution of water drops and ice crystals from 9 microns to 1.4 mm. Data are recorded onboard the sensor package and also telemetered via a 802.11b wireless communications link. Command signals can also be sent to the computer in the sensor package via the wireless link. In the event of a broken tether, a GMRS radio link to the balloon package is used to heat a wire that burns 15 cm opening in the top of the balloon. The balloon and

  8. Vehicle tethered aerostat optoelectronic monitoring platform system for Shanghai World EXPO

    NASA Astrophysics Data System (ADS)

    Zhou, Weihu; Wang, Yawei; Han, Xiaoquan; Yuan, Jiang

    2010-08-01

    To monitor the whole Shanghai Expo Park, a vehicle tethered aerostat optoelectronic monitoring platform with the characteristic of time-sensitive and all-weather monitoring is described in detail in this paper, which is hung beneath the tethered balloon and equipped with a variety of payloads, including visible light monitoring system, infrared monitoring system, hyperspectral monitoring system, GPS/INS system, monitoring and control system and so on. These equipments can be used for real-time monitoring, environmental monitoring, and ground target location of Shanghai Expo Park. The output High Definition (HD) image of Shanghai Expo Park from visible light monitoring system is clear and stable, and the stabilization accuracy of visual axis is 0.07°(3δ). The optoelectronic monitoring platform system uses the target location technology based on Global Position System/Inertial Navigation System (GPS/INS) system to output real-time location data compatible with Geographic Information System (GIS). Test results show that the maximum errors between the location results (latitude and longitude) solved by the target location program and the reference target are 0.2 0/00(latitude) and 2 0/00(longitude). Now the whole system has been used for surveillance the Shanghai Expo Park since April 2010.

  9. Tethered gravity laboratories study

    NASA Technical Reports Server (NTRS)

    Lucchetti, F.

    1990-01-01

    The scope of the study is to investigate ways of controlling the microgravity environment of the International Space Station by means of a tethered system. Four main study tasks were performed. First, researchers analyzed the utilization of the tether systems to improve the lowest possible steady gravity level on the Space Station and the tether capability to actively control the center of gravity position in order to compensate for activities that would upset the mass distribution of the Station. The purpose of the second task was to evaluate the whole of the experiments performable in a variable gravity environment and the related beneficial residual accelerations, both for pure and applied research in the fields of fluid, materials, and life science, so as to assess the relevance of a variable g-level laboratory. The third task involves the Tethered Variable Gravity Laboratory. The use of the facility that would crawl along a deployed tether and expose experiments to varying intensities of reduced gravity is discussed. Last, a study performed on the Attitude Tether Stabilizer concept is discussed. The stabilization effect of ballast masses tethered to the Space Station was investigated as a means of assisting the attitude control system of the Station.

  10. The stabilization interval system of a tethered descent underwater vehicle

    NASA Astrophysics Data System (ADS)

    Gayvoronskiy, S. A.; Ezangina, T.; Khozhaev, I.; Efimov, S. V.

    2016-04-01

    To damp the vertical oscillations of a descent submersible caused by dusting the control system utilizing a shock-absorbing hoist located on the submersible was developed. A robust proportional-plus-integral action controller was included in the control loop to ensure acceptable dynamic properties of the system by interval variations of the module mass, the rope length, the equivalent value of stiffness of a spring linkage and the equivalent value of damping factor of the spring linkage. A parametric synthesis of the controller was carried out on the basis of the robust expansion of the coefficient method of the quality rating estimation. The system operability was confirmed by the results of the digital simulation parameters

  11. Feasibility Study of Space Based Solar Power to Tethered Aerostat Systems

    NASA Technical Reports Server (NTRS)

    Blank, Stephen J.; Leete, Stephen J.; Jaffe, Paul

    2013-01-01

    The feasibility of two-stage Space-Based Solar Power to Tethered Aerostat to Earth (SSP-TA) system architectures that offer significant advantages over conventional single stage space-to-earth architectures is being studied. There have been many proposals for the transmission of solar power collected in space to the surface of the earth so that solar energy could provide a major part of the electric power requirements on earth. There are, however, serious difficulties in implementing the single stage space-based solar power systems that have been previously studied. These difficulties arise due to: i) the cost of transporting the components needed for the extremely large microwave transmit beaming aperture into space orbit, ii) the even larger collection apertures required on earth, iii) the potential radiation hazard to personnel and equipment on earth, and iv) a lack of flexibility in location of the collection station on the earth. Two candidate system architectures are described here to overcome these difficulties. In both cases a two-stage space to tethered aerostat to earth transmission system (SSP-TA) is proposed. The use of high altitude tethered aerostats (or powered airships) avoids the effects of attenuation of EM energy propagating through the earth s lower atmosphere. This allows the use of beaming frequencies to be chosen from the range of high millimeter (THz) to near-infra-red (NIR) to the visible. This has the potential for: i) greatly reduced transportation costs to space, ii) much smaller receiver collection apertures and ground stations, iii) elimination of the potential radiation hazard to personnel and equipment on earth, and iv) ease in transportation and flexibility in location of the collection station on the earth. A preliminary comparison of system performance and efficiencies is presented.

  12. The Science and Applications Tethered Platform (SATP) project

    NASA Technical Reports Server (NTRS)

    Merlina, P.

    1986-01-01

    The capabilities of tether systems in orbit are going to be demonstrated by the first planned flights of the Tethered Satellite System (TSS). These test flights will investigate the properties of tether systems as low altitude atmospheric research facilities and as electric power generators. Studies are being conducted with the purpose of testing a variety of concepts and approaches. A comparative analysis of results will allow the choosing of the most promising ideas for further development. The broad range of applications presently under study include applications in electrodynamics, transportation, microgravity in addition to basic research. The SATP project definition study is now about midway through its first phase. The analyses conducted have led to an appraisal of users interest in the project and to a deeper understanding of the problems associated with large, long-lived tether systems in space. In addition, two specialized platform designs, devoted to microgravity and precise pointing applications, are being studied because of their potential usefulness and the promise of technical feasibility.

  13. Simulated Space Environment Effects on Tether Materials with Protective Coatings

    NASA Technical Reports Server (NTRS)

    Finckenor, Miria M.; Watts, Ed

    2005-01-01

    Atomic oxygen (AO) erodes most organic materials. and ultraviolet radiation embrittles polymers. A previous study indicated untreated polymers such as ultra-high molecular weight polyethylene (UHMWPE) are severely degraded when exposed to AO. This test series was performed to determine the effect of AO and UV on the mechanical integrity of tether materials that were treated with AO-protective coatings. Three coating systems were evaluated for their ability to protect the underlying material from AO erosion. The first coating system is the Photosil surface modification process which incorporates silicon-containing functional groups into the top micron of an organic material. The Photosil process has had favorable results with polyurethane- and epoxy-based thermal control coatings . The second coating system is metallization, in this case nickel. The third coating system is silsesquioxane. The Marshall Space Flight Center Atomic Oxygen Beam Facility (AOBF) was used to simulate low Earth orbit AO of 5 eV energy. In addition, some tether samples were exposed to ultraviolet radiation then evaluated for any changes in mechanical strength. Tether missions, such as a momentum-exchange/electrodynamic reboost (MXER) tether, may benefit from this research.

  14. Technical and economic assessment of tethered wind energy systems

    SciTech Connect

    Furuya, O.; Maekawa, S.

    1984-08-01

    The wind energy existing at high altitude has been investigated as a potential energy resource in the United States. In terms of the average power density, it can be as high as 16 KW/m/sup 2/ at northeastern U.S. sites such as New York, which can be compared to 0.5 KW/m/sup 2/, the maximum ground level value at the U.S. sites. For a lifting generation device, a VTOL concept, new to this type of TWES, which combines the fixed wing with helicopter technology was extensively studied. The cost of electricity (COE) with such a system was determined and found to be competitive to that of fossil fuel in the near future.

  15. Tethered Lubricants

    SciTech Connect

    Archer, Lynden

    2010-09-15

    We have performed extensive experimental and theoretical studies of interfacial friction, relaxation dynamics, and thermodynamics of polymer chains tethered to points, planes, and particles. A key result from our tribology studies using lateral force microscopy (LFM) measurements of polydisperse brushes of linear and branched chains densely grafted to planar substrates is that there are exceedingly low friction coefficients for these systems. Specific project achievements include: (1) Synthesis of three-tiered lubricant films containing controlled amounts of free and pendent PDMS chains, and investigated the effect of their molecular weight and volume fraction on interfacial friction. (2.) Detailed studies of a family of hairy particles termed nanoscale organic hybrid materials (NOHMs) and demonstration of their use as lubricants.

  16. Multiple degree-of-freedom tracking for attitude control of an experimental system on tether-stabilized platform

    NASA Astrophysics Data System (ADS)

    Angrilli, Francesco; Baglioni, Pietro; Bianchini, Gianandrea; da Forno, Roberto; Fanti, Giulio; Mozzi, Massimo

    1991-08-01

    A study has been conducted about attitude control and pointing of an optical instrument (a Schmidt-type telescope) connected to the space station via a tether 2 to 10 km long, mounted on a platform. The tether plays a multifunctional role, including elastic suspension and data and power transmission. It will insulate the platform from dynamic noise, light, and other pollution from the space station. Furthermore, stabilization and active attitude control will be achieved by moving the attachment point of the tether with respect to the platform itself. A bi- dimensional model of this system has been realized and tested in the laboratory. The measurement and control concept that works on the basis of a computer vision system is discussed. The system is used to stabilize a platform floating on an air table attached to a fixed point through a tether, via a closed loop position control circuit. This is achieved through a CCD camera (768 X 512 pixels), an image processing software, and a dc motor with encoder which controls the attitude of the platform moving its attachment point. The tracking function is realized via a multiple windows technique using an algorithm based on the linearized equations of motion of the platform. The performance of the overall system is presented. An analysis of system characteristics with respect to a real application is carried out. In particular, the possibility of achieving stabilization and active attitude control of such a system by moving the attach point of the tether has been investigated.

  17. Avionics Tether Operations Control

    NASA Technical Reports Server (NTRS)

    Glaese, John R.

    2001-01-01

    The activities described in this Final Report were authorized and performed under Purchase Order Number H32835D, issued as part of NASA contract number NAS8-00114. The period of performance of this PO was from March 1 to September 30, 2001. The primary work activity was the continued development and updating of the tether dynamic simulation tools GTOSS (Generalized Tethered Object System Simulation) and TSSIM (Tethered Satellite System) and use of these and other tools in the analysis of various tether dynamics problems. Several updated versions of GTOSS were delivered during the period of performance by the author of the simulation, Lang Associates' David Lang. These updates had mainly to do with updated documentation and an updated coordinate system definition to the J2000 standards. This Final Report is organized by the months in which the activities described were performed. The following sections review the Statement of Work (SOW) and activities performed to satisfy it.

  18. Photon antibunching and bunching in a ring-resonator waveguide quantum electrodynamics system.

    PubMed

    Chen, Zihao; Zhou, Yao; Shen, Jung-Tsung

    2016-07-15

    We numerically investigate the photonic state generation and its nonclassical correlations in a ring-resonator waveguide quantum electrodynamics system. Specifically, we discuss photon antibunching and bunching in various scenarios, including the imperfect resonator with backscattering and dissipations. Our numerical results indicate that an imperfect ring resonator with backscattering can enhance the quality of antibunching. In addition, we also identify the quantum photonic halo phenomenon in the photon scattering dynamics and the shoulder effect in the second-order correlation function. PMID:27420523

  19. T-Rex: A Japanese Space Tether Experiment

    NASA Technical Reports Server (NTRS)

    Johnson, Les

    2009-01-01

    serves both to drive the current and then to act on the current to decelerate the system. One of the most important features of tether thrusters is that they use renewable energy sources to drive the electrical current flow in either the orbit-raising or orbit-lowering modes. Sources inherent to Earth orbit are used. To raise the orbit, sunlight can be converted to the electrical energy required to drive the tether current. To lower the orbit, the orbital energy itself (supplied by the Earth-to-orbit launcher when it raises the system into orbit) is the energy source of the tether current via the action of the Lorentz Force. Electrodynamic tethers can be directly applied to a wide spectrum of uses in space. As a propulsion system, they include satellite de-orbit, transfer of a satellite from one orbit to another, altitude maintenance for large spacecraft such as the International Space Station, and since it works wherever there is a magnetic field and an ionosphere planetary exploration missions. An electrodynamic tether upper stage could be used as an Orbit Transfer Vehicle (OTV) to move payloads within low earth orbit. The OTV would rendezvous with the payload and launch vehicle, grapple the payload and maneuver it to a new orbital altitude or inclination without the use of boost propellant. The tug could then lower its orbit to rendezvous with the next payload and repeat the process. Conceivably, such a system could perform several orbital maneuvering assignments without resupply, making it relatively inexpensive to operate.

  20. Design Rules and Analysis of a Capture Mechanism for Rendezvous between a Space Tether and Payload

    NASA Technical Reports Server (NTRS)

    Sorensen, Kirk F.; Canfield, Stephen L.; Norris, Marshall A.

    2006-01-01

    Momentum-exchange/electrodynamic reboost (MXER) tether systems have been proposed to serve as an "upper stage in space". A MXER tether station would boost spacecraft from low Earth orbit to a high-energy orbit quickly, like a high-thrust rocket. Then, it would slowly rebuild its orbital momentum through electrodynamic thrust, minimizing the use of propellant. One of the primary challenges in developing a momentum-exchange/electrodynamic reboost tether system as identified by the 2003 MXER Technology Assessment Group is in the development of a mechanism that will enable the processes of capture, carry and release of a payload by the rotating tether as required by the MXER tether approach. This paper will present a concept that will achieve the desired goals of the capture system. This solution is presented as a multi-DOF (degree-of-freedom) capture mechanism with nearly passive operation that features matching of the capture space and expected window of capture error, efficient use of mass and nearly passive actuation during the capture process. This paper will describe the proposed capture mechanism concept and provide an evaluation of the concept through a dynamic model and experimental tests performed on a prototype article of the mechanism in a dynamically similar environment. This paper will also develop a set of rules to guide the design of such a capture mechanism based on analytical and experimental analyses. The primary contributions of this paper will be a description of the proposed capture mechanism concept, a collection of rules to guide its design, and empirical and model information that can be used to evaluate the capability of the concept

  1. No Drama Quantum Electrodynamics?

    NASA Astrophysics Data System (ADS)

    Akhmeteli, Andrey

    2015-03-01

    Is it possible to offer a ``no drama'' quantum electrodynamics, as simple (in principle) as classical electrodynamics - a theory described by a system of partial differential equations (PDE) in 3+1 dimensions, but reproducing unitary evolution of a quantum field theory in the Fock space? The following results suggest an affirmative answer: 1. The scalar field can be algebraically eliminated from scalar electrodynamics. 2. After introduction of a complex 4-potential (producing the same electromagnetic field (EMF) as the standard real 4-potential), the spinor field can be algebraically eliminated from spinor electrodynamics. 3. The resulting theories describe independent evolution of EMF and can be embedded into quantum field theories. Another fundamental result: in a general case, the Dirac equation is equivalent to a 4th order PDE for just one component, which can be made real by a gauge transform. Issues related to the Bell theorem and the connection with Barut's self-field electrodynamics are discussed.

  2. A revolutionary and operational tethered aerostat system illustrating new LTA technology. [for ground-air-ground communications

    NASA Technical Reports Server (NTRS)

    Menke, J. A.

    1975-01-01

    An operational tethered aerostat system, which demonstrates utility of LTA systems, is described. It was made possible by development of a reliable tethered aerostat that is used to support broadcast equipment at an altitude of 10,000 feet. Two elements of the TCOM system, the aerostat and mooring station, are particularly relevant to the LTA Workshop. They demonstrate the feasibility of using LTA vehicles in real, operational, all-weather applications and, in addition, illustrate an advance in the overall technology base of LTA. The aerostat and the mooring station, including their technical design features and demonstrated performance characteristics, are described.

  3. Effect of the finite size of an asteroid on its deflection using a tether-ballast system

    NASA Astrophysics Data System (ADS)

    Mashayekhi, Mohammad J.; Misra, Arun K.

    2016-04-01

    Potentially hazardous near-Earth objects which can impose a significant threat on life on the planet have generated a lot of interest in the study of various asteroid deflection strategies. There are numerous asteroid deflection techniques suggested and discussed in the literature. This paper is focused on one of the non-destructive asteroid deflection strategies by attaching a long tether-ballast system to the asteroid. In the existing literature on this technique, very simplified models of the asteroid-tether-ballast system including a point mass model of the asteroid have been used. In this paper, the dynamical effect of using a finite size asteroid model on the asteroid deflection achieved is analyzed in detail. It has been shown that considering the finite size of the asteroid, instead of the point mass approximation, can have significant influence on the deflection predicted. Furthermore the effect of the tether-deployment stage, which is an essential part of any realistic asteroid deflection mission, on the predicted deflection is studied in this paper. Finally the effect of cutting the tether on the deflection achieved is analyzed and it has been shown that depending on the orbital properties of the asteroid as well as its size and rotational rate, cutting the tether at an appropriate time can increase the deflection achieved. Several numerical examples have been used in this paper to elaborate on the proposed technique and to quantitatively analyze the effect of different parameters on the asteroid deflection.

  4. Effect of the finite size of an asteroid on its deflection using a tether-ballast system

    NASA Astrophysics Data System (ADS)

    Mashayekhi, Mohammad J.; Misra, Arun K.

    2016-07-01

    Potentially hazardous near-Earth objects which can impose a significant threat on life on the planet have generated a lot of interest in the study of various asteroid deflection strategies. There are numerous asteroid deflection techniques suggested and discussed in the literature. This paper is focused on one of the non-destructive asteroid deflection strategies by attaching a long tether-ballast system to the asteroid. In the existing literature on this technique, very simplified models of the asteroid-tether-ballast system including a point mass model of the asteroid have been used. In this paper, the dynamical effect of using a finite size asteroid model on the asteroid deflection achieved is analyzed in detail. It has been shown that considering the finite size of the asteroid, instead of the point mass approximation, can have significant influence on the deflection predicted. Furthermore the effect of the tether-deployment stage, which is an essential part of any realistic asteroid deflection mission, on the predicted deflection is studied in this paper. Finally the effect of cutting the tether on the deflection achieved is analyzed and it has been shown that depending on the orbital properties of the asteroid as well as its size and rotational rate, cutting the tether at an appropriate time can increase the deflection achieved. Several numerical examples have been used in this paper to elaborate on the proposed technique and to quantitatively analyze the effect of different parameters on the asteroid deflection.

  5. Tether Transport System Study Summary Performed under Contract to Marshall Space Flight Center

    NASA Technical Reports Server (NTRS)

    Vonderwell, Dan; Bangham, Mike; Dionne, Heather; Fleming, Beth; Klus, Bill; Herring, Karmel; Suggs, Elton; Walker, Larry; Lorenzini, Enrico; Cosmo, Mario L.; Kaiser, Markus; Vestal, Linda; Johnson, Les; Carrington, Connie

    1998-01-01

    The main rationale for this study is to reduce the mission cost of transporting payloads to GEO. A two stage tether transport system was proposed for boosting payloads from LEO to GTO/GEO. The feasibility of the concept is addressed from the point of view of orbital mechanics and other principles of physics. The report presents the results of an engineering analysis that defines the system, major elements and subsystems, and assesses the feasibility (i.e., the technology readiness level) of designing and developing the system. Results indicate that significant cost savings can be realized over traditional upper stages within a few launches. Certain key technical issues, such as payload rendezvous and capture, need to be addressed in future studies. Advancements in certain technology areas, such as power generation and highly efficient propulsion systems, will have significant effects on the overall system design.

  6. Method of Deployment of a Space Tethered System Aligned to the Local Vertical

    NASA Astrophysics Data System (ADS)

    Zakrzhevskii, A. E.

    2016-09-01

    The object of this research is a space tether of two bodies connected by a flexible massless string. The research objective is the development and theoretical justification of a novel approach to the solution of the problem of deployment of the space tether in a circular orbit with its alignment to the local vertical. The approach is based on use of the theorem on the angular momentum change. It allows developing the open-loop control of the tether length that provides desired change of the angular momentum of the tether under the effect of the gravitational torque to the value, which corresponds to the angular momentum of the deployed tether aligned to the local vertical. The given example of application of the approach to a case of deployment of a tether demonstrates the simplicity of use of the method in practice, and also the method of validation of the mathematical model.

  7. Method of Deployment of a Space Tethered System Aligned to the Local Vertical

    NASA Astrophysics Data System (ADS)

    Zakrzhevskii, A. E.

    2016-04-01

    The object of this research is a space tether of two bodies connected by a flexible massless string. The research objective is the development and theoretical justification of a novel approach to the solution of the problem of deployment of the space tether in a circular orbit with its alignment to the local vertical. The approach is based on use of the theorem on the angular momentum change. It allows developing the open-loop control of the tether length that provides desired change of the angular momentum of the tether under the effect of the gravitational torque to the value, which corresponds to the angular momentum of the deployed tether aligned to the local vertical. The given example of application of the approach to a case of deployment of a tether demonstrates the simplicity of use of the method in practice, and also the method of validation of the mathematical model.

  8. Self-adjusting control system of the electrodynamic velocity transducer for Mössbauer spectrometer

    NASA Astrophysics Data System (ADS)

    Zekhtser, M. Yu.; Revyakin, A. S.; Sarychev, D. A.

    2016-08-01

    The novel control system has been developed on the basis of motion equation for the moving part of the electrodynamic velocity transducer of Mössbauer spectrometer. The motion equation coefficients are the parameters of its vibrating system. The square of cyclic eigenfrequency and damping factor are automatically determined by the control software for the spectrometer using the express analysis of free damped oscillations before any measurements are taken. The control system does not require manual adjustment of the spectrometer before the experiment. It exhibits accuracy of self-tuning and high degree of Doppler modulation stability in long-term experiments, providing high quality Mössbauer spectra.

  9. Currents between tethered electrodes in a magnetized laboratory plasma

    NASA Technical Reports Server (NTRS)

    Stenzel, R. L.; Urrutia, J. M.

    1989-01-01

    Laboratory experiments on important plasma physics issues of electrodynamic tethers were performed. These included current propagation, formation of wave wings, limits of current collection, nonlinear effects and instabilities, charging phenomena, and characteristics of transmission lines in plasmas. The experiments were conducted in a large afterglow plasma. The current system was established with a small electron-emitting hot cathode tethered to an electron-collecting anode, both movable across the magnetic field and energized by potential difference up to V approx.=100 T(sub e). The total current density in space and time was obtained from complete measurements of the perturbed magnetic field. The fast spacecraft motion was reproduced in the laboratory by moving the tethered electrodes in small increments, applying delayed current pulses, and reconstructing the net field by a linear superposition of locally emitted wavelets. With this technique, the small-amplitude dc current pattern is shown to form whistler wings at each electrode instead of the generally accepted Alfven wings. For the beam electrode, the whistler wing separates from the field-aligned beam which carries no net current. Large amplitude return currents to a stationary anode generate current-driven microinstabilities, parallel electric fields, ion depletions, current disruptions and time-varying electrode charging. At appropriately high potentials and neutral densities, excess neutrals are ionized near the anode. The anode sheath emits high-frequency electron transit-time oscillations at the sheath-plasma resonance. The beam generates Langmuir turbulence, ion sound turbulence, electron heating, space charge fields, and Hall currents. An insulated, perfectly conducting transmission line embedded in the plasma becomes lossy due to excitation of whistler waves and magnetic field diffusion effects. The implications of the laboratory observations on electrodynamic tethers in space are discussed.

  10. Change in the coil distribution of electrodynamic suspension system

    NASA Technical Reports Server (NTRS)

    Tanaka, Hisashi

    1992-01-01

    At the Miyazaki Maglev Test Center, the initial test runs were completed using a system design that required the superconducting coils to be parallel with the ground levitation coils. Recently, the coil distribution was changed to a system such that the two types of coils were perpendicular to each other. Further system changes will lead to the construction of a side wall levitation system. It is hoped that the development will culminate in a system whereby a superconducting coil will maintain all the functions: levitation, propulsion, and guidance.

  11. In-Space Transportation with Tethers

    NASA Technical Reports Server (NTRS)

    Lorenzini, Enrico C.

    1999-01-01

    Any analysis of electrodynamic tethers for Space Station applications will soon arrive at the conclusion that currents on the order of 10 A are required. For power generation, we have to foresee needs of several kilowatts even for an emergency backup system. For reboost, we need thrust forces on the order of a Newton, due to the large aerodynamic drag of the Station. In addition, we are restricted by the need to keep perturbations to the Station environment to a minimum. Very long tethers are ruled out by this condition, as they would move the system's center of gravity too much and pose additional operational problems when the Station is docking with other spacecraft. It is easy to show that "standard" tether systems, such as TSS-1, which rely on a large spherical surface to collect electron current from the ionosphere, are unsuitable for ISS applications. A study conducted by MSFC into the possible use of the TSS - 1/R system on the Space Station came to the conclusion that it did not make sense. A quick calculation, using the 10 A benchmark, shows why. TSS-LR collected I A, while the satellite was biased to 1.5 kV. This was twice what had been predicted. Even so, the current collected by the satellite was observed to increase only as the square root of the bias voltage. Thus, to achieve 10 A with the TSS-1 system under the same (daytime) conditions would require a bias voltage of 150 kV, or a tether length of over 850 km! Going to a larger surface would help some, but there is a strong law of diminishing returns for that route. Even if very large spheres were to be allowed (say of 8 m radius), which might achieve useful power levels during optimal conditions of daytime plasma densities with a tether 10 km long, they would suffer from the other Achilles heel of passive spherical collectors: a strong drop in the current (and power goes as the square of the current), as the low plasma densities are encountered during the third of the orbit which is in the Earth

  12. General theory based on fluctuational electrodynamics for van der Waals interactions in colloidal systems

    SciTech Connect

    Yannopapas, Vassilios

    2007-12-15

    A rigorous theory for the determination of the van der Waals interactions in colloidal systems is presented. The method is based on fluctuational electrodynamics and a multiple-scattering method which provides the electromagnetic Green's tensor. In particular, expressions for the Green's tensor are presented for arbitrary, finite collections of colloidal particles, for infinitely periodic or defected crystals, as well as for finite slabs of crystals. The presented formalism allows for ab initio calculations of the van der Waals interactions in colloidal systems since it takes fully into account retardation, many-body, multipolar, and near-field effects.

  13. Tethered Dynamics Explorer and Tethered Atmospheric Probe - A low-cost, low-risk tethered satellite program

    NASA Technical Reports Server (NTRS)

    Deloach, R.; Wood, G.; Crumbly, K.; Rupp, C.; Harrison, J.

    1989-01-01

    A tethered satellite flight program to test theoretical studies of tether concepts is proposed. The program consists of multiple flights of an ELV such as the Delta II, using the Small Expendable Deployment System (SEDS) to deploy two instrumented satellite payloads, the Tethered Dynamics Explorer (TDE) and the Tethered Atmospheric Probe (TAP). The applications and characteristics of the TDE and the TAP are described, including verification of the SEDS, the validation of the dynamics and control model for low-tension deployment and the force and moment instrumentation, the demonstration of tether initiated reentry, the collection of in-situ atmospheric and aerothermodynamic data, and the study of long-term tether exposure.

  14. Nonlinear normal modes in electrodynamic systems: A nonperturbative approach

    NASA Astrophysics Data System (ADS)

    Kudrin, A. V.; Kudrina, O. A.; Petrov, E. Yu.

    2016-06-01

    We consider electromagnetic nonlinear normal modes in cylindrical cavity resonators filled with a nonlinear nondispersive medium. The key feature of the analysis is that exact analytic solutions of the nonlinear field equations are employed to study the mode properties in detail. Based on such a nonperturbative approach, we rigorously prove that the total energy of free nonlinear oscillations in a distributed conservative system, such as that considered in our work, can exactly coincide with the sum of energies of the normal modes of the system. This fact implies that the energy orthogonality property, which has so far been known to hold only for linear oscillations and fields, can also be observed in a nonlinear oscillatory system.

  15. Electrodynamic System of Earth in Moon and Solar Tides Investigation

    NASA Astrophysics Data System (ADS)

    Grunskaya, Lubov; Isakevich, Valiriy

    Since 2000 there has been working the united system of monitoring of electrical and geomagnetic fields of ELF range of the atmosphere boundary surface layer at the spaced apart stations: Vladimir State physical experimental ground; the station of RAS Institute of Sun and Earth physics at Lake Baikal; the station in Paratunka (Kamchatka); the station in Obninsk. There has been developed a programme-analytical system (PAS) to investigate signal structures in spectral and time series, caused by geophysical and astrophysical processes based on the method of eigen vectors. There has been developed a programme and analytical system to investigate the signal structure in the spectral and time series caused by geophysical processes. There has been estimated the amplitude and investigated the properties of the Earth atmosphere boundary layer electrical field components localized spectrally at the frequencies of the moon and solar tides. There has been exposed a method of determination of relative and absolute amplitudes of the main components of the eigen series. There has been investigated coherence of the spectral components at the frequencies of solar and moon tides. The work is carried out with supporting of RFFI № 14-07-97510, State Task to Universities on 2014-2016.

  16. Optimization of motion control laws for tether crawler or elevator systems

    NASA Technical Reports Server (NTRS)

    Swenson, Frank R.; Von Tiesenhausen, Georg

    1988-01-01

    Based on the proposal of a motion control law by Lorenzini (1987), a method is developed for optimizing motion control laws for tether crawler or elevator systems in terms of the performance measures of travel time, the smoothness of acceleration and deceleration, and the maximum values of velocity and acceleration. The Lorenzini motion control law, based on powers of the hyperbolic tangent function, is modified by the addition of a constant-velocity section, and this modified function is then optimized by parameter selections to minimize the peak acceleration value for a selected travel time or to minimize travel time for the selected peak values of velocity and acceleration. It is shown that the addition of a constant-velocity segment permits further optimization of the motion control law performance.

  17. Shuttle tethered operations: The effect on orbital trajectory and inertial navigation

    NASA Technical Reports Server (NTRS)

    Lardas, Mark N.

    1989-01-01

    The first full scale test of a large tethered satellite system is planned. The Orbiter will be linked to a 500 kg payload by a 20 km tether, an action with a profound effect on the trajectory of the Orbiter. For the first time in the history of the Shuttle program, the vehicle will conduct prolonged operations with the center of mass of the orbiting system a significant distance from the center of mass of the Space Shuttle Orbiter, a violation of the fundamental assumption made in both the Orbiter ground-based and onboard navigation software. Inertial navigation of tethered operations with the Shuttle is further complicated by the presence of non-conservative forces in the system: Reaction Control System (RCS) translational effects, atmospheric drag, and electro-magnetic dynamics. These can couple with the conservative tether dynamics effects, and degrade the navigation software performance. The primary effects are examined on the Orbiter's trajectory, coupling by conservative forces during tethered operations, and the impact of both on the ability to meet inertial navigation constraints. The impact of electrodynamics, different RCS control modes, commanded attitudes, and attitude deadbands are presented. Operational guidelines which optimize successful mission navigation, and necessary navigation constraints are discussed.

  18. Corrigendum to "Dynamics of a flexible tethered satellite system utilising various materials for coplanar and non-coplanar models" [Adv. Space Res. 56 (2015) 648-663

    NASA Astrophysics Data System (ADS)

    Hong, Aaron Aw Teik; Varatharajoo, Renuganth

    2015-12-01

    The authors would like to thank Dr. N.A. Ismail for some of the discussions found in her thesis as these discussions have facilitated to achieve some of the results published in this article. Therefore, Ismail, N.A., "The Dynamics of a Flexible Motorised Momentum Exchange Tether (MMET)", PhD. thesis, University of Glasgow, UK, pp. 26-41, 2012 is cited accordingly herein. The thesis was missed out from the reference list in the original version of this article due to an oversight with no other intention. Similarly the thesis by Stevens, R.E., "Optimal Control of Electrodynamic Tether Satellites", PhD. thesis, Air Force Institute of Technology, USA, pp. 87-96, 2008 is referred for a further readership completeness.

  19. Propulsive Small Expendable Deployer System (ProSEDS)

    NASA Technical Reports Server (NTRS)

    1999-01-01

    This Quick Time movie is of NASA's Propulsive Small Expendable Deployer System experiment (ProSEDS). ProSEDS will demonstrate the use of an electrodynamic tether, basically a long, thin wire, for propulsion. An electrodynamic tether uses the same principles as electric motors in toys, appliances and computer disk drives, and generators in automobiles and power plants. When electrical current is flowing through the tether, a magnetic field is produced that pushes against the magnetic field of the Earth. For ProSEDS, the current in the tether results by virtue of the voltage generated when the tether moves through the Earth's magnetic field at more than 17,000 mph. This approach can produce drag thrust generating useable power. Since electrodynamic tethers require no propellant, they could substantially reduce the weight of the spacecraft and provide a cost-effective method of reboosting spacecraft. The tether would be a 3.1-mile (5 kilometer) long, ultrathin base-wire tether connected with a 6.2-mile (10 kilometer) long nonconducting tether. The ProSEDS experiment is managed by the Space Transportation Directorate at the Marshall Space Flight Center.

  20. Iterative methods for the solution of very large complex symmetric linear systems of equations in electrodynamics

    SciTech Connect

    Clemens, M.; Weiland, T.

    1996-12-31

    In the field of computational electrodynamics the discretization of Maxwell`s equations using the Finite Integration Theory (FIT) yields very large, sparse, complex symmetric linear systems of equations. For this class of complex non-Hermitian systems a number of conjugate gradient-type algorithms is considered. The complex version of the biconjugate gradient (BiCG) method by Jacobs can be extended to a whole class of methods for complex-symmetric algorithms SCBiCG(T, n), which only require one matrix vector multiplication per iteration step. In this class the well-known conjugate orthogonal conjugate gradient (COCG) method for complex-symmetric systems corresponds to the case n = 0. The case n = 1 yields the BiCGCR method which corresponds to the conjugate residual algorithm for the real-valued case. These methods in combination with a minimal residual smoothing process are applied separately to practical 3D electro-quasistatical and eddy-current problems in electrodynamics. The practical performance of the SCBiCG methods is compared with other methods such as QMR and TFQMR.

  1. Research on Orbital Plasma Electrodynamics (ROPE)

    NASA Technical Reports Server (NTRS)

    Intriligator, Devrie S.

    1998-01-01

    This final report summarizes some of the important scientific contributions to the Research on Orbital Plasma Electrodynamics (ROPE) investigation, to the Tethered Satellite System (TSS) mission, and to NASA that resulted from the work carried out under this contract at Carmel Research Center. These include Dr. Intriligator's participation in the PIT for the TSS-1R simulations and flight, her participation in ROPE team meetings and IWG meetings, her scientific analyses, and her writing and submitting technical papers to scientific journals. The scientific analyses concentrated on the characterization of energetic ions and their possible relation to pickup ion effects, correlation of particle and other effects (e.g., magnetic field, satellite surface), and collaboration with theorists including with ROPE co-investigators. In addition, scientific analyses were carried out of the effects due to satellite gas releases.

  2. Proposed tethered unmanned aerial system for the detection of pollution entering the Chesapeake Bay area

    NASA Astrophysics Data System (ADS)

    Goodman, J.; McKay, J.; Evans, W.; Gadsden, S. Andrew

    2016-05-01

    This paper is based on a proposed unmanned aerial system platform that is to be outfitted with high-resolution sensors. The proposed system is to be tethered to a moveable ground station, which may be a research vessel or some form of ground vehicle (e.g., car, truck, or rover). The sensors include, at a minimum: camera, infrared sensor, thermal, normalized difference vegetation index (NDVI) camera, global positioning system (GPS), and a light-based radar (LIDAR). The purpose of this paper is to provide an overview of existing methods for pollution detection of failing septic systems, and to introduce the proposed system. Future work will look at the high-resolution data from the sensors and integrating the data through a process called information fusion. Typically, this process is done using the popular and well-published Kalman filter (or its nonlinear formulations, such as the extended Kalman filter). However, future work will look at using a new type of strategy based on variable structure estimation for the information fusion portion of the data processing. It is hypothesized that fusing data from the thermal and NDVI sensors will be more accurate and reliable for a multitude of applications, including the detection of pollution entering the Chesapeake Bay area.

  3. Tethers and asteroids for artificial gravity assist in the solar system

    NASA Technical Reports Server (NTRS)

    Penzo, P. A.; Mayer, H. L.

    1984-01-01

    Analytical models are defined for gravity-assist trajectory changes for spacecraft passing massive compact bodies. The models are applied in an examination of the benefits of lowering a tether to an asteroid during a flyby in order to gain a trajectory change equivalent to that from a massive body (planet). Direct flybys yield velocity gains while retrograde flybys shed velocity. The magnitude of the effects are a function of the proximity to the body during flyby. This inherently limits the gravity assist technique used around planets, which usually have atmospheres and can have intense radiation fields. If a spacecraft could extend a tether (such as to be tested on the Orbiter) to snag on an asteroid surface, the potential trajectory/velocity change of the spacecraft would be limited mainly by the tether strength. The encounter physics are treated as a soft collision. Possible applications of the asteroid tether technique are outer planet, Mars and main belt asteroid exploration missions.

  4. How tethered systems can benefit microgravity research in the Space Station era

    NASA Technical Reports Server (NTRS)

    Lavitola, Maria Stella; Giani, Francesco; Briccarello, Mauro

    1989-01-01

    The use of a tethered movable orbiting laboratory for microgravity research is examined. The relation between reduced microgravity carriers and acceleration levels, and the effects of acceleration levels on in-orbit experiments are studied. The tuning of the gravity level at a space laboratory by employing a tether is described. The applications of the variable gravity environment to research in fluids and materials sciences, life sciences, separative techniques, and physical and applied chemistry are discussed.

  5. Possibilities for Continuous Frequency Tuning in Terahertz Gyrotrons with Nontunable Electrodynamic Systems

    NASA Astrophysics Data System (ADS)

    Bratman, V. L.; Savilov, A. V.; Chang, T. H.

    2016-02-01

    Large ohmic losses in the cavities of terahertz gyrotrons may lead to the overlapping of the axial mode spectra. In a number of gyrotron experiments, this effect has been used to provide a fairly broadband frequency tuning by changing appropriately the operating magnetic field and/or accelerating voltage of the gyrotron. Similar to the systems with nonfixed axial structure of the RF electromagnetic field and low diffraction quality, which are due to weak reflections of the operating wave from the collector end of the electrodynamic system, this changing leads to a monotonic change in the axial index of the operating wave and transition from the gyrotron regime to the gyro-BWO regime. According to a theoretical comparison of these two methods performed on the basis of generalization of self-consistent gyrotron equations with allowance for variations in the axial electron momenta, low-reflection systems can provide a higher efficiency and monotonicity of the frequency tuning.

  6. New Tether Ozonesonde System Developed for Uintah Basin Ozone Study in February, 2012

    NASA Astrophysics Data System (ADS)

    Johnson, B. J.; Cullis, P.; Wendell, J.; Hall, E.; Jordan, A.; Albee, R.; Schnell, R. C.

    2012-12-01

    NOAA/ESRL/GMD participated in the February, 2012 UINTAH basin air quality campaign to measure ozone concentrations from surface to 300 meters above ground level. The study region, southwest of Vernal, Utah, is an active oil and gas production and exploration area. During the previous winter in 2011, an air quality study led by state and local agencies and Utah State University measured very high ozone at several sites, exceeding 140 ppbv centered near Ouray, Utah under shallow boundary layer with surface snow-cover conditions. The high ozone conditions never developed during the 2012 campaign. The weather remained dry and warm with typical ozone mixing rations ranging from 20 to 60 ppbv. In order to provide near continuous ozone profiles without consuming a balloon and ozonesonde for each sounding, a tether system was developed by the Global Monitoring Division based upon a motorized deep sea fishing rod and reel with 50 pound line. The lightweight system was shown to be rugged and reliable and capable of conducting an ascending and descending profile to 300 m within 90 minutes. Communication software and data loggers continuously monitor the radiosonde pressure to control the ascent/descent rates and altitude. The system can operate unmanned as it will ascend, descend and hold an altitude as controlled from a laptop computer located up to 30 m distant.

  7. Tethers open new space options

    NASA Astrophysics Data System (ADS)

    Bekey, I.

    1983-04-01

    Several examples of possible applications of the tethering concept in space are examined. In particular, attention is given to a practical design of a 500-kg satellite system to be tethered at a distance of 100 km from the Space Shuttle. The satellite body has the form of a sphere, aerodynamically stabilized and fitted with a dockline adapter that mates with a capture mechanism at the tip of an extendable boom; the tether is a very flexible synthetic line 1-2 mm in diameter. Other applications include a wholly passive stable platform created by tethering two rows of empty Shuttle External Tanks or similar masses 10-20 km apart, a remote docking port for a space station, and constellations of space objects, with tethers used to tie them together and constrain their relative motions.

  8. Study on figure-eight-shaped coil electrodynamic suspension magnetic levitation systems without cross-connection

    SciTech Connect

    Ribani, P.L.; Urbano, N.

    2000-01-01

    Two figure-eight-shaped coils for electrodynamic suspension (EDS) magnetic levitation (MAGLEV) systems without cross-connection are proposed and analyzed. The guideway coils are positioned under the MAGLEV vehicle; they are parallel to the horizontal plane. The interaction of a magnetic module on the vehicle, composed of three or four superconducting (SC) coils, with a guideway module, comprised of two figure-eight coils, is studied by means of the dynamic circuit theory. The currents in the SC coils are supposed to be constant in time while they move as a rigid body, with a constant velocity. Some results are presented and compared with those for a standard side-wall cross-connected system.

  9. Middle atmospheric electrodynamics

    NASA Technical Reports Server (NTRS)

    Kelley, M. C.

    1983-01-01

    A review is presented of the advances made during the last few years with respect to the study of the electrodynamics in the earth's middle atmosphere. In a report of the experimental work conducted, attention is given to large middle atmospheric electric fields, the downward coupling of high altitude processes into the middle atmosphere, and upward coupling of tropospheric processes into the middle atmosphere. It is pointed out that new developments in tethered balloons and superpressure balloons should greatly increase the measurement duration of earth-ionospheric potential measurements and of stratospheric electric field measurements in the next few years. Theoretical work considered provides an excellent starting point for study of upward coupling of transient and dc electric fields. Hays and Roble (1979) were the first to construct a model which included orographic features as well as the classical thunderstorm generator.

  10. Radar cross-section measurements and simulation of a tethered satellite. The small expendable deployer system end-mass payload

    NASA Technical Reports Server (NTRS)

    Cravey, Robin L.; Fralick, Dion T.; Vedeler, Erik

    1995-01-01

    The first Small Expendable Deployer System (SEDS-1), a tethered satellite system, was developed by NASA and launched March 29, 1993 as a secondary payload on a United State Air Force (USAF) Delta-2 launch vehicle. The SEDS-1 successfully deployed an instrumented end-mass payload (EMP) on a 20-km nonconducting tether from the second stage of the Delta 2. This paper describes the effort of NASA Langley Research Center's Antenna and Microwave Research Branch to provide assistance to the SEDS Investigators Working Group (IWG) in determining EMP dynamics by analyzing the mission radar skin track data. The radar cross section measurements taken and simulations done for this study are described and comparisons of the measured data with the simulated data for the EMP at 6 GHz are presented.

  11. Orbital Injection of the SEDSAT Satellite: Tethered Systems Dynamics and Flight Data Analysis

    NASA Technical Reports Server (NTRS)

    Lorenzini, Enrico C.; Gullahorn, Gordon E.; Cosmo, Mario L.; Ruiz, Manuel; Pelaez, Jesus

    1996-01-01

    This report deals with the following topics which are all related to the orbital injection of the SEDSAT satellite: Dynamics and Stability of Tether Oscillations after the First Cut. The dynamics of the tether after the first cut (i.e., without the Shuttle attached to it) is investigated. The tether oscillations with the free end are analyzed in order to assess the stability of the rectilinear configuration in between the two tether cuts; analysis of Unstable Modes. The unstable modes that appear for high libration angles are further investigated in order to determine their occurrences and the possible transition from bound librations to rotations; Orbital Release Strategies for SEDSAT. A parametric analysis of the orbital decay rate of the SEDSAT satellite after the two tether cuts has been carried out as a function of the following free parameters: libration amplitude at the end of deployment, deviation angle from LV at the first cut, and orbital anomaly at the second cut. The values of these parameters that provide a minimum orbital decay rate of the satellite (after the two cuts) have been computed; and Dynamics and Control of SEDSAT. The deployment control law has been modified to cope with the new ejection velocity of the satellite from the Shuttle cargo bay. New reference profiles have been derived as well as new control parameters. Timing errors at the satellite release as a function of the variations of the initial conditions and the tension model parameters have been estimated for the modified control law.

  12. Tethered Spinal Cord Syndrome

    MedlinePlus

    ... Enhancing Diversity Find People About NINDS NINDS Tethered Spinal Cord Syndrome Information Page Table of Contents (click to ... being done? Clinical Trials Organizations What is Tethered Spinal Cord Syndrome? Tethered spinal cord syndrome is a neurological ...

  13. Propulsive Small Expendable Deployer System (ProSEDS)

    NASA Technical Reports Server (NTRS)

    1999-01-01

    NASA's Propulsive Small Expendable Deployer System experiment (ProSEDS) will demonstrate the use of an electrodynamic tether, basically a long, thin wire, for propulsion. An electrodynamic tether uses the same principles as electric motors in toys, appliances and computer disk drives, and generators in automobiles and power plants. When electrical current is flowing through the tether, a magnetic field is produced that pushes against the magnetic field of the Earth. For ProSEDS, the current in the tether results by virtue of the voltage generated when the tether moves through the Earth's magnetic field at more than 17,000 mph. This approach can produce drag thrust generating useable power. Since electrodynamic tethers require no propellant, they could substantially reduce the weight of the spacecraft and provide a cost-effective method of reboosting spacecraft. The initial flight of ProSEDS is scheduled to fly aboard an Air Force Delta II rocket in the summer of 2002. In orbit, ProSEDS will deploy from a Delta II second stage. It will be a 3.1-mile (5 kilometer) long, ultrathin base-wire cornected with a 6.2-mile (10 kilometer) long nonconducting tether. This photograph shows Less Johnson, a scientist at MSFC inspecting the nonconducting part of a tether as it exits a deployer similar to the one to be used in the ProSEDS experiment. The ProSEDS experiment is managed by the Space Transportation Directorate at MSFC.

  14. BOU: Development of a low-cost tethered balloon sensing system for monitoring the lower atmosphere

    NASA Astrophysics Data System (ADS)

    Picos, Rodrigo; Lopez-Grifol, Alvaro; Martinez-Villagrassa, Daniel; Simó, Gemma; Wenger, Burkhard; Dünnermann, Jens; Jiménez, Maria Antonia; Cuxart, Joan

    2016-04-01

    The study of the atmospheric boundary layer, the lowest part of the atmosphere, and the processes that occur therein often requires the observation of vertical profiles of the main meteorological variables, i.e. air temperature and humidity, wind vector and barometric pressure. In particular, when the interest is focused on the air-surface interactions, a high vertical resolution over the first 500 m is required for the observations to describe the physical processes that occur immediately above the surface. Typically, these needs are covered with the use of captive balloons, which are helium-filled balloons tethered to a winch on the ground and a sensor package suspended a short distance below the balloon. Since the commercial version of such instrumental platforms are scarce and expensive, a new low-cost device has been developed in the last years: BOU (tethered Balloon sonde OWL-UIB). In this paper, we focus on the sensor package and data acquisition system part, that is able to fulfill the low-cost requirements. The system uses a low-cost Arduino Mega board as the processor, and stores all the data in a SD card, though an RF connection is also possible but more unreliable. The system has been configured to sample temperature, humidity, air pressure, wind speed, having also a magnetometer and an accelerometer. Sampling time was 1 second, though it was possible to set it faster. It is worth mentioning that the system is easily reconfigurable, and more sensors can be added. The system is powered by a Polymer battery of 1800mA , allowing the system to run continously for more than 6 hours. The temperature is acquired using three different sensors (a HYT 271 calibrated sensor with an accuracy of ±0.2 °C, plus the internal temperature sensors of the wind and pressure sensors, with accuracies around ±0.5 °C). The humidity is also sensed using the calibrated HYT 271 sensor, which features an accuracy of ±1.8%. Air pressure is sensed using a BMP080 sensor, which

  15. The role of tethers on space station

    NASA Technical Reports Server (NTRS)

    Vontiesenhausen, G. (Editor)

    1985-01-01

    The results of research and development that addressed the usefulness of tether applications in space, particularly for space station are described. A well organized and structured effort of considerable magnitude involving NASA, industry and academia have defined the engineering and technological requirements of space tethers and their broad range of economic and operational benefits. The work directed by seven NASA Field Centers is consolidated and structured to cover the general and specific roles of tethers in space as they apply to NASA's planned space station. This is followed by a description of tether systems and operations. A summary of NASA's plans for tether applications in space for years to come is given.

  16. The dynamic phenomena of a tethered satellite: NASA's first Tethered Satellite Mission, TSS-1

    NASA Technical Reports Server (NTRS)

    Ryan, R. S.; Mowery, D. K.; Tomlin, D. D.

    1993-01-01

    The tethered satellite system (TSS) was envisioned as a means of extending a satellite from its base (space shuttle, space station, space platform) into a lower or higher altitude in order to more efficiently acquire data and perform science experiments. This is accomplished by attaching the satellite to a tether, deploying it, then reeling it in. When its mission is completed, the satellite can be returned to its base for reuse. If the tether contains a conductor, it can also be used as a means to generate and flow current to and from the satellite to the base. When current is flowed, the tether interacts with the Earth's magnetic field, deflecting the tether. When the current flows in one direction, the system becomes a propulsive system that can be used to boost the orbiting system. In the other direction, it is a power generating system. Pulsing the current sets up a dynamic oscillation in the tether, which can upset the satellite attitude and preclude docking. A basic problem occurs around 400-m tether length, during satellite retrieval when the satellite's pendulous (rotational) mode gets in resonance with the first lateral tether string mode. The problem's magnitude is determined by the amount of skiprope present coming into this resonance condition. This paper deals with the tethered satellite, its dynamic phenomena, and how the resulting problems were solved for the first tethered satellite mission (TSS-1). Proposals for improvements for future tethered satellite missions are included. Results from the first tethered satellite flight are summarized.

  17. Space Station tethered waste disposal

    NASA Technical Reports Server (NTRS)

    Rupp, Charles C.

    1988-01-01

    The Shuttle Transportation System (STS) launches more payload to the Space Station than can be returned creating an accumulation of waste. Several methods of deorbiting the waste are compared including an OMV, solid rocket motors, and a tether system. The use of tethers is shown to offer the unique potential of having a net savings in STS launch requirement. Tether technology is being developed which can satisfy the deorbit requirements but additional effort is required in waste processing, packaging, and container design. The first step in developing this capability is already underway in the Small Expendable Deployer System program. A developmental flight test of a tether initiated recovery system is seen as the second step in the evolution of this capability.

  18. Nucleolus-tethering system (NoTS) reveals that assembly of photobodies follows a self-organization model.

    PubMed

    Liu, Yin; Liu, Qi; Yan, Qingqing; Shi, Leilei; Fang, Yuda

    2014-04-01

    Protein-protein interactions play essential roles in regulating many biological processes. At the cellular level, many proteins form nuclear foci known as nuclear bodies in which many components interact with each other. Photobodies are nuclear bodies containing proteins for light-signaling pathways in plants. What initiates the formation of photobodies is poorly understood. Here we develop a nucleolar marker protein nucleolin2 (Nuc2)-based method called the nucleolus-tethering system (NoTS) by artificially tethering a protein of interest to the nucleolus to analyze the initiation of photobodies. A candidate initiator is evaluated by visualizing whether a protein fused with Nuc2 forms body-like structures at the periphery of the nucleolus, and other components are recruited to the de novo-formed bodies. The interaction between two proteins can also be revealed through relocation and recruitment of interacting proteins to the nucleolus. Using the NoTS, we test the interactions among components in photobodies. In addition, we demonstrate that components of photobodies such as CONSTITUTIVELY PHOTOMORPHOGENIC 1, photoreceptors, and transcription factors tethered to the nucleolus have the capacity to form body-like structures at the periphery of the nucleolus, which contain other components of photobodies, suggesting a self-organization model for the biogenesis of photobodies. PMID:24554768

  19. No Drama Quantum Electrodynamics?

    NASA Astrophysics Data System (ADS)

    Akhmeteli, Andrey

    2014-03-01

    Is it possible to offer a ``no drama'' quantum electrodynamics, as simple (in principle) as classical electrodynamics - a theory described by a system of partial differential equations (PDE) in 3+1 dimensions, but reproducing unitary evolution of a quantum field theory in the Fock space? The following results suggest an affirmative answer: 1. The scalar field can be algebraically eliminated from scalar electrodynamics. 2. After introduction of a complex 4-potential (producing the same electromagnetic field (EMF) as the standard real 4-potential), the spinor field can be algebraically eliminated from spinor electrodynamics. 3. The resulting theories describe independent evolution of EMF and can be embedded into quantum field theories. Another fundamental result: in a general case, the Dirac equation is equivalent to a 4th order PDE for just one component, which can be made real by a gauge transform. Issues related to the Bell theorem and the connection with Barut's self-field electrodynamics are discussed. A. Akhmeteli, Int'l Journal of Quantum Information, Vol. 9, Suppl., 17-26 (2011) A. Akhmeteli, Journal of Mathematical Physics, Vol. 52, 082303 (2011) A. Akhmeteli, quant-ph/1111.4630 A. Akhmeteli, European Physical Journal C, Vol. 73, 2371 (2013) (open access)

  20. Artist's Concept of Propulsive Small Expendable Deployer System (ProSEDS)

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Pictured is an artist's concept of NASA's Propulsive Small Expendable Deployer System experiment (ProSEDS). ProSEDS will demonstrate the use of an electrodynamic tether, basically a long, thin wire, for propulsion. An electrodynamic tether uses the same principles as electric motors in toys, appliances and computer disk drives, and generators in automobiles and power plants. When electrical current is flowing through the tether, a magnetic field is produced that pushes against the magnetic field of the Earth. For ProSEDS, the current in the tether results by virtue of the voltage generated when the tether moves through the Earth's magnetic field at more than 17,000 mph. This approach can produce drag thrust generating useable power. Since electrodynamic tethers require no propellant, they could substantially reduce the weight of the spacecraft and provide a cost-effective method of reboosting spacecraft. The initial flight of ProSEDS is scheduled to fly aboard an Air Force Delta II rocket in summer of 2002. In orbit, ProSEDS will deploy from a Delta II second stage. It will be a 3.1-mile (5 kilometer) long, ultrathin base-wire tether cornected with a 6.2-mile (10 kilometer) long nonconducting tether. The ProSEDS experiment is managed by the Space Transportation Directorate at the Marshall Space Flight Center.

  1. Applications of Tethers in Space: Workshop Proceedings, Volume 1

    NASA Technical Reports Server (NTRS)

    Baracat, W. A. (Compiler)

    1986-01-01

    The complete documentation of the workshop including all addresses, panel reports, charts, and summaries are presented. This volume presents all the reports on the fundamentals of applications of tethers in space. These applications include electrodynamic interactions, transportation, gravity utilization, constellations, technology and test, and science applications.

  2. Applications of Tethers in Space: workshop proceedings, volume 1

    SciTech Connect

    Baracat, W.A.

    1986-06-01

    The complete documentation of the workshop including all addresses, panel reports, charts, and summaries are presented. This volume presents all the reports on the fundamentals of applications of tethers in space. These applications include electrodynamic interactions, transportation, gravity utilization, constellations, technology and test, and science applications.

  3. Biodegradable, Tethered Lipid Bilayer-Microsphere Systems with Membrane-Integrated α-Helical Peptide Anchors.

    PubMed

    Fried, Eric S; Luchan, Joshua; Gilchrist, M Lane

    2016-04-12

    Supported lipid bilayers (SLBs) are ideally suited for the study of biomembrane-biomembrane interactions and for the biomimicry of cell-to-cell communication, allowing for surface ligand displays that contain laterally mobile elements. However, the SLB paradigm does not include three-dimensionality and biocompatibility. As a way to bypass these limitations, we have developed a biodegradable form of microsphere SLBs, also known as proteolipobeads (PLBs), using PLGA microspheres. Microspheres were synthesized using solvent evaporation and size selected with fluorescence activated cell sorting (FACS). Biomembranes were covalently tethered upon fusion to microsphere supports via short-chain PEG spacers connecting membrane-integrated α-helical peptides and the microsphere surface, affecting membrane diffusivity and mobility as indicated by confocal FRAP analysis. Membrane heterogeneities, which are attributed to PLGA hydrophobicity and rough surface topography, are curtailed by the addition of PEG tethers. This method allows for the presentation of tethered, laterally mobile biomembranes in three dimensions with functionally embedded attachment peptides for mobile ligand displays. PMID:26972467

  4. In-plane payload capture using tethers

    NASA Astrophysics Data System (ADS)

    Williams, Paul; Blanksby, Chris; Trivailo, Pavel; Fujii, Hironori A.

    2005-11-01

    This paper presents a study on utilising space tether technology for the rendezvous and capture of payloads. Tethers are advantageous in space applications due to their low weight and extreme length and significant mass savings may be obtained compared to conventional propulsion systems. However, there are some significant challenges that face the designer of such a system. This paper addresses some of these challenges: (1) Matching the position and velocity of the tether tip for rendezvous with an incoming payload, (2) prolonging the rendezvous manoeuvre to allow maximum time for successful docking of the payload, (3) design of a capture mechanism that allows for errors in the tether tip velocity, (4) control of the post-capture dynamics of the tether, and (5) safety and failsafe design concerns. This paper presents control laws and numerical analysis for each of these challenges and demonstrates the feasibility of payload capture using tether technology.

  5. Generation and injection of e.m. waves in space plasma by means of a long orbiting tether

    NASA Technical Reports Server (NTRS)

    1980-01-01

    The generation and injection of electromagnetic waves in space plasma by means of a long orbiting tether are considered. The objectives include an estimation of the portions of the primary electrodynamic power developed by the tether that goes to excite each of various wave generation and injection mechanisms expected to be present during a tether's orbital flight, an evaluation of the signal levels associated with each one of the mechanisms above, and verification of their detectability with state-of-the-art instrumentation on the Earth surface or elsewhere. The generation and injection of Alfven waves and electron whistler waves were identified as the most relevant mechanisms activited by the electrodynamic tether. The physical mechanisms that govern these two families of phenomena were investigated and the ratio between the power that goes in Alfven waves and in whistlers was derived. The analysis of the possible production of accelerated electrons by the electrodynamic tether was initiated.

  6. Selected tether applications in space: Phase 2

    NASA Technical Reports Server (NTRS)

    Thorsen, M. H.; Lippy, L. J.

    1985-01-01

    System characteristics and design requirements are assessed for tether deployment. Criteria are established for comparing alternate concepts for: (1) deployment of 220 klb space shuttle from the space station; (2) tether assisted launch of a 20,000 lb payload to geosynchronous orbit; (3) placement of the 20,000 lb AXAF into 320 nmi orbit via orbiter; (4) retrieval of 20,000 lb AXAF from 205 nmi circular orbit for maintenance and reboost to 320 nmi; and (5) tethered OMV rendezvous and retrieval of OTV returning from a geosynchronous mission. Tether deployment systems and technical issues are discussed.

  7. Space Test of Bare-Wire Anode Tethers

    NASA Technical Reports Server (NTRS)

    Johnson, L.; Fujii, H. A.; Sanmartin, J. R.

    2007-01-01

    An international team, lead by Tokyo Metropolitan University, is developing a mission concept for a suborbital test of orbital-motion-limited (OML) bare-wire anode current collection for application to electrodynamic tether propulsion. The tether is a tape with a 50-mm width, 0.05-mm thickness, and 1-km length. This will be the first space test of the OML theory. In addition, by being an engineering demonstration (of space tethers), the mission will demonstrate electric beam generation for "sounding" determination of the neutral density profile in the ionospheric "E-layer." If selected by the Institute of Space and Astronautical Science/Japanese Aerospace Exploration Agency (JAXA), the mission will launch in early 2009 using an $520 Sounding Rocket. During ascent, and above =100 km in attitude, the 1-km tape tether will be deployed at a rate of 8 m/s. Once deployed, the tape tether will serve as an anode, collecting ionospheric electrons. The electrons will be expelled into space by a hollow cathode device, thereby completing the circuit and allowing current to flow.This paper will describe the objectives of the proposed mission, the technologies to be employed, and the application of the results to future space missions using electrodynamic tethers for propulsion or power generation.

  8. Tethered gravity laboratories study

    NASA Technical Reports Server (NTRS)

    Lucchetti, F.

    1989-01-01

    Tethered gravity laboratories study is presented. The following subject areas are covered: variable gravity laboratory; attitude tether stabilizer; configuration analysis (AIT); dynamic analysis (SAO); and work planned for the next reporting period.

  9. Proposed aerothermodynamic experiments in transition flow using the NASA/ASI tethered satellite system-2

    NASA Technical Reports Server (NTRS)

    Wood, George M.; Wilmoth, Richard G.; Carlomagno, Giovanni M.; De Luca, Luigi

    1990-01-01

    Aerothermodynamic, aerodynamic, and atmospheric science data acquired between 55 and 150 km has been limited by the lack of vehicles or platforms capable of sustained operation at these altitudes. Tethered satellites, which have been under study for this purpose by NASA, the Italian Space Agency (ASI), and others for more than a decade, are expected to become a reality by mid-1991. This approach, in which an instrumented platform is maintained at a desired altitude by a tether attached to a host vehicle orbiting at higher altitudes, will provide the first opportunity to obtain steady state data over an extended period encompassing one or more orbital revolutions. This paper describes the objectives and measurement methods for the first of the facility-class satellites, the TSS-2, which is proposed for a 1995 deployment, and gives the status of the experiment definition. Monte Carlo modeling of the flow fields at 130 km around the baseline 1.6 m diameter sphere is discussed and illustrative results of the modeling given.

  10. Tethered Satellites as Enabling Platforms for an Operational Space Weather Monitoring System

    NASA Technical Reports Server (NTRS)

    Krause, L. Habash; Gilchrist, B. E.; Bilen, S.; Owens, J.; Voronka, N.; Furhop, K.

    2013-01-01

    Space weather nowcasting and forecasting models require assimilation of near-real time (NRT) space environment data to improve the precision and accuracy of operational products. Typically, these models begin with a climatological model to provide "most probable distributions" of environmental parameters as a function of time and space. The process of NRT data assimilation gently pulls the climate model closer toward the observed state (e.g. via Kalman smoothing) for nowcasting, and forecasting is achieved through a set of iterative physics-based forward-prediction calculations. The issue of required space weather observatories to meet the spatial and temporal requirements of these models is a complex one, and we do not address that with this poster. Instead, we present some examples of how tethered satellites can be used to address the shortfalls in our ability to measure critical environmental parameters necessary to drive these space weather models. Examples include very long baseline electric field measurements, magnetized ionospheric conductivity measurements, and the ability to separate temporal from spatial irregularities in environmental parameters. Tethered satellite functional requirements will be presented for each space weather parameter considered in this study.

  11. Tethered Space Satellite-1 (TSS-1): Technical Roundabouts

    NASA Technical Reports Server (NTRS)

    O'Connor, Brian; Stevens, Jennifer

    2016-01-01

    In the early 1990's US and Italian scientists collaborated to study the electrodynamics of dragging a satellite on a tether through the electrically charged portion of Earth's atmosphere called the ionosphere. An electrical current induced in the long wire could be used for power and thrust generation for a satellite. Other tether uses include momentum exchange, artificial gravity, deployment of sensors or antennas, and gravity-gradient stabilization for satellites. Before the Tethered Space Satellite (TSS-1), no long tether had ever been flown, so many questions existed on how it would actually behave. The TSS consisted of a satellite with science experiments attached to a 12.5 mile long, very thin (0.10 inch diameter) copper wire assembly wound around a spool in the deployer reel mechanism. With the Space Shuttle at an altitude of 160 nautical miles above earth, the satellite was to be deployed by raising it from the Shuttle bay on a boom facing away from Earth. Once cleared of the bay, the deployer mechanism was to slowly feed out the 12-plus miles of tether. Scientific data would be collected throughout the operation, after which the satellite would be reeled back in. Pre-flight testing system level tests involved setting up a tether receiver to catch the 12.5 mile tether onto another reel as it was being unwound by the deployer reel mechanism. Testing only the reel mechanism is straightforward. This test becomes more complicated when the TSS is mounted on the flight pallet at Kennedy Space Center (KSC). The system level tests must be passed before the pallet can be installed into the Space Shuttle cargo bay. A few months before flight, the TSS payload had been integrated onto the Spacelab pallet and system level tests, including unreeling and reeling the tether, had been successfully completed. Some of this testing equipment was then shipped back to the contractor Martin Marietta. Systems-level load analyses, which cannot be run until all information about

  12. Dynamics and control of tethered spacecraft - A brief overview

    NASA Technical Reports Server (NTRS)

    Modi, V. J.; Lakshmanan, P. K.; Misra, A. K.

    1990-01-01

    Work related to the dynamics of tether connected orbiting systems and their control during deployment, operational, and retrieval phases is briefly reviewed. In particular, attention is given to the modeling of tether dynamics and control, end bodies tethered at point masses, deployment dynamics and tension control, and thruster and offset control. Directions of future efforts aimed at gaining a better understanding of the performance of tethered systems are outlined.

  13. Substorm electrodynamics

    NASA Technical Reports Server (NTRS)

    Stern, David P.

    1990-01-01

    The present one-dimensional model analysis of substorm electrodynamics proceeds from the standard scenario in which the plasma sheet collapses into a neutral sheet, and magnetic merging occurs between the two tail lobes; plasma flows into the neutral sheet from the lobes and the sides, undergoing acceleration in the dawn-dusk direction. The process is modified by the tendency of the accelerated plasma to unbalance charge neutrality, leading to an exchange of electrons with the ionosphere in order to maintain neutrality. The cross-tail current is weakened by the diversion: this reduces the adjacent lobe-field intensity, but without notable effects apart from a slight expansion of the tail boundary.

  14. On a modified electrodynamics

    PubMed Central

    Reiss, H.R.

    2012-01-01

    A modification of electrodynamics is proposed, motivated by previously unremarked paradoxes that can occur in the standard formulation. It is shown by specific examples that gauge transformations exist that radically alter the nature of a problem, even while maintaining the values of many measurable quantities. In one example, a system with energy conservation is transformed to a system where energy is not conserved. The second example possesses a ponderomotive potential in one gauge, but this important measurable quantity does not appear in the gauge-transformed system. A resolution of the paradoxes comes from noting that the change in total action arising from the interaction term in the Lagrangian density cannot always be neglected, contrary to the usual assumption. The problem arises from the information lost by employing an adiabatic cutoff of the field. This is not necessary. Its replacement by a requirement that the total action should not change with a gauge transformation amounts to a supplementary condition for gauge invariance that can be employed to preserve the physical character of the problem. It is shown that the adiabatic cutoff procedure can also be eliminated in the construction of quantum transition amplitudes, thus retaining consistency between the way in which asymptotic conditions are applied in electrodynamics and in quantum mechanics. The ‘gauge-invariant electrodynamics’ of Schwinger is shown to depend on an ansatz equivalent to the condition found here for maintenance of the ponderomotive potential in a gauge transformation. Among the altered viewpoints required by the modified electrodynamics, in addition to the rejection of the adiabatic cutoff, is the recognition that the electric and magnetic fields do not completely determine a physical problem, and that the electromagnetic potentials supply additional information that is required for completeness of electrodynamics. PMID:23105173

  15. Flow around a tethered cylinder, the effect of tether length at high layover angles

    NASA Astrophysics Data System (ADS)

    Ryan, Kris

    2011-07-01

    Tethered cylinder systems constitute a natural extension of the lightly damped, hydro-elastically mounted cylinder. In this case, the cylinder is constrained to travel along an arc prescribed by the tether length. The analysis of the tethered cylinder system is hampered by the dependence of the natural frequency of the system on both the fluid forces acting on the system and the curved motion (which in turn alters the added mass coefficient away from unity). These difficulties have precluded prior studies considering the natural frequency or reduced velocity as a controlling parameter, making direct comparison with the hydro-elastically mounted cylinder system difficult.This investigation considers the case of a tethered cylinder at low Reynolds number (Re=200) for a mass ratio m*=0.2. It notes a local maximum in the amplitude of oscillation when the normalized tether length L*≃2.0, in agreement with prior studies. By instead considering the amplitude of oscillation in a rotational framework, we are able to explain the existence of this peak, and identify two regions of amplitude response, the first region exists for very small tether lengths (L*≲0.3), while the second exists for larger tether lengths. The transition from small tether lengths to large tether lengths exhibits the highest amplitude angular oscillations.Several wake states are also considered for a tethered cylinder which is oscillating about a horizontal mean layover angle. By considering these wake states, coupled with the definition of the natural frequency, an estimate of the added mass coefficient is made. Here we predict that CA≃0.5 for a tether length of L*=1.5. This prediction is based not only on the tether length, but also on the amplitude of oscillation, and hence is Reynolds number dependent.

  16. Tethered body problems and relative motion orbit determination

    NASA Technical Reports Server (NTRS)

    Eades, J. B., Jr.; Wolf, H.

    1972-01-01

    Selected problems dealing with orbiting tethered body systems have been studied. In addition, a relative motion orbit determination program was developed. Results from these tasks are described and discussed. The expected tethered body motions were examined, analytically, to ascertain what influence would be played by the physical parameters of the tether, the gravity gradient and orbit eccentricity. After separating the motion modes these influences were determined; and, subsequently, the effects of oscillations and/or rotations, on tether force, were described. A study was undertaken, by examining tether motions, to see what type of control actions would be needed to accurately place a mass particle at a prescribed position relative to a main vehicle. Other applications for tethers were studied. Principally these were concerned with the producing of low-level gee forces by means of stabilized tether configurations; and, the initiation of free transfer trajectories from tether supported vehicle relative positions.

  17. Selected Tether Applications Cost Model

    NASA Technical Reports Server (NTRS)

    Keeley, Michael G.

    1988-01-01

    Diverse cost-estimating techniques and data combined into single program. Selected Tether Applications Cost Model (STACOM 1.0) is interactive accounting software tool providing means for combining several independent cost-estimating programs into fully-integrated mathematical model capable of assessing costs, analyzing benefits, providing file-handling utilities, and putting out information in text and graphical forms to screen, printer, or plotter. Program based on Lotus 1-2-3, version 2.0. Developed to provide clear, concise traceability and visibility into methodology and rationale for estimating costs and benefits of operations of Space Station tether deployer system.

  18. Tuned mass damping system for a pendulum in gravity and microgravity fields

    NASA Astrophysics Data System (ADS)

    Atour, Farah

    2016-07-01

    An electrodynamic tether is a simple idea, but one with an amazing number of uses. Electrodynamic tether is a long conductor wire that is attached to the satellite, which can act as a generator or motor, from its motion through the earth's magnetic field. And it has the potential to make space travel significantly cheaper. The lack of electrodynamic tether's widespread in common applications can be attributed to the variable Lorentz forces occuring on the tethers, which will cause them to oscillate and may go out of control, de-orbit the satellite and fall to Earth. A tuned mass damper system, for short refered as tilger, is suggested as damper of oscillations of tethers. A system composed of a tuned mass damper and a simple pendulum simulating the tether was therefore constructed. 350 sets of experimental trials were done on the system, while it was installed inside a drop tower capsule resting on the ground, in order to pick four optimum setup experiments that will undergo a series of microgravity experiments at the Bremen Drop Tower in Bremen, Germany. The GJU Bachelor Research students found that the oscillations of the simple pendulum will not be affected by the tilger during the free fall experiment, except if a feedback mechanism is installed between the simple pendulum and the tilger. In this case, the tilger will dampen the simple pendulum oscillations during free fall.

  19. Method and apparatus for advancing tethers

    DOEpatents

    Zollinger, W. Thor

    1998-01-01

    A tether puller for advancing a tether through a channel may include a bellows assembly having a leading end fixedly attached to the tether at a first position and a trailing end fixedly attached to the tether at a second position so that the leading and trailing ends of the bellows assembly are located a substantially fixed distance apart. The bellows assembly includes a plurality of independently inflatable elements each of which may be separately inflated to an extended position and deflated to a retracted position. Each of the independently inflatable elements expands radially and axially upon inflation. An inflation system connected to the independently inflatable elements inflates and deflates selected ones of the independently inflatable elements to cause the bellows assembly to apply a tractive force to the tether and advance it in the channel.

  20. Method and apparatus for advancing tethers

    DOEpatents

    Zollinger, W.T.

    1998-06-02

    A tether puller for advancing a tether through a channel may include a bellows assembly having a leading end fixedly attached to the tether at a first position and a trailing end fixedly attached to the tether at a second position so that the leading and trailing ends of the bellows assembly are located a substantially fixed distance apart. The bellows assembly includes a plurality of independently inflatable elements each of which may be separately inflated to an extended position and deflated to a retracted position. Each of the independently inflatable elements expands radially and axially upon inflation. An inflation system connected to the independently inflatable elements inflates and deflates selected ones of the independently inflatable elements to cause the bellows assembly to apply a tractive force to the tether and advance it in the channel. 9 figs.

  1. The tether inspection and repair experiment (TIRE)

    NASA Technical Reports Server (NTRS)

    Wood, George M.; Loria, Alberto; Harrison, James K.

    1988-01-01

    The successful development and deployment of reusable tethers for space applications will require methods for detecting, locating, and repairing damage to the tether. This requirement becomes especially important whenever the safety of the STS or the Space Station may be diminished or when critical supplies or systems would be lost in the event of a tether failure. A joint NASA/PSN study endeavor has recently been initiated to evaluate and address the problems to be solved for such an undertaking. The objectives of the Tether Inspection and Repair Experiment (TIRE) are to develop instrumentation and repair technology for specific classes of tethers defined as standards, and to demonstrate the technologies in ground-based and in-flight testing on the STS.

  2. Damage inspection and verification of tethers (DIVOT)

    NASA Technical Reports Server (NTRS)

    Howard, George E.; Gray, John; Levi, Alejandro

    1989-01-01

    The feasibility of an optically-based noncontacting Damage Inspection and Verification of Tethers (DIVOT) System has been developed and successfully demonstrated. DIVOT can be used to inspect a tether for micrometeorite-sized damage sites quickly, at tether scanning rates exceeding 1 m/s. The DIVOT system concept is described and the DIVOT experimental setup for demonstrating the system is reviewed. The experiments are described and the results are reported. The establishment of a relationship between damage and optical response is discussed.

  3. Tethering sockets and wrenches

    NASA Technical Reports Server (NTRS)

    Johnson, E. P.

    1990-01-01

    The tethering of sockets and wrenches was accomplished to improve the safety of working over motor segments. To accomplish the tethering of the sockets to the ratchets, a special design was implemented in which a groove was machined into each socket. Each socket was then fitted with a snap ring that can spin around the machined groove. The snap ring is tethered to the handle of the ratchet. All open end wrenches are also tethered to the ratchet or to the operator, depending upon the type. Tests were run to ensure that the modified tools meet torque requirements. The design was subsequently approved by Space Safety.

  4. Space Tethers Programmatic Infusion Opportunities

    NASA Technical Reports Server (NTRS)

    Bonometti, J. A.; Frame, K. L.

    2005-01-01

    Programmatic opportunities abound for space Cables, Stringers and Tethers, justified by the tremendous performance advantages that these technologies offer and the rather wide gaps that must be filled by the NASA Exploration program, if the "sustainability goal" is to be met. A definition and characterization of the three categories are presented along with examples. A logical review of exploration requirements shows how each class can be infused throughout the program, from small experimental efforts to large system deployments. The economics of tethers in transportation is considered along with the impact of stringers for structural members. There is an array of synergistic methodologies that interlace their fabrication, implementation and operations. Cables, stringers and tethers can enhance a wide range of other space systems and technologies, including power storage, formation flying, instrumentation, docking mechanisms and long-life space components. The existing tether (i.e., MXER) program's accomplishments are considered consistent with NASA's new vision and can readily conform to requirements-driven technology development.

  5. Propulsive Small Expendable Deployer System (ProSEDS)

    NASA Technical Reports Server (NTRS)

    Ballance, Judy; Johnson, Les; Rogacki, John R. (Technical Monitor)

    2000-01-01

    The Propulsive Small Expendable Deployer System (ProSEDS) space experiment will demonstrate the use of an electrodynamic tether propulsion system to generate thrust in space by decreasing the orbital altitude of a Delta II Expendable Launch Vehicle (ELV) second stage. ProSEDS, which is planned to fly in 2001, will use the flight proven Small Expendable Deployer System (SEDS) to deploy a tether (5km bare wire plus 10 km spectra or dyneema) from a Delta II second stage to achieve approximately 0.4N drag thrust. ProSEDS will utilize the tether-generated current to provide limited spacecraft power. The ProSEDs instrumentation includes a Langmuir probe and Differential Ion Flux Probe, which will determine the characteristics of the ambient ionospheric plasma. Two Global Positioning System (GPS) receivers will be used (one on the Delta and one on the endmass) to help determine tether dynamics and to limit transmitter operations to occasions when the spacecraft is over selected ground stations, The flight experiment is a precursor to the more ambitious electrodynamic tether upper stage demonstration mission, which will be capable of orbit raising, lowering and inclination changes-all using electrodynamic thrust. An immediate application of ProSEDS technology is for the deorbit of spent satellites for orbital debris mitigation. In addition to the use of this technology to provide orbit transfer and debris mitigation it may also be an attractive option for future missions to Jupiter and any other planetary body with a magnetosphere.

  6. Tethered Space Satellite-1 (TSS-1): Wound About a Bolt

    NASA Technical Reports Server (NTRS)

    O'Connor, Brian; Stevens, Jennifer

    2016-01-01

    In the early 1990's US and Italian scientists collaborated to study the electrodynamics on a long tether between two satellites as it moved through the electrically charged portion of Earth's atmosphere called the ionosphere. Potential uses for the electrical current induced in the long wire include power and thrust generation for a satellite, momentum exchange, artificial gravity, deployment of sensors or antennas, and gravity-gradient stabilization. The Tethered Space Satellite (TSS) was a first-of-its-kind experiment with long tethers in space. It consisted of a satellite with science experiments attached to a 12.5 mile long, very thin (0.10 inch diameter) copper wire assembly wound around a spool in the deployer reel mechanism. The whole mechanism sits on a pallet that is installed into the Shuttle bay. At an altitude of 160 nautical miles above earth, the satellite would be deplodeployed from the Shuttle bay by raising it on a boom facing away from Earth. Once cleared of the bay, the deployer mechanism would slowly feed out the 12-plus miles of tether. Scientific data would be collected throughout the operation, after which the satellite would be reeled back in. A receiver spool to catch the 12.5 mile tether as it was being unwound by the deployer reel mechanism was set up to do the system-level test of deployer real mechanism prior to installing the loaded pallet into the Shuttle bay. The system level tests were required before the pallet could be installed into the Space Shuttle cargo bay. A few months before flight, the system level tests, including unreeling and reeling the tether, were completed at Kennedy Space Center (KSC) and the TSS payload was installed onto the Spacelab pallet. Some of this testing equipment was then shipped back to the contractor, Martin Marietta. Integration with the Shuttle began. Systems-level load analyses, which cannot be run until all information about each payload is finalized, was run in parallel with the physical

  7. Galilean limit of electrodynamics.

    NASA Astrophysics Data System (ADS)

    Reula, O. A.; Hamity, V. H.; Frittelli, S.

    The final interest of the authors' work is to study the Newtonian limit as an approximation to General Relativity. In this paper they show, using the Galilean limit of electrodynamics with external sources as a test model, some of the problems that they will be confronted with, and the techniques that are introduced to attack them. The crucial physical issue, to define an asymptotic expansion of a class of solutions, is the selection of initial data which results of imposing regularity conditions in the nonrelativistic limit. The authors' model is an example of a more general class of systems which includes, hopefully, the gravitational field plus matter.

  8. Limits on nonlinear electrodynamics

    NASA Astrophysics Data System (ADS)

    Fouché, M.; Battesti, R.; Rizzo, C.

    2016-05-01

    In this paper we set a framework in which experiments whose goal is to test QED predictions can be used in a more general way to test nonlinear electrodynamics (NLED) which contains low-energy QED as a special case. We review some of these experiments and we establish limits on the different free parameters by generalizing QED predictions in the framework of NLED. We finally discuss the implications of these limits on bound systems and isolated charged particles for which QED has been widely and successfully tested.

  9. An optical telemetry system for underwater recording of electromyogram and neuronal activity from non-tethered crayfish.

    PubMed

    Tsuchida, Yoshikazu; Hama, Noriyuki; Takahata, Masakazu

    2004-08-15

    We have developed an optical telemetry system for recording electrical signals associated with muscle and neuronal activities from freely walking crayfish under water. The device was made from conventional electronic parts which are commercially available, utilizing infrared light (880 nm) for signal transmission. Two or four channels of biological signals were multiplexed, the voltage of each data point modulated to the duration of subcarrier pulses and further to the interval of narrower carrier pulses that directly drove the infrared light emission diode (IRLED) under water. The light-pulse modulated signals were received by photodiodes and demodulated to restore the original two or four channel signals. Electrical recordings using wired electrodes and conventional amplifiers revealed that the optically transmitted signals were consistent with the wire-transmitted ones. In order to test the performance of this system, we recorded electromyograms (EMGs) from the second and third walking legs on each side of crayfish together with the neuronal activity in the ventral nerve cord. The results confirmed our previous observation in tethered crayfish that the background tonus of leg muscles showed an increase preceding their rhythmic activation. PMID:15196832

  10. Precision attitude control for tethered satellites

    NASA Technical Reports Server (NTRS)

    Kline-Schoder, Robert J.; Powell, J. D.

    1993-01-01

    Tethered spacecraft are particularly well suited to serve as isolation platforms for space-borne observatories. It has previously been shown that, due to the relatively large tether force, conventional means of performing attitude control for tethered satellites are inefficient for any mission with pointing requirements more stringent than about 1 deg. A particularly effective method of implementing attitude control for tethered satellites is to use the tether tension force to generate control moments by moving the tether attach point relative to the subsatellite center of mass. This paper presents the development of a precision pointing control algorithm for tethered satellites and the simulation of the control system with laboratory hardware. The control algorithm consists of a linear quadratic regulator feedback law and a Kalman filter. The control algorithm has been shown to regulate the vehicle orientation to within 0.60 arcsec rms. This level of precision was achieved only after including a mass center estimator and accurately modeling the effects of the nonlinear attach point motion actuator.

  11. Quantization of general linear electrodynamics

    SciTech Connect

    Rivera, Sergio; Schuller, Frederic P.

    2011-03-15

    General linear electrodynamics allow for an arbitrary linear constitutive relation between the field strength 2-form and induction 2-form density if crucial hyperbolicity and energy conditions are satisfied, which render the theory predictive and physically interpretable. Taking into account the higher-order polynomial dispersion relation and associated causal structure of general linear electrodynamics, we carefully develop its Hamiltonian formulation from first principles. Canonical quantization of the resulting constrained system then results in a quantum vacuum which is sensitive to the constitutive tensor of the classical theory. As an application we calculate the Casimir effect in a birefringent linear optical medium.

  12. Development of a tethered satellite force transducer

    NASA Astrophysics Data System (ADS)

    Rhew, Ray D.

    The SEDS (Small Expendable Deployer System)/Delta II is a demonstration flight of a tethered satellite deployer system. The satellite or end mass payload, which is deployed and tethered to the Delta II rocket, is instrumented to determine its dynamics during deployment. A three-component force transducer or strain-gage balance was developed to measure tether tension on the end-mass side of the tether. The transducer was designed to measure tensions up to 20N in each direction and resolve tensions as low as 0.002N. In addition, the transducer was required to withstand the shock, vibration, and temperature excursions of the mission. The development of the transducer from design to testing and integration is discussed.

  13. Theoretical investigation of the generation and injection of electromagnetic waves in space plasma by means of a long-orbiting tether

    NASA Technical Reports Server (NTRS)

    Dobrowolny, M.

    1981-01-01

    Analysis of the various mechanisms of electromagnetic wave generation by the shuttle-borne orbiting tether of the T.S.S. Facility shows that significant electrodynamic power levels are available even when overestimating the loss mechanisms expected to intervene. This electrodynamic power is in part dissipated by Joule losses in the tether, in part goes to accelerate electrons through the sheath surrounding the balloon (when in a downward deployment), and in part goes into e.m. wave generation. A preliminary estimate shows that a 100 km tether in orbit would produce ULF/ELF signals that are detectable on the ground with state-of-the-art magnetometric instrumentation.

  14. Morpheus Tether Test #22

    NASA Video Gallery

    Morpheus conducts another tethered test, June 6, 2013. Morpheus is a full spacecraft and rocket-powered lander, which demonstrates new green technology, as well as an autonomous landing and hazard ...

  15. Morpheus Tether Test #14

    NASA Video Gallery

    Morpheus conducts another tethered test, May 8, 2012. Morpheus is a full spacecraft and rocket-powered lander, which demonstrates new green technology, as well as an autonomous landing and hazard d...

  16. Morpheus Tether Test #9

    NASA Video Gallery

    Morpheus conducts another tethered test, March 16, 2012. Morpheus is a full spacecraft and rocket-powered lander, which demonstrates new green technology, as well as an autonomous landing and hazar...

  17. Morpheus Tether Test #12

    NASA Video Gallery

    Morpheus conducts another tethered test, April 18, 2012. Morpheus is a full spacecraft and rocket-powered lander, which demonstrates new green technology, as well as an autonomous landing and hazar...

  18. Morpheus Tether Test #13

    NASA Video Gallery

    Morpheus conducts another tethered test, May 2, 2012. Morpheus is a full spacecraft and rocket-powered lander, which demonstrates new green technology, as well as an autonomous landing and hazard d...

  19. Morpheus Tether Test #10

    NASA Video Gallery

    Morpheus conducts another tethered test, April 5, 2012. Morpheus is a full spacecraft and rocket-powered lander, which demonstrates new green technology, as well as an autonomous landing and hazard...

  20. Morpheus Tether Test #11

    NASA Video Gallery

    Morpheus conducts another tethered test, April 11, 2012. Morpheus is a full spacecraft and rocket-powered lander, which demonstrates new green technology, as well as an autonomous landing and hazar...

  1. Tether Deployer And Brake

    NASA Technical Reports Server (NTRS)

    Carroll, Joseph A.; Alexander, Charles M.

    1993-01-01

    Design concept promises speed, control, and reliability. Scheme for deploying tether provides for fast, free, and snagless payout and fast, dependable braking. Developed for small, expendable tethers in outer space, scheme also useful in laying transoceanic cables, deploying guidance wires to torpedoes and missiles, paying out rescue lines from ship to ship via rockets, deploying antenna wires, releasing communication and power cables to sonobuoys and expendable bathythermographs, and in reeling out lines from fishing rods.

  2. Remarks on nonlinear electrodynamics

    NASA Astrophysics Data System (ADS)

    Gaete, Patricio; Helayël-Neto, José

    2014-11-01

    We consider both generalized Born-Infeld and exponential electrodynamics. The field energy of a point-like charge is finite only for Born-Infeld-like electrodynamics. However, both Born-Infeld-type and exponential electrodynamics display the vacuum birefringence phenomenon. Subsequently, we calculate the lowest-order modifications to the interaction energy for both classes of electrodynamics, within the framework of the gauge-invariant path-dependent variables formalism. These are shown to result in long-range (-type) corrections to the Coulomb potential. Once again, for their noncommutative versions, the interaction energy is ultraviolet finite.

  3. Artificial Gravity: Tethers and Containers

    NASA Technical Reports Server (NTRS)

    Criswell, D. R.

    1985-01-01

    Tethers used in conjunction with containers offer a means of enhanced control of basic variables such as local acceleration, pointing and orientation, and protected or controlled environments against particle or electromagnetic radiation. Permanent occupancy of space will require the rapid exploration of the short and long term responses of many living organisms to the space environment or separated components of that environment. Tethers and ET facilities could provide the rapid establishment of laboratories in LEO within which to study living systems in a wide range of separate controlled environments for long periods of time, support large optical arrays; provide orbiting laboratories; and provide controlled environments within which the application of advanced manufacturing, assembly, control, and robotics could be developed to aid off-Earth industry and science and the conduct of more complex space operations.

  4. TSS tether cable meteoroid/orbital debris damage analysis

    NASA Technical Reports Server (NTRS)

    Hayashida, K. B.; Robinson, J. H.

    1993-01-01

    This report summarizes the damage analyses performed on the tether cable used for the tethered satellite system (TSS), for the damage that could be caused by meteoroid or orbital debris impacts. The TSS consists of a tethered satellite deployer and a tethered satellite. The analytical studies were performed at Marshall Space Flight Center (MSFC) with the results from the following tests: (1) hypervelocity impact tests to determine the 'critical' meteoroid particle diameter, i.e., the maximum size of a meteoroid particle which can impact the tether cable without causing 'failure'; (2) electrical resistance tests on the damaged and undamaged tether cable to determine if degradation of current flow occurred through the damaged tether cables; and (3) tensile load tests to verify the load carrying capability of the damaged tether cables. Finally, the HULL hydrodynamic computer code was used to simulate the hypervelocity impact of the tether cable by particles at velocities higher than can be tested, to determine the extent of the expected tether damage.

  5. Research on the tether assisted observation of an asteroid

    NASA Astrophysics Data System (ADS)

    Zhong, Rui; Wang, Yue

    2016-06-01

    The exploration of asteroids attracts much attention due to its potential in both scientific research and engineering application. However, the observation of an asteroid is a difficult task as the gravitational attraction of the asteroid is limited and complex. This paper proposes a concept of keeping probes in hovering above the asteroid by space tethers. The dynamics of a tethered probe attached to the surface of an asteroid is analyzed and the equations of motion are derived using Lagrange's equation. Then the equilibrium points of the dynamic system are calculated. The equilibrium tether libration angles are determined by the tether length and tether attaching location, while subjected to the constraint of positive tether tension. Afterwards, the stability of the equilibrium points are studied based on Lyapunov's theory. The variation of the equilibrium points with respect to the tether attaching location is numerically analyzed in the scenarios of different tether lengths. A parametric study of the stability of the equilibrium points is also provided. Finally, the dynamic behavior of a tethered probe perturbed from the equilibrium states is simulated to verify the proposed tether assisted technology for the observation of the asteroid.

  6. Formation Flying of Tethered and Nontethered Spacecraft

    NASA Technical Reports Server (NTRS)

    Quadrelli, Marco B.

    2005-01-01

    A paper discusses the effect of the dynamic interaction taking place within a formation composed of a rigid and a deformable vehicle, and presents the concept of two or more tethered spacecraft flying in formation with one or more separated free-flying spacecraft. Although progress toward formation flight of nontethered spacecraft has already been achieved, the document cites potential advantages of tethering, including less consumption of fuel to maintain formation, very high dynamic stability of a rotating tethered formation, and intrinsically passive gravity-gradient stabilization. The document presents a theoretical analysis of the dynamics of a system comprising one free-flying spacecraft and two tethered spacecraft in orbit, as a prototype of more complex systems. The spacecraft are modeled as rigid bodies and the tether as a mass-less spring with structural viscous damping. Included in the analysis is a study of the feasibility of a centralized control system for maintaining a required formation in low Earth orbit. A numerical simulation of a retargeting maneuver is reported to show that even if the additional internal dynamics of the system caused by flexibility is considered, high pointing precision can be achieved if a fictitious rigid frame is used to track the tethered system, and it should be possible to position the spacecraft with centimeter accuracy and to orient the formation within arc seconds of the desired direction also in the presence of low Earth orbit environmental perturbations. The results of the study demonstrate that the concept is feasible in Earth orbit and point the way to further study of these hybrid tethered and free-flying systems for related applications in orbit around other Solar System bodies.

  7. Tethers in Space Handbook

    NASA Technical Reports Server (NTRS)

    Cosmo, M. L. (Editor); Lorenzini, E. C. (Editor)

    1997-01-01

    A new edition of the Tethers in Space Handbook was needed after the last edition published in 1989. Tether-related activities have been quite busy in the 90's. We have had the flights of TSSI and TSSI-R, SEDS-1 and -2, PMG, TIPS and OEDIPUS. In less than three years there have been one international Conference on Tethers in Space, held in Washington DC, and three workshops, held at ESA/Estec in the Netherlands, at ISAS in Japan and at the University of Michigan, Ann Harbor. The community has grown and we finally have real flight data to compare our models with. The life of spaceborne tethers has not been always easy and we got our dose of setbacks, but we feel pretty optimistic for the future. We are just stepping out of the pioneering stage to start to use tethers for space science and technological applications. As we are writing this handbook TiPs, a NRL tether project is flying above our heads. There is no emphasis in affirming that as of today spacebome tethers are a reality and their potential is far from being fully appreciated. Consequently, a large amount of new information had to be incorporated into this new edition. The general structure of the handbook has been left mostly unchanged. The past editors have set a style which we have not felt needed change. The section on the flights has been enriched with information on the scientific results. The categories of the applications have not been modified, and in some cases we have mentioned the existence of related flight data. We felt that the section contributed by Joe Carroll, called Tether Data, should be maintained as it was, being a "classic" and still very accurate and not at all obsolete. We have introduced a new chapter entitled Space Science and Tethers since flight experience has shown that tethers can complement other space-based investigations. The bibliography has been updated. Due to the great production in the last few years %e had to restrict our search to works published in refereed journal

  8. Phase 3 study of selected tether applications in space, mid-term review

    NASA Technical Reports Server (NTRS)

    1986-01-01

    Topics addressed include: guidelines for the Space Transportation System (STS) payload deployer design; mini-orbital maneuvering vehicle (MOMV) design: shuttle tether deployer systems (STEDS); cost modeling; tethered platform analysis; fuel savings analysis; and STEDS control simulation.

  9. Cavity quantum electrodynamics using a near-resonance two-level system: Emergence of the Glauber state

    SciTech Connect

    Sarabi, B.; Ramanayaka, A. N.; Burin, A. L.; Wellstood, F. C.; Osborn, K. D.

    2015-04-27

    Random tunneling two-level systems (TLSs) in dielectrics have been of interest recently because they adversely affect the performance of superconducting qubits. The coupling of TLSs to qubits has allowed individual TLS characterization, which has previously been limited to TLSs within (thin) Josephson tunneling barriers made from aluminum oxide. Here, we report on the measurement of an individual TLS within the capacitor of a lumped-element LC microwave resonator, which forms a cavity quantum electrodynamics (CQED) system and allows for individual TLS characterization in a different structure and material than demonstrated with qubits. Due to the reduced volume of the dielectric (80 μm{sup 3}), even with a moderate dielectric thickness (250 nm), we achieve the strong coupling regime as evidenced by the vacuum Rabi splitting observed in the cavity spectrum. A TLS with a coherence time of 3.2 μs was observed in a film of silicon nitride as analyzed with a Jaynes-Cummings spectral model, which is larger than seen from superconducting qubits. As the drive power is increased, we observe an unusual but explicable set of continuous and discrete crossovers from the vacuum Rabi split transitions to the Glauber (coherent) state.

  10. Cavity quantum electrodynamics using a near-resonance two-level system: Emergence of the Glauber state

    NASA Astrophysics Data System (ADS)

    Sarabi, B.; Ramanayaka, A. N.; Burin, A. L.; Wellstood, F. C.; Osborn, K. D.

    2015-04-01

    Random tunneling two-level systems (TLSs) in dielectrics have been of interest recently because they adversely affect the performance of superconducting qubits. The coupling of TLSs to qubits has allowed individual TLS characterization, which has previously been limited to TLSs within (thin) Josephson tunneling barriers made from aluminum oxide. Here, we report on the measurement of an individual TLS within the capacitor of a lumped-element LC microwave resonator, which forms a cavity quantum electrodynamics (CQED) system and allows for individual TLS characterization in a different structure and material than demonstrated with qubits. Due to the reduced volume of the dielectric (80 μm3), even with a moderate dielectric thickness (250 nm), we achieve the strong coupling regime as evidenced by the vacuum Rabi splitting observed in the cavity spectrum. A TLS with a coherence time of 3.2 μs was observed in a film of silicon nitride as analyzed with a Jaynes-Cummings spectral model, which is larger than seen from superconducting qubits. As the drive power is increased, we observe an unusual but explicable set of continuous and discrete crossovers from the vacuum Rabi split transitions to the Glauber (coherent) state.

  11. System noise analysis of the dumbbell tethered satellite for gravity-gradient measurements

    NASA Technical Reports Server (NTRS)

    Colombo, G.

    1979-01-01

    An analysis of the dumbbell gravity gradiometer concept for measuring short wavelength variations in the earth's gravity gradient is presented. Variations in the gradient are recorded by measuring tension variations in a vertically stabilized satellite consisting of heavy masses connected by a long wire or rod. Tension noise arises from the excitation of various mechanical oscillations of the system. The principal noise sources that were identified are fluctuations in atmospheric drag heating and drag force resulting from density variations and winds. Approximate analytical expressions are presented for the tension noise as a function of the system design parameters for various possible configurations. Computer simulations using numerical integration were performed to study the tension noise for several sample cases. Three designs consistent with Shuttle launch capabilities are discussed.

  12. Tethered to work: A family systems approach linking mobile device use to turnover intentions.

    PubMed

    Ferguson, Merideth; Carlson, Dawn; Boswell, Wendy; Whitten, Dwayne; Butts, Marcus M; Kacmar, K Michele Micki

    2016-04-01

    We examined the use of a mobile device for work during family time (mWork) to determine the role that it plays in employee turnover intentions. Using a sample of 344 job incumbents and their spouses, we propose a family systems model of turnover and examine 2 paths through which we expect mWork to relate to turnover intentions: the job incumbent and the spouse. From the job incumbent, we found that the job incumbent's mWork associated with greater work-to-family conflict and burnout, and lower organizational commitment. From the spouse, we found that incumbent mWork and greater work-to-family conflict associated with increased resentment by the spouse and lower spousal commitment to the job incumbent's organization. Both of these paths played a role in predicting job incumbent turnover intentions. We discuss implications and opportunities for future research on mWork for integrating work and family into employee turnover intentions. PMID:26653530

  13. Connection system. [insuring against loss of a tool component without using multiple tethers

    NASA Technical Reports Server (NTRS)

    Mccandless, B., II (Inventor)

    1984-01-01

    A mechanical connection system comprises a first body defining a receptable and a second body defining a pin matingly receivable in the receptacle by relative movement in a first directional mode. A primary latch is engagable between the two bodies to retain the pin in the receptacle. The primary latch is reciprocable in a second directional mode transverse to the first directional mode. A lock member carried by one of the bodies is operatively associated with the primary latch and movable, transverse to the second directional mode, between a locking position maintaining engagement of the primary latch and a releasing position permitting release of the primary latch. The lock includes an operator portion engagable to move the lock member from its locking position to its releasing position. The operator is located internally of the first body. An actuator is selectivity insertable into and disengagable from the first body. The actuator is movable relative to the first body when it is inserted for engagement with and operation of the operator.

  14. Plasma contactors for use with electodynamic tethers for power generation

    NASA Technical Reports Server (NTRS)

    Hastings, D. E.; Gatsonis, N. A.

    1988-01-01

    Plasma contactors are proposed as a means of making good electrical contact between biased surfaces such as found at the ends of an electrodynamic tether and the space environment. The plasma contactor emits a plasma cloud which facilitates the electrical connection. The physics of this plasma cloud is investigated for contactors used as electron collectors. The central question addressed is whether the electrons collected by a plasma contactor come from the far field or by ionization of local neutral gas. This question is important because the system implications are different for the two mechanisms. It is shown that contactor clouds in space will consist of a spherical core possibly containing a shock wave. Outside of the core the cloud will expand anisotropically across the magnetic field leading to a turbulent cigar shape structure along the field. This outer region is itself divided into two regions by the ion response to the electric field. A two-dimensional theory for the outer regions of the cloud is developed. The current voltage characteristic of an Argon plasma contactor cloud is estimated for several ion currents in the range of 1 to 100 Amperes. It is suggested that the major source of collected electrons comes by ionization of neutral gas while collection of electrons from the far field is relatively small.

  15. Tethered orbital refueling study

    NASA Technical Reports Server (NTRS)

    Fester, Dale A.; Rudolph, L. Kevin; Kiefel, Erlinda R.; Abbott, Peter W.; Grossrode, Pat

    1986-01-01

    One of the major applications of the space station will be to act as a refueling depot for cryogenic-fueled space-based orbital transfer vehicles (OTV), Earth-storable fueled orbit maneuvering vehicles, and refurbishable satellite spacecraft using hydrazine. One alternative for fuel storage at the space station is a tethered orbital refueling facility (TORF), separated from the space station by a sufficient distance to induce a gravity gradient force that settles the stored fuels. The technical feasibility was examined with the primary focus on the refueling of LO2/LH2 orbital transfer vehicles. Also examined was the tethered facility on the space station. It was compared to a zero-gravity facility. A tethered refueling facility should be considered as a viable alternative to a zero-gravity facility if the zero-gravity fluid transfer technology, such as the propellant management device and no vent fill, proves to be difficult to develop with the required performance.

  16. Tether Dynamics Simulation

    NASA Technical Reports Server (NTRS)

    1987-01-01

    The proceedings of the conference are presented. The objective was to provide a forum for the discussion of the structure and status of existing computer programs which are used to simulate the dynamics of a variety of tether applications in space. A major topic was different simulation models and the process of validating them. Guidance on future work in these areas was obtained from a panel discussion; the panel was composed of resource and technical managers and dynamic analysts in the tether field. The conclusions of this panel are also presented.

  17. SEDS Tether M/OD Damage Analyses

    NASA Technical Reports Server (NTRS)

    Hayashida, K. B.; Robinson, J. H.; Hill, S. A.

    1997-01-01

    The Small Expendable Deployer System (SEDS) was designed to deploy an endmass at the end of a 20-km-long tether which acts as an upper stage rocket, and the threats from the meteoroid and orbital debris (M/OD) particle environments on SEDS components are important issues for the safety and success of any SEDS mission. However, the possibility of severing the tether due to M/OD particle impacts is an even more serious concern, since the SEDS tether has a relatively large exposed area to the M/OD environments although its diameter is quite small. The threats from the M/OD environments became a very important issue for the third SEDS mission, since the project office proposed using the shuttle orbiter as a launch platform instead of the second stage of a Delta II expendable rocket, which was used for the first two SEDS missions. A series of hyper-velocity impact tests were performed at the Johnson Space Center and Arnold Engineering Development Center to help determine the critical particle sizes required to sever the tether. The computer hydrodynamic code or hydrocode called CTH, developed by the Sandia National Laboratories, was also used to simulate the damage on the SEDS tether caused by both the orbital debris and test particle impacts. The CTH hydrocode simulation results provided the much needed information to help determine the critical particle sizes required to sever the tether. The M/OD particle sizes required to sever the tether were estimated to be less than 0.1 cm in diameter from these studies, and these size particles are more abundant in low-Earth orbit than larger size particles. Finally, the authors performed the M/OD damage analyses for the three SEDS missions; i.e., SEDS-1, -2, and -3 missions, by using the information obtained from the hypervelocity impact test and hydrocode simulations results.

  18. Astronaut James Newman evaluates tether devices in Discovery's payload bay

    NASA Technical Reports Server (NTRS)

    1993-01-01

    Astronaut James H. Newman, mission specialist, evaluates various tether devices to be used during the Hubble Space Telescope (HST) servicing mission scheduled for later this year. Newman is tethered to the starboard side, with the orbital maneuvering system (OMS) pod just behind him.

  19. Galilean Podolsky Electrodynamics

    NASA Astrophysics Data System (ADS)

    Pompeia, P. J.; de Montigny, M.; Khanna, F. C.

    2009-09-01

    We analyze non-relativistic limits of Podolsky generalized electrodynamics in the context of the 5-dimensional Galilean formalism. The 'electric' and 'magnetic' limits are studied in analogy with the work of Le Bellac and Levy-Leblond (1973).

  20. Ionospheric Multi-Point Measurements Using Tethered Satellite Sensors

    NASA Technical Reports Server (NTRS)

    Gilchrist, B. E.; Heelis, R. A.; Raitt, W. J.

    1998-01-01

    Many scientific questions concerning the distribution of electromagnetic fields and plasma structures in the ionosphere require measurements over relatively small temporal and spatial scales with as little ambiguity as possible. It is also often necessary to differentiate several geophysical parameters between horizontal and vertical gradients unambiguously. The availability of multiple tethered satellites or sensors, so-called "pearls-on-a-string," may make the necessary measurements practical. In this report we provide two examples of scientific questions which could benefit from such measurements (1) high-latitude magnetospheric-ionospheric coupling; and, (2) plasma structure impact on large and small-scale electrodynamics. Space tether state-of-the-art and special technical considerations addressing mission lifetime, sensor pointing, and multi-stream telemetry are reviewed.

  1. Coordinated coupling control of tethered space robot using releasing characteristics of space tether

    NASA Astrophysics Data System (ADS)

    Huang, Panfeng; Zhang, Fan; Xu, Xiudong; Meng, Zhongjie; Liu, Zhengxiong; Hu, Yongxin

    2016-04-01

    Tethered space robot (TSR) is a new concept of space robot, which is released from the platform satellite, and retrieved via connected tether after space debris capture. In this paper, we propose a new coordinate control scheme for optimal trajectory and attitude tracking, and use releasing motor torque to instead the tension force, since it is difficult to track in practical. Firstly, the 6-DOF dynamics model of TSR is derived, in which the dynamics of tether releasing system is taken into account. Then, we propose and design the coordinated coupled controller, which is composed of a 6-DOF sliding mode controller and a PD controller tether's releasing. Thrust is treated as control input of the 6-DOF sliding mode controller to control the in-plane and out-of-plane angle of the tether and attitude angles of the TSR. The torque of releasing motor is used as input of PD controller, which controls the length rate of space tether. After the verification of the control scheme, finally, the simulation experiment is presented in order to validate the effectiveness of this control method. The results show that TSR can track the optimal approaching trajectory accurately. Simultaneously, the attitude angles can be changed to the desired attitude angles in control period, and the terminal accuracy is ±0.3°.

  2. Input profile for satellite orbit transfer by tether mechanism; Part I: Tether length profile using feed-forward procedure

    NASA Astrophysics Data System (ADS)

    Hokamoto, Shinji

    This study deals with orbital transfer of a satellite using a tether extension / retrieval mechanism. Instead of using propellant for the orbital transfer, the present concept uses electrical energy. By controlling the pitch motion of the tether system, we can achieve a prescribed velocity of the satellite at a prescribed position. By cutting the tether at that instant, we can inject the satellite into a designed new orbit. This paper considers co-planar motion and proposes a technique to achieve the desired tether length, pitch angle, and pitch angular rate at a designated position in orbit by using only tether length control. These three state variables are adjusted to their target values in three consecutive sections in the orbit; 1) control for the angular momentum of the pitching motion, which implies to adjust the tether length, 2) control for the pitch angle, and 3) control for the pitch angular rate. In each section, a pitch acceleration profile can be formed by using Fourier series as an alternative input for tether length profile. Their coefficients can be obtained without numerical iterations by using the simple initial / final relationships for the pitch angle and pitch angular rate. Therefore, this proposed procedure requires less computational cost than a numerical search, is easily applicable for different models and orbits, and can cope with physical restrictions of the system, such as tether tension or maximum tether length. Furthermore, the resulting final states precisely coincide with the target values. To demonstrate that the proposed procedure can successfully generate proper input profiles, this paper presents an orbital transfer problem as an example, and verifies its effectiveness. The simulation results show that the maximum tether length is less than 5km, and that the tether tension is kept positive during the mission.

  3. Fortissimo: A Japanese Space Test Of Bare Wire Anode Tethers

    NASA Technical Reports Server (NTRS)

    Johnson, Les; Fujii, H. A.; Sanmartin, J. R.

    2008-01-01

    A Japanese led international team is developing a suborbital test of orbital-motion-limited (OML) bare wire anode current collection for application to electrodynamic tether (EDT) propulsion. The tether is a tape with a width of 25 mm, thickness of 0.05 mm, and is 300 m in length. This will be the first space test of OML theory. The mission will launch in the summer of 2009 using an S520 Sounding Rocket. During ascent, and above approx. 100 km in attitude, the tape tether will be deployed at a rate of approx. 8 m/s. Once deployed, the tape tether will serve as an anode, collecting ionospheric electrons. The electrons will be expelled into space by a hollow cathode device, thereby completing the circuit and allowing current to flow. The total amount of current collected will be used to assess the validity of OML theory. This paper will describe the objectives of the proposed mission, the technologies to be employed, and the application of the results to future space missions using EDTs for propulsion or power generation.

  4. Electrodynamics on extrasolar giant planets

    SciTech Connect

    Koskinen, T. T.; Yelle, R. V.; Lavvas, P.; Cho, J. Y-K.

    2014-11-20

    Strong ionization on close-in extrasolar giant planets (EGPs) suggests that their atmospheres may be affected by ion drag and resistive heating arising from wind-driven electrodynamics. Recent models of ion drag on these planets, however, are based on thermal ionization only and do not include the upper atmosphere above the 1 mbar level. These models are also based on simplified equations of resistive magnetohydrodynamics that are not always valid in extrasolar planet atmospheres. We show that photoionization dominates over thermal ionization over much of the dayside atmosphere above the 100 mbar level, creating an upper ionosphere dominated by ionization of H and He and a lower ionosphere dominated by ionization of metals such as Na, K, and Mg. The resulting dayside electron densities on close-in exoplanets are higher than those encountered in any planetary ionosphere of the solar system, and the conductivities are comparable to the chromosphere of the Sun. Based on these results and assumed magnetic fields, we constrain the conductivity regimes on close-in EGPs and use a generalized Ohm's law to study the basic effects of electrodynamics in their atmospheres. We find that ion drag is important above the 10 mbar level where it can also significantly alter the energy balance through resistive heating. Due to frequent collisions of the electrons and ions with the neutral atmosphere, however, ion drag is largely negligible in the lower atmosphere below the 10 mbar level for a reasonable range of planetary magnetic moments. We find that the atmospheric conductivity decreases by several orders of magnitude in the night side of tidally locked planets, leading to a potentially interesting large-scale dichotomy in electrodynamics between the day and night sides. A combined approach that relies on UV observations of the upper atmosphere, phase curve and Doppler measurements of global dynamics, and visual transit observations to probe the alkali metals can potentially be

  5. Recurrent Delocalization and Quasiequilibration of Photons in Coupled Systems in Circuit Quantum Electrodynamics

    NASA Astrophysics Data System (ADS)

    Hwang, Myung-Joong; Kim, M. S.; Choi, Mahn-Soo

    2016-04-01

    We explore the photon population dynamics in two coupled circuit QED systems. For a sufficiently weak intercavity photon hopping, as the photon-cavity coupling increases, the dynamics undergoes double transitions first from a delocalized to a localized phase and then from the localized to another delocalized phase. The latter delocalized phase is distinguished from the former one; instead of oscillating between the two cavities, the photons rapidly quasiequilibrate over the two cavities. These intriguing features are attributed to an interplay between two qualitatively distinctive nonlinear behaviors of the circuit QED systems in the utrastrong coupling regime, whose distinction has been widely overlooked.

  6. Recurrent Delocalization and Quasiequilibration of Photons in Coupled Systems in Circuit Quantum Electrodynamics.

    PubMed

    Hwang, Myung-Joong; Kim, M S; Choi, Mahn-Soo

    2016-04-15

    We explore the photon population dynamics in two coupled circuit QED systems. For a sufficiently weak intercavity photon hopping, as the photon-cavity coupling increases, the dynamics undergoes double transitions first from a delocalized to a localized phase and then from the localized to another delocalized phase. The latter delocalized phase is distinguished from the former one; instead of oscillating between the two cavities, the photons rapidly quasiequilibrate over the two cavities. These intriguing features are attributed to an interplay between two qualitatively distinctive nonlinear behaviors of the circuit QED systems in the utrastrong coupling regime, whose distinction has been widely overlooked. PMID:27127967

  7. Experiments with Electrodynamic Wheels

    NASA Astrophysics Data System (ADS)

    Gaul, Nathan; Corey, Daniel; Cordrey, Vincent; Majewski, Walerian

    2015-04-01

    Our experiments were involving inductive magnetic levitation. A Halbach array is a system in which a series of magnets is arranged in a manner such that the magnetic field is cancelled on one side of the array while strengthening the field on the other. We constructed two circular Halbach wheels, making the strong magnetic field on the outer rim of the ring. Such system is usually dubbed as an Electrodynamic Wheel (EDW). Rotating this wheel around a horizontal axis above a flat conducting surface should induce eddy currents in said surface through the variable magnetic flux. The eddy currents produce, in turn, their own magnetic fields which interact with the magnets of the EDW. We demonstrated that these interactions produce both drag and lift forces on the EDW which can theoretically be used for lift and propulsion of the EDW. The focus of our experiments is determining how to maximize the lift-to-drag ratio by the proper choice of the induction element. We will also describe our experiments with a rotating circular Halbach array having the strong magnetic field of about 1 T on the flat side of the ring, and acting as a hovercraft.

  8. ProSEDS Telemetry System Utilization of GPS Position Data for Transmitter Cycling

    NASA Technical Reports Server (NTRS)

    Kennedy, Paul; Sims, Herb

    2000-01-01

    NASA Marshall Space Flight Center will launch the Propulsive Small Expendable Deployer System (ProSEDS) space experiment in late 2000. ProSEDS will demonstrate the use of an electrodynamic tether propulsion system and will utilize a conducting wire tether to generate limited spacecraft power. This paper will provide an overview of the ProSEDS mission and will discuss the design, development and test of the spacecraft telemetry system which utilizes a custom designed GPS subsystem to determine spacecraft position relative to ground station location and to control transmitter on/off cycling based on spacecraft state vector and ground station visibility.

  9. Modeling and Simulation of a Tethered Harpoon for Comet Sampling

    NASA Technical Reports Server (NTRS)

    Quadrelli, Marco B.

    2014-01-01

    This paper describes the development of a dynamic model and simulation results of a tethered harpoon for comet sampling. This model and simulation was done in order to carry out an initial sensitivity analysis for key design parameters of the tethered system. The harpoon would contain a canister which would collect a sample of soil from a cometary surface. Both a spring ejected canister and a tethered canister are considered. To arrive in close proximity of the spacecraft at the end of its trajectory so it could be captured, the free-flying canister would need to be ejected at the right time and with the proper impulse, while the tethered canister must be recovered by properly retrieving the tether at a rate that would avoid an excessive amplitude of oscillatory behavior during the retrieval. The paper describes the model of the tether dynamics and harpoon penetration physics. The simulations indicate that, without the tether, the canister would still reach the spacecraft for collection, that the tether retrieval of the canister would be achievable with reasonable fuel consumption, and that the canister amplitude upon retrieval would be insensitive to variations in vertical velocity dispersion.

  10. The Tethered Moon

    NASA Technical Reports Server (NTRS)

    Zahnle, Kevin; Lupu, Roxana Elena; Dubrovolskis, A. R.

    2014-01-01

    that the Moon's orbit evolves is limited by the modest radiative cooling rate of Earth's atmosphere, which in effect tethers the Moon to the Earth. Consequently the Moon's orbit evolves orders of magnitude more slowly than in conventional models. Slow orbital evolution promotes capture by orbital resonances that may have been important in the Earth-Moon system

  11. Quantum electrodynamical time-dependent density functional theory for many-electron systems on a lattice

    NASA Astrophysics Data System (ADS)

    Farzanehpour, Mehdi; Tokatly, Ilya; Nano-Bio Spectroscopy Group; ETSF Scientific Development Centre Team

    2015-03-01

    We present a rigorous formulation of the time-dependent density functional theory for interacting lattice electrons strongly coupled to cavity photons. We start with an example of one particle on a Hubbard dimer coupled to a single photonic mode, which is equivalent to the single mode spin-boson model or the quantum Rabi model. For this system we prove that the electron-photon wave function is a unique functional of the electronic density and the expectation value of the photonic coordinate, provided the initial state and the density satisfy a set of well defined conditions. Then we generalize the formalism to many interacting electrons on a lattice coupled to multiple photonic modes and prove the general mapping theorem. We also show that for a system evolving from the ground state of a lattice Hamiltonian any density with a continuous second time derivative is locally v-representable. Spanish Ministry of Economy and Competitiveness (Grant No. FIS2013-46159-C3-1-P), Grupos Consolidados UPV/EHU del Gobierno Vasco (Grant No. IT578-13), COST Actions CM1204 (XLIC) and MP1306 (EUSpec).

  12. The Electrodynamics of Gradient Fields in Superconductive Magnetic Resonance Imaging Systems

    NASA Astrophysics Data System (ADS)

    Morich, Michael Andrew

    The eddy current problem associated with magnetic field gradients in superconductive magnetic resonance imaging (MRI) and spectroscopy (MRS) applications is well-known throughout the nuclear magnetic resonance (NMR) scientific and engineering community. The electromagnetic interaction of gradient field coils with surrounding cold (4.2 K to 80 K) and warm (300 K) metal structures from which the superconducting magnet systems are fabricated, nonetheless, has largely remained unstudied from a theoretical standpoint. There is a great need for a fundamental understanding of this interaction, which, it is fair to say, is a major determinant of imaging system performance due to its impact on gradient pulse fidelity. The work presented in this dissertation addresses this need and advances our knowledge and understanding of the gradient coil and cold shield interaction problem. It goes beyond the gross approximations of superconducting shell and skin-effect models used in present self-shielded and unshielded gradient coil design schemes. In essence, we take into account the fact that a typical gradient pulse spectrum spans DC to several kHz and, hence, skin-effect arguments are invalid. The work is largely theoretical in nature and provides solutions to canonical and more generalized problems involving axial (azimuthal separation constant m = 0) and distributed transverse (m = +/-1) gradient field coils which interact with cylindrical metallic shells of finite conductivity, various thicknesses and of infinite length. The electromagnetic boundary-value problems are developed and are then solved in the spectral domain, exclusive of the radial variable. The solutions are obtained directly in the spectral domain for three cases: (i) m = 0 and a single shell of infinite thickness, (ii) m = 0 and a single shell of finite thickness, and (iii) m = +/-1 and a single shell of infinite thickness. A normalized matrix solution is then developed for the general N-shell problem and is

  13. Method for identifying electromagnetically induced transparency in a tunable circuit quantum electrodynamics system

    NASA Astrophysics Data System (ADS)

    Liu, Qi-Chun; Li, Tie-Fu; Luo, Xiao-Qing; Zhao, Hu; Xiong, Wei; Zhang, Ying-Shan; Chen, Zhen; Liu, J. S.; Chen, Wei; Nori, Franco; Tsai, J. S.; You, J. Q.

    2016-05-01

    Electromagnetically induced transparency (EIT) has been realized in atomic systems, but fulfilling the EIT conditions for artificial atoms made from superconducting circuits is a more difficult task. Here we report an experimental observation of the EIT in a tunable three-dimensional transmon by probing the cavity transmission. To fulfill the EIT conditions, we tune the transmon to adjust its damping rates by utilizing the effect of the cavity on the transmon states. From the experimental observations, we clearly identify the EIT and Autler-Townes splitting (ATS) regimes as well as the transition regime in between. Also, the experimental data demonstrate that the threshold ΩAIC determined by the Akaike information criterion can describe the EIT-ATS transition better than the threshold ΩEIT given by the EIT theory.

  14. The Tethered Moon

    NASA Astrophysics Data System (ADS)

    Zahnle, Kevin; Lupu, R.; Fegley, B.; Marley, M.; Sleep, N.; Dobrovolskis, A.

    2013-10-01

    Cosmic collisions between terrestrial planets resemble somewhat the life cycle of the phoenix: worlds collide, are consumed in flame, and after the debris has cleared, shiny new worlds emerge aglow with possibilities. And glow they do, for they are molten. How brightly they glow, and for how long, is determined by their atmospheres, and by their moons. stop. It is well known that the atmosphere's thermal blanketing effect prevents a magma ocean from cooling rapidly. Several models have considered thick H2O-CO2 atmospheres over cooling magma oceans. These models address how the magma ocean freezes, how long it takes to freeze, and how, when, and what is degassed. stop. The atmosphere over a magmasphere is very hot and so contains the geochemical volatiles that can evaporate from a magma ocean, such as sulfur, alkalis and halogens, in addition to H2O and CO2. We compute 1-D non-gray radiative-convective atmospheric structure models that include all the molecular and atomic opacity sources that would be present in equilibrium over a magma ocean. We use these to compute cooling rates for hot post-giant-impact terrestrial planets. Our model is in excellent asymptotic agreement with two recent independent calculations of the runaway greenhouse limit for H2O-CO2 atmosphere. For cooling of the magma ocean itself, we use parameterizations recommended by Solomatov. stop. Tidal heating of the Earth by the Moon is important, because it is a big term, and because it occurs mostly in mantle materials that are just beginning to freeze, which frustrates freezing. The Moon is entwined with Earth by a negative feedback between thermal blanketing and tidal heating that comes from the temperature-dependent viscosity of the magma ocean. Because of this feedback, the rate that the Moon's orbit evolves is limited by the modest radiative cooling rate of Earth's atmosphere, which in effect tethers the Moon to the Earth. Consequently the Moon's orbit evolves orders of magnitude more slowly

  15. Structure of Aristotelian electrodynamics

    NASA Astrophysics Data System (ADS)

    Jacobson, Ted

    2015-07-01

    Aristotelian electrodynamics (AE) describes the regime of a plasma with a very strong electric field that is not shorted out, with the charge current determined completely by pair production and the balance of the Lorentz 4-force against the curvature radiation reaction. Here it is shown how the principal null directions and associated eigenvalues of the field tensor govern AE, and how force-free electrodynamics arises smoothly from AE when the eigenvalues (and therefore the electric field in some frame) vanish. A criterion for validity of AE and force-free electrodynamics is proposed in terms of a pair of "field curvature scalars" formed from the first derivative of the principal null directions.

  16. First quantized electrodynamics

    SciTech Connect

    Bennett, A.F.

    2014-06-15

    The parametrized Dirac wave equation represents position and time as operators, and can be formulated for many particles. It thus provides, unlike field-theoretic Quantum Electrodynamics (QED), an elementary and unrestricted representation of electrons entangled in space or time. The parametrized formalism leads directly and without further conjecture to the Bethe–Salpeter equation for bound states. The formalism also yields the Uehling shift of the hydrogenic spectrum, the anomalous magnetic moment of the electron to leading order in the fine structure constant, the Lamb shift and the axial anomaly of QED. -- Highlights: •First-quantized electrodynamics of the parametrized Dirac equation is developed. •Unrestricted entanglement in time is made explicit. •Bethe and Salpeter’s equation for relativistic bound states is derived without further conjecture. •One-loop scattering corrections and the axial anomaly are derived using a partial summation. •Wide utility of semi-classical Quantum Electrodynamics is argued.

  17. Anomalous electrodynamic explosions in liquids

    SciTech Connect

    Aspden, H.

    1986-06-01

    The recently reported Graneau experiments on electrodynamic explosions in liquids, which reveal anomalous longitudinal electrodynamic forces of the order of 10/sup 4/ times greater than expected, verify the need for a term in the law of electrodynamics that corresponds to the ion/electron mass ratio. This confirms an earlier theoretical interpretation of the anomalous cathode reaction forces found in the vacuum arc.

  18. Electrodynamics, wind and temperature

    NASA Technical Reports Server (NTRS)

    Schmidlin, F. J.

    1988-01-01

    This RTOP provides for correlative meteorological wind and temperature measurements with atmospheric electrodynamic measurements. Meteorological rocketsondes were launched as part of a number of electrodynamic investigations in Alaska, Norway, Peru, Sweden, and at the Wallops Flight Facility, Wallops Island, Virginia. Measurements obtained as part of the MAC/Epsilon campaign during October 1987 from Andoya, Norway, were in conjunction with electric field, ion mobility, conductivity, and energy deposition studies. The measurements obtained between 30 and 90 km are to evaluate and correlate changes in the atmospheric electrical structure caused by the neutral wind and temperature, or changes in the neutral atmosphere resulting from electrical anomalies.

  19. Galilean conformal electrodynamics

    NASA Astrophysics Data System (ADS)

    Bagchi, Arjun; Basu, Rudranil; Mehra, Aditya

    2014-11-01

    Maxwell's Electrodynamics admits two distinct Galilean limits called the Electric and Magnetic limits. We show that the equations of motion in both these limits are invariant under the Galilean Conformal Algebra in D = 4, thereby exhibiting non-relativistic conformal symmetries. Remarkably, the symmetries are infinite dimensional and thus Galilean Electrodynamics give us the first example of an infinitely extended Galilean Conformal Field Theory in D > 2. We examine details of the theory by looking at purely non-relativistic conformal methods and also use input from the limit of the relativistic theory.

  20. SPHERES tethered formation flight testbed: advancements in enabling NASA's SPECS mission

    NASA Astrophysics Data System (ADS)

    Chung, Soon-Jo; Adams, Danielle; Saenz-Otero, Alvar; Kong, Edmund; Miller, David W.; Leisawitz, David; Lorenzini, Enrico; Sell, Steve

    2006-06-01

    This paper reports on efforts to control a tethered formation flight spacecraft array for NASA's SPECS mission using the SPHERES test-bed developed by the MIT Space Systems Laboratory. Specifically, advances in methodology and experimental results realized since the 2005 SPIE paper are emphasized. These include a new test-bed setup with a reaction wheel assembly, a novel relative attitude measurement system using force torque sensors, and modeling of non-ideal tethers to account for tether vibration modes. The nonlinear equations of motion of multi-vehicle tethered spacecraft with elastic flexible tethers are derived from Lagrange's equations. The controllability analysis indicates that both array resizing and spin-up are fully controllable by the reaction wheels and the tether motor, thereby saving thruster fuel consumption. Based upon this analysis, linear and nonlinear controllers have been successfully implemented on the tethered SPHERES testbed, and tested at the NASA MSFC's flat floor facility using two and three SPHERES configurations.

  1. Elastic-Tether Suits for Artificial Gravity and Exercise

    NASA Technical Reports Server (NTRS)

    Torrance, Paul; Biesinger, Paul; Rybicki, Daniel D.

    2005-01-01

    Body suits harnessed to systems of elastic tethers have been proposed as means of approximating the effects of normal Earth gravitation on crewmembers of spacecraft in flight to help preserve the crewmembers physical fitness. The suits could also be used on Earth to increase effective gravitational loads for purposes of athletic training. The suit according to the proposal would include numerous small tether-attachment fixtures distributed over its outer surface so as to distribute the artificial gravitational force as nearly evenly as possible over the wearer s body. Elastic tethers would be connected between these fixtures and a single attachment fixture on a main elastic tether that would be anchored to a fixture on or under a floor. This fixture might include multiple pulleys to make the effective length of the main tether great enough that normal motions of the wearer cause no more than acceptably small variations in the total artificial gravitational force. Among the problems in designing the suit would be equalizing the load in the shoulder area and keeping tethers out of the way below the knees to prevent tripping. The solution would likely include running tethers through rings on the sides. Body suits with a weight or water ballast system are also proposed for very slight spinning space-station scenarios, in which cases the proposed body suits will easily be able to provide the equivalency of a 1-G or even greater load.

  2. Causality in Classical Electrodynamics

    ERIC Educational Resources Information Center

    Savage, Craig

    2012-01-01

    Causality in electrodynamics is a subject of some confusion, especially regarding the application of Faraday's law and the Ampere-Maxwell law. This has led to the suggestion that we should not teach students that electric and magnetic fields can cause each other, but rather focus on charges and currents as the causal agents. In this paper I argue…

  3. Tethered float liquid level sensor

    DOEpatents

    Daily, III, William Dean

    2016-09-06

    An apparatus for sensing the level of a liquid includes a float, a tether attached to the float, a pulley attached to the tether, a rotation sensor connected to the pulley that senses vertical movement of said float and senses the level of the liquid.

  4. Computer simulations of block copolymer tethered nanoparticle self-assembly

    NASA Astrophysics Data System (ADS)

    Chan, Elaine R.; Ho, Lin C.; Glotzer, Sharon C.

    2006-08-01

    We perform molecular simulations to study the self-assembly of block copolymer tethered cubic nanoparticles. Minimal models of the tethered nanoscale building blocks (NBBs) are utilized to explore the structures arising from self-assembly. We demonstrate that attaching a rigid nanocube to a diblock copolymer affects the typical equilibrium morphologies exhibited by the pure copolymer. Lamellar and cylindrical phases are observed in both systems but not at the corresponding relative copolymer tether block fractions. The effect of nanoparticle geometry on phase behavior is investigated by comparing the self-assembled structures formed by the tethered NBBs with those of their linear ABC triblock copolymer counterparts. The tethered nanocubes exhibit the conventional triblock copolymer lamellar and cylindrical phases when the repulsive interactions between different blocks are symmetric. The rigid and bulky nature of the cube induces interfacial curvature in the tethered NBB phases compared to their linear ABC triblock copolymer counterparts. We compare our results with those structures obtained from ABC diblock copolymer tethered nanospheres to further elucidate the role of cubic nanoparticle geometry on self-assembly.

  5. Experimental investigation of the dynamics of spinning tethered bodies

    NASA Astrophysics Data System (ADS)

    Modi, V. J.; Pradhan, S.; Chu, M.; Tyc, G.; Misra, A. K.

    1996-10-01

    Ground based experiments are conducted as a part of the OEDIPUS-C sounding rocket mission, scheduled for launch in the winter of 1995. Here OEDIPUS stands for Observation of Electrified Distribution in Ionospheric Plasma—a Unique Strategy. The OEDIPUS-C configuration consists of two spinning bodies connected by a 1 km long tether (the spin axis is nominally along the tether line). The objective is to assess dynamic behaviour of the tether and the payload. The test configuration consists of an end-body supported by a tether. The test procedure involves slow spin-up of the system and identifying the speeds corresponding to onset of the tether modes or the large amplitude end-body coning. This is referred to as the critical speed and corresponds to the stability boundary of the system. Experimental results are obtained for four different bodies to study the system stability over a wide range of mass and geometric parameters. Effect of offset of the tether attachment from the end-body centre of mass is also investigated. The observed critical speeds are compared with those given by the linear theory. The test results are generally in very good agreement with the theory, however several transient phenomena observed during the test suggest that system nonlinearities cannot be ignored when modelling such a complex system.

  6. Accretion disk electrodynamics

    NASA Technical Reports Server (NTRS)

    Coroniti, F. V.

    1985-01-01

    Accretion disk electrodynamic phenomena are separable into two classes: (1) disks and coronas with turbulent magnetic fields; (2) disks and black holes which are connected to a large-scale external magnetic field. Turbulent fields may originate in an alpha-omega dynamo, provide anomalous viscous transport, and sustain an active corona by magnetic buoyancy. The large-scale field can extract energy and angular momentum from the disk and black hole, and be dynamically configured into a collimated relativistic jet.

  7. On generalized logarithmic electrodynamics

    NASA Astrophysics Data System (ADS)

    Kruglov, S. I.

    2015-02-01

    The generalized logarithmic electrodynamics with two parameters and is considered. The indexes of refraction of light in the external magnetic field are calculated. In the case we come to results obtained by Gaete and Helayël-Neto (Eur Phys J C 74:2816, 2014). The bound on the values of , was obtained from the Biréfringence Magnétique du Vide (BMV) experiment. The symmetrical Belinfante energy-momentum tensor and dilatation current are found.

  8. Tethered catalysts for the hydration of carbon dioxide

    SciTech Connect

    Valdez, Carlos A; Satcher, Jr., Joe H; Aines, Roger D; Wong, Sergio E; Baker, Sarah E; Lightstone, Felice C; Stolaroff, Joshuah K

    2014-11-04

    A system is provided that substantially increases the efficiency of CO.sub.2 capture and removal by positioning a catalyst within an optimal distance from the air-liquid interface. The catalyst is positioned within the layer determined to be the highest concentration of carbon dioxide. A hydrophobic tether is attached to the catalyst and the hydrophobic tether modulates the position of the catalyst within the liquid layer containing the highest concentration of carbon dioxide.

  9. Stability of DNA-Tethered Lipid Membranes with Mobile Tethers

    PubMed Central

    Chung, Minsub; Boxer, Steven G.

    2011-01-01

    We recently introduced two approaches for tethering planar lipid bilayers as membrane patches to either a supported lipid bilayer or DNA-functionalized surface using DNA hybridization (Chung, M., Lowe, R. D., Chan, Y-H. M., Ganesan, P. V., Boxer, S. G. J. Struct. Biol. 2009, 168, 190–9). When mobile DNA tethers are used, the tethered bilayer patches become unstable, while they are stable if the tethers are fixed on the surface. Because the mobile tethers between a patch and a supported lipid bilayer offer a particularly interesting architecture for studying the dynamics of membrane-membrane interactions, we have investigated the sources of instability, focusing on membrane composition. The most stable patches were made with a mixture of saturated lipids and cholesterol, suggesting an important role for membrane stiffness. Other factors such as the effect of tether length, lateral mobility and patch membrane edge were also investigated. Based on these results, a model for the mechanism of patch destruction is developed. PMID:21452847

  10. Elastic issues and vibration reduction in a tethered deorbiting mission

    NASA Astrophysics Data System (ADS)

    Sabatini, Marco; Gasbarri, Paolo; Palmerini, Giovanni B.

    2016-05-01

    Recently proposed mission concepts involving harpoons or nets to capture and de-orbit debris represent an interesting application of the tethered systems, where the orbiting bodies are connected by a flexible link. These systems present a complex behavior, as flexible characteristics combine with orbital dynamics. The focus of the paper is on the dynamic behavior of the tethered system in the final phase of the de-orbiting mission, when a powerful apogee motor is used to change the debris orbit. The thrust action introduces significant issues, as elastic waves propagate along the tether, and the relevant oscillations couple with the orbital dynamics. Input shaping techniques are proposed to limit or cancel these oscillations. However, the performance of these techniques drops when non-ideal scenarios are considered. In particular, an initially slack tether is a serious issue that must be solved if acceptably low oscillations of the tether are to be obtained. Three strategies are proposed and discussed in this paper to remove the slack condition: a natural drift of the chaser by means of a single impulse, a controlled maneuver for precisely adjusting the relative distance between chaser spacecraft and debris, and a retrieval mechanism for changing the tether length.

  11. Emerging Insights into the Roles of Membrane Tethers from Analysis of Whole Organisms: The Tip of an Iceberg?

    PubMed Central

    Toh, Wei Hong; Gleeson, Paul A.

    2016-01-01

    Membrane tethers have been identified throughout different compartments of the endomembrane system. It is now well established that a number of membrane tethers mediate docking of membrane carriers in anterograde and retrograde transport and in regulating the organization of membrane compartments. Much of our information on membrane tethers have been obtained from the analysis of individual membrane tethers in cultured cells. In the future it will be important to better appreciate the network of interactions mediated by tethers and the potential co-ordination of their collective functions in vivo. There are now a number of studies which have analyzed membrane tethers in tissues and organisms which are providing new insights into the role of this class of membrane protein at the physiological level. Here we review recent advances in the understanding of the function of membrane tethers from knock outs (or knock downs) in whole organisms and from mutations in tethers associated with disease. PMID:26973835

  12. The dynamics of tethers in artificial gravity applications

    NASA Astrophysics Data System (ADS)

    Glaese, John R.

    Artificial gravity can be generated in space by centrifual 'forces'. Tethers can be used to bind together systems of masses revolving about a common center. To assess the potential problems associated with such configurations it is desirable to investigate candidate concepts. This paper discusses deployment, spinup, despin, and retrieval. The dynamic behavior of a configuration consisting of two bodies connected by a flexible tether of nonnegligible mass is investigated. Results from simulations of the spinup operation are presented. Tether dynamic behavior will have a significant impact on the feasibility of these concepts. The requirement for suppression of tether oscillations imposes limitations on speed of deployment and retrieval. Deployment and retrieval scenarios are proposed and considered. Preliminary results do not indicate a need for special control laws to damp lateral oscillations.

  13. Electrodynamic Dust Shield Demonstrator

    NASA Technical Reports Server (NTRS)

    Stankie, Charles G.

    2013-01-01

    The objective of the project was to design and manufacture a device to demonstrate a new technology developed by NASA's Electrostatics and Surface Physics Laboratory. The technology itself is a system which uses magnetic principles to remove regolith dust from its surface. This project was to create an enclosure that will be used to demonstrate the effectiveness of the invention to The Office of the Chief Technologist. ONE of the most important challenges of space exploration is actually caused by something very small and seemingly insignificant. Dust in space, most notably on the moon and Mars, has caused many unforeseen issues. Dirt and dust on Earth, while a nuisance, can be easily cleaned and kept at bay. However, there is considerably less weathering and erosion in space. As a result, the microscopic particles are extremely rough and abrasive. They are also electrostatically charged, so they cling to everything they make contact with. This was first noted to be a major problem during the Apollo missions. Dust would stick to the spacesuits, and could not be wiped off as predicted. Dust was brought back into the spacecraft, and was even inhaled by astronauts. This is a major health hazard. Atmospheric storms and other events can also cause dust to coat surfaces of spacecraft. This can cause abrasive damage to the craft. The coating can also reduce the effectiveness of thermal insulation and solar panels.' A group of engineers at Kennedy Space Center's Electrostatics and Surface Physics Laboratory have developed a new technology, called the Electrodynamic Dust Shield, to help alleviate these problems. It is based off of the electric curtain concept developed at NASA in 1967. "The EDS is an active dust mitigation technology that uses traveling electric fields to transport electrostatically charged dust particles along surfaces. To generate the traveling electric fields, the EDS consists of a multilayer dielectric coating with an embedded thin electrode grid

  14. Preliminary Orbit Determination of a Tethered Satellite Using the p-Iteration Method

    NASA Astrophysics Data System (ADS)

    Cicci, D. A.; Qualls, C.

    2016-06-01

    The possibility of the future deployment of tethered satellites has created a need for a preliminary orbit determination method capable of determining whether or not a satellite is tethered to another satellite. Classical preliminary orbit determination methods, which are used for untethered satellites, typically require two or more position vectors along with their respective observation times in order to determine a preliminary orbital element set. However, these conventional methods can't distinguish between an untethered satellite and a tethered one, whose motion is modified due to the presence of a tether force. The use of conventional methods on a satellite which is part of a tethered satellite system will result in the calculation of inaccurate orbital elements. Modifications have been made to the p-iteration preliminary orbit determination method in order to allow for the identification of these tethered satellites. The modifications allow for the calculation of a modified gravitational parameter, which can be used to distinguish between a tethered satellite and an untethered one. This paper applies this modified p-iteration method to the problem of the quick identification of a tethered satellite. The performance of this method is evaluated through scenarios of differing tether lengths, levels of observation error, and orbital eccentricities. Due to the need for the preliminary orbit determination to be achieved quickly, only short time intervals between observations were considered. The manner in which this preliminary orbit information can be used to obtain tether parameters for the subsequent differential correction process is also described.

  15. Preliminary Orbit Determination of a Tethered Satellite Using the p-Iteration Method

    NASA Astrophysics Data System (ADS)

    Cicci, D. A.; Qualls, C.

    2016-04-01

    The possibility of the future deployment of tethered satellites has created a need for a preliminary orbit determination method capable of determining whether or not a satellite is tethered to another satellite. Classical preliminary orbit determination methods, which are used for untethered satellites, typically require two or more position vectors along with their respective observation times in order to determine a preliminary orbital element set. However, these conventional methods can't distinguish between an untethered satellite and a tethered one, whose motion is modified due to the presence of a tether force. The use of conventional methods on a satellite which is part of a tethered satellite system will result in the calculation of inaccurate orbital elements. Modifications have been made to the p-iteration preliminary orbit determination method in order to allow for the identification of these tethered satellites. The modifications allow for the calculation of a modified gravitational parameter, which can be used to distinguish between a tethered satellite and an untethered one. This paper applies this modified p-iteration method to the problem of the quick identification of a tethered satellite. The performance of this method is evaluated through scenarios of differing tether lengths, levels of observation error, and orbital eccentricities. Due to the need for the preliminary orbit determination to be achieved quickly, only short time intervals between observations were considered. The manner in which this preliminary orbit information can be used to obtain tether parameters for the subsequent differential correction process is also described.

  16. Tethered nuclear power for the Space Station

    NASA Technical Reports Server (NTRS)

    Bents, D. J.

    1985-01-01

    A nuclear space power system the SP-100 is being developed for future missions where large amounts of electrical power will be required. Although it is primarily intended for unmanned spacecraft, it can be adapted to a manned space platform by tethering it above the station through an electrical transmission line which isolates the reactor far away from the inhabited platform and conveys its power back to where it is needed. The transmission line, used in conjunction with an instrument rate shield, attenuates reactor radiation in the vicinity of the space station to less than one-one hundredth of the natural background which is already there. This combination of shielding and distance attenuation is less than one-tenth the mass of boom-mounted or onboard man-rated shields that are required when the reactor is mounted nearby. This paper describes how connection is made to the platform (configuration, operational requirements) and introduces a new element the coaxial transmission tube which enables efficient transmission of electrical power through long tethers in space. Design methodology for transmission tubes and tube arrays is discussed. An example conceptual design is presented that shows SP-100 at three power levels 100 kWe, 300 kWe, and 1000 kWe connected to space station via a 2 km HVDC transmission line/tether. Power system performance, mass, and radiation hazard are estimated with impacts on space station architecture and operation.

  17. Tethered nuclear power for the space station

    NASA Technical Reports Server (NTRS)

    Bents, D. J.

    1985-01-01

    A nuclear space power system the SP-100 is being developed for future missions where large amounts of electrical power will be required. Although it is primarily intended for unmanned spacecraft, it can be adapted to a manned space platform by tethering it above the station through an electrical transmission line which isolates the reactor far away from the inhabited platform and conveys its power back to where it is needed. The transmission line, used in conjunction with an instrument rate shield, attenuates reactor radiation in the vicinity of the space station to less than one-one hundredth of the natural background which is already there. This combination of shielding and distance attenuation is less than one-tenth the mass of boom-mounted or onboard man-rated shields that are required when the reactor is mounted nearby. This paper describes how connection is made to the platform (configuration, operational requirements) and introduces a new element the coaxial transmission tube which enables efficient transmission of electrical power through long tethers in space. Design methodology for transmission tubes and tube arrays is discussed. An example conceptual design is presented that shows SP-100 at three power levels 100 kWe, 300 kWe, and 1000 kWe connected to space station via a 2 km HVDC transmission line/tether. Power system performance, mass, and radiation hazard are estimated with impacts on space station architecture and operation.

  18. Investigation of nonlinear E.M. phenomena in the tethered magnetospheric cloud

    NASA Technical Reports Server (NTRS)

    Alpert, Yakov L.

    1990-01-01

    Nonlinear effects of parametric and of heating type, produced in a plasma under the action of an electric field E(sub 0)(e exp i(omega)t), are considered in this work in connection with the Tethered Magnetospheric Cloud (TMC) accompanying the Tether Satellite System (TSS). The theoretical results show that these phenomena should appear in the ionosphere at high altitudes Z greater than or = (150-200) km, particularly, at Z approximately = 300 km of the TSS system orbit. Therefore, it is of a special interest to search these phenomena by such a unique experiment as the forthcoming first TSS-I and by the future, perhaps modified TSS missions. Because of the parametric decay instability, new branches of wave may be excited both around the electron and ion Lengmuir frequencies Omega (sub 0) = 2(pi)f(sub 0) and Omega (sub 0) = 2(pi)f(sub 0) under the influence of high frequency (HF), (f less than or = 10(exp 6) to few 10(exp 6) Hz), strong electric waves. The heating of all the kinds of particles is growing up very quickly in the ionosphere with altitude in the extra low and very low frequency ranges, F approximately = (1 to 10(exp 4) Hz, discussed below. The temperatures (energies), for example, of the electrons accelerated by the electric field become larger than the ionization potential in this frequency range already at altitudes Z greater than or = (150 - 200) km when the amplitude of the electric field is the absolute value of E(sub 0) approximately = (1-2) mV/m. The sources of these electric fields may be in the TSS-I mission, that so called Phantom Loop (PL) - the Tethered Electrodynamic Tail (TET), and the different kind of electromagnetic oscillations produced by different kinds of instabilities in the TMC plasma. The growth rates of these instabilities will become very high in the TSS surrounding magnetoplasma. However, in the future TSS missions, special artificial sources (generators) of electric fields should be used for these investigations.

  19. Nonlinear electrodynamics at Cinvestav

    NASA Astrophysics Data System (ADS)

    Bretón, Nora

    2012-02-01

    After a brief introduction to the original aims of Nonlinear electrodynamics (NLED), a review on NLED research that has been developed in the Physics Department at Cinvestav-IPN is addressed: from the seminal work by Jerzy Plebañski, which was followed by S. Hacyan and S. Alarcón, afterwards by A. García and H. Salazar; and more recently by E. Ayón-Beato and N. Bretón. We conclude by pointing to the current streams of research.

  20. Semi-classical Electrodynamics

    NASA Astrophysics Data System (ADS)

    Lestone, John

    2016-03-01

    Quantum electrodynamics is complex and its associated mathematics can appear overwhelming for those not trained in this field. We describe semi-classical approaches that can be used to obtain a more intuitive physical feel for several QED processes including electro-statics, Compton scattering, pair annihilation, the anomalous magnetic moment, and the Lamb shift, that could be taught easily to undergraduate students. Any physicist who brings their laptop to the talk will be able to build spread sheets in less than 10 minutes to calculate g/2 =1.001160 and a Lamb shift of 1057 MHz.

  1. Electrodynamic force law controversy.

    PubMed

    Graneau, P; Graneau, N

    2001-05-01

    Cavalleri et al. [Phys. Rev. E 52, 2505 (1998); Eur. J. Phys. 17, 205 (1996)] have attempted to resolve the electrodynamic force law controversy. This attempt to prove the validity of either the Ampère or Lorentz force law by theory and experiment has revealed only that the two are equivalent when predicting the force on part of a circuit due to the current in the complete circuit. However, in our analysis of internal stresses, only Ampère's force law agrees with experiment. PMID:11415053

  2. Behavior of tethered debris with flexible appendages

    NASA Astrophysics Data System (ADS)

    Aslanov, Vladimir S.; Yudintsev, Vadim V.

    2014-11-01

    Active exploration of the space leads to growth of a near-Earth space pollution. The frequency of the registered collisions of space debris with functional satellites highly increased during last 10 years. As a rule a large space debris can be observed from the Earth and catalogued, then it is possible to avoid collision with the active spacecraft. However every large debris is a potential source of a numerous small debris particles. To reduce debris population in the near Earth space the large debris should be removed from working orbits. The active debris removal technique is considered that intend to use a tethered orbital transfer vehicle, or a space tug attached by a tether to the space debris. This paper focuses on the dynamics of the space debris with flexible appendages. Mathematical model of the system is derived using the Lagrange formalism. Several numerical examples are presented to illustrate the mutual influence of the oscillations of flexible appendages and the oscillations of a tether. It is shown that flexible appendages can have a significant influence on the attitude motion of the space debris and the safety of the transportation process.

  3. Planar Multilayer Circuit Quantum Electrodynamics

    NASA Astrophysics Data System (ADS)

    Minev, Z. K.; Serniak, K.; Pop, I. M.; Leghtas, Z.; Sliwa, K.; Hatridge, M.; Frunzio, L.; Schoelkopf, R. J.; Devoret, M. H.

    2016-04-01

    Experimental quantum information processing with superconducting circuits is rapidly advancing, driven by innovation in two classes of devices, one involving planar microfabricated (2D) resonators, and the other involving machined three-dimensional (3D) cavities. We demonstrate that circuit quantum electrodynamics can be implemented in a multilayer superconducting structure that combines 2D and 3D advantages. We employ standard microfabrication techniques to pattern each layer, and rely on a vacuum gap between the layers to store the electromagnetic energy. Planar qubits are lithographically defined as an aperture in a conducting boundary of the resonators. We demonstrate the aperture concept by implementing an integrated, two-cavity-mode, one-transmon-qubit system.

  4. Analysis of The Interaction of Space Tethers with Catalogued Space Objects

    NASA Technical Reports Server (NTRS)

    Bonometti, Joseph (Technical Monitor); Hoyt, Robert; Buller, Jason

    2005-01-01

    The potential for collisions or close passes with other space objects presents a significant issue for many space tether applications, representing a potential risk both to the integrity of the tether system and t o the safety of other spacecraft. Potential collisions between tethers and other space objects may be possible to avoid if close encounters can be predicted with sufficient precision and advance notice. In order to provide a method for predicting the frequency with which a tether must be maneuvered to avoid collisions, and to provide a resource for accurate close-encounter prediction during tether flight experiments, we have developed a software tool that compares the trajectory of a tether object with that of all of the objects in the NORAD space catalogue. In this paper we describe the models and algorithms used in this tool, and discuss results of test cases conducted to predict the close-encounter frequency of a tether systems ranging from a short nanosatellite-based tether experiment to a hundred-kilometer long MXER tether system.

  5. Magnetic Levitation Experiments with the Electrodynamic Wheel

    NASA Astrophysics Data System (ADS)

    Cordrey, Vincent; Gutarra-Leon, Angel; Gaul, Nathan; Majewski, Walerian

    Our experiments explored inductive magnetic levitation using circular Halbach arrays with the strong variable magnetic field on the outer rim of the ring. Such a system is usually called an Electrodynamic Wheel (EDW). Rotating this wheel around a horizontal axis above a flat conducting surface should induce eddy currents in said surface through the variable magnetic flux. The eddy currents produce, in turn, their own magnetic fields which interact with the magnets of the EDW. We constructed two Electrodynamic Wheels with different diameters and demonstrated that the magnetic interactions produce both lift and drag forces on the EDW which can be used for levitation and propulsion of the EDW. The focus of our experiments is the direct measurement of lift and drag forces to compare with theoretical models using wheels of two different radii. Supported by Grants from the Virginia Academy of Science, Society of Physics Students, Virginia Community College System, and the NVCC Educational Foundation.

  6. Development and application of the Manned Maneuvering Unit, work restraint system, stowage container and return line tether

    NASA Technical Reports Server (NTRS)

    Bergonz, F. H.; Okelly, J. K.; Whitsett, C. W.; Petynia, W. W.

    1981-01-01

    The Manned Maneuvering Unit (MMU), a self-contained zero-gravity backpack designed for astronaut extravehicular activity, is discussed with reference to the system requirements and characteristics, and potential near-term and future uses. Attention is given to the MMU man-machine interfaces, propulsion capability, attitude control, crew restraint hardware, donning, doffing, activation, and deactivation. Specific applications discussed include: spacecraft inspection and servicing, assembly of large space systems, payload deployment/retrieval, and crew rescue.

  7. Photon propagator in skewon electrodynamics

    NASA Astrophysics Data System (ADS)

    Itin, Yakov

    2016-01-01

    Electrodynamics with a local and linear constitutive law is used as a framework for models violating Lorentz covariance. The constitutive tensor of such a construction is irreducibly decomposed into three independent pieces. The principal part is the anisotropic generalization of the standard electrodynamics. The two other parts, axion and skewon, represent nonclassical modifications of electrodynamics. We derive the expression for the photon propagator in the Minkowski spacetime endowed with a skewon field. For a relatively small (antisymmetric) skewon field, a modified Coulomb law is exhibited.

  8. The Propulsive Small Expendable Deployer System (ProSEDS)

    NASA Technical Reports Server (NTRS)

    Lorenzini, Enrico C.

    2002-01-01

    This Annual Report covers the following main topics: 1) Updated Reference Mission. The reference ProSEDS (Propulsive Small Expendable Deployer System) mission is evaluated for an updated launch date in the Summer of 2002 and for the new 80-s current operating cycle. Simulations are run for nominal solar activity condition at the time of launch and for extreme conditions of dynamic forcing. Simulations include the dynamics of the system, the electrodynamics of the bare tether, the neutral atmosphere and the thermal response of the tether. 2) Evaluation of power delivered by the tether system. The power delivered by the tethered system during the battery charging mode is computed under the assumption of minimum solar activity for the new launch date. 3) Updated Deployment Control Profiles and Simulations. A number of new deployment profiles were derived based on the latest results of the deployment ground tests. The flight profile is then derived based on the friction characteristics obtained from the deployment tests of the F-1 tether. 4) Analysis/estimation of deployment flight data. A process was developed to estimate the deployment trajectory of the endmass with respect to the Delta and the final libration amplitude from the data of the deployer turn counters. This software was tested successfully during the ProSEDS mission simulation at MSFC (Marshall Space Flight Center) EDAC (Environments Data Analysis Center).

  9. Electrodynamics of planar Archimedean spiral resonator

    NASA Astrophysics Data System (ADS)

    Maleeva, N.; Averkin, A.; Abramov, N. N.; Fistul, M. V.; Karpov, A.; Zhuravel, A. P.; Ustinov, A. V.

    2015-07-01

    We present a theoretical and experimental study of electrodynamics of a planar spiral superconducting resonator of a finite length. The resonator is made in the form of a monofilar Archimedean spiral. By making use of a general model of inhomogeneous alternating current flowing along the resonator and specific boundary conditions on the surface of the strip, we obtain analytically the frequencies fn of resonances which can be excited in such system. We also calculate corresponding inhomogeneous RF current distributions ψ n ( r ) , where r is the coordinate across a spiral. We show that the resonant frequencies and current distributions are well described by simple relationships f n = f 1 n and ψ n ( r ) ≃ sin [ π n ( r / R e ) 2 ] , where n = 1 , 2... and Re is the external radius of the spiral. Our analysis of electrodynamic properties of spiral resonators' is in good agreement with direct numerical simulations and measurements made using specifically designed magnetic probe and laser scanning microscope.

  10. EMC Test Report Electrodynamic Dust Shield

    NASA Technical Reports Server (NTRS)

    Carmody, Lynne M.; Boyette, Carl B.

    2014-01-01

    This report documents the Electromagnetic Interference E M I evaluation performed on the Electrodynamic Dust Shield (EDS) which is part of the MISSE-X System under the Electrostatics and Surface Physics Laboratory at Kennedy Space Center. Measurements are performed to document the emissions environment associated with the EDS units. The purpose of this report is to collect all information needed to reproduce the testing performed on the Electrodynamic Dust Shield units, document data gathered during testing, and present the results. This document presents information unique to the measurements performed on the Bioculture Express Rack payload; using test methods prepared to meet SSP 30238 requirements. It includes the information necessary to satisfy the needs of the customer per work order number 1037104. The information presented herein should only be used to meet the requirements for which it was prepared.

  11. Numerical Simulation of Tethered Underwater Kites for Power Generation

    NASA Astrophysics Data System (ADS)

    Ghasemi, Amirmahdi; Olinger, David; Tryggvason, Gretar

    2015-11-01

    An emerging renewable energy technology, tethered undersea kites (TUSK), which is used to extract hydrokinetic energy from ocean and tidal currents, is studied. TUSK systems consist of a rigid-winged ``kite,'' or glider, moving in an ocean current which is connected by tethers to a floating buoy on the ocean surface. The TUSK kite is a current speed enhancement device since the kite can move in high-speed, cross-current motion at 4-6 times the current velocity, thus producing more power than conventional marine turbines. A computational simulation is developed to simulate the dynamic motion of an underwater kite and extendable tether. A two-step projection method within a finite volume formulation, along with an Open MP acceleration method, is employed to solve the Navier-Stokes equations. An immersed boundary method is incorporated to model the fluid-structure interaction of the rigid kite (with NACA 0012 airfoil shape in 2D and NACA 0021 airfoil shape in 3D simulations) and the fluid flow. PID control methods are used to adjust the kite angle of attack during power (tether reel-out) and retraction (reel-in) phases. Two baseline simulations (for kite motions in two and three dimensions) are studied, and system power output, flow field vorticity, tether tension, and hydrodynamic coefficients (lift and drag) for the kite are determined. The simulated power output shows good agreement with established theoretical results for a kite moving in two-dimensions.

  12. A new concept of solar power satellite: Tethered-SPS

    NASA Astrophysics Data System (ADS)

    Sasaki, Susumu; Tanaka, Koji; Higuchi, Ken; Okuizumi, Nobukatsu; Kawasaki, Shigeo; Shinohara, Naoki; Senda, Kei; Ishimura, Kousei

    2007-02-01

    Tethered solar power satellite (Tethered-SPS) consisting of a large panel with a capability of power generation/transmission and a bus system which are connected by multi-wires is proposed as an innovative solar power satellite (SPS). The power generation/transmission panel is composed of a huge number of perfectly equivalent power modules. The electric power generated by the solar cells at the surface of each module is converted to the microwave power in the same module. Since the modules are controlled by the bus system using wireless LAN, no wired signal/power interfaces are required between the modules. The attitude in which the microwave transmission antenna is directed to the ground is maintained by the gravity gradient force. The tethered panel is composed of individual tethered subpanels which are loosely connected to each other. This configuration enables an evolutional construction in which the function of the SPS grows as the construction proceeds. A scale model of the tethered subpanel can be used for the first step demonstration experiment of the SPS in the near future.

  13. Dynamics and control of the Space Station based tethered payload

    NASA Astrophysics Data System (ADS)

    Lakshmanan, P. K.; Modi, V. J.; Misra, A. K.

    A mathematical model is proposed here for studying the dynamics of the Tethered Satellite System (TSS) that consists of a plate-type Space Station from which a tether supported subsatellite is deployed or retrieved. The rigid body dynamics of the tether, subsatellite and Space Station are analyzed accounting for the mass of the tether as well as a three-dimensional offset of its point of attachment. Controllability of the linearized equations is established numerically and a comparative study of three different control strategies conducted. The strategies employ thrusters, tension in the tether line or motion of the offset of the attachment to achieve control of the system subjected to a relatively large initial disturbance. Results suggest that, in the stationkeeping mode, the tension control strategy damps a given disturbance in the shortest time, however, at an expense of the energy. On the other hand, the offset control proves to be the most efficient in terms of energy consumption, but now the response to disturbance persists over a long duration.

  14. Research on Orbital Plasma: Electrodynamics (ROPE)

    NASA Technical Reports Server (NTRS)

    Samir, Uri; Fontheim, Ernest G.

    2000-01-01

    Enhancements of the temperature of electrons in spacecraft plasma wakes have been reported for numerous cases and this phenomenon has been discussed both empirically and theoretically. However, very few measurements seem to have been made of the ion temperature within plasma wakes-possibly because the great majority of ion measurements were focussed on obtaining geophysical parameters and, hence, were confined to the region ahead of the spacecraft. Recently, however, an enhancement of the temperature of ions was discovered in data obtained in the wake of the Space Shuttle during the Spacelab-2 mission. At the time of that publication, this was the only known observation of this type. Herein, we report an additional case of ion temperature enhancement in a plasma wake. The data were taken during the Tethered Satellite System Reflight mission (TSS-1R) in the wake of the tethered satellite during passive (no current flow) operations. The measurements were obtained with the Differential Ion Flux Probe, or DIFP.

  15. Timelike Momenta In Quantum Electrodynamics

    DOE R&D Accomplishments Database

    Brodsky, S. J.; Ting, S. C. C.

    1965-12-01

    In this note we discuss the possibility of studying the quantum electrodynamics of timelike photon propagators in muon or electron pair production by incident high energy muon or electron beams from presently available proton or electron accelerators.

  16. Flight mechanics applications for tethers in space: Cooperative Italian-US programs

    NASA Technical Reports Server (NTRS)

    Bevilacqua, Franco; Merlina, Pietro; Anderson, John L.

    1990-01-01

    Since the 1974 proposal by Giuseppe Colombo to fly a tethered subsatellite from the Shuttle Orbiter, the creative thinking of many scientists and engineers from Italy and U.S. has generated a broad range of potential tether applications in space. Many of these applications have promise for enabling innovative research and operational activities relating to flight mechanics in earth orbit and at suborbital altitudes. From a flight mechanics standpoint the most interesting of the currently proposed flight demonstrations are: the second Tethered Satellite System experiment which offers both the potential for aerothermodynamics and hypersonics research and for atmospheric science research; the Tethered Initiated Space Recovery System which would enable orbital deboost and recovery of a re-entry vehicle and waste removal from a space station; and the Tether Elevator/Crawler System which would provide a variable microgravity environment and space station center of mass management. The outer atmospheric and orbital flight mechanics characteristics of these proposed tether flight demonstrations are described. The second Tethered Satellite System mission will deploy the tethered satellite earthward and will bring it as low as 130 km from ground and thus into the transition region between the atmosphere (non-ionized) and the partially ionized ionosphere. The atmospheric flight mechanics of the tethered satellite is discussed and simulation results are presented. The Tether Initiated Space Recovery System experiment will demonstrate the ability of a simple tether system to deboost and recover a reentry vehicle. The main feature of this demonstration is the utilization of a Small Expendable Deployment System (SEDS) and the low-tension deployment assumed to separate the reentry vehicle from the Shuttle. This low-tension deployment maneuver is discussed and its criticalities are outlined. The Tether Elevator/Crawler System is a new space element able to move in a controlled way

  17. Two applications of axion electrodynamics

    NASA Technical Reports Server (NTRS)

    Wilczek, Frank

    1987-01-01

    The equations of axion electrodynamics are studied. Variations in the axion field can give rise to peculiar distributions of charge and current. These effects provide a simple understanding of the fractional electric charge on dyons and of some recently discovered oddities in the electrodynamics of antiphase boundaries in PbTe. Some speculations regarding the possible occurrence of related phenomena in other solids are presented.

  18. Properties of noncommutative axionic electrodynamics

    NASA Astrophysics Data System (ADS)

    Gaete, Patricio; Schmidt, Iván

    2007-07-01

    Using the gauge-invariant but path-dependent variables formalism, we compute the static quantum potential for noncommutative axionic electrodynamics, and find a radically different result than the corresponding commutative case. We explicitly show that the static potential profile is analogous to that encountered in both non-Abelian axionic electrodynamics and in Yang-Mills theory with spontaneous symmetry breaking of scale symmetry.

  19. Electrodynamic Arrays Having Nanomaterial Electrodes

    NASA Technical Reports Server (NTRS)

    Trigwell, Steven (Inventor); Biris, Alexandru S. (Inventor); Calle, Carlos I. (Inventor)

    2013-01-01

    An electrodynamic array of conductive nanomaterial electrodes and a method of making such an electrodynamic array. In one embodiment, a liquid solution containing nanomaterials is deposited as an array of conductive electrodes on a substrate, including rigid or flexible substrates such as fabrics, and opaque or transparent substrates. The nanomaterial electrodes may also be grown in situ. The nanomaterials may include carbon nanomaterials, other organic or inorganic nanomaterials or mixtures.

  20. Investigation of dynamic noise affecting geodynamics information in a tethered subsatellite

    NASA Technical Reports Server (NTRS)

    Gullahorn, G. E.

    1984-01-01

    The effects of a tethered satellite system's internal dynamics on the subsatellite were calculated including both overall motions (libration and attitude oscillations) and internal tether oscillations. The SKYHOOK tether simulation program was modified to operate with atmospheric density variations and to output quantities of interest. Techniques and software for analyzing the results were developed including noise spectral analysis. A program was begun for computing a stable configuration of a tether system subject to air drag. These configurations will be of use as initial conditions for SKYHOOK and, through linearized analysis, directly for stability and dynamical studies. A case study in which the subsatellite traverses an atmospheric density enhancement confirmed some theoretical calculations, and pointed out some aspects of the interaction with the tether system dynamics.

  1. Tethered Pyrotechnic Apparatus for Acquiring a Ground Sample

    NASA Technical Reports Server (NTRS)

    Jones, Jack; Zimmerman, Wayne; Wu, Jiunn Jenq; Badescu, Mircea; Sherrit, Stewart

    2009-01-01

    A proposed alternative design for the balloon-borne ground-sampling system described in the immediately preceding article would not rely on free fall to drive a harpoonlike sample-collecting device into the ground. Instead, the harpoon-like sample-collecting device would be a pyrotechnically driven, tethered projectile. The apparatus would include a tripod that would be tethered to the gondola. A gun for shooting the projectile into the ground would be mounted at the apex of the tripod. The gun would include an electronic trigger circuit, a chamber at the breech end containing a pyrotechnic charge, and a barrel. A sabot would be placed in the barrel just below the pyrotechnic charge, and the tethered projectile would be placed in the barrel just below the sabot. The tripod feet would be equipped with contact sensors connected to the trigger circuit. In operation, the tripod would be lowered to the ground on its tether. Once contact with the ground was detected by the sensors on all three tripod feet, the trigger circuit would fire the pyrotechnic charge to drive the projectile into the ground. (Requiring contact among all three tripod feet and the ground would ensure that the projectile would be fired into the ground, rather than up toward the gondola or the balloon.) The tethered projectile would then be reeled back up to the gondola for analysis of the sample.

  2. Analytical investigation of the dynamics of tethered constellations in earth orbit

    NASA Technical Reports Server (NTRS)

    Lorenzini, Enrico C.; Gullahorn, Gordon E.; Estes, Robert D.

    1988-01-01

    This Quarterly Report on Tethering in Earth Orbit deals with three topics: (1) Investigation of the propagation of longitudinal and transverse waves along the upper tether. Specifically, the upper tether is modeled as three massive platforms connected by two perfectly elastic continua (tether segments). The tether attachment point to the station is assumed to vibrate both longitudinally and transversely at a given frequency. Longitudinal and transverse waves propagate along the tethers affecting the acceleration levels at the elevator and at the upper platform. The displacement and acceleration frequency-response functions at the elevator and at the upper platform are computed for both longitudinal and transverse waves. An analysis to optimize the damping time of the longitudinal dampers is also carried out in order to select optimal parameters. The analytical evaluation of the performance of tuned vs. detuned longitudinal dampers is also part of this analysis. (2) The use of the Shuttle primary Reaction Control System (RCS) thrusters for blowing away a recoiling broken tether is discussed. A microcomputer system was set up to support this operation. (3) Most of the effort in the tether plasma physics study was devoted to software development. A particle simulation code has been integrated into the Macintosh II computer system and will be utilized for studying the physics of hollow cathodes.

  3. Design and fabrication of the 20 km/10 kV electromechanical tether for TSS-1 using high impact conductor (Hiwire)

    NASA Technical Reports Server (NTRS)

    Scala, E.; Bentley, D. P.; Marshall, L. S.

    1986-01-01

    The development of a 20-km electromechanical tether for the tethered satellite system (TSS) is described. The basic design requirements for electromagnetic cables and for conductors in cables subject to stresses and cyclic loading are discussed. The tether fabricatioon procedures involve: (1) conductor twisting around the core, (2) insulation extrusion, (3) strength member braiding, and (4) protective jacket braiding.

  4. Modeling of tape tether vibration and vibration sensing using smart film sensors

    NASA Astrophysics Data System (ADS)

    Kunugi, Kouta; Kojima, Hirohisa; Trivailo, Pavel M.

    2015-02-01

    Tape-tethered satellite systems use long and flexible tape tethers, the bending and torsional vibrations of which affect the positions and attitude of attached satellites and climbers. Owing to the distribution characteristics of a tape tether, ordinary point sensors and actuators cannot be used easily to control the vibrations. Other types of sensors and actuators are required for this purpose. The flexibility and deformability of smart materials make them particularly suitable for integration into a tape-tethered system. Thus, in this paper, we propose a method for modeling the bending and torsional vibrations of a tape tether, and report our investigation into the feasibility of using smart film sensors to distinguish between the two vibration types. We formulate equations of motion for the tape tether using multibody dynamics techniques, and perform numerical simulations to study the behavior of the bending and torsional vibrations. The results of our experiments show that the bending and torsional vibrations of a tape tether can be measured using smart film sensors attached to the tether.

  5. Tethered balloon-based measurements of meteorological variables and aerosols

    NASA Technical Reports Server (NTRS)

    Sentell, R. J.; Storey, R. W.; Chang, J. J. C.; Jacobsen, S. J.

    1976-01-01

    Tethered balloon based measurements of the vertical distributions of temperature, humidity, wind speed, and aerosol concentrations were taken over a 4-hour period beginning at sunrise on June 29, 1976, at Wallops Island, Virginia. Twelve consecutive profiles of each variable were obtained from ground to about 500 meters. These measurements were in conjuction with a noise propagation study on remotely arrayed acoustic range (ROMAAR) at Wallops Flight Center. An organized listing of these vertical soundings is presented. The tethered balloon system configuration utilized for these measurements is described.

  6. The use of tethers for an artificial gravity facility

    NASA Technical Reports Server (NTRS)

    Lemke, L. G.; Mascy, A. F.; Swenson, B. L.

    1988-01-01

    The principles of operation and the design of the Artificial Gravity Research Facility (AGRF), which is a centrifuge to be constructed and operated for research and development purposes in a low-earth orbit, are examined, with particular attention given to the use of tethers for this facility. The differences and similarities between the AGRF and the previous artificial-gravity concepts are discussed in the framework of modern understanding of the effects of partial gravity and rotating environments on the human organism. The impact of tension-stiffened tethers on the system mass of the AGRF is examined, together with their effect on space operations and safety.

  7. Dynamics of multi-tethered pyramidal satellite formation

    NASA Astrophysics Data System (ADS)

    Alary, D.; Andreev, K.; Boyko, P.; Ivanova, E.; Pritykin, D.; Sidorenko, V.; Tourneur, C.; Yarotsky, D.

    2015-12-01

    This paper is devoted to the dynamics of a multi-tethered pyramidal satellite formation rotating about its axis of symmetry in the nominal mode. Whereas the combination of rotation and gravity-gradient forces is insufficient to maintain the mutual positions of satellites, they are assumed to be equipped with low-thrust rocket engines. We propose a control strategy that allows the stabilization of the nominal spin state and demonstrate the system's proper operation by numerically simulating its controlled motion. The discussed multi-tethered formations could be employed, for example, to provide co-location of several satellites at a slot in geostationary orbit.

  8. Jupiter, Tether, and Lenz's Law

    NASA Technical Reports Server (NTRS)

    Lee, Russell

    1999-01-01

    Jupiter has a large, complex, and intense magnetic field that is thought to arise from electrical currents in the rapidly spinning metallic hydrogen interior. The strong magnetic field can induce currents when the conductive tether is directed toward or away from Jupiter. The currents can be stored and used for both propulsion and power generation. Therefore, our spacecraft might be able to visit several Jovian moons or maintain in the orbit around Jupiter. In our future space traveling, we also can use this technical skill to travel to other planets without any fuel. First-year physics textbooks describe Lenz's Law in which current is induced in a conductor moving through a stationary magnetic field. A demonstration of induced current in a stationary conductor and moving magnetic field is described, which may have space-tether application.

  9. Electrodynamics of superconducting pnictide superlattices

    SciTech Connect

    Perucchi, A.; Pietro, P. Di; Capitani, F.; Lupi, S.; Lee, S.; Kang, J. H.; Eom, C. B.; Jiang, J.; Weiss, J. D.; Hellstrom, E. E.; Dore, P.

    2014-06-02

    It was recently shown that superlattices where layers of the 8% Co-doped BaFe{sub 2}As{sub 2} superconducting pnictide are intercalated with non superconducting ultrathin layers of either SrTiO{sub 3} or of oxygen-rich BaFe{sub 2}As{sub 2}, can be used to control flux pinning, thereby increasing critical fields and currents, without significantly affecting the critical temperature of the pristine superconducting material. However, little is known about the electron properties of these systems. Here, we investigate the electrodynamics of these superconducting pnictide superlattices in the normal and superconducting state by using infrared reflectivity, from THz to visible range. We find that multigap structure of these superlattices is preserved, whereas some significant changes are observed in their electronic structure with respect to those of the original pnictide. Our results suggest that possible attempts to further increase the flux pinning may lead to a breakdown of the pnictide superconducting properties.

  10. Two-Way Tether Gun

    NASA Technical Reports Server (NTRS)

    Sanger, George F.

    1994-01-01

    Safety-tether device enables crewmembers on spacecraft to retrieve crewmember drifting away from spacecraft. Alternatively, drifting crewmember who carries device uses it to grasp and return to spacecraft. Also used on Earth. For example, rescuer on vessel or pier uses it to retrieve and haul drowning or unconscious person to safety; drifting person or rescuer in water uses it to grasp and hold onto support.

  11. Label-free measurements of membrane tether thickness using optical tweezers combined with SLIM

    NASA Astrophysics Data System (ADS)

    Sarshar, Mohammad; Wong, Winson T.; Anvari, Bahman

    2015-03-01

    Various cellular activities such as motility, division, and endocytosis involve a change in the cell shape. The mechanical interactions between the cell membrane and cytoskeleton play an important role in regulating changes in the cell shape. Tether formation from cell membranes provides a technique to characterize the mechanical properties of cell membranes and membrane-cytoskeleton interactions. Accurate measurement of the nano-scale tether diameter is relevant to quantification of membrane tension, bending modulus, and adhesion energy of the membrane-cytoskeleton structure. We have integrated optical tweezers with quantitative phase imaging, based on spatial light interference microscopy (SLIM), to simultaneously form tethers from HEK-293 cells and measure their diameters. Tether thickness along the illumination axis was measured using the quantitative phase map of the sample, and the refractive index (RI) mismatch between the sample and the surrounding media. The RI of the tethers ranged from 1.354 to 1.368 (cell culture medium RI=1.337). Our SLIM imaging system provided a 38 nm resolution in tether thickness measurements. Tether diameter fluctuations of <100 nm were resolved on tethers that ranged between 600-900 nm in diameter. Our integrated platform also provides the ability to simultaneously manipulate and image cell organelles in a non-contact and marker-free manner at nanometer spatial resolution.

  12. Dynamics and stability of a tethered centrifuge in low earth orbit

    NASA Technical Reports Server (NTRS)

    Quadrelli, B. M.; Lorenzini, E. C.

    1992-01-01

    The three-dimensional attitude dynamics of a spaceborne tethered centrifuge for artificial gravity experiments in low earth orbit is analyzed using two different methods. First, the tethered centrifuge is modeled as a dumbbell with a straight viscoelastic tether, point tip-masses, and sophisticated environmental models such as nonspherical gravity, thermal perturbations, and a dynamic atmospheric model. The motion of the centrifuge during spin-up, de-spin, and steady-rotation is then simulated. Second, a continuum model of the tether is developed for analyzing the stability of lateral tether oscillations. Results indicate that the maximum fluctuation about the 1-g radial acceleration level is less than 0.001 g; the time required for spin-up and de-spin is less than one orbit; and lateral oscillations are stable for any practical values of the system parameters.

  13. Diffusive transport of molecular cargo tethered to a DNA origami platform.

    PubMed

    Kopperger, Enzo; Pirzer, Tobias; Simmel, Friedrich C

    2015-04-01

    Fast and efficient transport of molecular cargoes along tracks or on supramolecular platforms is an important prerequisite for the development of future nanorobotic systems and assembly lines. Here, we study the diffusive transport of DNA cargo strands bound to a supramolecular DNA origami structure via an extended tether arm. For short distances (on the order of a few nanometers), transport from a start to a target site is found to be less efficient than for direct transfer without tether. For distances on the scale of the origami platform itself, however, cargo transfer mediated by a rigid tether arm occurs very fast and robust, whereas a more flexible, hinged tether is found to be considerably less efficient. Our results suggest diffusive motion on a molecular tether as a highly efficient mechanism for fast transfer of cargoes over long distances. PMID:25739805

  14. Design and Test of a Tethered Pair of Satellites: Equipment Requirements

    NASA Technical Reports Server (NTRS)

    Pernicka, Henry J.; Leitner, Jesse (Technical Monitor)

    2003-01-01

    A recent development in spacecraft mission design involves the increasing use of Distributed Spacecraft Systems (DSS). Several key technologies must mature sufficiently to facilitate these missions, including the use of spacecraft flying in tightly controlled formations. Such formations may be controlled using "free flying" navigation schemes, or alternatively may use tethers to constrain the formation geometry. An investigation has been initiated here to further develop this technology using two small spacecraft connected by a short tether. After insertion into orbit, the tether will be extended and various data collected on the performance of the dual-spacecraft "formation." At some later time, the tether will be cut, and the spacecraft pair will be navigated in a manner to maintain a geometry as closely as possible to that of the tethered configuration. Comparisons and evaluations of the two modes of operation can then be made so that the merits of both approaches are available to mission designers.

  15. Dynamics of tethered versus free-swimming animals: A wake structure comparison in jellyfish

    NASA Astrophysics Data System (ADS)

    Katija, Kakani; Dabiri, John O.

    2006-11-01

    Previous research has shown that jellyfish utilize the formation and shedding of vortices to help feed and move the animal. Laboratory experiments often require restricting the motion of an animal by tethering/fluming to allow for repeatable results. However, past research has not addressed the differences that arise when the motion of an animal is restricted/confined. This presentation will attend to this issue by comparing the wake structure of a tethered and free-swimming Aurelia aurita. Digital Particle Image Velocimetry is used to collect measurements of the velocity field surrounding an animal that is either tethered or swimming freely. Dynamical systems methods are used to compute Lagrangian coherent structures (LCS), which is used to identify the geometries of structures in the wake of the animal. Using LCS, a comparison between the wake of a tethered and free-swimming animal can be made. This research provides a quantitative measure of the differences between a tethered and freely moving jellyfish.

  16. Covariant Electrodynamics in Vacuum

    NASA Astrophysics Data System (ADS)

    Wilhelm, H. E.

    1990-05-01

    The generalized Galilei covariant Maxwell equations and their EM field transformations are applied to the vacuum electrodynamics of a charged particle moving with an arbitrary velocity v in an inertial frame with EM carrier (ether) of velocity w. In accordance with the Galilean relativity principle, all velocities have absolute meaning (relative to the ether frame with isotropic light propagation), and the relative velocity of two bodies is defined by the linear relation uG = v1 - v2. It is shown that the electric equipotential surfaces of a charged particle are compressed in the direction parallel to its relative velocity v - w (mechanism for physical length contraction of bodies). The magnetic field H(r, t) excited in the ether by a charge e moving uniformly with velocity v is related to its electric field E(r, t) by the equation H=ɛ0(v - w)xE/[ 1 +w • (t>- w)/c20], which shows that (i) a magnetic field is excited only if the charge moves relative to the ether, and (ii) the magnetic field is weak if v - w is not comparable to the velocity of light c0 . It is remarkable that a charged particle can excite EM shock waves in the ether if |i> - w > c0. This condition is realizable for anti-parallel charge and ether velocities if |v-w| > c0- | w|, i.e., even if |v| is subluminal. The possibility of this Cerenkov effect in the ether is discussed for terrestrial and galactic situations

  17. Astronaut James Newman evaluates tether devices in Discovery's payload bay

    NASA Technical Reports Server (NTRS)

    1993-01-01

    Astronaut James H. Newman, mission specialist, uses a 35mm camera to take a picture of fellow astronaut Carl E. Walz (out of frame) in Discovery's cargo bay. The two were engaged in an extravehicular activity (EVA) to test equipment to be used on future EVA's. Newman is tethered to the starboard side, with the orbital maneuvering system (OMS) pod just behind him.

  18. Electrodynamics payloads for small rockets

    NASA Technical Reports Server (NTRS)

    Croskey, C. L.; Hale, L. C.; Mitchell, J. D.; Mccarthy, S. P.; Goodnow, K. J.; Li, C.; Goldberg, R. A.

    1992-01-01

    Totally integrated design facilitates electrical cleanliness and light weight, which are necessary in subsonic parachute-borne payloads for electrodynamics investigations. 'Blunt' probes measure ion conductivity, as do Gerdien condensers. Recent finite-element computer analyses combining flow and electrodynamics have resolved problems in determining ion densities and mobilities from Gerdien data. Three-axis electric fields are measured with deployable boom-mounted electrodes from dc through VLF. Splitting the cylindrical payload with an insulator and measuring the current between halves has provided a vertical Maxwell current detector mechanically rigid enough to measure, at ELF, energy related to coupling. A nose tip 'Smith' probe turbulence measurement is usually performed on ascent. Other instrumentation, such as photo-ionization sources and X-ray detectors, can also be included. These electrodynamic measurement payloads are about one meter in length and have a mass of about 9 kg. They can be launched with an Orion-class or smaller vehicle.

  19. Tethers as Debris: Hydrocode Simulation of Impacts of Polymer Tether Fragments on Aluminum Plates

    NASA Technical Reports Server (NTRS)

    Evans, Steven W.

    2003-01-01

    Tethers promise to find use in a variety of space applications. Despite being narrow objects, their great lengths result in them having large total areas. Consequently, tethers are very susceptible to being severed by orbital debris. Extensive work has been done designing tethers that resist severs by small debris objects, in order to lengthen their working lives. It is from this perspective that most recent work has considered the tether - debris question. The potential of intact tethers, or severed tether fragments, as debris, to pose a significant collision risk to other spacecraft has been less well studied. Understanding the consequences of such collisions is important in assessing the risks tethers pose to other spacecraft. This paper discusses the damage that polymer tethers may produce on aluminum plates, as revealed by hypervelocity impact simulations using the SPHC hydrodynamic code.

  20. Quantum electrodynamics effects on NMR magnetic shielding constants of He-like and Be-like atomic systems

    NASA Astrophysics Data System (ADS)

    Gimenez, Carlos A.; Kozioł, Karol; Aucar, Gustavo A.

    2016-03-01

    NMR shielding constants for He- and Be-like atomic systems of Ne, Ar, Kr, Xe, and Rn have been calculated at the random-phase-approximation level of approach, including an estimation of QED corrections within the polarization propagator formalism. We show that QED effects enhance electron correlation when Z becomes heavier, which happens with relativistic effects, and also that QED effects become smaller when going from more to less ionized systems. We studied two- and four-electron systems. Then such studies could easily be generalized to other many-electron systems. Results of calculations with our relatively simple model, which includes QED and electron correlation effects on the same theoretical grounds, have a summarized error in the range from 10% (for Ne) up to 24% (for Rn), so that our accuracy is a little lower than for calculations on H-like systems. Our findings should stimulate the development and/or the application of more rigorous formalisms to get more accurate QED corrections to response properties in many-electron systems.

  1. Time-dependent Kohn-Sham approach to quantum electrodynamics

    SciTech Connect

    Ruggenthaler, M.; Mackenroth, F.; Bauer, D.

    2011-10-15

    We prove a generalization of the van Leeuwen theorem toward quantum electrodynamics, providing the formal foundations of a time-dependent Kohn-Sham construction for coupled quantized matter and electromagnetic fields. We circumvent the symmetry-causality problems associated with the action-functional approach to Kohn-Sham systems. We show that the effective external four-potential and four-current of the Kohn-Sham system are uniquely defined and that the effective four-current takes a very simple form. Further we rederive the Runge-Gross theorem for quantum electrodynamics.

  2. Laboratory Scale Prototype of a Low-Speed Electrodynamic Levitation System Based on a Halbach Magnet Array

    ERIC Educational Resources Information Center

    Iniguez, J.; Raposo, V.

    2009-01-01

    In this paper we analyse the behaviour of a small-scale model of a magnetic levitation system based on the Inductrack concept. Drag and lift forces acting on our prototype, moving above a continuous copper track, are studied analytically following a simple low-speed approach. The experimental results are in good agreement with the theoretical…

  3. Analysis of ProSEDS Test of Bare-Tether Collection

    NASA Technical Reports Server (NTRS)

    Sanmartin, J. R.; Lorenzini, E. C.; Estes, R. D.; Charro, M.; Cosmo, M. L.

    2003-01-01

    NASA's tether experiment ProSEDS will be placed in orbit on board a Delta-II rocket to test bare-tether electron collection, deorbiting of the rocket second stage, and the system dynamic stability. ProSEDS performance will vary because ambient conditions change along the orbit and tether-circuit bulk elements at the cathodic end follow the step-by-step sequence for the current cycles of operating modes (open-circuit, shunt and resistor modes for primary cycles; shunt and battery modes for secondary cycles). In this work we discuss expected ProSEDS values of the ratio L,/L*, which jointly with cathodic bulk elements determines bias and current tether profiles; L, is tether length, and L* (changing with tether temperature and ionospheric plasma density and magnetic field) is a characteristic length gauging ohmic versus baretether collection impedances. We discuss how to test bare-tether electron collection during primary cycles, using probe measurements of plasma density, measurements of cathodic current in resistor and shunt modes, and an estimate of tether temperature based on ProSEDS orbital position at the particular cycle concerned. We discuss how a temperature misestimate might occasionally affect the test of bare-tether collection, and how introducing the battery mode in some primary cycles, for an additional current measurement, could obviate the need of a temperature estimate. We also show how to test bare-tether collection by estimating orbit-decay rate from measurements of cathodic current for the shunt and battery modes of secondary cycles.

  4. Path integral quantization of generalized quantum electrodynamics

    SciTech Connect

    Bufalo, R.; Pimentel, B. M.; Zambrano, G. E. R.

    2011-02-15

    In this paper, a complete covariant quantization of generalized electrodynamics is shown through the path integral approach. To this goal, we first studied the Hamiltonian structure of the system following Dirac's methodology and, then, we followed the Faddeev-Senjanovic procedure to obtain the transition amplitude. The complete propagators (Schwinger-Dyson-Fradkin equations) of the correct gauge fixation and the generalized Ward-Fradkin-Takahashi identities are also obtained. Afterwards, an explicit calculation of one-loop approximations of all Green's functions and a discussion about the obtained results are presented.

  5. Subclassical fields and polarization in electrodynamics

    SciTech Connect

    Planat, Mathieu; Polonyi, Janos

    2010-08-15

    Expectation values of the electromagnetic field and the electric current are introduced at space-time resolution which belongs to the quantum domain. These allow us to approach some key features of classical electrodynamics from the underlying QED. One is the emergence of the radiation field in the retarded solution of the Maxwell equation, derived from an action principle. Another question discussed is the systematic derivation of the polarizability of a charge system. Furthermore, the decoherence and the consistency of the photon field are established by a perturbative calculation of the reduced density matrix for the electromagnetic field within the closed time path formalism.

  6. Analytical investigation of the dynamics of tethered constellations in Earth orbit, phase 2

    NASA Technical Reports Server (NTRS)

    Lorenzini, E.; Arnold, D. A.; Grossi, M. D.; Gullahorn, G. E.

    1986-01-01

    The development of a two dimensional analytical model that describes the dynamics of an n-mass vertical tethered system is reported. Two different approaches are described: in the first one the control quantities are the independent variables while in the second one the Cartesian coordinates of each mass expressed in the orbiting reference frame are the independent variables. The latter model was used in the 3-mass version to simulate the dynamics of the tethered system in applications involving the displacement of the middle mass along the tether. In particular, issues related to reproducing predetermined acceleration profiles and g-tuning are reported.

  7. Topological vortices in generalized Born-Infeld-Higgs electrodynamics

    NASA Astrophysics Data System (ADS)

    Casana, R.; Hora, E. da; Rubiera-Garcia, D.; Santos, C. dos

    2015-08-01

    A consistent BPS formalism to study the existence of topological axially symmetric vortices in generalized versions of the Born-Infeld-Higgs electrodynamics is implemented. Such a generalization modifies the field dynamics via the introduction of three nonnegative functions depending only in the Higgs field, namely, , , and . A set of first-order differential equations is attained when these functions satisfy a constraint related to the Ampère law. Such a constraint allows one to minimize the system's energy in such way that it becomes proportional to the magnetic flux. Our results provides an enhancement of the role of topological vortex solutions in Born-Infeld-Higgs electrodynamics. Finally, we analyze a set of models entailing the recovery of a generalized version of Maxwell-Higgs electrodynamics in a certain limit of the theory.

  8. Engineering squeezed states of microwave radiation with circuit quantum electrodynamics

    SciTech Connect

    Li Pengbo; Li Fuli

    2011-03-15

    We introduce a squeezed state source for microwave radiation with tunable parameters in circuit quantum electrodynamics. We show that when a superconducting artificial multilevel atom interacting with a transmission line resonator is suitably driven by external classical fields, two-mode squeezed states of the cavity modes can be engineered in a controllable fashion from the vacuum state via adiabatic following of the ground state of the system. This scheme appears to be robust against decoherence and is realizable with present techniques in circuit quantum electrodynamics.

  9. Scattering Efficiency of High-Voltage Tethers in Space

    NASA Technical Reports Server (NTRS)

    Krivorutsky, E. N.; Khazanov, G. V.; Gamayunov, K. V.; Avanov, L. A.

    2005-01-01

    Several concepts have been proposed to remediate the effect of artificial Radiation Belts (RB) in Space Plasma. Among them is the high-voltage electrostatic tether remediation technique. Preliminary analysis that has been carried out later by several groups showed, that this technique could be very efficient and is able to control relativistic electron energies of artificial RB population. The relativistic electron population is the one of the most important topic of US Space Weather studies and very dangerous to many civilian and military space assets, it is also important to study some fundamentals of scattering efficiency of high-voltage tethers in space plasma. There are several fundamental issues that should be examined in order to validate high-voltage tether artificial RB remediation concept. The most critical among them are: power consumption, the size and stability of the plasma sheath around the tether, and scattering efficiency of this high-voltage system that is ultimately related with the plasma sheath size. This study would be focused on the scattering process itself and artificial RB remediation assuming that power consumption and the size of the plasma sheath are known.

  10. Sliding mode control of electromagnetic tethered satellite formation

    NASA Astrophysics Data System (ADS)

    Hallaj, Mohammad Amin Alandi; Assadian, Nima

    2016-08-01

    This paper investigates the control of tethered satellite formation actuated by electromagnetic dipoles and reaction wheels using the robust sliding mode control technique. Generating electromagnetic forces and moments by electric current coils provides an attractive control actuation alternative for tethered satellite system due to the advantages of no propellant consumption and no obligatory rotational motion. Based on a dumbbell model of tethered satellite in which the flexibility and mass of the tether is neglected, the equations of motion in Cartesian coordinate are derived. In this model, the J2 perturbation is taken into account. The far-field and mid-field models of electromagnetic forces and moments of two satellites on each other and the effect of the Earth's magnetic field are presented. A robust sliding mode controller is designed for precise trajectory tracking purposes and to deal with the electromagnetic force and moment uncertainties and external disturbances due to the Earth's gravitational and magnetic fields inaccuracy. Numerical simulation results are presented to validate the effectiveness of the developed controller and its superiority over the linear controller.

  11. Three dimensional dynamics of a flexible Motorised Momentum Exchange Tether

    NASA Astrophysics Data System (ADS)

    Ismail, N. A.; Cartmell, M. P.

    2016-03-01

    This paper presents a new flexural model for the three dimensional dynamics of the Motorised Momentum Exchange Tether (MMET) concept. This study has uncovered the relationships between planar and nonplanar motions, and the effect of the coupling between these two parameters on pragmatic circular and elliptical orbits. The tether sub-spans are modelled as stiffened strings governed by partial differential equations of motion, with specific boundary conditions. The tether sub-spans are flexible and elastic, thereby allowing three dimensional displacements. The boundary conditions lead to a specific frequency equation and the eigenvalues from this provide the natural frequencies of the orbiting flexible motorised tether when static, accelerating in monotonic spin, and at terminal angular velocity. A rotation transformation matrix has been utilised to get the position vectors of the system's components in an assumed inertial frame. Spatio-temporal coordinates are transformed to modal coordinates before applying Lagrange's equations, and pre-selected linear modes are included to generate the equations of motion. The equations of motion contain inertial nonlinearities which are essentially of cubic order, and these show the potential for intricate intermodal coupling effects. A simulation of planar and non-planar motions has been undertaken and the differences in the modal responses, for both motions, and between the rigid body and flexible models are highlighted and discussed.

  12. Transportation using spinning tethers with emphasis on phasing and plane change

    NASA Technical Reports Server (NTRS)

    Henderson, David G.

    1989-01-01

    This paper studies the potential uses of spinning tethers as components in a transportation system. Additional degrees of freedom in the selection of transfer orbits as well as phasing control are introduced by allowing both the spin rate of the tethers to be controllable and by allowing the ejection and capture points to be anywhere along the tether length. Equations are derived for the phasing of the planar transfer problem. A construction algorithm for nonplanar transfers is developed and nonplanar phasing conditions are examined.

  13. Tethers in space: Birth and growth of a new avenue to space utilization

    NASA Technical Reports Server (NTRS)

    Vontiesenhausen, G.

    1984-01-01

    The evolution of the ideas of tether applications in space are traced from its origin in the last century past a dormant period of sixty-five years to the mid-seventies. At that time as a consequence of major revival efforts, NASA entered into serious investigations of the theoretical and practical feasibility of a large number of tethered concepts in space. These efforts culminated in the establishment of the Tethered Satellite System Project now at NASA in the advanced development phase. Extensive planning efforts are described, first, through a Tether Applications in Space Workshop which generated additional concepts and provided overall assessments and recommendations to NASA, and then through a NASA inter-center Tether Applications in Space Task Group which generated a four year program plan in the areas of further studies, technology, work and science and applications of tethers in space. An outlook into the future of tether applications that approaches some of the goals of the early visionaries is offered.

  14. Apparent Paradoxes in Classical Electrodynamics: Relativistic Transformation of Force

    ERIC Educational Resources Information Center

    Kholmetskii, A. L.; Yarman, T.

    2007-01-01

    In this paper, we analyse a number of paradoxical teaching problems of classical electrodynamics, dealing with the relativistic transformation of force for complex macro systems, consisting of a number of subsystems with nonzero relative velocities such as electric circuits that change their shape in the course of time. (Contains 7 figures.)

  15. Autonomous Vision-Based Tethered-Assisted Rover Docking

    NASA Technical Reports Server (NTRS)

    Tsai, Dorian; Nesnas, Issa A.D.; Zarzhitsky, Dimitri

    2013-01-01

    Many intriguing science discoveries on planetary surfaces, such as the seasonal flows on crater walls and skylight entrances to lava tubes, are at sites that are currently inaccessible to state-of-the-art rovers. The in situ exploration of such sites is likely to require a tethered platform both for mechanical support and for providing power and communication. Mother/daughter architectures have been investigated where a mother deploys a tethered daughter into extreme terrains. Deploying and retracting a tethered daughter requires undocking and re-docking of the daughter to the mother, with the latter being the challenging part. In this paper, we describe a vision-based tether-assisted algorithm for the autonomous re-docking of a daughter to its mother following an extreme terrain excursion. The algorithm uses fiducials mounted on the mother to improve the reliability and accuracy of estimating the pose of the mother relative to the daughter. The tether that is anchored by the mother helps the docking process and increases the system's tolerance to pose uncertainties by mechanically aligning the mating parts in the final docking phase. A preliminary version of the algorithm was developed and field-tested on the Axel rover in the JPL Mars Yard. The algorithm achieved an 80% success rate in 40 experiments in both firm and loose soils and starting from up to 6 m away at up to 40 deg radial angle and 20 deg relative heading. The algorithm does not rely on an initial estimate of the relative pose. The preliminary results are promising and help retire the risk associated with the autonomous docking process enabling consideration in future martian and lunar missions.

  16. Three-dimensional multi-tethered satellite formation with the elements moving along Lissajous curves

    NASA Astrophysics Data System (ADS)

    Yarotsky, D.; Sidorenko, V.; Pritykin, D.

    2016-07-01

    This note presents a novel approach to maintain three-dimensional multi-tethered satellite formation in space. For a formation consisting of a main body connected by tethers with several deputy satellites (the so-called "hub-and-spoke" configuration) we demonstrate that under proper choice of the system's parameters the deputy satellites can move along Lissajous curves in the plane normal to the local vertical with all tethers stretched; the total force due to the tension forces acting on the main satellite is balanced in a way allowing it to be in relative equilibrium strictly below or strictly above the system's center of mass. We analyze relations between the system's essential parameters and obtain conditions under which the proposed motion does take place. We also study analytically the motion stability for different configurations and whether the deputy satellites can collide or the tethers can entangle. Our theoretical findings are corroborated and validated by numerical experiments.

  17. Three-dimensional multi-tethered satellite formation with the elements moving along Lissajous curves

    NASA Astrophysics Data System (ADS)

    Yarotsky, D.; Sidorenko, V.; Pritykin, D.

    2016-04-01

    This note presents a novel approach to maintain three-dimensional multi-tethered satellite formation in space. For a formation consisting of a main body connected by tethers with several deputy satellites (the so-called "hub-and-spoke" configuration) we demonstrate that under proper choice of the system's parameters the deputy satellites can move along Lissajous curves in the plane normal to the local vertical with all tethers stretched; the total force due to the tension forces acting on the main satellite is balanced in a way allowing it to be in relative equilibrium strictly below or strictly above the system's center of mass. We analyze relations between the system's essential parameters and obtain conditions under which the proposed motion does take place. We also study analytically the motion stability for different configurations and whether the deputy satellites can collide or the tethers can entangle. Our theoretical findings are corroborated and validated by numerical experiments.

  18. Carl Neumann's Contributions to Electrodynamics

    NASA Astrophysics Data System (ADS)

    Schlote, Karl-Heinz

    2004-09-01

    I examine the publications of Carl Neumann (1832 1925) on electrodynamics, which constitute a major part of his work and which illuminate his approach to mathematical physics. I show how Neumann contributed to physics at an important stage in its development and how his work led to a polemic with Hermann Helmholtz (1821 1894). Neumann advanced and extended the ideas of the Königsberg school of mathematical physics. His investigations were aimed at founding a mathematically exact physical theory of electrodynamics, following the approach of Carl G.J. Jacobi (1804 1851) on the foundation of a physical theory as outlined in Jacobi’s lectures on analytical mechanics. Neumann’s work also shows how he clung to principles that impeded him in appreciating and developing new ideas such as those on field theory that were proposed by Michael Faraday (1791 1867) and James Clerk Maxwell (1831 1879).

  19. Pyroshock testing-electrodynamic shakers

    NASA Astrophysics Data System (ADS)

    Smallwood, David O.

    2002-05-01

    Far field pyroshock (accelerations less than a few hundred grams, and bandwidths less than a few kHz) can be simulated on electrodynamic shakers. Typically, the specification is in terms of the shock response spectrum (SRS). Wave forms are synthesized which will match the required SRS. The process is not unique, as many wave forms can have essentially the same SRS. Sometimes additional restrictions are placed on the synthesized wave form. Most common are restrictions on the duration of the wave form. The process of synthesizing wave forms, which will match an SRS and conform to the limitations of electrodynamic shakers, will be described. The methods used to reproduce these wave forms on the shaker will then be discussed.

  20. Accelerator and electrodynamics capability review

    SciTech Connect

    Jones, Kevin W

    2010-01-01

    Los Alamos National Laboratory (LANL) uses capability reviews to assess the science, technology and engineering (STE) quality and institutional integration and to advise Laboratory Management on the current and future health of the STE. Capability reviews address the STE integration that LANL uses to meet mission requirements. The Capability Review Committees serve a dual role of providing assessment of the Laboratory's technical contributions and integration towards its missions and providing advice to Laboratory Management. The assessments and advice are documented in reports prepared by the Capability Review Committees that are delivered to the Director and to the Principal Associate Director for Science, Technology and Engineering (PADSTE). Laboratory Management will use this report for STE assessment and planning. LANL has defined fifteen STE capabilities. Electrodynamics and Accelerators is one of the seven STE capabilities that LANL Management (Director, PADSTE, technical Associate Directors) has identified for review in Fiscal Year (FY) 2010. Accelerators and electrodynamics at LANL comprise a blend of large-scale facilities and innovative small-scale research with a growing focus on national security applications. This review is organized into five topical areas: (1) Free Electron Lasers; (2) Linear Accelerator Science and Technology; (3) Advanced Electromagnetics; (4) Next Generation Accelerator Concepts; and (5) National Security Accelerator Applications. The focus is on innovative technology with an emphasis on applications relevant to Laboratory mission. The role of Laboratory Directed Research and Development (LDRD) in support of accelerators/electrodynamics will be discussed. The review provides an opportunity for interaction with early career staff. Program sponsors and customers will provide their input on the value of the accelerator and electrodynamics capability to the Laboratory mission.

  1. Instantaneous fields in classical electrodynamics

    NASA Astrophysics Data System (ADS)

    Heras, J. A.

    2005-01-01

    In this paper we express the retarded fields of Maxwell's theory in terms of the instantaneous fields of a Galilei-invariant electromagnetic and we find the vector function χL whose spatial and temporal derivatives transform the Euclidean fields into the retarded ones. We conclude that the instantaneous fields can formally be introduced as unphysical objects into classical electrodynamics which can be used to find the physical retarded fields.

  2. Failsafe multistrand tether structures for space propulsion

    NASA Astrophysics Data System (ADS)

    Forward, Robert L.

    1992-07-01

    The development of a circularly symmetric singly crosslinked multistrand space tether, named Hoytether, is reported. The Hoytether consists of a number of primary strands running the full length of the structure, with nearest neighbor primary strands crosslinked at intervals by secondary strands that are put under load only if a section of primary strand is cut by space debris. It has been demonstrated that a multistrand tether of the singly crosslinked Hoytether design can provide a long-lived failsafe multistrand replacement for a single-strand tether while imposing a minimal mass ratio penalty.

  3. Tethered Ozonesonde Measurements During FRAPPE July-August 2014

    NASA Astrophysics Data System (ADS)

    Oltmans, S. J.; Johnson, B.; Sterling, C. W.; Cullis, P.; Hall, E. G.; Jordan, A. F.; Wendell, J.; Schnell, R. C.; McClure-Begley, A.; Thompson, A. M.

    2015-12-01

    O3 and temperature profiles were measured from tethered ozonesondes from surface to 400 m above ground level on 9 days during the summer of 2014 Colorado Front Range Air Pollution and Photochemistry Experiment (FRAPPE). The portable tethered ozonesonde system was set up at one of 3 sites located next to a Colorado Department of Public Health and Environment surface monitoring station. The day and site chosen were based on the previous day O3 and weather forecast. Measurements typically began at 8:30 AM and ended at 4:30 PM, averaging 40 profiles in one day. The ozonesonde when sampling at the surface consistently read within 0-3 ppbv of the surface monitor at each of the sites with a typical daytime range of 20-90 ppbv. The hourly values were averaged at 50 meter intervals showing O3 production rates were consistently around 8 ppbv per hour from 50 to 300 meters above ground level. On sunny, light wind days the O3 mixing ratio reached a maximum of 80-90 ppbv between 14:00 and 15:00 local time. The generally constant mixing ratio with height and highest mixing ratios above the surface indicate that photochemical O3 production was taking place throughout the profile. Continuous O3 profiles from a tall tower (5 and 300 m) and daily ozonesondes tracked O3 variability through the experiment. High O3 at each site was associated with different local wind directions. At Ft. Collins winds were generally out of the southeast, at Chatfield from the northeast, and at City Park Golf Course more variable. The tether system was developed at NOAA/ESRL to provide a cost effective method to measure O3 profiles on a continuous basis. The tether system consisted of a deep sea fishing pole, electric motor driving the reel with light-weight fishing line attached to the balloon ozonesonde, a tether control box, and laptop. The in house software package monitored data and controlled the tether speed and turn-around point based on real time GPS altitude from the transmitting radiosonde.

  4. Tethers as Debris: Hydrocode Simulation of Impacts of Tether Fragments on Planar Aerospace Materials

    NASA Technical Reports Server (NTRS)

    Evans, Steven W.; Parker, Nelson C. (Technical Monitor)

    2002-01-01

    Tethers promise to find use in a variety of space applications. Despite being narrow objects, their great lengths result in them having large total areas, and so tethers are quite susceptible to being severed by orbital debris. Extensive work has been done designing tethers that resist severs by small debris objects, and hence have longer working lives. It is from this perspective that most recent work has considered the tether - debris question. The potential of intact tethers, or severed tether fragments, as debris to pose a significant collision risk to other spacecraft has been less well studied. Understanding the consequences of such encounters is important in assessing the risks to other spacecraft posed by tethers. In this paper I discuss the damage that two types of tethers may produce on planar aerospace materials, as revealed by hyper- velocity impact simulations using the SPHC hydrodynamic code. Tether types considered include a single nylon line and a complex design including metal wires. Target materials considered include the aluminum plates typically used in debris shielding, and solar panels.

  5. Phase behavior and complex crystal structures of self-assembled tethered nanoparticle telechelics.

    PubMed

    Marson, Ryan L; Phillips, Carolyn L; Anderson, Joshua A; Glotzer, Sharon C

    2014-01-01

    Motivated by growing interest in the self-assembly of nanoparticles for applications such as photonics, organic photovoltaics, and DNA-assisted designer crystals, we explore the phase behavior of tethered spherical nanoparticles. Here, a polymer tether is used to geometrically constrain a pair of nanoparticles creating a tethered nanoparticle "telechelic". Using simulation, we examine how varying architectural features, such as the size ratio of the two end-group nanospheres and the length of the flexible tether, affects the self-assembled morphologies. We demonstrate not only that this hybrid building block maintains the same phase diversity as linear triblock copolymers, allowing for a variety of nanoparticle materials to replace polymer blocks, but also that new structures not previously reported are accessible. Our findings imply a robust underlying ordering mechanism is common among these systems, thus allowing flexibility in synthesis approaches to achieve a target morphology. PMID:24641517

  6. Dynamics of Membrane Tethers Reveal Novel Aspects of Cytoskeleton-Membrane Interactions in Axons

    PubMed Central

    Datar, Anagha; Bornschlögl, Thomas; Bassereau, Patricia; Prost, Jacques; Pullarkat, Pramod A.

    2015-01-01

    Mechanical properties of cell membranes are known to be significantly influenced by the underlying cortical cytoskeleton. The technique of pulling membrane tethers from cells is one of the most effective ways of studying the membrane mechanics and the membrane-cortex interaction. In this article, we show that axon membranes make an interesting system to explore as they exhibit both free membrane-like behavior where the tether-membrane junction is movable on the surface of the axons (unlike many other cell membranes) as well as cell-like behavior where there are transient and spontaneous eruptions in the tether force that vanish when F-actin is depolymerized. We analyze the passive and spontaneous responses of axonal membrane tethers and propose theoretical models to explain the observed behavior. PMID:25650917

  7. Adaptive sliding mode control of tethered satellite deployment with input limitation

    NASA Astrophysics Data System (ADS)

    Ma, Zhiqiang; Sun, Guanghui

    2016-10-01

    This paper proposes a novel adaptive sliding mode tension control method for the deployment of tethered satellite, where the input tension limitation is taken into account. The underactuated governing equations of the tethered satellites system are firstly derived based on Lagrangian mechanics theory. Considering the fact that the tether can only resist axial stretching, the tension input is modelled as input limitation. New adaptive sliding mode laws are addressed to guarantee the stability of the tethered satellite deployment with input disturbance, meanwhile to eliminate the effect of the limitation features of the tension input. Compared with the classic control strategy, the newly proposed adaptive sliding mode control law can deploy the satellite with smaller overshoot of the in-plane angle and implement the tension control reasonably and effectively in engineering practice. The numerical results validate the effectiveness of the proposed methods.

  8. Tethered Test of Morpheus -- Innovation Day

    NASA Video Gallery

    Another tethered test of the Morpheus vertical test bed. This flight was on Innovation Day at Johnson Space Center. We had around 300 onlookers during this test. This test looked better than yester...

  9. Morpheus Tether Test #20 - Duration: 74 seconds.

    NASA Video Gallery

    Morpheus conducts another tethered test, August 3, 2012. Morpheus is a full spacecraft and rocket-powered lander, which demonstrates new green technology, as well as an autonomous landing and hazar...

  10. Morpheus Tether Test #15 - Duration: 85 seconds.

    NASA Video Gallery

    Morpheus conducts another tethered test, May 10, 2012. Morpheus is a full spacecraft and rocket-powered lander, which demonstrates new green technology, as well as an autonomous landing and hazard ...

  11. Morpheus Tether Test #16 - Duration: 44 seconds.

    NASA Video Gallery

    Morpheus conducts another tethered test, June 11, 2012. Morpheus is a full spacecraft and rocket-powered lander, which demonstrates new green technology, as well as an autonomous landing and hazard...

  12. Morpheus Tether Test #17 - Duration: 71 seconds.

    NASA Video Gallery

    Morpheus conducts another tethered test, June 18, 2012. Morpheus is a full spacecraft and rocket-powered lander, which demonstrates new green technology, as well as an autonomous landing and hazard...

  13. Tethers in space handbook, second edition

    NASA Technical Reports Server (NTRS)

    Penzo, Paul A. (Editor); Ammann, Paul W. (Editor)

    1989-01-01

    The Tethers in Space Handbook, Second Edition represents an update to the initial volume issued in September 1986. As originally intended, this handbook is designed to serve as a reference manual for policy makers, program managers, educators, engineers, and scientists alike. It contains information for the uninitiated, providing insight into the fundamental behavior of tethers in space. For those familiar with space tethers, it includes a summary of past and ongoing studies and programs, a complete bibliography of tether publications, and names, addresses, and phone numbers of workers in the field. Perhaps its most valuable asset is the brief description of nearly 50 tether applications which have been proposed and analyzed over the past 10 years. The great variety of these applications, from energy generation to boosting satellites to gravity wave detection is an indication that tethers will play a significant part in the future of space development. This edition of the handbook preserves the major characteristics of the original; however, some significant rearrangements and additions have been made. The first section on Tether Programs has been brought up to date, and now includes a description of TSS-2, the aerodynamic NASA/Italian Space Agency (ASI) mission. Tether Applications follows, and this section has been substantially rearranged. First, the index and cross-reference for the applications have been simplified. Also, the categories have changed slightly, with Technology and Test changed to Aerodynamics, and the Constellations category removed. In reality, tether constellations may be applicable to many of the other categories, since it is simply a different way of using tethers. Finally, to separate out those applications which are obviously in the future, a Concepts category has been added. A new section included here on Conference Summaries recognizes the fact that the tether community is growing internationally, and that meetings provide a means of

  14. Magnetic cleanliness verification approach on tethered satellite

    NASA Technical Reports Server (NTRS)

    Messidoro, Piero; Braghin, Massimo; Grande, Maurizio

    1990-01-01

    Magnetic cleanliness testing was performed on the Tethered Satellite as the last step of an articulated verification campaign aimed at demonstrating the capability of the satellite to support its TEMAG (TEthered MAgnetometer) experiment. Tests at unit level and analytical predictions/correlations using a dedicated mathematical model (GANEW program) are also part of the verification activities. Details of the tests are presented, and the results of the verification are described together with recommendations for later programs.

  15. Uses of tethered atmospheric research probes

    NASA Technical Reports Server (NTRS)

    Deloach, Richard

    1991-01-01

    In situ measurements in the lower thermosphere are rare because of the difficulty of reaching these altitudes with conventional instrument platforms. The emerging technology of tethered satellites as a means to probe these altitudes from above has matured to the point that a flight program is planned to verify the operational performance of a low-cost deployer mechanism for tethered satellites, and to demonstrate a basic understanding of the dynamics of tethered satellite deployment. With such operational developments at hand, it is appropriate to review some of the potential applications of tethered measurement platforms for acquiring in situ data in the upper atmosphere. This paper focuses on downward-deployed tethered satellite measurements of interest to atmospheric scientists and to hypersonic aerodynamicists, and discusses ways in which this technology may be able to support selected long-range research programs currently in progress or in various stages of pre-flight development. The intent is to illustrate for the potential user community some of the unique advantages of tethered measurement platform technology now under development, and to stimulate creative thinking about ways in which this new capability may be used in support of future research programs.

  16. Electrodynamic vibration supression

    NASA Astrophysics Data System (ADS)

    Behrens, Sam; Fleming, Andrew J.; Moheimani, S. O. R.

    2003-07-01

    This paper introduces electromagnetic shunt damping (EMSD) which is similar to piezoelectric shunt damping. EMSD has four major advantages over piezoelectric shunt damping; simple transducer manufacturing, smaller shunt voltages, long stroke and larger control forces. A novel single mode shunt control strategy is validated through experimentation on a simple electromagnetic mass spring damper system. Theoretical results are also presented.

  17. Saturn ring rendezvous mission utilizing a tethered sub-satellite

    NASA Technical Reports Server (NTRS)

    Bright, Larry E.

    1990-01-01

    By combining the advanced technologies of constant-thrust propulsion and space tethers in a planetary mission, it may be feasible to perform a complete radial and azimuthal survey of the Saturnian ring system from close range (about 10 km) in a period of some 300 days. Constant-thrust propulsion would provide the means of 'hovering' above the rings while simultaneously spiraling radially inward toward Saturn. Use of a tethered sub-satellite at a distance of 500-1000 km from the main spacecraft would permit an instrumented package to achieve a significant azimuthal angular rate relative to the rings. Exhaustive 360 deg azimuthal mapping at one or two selected distances from Saturn could be performed in a few tens of days.

  18. Tethered elevator: A unique opportunity for space processing

    NASA Technical Reports Server (NTRS)

    Monti, R.

    1986-01-01

    The latest fluid dynamic and material science experiments in the microgravity environment have emphasized the importance of the residual gravity level and of the g-jitter on fluid physics phenomena. The tethered elevator presents the possibility of providing variable g-levels (both steady and g-jitter) around a very low steady g-level (that can be realized when the elevator is near the center of mass of the space station-tether complex). When positioning a variable periodic oscillation to the payload a clean g-jitter disturbance can be obtained that would not be otherwise obtainable by other systems. These two possibilities make the elevator a facility to help resolve a number of still open questions that are preventing wider utilization of the space environment in the microgravity area.

  19. Some Considerations about Podolsky-Axionic Electrodynamics

    NASA Astrophysics Data System (ADS)

    Gaete, Patricio

    For a Podolsky-axionic electrodynamics, we compute the interaction potential within the structure of the gauge-invariant but path-dependent variables formalism. The result is equivalent to that of axionic electrodynamics from a new noncommutative approach, up to first-order in θ.

  20. Electrodynamics at the highest energies

    SciTech Connect

    Klein, Spencer R.

    2002-06-17

    At very high energies, the bremsstrahlung and pair production cross sections exhibit complex behavior due to the material in which the interactions occur. The cross sections in dense media can be dramatically different than for isolated atoms. This writeup discusses these in-medium effects, emphasizing how the cross section has different energy and target density dependencies in different regimes. Data from SLAC experiment E-146 will be presented to confirm the energy and density scaling. Finally, QCD analogs of the electrodynamics effects will be discussed.

  1. Quantum Electrodynamics for Vector Mesons

    SciTech Connect

    Djukanovic, Dalibor; Schindler, Matthias R.; Scherer, Stefan; Gegelia, Jambul

    2005-07-01

    Quantum electrodynamics for {rho} mesons is considered. It is shown that, at the tree level, the value of the gyromagnetic ratio of the {rho}{sup +} is fixed to 2 in a self-consistent effective quantum field theory. Further, the mixing parameter of the photon and the neutral vector meson is equal to the ratio of electromagnetic and strong couplings, leading to the mass difference M{sub {rho}}{sub {sup 0}}-M{sub {rho}}{sub {sup {+-}}}{approx}1 MeV at tree order.

  2. A model of nonlinear electrodynamics

    SciTech Connect

    Kruglov, S.I.

    2015-02-15

    A new model of nonlinear electrodynamics with two parameters is investigated. We also consider a model with one dimensional parameter. It was shown that the electric field of a point-like charge is not singular at the origin and there is the finiteness of the static electric energy of point-like charged particle. We obtain the canonical and symmetrical Belinfante energy–momentum tensors and dilatation currents. It is demonstrated that the dilatation symmetry and dual symmetry are broken in the models suggested. We have calculated the static electric energy of point-like particles.

  3. Space time neural networks for tether operations in space

    NASA Technical Reports Server (NTRS)

    Lea, Robert N.; Villarreal, James A.; Jani, Yashvant; Copeland, Charles

    1993-01-01

    A space shuttle flight scheduled for 1992 will attempt to prove the feasibility of operating tethered payloads in earth orbit. due to the interaction between the Earth's magnetic field and current pulsing through the tether, the tethered system may exhibit a circular transverse oscillation referred to as the 'skiprope' phenomenon. Effective damping of skiprope motion depends on rapid and accurate detection of skiprope magnitude and phase. Because of non-linear dynamic coupling, the satellite attitude behavior has characteristic oscillations during the skiprope motion. Since the satellite attitude motion has many other perturbations, the relationship between the skiprope parameters and attitude time history is very involved and non-linear. We propose a Space-Time Neural Network implementation for filtering satellite rate gyro data to rapidly detect and predict skiprope magnitude and phase. Training and testing of the skiprope detection system will be performed using a validated Orbital Operations Simulator and Space-Time Neural Network software developed in the Software Technology Branch at NASA's Lyndon B. Johnson Space Center.

  4. DNA-based patterning of tethered membrane patches

    PubMed Central

    Hughes, Laura D.; Boxer, Steven G.

    2013-01-01

    Solid-supported lipid bilayers are useful model systems for mimicking cellular membranes; however, the interaction of the bilayer with the surface can disrupt the function of integral membrane proteins and impede topological transformations such as membrane fusion. As a result, a variety of tethered or cushioned lipid bilayer architectures have been described, which retain the proximity to the surface, enabling surface-sensitive techniques, but physically distance the bilayer from the surface. We have recently developed a method for spatially separating a lipid bilayer from a solid support using DNA lipids. In this system, a DNA strand is covalently attached to a glass slide or SiO2 wafer, and giant unilamellar vesicles (GUVs) displaying the complement rupture to form a planar lipid bilayer tethered above the surface. However, the location of the patch is random, determined by where the DNA-GUV initially binds to its complement. To allow greater versatility and control, we sought a way to pattern tethered membrane patches. We present a method for creating spatially distinct tethered membrane patches on a glass slide using microarray printing. Surface-reactive DNA sequences are spotted onto the slide, incubated to covalently link the DNA to the surface, and DNA-GUVs patches are formed selectively on the printed DNA. By interfacing the bilayers with microfluidic flow cells, materials can be added on top of or fused into the membrane to change the composition of the bilayers. With further development, this approach would enable rapid screening of different patches in protein binding assays and would enable interfacing patches with electrical detectors. PMID:23992147

  5. Electrodynamic convection in silicon floating zones

    NASA Astrophysics Data System (ADS)

    Mühlbauer, A.; Erdmann, W.; Keller, W.

    1983-12-01

    Using a simplified Navier-Stokes equation it has been possible to compute the electrodynamic convection generated by a radio frequency coil field for the modern needle-eye float-zone growth of silicon. The calculated electrodynamic force in such a zone shows maximum values up to 11.7 N/cm 3 and generates flow velocities between 25 and 100 cm/s. As only superficial convection can be brought about by electrodynamic forces, the axial and radial dopant incorporation will not be influenced strongly. A comparison of electrodynamic forces with the other forces possibly causing flow in silicon floating zones shows that the electrodynamic forces exceed all other forces by several orders of magnitude.

  6. Formations of Tethered Spacecraft as Stable Platforms for Far IR and Sub-mm Astronomy

    NASA Technical Reports Server (NTRS)

    Quadrelli, Marco B.; Hadaegh, Fred Y.; Shao, Michael; Lorenzini, Enrico C.

    2004-01-01

    In this paper we describe current research in tethered formations for interferometry, and a roadmap to demonstrating the required key technologies via on-ground and in-orbit testing. We propose an integrated kilometer-size tethered spacecraft formation flying concept which enables Far IR and Sub-mm astronomy observations from space. A rather general model is used to predict the dynamics, control, and estimation performance of formations of spacecraft connected by tethers in LEO and deep space. These models include the orbital and tethered formation dynamics, environmental models, and models of the formation estimator/controller/commander. Both centralized and decentralized control/sensing/estimation schemes are possible, and dynamic ranges of interest for sensing/control are described. Key component/subsystem technologies are described which need both ground-based and in-orbit demonstration prior to their utilization in precision space interferometry missions using tethered formations. Defining an orbiting formation as an ensemble of orbiting spacecraft performing a cooperative task, recent work has demonstrated the validity of the tethering the spacecraft to provide both the required formation rigidity and satisfy the formation reconfiguration needs such as interferometer baseline control. In our concept, several vehicles are connected and move along the tether, so that to reposition them the connecting tether links must vary in length. This feature enables variable and precise baseline control while the system spins around the boresight. The control architecture features an interferometer configuration composed of one central combiner spacecraft and two aligned collector spacecraft. The combiner spacecraft acts as the formation leader and is also where the centralized sensing and estimation functions reside. Some of the issues analyzed with the model are: dynamic modes of deformation of the distributed structure, architecture of the formation sensor, and sources

  7. A numerical simulation of auroral ionospheric electrodynamics

    NASA Technical Reports Server (NTRS)

    Mallinckrodt, A. J.

    1985-01-01

    A computer simulation of auroral ionospheric electrodynamics in the altitude range 80 to 250 km has been developed. The routine will either simulate typical electron precipitation profiles or accept observed data. Using a model background ionosphere, ion production rates are calculated from which equilibrium electron densities and the Hall and Pedersen conductivities may be determined. With the specification of suitable boundary conditions, the entire three-dimensional current system and electric field may be calculated within the simulation region. The results of the application of the routine to a typical inverted-V precipitation profile are demonstrated. The routine is used to explore the observed anticorrelation between electric field magnitude and peak energy in the precipitating electron spectrum of an auroral arc.

  8. Study of selected tether applications in space, phase 3, volume 2

    NASA Technical Reports Server (NTRS)

    1986-01-01

    The results of a Phase 3 study of two Selected Tether Applications in Space (STAIS); deorbit of a Shuttle and launch of an Orbital Transfer Vehicle (OTV), both from the space station using a tether were examined. The study objectives were to: perform a preliminary engineering design, define operational scenarios, develop a common cost model, perform cost benefits analyses, and develop a Work Breakdown Structure (WBS). Key features of the performance analysis were to identify the net increases in effective Shuttle cargo capability if tethers are used to assist in the deorbit of Shuttles and the launching of the OTVs from the space station and to define deployer system designs required to accomplish these tasks. Deployer concepts were designed and discussed. Operational scenarios, including timelines, for both tethered and nontethered Shuttle and OTV operations at the space station were evaluated. A summary discussion of the Selected Tether Applications Cost Model (STACOM) and the results of the cost benefits analysis are presented. Several critical technologies needed to implement tether assisted deployment of payloads are also discussed. Conclusions and recommendations are presented.

  9. The mechanics of motorised momentum exchange tethers when applied to active debris removal from LEO

    NASA Astrophysics Data System (ADS)

    Caldecott, Ralph; Kamarulzaman, Dayangku N. S.; Kirrane, James P.; Cartmell, Matthew P.; Ganilova, Olga A.

    2014-12-01

    The concept of momentum exchange when applied to space tethers for propulsion is well established, and a considerable body of literature now exists on the on-orbit modelling, the dynamics, and also the control of a large range of tether system applications. The authors consider here a new application for the Motorised Momentum Exchange Tether by highlighting three key stages of development leading to a conceptualisation that can subsequently be developed into a technology for Active Debris Removal. The paper starts with a study of the on-orbit mechanics of a full sized motorised tether in which it is shown that a laden and therefore highly massasymmetrical tether can still be forced to spin, and certainly to librate, thereby confirming its possible usefulness for active debris removal (ADR). The second part of the paper concentrates on the modelling of the centripetal deployment of a symmetrical MMET in order to get it initialized for debris removal operations, and the third and final part of the paper provides an entry into scale modelling for low cost mission design and testing. It is shown that the motorised momentum exchange tether offers a potential solution to the removal of large pieces of orbital debris, and that dynamic methodologies can be implemented to in order to optimise the emergent design.

  10. The mechanics of motorised momentum exchange tethers when applied to active debris removal from LEO

    SciTech Connect

    Caldecott, Ralph; Kamarulzaman, Dayangku N. S.; Kirrane, James P.; Cartmell, Matthew P.; Ganilova, Olga A.

    2014-12-10

    The concept of momentum exchange when applied to space tethers for propulsion is well established, and a considerable body of literature now exists on the on-orbit modelling, the dynamics, and also the control of a large range of tether system applications. The authors consider here a new application for the Motorised Momentum Exchange Tether by highlighting three key stages of development leading to a conceptualisation that can subsequently be developed into a technology for Active Debris Removal. The paper starts with a study of the on-orbit mechanics of a full sized motorised tether in which it is shown that a laden and therefore highly massasymmetrical tether can still be forced to spin, and certainly to librate, thereby confirming its possible usefulness for active debris removal (ADR). The second part of the paper concentrates on the modelling of the centripetal deployment of a symmetrical MMET in order to get it initialized for debris removal operations, and the third and final part of the paper provides an entry into scale modelling for low cost mission design and testing. It is shown that the motorised momentum exchange tether offers a potential solution to the removal of large pieces of orbital debris, and that dynamic methodologies can be implemented to in order to optimise the emergent design.

  11. Biomimicry enhances sequential reactions of tethered glycolytic enzymes, TPI and GAPDHS.

    PubMed

    Mukai, Chinatsu; Gao, Lizeng; Bergkvist, Magnus; Nelson, Jacquelyn L; Hinchman, Meleana M; Travis, Alexander J

    2013-01-01

    Maintaining activity of enzymes tethered to solid interfaces remains a major challenge in developing hybrid organic-inorganic devices. In nature, mammalian spermatozoa have overcome this design challenge by having glycolytic enzymes with specialized targeting domains that enable them to function while tethered to a cytoskeletal element. As a step toward designing a hybrid organic-inorganic ATP-generating system, we implemented a biomimetic site-specific immobilization strategy to tether two glycolytic enzymes representing different functional enzyme families: triose phosphoisomerase (TPI; an isomerase) and glyceraldehyde 3-phosphate dehydrogenase (GAPDHS; an oxidoreductase). We then evaluated the activities of these enzymes in comparison to when they were tethered via classical carboxyl-amine crosslinking. Both enzymes show similar surface binding regardless of immobilization method. Remarkably, specific activities for both enzymes were significantly higher when tethered using the biomimetic, site-specific immobilization approach. Using this biomimetic approach, we tethered both enzymes to a single surface and demonstrated their function in series in both forward and reverse directions. Again, the activities in series were significantly higher in both directions when the enzymes were coupled using this biomimetic approach versus carboxyl-amine binding. Our results suggest that biomimetic, site-specific immobilization can provide important functional advantages over chemically specific, but non-oriented attachment, an important strategic insight given the growing interest in recapitulating entire biological pathways on hybrid organic-inorganic devices. PMID:23626684

  12. Electrodynamic radioactivity detector for microparticles

    NASA Astrophysics Data System (ADS)

    Ward, T. L.; Davis, E. J.; Jenkins, R. W., Jr.; McRae, D. D.

    1989-03-01

    A new technique for the measurement of the radioactive decay of single microparticles has been demonstrated. Although the experiments were made with droplets of order 20 μm in diameter, microparticles in the range 0.1-100 μm can be accommodated. An electrodynamic balance and combination light-scattering photometer were used to measure the charge-loss rate and size of a charged microsphere suspended in a laser beam by superposed ac and dc electrical fields. The charged particle undergoes charge loss in the partially ionized gas atmosphere which results from radioactive decay of 14C-tagged compounds, and the rate of charge loss is proportional to the rate of decay here. The charge on a particle was determined by measuring the dc voltage necessary to stably suspend the particle against gravity while simultaneously determining the droplet size by light-scattering techniques. The parameters which affect the operation of the electrodynamic balance as a radioactivity detector are examined, and the limits of its sensitivity are explored. Radioactivity levels as low as 120 pCi have been measured, and it appears that by reducing the background contamination inside our balance activity levels on the order of 10 pCi can be detected. This new technique has application in the measurement of activity levels and source discrimination of natural and man-made aerosols and smokes and is also useful for studies involving specifically labeled radio-chemical probes.

  13. Using orbital tethers to remediate geomagnetic radiation belts

    NASA Astrophysics Data System (ADS)

    Hudoba de Badyn, Mathias; Marchand, Richard; Sydora, Richard D.

    2016-02-01

    The Van Allen radiation belts pose a hazard to spacecraft and astronauts, and similar radiation belts around other planets pose a hazard to interplanetary probes. We discuss a method of remediating these radiation belts first proposed by Danilov and Vasilyev, and recently improved by Hoyt, Minor, and Cash, where a long, charged tether is placed in orbit inside a radiation belt. In this approach, an electric field of the tether scatters the belt particles into a pitch angle loss cone leading to absorption of the particles in the atmosphere. A test particle calculation is presented which computes the scattered pitch angle of belt particles as a function of initial pitch angle and gyrophase for different particle energies. The moments of the resulting distribution of scattered angle versus initial pitch angle are used to compute the number density of the belt as a function of time using a Fokker-Planck diffusion approximation. Finally, we use the characteristic timescales of scattering for particles of different energies to discuss the feasibility of using such a system of tethers as a long and short-term remediation solution.

  14. The Secret Life of Tethers: The Role of Tethering Factors in SNARE Complex Regulation.

    PubMed

    Dubuke, Michelle L; Munson, Mary

    2016-01-01

    Trafficking in eukaryotic cells is a tightly regulated process to ensure correct cargo delivery to the proper destination organelle or plasma membrane. In this review, we focus on how the vesicle fusion machinery, the SNARE complex, is regulated by the interplay of the multisubunit tethering complexes (MTC) with the SNAREs and Sec1/Munc18 (SM) proteins. Although these factors are used in different stages of membrane trafficking, e.g., Golgi to plasma membrane transport vs. vacuolar fusion, and in a variety of diverse eukaryotic cell types, many commonalities between their functions are being revealed. We explore the various protein-protein interactions and findings from functional reconstitution studies in order to highlight both their common features and the differences in their modes of regulation. These studies serve as a starting point for mechanistic explorations in other systems. PMID:27243006

  15. The Secret Life of Tethers: The Role of Tethering Factors in SNARE Complex Regulation

    PubMed Central

    Dubuke, Michelle L.; Munson, Mary

    2016-01-01

    Trafficking in eukaryotic cells is a tightly regulated process to ensure correct cargo delivery to the proper destination organelle or plasma membrane. In this review, we focus on how the vesicle fusion machinery, the SNARE complex, is regulated by the interplay of the multisubunit tethering complexes (MTC) with the SNAREs and Sec1/Munc18 (SM) proteins. Although these factors are used in different stages of membrane trafficking, e.g., Golgi to plasma membrane transport vs. vacuolar fusion, and in a variety of diverse eukaryotic cell types, many commonalities between their functions are being revealed. We explore the various protein-protein interactions and findings from functional reconstitution studies in order to highlight both their common features and the differences in their modes of regulation. These studies serve as a starting point for mechanistic explorations in other systems. PMID:27243006

  16. Architecture dependence of photon antibunching in cavity quantum electrodynamics

    NASA Astrophysics Data System (ADS)

    Bradford, Matthew; Shen, Jung-Tsung

    2015-08-01

    We investigate numerically the architecture dependence of the characteristics of antibunched photons generated in cavity quantum electrodynamic systems. We show that the quality of antibunching [the smallness of the second-order intensity correlation function at zero time g(2 )(0 ) ] and the generation efficiency significantly depend on the configurations: the arrangements of single-mode optical cavities and waveguides. We found that for certain class of architecture, when the Jaynes-Cummings system (the atom-cavity system) couples to two terminated waveguides, there exists a fundamental tradeoff between high transmission and low g(2 )(0 ) , and is sensitive to dissipation. We further show that optimal antibunching can be achieved in two alternative cavity quantum electrodynamic configurations operating in the dissipatively weak coupling regime such that the two-photon transmission can be two orders of magnitude higher for the same g(2 )(0 ) .

  17. Atmospheric electrodynamics in the U.S. - 1987-1990

    NASA Technical Reports Server (NTRS)

    Holzworth, R. H.

    1991-01-01

    Atmospheric electrodynamics research is summarized, focusing on three general areas: the ionosphere as a source for middle atmospheric electrodynamics, regional and global scale electrodynamics, and thunderstorms and lightning. New or improved instrumentation techniques which have furthered atmospheric electrodynamics research are also discussed.

  18. Electrodynamic studies of upper and lower atmospheric coupling

    NASA Technical Reports Server (NTRS)

    Chiu, Y. T.; Cornwall, J. M.; Edgar, B. C.; Schulz, M.; Sharp, L. R.

    1981-01-01

    Theoretical interprotations and data interpretations of electrodynamical studies in upper and lower atmosphere coupling are reported. The following topics are discussed: (1) magnetosphere/ionosphere/atmosphere coupling in auroral electrodynamics; (2) middle atmosphere electrodynamics; (3) thermosphere troposphere coupling; and (4) tropospheric electrodynamics. Understanding of the near Earth space environment shows the interrelationships between various components of the Earth's atmosphere.

  19. Atmospheric electrodynamics in the U. S. - 1987-1990

    SciTech Connect

    Holzworth, R.H. )

    1991-01-01

    Atmospheric electrodynamics research is summarized, focusing on three general areas: the ionosphere as a source for middle atmospheric electrodynamics, regional and global scale electrodynamics, and thunderstorms and lightning. New or improved instrumentation techniques which have furthered atmospheric electrodynamics research are also discussed. 93 refs.

  20. Electrodynamics of ionospheric weather over low latitudes

    NASA Astrophysics Data System (ADS)

    Abdu, Mangalathayil Ali

    2016-12-01

    The dynamic state of the ionosphere at low latitudes is largely controlled by electric fields originating from dynamo actions by atmospheric waves propagating from below and the solar wind-magnetosphere interaction from above. These electric fields cause structuring of the ionosphere in wide ranging spatial and temporal scales that impact on space-based communication and navigation systems constituting an important segment of our technology-based day-to-day lives. The largest of the ionosphere structures, the equatorial ionization anomaly, with global maximum of plasma densities can cause propagation delays on the GNSS signals. The sunset electrodynamics is responsible for the generation of plasma bubble wide spectrum irregularities that can cause scintillation or even disruptions of satellite communication/navigation signals. Driven basically by upward propagating tides, these electric fields can suffer significant modulations from perturbation winds due to gravity waves, planetary/Kelvin waves, and non-migrating tides, as recent observational and modeling results have demonstrated. The changing state of the plasma distribution arising from these highly variable electric fields constitutes an important component of the ionospheric weather disturbances. Another, often dominating, component arises from solar disturbances when coronal mass ejection (CME) interaction with the earth's magnetosphere results in energy transport to low latitudes in the form of storm time prompt penetration electric fields and thermospheric disturbance winds. As a result, drastic modifications can occur in the form of layer restructuring (Es-, F3 layers etc.), large total electron content (TEC) enhancements, equatorial ionization anomaly (EIA) latitudinal expansion/contraction, anomalous polarization electric fields/vertical drifts, enhanced growth/suppression of plasma structuring, etc. A brief review of our current understanding of the ionospheric weather variations and the