Science.gov

Sample records for electrodynamic tether system

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. Numerical simulations of the electrodynamic interactions between the Tethered-Satellite-System and space plasma

    NASA Technical Reports Server (NTRS)

    Vashi, Bharat I.

    1992-01-01

    The first Tethered-Satellite-System (TSS-1), scheduled for a flight in late 1992, is expected to provide relevant information related to the concept of generating an emf in a 20-km-long (or longer) conducting wire. This paper presents numerical simulations of the electrodynamic interactions between the TSS system and space plasma, using a 2D and 3D models of the system. The 2D case code simulates the motion of a long cylinder past a plasma, which is composed of electrons and H(+) ions. The system is solved by allowing the plasma to flow past the cylinder with an imposed magnetic field. The more complex 3D case is considered to study the dynamics in great detail. Results of 2D simulation show that the interaction of a satellite with plasma flowing perpendicularly to the magnetic field results in an enhancement in the current collection.

  13. 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.

  14. 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.

  15. 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

  16. Electrodynamic tethers for energy conversion

    NASA Technical Reports Server (NTRS)

    Nobles, W.

    1986-01-01

    Conductive tethers have been proposed as a new method for converting orbital mechanical energy into electrical power for use on-board a satellite (generator mode) or conversely (motor mode) as a method of providing electric propulsion using electrical energy from the satellite. The operating characteristics of such systems are functionally dependent on orbit altitude and inclination. Effects of these relationships are examined to determine acceptable regions of application. To identify system design considerations, a specific set of system performance goals and requirements are selected. The case selected is for a 25 kW auxiliary power system for use on Space Station. Appropriate system design considerations are developed, and the resulting system is described.

  17. 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.

  18. 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.

  19. Electrodynamic Tethers for Reboost of the International Space Station

    NASA Technical Reports Server (NTRS)

    Johnson, Les; Herrmann, Melody; Vas, Irwin; Estes, Bob

    1999-01-01

    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. The system also has direct application to spacecraft and upper stage propulsion. Electrodynamic tethers have been demonstrated in space previously with the Plasma Motor Generator (PMG) experiment and the Tethered Satellite System (TSS-IR). The advanced electrodynamic tether proposed for ISS reboost has significant advantages over previous systems in that hi-her thrust is achievable with significantly shorter tethers and without the need for an active current collection device, hence making the system simpler and much less expensive.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

    The possibility of using electrodynamic forces to control pendular oscillations during the retrieval of a subsatellite is investigated. The use of the tether for transferring payloads between orbits is studied.

  5. High voltage characteristics of the electrodynamic tether and the generation of power and propulsion

    NASA Technical Reports Server (NTRS)

    Williamson, P. R.

    1986-01-01

    The Tethered Satellite System (TSS) will deploy and retrieve a satellite from the Space Shuttle orbiter with a tether of up to 100 km in length attached between the satellite and the orbiter. The characteristics of the TSS which are related to high voltages, electrical currents, energy storage, power, and the generation of plasma waves are described. A number of specific features of the tether system of importance in assessing the operational characteristics of the electrodynamic TSS are identified.

  6. Electrodynamic aspects of the first tethered satellite mission

    SciTech Connect

    Dobrowolny, M.; Melchioni, E.

    1993-08-01

    They authors provide a brief review of the physics basis for the tethered satellite program whose development began in 1984. They describe the electrodynamic effects which can be seen or induced by means of a conducting tether orbiting through the ionosphere. They also describe the first mission, in terms of the equipment, mission objective, and the actual experiment launched in July 1992.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. Hollow cathode-based plasma contactor experiments for electrodynamic tether

    NASA Astrophysics Data System (ADS)

    Patterson, Michael J.

    1987-01-01

    The role plasma contactors play in effective electrodynamic tether operation is discussed. Hollow cathodes and hollow cathode-based plasma sources have been identified as leading candidates for the electrodynamic tether plasma contactor. Present experimental efforts to evaluate the suitability of these devices as plasma contactors are reviewed. This research includes the definition of preliminary plasma contactor designs, and the characterization of their operation as electron collectors from a simulated space plasma. The discovery of an 'ignited mode' regime of high contactor efficiency and low impedance is discussed, as well as is the application of recent models of the plasma coupling process to contactor operation. Results indicate that ampere-level electron currents can be exchanged between hollow cathode-based plasma contactors and a dilute plasma in this regime. A discussion of design considerations for plasma contactors is given which includes expressions defining the total mass flow rate and power requirements of plasma contactors operating in both the cathodic and anodic regimes, and correlation of this to the tether current. Finally, future ground and spaceflight experiments are proposed to resolve critical issues of plasma contactor operation.

  20. 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.

  1. Tethered satellite systems - Technology of the future? Results of the study 'Long-term applications of tethered systems in orbit' (LASSO)

    NASA Astrophysics Data System (ADS)

    Seboldt, Wolfgang

    1992-08-01

    Possible future applications of tethered satellite systems are examined. The physics of electrodynamic tether systems is reviewed and the use of such tethers in energy provision and propulsion is addressed. The uses of electrically nonconducting tethers in geophysical studies and research of the sun, microgravity, aerothermodynamics, and meteorology and their possible role in space transport are considered.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Tether crawler system

    NASA Technical Reports Server (NTRS)

    Swanson, Frank R.

    1986-01-01

    A crawler system is designed to move a low-g/variable-g laboratory module along a tether between the Space Station and an attached space platform. An analysis is made of the effects of control law parameter change on the displacement, velocity, and acceleration of the crawler system. The control law is then modified by the addition of a constant-velocity section and the values of distance traveled, velocity, and acceleration are analyzed as a function of time. The power and torque equations are derived for a crawler system moving along a tether in orbit and numerical values of power and torque required for each prescribed movement are calculated versus time for four different cases using the control laws. A two-step control sequence is selected to permit initial location along the tether by distance traveled, followed by a vernier movement to reach the final desired constant net acceleration level. The components for the control system are identified and arranged in a block disgram configuration. The support subsystems are also identified. The sections were integrated to develop a procedure for the determination of crawler system performance requirements and the initial design of tether crawler systems.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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

  20. Investigation of the current collected by a positively biased satellite with application to electrodynamic tethers

    NASA Astrophysics Data System (ADS)

    Janeski, John A.; Scales, Wayne A.; Hall, Christopher D.

    2014-09-01

    The interaction between a positively biased body traveling through an ionospheric space plasma has direct application to electrodynamic tether (EDT) systems. A 2-D3v particle-in-cell model has been developed to study the plasma dynamics near a positively charged EDT system end-body and their impact on the current collected. The results show that the azimuthal current structures observed during the reflight of the tethered satellite system (TSS-1R) mission develop in the simulations and are found to enhance the current collected by the satellite by 67% when the magnetic field is ˜15° off of perpendicular to the orbital velocity. As the component of the magnetic field in the simulation's plane increases, the electrons are not able to easily cross the field lines causing plasma lobes to form in the +y and -y regions around the satellite. The lobes limit the current arriving at the satellite and also cause an enhanced wake to develop. A high satellite bias causes a stable bow shock structure to form in the ram region of the satellite, which limits the number of electrons entering the sheath region and thus limits the current collected. Electron-neutral collisions are found to destabilize the bow shock structure, and its current limiting effects were negated. Analytical curve fits based on the simulations are presented in order to characterize the dependence of the current collected on the magnetic field's orientation, space plasma magnetization, and satellite potential. The variations in the collected current induced by space plasma environmental changes may introduce new instabilities in an EDT system's dynamics.

  1. Are de-orbiting missions possible using electrodynamic tethers? Task review from the space debris perspective

    NASA Astrophysics Data System (ADS)

    Pardini, Carmen; Hanada, Toshiya; Krisko, Paula H.; Anselmo, Luciano; Hirayama, Hiroshi

    2007-05-01

    Over 9000 satellites and other trackable objects are currently in orbit around the Earth, along with many smaller particles. As the low Earth orbit is not a limitless resource, some sort of debris mitigation measures are needed to solve the problem of unusable satellites and spent upper stages. De-orbiting devices based on the use of conducting tethers have been recently proposed as innovative solutions to mitigate the growth of orbital debris. However, electrodynamic tethers introduce unusual problems when viewed from the space debris perspective. In particular, because of their small diameter, tethers of normal design may have a high probability of being severed by impacts with relatively small meteoroids and orbital debris. This paper compares the results obtained at ISTI/CNR, the Kyushu University and NASA/JSC concerning the vulnerability to debris impacts on a specific conducting tether able to de-orbit spacecraft in inclinations up to 75∘ and initial altitude less than 1400 km. A double line tether design has been analyzed, in addition to the single wire solution, in order to reduce the tether vulnerability. The results confirm that the survivability concern is fully justified for a single line tether and no de-orbit mission, from the altitudes and inclinations considered, is possible if the tether diameter is smaller than a few millimeters. The survival probability is shown to grow for a double line configuration with a sufficiently high number of knots and loops. The results are strongly dependent on the environment model adopted and the MASTER-2001 orbital debris and meteoroids fluxes result in survival probabilities appreciably higher than those of ORDEM2000 coupled with the Grün meteoroids model.

  2. 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.

  3. Tethered Satellite System control system design

    NASA Technical Reports Server (NTRS)

    Tomlin, Donald D.; Mowery, David K.; Bodley, Carl S.

    1989-01-01

    This paper discusses the control aspects of the Tethered Satellite System mission. The deployer controls system uses length-error and tension-error feedback to control in-plane libration, length, and length rate. The satellite's reaction control system is used to augment tether tension, control rates and attitude about the tether axis, and to damp in-plane and out-of-plane libration. The orbiter's reaction control system is also used to control in-plane and out-of-plane libration. Results of simulations are presented for the flight portion of the Tethered Satellite System mission.

  4. Tethering a new technology

    NASA Technical Reports Server (NTRS)

    Stone, Nobie H.; Candidi, Maurizio

    1993-01-01

    In a tethered-satellite system, two satellites travelling in different orbits are forced to circle the earth in the same time period. The lower satellite is dragged by the tether to a higher orbital speed, while the upper one tends to move higher. This generates a tension which maintains the system in a stable configuration; the tether is aligned with a radius projecting outward from the earth's center. Such a system has been demonstrated by the TSS-1 tethered satellite carried by the Space Shuttle's STS-46 mission. The dynamic and the electrodynamic behavior of the system at long tether lengths were not, however, evaluated due to system malfunctions.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  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. 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.

  13. 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.

  14. Dynamics and control of multibody tethered systems

    NASA Astrophysics Data System (ADS)

    Kalantzis, S.; Modi, V. J.; Pradhan, S.; Misra, A. K.

    The equations of motion for a multibody tethered satellite system in a three dimensional Keplerian orbit are derived. The model considers a multi-satellite system connected in series by flexible tethers. Both tethers and subsatellites are free to undergo three dimensional attitude motion, together with longitudinal and transverse vibration for the tether. The elastic deformations of the tethers are discretized using the assumed-mode method. In addition, the tether attachment points to the subsatellites are kept arbitrary and time varying, with deployment and retrieval degrees of freedom. The governing equations of motion are derived using an Order ( N) Lagrangian formulation. Next, two independent controllers, i.e. an attitude and vibration controller, are designed to regulate the rigid and flexible motion present in the system, excited from various maneuvres performed during the course of a mission. The former controller utilizes the thrusters and momentum-wheels located on the rigid satellites with a control algorithm based on the feedback linearization technique. On the other hand, the latter is designed using the robust linear quadratic Gaussian-loop transfer recovery method actuating the variable tether attachment point, or offset position. Both controllers are successful in suppressing unwanted disturbances in the system in a acceptable amount of time.

  15. 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.

  16. 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.

  17. 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

  18. Membrane Tethering Complexes in the Endosomal System.

    PubMed

    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

  19. 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.

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

    NASA Astrophysics Data System (ADS)

    Chapel, Jim D.; Flanders, Howard

    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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Gravity gradient determination with tethered systems

    NASA Technical Reports Server (NTRS)

    Kalaghan, P. M.; Colombo, G.

    1978-01-01

    A detailed investigation of the Earth's gravity field is needed for application to modern solid earth and oceanic investigations. The use of gravity gradiometers presents a technique to measure the intermediate wavelength components of the gravity field. One configuration of a gradiometer involves a tethered pair of masses orbiting the Earth and stabilized by vertical gravity gradient of the earth. A mesurement of the tension in such a system, called the DUMBBELL system is described. It allows the determination of the vertical gradient of the anomalous component of the Earth's gravtiy field. Preliminary analysis of the dynamics, mechanization, expected signal levels and noise environment indicates that the Dumbbell system is feasible.

  9. 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.

  10. 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.

  11. 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.

  12. Control Scheme of Tether Drag Deorbit System in Orbital Plane

    NASA Astrophysics Data System (ADS)

    Cui, Wei-Dong; Sun, Liang; Zhao, Guo-Wei

    In this paper, based on a dumbbell model of tethered satellite, a tension control scheme and a thrust control scheme of tether drag deorbit system in orbital plane are respectively proposed. In the tension control scheme, the tether tension can be measured by tension sensor and controlled by adjusting the tether length with a certain windlass mechanism, so that the librational angles could track the expected value; meanwhile, the tether could come back to the initial value. Because of the windlass mechanism, the slackness of tether can be avoided. In the thrust control scheme, the tether drag deorbit system is with a short tether in orbital maneuvering and the thrust acceleration imposed on the base satellite can be adjusted to avoid the slackness of tether and damp out the librational angles; besides, it is required that the regulation value of thrust acceleration meets with accuracy trajectory in practical engineering. Afterwards, a reasonable deorbit case of an abandoned GEO satellite is studied, in which the control of base satellite is considered; then, the advantages and disadvantages of two control schemes are analyzed and an improved control strategy is given. Numerical simulation results indicate that the slackness of tether can be eliminated and the librational angles are damped out according to the designed controllers, and the stability of the attitude of abandoned satellite is also guaranteed during flight. The proposed control schemes are feasible, which is useful for the flight safety.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Theory of plasma contractors for electrodynamic tethered satellite systems

    NASA Technical Reports Server (NTRS)

    Parks, D. E.; Katz, I.

    1986-01-01

    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.

  20. 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.

  1. 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.

  2. Operational complexities of real tether systems in space

    NASA Technical Reports Server (NTRS)

    Hoffman, Jeffrey A.

    1989-01-01

    Some of the major operational concerns that have to be addressed in planning a real tether mission, such as the TTS-1 mission, which is due to fly on the Space Shuttle in the early 1990's, are discussed. Specifically, several operational hazards, such as the tether reel overtorque and the loss of tether system control, are considered from the viewpoint of flight crew, who must be able to detect the presence of a problem and to determine the corrective action to be taken. Various safety measures are discussed.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. Development of the Flight Tether for ProSEDS

    NASA Technical Reports Server (NTRS)

    Curtis, Leslie; Vaughn, Jason; Welzyn, Ken; Carroll, Joe; Brown, Norman S. (Technical Monitor)

    2002-01-01

    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 11 Expendable Launch Vehicle second stage. ProSEDS will use the flight-proven Small Expendable Deployer System to deploy a newly designed and developed tether which will provide tether generated drag thrust of approx. 0.4 N. The development and production of very long tethers with specific properties for performance and survivability will be required to enable future tether missions. The ProSEDS tether design and the development process may provide some lessons learned for these future missions. The ProSEDS system requirements drove the design of the tether to have three different sections of tether each serving a specialized purpose. The tether is a total of 15 kilometers long: 10 kilometers of a non-conductive Dyneema lead tether; 5 km of CCOR conductive coated wire; and 220 meters of insulated wire with a protective Kevlar overbraid. Production and joining of long tether lengths involved many development efforts. Extensive testing of tether materials including ground deployment of the full-length ProSEDS tether was conducted to validate the tether design and performance before flight.

  9. Dynamics and stability of spinning flexible space tether systems

    NASA Astrophysics Data System (ADS)

    Tyc, George

    This dissertation focuses on a detailed dynamical investigation of a previously unexplored tether configuration that involves a spinning two-body tethered system with flexible appendages on each end-body where the spin axis is nominally aligned along the tether. The original motivation for this work came after the flight of the first Canadian sub-orbital tether mission OEDIPUS-A in 1989 which employed this spinning tethered configuration. To everyone's surprise, one of the end-bodies was observed to exhibit a rapid divergence of its nutation angle. It was clear after this flight that there were some fundamental mechanisms associated with the interaction between the tether and the end-body that were not fully understood at that time. Hence, a Tether Dynamics Experiment (TDE) was formed and became a formal part of the scientific agenda for the follow-on mission OEDIPUS-C which flew in 1995. This dissertation describes the work that was conducted as part of the TDE and involves: theoretical investigations into the dynamics of this spinning tethered flexible body system; ground testing to validate the models and establish the tether properties; application of the models to develop a stabilization approach for OEDIPUS-C, and comparisons between theory and flight data from both OEDIPUS-A and OEDIPUS-C. Nonlinear equations of motion are developed for a spinning tethered system where the tether could be either spinning with the end-bodies or attached to small de-spun platforms on the end-bodies. Since the tether used for the OEDIPUS missions is not a string, as is often assumed, but rather a wire that has some bending stiffness, albeit small, the tether bending was also taken into account in the formulation. Two sets of ground tests are described that were used to validate the stability conditions and gain confidence in the mathematical models. One set involved hanging a body by a tether and spinning at different speeds to investigate the end-body stability. The other set

  10. The study of the use of tethers for payload orbital transfer. Continuation of investigation of electrodynamic stabilization and control of long orbiting tethers

    NASA Technical Reports Server (NTRS)

    Colombo, G.

    1983-01-01

    The algorithm used in the reel maneuver was refined so as to develop a workable pre-release maneuver with particular emphasis on accounting for propagation delay and the dynamics of the tether itself in order to release the payload with no loss of tension along the wire.

  11. 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. .

  12. 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.

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1994-05-01

    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.

  15. 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.

  16. Interactions of a tethered satellite system with the ionosphere

    NASA Technical Reports Server (NTRS)

    Grossi, M. D.; Colombo, G.

    1978-01-01

    The Tethered Satellite System will be the first large structure deployed in space. It will react strongly with the magneto-ionic medium of the Earth's ionosphere and will thus be valuable experimental tool. Experiments planned for the structure are discussed. Emphasis is placed on the structures ability to excite a large variety of wave phenomena in the ionosphere using its electromotive force.

  17. Numerical and Experimental Approaches on the Motion of a Tethered System

    NASA Astrophysics Data System (ADS)

    Takehara, Shoichiro; Terumichi, Yoshiaki; Nohmi, Masahiro; Sogabe, Kiyoshi

    In the present paper, the motion of a tethered system with large deformation and large displacement is discussed. In general, a tether is a cable or a wire rope, and a tethered system consists of a tether and the equipment attached to the tether. A tethered subsatellite in space is an example of a tethered system. In the present study, a tethered system consisting of a very flexible body (the tether) and a rigid body at one end is considered as the analytical model. A flexible body in planer motion is described using the Absolute Nodal Coordinate Formulation. Using this formulation, the motion of a flexible body with large deformation, rotation and translation can be expressed with the accuracy of rigid body motion. The combination of the flexible body motion and the rigid body motion is performed, and their interaction is discussed. Experiments are performed to investigate the fundamental motion of the tethered system and to evaluate the validity of the numerical formulation. Experiments were conducted using a steel tether and a rubber tether in gravity space. In addition, an experiment of the motion of the tethered system with a rigid body in microgravity space was conducted.

  18. Space tethers for science in the space station era; Proceedings of the Second International Conference, Venice, Italy, Oct. 4-8, 1987

    NASA Technical Reports Server (NTRS)

    Guerriero, Luciano (Editor); Bekey, Ivan (Editor)

    1988-01-01

    Various papers on space tethers are presented. The general topics addressed include: the space program context for tethers, early experimental validation of tethers, tether dynamics simulations, electrodynamics aspects of tethers, and tethers for science and innovative uses. Also considered are: tethers in space, tether dynamics, tethers on stations and platforms, and tether technology.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Future geodesy missions: Tethered systems and formation flying

    NASA Astrophysics Data System (ADS)

    Fontdecaba, Jordi; Sanjurjo, Manuel; Pelaez, Jesus; Metris, Gilles; Exertier, Pierre

    Recent gravity field determination missions have shown the possibility of improving our Earth knowledge from space. GRACE has helped to the determination of temporal variations of low and mean degrees of the field while GOCE will improve the precision in the determination of higher degrees. But there is still some needs for geophysics which are not satisfied by these missions. Two areas where improvements must be done are (i) perenniality of the observations, and (ii) determination of temporal variations of higher degrees of the gravity field. These improvements can be achieved thanks to new measurement technologies with higher precision, but also using new observables. Historically, space determination of the gravity field has been done observing the perturbations of the orbit of the satellites. More recently, GRACE has introduced the use of satellite-tosatellite ranging. Goce will use onboard gradiometry. The authors have explored the possibilities of two new technologies for the determination of the gravity field: (i) tethered systems, and (ii) formation flying for all kind of configurations (not just leader-follower). To analyze the possibilities of these technologies, we obtain the covariance matrix of the coefficients of the gravity field for the different observables. This can be done providing some very reasonable hypothesis are accepted. This matrix contains a lot of information concerning the behavior of the observable. In order to obtain the matrix, we use the so-called lumped coefficients approach. We have used this method for three observables (i) tethered systems, (ii) formation flying and (iii) gradiometry (for comparison purposes). Tethers appear as a very long base gradiometers, with very interesting properties, but also very challenging from a technological point of view. One of the major advantages of the tethered systems is their multitask design. Indeed, the same cable can be used for propulsion purposes in some phases of the mission, and for

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Active damping control for electrodynamic suspension systems without mechanical transducers

    SciTech Connect

    Brunelli, B.; Casadei, D.; Serra, G.; Tani, A.

    1996-09-01

    In this paper an electrodynamic suspension system for maglev vehicles is analyzed, in which the active damping of the vertical oscillations is obtained without position, velocity and acceleration transducers. The damping effect is accomplished controlling the supply voltage of the damping coil to respond to current changes due to vertical oscillations. The stability of the suspension system is investigated by a linearized analysis of the model equations, emphasizing the influence of the voltage regulator parameters. The performance of the damping system, in terms of step response and ride quality, is also discussed.

  10. 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

  11. 3-dimensional current collection model. [Of Tethered Satellite System 1

    SciTech Connect

    Hwang, Kai-Shen; Shiah, A.; Wu, S.T.; Stone, N. Alabama, University, Huntsvilll NASA, Marshall Space Flight Center, Huntsville, Ae )

    1992-07-01

    A three-dimensional, time dependent current collection model of a satellite has been developed for the TSS-1 system. The system has been simulated particularly for the Research of Plasma Electrodynamics (ROPE) experiment. The Maxwellian distributed particles with the geomagnetic field effects are applied in this numerical simulation. The preliminary results indicate that a ring current is observed surrounding the satellite in the equatorial plane. This ring current is found between the plasma sheath and the satellite surface and is oscillating with a time scale of approximately 1 microsec. This is equivalent to the electron plasma frequency. An hour glass shape of electron distribution was observed when the viewing direction is perpendicular to the equatorial plane. This result is consistent with previous findings from Linson (1969) and Antoniades et al. (1990). Electrons that are absorbed by the satellite are limited from the background ionosphere as indicated by Parker and Murphy (1967). 6 refs.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. The effects of tethering rear -facing child restraint systems on ATD responses.

    PubMed

    Manary, Miriam A; Reed, Matthew P; Klinich, Kathleen D; Ritchie, Nichole L; Schneider, Lawrence W

    2006-01-01

    A series of sled tests was performed to analyze the responses of an anthropomorphic test device (ATD), particularly neck forces, when rear-facing child restraint systems (CRS) are tethered. Nominally identical rear-facing CRS were tested in four tether conditions: untethered, tethered down to the floor, tethered down to the bottom of the vehicle seat, and tethered rearward to a point above the back of the vehicle seat. The CRABI 12MO ATD with head, upper neck, and chest instrumentation was used in all tests. The tests were conducted using the ECE R44.02 test bench. Both frontal and rear impacts were performed and each condition was repeated for a total of 16 sled tests. Motions of the CRS and ATD were recorded using high-speed digital video (1000 fps). The highest ATD accelerations, forces, and moments were observed during the primary impact of a frontal test, rather than on rebound. The loads observed during rebound from frontal impact were similar in magnitude to the peak loads collected during rear impact. The four tethering geometries produced distinct loading patterns. The lowest HIC, neck forces, and chest accelerations in both impact directions were observed with the rearward tether. The upper neck moment data did not show a clear trend relative to tethering geometry. ATD and CRS motions were best controlled in frontal impact by the rearward tethering geometry while the motions in rear impact were best controlled by tethering to the floor. The data show a potential benefit in both frontal and rear impacts of tethering rear-facing CRS to a point above the vehicle seatback. PMID:16968650

  20. 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.

  1. 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

  2. Current collection and current closure in the Tethered Satellite System

    NASA Technical Reports Server (NTRS)

    Drobot, Adam; Satyanarayana, P.; Chang, Chia-Lie; Tsang, Kang; Papadopoulos, Dennis

    1991-01-01

    Current collection and closure-path modeling are examined analytically with respect to the Tethered Satellite System (TSS). A particle-in cell code is compared with a one-dimensional unmagnetized fluid code to model the behavior of a positively charged satellite in the ionosphere. The morphology of the sheath and the sheath-region processes are thus examined, and the influence of ions leaving the sheath region is found to cause the attraction of an electron current that is 40 times greater than the steady state value. The enhancement is transient and enhances the acceleration of the electrons in the sheath. A set of modified MHD equations, including those for ion inertia, quasineutrality, and electron drift, is employed to model TSS current closure. Whistler modes are found to exist and can be excited as the TSS passes through the ionosphere. Important conclusions include a significant fluctuation level in the steady state sheath, an ion void which affects the electron population, and some long-lived electrons trapped in the settled sheath with respect to two directions.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. On dynamical formulations of a tethered satellite system with mass transport

    NASA Astrophysics Data System (ADS)

    Liu, F. C.

    1985-01-01

    Two satellites connected by a long flexible tether along the earth radial direction comprise a stable equilibrium state. This paper deals with formulations of in-plane motion of the tether connected satellites with a third mass transporting from one satellite to the other. Systems of equations of motion formulated by two methods, Lagrange equations and D'Alembert's Principle, are presented and methods for numerical solutions are proposed. Initial conditions for inward and outward transfers are derived.

  8. 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.

  9. The detection of gravitational waves using electrodynamic system of Earth

    NASA Astrophysics Data System (ADS)

    Grunskaya, Lubov; Isakevich, Valiriy

    There is studied the interconnection of tide processes of geophysical and astrophysical origin with the Earth electromagnetic fields. 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 were discovered frequencies in the electrical and geomagnetical field of ELF range with PAS, which coincide with the frequency of gravitational -wave radiation of a number of double stellar systems. In the electrical and geomagnetic field there was discovered a specific axion frequency VA=0.5*10-5 Hz belonging to the ELF range which was predicted by the theory. The problem of the anomalous behavior of the electrodynamic system response to the gravitational - wave affect is being discussed. On the basis of the rich experimental material have been investigated the frequencies of gravitational-wave radiation of a number of binary systems: J0700+6418, J1012+5307, J1537+1155, J1959+2048, J2130+1210, J1915+1606. The work is carried out with supporting of RFFI № 14-07-97510, State Task to Universities on 2014-2016.

  10. Several Developments in Space Tethers

    NASA Technical Reports Server (NTRS)

    Santangelo, Andrew; Sturmfels, Rich; Rothwell, Neal

    2007-01-01

    Five reports address different aspects of development of tethers to be deployed from spacecraft in orbit around the Earth. The first report discusses proposed optoelectronic tracking of retroreflective objects located at intervals or of retroreflective coats along the entire length of a tether to measure lateral motions. The second report describes digitally controlled spooling machinery that retracts or extends a tape tether at controlled speed and tension in the spool isolated from uncontrolled tension on the outside. The third report discusses part of this machinery that pivots to accommodate misalignments between the deployed and spooled portions of the tether and contains rollers used to exert tension and speed control. The fourth report discusses aspects of designs of proposed electrodynamic tethers, which would be electrically conductive and would interact with the magnetic field of the Earth to exert forces to modify orbits of deploying spacecraft. The fifth report discusses electrical aspects of designs of electrodynamic tape tethers, including the use of solar cells or motional electromagnetic force to generate currents in tethers and the use of electron emitters and electron and ion collectors at opposite ends of tethers to make electrical contact with the thin plasma in surrounding space.

  11. 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.

  12. Impact of tether cutting on onboard navigation during the Tethered Satellite Mission-1

    NASA Astrophysics Data System (ADS)

    Pirker, Dana M.

    1989-10-01

    The first Tethered Satellite System mission (TSS-1) is manifested for Shuttle Flight STS-44 in January of 1991. The TSS mission presents a new challenge to engineers, requiring advanced guidance, navigation and control concepts. Current NASA flight rules require that the navigational state of the Orbiter at deorbit burn be known to an accuracy of 20 nautical miles. Response of the Shuttle crew to this contingency may involve cutting the tether prior to a complete retrieval. The degradation of the navigational state accuracy as modelled by Shuttle navigation system is examined. Responses to the loss of communication scenario are proposed for two cases. The first case examines navigational performance during a nominal attitude profile. The second case is identical to the first, with the inclusion of modelled tether electrodynamical forces. Comparisons of trajectories propagated from the onboard navigational state vector and a reference ephemeris state vector were performed, with the tether cut simulated at various points during the mission. Additionally, updates to the onboard navigational state via ground uplinks were provided prior to the assumed loss of communication. Through these comparisons, the onboard navigation state error was determined. Alternative responses result from efforts to minimize this error during the various phases of TSS-1 deployment. These results demonstrated existing NASA flight rules could be violated by cutting the tether, and suggests reponses to a loss of communications contingency to maintain a more accurate navigational state.

  13. 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.

  14. 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.

  15. Qualification and In-Flight Demonstration of a European Tether Deployment and Momentum Transfer System on YES2

    NASA Astrophysics Data System (ADS)

    Kruijff, M.; van der Heide, E. J.

    2008-08-01

    This paper highlights the design, qualification and mission performance of a comprehensive tethered momentum transfer technology on ESA's second Young Engineers' Satellite (YES2), aiming specifically on the tether deployer. The deployer is designed with a broad range of near-term tether applications in mind and therefore opens up novel possibilities e.g. small satellite missions. The system contains the following critical elements. The tether, including features to enhance safety, wound up in controlled manner onto a spool core; optical deployment sensors and electronics; a "barberpole" friction brake controlled by a stepper motor; and a triple cutter system. A spring-based ejection system and, on the subsatellite side, a timer/release system facilitate the stagings required for accurate tethered momentum transfer. In addition a small, 6 kg re-entry capsule was developed with 1 kg scientific payload and parachute system. On September 25th, 2007, YES2 deployed a 32 km tether in orbit and gathered a wealth of data. This paper aims to provide an overview of the design, qualification and flight performance of the tether deployer hardware. This performance is compared to the design and from this can be concluded a suitability of the hardware for tether deployment and tethered momentum transfer.

  16. 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.

  17. 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.

  18. Tether fundamentals

    NASA Technical Reports Server (NTRS)

    Carroll, J. A.

    1986-01-01

    Some fundamental aspects of tethers are presented and briefly discussed. The effects of gravity gradients, dumbbell libration in circular orbits, tether control strategies and impact hazards for tethers are among those fundamentals. Also considered are aerodynamic drag, constraints in momentum transfer applications and constraints with permanently deployed tethers. The theoretical feasibility of these concepts are reviewed.

  19. 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.

  20. Downward-deployed tethered satellite systems, measurement techniques, and instrumentation - A review

    NASA Technical Reports Server (NTRS)

    Brown, Kenneth G.; Melfi, Leonard T., Jr.; Upchurch, Billy T.; Wood, George M., Jr.

    1992-01-01

    This paper describes a number of scheduled and proposed Shuttle-based downward-deployed tethered satellite systems (TSSs) the purpose of which is to determine the structure of the lower thermosphere and to measure the atmospheric and aerodynamic effects in the vicinity of the satellite, the aerothermodynamic effects on the satellite's surface, and the dynamics of the tether and its endmass, the satellite. The instruments for the downward-deployed tethered missions will include mass spectrometers and other density sensors, plasma instrumentation, optical spectrophotometers, magnetometers, and instrumentation to measure the effects on satellite surface (such as the surface temperature, heat transfer, and pressure; gas adsorption on surfaces, chemistry with other gas molecules and surface material, and desorption from the surface; and surface charging).

  1. 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).

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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

  7. 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.

  8. Applications of a dynamic tethering system to enable the deep space cam jointed observation bot

    NASA Astrophysics Data System (ADS)

    Leake, Skye; McGuire, Thomas; Parsons, Michael; Hirsch, Michael P.; Straub, Jeremy

    2016-05-01

    A device capable of creating tethers for use with spacecraft that are made from a diverse material palette could serve many functions. These functions include supporting applications such as data transfer, power generation, and resource collection. Applications that are currently being considered include use in a system for orientation, data transfer, and power delivery and use as part of a free-moving camera system which would be used in proximity to a spacecraft for capturing images and video for promotional and preforming diagnostic and "self-check" operations. Materials that have been considered for use in such a tethering device have different physical attributes in order to facilitate supporting the widest possible degree of applications for use in scientific, remote sensing, power generation, and electromagnetic applications methods for the parent spacecraft. Physical properties that have been considered include: rigidity, conductivity, heat dissipation, and opacity. The proposed dynamic tethering system would be driven by 3D printing technologies. This prospective application of 3D printing remains relatively unexplored. This provides great opportunities for knowledge expansion and the development of dynamic tethers for use capturing video footage and pictures, and for other scientific endeavors.

  9. Shuttle Orbiter tethered subsatellite for exploring and tapping space plasmas

    NASA Technical Reports Server (NTRS)

    Banks, P. M.; Williamson, P. R.; Oyama, K. I.

    1981-01-01

    Consideration is given to the possibilities for studies in space plasma physics offered by a subsatellite mechanically tethered above the Space Shuttle Orbiter by a long conducting wire. The proposed experiment, designated the Shuttle Electrodynamic Tether Systems (SETS) is based on the concept of collecting electrons at the subsatellite and ejecting them from the Orbiter, made possible by the emf generated by the motion of the tether across geomagnetic field lines. The power generated in this manner can be used both for practical purposes within the Orbiter and for the creation of large-amplitude plasma and electromagnetic waves within the surrounding plasma. For a conducting spherical subsatellite 30 m in diameter with a 10-km tether drawing 1 A, calculations show that emfs on the order of 1000-2000 V and energy dissipation of as much as 10,000 W can be obtained, accompanied by the generation of two regions of net electric charge in the ionosphere. Scientific studies considered for SETS include the measurement of MHD waves artificially generated in the ionosphere, the investigation of current-driven plasma instabilities, VLF wave generation and the simulation of electrodynamics associated with the motion of celestial bodies through plasma.

  10. 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.

  11. 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

  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. 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.

  14. Analysis of electrode system for generation of high-power electrodynamic flow

    NASA Astrophysics Data System (ADS)

    Rebrov, I. E.; Khomich, V. Yu.; Yamshchikov, V. A.

    2016-08-01

    A high-power electrodynamic flow in atmospheric air is numerically simulated and experimentally studied. An electrode system consisting of a cylindrical plasma emitter and a plane metal grid collector of ions is used to generate a flow with a speed of 2 m/s and a volume rate of 15 L/s.

  15. 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.

  16. 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

  17. Electrodynamic pulsator

    SciTech Connect

    Myslinski, A.; Semeniuk, B.; Kasprzycka-Guttman, T. . Dept. of Chemistry)

    1993-11-01

    An electrodynamic pulsator, designed for the reciprocation of liquids in an pulsed extractor, is described. Application of the pulsator is illustrated by its performance in connection with a laboratory packed column used for extraction of citric acid from aqueous solutions by cyclohexanone. A schematic of the pulsator is shown. This pulsator was designed to avoid the indirect, stepwise, mechanical regulation systems used in pulsed extractors which employ an external device such as a piston pump.

  18. 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.

  19. Experimental verification of chaotic control of an underactuated tethered satellite system

    NASA Astrophysics Data System (ADS)

    Pang, Zhaojun; Jin, Dongping

    2016-03-01

    This paper studies chaotic control of a tethered satellite system (TSS) driven only by a momentum-exchange device during its attitude adjustment. In dealing with such the underactuated system, an extended time-delay autosynchronization (ETDAS) is employed to stabilize the chaotic motion to a periodic motion. To obtain the control domains of the ETDAS method, a stability analysis of the controlled tethered satellite system in elliptical orbit is implemented. According to the principle of dynamic similarity, then, ground-based experiment setups are proposed and designed to emulate the in-plane motions of the TSS. Representative experiments are presented to demonstrate the effectiveness of the ETDAS scheme in controlling the chaotic motion of the underactuated TSS.

  20. 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.

  1. 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

  2. Tethered gravity laboratories study

    NASA Technical Reports Server (NTRS)

    Lucchetti, F.

    1989-01-01

    Information on the Tethered Gravity Laboratory on the International Space Station is given in viewgraph form. Topics covered include active control, low gravity processes identification, systems analysis, tether interfaces with the Laboratory, elevator and payload configurations, elevator subsystems, and accelerometer technology requirements.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. All-out Test in Tethered Canoe System can Determine Anaerobic Parameters of Elite Kayakers.

    PubMed

    Messias, L H D; Ferrari, H G; Sousa, F A B; Dos Reis, I G M; Serra, C C S; Gobatto, C A; Manchado-Gobatto, F B

    2015-10-01

    The aims of this study were to use a specific all-out 30-sec tethered test to determine the anaerobic parameters in elite kayakers and verify the relationship between these results and sports performance. Twelve elite slalom kayakers were evaluated. The tethered canoe system was created and used for the all-out 30-sec test application. Measurements of peak force, mean force, minimum force, fatigue index and impulse were performed. Performance evaluation was determined by measuring the time of race in a simulated race containing 24 gates on a white-water course. Blood was collected (25-µl) for analysis of lactate concentration at rest and at 2, 4, 6, 8 and 10-min intervals after both the all-out test and the simulated race. The Pearson product moment correlation shows a inverse and significant relationship of peak force, mean force and impulse with time of race. Blood lactate concentrations after the all-out test and the simulated race peak at same time (4 min). Additionally, no interaction was visualized between time and all-out test/simulated race for blood lactate concentrations (P <0.365). These results suggest a relationship between the parameters of the all-out test and performance. Thus, the tethered canoe system is a useful tool for determining parameters that could be used in training control of slalom kayakers.

  8. 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.

  9. 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.

  10. 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

  11. 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

  12. 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

  13. 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.

  14. Space weather disturbances in the ionosphere-thermosphere-electrodynamics system at middle and low latitudes

    NASA Astrophysics Data System (ADS)

    Schunk, Robert

    2012-07-01

    It has been clearly established that the ionosphere-thermosphere-electrodynamics system can vary significantly from hour to hour and from day to day. The hour-to-hour variations are associated with weather disturbances, which can produce mesoscale (100-1000 km) structures and plasma irregularities. For the ionosphere, these weather disturbances include Traveling Ionospheric Disturbances (TIDs), sporadic E layers, He ^{+} layers in the topside ionosphere, descending intermediate layers, ridges of enhanced ionization (Storm Enhanced Densities), a 4-wave signature, spread-F, and equatorial plasma bubbles. For the thermosphere, the weather disturbances include upward propagating waves from the lower atmosphere (planetary, tidal and gravity waves), Traveling Atmospheric Disturbances (TADs) generated at high latitudes, storm-time O/N _{2} depletions, and neutral gas perturbations both at the terminator and in the regions containing equatorial plasma bubbles. The current state of our knowledge of weather disturbances in the middle and low latitude ionosphere-thermosphere-electrodynamics system will be reviewed.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. Effects of aerodynamic lift on the stability of tethered subsatellite system

    NASA Astrophysics Data System (ADS)

    Keshmiri, Mehdi; Misra, Arun K.

    Dynamics and stability of a two-body tethered system are investigated considering the aerodynamic lift on the subsatellite in addition to he aerodynamic drag. The Free Molecular Flow Model is used to calculate the aerodynamic forces on the subsatellite. Equilibrium configurations of the system are obtained numerically. Equations of motion are linearized analytically about the equilibrium configuration through a symbolic manipulation language, Maple V., and stability behavior of small oscillations about the equilibrium configuration is analyzed. An extensive parametric study is done to understand the effect of aerodynamic forces (lift and drag) on the stability of the uncontrolled system. It is shown that the stability behavior changes significantly if the subsatellite is changed from a body with no lift to a body with lift. Hence, an unstable system with a spherical subsatellite can be stabilized if aerodynamic surfaces are appropriately added. It is concluded that consideration of the aerodynamic lifting forces in addition to the aerodynamic drag forces on the subsatellite is indispensible for proper design of a tethered subsatellite system deployed in a low-altitude orbit.

  6. 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.

  7. Advantages of using an elliptically-orbiting tethered-dumbbell system for a satellite transfer to geosynchronous orbit

    NASA Astrophysics Data System (ADS)

    Kyroudis, G. A.; Conway, B. A.

    1986-08-01

    This paper examines the use of an elliptically-orbiting tethered-dumbbell (Space Shuttle-satellite) system for satellite transfer to geosynchronous altitude. The two-dimensional rigid body equations of motion are derived using a Lagrangian method. Integration of these equations yields the system states, from tether deployment through payload release. These states are used to predict the Delta V savings (compared to a Hohmann transfer) when the payload is given a 'forward swing zero libration' release, that is, the payload is released on a forward swing when the libration angle is instantaneously zero. By varying the predeployment true anomaly, the 'forward swing zero libration' is caused to occur nearly simultaneously with periapse passage, resulting in maximum Delta V savings. The system deployment velocity and tether length were also varied to observe their effect on Delta V savings.

  8. 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.

  9. 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.

  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. 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.

  12. 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.

  13. 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.

  14. 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

  15. Single-photon filtering by a cavity quantum electrodynamics system

    SciTech Connect

    Koshino, Kazuki

    2008-02-15

    The nonlinear dynamics of a classical photon pulse in a cavity-QED system is investigated theoretically. It is shown that this system can work as a single-photon filter, which drastically suppresses the multiple-photon probability of the output. The output photon statistics is sensitive to the input pulse length. A suitable choice of pulse length produces a photon pulse with the single-photon probability of 0.32, while the multiple-photon probability is suppressed to 0.01.

  16. Dynamic circuit and Fourier series methods for moment calculation in electrodynamic repulsive magnetic levitation systems

    NASA Astrophysics Data System (ADS)

    Knowles, R.

    1982-07-01

    A general theory of moments for electrodynamic magnetic levitation systems has been developed using double Fourier series and dynamic circuit principles. Both employ Parseval's theorem using either wave constant derivatives or the polar waveconstant principle of the Fourier-Bessel/double Fourier series equivalence. A method for calculating angular derivatives of moments and forces is explained, and for all of these methods comparisons are made with experimental results obtained for single and split rail configurations. Extensions of dynamic circuit theory for tilted nonflat and circular magnets are also explained.

  17. Interference control of nonlinear excitation in a multi-atom cavity quantum electrodynamics system.

    PubMed

    Yang, Guoqing; Tan, Zheng; Zou, Bichen; Zhu, Yifu

    2014-12-01

    We show that by manipulating quantum interference in a multi-atom cavity quantum electrodynamics (CQED) system, the nonlinear excitation of the cavity-atom polariton can be resonantly enhanced while the linear excitation is suppressed. Under the appropriate conditions, it is possible to selectively enhance or suppress the polariton excitation with two free-pace laser fields. We report on an experiment with cold Rb atoms in an optical cavity and present experimental results that demonstrate such interference control of the CQED excitation and its direct application to studies of all-optical switching and cross-phase modulation of the cavity-transmitted light.

  18. Electrodynamics of a compound system with relativistic corrections

    SciTech Connect

    Pachucki, Krzysztof

    2007-08-15

    The electromagnetic interaction of a moving compound charged system with leading relativistic corrections is studied. An effective Hamiltonian is obtained by using a set of canonical transformations, and it is demonstrated that the coupling of the total motion to internal degrees of freedom is uniquely determined by Lorentz covariance. Several known results such as the Roentgen term and the interaction of the spin with the electric field are recovered, and new results for various relativistic and recoil corrections are obtained.

  19. 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.

  20. Adaptive sliding mode controller based on super-twist observer for tethered satellite system

    NASA Astrophysics Data System (ADS)

    Keshtkar, Sajjad; Poznyak, Alexander

    2016-09-01

    In this work, the sliding mode control based on the super-twist observer is presented. The parameters of the controller as well as the observer are admitted to be time-varying and depending on available current measurements. In view of that, the considered controller is referred to as an adaptive one. It is shown that the deviations of the generated state estimates from real state values together with a distance of the closed-loop system trajectories to a desired sliding surface reach a μ-zone around the origin in finite time. The application of the suggested controller is illustrated for the orientation of a tethered satellite system in a required position.

  1. Classical electrodynamic systems interacting with classical electromagnetic random radiation

    NASA Astrophysics Data System (ADS)

    Cole, Daniel C.

    1990-02-01

    In the past, a few researchers have presented arguments indicating that a statistical equilibrium state of classical charged particles necessarily demands the existence of a temperature-independent, incident classical electromagnetic random radiation. Indeed, when classical electromagnetic zero-point radiation is included in the analysis of problems with macroscopic boundaries, or in the analysis of charged particles in linear force fields, then good agreement with nature is obtained. In general, however, this agreement has not been found to hold for charged particles bound in nonlinear force fields. The point is raised here that this disagreement arising for nonlinear force fields may be a premature conclusion on this classical theory for describing atomic systems, because past calculations have not directed strict attention to electromagnetic interactions between charges. This point is illustrated here by examining the classical hydrogen atom and showing that this problem has still not been adequately solved.

  2. 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.

  3. Dynamics of variable-length tethers with application to tethered satellite deployment

    NASA Astrophysics Data System (ADS)

    Tang, J. L.; Ren, G. X.; Zhu, W. D.; Ren, H.

    2011-08-01

    The dynamics of variable-length tethers are studied using a flexible multibody dynamics method. The governing equations of the tethers are derived using a new, hybrid Eulerian and Lagrangian framework, by which the mass flow at a boundary of a tether and the length variation of a tether element are accounted for. The variable-length tether element based on the absolute nodal coordinate formulation is developed to simulate the deployment of satellite tethers. The coupled dynamic equations of tethers and satellites are obtained using the Lagrangian multiplier method. Several tethered satellite systems involving large displacements, rotations, and deformations are numerically simulated, where the tethers are released from several meters to about 1 km. A control strategy is proposed to avoid slackness of the tethers during deployment. The accuracy of the modeling and solution procedures was validated on an elevator model.

  4. 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.

  5. 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.

  6. 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.

  7. SPARCL: a high-altitude tethered balloon-based optical space-to-ground communication system

    NASA Astrophysics Data System (ADS)

    Badesha, Surjit S.

    2002-12-01

    The Johns Hopkins University Applied Physics Laboratory (JHU/APL) has conducted a feasibility study to determine if a high altitude (20 km) tethered balloon-based space-to-ground optical communication system is a feasible concept. To support this effort, a detailed concept definition was developed and associated issues were identified and analyzed systematically. Of all the adverse atmospheric phenomena, cloud coverage was identified as the most prohibitive obstacle for a space-to-ground optical communication link. However, by placing a receiver on a balloon at a 20 km altitude, the proposed high altitude system avoids virtually all atmospheric effects. A practical notional scenario was developed (i.e. surveillance and/or reconnaissance of a regional conflict) involving end-to-end optical communication architecture to identify system elements, system level requirements, and to quantify realistic data rate requirements. Analysis of the proposed space-to-ground communication elements indicates that while significant development is required, the system is technically feasible and is a very cost effective 24/7solution.

  8. 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.

  9. Space Tethers: Design Criteria

    NASA Technical Reports Server (NTRS)

    Tomlin, D. D.; Faile, G. C.; Hayashida, K. B.; Frost, C. L.; Wagner, C. Y.; Mitchell, M. L.; Vaughn, J. A.; Galuska, M. J.

    1997-01-01

    This document is prepared to provide a systematic process for the selection of tethers for space applications. Criteria arc provided for determining the strength requirement for tether missions and for mission success from tether severing due to micrometeoroids and orbital debris particle impacts. Background information of materials for use in space tethers is provided, including electricity-conducting tethers. Dynamic considerations for tether selection is also provided. Safety, quality, and reliability considerations are provided for a tether project.

  10. 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.

  11. Self-formed cavity quantum electrodynamics in coupled dipole cylindrical-waveguide systems.

    PubMed

    Afshar V, S; Henderson, M R; Greentree, A D; Gibson, B C; Monro, T M

    2014-05-01

    An ideal optical cavity operates by confining light in all three dimensions. We show that a cylindrical waveguide can provide the longitudinal confinement required to form a two dimensional cavity, described here as a self-formed cavity, by locating a dipole, directed along the waveguide, on the interface of the waveguide. The cavity resonance modes lead to peaks in the radiation of the dipole-waveguide system that have no contribution due to the skew rays that exist in longitudinally invariant waveguides and reduce their Q-factor. Using a theoretical model, we evaluate the Q-factor and modal volume of the cavity formed by a dipole-cylindrical-waveguide system and show that such a cavity allows access to both the strong and weak coupling regimes of cavity quantum electrodynamics.

  12. 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.

  13. 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.

  14. Multiparty Quantum Secret Sharing of Classical Message using Cavity Quantum Electrodynamic System

    NASA Astrophysics Data System (ADS)

    Han, Lian-Fang; Liu, Yi-Min; Zhang, Zhan-Jun

    2006-08-01

    An experimental feasible scheme of multiparty secret sharing of classical messages is proposed, based on a cavity quantum electrodynamic system. The secret messages are imposed on atomic Bell states initially in the sender's possession by local unitary operations. By swapping quantum entanglement of atomic Bell states, the secret messages are split into several parts and each part is distributed to a separate party. In this case, any subset of the entire party group can not read out the secret message but the entirety via mutual cooperations. In this scheme, to discriminate atomic Bell states, additional classical fields are employed besides the same highly-detuned single-mode cavities used to prepare atomic Bell states. This scheme is insensitive to the cavity decay and the thermal field, and usual joint Bell-state measurements are unnecessary.

  15. 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.

  16. 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.

  17. 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

  18. 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 ...

  19. 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.

  20. 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.

  1. Characterization of the Thermotoga maritima Chemotaxis Methylation System that Lacks Methyltransferase CheR:MCP Tethering

    PubMed Central

    Perez, Eduardo; Stock, Ann M.

    2013-01-01

    Summary Sensory adaptation in bacterial chemotaxis is mediated by covalent modifications of specific glutamate and glutamine residues within the cytoplasmic domains of methyl-accepting proteins (MCPs). In Escherichia coli and Salmonella enterica, efficient methylation of MCPs depends on the localization of methyltransferase CheR to MCP clusters through an interaction between the CheR β-subdomain and a pentapeptide sequence (NWETF or NWESF) at the C terminus of the MCP. In vitro methylation analyses utilizing S. enterica and Thermotoga maritima CheR proteins and MCPs indicate that MCP methylation in T. maritima occurs independently of a pentapeptide-binding motif. Kinetic and binding measurements demonstrate that despite efficient methylation, the interaction between T. maritima CheR and T. maritima MCPs is of relatively low affinity. Comparative protein sequence analyses of CheR β-subdomains from organisms having MCPs that contain and/or lack pentapeptide-binding motifs identified key similarities and differences in residue conservation, suggesting the existence of two distinct classes of CheR proteins: pentapeptide-dependent and pentapeptide-independent methyltransferases. Analysis of MCP C-terminal ends showed that only ~10% of MCPs contain a putative C-terminal binding motif, the majority of which are restricted to the different proteobacteria classes (α, β, γ, δ). These findings suggest that tethering of CheR to MCPs is a relatively recent event in evolution and that the pentapeptide-independent methylation system is more common than the well characterized pentapeptide-dependent methylation system. PMID:17163981

  2. 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.

  3. 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.

  4. Modeling the Ionosphere-Thermosphere-Electrodynamics System for Space Weather Specifications, Forecasts and Applications

    NASA Astrophysics Data System (ADS)

    Schunk, R. W.; Scherliess, L.; Eccles, V.; Gardner, L. C.; Sojka, J. J.; Zhu, L.; Pi, X.; Mannucci, A. J.; Butala, M. D.; Wilson, B. D.; Komjathy, A.; Wang, C.; Rosen, G.

    2015-12-01

    Significant progress has been made during the last two decades with regard to understanding, specifying, forecasting, and mitigating the impacts of space weather on numerous DoD and civilian activities. The progress has been made because of more and improved measurements, and advances in modeling the ionosphere-thermosphere-electrodynamics (I-T-E) system. With regard to modeling, the recent focus has been on ensemble modeling with both physics-based and data assimilation models. Our team has created a Multimodel Ensemble Prediction System (MEPS) that is composed of seven physics-based data assimilation models for the I-T-E system that cover the globe. Five different data assimilation models cover the mid-low latitude region, so that we can conduct ensemble modeling with physics-based data assimilation models in that domain. The data assimilation models can assimilate Total Electron Content (TEC) from a constellation of satellites, bottom-side electron density profiles from digisondes, and in situ plasma densities, occultations and ultraviolet emissions from satellites. We have performed MEPS model runs for selected storm and quiet periods, and for each period we have obtained ensemble model reconstructions with different data types and amounts in order to determine how the individual data assimilation models behave. These new and interesting results will be presented.

  5. 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.

  6. 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.

  7. Quantum electrodynamical theory of high-efficiency excitation energy transfer in laser-driven nanostructure systems

    NASA Astrophysics Data System (ADS)

    Weeraddana, Dilusha; Premaratne, Malin; Gunapala, Sarath D.; Andrews, David L.

    2016-08-01

    A fundamental theory is developed for describing laser-driven resonance energy transfer (RET) in dimensionally constrained nanostructures within the framework of quantum electrodynamics. The process of RET communicates electronic excitation between suitably disposed emitter and detector particles in close proximity, activated by the initial excitation of the emitter. Here, we demonstrate that the transfer rate can be significantly increased by propagation of an auxiliary laser beam through a pair of nanostructure particles. This is due to the higher order perturbative contribution to the Förster-type RET, in which laser field is applied to stimulate the energy transfer process. We construct a detailed picture of how excitation energy transfer is affected by an off-resonant radiation field, which includes the derivation of second and fourth order quantum amplitudes. The analysis delivers detailed results for the dependence of the transfer rates on orientational, distance, and laser intensity factor, providing a comprehensive fundamental understanding of laser-driven RET in nanostructures. The results of the derivations demonstrate that the geometry of the system exercises considerable control over the laser-assisted RET mechanism. Thus, under favorable conformational conditions and relative spacing of donor-acceptor nanostructures, the effect of the auxiliary laser beam is shown to produce up to 70% enhancement in the energy migration rate. This degree of control allows optical switching applications to be identified.

  8. On a modified electrodynamics.

    PubMed

    Reiss, H R

    2012-09-01

    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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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.

  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. 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.

  18. 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.

  19. 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.

  20. Electrodynamics of Perfect Conductors

    NASA Astrophysics Data System (ADS)

    Fiolhais, Miguel C. N.; Essén, Hanno

    2013-05-01

    The most general electrodynamic equations of a perfect conducting state are obtained using a variational principle in a classical framework, following an approach by Pierre-Gilles de Gennes. London equations are derived as the time-independent case of these equations, corresponding to the magnetostatic minimal energy state of the perfect conducting system. For further confirmation, the same equations are also derived in the classical limit of the Coleman-Weinberg model, the most successful quantum macroscopic theory of superconductivity. The magnetic field expulsion is, therefore, a direct consequence of zero resistivity and not an exclusive property of superconductors.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. Electrodynamics sensor for the image reconstruction process in an electrical charge tomography system.

    PubMed

    Rahmat, Mohd Fua'ad; Isa, Mohd Daud; Rahim, Ruzairi Abdul; Hussin, Tengku Ahmad Raja

    2009-01-01

    Electrical charge tomography (EChT) is a non-invasive imaging technique that is aimed to reconstruct the image of materials being conveyed based on data measured by an electrodynamics sensor installed around the pipe. Image reconstruction in electrical charge tomography is vital and has not been widely studied before. Three methods have been introduced before, namely the linear back projection method, the filtered back projection method and the least square method. These methods normally face ill-posed problems and their solutions are unstable and inaccurate. In order to ensure the stability and accuracy, a special solution should be applied to obtain a meaningful image reconstruction result. In this paper, a new image reconstruction method - Least squares with regularization (LSR) will be introduced to reconstruct the image of material in a gravity mode conveyor pipeline for electrical charge tomography. Numerical analysis results based on simulation data indicated that this algorithm efficiently overcomes the numerical instability. The results show that the accuracy of the reconstruction images obtained using the proposed algorithm was enhanced and similar to the image captured by a CCD Camera. As a result, an efficient method for electrical charge tomography image reconstruction has been introduced.

  6. 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.

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  11. Morpheus Tether Test #15

    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 ...

  12. 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...

  13. Morpheus Tether Test #17

    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...

  14. Morpheus Tether Test #16

    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...

  15. 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 ...

  16. Morpheus Tether Test #20

    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...

  17. 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...

  18. Cellular adhesion and dynamic membrane tether extraction

    NASA Astrophysics Data System (ADS)

    Nowak, Sarah; Chou, Tom

    2009-03-01

    We consider the energetics and dynamics of pulling a ligand bound to an integral membrane receptor. Deformation of the cell membrane and cytoskeleton is considered as the ligand is pulled. We assume that deformation of the cytoskeleton obeys Hook's law up to a critical force at which the cell membrane locally detaches from the cytoskeleton and a membrane tether forms. Depending on the pulling velocity and force, a membrane tether of varying length may form before the receptor-ligand bond breaks. We study the probability of tether formation and the mean tether length at the moment of ligand detachment as a function of system parameters. This problem is applicable to AFM studies of cellular adhesion molecules, and to the biological problem of leukocyte rolling.

  19. Modeling Ionospheric Electrodynamics (Invited)

    NASA Astrophysics Data System (ADS)

    Huba, J. D.

    2009-12-01

    We present modeling results of ionospheric electrodynamics using the 3D NRL ionosphere model SAMI3. Recently, SAMI3 has been upgraded to solve the potential equation that determines the electrostatic potential from the ionospheric conductances (Pedersen and Hall) and drivers: neutral wind, gravity, and parallel current systems. We present results showing the impact of different neutral wind models (e.g., HWM93, HWM07, TIMEGCM) on the dynamics of the low- to mid-latitude ionosphere, as well as the Region 1 and 2 current systems. We point out issues and concerns with obtaining an accurate specification of the global electric field within the context of existing models.(with J. Krall, G. Joyce, S. Slinker, and G. Crowley). Research supported by NASA and ONR

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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.

  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. 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.

  7. 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.

  8. 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.

  9. 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.

  10. GRASP: A Multitasking Tether.

    PubMed

    Rabouille, Catherine; Linstedt, Adam D

    2016-01-01

    Originally identified as Golgi stacking factors in vitro, the Golgi reassembly stacking protein (GRASP) family has been shown to act as membrane tethers with multiple cellular roles. As an update to previous comprehensive reviews of the GRASP family (Giuliani et al., 2011; Vinke et al., 2011; Jarvela and Linstedt, 2012), we outline here the latest findings concerning their diverse roles. New insights into the mechanics of GRASP-mediated tethering come from recent crystal structures. The models of how GRASP65 and GRASP55 tether membranes relate directly to their role in Golgi ribbon formation in mammalian cells and the unlinking of the ribbon at the onset of mitosis. However, it is also clear that GRASPs act outside the Golgi with roles at the ER and ER exit sites (ERES). Furthermore, the proteins of this family display other roles upon cellular stress, especially in mediating unconventional secretion of both transmembrane proteins (Golgi bypass) and cytoplasmic proteins (through secretory autophagosomes).

  11. GRASP: A Multitasking Tether.

    PubMed

    Rabouille, Catherine; Linstedt, Adam D

    2016-01-01

    Originally identified as Golgi stacking factors in vitro, the Golgi reassembly stacking protein (GRASP) family has been shown to act as membrane tethers with multiple cellular roles. As an update to previous comprehensive reviews of the GRASP family (Giuliani et al., 2011; Vinke et al., 2011; Jarvela and Linstedt, 2012), we outline here the latest findings concerning their diverse roles. New insights into the mechanics of GRASP-mediated tethering come from recent crystal structures. The models of how GRASP65 and GRASP55 tether membranes relate directly to their role in Golgi ribbon formation in mammalian cells and the unlinking of the ribbon at the onset of mitosis. However, it is also clear that GRASPs act outside the Golgi with roles at the ER and ER exit sites (ERES). Furthermore, the proteins of this family display other roles upon cellular stress, especially in mediating unconventional secretion of both transmembrane proteins (Golgi bypass) and cytoplasmic proteins (through secretory autophagosomes). PMID:26858948

  12. GRASP: A Multitasking Tether

    PubMed Central

    Rabouille, Catherine; Linstedt, Adam D.

    2016-01-01

    Originally identified as Golgi stacking factors in vitro, the Golgi reassembly stacking protein (GRASP) family has been shown to act as membrane tethers with multiple cellular roles. As an update to previous comprehensive reviews of the GRASP family (Giuliani et al., 2011; Vinke et al., 2011; Jarvela and Linstedt, 2012), we outline here the latest findings concerning their diverse roles. New insights into the mechanics of GRASP-mediated tethering come from recent crystal structures. The models of how GRASP65 and GRASP55 tether membranes relate directly to their role in Golgi ribbon formation in mammalian cells and the unlinking of the ribbon at the onset of mitosis. However, it is also clear that GRASPs act outside the Golgi with roles at the ER and ER exit sites (ERES). Furthermore, the proteins of this family display other roles upon cellular stress, especially in mediating unconventional secretion of both transmembrane proteins (Golgi bypass) and cytoplasmic proteins (through secretory autophagosomes). PMID:26858948

  13. Benefits of tether momentum transfer to Space Station operations

    NASA Technical Reports Server (NTRS)

    Woodis, W. R.; Vanpelt, J. M.

    1986-01-01

    A full solar cycle (1994-2004) is analyzed to study tether and nontether Space Station operations. The Space Station yearly altitude variation for the two approaches are investigated; it is observed that the optimum tether approach provides greater benefits that the nontether approach due to the cargon weight gain associated with the preferred low altitudes of the optimum variable altitude tether approach. The advantages provided by the combining a variable altitude/OTV launch approach are discussed. The baseline and tethered Shuttle deployments are compared and the design and capabilities of the deployer system are examined.

  14. 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.

  15. 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.

  16. 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

  17. Electrodynamic forces of the cross-connected figure-eight null-flux coil suspension system

    SciTech Connect

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

    1993-01-01

    This paper analyzes the cross-connected figure-eight null-flux coil suspension system for maglev vehicles on the basis of dynamic circuit theory. The equivalent circuits and general magnetic force expressions for the system are developed. Simple analytical formulas for the magnetic force partitions on the basis of harmonic approximation are presented, and numerical results are also included.

  18. Tension waves in tethered satellite cables

    NASA Technical Reports Server (NTRS)

    Lallman, F. J.

    1984-01-01

    A one-degree-of-freedom simulation of the Tethered Satellite System (TSS) was programmed using a distributed system model of the tether based on the one-dimensional wave equation. This model represents the time varying tension profile along the tether as the sum of two traveling waves of tension moving in opposite directions. A control loop was devised which combines a deployment rate command with the measured tension at the deployer to produce a smooth, stable rate of deployment of the subsatellite. Simulation results show a buildup of periodic bursts of high frequency oscillation in tension. This report covers the mathematical modelling and simulation results and explains the reason for the observed oscillations. The design of a possible vibration damping device is discussed.

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. 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°.

  4. Input shaped large thrust maneuver with a tethered debris object

    NASA Astrophysics Data System (ADS)

    Jasper, Lee; Schaub, Hanspeter

    2014-03-01

    In order to reduce the debris population in LEO, remediation is necessary. An active debris removal method is explored that utilizes fuel reserves on a recently launched upper stage to rendezvous with, and tether to, debris. The system's tethered dynamics are explored using a discretized tether model attached to six degree of freedom end bodies. The thrust output is shaped to remove the spectral energy at the natural frequencies of the tether, significantly reducing the post-burn relative motion between the vehicles. The sensitivity of the input shaping performance due to imperfect knowledge of the debris mass demonstrates that a double notch spanning multiple frequencies around the first mode is necessary to be robust to unknown debris mass. On-orbit simulations show that input shaping helps the tethered system achieve smooth oscillations about a gravity gradient alignment, reducing collision likelihood.

  5. Input Shaped Large Thrust Maneuver with a Tethered Debris Object

    NASA Astrophysics Data System (ADS)

    Jasper, L.; Schaub, H.

    2013-08-01

    In order to reduce the debris population in LEO, remediation is necessary. An active debris removal method is explored that utilizes fuel reserves on a recently launched upper stage to rendezvous with, and tether to, debris. The system's tethered dynamics are explored using a discretized tether model attached to six degree of freedom end bodies. The thrust output is shaped to remove the spectral energy at the natural frequencies of the tether, significantly reducing the post-burn relative motion between the vehicles. The sensitivity of the input shaping performance due to imperfect knowledge of the debris mass demonstrates that a double notch spanning multiple frequencies around the first mode is necessary to be robust to unknown debris mass. On-orbit simulations show that input shaping helps the tethered system achieve smooth oscillations about a gravity gradient alignment, reducing collision likelihood.

  6. 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).

  7. 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.

  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. Spatial orbital tether constructions

    NASA Astrophysics Data System (ADS)

    Kogan, A. Yu.

    2016-09-01

    This paper is concerned with the problem of shape-retaining spatial tether configurations in a circular Keplerian orbit. Sufficient conditions of shape retention are described, which are imposed on the geometry of the structure, distribution of mass in the nodes, and parameters of rotation. The paper also mentions classes of structures with different properties of symmetry and motion, as well as specific examples of shaperetaining structures.

  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. 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.

  12. 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.

  13. Are all multisubunit tethering complexes bona fide tethers?

    PubMed

    Brunet, Stephanie; Sacher, Michael

    2014-11-01

    Since the late 1990s, a number of multisubunit tethering complexes (MTCs) have been described that function in membrane trafficking events: TRAPP I, TRAPP II, TRAPP III, COG, HOPS, CORVET, Dsl1, GARP and exocyst. On the basis of structural and sequence similarities, they have been categorized as complexes associated with tethering containing helical rods (CATCHR) (Dsl1, COG, GARP and exocyst) or non-CATCHR (TRAPP I, II and III, HOPS and CORVET) complexes (Yu IM, Hughson FM. Tethering factors as organizers of intracellular vesicular traffic. Annu Rev Cell Dev Biol 2010;26:137-156). Both acronyms (CATCHR and MTC) imply these complexes tether opposing membranes to facilitate fusion. The main question we will address is: have these complexes been formally demonstrated to function as tethers? If the answer is no, then is it premature or even correct to refer to them as tethers? In this commentary, we will argue that the vast majority of MTCs have not been demonstrated to act as a tether. We propose that a distinction between the terms tether and tethering factor be considered to address this issue. PMID:25048641

  14. 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.

  15. 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

  16. 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…

  17. Quantum Electrodynamics: Theory

    ScienceCinema

    Lincoln, Don

    2016-07-12

    The Standard Model of particle physics is composed of several theories that are added together. The most precise component theory is the theory of quantum electrodynamics or QED. In this video, Fermilab’s Dr. Don Lincoln explains how theoretical QED calculations can be done. This video links to other videos, giving the viewer a deep understanding of the process.

  18. Enhanced Tethered-Particle Motion Analysis Reveals Viscous Effects

    PubMed Central

    Kumar, Sandip; Manzo, Carlo; Zurla, Chiara; Ucuncuoglu, Suleyman; Finzi, Laura; Dunlap, David

    2014-01-01

    Tethered-particle motion experiments do not require expensive or technically complex hardware, and increasing numbers of researchers are adopting this methodology to investigate the topological effects of agents that act on the tethering polymer or the characteristics of the polymer itself. These investigations depend on accurate measurement and interpretation of changes in the effective length of the tethering polymer (often DNA). However, the bead size, tether length, and buffer affect the confined diffusion of the bead in this experimental system. To evaluate the effects of these factors, improved measurements to calibrate the two-dimensional range of motion (excursion) versus DNA length were carried out. Microspheres of 160 or 240 nm in radius were tethered by DNA molecules ranging from 225 to 3477 basepairs in length in aqueous buffers containing 100 mM potassium glutamate and 8 mM MgCl2 or 10 mM Tris-HCl and 200 mM KCl, with or without 0.5% Tween added to the buffer, and the motion was recorded. Different buffers altered the excursion of beads on identical DNA tethers. Buffer with only 10 mM NaCl and >5 mM magnesium greatly reduced excursion. Glycerol added to increase viscosity slowed confined diffusion of the tethered beads but did not change excursion. The confined-diffusion coefficients for all tethered beads were smaller than those expected for freely diffusing beads and decreased for shorter tethers. Tethered-particle motion is a sensitive framework for diffusion experiments in which small beads on long leashes most closely resemble freely diffusing, untethered beads. PMID:24461015

  19. Manipulating assembly of nanoparticles by polymer tethers

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenli; Horsch, Mark; Iacovella, Christopher; Glotzer, Sharon

    2006-03-01

    A major challenge in nanoscience and nanotechnology is the ability to control and guide the self-assembly of nano building blocks into target structures in a predictable way. In this talk, we use molecular simulation to show how polymer tethers can be used to manipulate the assembly of nanoparticles into various one-dimensional, two-dimensional, and three-dimensional structures. We present results on the self-assembly of polymer-tethered nanospheres, nanorods, and more exotic shapes, and present temperature versus concentration phase diagrams for the nanosphere and nanorod systems. For polymer-tethered nanorods we predict tetragonally perforated lamellar and honeycomb phases, which have been observed experimentally but have not been predicted by any previous theory. We also predict a new phase---a racemic mixture of hexagonally ordered chiral cylinders that self-assemble from these achiral building blocks. For the system of polymer-tethered nanospheres we predict that in contrast to flexible amphiphiles, the nanospheres are locally ordered and there is an increase in the local ordering with an increase in concentration or relative nanoparticle diameter. [1] Zhang, Mark A. Horsch, Monica H. Lamm, and Sharon C. Glotzer, Nano Lett., 3(10), 1341-1346, 2003. [2] Mark A. Horsch, Zhenli Zhang and Sharon C. Glotzer, Phys. Rev. Lett., 95(5), 056106, 2005. [3] Christopher R. Iacovella, Mark A. Horsch, Zhenli Zhang and Sharon C. Glotzer, Langmuir, 21(21), 9488, 2005.

  20. 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.

  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. Cell Cytoskeleton and Tether Extraction

    PubMed Central

    Pontes, B.; Viana, N.B.; Salgado, L.T.; Farina, M.; Neto, V. Moura; Nussenzveig, H.M.

    2011-01-01

    We perform a detailed investigation of the force × deformation curve in tether extraction from 3T3 cells by optical tweezers. Contrary to conventional wisdom about tethers extracted from cells, we find that actin filaments are present within them, so that a revised theory of tether pulling from cells is called for. We also measure steady and maximum tether force values significantly higher than previously published ones for 3T3 cells. Possible explanations for these differences are investigated. Further experimental support of the theory of force barriers for membrane tube extension is obtained. The potential of studies on tether pulling force × deformation for retrieving information on membrane-cytoskeleton interaction is emphasized. PMID:21723813

  3. Spin augmented deployment and retrieval of tethered artificial gravity spacecraft

    NASA Astrophysics Data System (ADS)

    Stoen, Jeffrey Donald

    The dynamics and control of a tethered centrifuge during constant spin deployment and retrieval of the tether is investigated. First, a simple two segment tether model is used to demonstrate that tangential thrusters on the end bodies can maintain a constant centrifuge spin rate and provide the control action necessary to damp lateral oscillations of the tether. An LQR controller is devised to create a balanced control scheme that provides such coordination between actuators as is required to produce a comfortable environment for occupants of the centrifuge. Next, the stability of motions of the tether end bodies is studied to assess effects of varying the body's mass properties and the position of the tether attachment joint. Finally, an improved, multi-segment model of the tether is employed to deal with limitations due to imperfect monitoring of the state of the system and difficulties in delivering accurate thrust levels. We construct a Kalman filter to furnish both estimates for the unknown states and smoothing of noisy measurements of sensed states.

  4. 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.

  5. Propulsive Small Expendable Deployer System (ProSEDS)

    NASA Technical Reports Server (NTRS)

    Curtis, Leslie; Johnson, Les; Brown, Norman S. (Technical Monitor)

    2002-01-01

    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 11 Expendable Launch Vehicle second stage. ProSEDS, which is planned on an Air Force GPS Satellite replacement mission in June 2002, will use the flight proven Small Expendable Deployer System (SEDS) to deploy a tether (5 km bare wire plus 10 km non-conducting Dyneema) from a Delta 11 second stage to achieve approx. 0.4N drag thrust. ProSEDS will utilize the tether-generated current to provide limited spacecraft power. The ProSEDS instrumentation includes Langmuir probes and Differential Ion Flux Probes, 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 removal 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. Extended symmetrical classical electrodynamics.

    PubMed

    Fedorov, A V; Kalashnikov, E G

    2008-03-01

    In this paper, we discuss a modification of classical electrodynamics in which "ordinary" point charges are absent. The modified equations contain additional terms describing the induced charges and currents. The densities of the induced charges and currents depend on the vector k and the vectors of the electromagnetic field, E and B . It is shown that the vectors E and B can be defined in terms of two four-potentials and the components of k are the components of a four-tensor of the third rank. The Lagrangian of the modified electrodynamics is defined. The conditions are derived at which only one four-potential determines the behavior of the electromagnetic field. It is also shown that static modified electrodynamics can describe the electromagnetic field in the inner region of an electric monopole. In the outer region of the electric monopole the electric field is governed by the Maxwell equations. It follows from boundary conditions at the interface between the inner and outer regions of the monopole that the vector k has a discrete spectrum. The electric and magnetic fields, energy, and angular momentum of the monopole are found for different eigenvalues of k .

  7. 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

  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. Introduction of luminescent rhenium(I), ruthenium(II), iridium(III) and rhodium(III) systems into rhodamine-tethered ligands for the construction of bichromophoric chemosensors.

    PubMed

    Wang, Chunyan; Lam, Ho-Chuen; Zhu, Nianyong; Wong, Keith Man-Chung

    2015-09-14

    Several classes of luminescent transition metal complexes, including rhenium(I) tricarbonyl diimine, ruthenium(II) diimine, cyclometallated iridium(III) and rhodium(III) diimine, as well as ruthenium(II) and iridium(III) terpyridine systems, tethered with rhodamine moieties, have been synthesized and characterized. The X-ray crystal structure of one cyclometallated rhodium(III) diimine (11) with a rhodamine pendant was determined. Most of the complexes were found to exhibit emission in fluid solution at room temperature. Depending on the nature of the transition metal system, the emission origin was mainly assigned to be derived from the triplet excited state of the metal-to-ligand charge transfer ((3)MLCT) or the intraligand ((3)IL) transition. The cation-binding properties of these complexes toward various cations were investigated by electronic absorption and emission spectroscopy. Some of them were found to exhibit new low-energy absorption and emission bands, attributed to the ring opening of the rhodamine moiety, with high selectivity and/or high sensitivity for various cations, in agreement with sensing and spectroscopic behaviours of the rhodamine derivative. Depending on the nature of the transition metal centres, the chelating ligands as well as the linker to the rhodamine derivative, different sensing properties in terms of selectivity, sensitivity and binding stability, could be obtained.

  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. 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

  13. 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.

  14. Brownian motion of tethered nanowires.

    PubMed

    Ota, Sadao; Li, Tongcang; Li, Yimin; Ye, Ziliang; Labno, Anna; Yin, Xiaobo; Alam, Mohammad-Reza; Zhang, Xiang

    2014-05-01

    Brownian motion of slender particles near a boundary is ubiquitous in biological systems and in nanomaterial assembly, but the complex hydrodynamic interaction in those systems is still poorly understood. Here, we report experimental and computational studies of the Brownian motion of silicon nanowires tethered on a substrate. An optical interference method enabled direct observation of microscopic rotations of the slender bodies in three dimensions with high angular and temporal resolutions. This quantitative observation revealed anisotropic and angle-dependent hydrodynamic wall effects: rotational diffusivity in inclined and azimuth directions follows different power laws as a function of the length, ∼ L(-2.5) and ∼ L(-3), respectively, and is more hindered for smaller inclined angles. In parallel, we developed an implicit simulation technique that takes the complex wire-wall hydrodynamic interactions into account efficiently, the result of which agreed well with the experimentally observed angle-dependent diffusion. The demonstrated techniques provide a platform for studying the microrheology of soft condensed matters, such as colloidal and biological systems near interfaces, and exploring the optimal self-assembly conditions of nanostructures. PMID:25353883

  15. 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.

  16. 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.

  17. 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.

  18. Mesoscopic cavity quantum electrodynamics with quantum dots

    SciTech Connect

    Childress, L.; Soerensen, A.S.; Lukin, M.D.

    2004-04-01

    We describe an electrodynamic mechanism for coherent, quantum-mechanical coupling between spatially separated quantum dots on a microchip. The technique is based on capacitive interactions between the electron charge and a superconducting transmission line resonator, and is closely related to atomic cavity quantum electrodynamics. We investigate several potential applications of this technique which have varying degrees of complexity. In particular, we demonstrate that this mechanism allows design and investigation of an on-chip double-dot microscopic maser. Moreover, the interaction may be extended to couple spatially separated electron-spin states while only virtually populating fast-decaying superpositions of charge states. This represents an effective, controllable long-range interaction, which may facilitate implementation of quantum information processing with electron-spin qubits and potentially allow coupling to other quantum systems such as atomic or superconducting qubits.

  19. Radiative corrections in symmetrized classical electrodynamics

    PubMed

    Van Meter JR; Kerman; Chen; Hartemann

    2000-12-01

    The physics of radiation reaction for a point charge is discussed within the context of classical electrodynamics. The fundamental equations of classical electrodynamics are first symmetrized to include magnetic charges: a double four-potential formalism is introduced, in terms of which the field tensor and its dual are employed to symmetrize Maxwell's equations and the Lorentz force equation in covariant form. Within this framework, the symmetrized Dirac-Lorentz equation is derived, including radiation reaction (self-force) for a particle possessing both electric and magnetic charge. The connection with electromagnetic duality is outlined, and an in-depth discussion of nonlocal four-momentum conservation for the wave-particle system is given.

  20. 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.

  1. Pulsar electrodynamics: an unsolved problem

    NASA Astrophysics Data System (ADS)

    Melrose, D. B.; Yuen, R.

    2016-04-01

    > Pulsar electrodynamics is reviewed emphasizing the role of the inductive electric field in an oblique rotator and the incomplete screening of its parallel component by charges, leaving `gaps' with \\Vert \

  2. 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.

  3. 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.

  4. 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).

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Optimal control of a spinning double-pyramid Earth-pointing tethered formation

    NASA Astrophysics Data System (ADS)

    Williams, Paul

    2009-06-01

    The dynamics and control of a tethered satellite formation for Earth-pointing observation missions is considered. For most practical applications in Earth orbit, a tether formation must be spinning in order to maintain tension in the tethers. It is possible to obtain periodic spinning solutions for a triangular formation whose initial conditions are close to the orbit normal. However, these solutions contain significant deviations of the satellites on a sphere relative to the desired Earth-pointing configuration. To maintain a plane of satellites spinning normal to the orbit plane, it is necessary to utilize "anchors". Such a configuration resembles a double-pyramid. In this paper, control of a double-pyramid tethered formation is studied. The equations of motion are derived in a floating orbital coordinate system for the general case of an elliptic reference orbit. The motion of the satellites is derived assuming inelastic tethers that can vary in length in a controlled manner. Cartesian coordinates in a rotating reference frame attached to the desired spin frame provide a simple means of expressing the equations of motion, together with a set of constraint equations for the tether tensions. Periodic optimal control theory is applied to the system to determine sets of controlled periodic trajectories by varying the lengths of all interconnecting tethers (nine in total), as well as retrieval and simple reconfiguration trajectories. A modal analysis of the system is also performed using a lumped mass representation of the tethers.

  11. 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.

  12. 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.

  13. Mesoscale modeling and computer simulation of tethered nanorod "shape amphiphile" assemblies

    NASA Astrophysics Data System (ADS)

    Horsch, Mark A.

    The goal of this thesis is to elucidate the parameters that strongly influence the self-assembled morphologies formed by tethered nanoparticle, "shape amphiphiles". Minimal models are developed which capture the geometry and rigidity of the particles, the immiscibility between the particle and tether, and the tether connectivity and flexibility. This work focuses on the self-assembly of tethered rods a class of shape amphiphile where the rigid block is rod-like. The work presented here demonstrates that in addition to forming micelles, cylinders, bicontinuous, and sheet-like morphologies additional local ordering arises due to the geometry or anisotropy of the rigid block. For example, at high concentrations tethered rods are observed to form monolayer smectic morphologies when the solvent is good for the tether and poor for the rod, while, mono-tethered spheres self-assemble into bilayer structures. The number of tethers also influences the self-assembly. For example, di-tethered spheres self-assemble into monolayers in contrast to the bilayers formed when only a single tether is attached to the sphere. For the tethered rods in selective solvent, our simulations predict several novel phases. In the case of end-tethered rods, a novel hexagonally arranged chiral cylinder morphology was observed. Other morphologies such as the tetragonally perforated and hexagonally perforated lamellar phases were observed. These phases have been observed in experimental rod coil copolymers but have not been previously predicted by simulation or theory. In the case of side-tethered rods several novel phases have been identified in this work including rectangular centered stepped ribbons, and bilayer phases, one with P2 symmetry and the other with Cmm symmetry, are predicted. Of particular interest may be the orientation of the rods in the stepped ribbon phase, wherein the long axis of the rod is parallel to the major axis of the ribbon. For end-tethered rods in a neat system two

  14. 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.

  15. Experimental demonstration of offset control with an application to the tethered payload

    NASA Astrophysics Data System (ADS)

    Modi, V. J.; Lakshmanan, P. K.; Misra, A. K.; Picha, R. J.; Chan, S.; Vakil, S.

    1989-05-01

    A control law for tethered satellite systems was proposed that uses a boom-trolley arrangement that allows the point of attachment of the tether to be moved in three orthogonal directions. This means that the position, velocity and acceleration of the tether attachment point, become specified quantities in the dynamical formulation. The accelerations are integrated along each axis to obtain the corresponding velocities and positions. A tethered satellite system model was developed to demonstrate the offset control strategy in real time. A variety of tether configurations, retrieval rates, and initial conditions were employed to systematically test the controller's effectiveness. Even at large initial conditions the controller proved very successful in bringing the tether to its equilibrium configuration. This clearly demonstrated the robustness of the control algorithm. The effectiveness increased as the tether length diminished which makes it particularly attractive in situations where other controllers have limitations. It is expected that a hybrid control strategy with thruster/tension control at large tether lengths followed by offset control near the platform end during the final stages of retrieval would be most effective.

  16. 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.

  17. Cell Protrusions and Tethers: A Unified Approach

    PubMed Central

    Pospieszalska, Maria K.; Lasiecka, Irena; Ley, Klaus

    2011-01-01

    Low pulling forces applied locally to cell surface membranes produce viscoelastic cell surface protrusions. As the force increases, the membrane can locally separate from the cytoskeleton and a tether forms. Tethers can grow to great lengths exceeding the cell diameter. The protrusion-to-tether transition is known as the crossover. Here we propose a unified approach to protrusions and tethers providing, to our knowledge, new insights into their biomechanics. We derive a necessary and sufficient condition for a crossover to occur, a formula for predicting the crossover time, conditions for a tether to establish a dynamic equilibrium (characterized by constant nonzero pulling force and tether extension rate), a general formula for the tether material after crossover, and a general modeling method for tether pulling experiments. We introduce two general protrusion parameters, the spring constant and effective viscosity, valid before and after crossover. Their first estimates for neutrophils are 50 pN μm−1 and 9 pN s μm−1, respectively. The tether elongation after crossover is described as elongation of a viscoelastic-like material with a nonlinearly decaying spring (NLDs-viscoelastic material). Our model correctly describes the results of the published protrusion and tether pulling experiments, suggesting that it is universally applicable to such experiments. PMID:21463583

  18. 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.

  19. 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.

  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. 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.

  2. 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.

  3. 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.

  4. 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…

  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. 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.

  7. 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.

  8. 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.

  9. Tethered Communication Satellites

    NASA Technical Reports Server (NTRS)

    Von Tiesenhausen, G.

    1986-01-01

    Report describes concept for placing several communication satellites in geostationary orbit without taking up more space than assigned to single satellite. Proposed scheme eases orbital crowding more economically than space platforms. Concept requires minimal redesign of existing satellites and accommodates many satellites in just one orbital slot. System much lighter in weight than geostationary platform and easier and more economical to transport.

  10. 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.

  11. The constitutive equation for membrane tether extraction.

    PubMed

    Chen, Yong; Yao, Da-Kang; Shao, Jin-Yu

    2010-12-01

    Membrane tethers or nanotubes play a critical role in a variety of cellular and subcellular processes such as leukocyte rolling and intercellular mass transport. The current constitutive equations that describe the relationship between the pulling force and the tether velocity during tether extraction have serious limitations. In this article, we propose a new phenomenological constitutive equation that captures all known characteristics of nanotube formation, including nonlinearity, nonzero threshold force, and possible negative tether velocity. We used tether extraction from endothelial cells as a prototype to illustrate how to obtain the material constants in the constitutive equation. With the micropipette aspiration technique, we measured tether pulling forces at both positive and negative tether velocities. We also determined the threshold force of 55 pN experimentally for the first time. This new constitutive equation unites two established ones and provides us a unified platform to better understand not only the physiological role of tether extraction during leukocyte rolling and intercellular or intracellular transport, but also the physics of membrane tether growth or retraction.

  12. Coupled Translational and Rotational Fluctuations of Tethered Beads

    NASA Astrophysics Data System (ADS)

    Spakowitz, Andrew; Mehraeen, Shafigh

    2008-03-01

    Single-molecule manipulation plays an important role in determining the physical mechanisms responsible for biological function. Establishing a robust method of predicting the fluctuating behavior of a tethered bead provides insight into how to maximize the signal-to-noise ratio to improve experimental resolution. We theoretically address the behavior of single-molecule experimental apparatuses. Our theory is amenable to addressing a variety of different bead-tether systems, thus providing a basis for comparing and contrasting these different experimental setups and for adapting the theory to the specific experimental system of interest. Fluctuations in both the location and orientation of the bead are incorporated in the theory; we explore their coupled effect on the observed behavior in single-molecule systems. The physical behavior of the tether molecule is described using the wormlike chain model. Making use of our exact solutions for wormlike chain model statistics, our current treatment achieves exact precision for the polymer behavior, apart from the approximations that are inherent to the wormlike chain model. We find that the impact of rotational fluctuations on the bead motion is largest when the radius of the bead is comparable to the length of the chain tether. We explore the impact that chain length and bead radius have on the resolution of single-molecule experiments and how to maximize the signal-to-noise ratio.

  13. Dynamic analysis and trajectory tracking of a tethered space robot

    NASA Astrophysics Data System (ADS)

    Soltani, Mehrzad; Keshmiri, Mehdi; Misra, Arun K.

    2016-11-01

    Dynamic analysis and trajectory tracking of a Tethered Space Robot (TSR) is investigated in this paper. A hybrid controller is used to perform the control task. It consists of two components, the first one deals with librational motion of the tether, while the second one takes care of the manipulator motion. A Nonlinear Model Predictive Control (NMPC) approach is used to control the tether libration; for this purpose, the libration is described by a single degree of freedom and the tether length rate is employed as the input to suppress the librational motion. A modified Computed Torque Method (CTM) is used to control the manipulator motion. The dynamic interaction between the manipulator motion and the librational motion is considered both in the system dynamics and control of the system. Using numerical simulations, performance of the proposed control system is evaluated for end-effector positioning as well as for trajectory tracking for two cases: a Low Earth Orbit (LEO) and the Geostationary Earth Orbit (GEO).

  14. 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.

  15. Analytical solution for extensible tethers

    NASA Technical Reports Server (NTRS)

    Eades, J. B., Jr.

    1974-01-01

    The mathematical model considers a large particle (m sub 1), such as a space station, and a smaller particle (m sub 2), connected by an ideal, massless tether, i.e., one incapable of sustaining other than tensile loads. The problem situation described offers a practical solution which should be quite useful in certain space flight operations, especially for the transfer of cargo and personnel and for retrieval and rescue operations. The idea is simple in its application and does not appear to require sophisticated hardware. An appealing advantage is that it is infinitely reusable, i.e., it could be rewound and used over and over again.

  16. 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.)

  17. 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.

  18. 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.

  19. 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.

  20. Where are We Going in Tethers

    NASA Technical Reports Server (NTRS)

    Colombo, G.

    1985-01-01

    The state of the art of the tether in space science and in space operations is discussed. It is emphasized that space technology is not the continuation of aerodynamics, but rather is something fundamentally distinct. The tether is foreseen as a basic structural element for aerospace engineering in the future.

  1. 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).

  2. Eukaryotic membrane tethers revisited using magnetic tweezers

    NASA Astrophysics Data System (ADS)

    Hosu, Basarab G.; Sun, Mingzhai; Marga, Françoise; Grandbois, Michel; Forgacs, Gabor

    2007-06-01

    Membrane nanotubes, under physiological conditions, typically form en masse. We employed magnetic tweezers (MTW) to extract tethers from human brain tumor cells and compared their biophysical properties with tethers extracted after disruption of the cytoskeleton and from a strongly differing cell type, Chinese hamster ovary cells. In this method, the constant force produced with the MTW is transduced to cells through super-paramagnetic beads attached to the cell membrane. Multiple sudden jumps in bead velocity were manifest in the recorded bead displacement-time profiles. These discrete events were interpreted as successive ruptures of individual tethers. Observation with scanning electron microscopy supported the simultaneous existence of multiple tethers. The physical characteristics, in particular, the number and viscoelastic properties of the extracted tethers were determined from the analytic fit to bead trajectories, provided by a standard model of viscoelasticity. Comparison of tethers formed with MTW and atomic force microscopy (AFM), a technique where the cantilever-force transducer is moved at constant velocity, revealed significant differences in the two methods of tether formation. Our findings imply that extreme care must be used to interpret the outcome of tether pulling experiments performed with single molecular techniques (MTW, AFM, optical tweezers, etc). First, the different methods may be testing distinct membrane structures with distinct properties. Second, as soon as a true cell membrane (as opposed to that of a vesicle) can attach to a substrate, upon pulling on it, multiple nonspecific membrane tethers may be generated. Therefore, under physiological conditions, distinguishing between tethers formed through specific and nonspecific interactions is highly nontrivial if at all possible.

  3. Eukaryotic membrane tethers revisited using magnetic tweezers.

    PubMed

    Hosu, Basarab G; Sun, Mingzhai; Marga, Françoise; Grandbois, Michel; Forgacs, Gabor

    2007-04-19

    Membrane nanotubes, under physiological conditions, typically form en masse. We employed magnetic tweezers (MTW) to extract tethers from human brain tumor cells and compared their biophysical properties with tethers extracted after disruption of the cytoskeleton and from a strongly differing cell type, Chinese hamster ovary cells. In this method, the constant force produced with the MTW is transduced to cells through super-paramagnetic beads attached to the cell membrane. Multiple sudden jumps in bead velocity were manifest in the recorded bead displacement-time profiles. These discrete events were interpreted as successive ruptures of individual tethers. Observation with scanning electron microscopy supported the simultaneous existence of multiple tethers. The physical characteristics, in particular, the number and viscoelastic properties of the extracted tethers were determined from the analytic fit to bead trajectories, provided by a standard model of viscoelasticity. Comparison of tethers formed with MTW and atomic force microscopy (AFM), a technique where the cantilever-force transducer is moved at constant velocity, revealed significant differences in the two methods of tether formation. Our findings imply that extreme care must be used to interpret the outcome of tether pulling experiments performed with single molecular techniques (MTW, AFM, optical tweezers, etc). First, the different methods may be testing distinct membrane structures with distinct properties. Second, as soon as a true cell membrane (as opposed to that of a vesicle) can attach to a substrate, upon pulling on it, multiple nonspecific membrane tethers may be generated. Therefore, under physiological conditions, distinguishing between tethers formed through specific and nonspecific interactions is highly nontrivial if at all possible.

  4. 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.

  5. Some problems of classical electrodynamics

    NASA Astrophysics Data System (ADS)

    Ginzburg, I. F.

    2011-12-01

    In this lecture, I discuss issues that usually escape attention of students in electrodynamics. These are the questions of (1) what the photon observed in nature "looks like," (2) how an interference pattern arises from a source containing a lot of incoherently emitting atoms, and (3) how light "slows down" in a medium. Answers to these questions, if discussed at all, are scattered over various textbooks. Here, I follow our textbook [1].

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Tethered Capturing Scenarios in Low Earth Orbit

    NASA Astrophysics Data System (ADS)

    Keramati Nigjeh, Behzad; Trivailo, Pavel; Blanksby, Chris

    To-date, a few actuation methods have been presented which enable zero differential velocity rendezvous for the tip of a space tether and a payload. Some researchers in the field have also investigated the futuristic, ambitious, tethered capturing scenarios for interplanetary transfers. This paper investigates some new and beneficial tethered space capturing scenarios, which can be implemented for near-term space mass/momentum transfer missions in Low Earth Orbit (LEO), by using currently available technology and resources. Zero differential velocity capture could be achieved by initiating a swinging motion in the tether before rendezvous. The lack of significant damping forces in space, means the swinging motion continues after capture, which is extremely undesirable for the retrieval phase and poses a serious danger for the platform as the payload approaches to it. Although exploiting space propulsion on the capturing device at the tip of the tether could stop the swinging motion of the tether directly after the capture, another alternative presented in this paper is to use the space propulsion to boost the payload to the same orbit as the platform. This has the benefit of dramatically reducing fuel consumption and accomplishment of the retrieval phase with low risk of impact to the platform. The numerical methods utilized in the dynamic simulation have been used to evaluate the efficiency of the tethered capturing scenarios mentioned above in comparison to the direct space capture and ideal Hohmann orbit transfer. The payload mass addition to the tip of the elastic tether at capture causes a longitudinal vibration mode (Bobbing mode) in the tether. Since the structural damping in the tether is negligible, a precise length rate/tension control could be used to dampen this mode in the first semi-period, demolishing any subsequent tension peak. This is a new mathematical non-linear control scheme, which is described for tension mitigation and damping of Bobbing

  11. 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.

  12. 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.

  13. Large- and Small-Scale Ring Current Electrodynamic Coupling

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.

    2003-01-01

    In this talk we will address the two primary issues of ring current (RC) electrodynamic coupling: 1. RC self-consistent magnetosphere-ionosphere coupling that includes calculation of the magnetospheric electric field (large scale electrodynamic coupling); and 2. RC self-consistent coupling with electromagnetic ion cyclotron (EMIC) waves (small scale electrodynamic coupling). Our study will be based on two RC models that we have recently developed in our group. The first model by Khazanov et al. [2002] couples the system of two kinetic equations: one equation which describes the RC ion dynamics and another equation which describes the energy density evolution of EMIC waves. The second model by Khazanov et al. [2003] deals with large scale electrodynamic coupling processes and provides a self-consistent simulation of RC ions and the magnetospheric electric field. There is presently no model that addresses both of these issues simultaneously in a self-consistent calculation. However, the need exists for such a model, because these two processes directly influence each other, with the mesoscale coupling changing the drift paths of the thermal and energetic particle populations in the inner magnetosphere, thereby changing the wave interactions, and the microscale coupling altering the pitch angle distributions and ionospheric conductivities (through increased precipitation), thus changing the field-aligned currents and electric potential structure. The initial thrust of the work will be the development of a combined kinetic model of micro- and meso-scale RC electrodynamic coupling processes and to examine their interactions with each other on a global scale.

  14. 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.

  15. 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.

  16. 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.

  17. Crowded, confined, and frustrated: dynamics of molecules tethered to nanoparticles.

    PubMed

    Agarwal, Praveen; Kim, Sung A; Archer, Lynden A

    2012-12-21

    Above a critical chemistry-dependent molecular weight, all polymer molecules entangle and, as a result, exhibit slow dynamics, enhanced viscosity, and elasticity. Herein we report on the dynamics of low molecular weight polymers tethered to nanoparticles and find that even conventionally unentangled chains manifest dynamical features similar to entangled, long-chain molecules. Our findings are shown to imply that crowding and confinement of polymers on particles produce topological constraints analogous to those in entangled systems.

  18. Tethered space recovery vehicle deployment/re-entry demonstration

    NASA Technical Reports Server (NTRS)

    Florence, D.

    1988-01-01

    The feasibility of utilizing existing Space Re-entry Vehicle (SRV) hardware for a Shuttle Orbiter-based tethered SRV deployment and re-entry demonstration using the Small Expendable Deployer System has been investigated. Options for mounting the SRV in the Orbiter, modifications and additions required to the existing SRV hardware have been defined. Flight demonstration scenarios from the Orbiter have been investigated, and re-entry motion and targeting uncertainties have been determined.

  19. 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...

  20. 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.

  1. 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.

  2. 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

  3. Fluidic electrodynamics: Approach to electromagnetic propulsion

    SciTech Connect

    Martins, Alexandre A.; Pinheiro, Mario J.

    2009-03-16

    We report on a new methodological approach to electrodynamics based on a fluidic viewpoint. We develop a systematic approach establishing analogies between physical magnitudes and isomorphism (structure-preserving mappings) between systems of equations. This methodological approach allows us to give a general expression for the hydromotive force, thus re-obtaining the Navier-Stokes equation departing from the appropriate electromotive force. From this ground we offer a fluidic approach to different kinds of issues with interest in propulsion, e.g., the force exerted by a charged particle on a body carrying current; the magnetic force between two parallel currents; the Magnus's force. It is shown how the intermingle between the fluid vector fields and electromagnetic fields leads to new insights on their dynamics. The new concepts introduced in this work suggest possible applications to electromagnetic (EM) propulsion devices and the mastery of the principles of producing electric fields of required configuration in plasma medium.

  4. 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.

  5. Radio pulsar disk electrodynamics

    SciTech Connect

    Michel, F.C.

    1983-03-01

    We outline the macroscopic physics of a disk close to an isolated, magnetized, rotating neutron star. It seems likely that such systems are formed from time to time in the universe. The neutron star acts as a Faraday disk dynamo, and the disk acts as both a load and a neutral sheet, permitting the polar cap current to return to the neutron star and also splitting a dipolar magnetic field into two monopolar halves. Michel and Dessler have proposed that such systems are radio pulsars. The dominant energy loss is from the stellar wind torque (giving a deceleration index n = 7/3), and the next contribution is dissipation in the ''auroral'' zones, where the current returns to the star in a sheet about 5 cm thick. The latter is comparable to the observed radio luminosities and is in reasonable accord with the data. The disk itself may be a source of visible radiation comparable to that in pulsed radiofrequency emission. As the pulsar ages, the disk expands and narrows into a ring, the plausible consequence of which could be cessation of pulsed emission at periods of a few seconds.

  6. Towards hybrid circuit quantum electrodynamics with quantum dots

    NASA Astrophysics Data System (ADS)

    Viennot, Jérémie J.; Delbecq, Matthieu R.; Bruhat, Laure E.; Dartiailh, Matthieu C.; Desjardins, Matthieu M.; Baillergeau, Matthieu; Cottet, Audrey; Kontos, Takis

    2016-08-01

    Cavity quantum electrodynamics allows one to study the interaction between light and matter at the most elementary level. The methods developed in this field have taught us how to probe and manipulate individual quantum systems like atoms and superconducting quantum bits with an exquisite accuracy. There is now a strong effort to extend further these methods to other quantum systems, and in particular hybrid quantum dot circuits. This could turn out to be instrumental for a noninvasive study of quantum dot circuits and a realization of scalable spin quantum bit architectures. It could also provide an interesting platform for quantum simulation of simple fermion-boson condensed matter systems. In this short review, we discuss the experimental state of the art for hybrid circuit quantum electrodynamics with quantum dots, and we present a simple theoretical modeling of experiments.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Dusty Plasma Experiments Using an Electrodynamic Balance

    NASA Technical Reports Server (NTRS)

    Spann, J. F.; Abbas, M. M.; Suess, S. T.; Venturini, C. C.; Comfort, R. H.

    2000-01-01

    Knowledge of the formation, distribution, physical, chemical and optical characteristics of interstellar, interplanetary, and planetary dust grains provide valuable information about many issues dealing with the origin and formation of the solar system bodies, interplanetary and interstellar environments as well as various industrial processes. Understanding the microphysics of individual grains and their interaction with the surrounding environment is key to properly model various conditions and interpret existing data. The theory and models of individual dust grains are well developed for environments that vary from dense planetary atmospheres to dusty plasmas to diffuse environments such is interplanetary space. However, experimental investigations of individual dust grains in equilibrium are less common, perhaps due to the difficult of these experiments. Laboratory measurements of dust grains have primarily measured ensemble properties or transient properties of single grains. A technique developed in the 1950's for ion spectroscopy, known as a quadrupole trap or 'Paul Trap', has recently been used to investigate single micron-sized dust grains. This scaled ion trap called an electrodynamic balance has been used for atmospheric aerosol research. A description of this technique is provided. Recent results from experiments to investigate the equilibrium potential of dust grains exposed to far ultraviolet light or to -,in electron or ion beam are presented. This laboratory technique ]ends itself to many applications that relate to planetary atmospheres, heliospheric environments, pre-stellar and pre-planetary conditions, and industrial settings. Several planned experimental approaches are presented. Potential experiments to investigate the interaction of multiple dust grains using an electrodynamic balance are proposed.

  12. Electrostatic and electrodynamic response properties of nanostructures

    NASA Astrophysics Data System (ADS)

    Ayaz, Yuksel

    1999-11-01

    This thesis addresses the problem of nanostructure dielectric response to excitation by electric fields, both in the electrostatic c→infinity and the electrodynamic regimes. The nanostructures treated include planar quantum wells and quantum wires embedded in the vicinity of the bounding surface of the host semiconductor medium. Various cases are analyzed, including a single well or wire, a double well or wire, a lattice of N wells or wires and an infinite superlattice of wells or wires. The host medium is considered to have phonons and/or a bulk semiconductor plasma which interact with the plasmons of the embedded quantum wells or wires, and the host plasma is treated in both the local "cold" plasma regime and the nonlocal "hot" plasma regime. New hybridized quantum plasma collective modes emerge from these studies. The techniques employed here include the variational differential formulation of integral equations for the inverse dielectric function (in electrostatic case) and the dyadic Green's function (in the electrodynamic case) for the various systems described above. These integral equations are then solved in frequency-position representation by a variety of techniques depending on the geometrical features of the particular problem. Explicit closed form solutions for the inverse dielectric function or dyadic Green's function facilitate identification of the coupled collective modes in terms of their frequency poles, and the residues at the pole positions provide the relative amplitudes with which these normal modes respond to external excitation. Interesting features found include, for example, explicit formulas showing the transference of coupling of a two dimensional (2D) quantum well plasmon from a surface phonon to a bulk phonon as the 2D quantum well is displaced away from the bounding surface, deeper into the medium.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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

  20. Primordial magnetic fields and nonlinear electrodynamics

    SciTech Connect

    Kunze, Kerstin E.

    2008-01-15

    The creation of large scale magnetic fields is studied in an inflationary universe where electrodynamics is assumed to be nonlinear. After inflation ends electrodynamics becomes linear and thus the description of reheating and the subsequent radiation dominated stage are unaltered. The nonlinear regime of electrodynamics is described by Lagrangians having a power-law dependence on one of the invariants of the electromagnetic field. It is found that there is a range of parameters for which primordial magnetic fields of cosmologically interesting strengths can be created.

  1. 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.

  2. Teleportation of atomic states via cavity quantum electrodynamics

    NASA Astrophysics Data System (ADS)

    Guerra, E. S.

    2004-12-01

    In this paper, we discuss a scheme of teleportation of atomic states. The experimental realization proposed makes use of cavity quatum electrodynamics involving the interaction of Rydberg atoms with a micromaser cavity prepared in a coherent state. We start presenting a scheme to prepare atomic Bell states via the interaction of atoms with a cavity. In our scheme the cavity and some atoms play the role of auxiliary systems used to achieve the teleportation.

  3. High-voltage sheaths and charge neutralization in space power systems

    NASA Technical Reports Server (NTRS)

    Satyanarayana, P.; Chang, Chia-Lie; Drobot, Adam; Papadopoulos, Dennis

    1991-01-01

    The authors examine the electrodynamics of charged platforms in the ionosphere with a variety of analytical and numerical models. These models have been specifically designed to study the tethered satellite system (TSS-1) due to be launched in early 1992. One of the objectives of TSS-1 is to determine the potential of tethers for electrical power generation from orbital motion across the earth's magnetic field. The author identifies and explores important aspects of the interaction between the ambient ionospheric plasma and moving charged orbital platforms: (1) the formation of energetic particles in the wake of a nominally neutral satellite, (2) transient current collection by a highly charged platform, (3) the current closure paths in the ionosphere between multiple polarized platforms, and (4) the conditions for rapid neutralization by enhanced plasma formation in the presence of effluent gases.

  4. Fluctuational electrodynamics of hyperbolic metamaterials

    SciTech Connect

    Guo, Yu; Jacob, Zubin

    2014-06-21

    We give a detailed account of equilibrium and non-equilibrium fluctuational electrodynamics of hyperbolic metamaterials. We show the unifying aspects of two different approaches; one utilizes the second kind of fluctuation dissipation theorem and the other makes use of the scattering method. We analyze the near-field of hyperbolic media at finite temperatures and show that the lack of spatial coherence can be attributed to the multi-modal nature of super-Planckian thermal emission. We also adopt the analysis to phonon-polaritonic super-lattice metamaterials and describe the regimes suitable for experimental verification of our predicted effects. The results reveal that far-field thermal emission spectra are dominated by epsilon-near-zero and epsilon-near-pole responses as expected from Kirchoff's laws. Our work should aid both theorists and experimentalists to study complex media and engineer equilibrium and non-equilibrium fluctuations for applications in thermal photonics.

  5. Controlled Tethering Molecules via Crystal Surface Engineering

    NASA Astrophysics Data System (ADS)

    Cheng, Stephen Z. D.; Zheng, Joseph X.; Chen, William Y.

    2004-03-01

    So far, almost all experiments in tethering chain molecules onto substrates are via "grafting to" or "grafting from" polymerizations in addition to physical absorption. Issues concerning the uniformity of the tethered chain density and the molecular weight distribution of the chains tethered by polymerization always undermine the properties experimentally observed. We proposed a novel design to precisely control the tethering density of polystyrene (PS) brushes on a poly(ethylene oxide) (PEO) or a poly(L-lactic acid) (PLLA) lamellar crystal basal surface using PEO-b-PS or PLLA-b-PS diblock copolymers. As the crystallization temperature (Tc) increased in either a PEO-b-PS/mixed solution (chrolobenzene/octane) or a PLLA-b-PS/amyl acetate solution, the PEO or PLLA lamellar thickness (d) increased, and correspondingly, the number of folds per PEO or PLLA block was reduced. The reduced tethered density (Σ*) of the PS brushes thus increased. At an onset where the PS brushes are overcrowded within the solution, a drastic slope change in the relationship between (d)-1 and Tc occurs in both cases at a Σ* between 3 - 4. This illustrates that the weak to intermediate interaction changes of the PS brushes with their neighbors may be universally represented.

  6. Continuum electrodynamics and the Abraham-Minkowski momentum controversy

    NASA Astrophysics Data System (ADS)

    Crenshaw, Michael E.

    2015-08-01

    Continuum electrodynamics is an axiomatic formal theory based on the macroscopic Maxwell equations and the constitutive relations. We apply the formal theory to a thermodynamically closed system consisting of an antireection coated block of dielectric situated in free-space and illuminated by a quasimonochromatic field. We show that valid theorems of the formal theory are proven false by relativity and by conservation laws. Then the axioms of the formal theory are proven false at a fundamental level of mathematical logic. We derive a new formal theory of continuum electrodynamics for macroscopic electric and magnetic fields in a four-dimensional at non-Minkowski material spacetime in which the speed of light is c/n.

  7. Dendrimer light-harvesting: intramolecular electrodynamics and mechanisms.

    PubMed

    Andrews, David L; Bradshaw, David S; Jenkins, Robert D; Rodríguez, Justo

    2009-12-01

    In the development of highly efficient materials for harvesting solar energy, there is an increasing focus on purpose-built dendrimers and allied multi-chromophore systems. A proliferation of antenna chromophores is not the only factor determining the sought light-harvesting efficiency; the internal geometry and photophysics of these molecules are also crucially important. In particular, the mechanisms by means of which radiant energy is ultimately trapped depends on an intricate interplay of electronic, structural, energetic and symmetry properties. To better understand these processes a sound theoretical representation of the intramolecular electrodynamics is required. A suitable formalism, based on quantum electrodynamics, readily delivers physical insights into the necessary excitation channelling processes, and it affords a rigorous basis for modelling the intramolecular flow of energy.

  8. Electrodynamic Maglev coil design and analysis

    SciTech Connect

    Davey, K.R.

    1997-09-01

    Electrodynamic Maglev systems are distinguished from electromagnetic systems in that the currents yielding lift and guidance forces are induced by the movement of the vehicle. Above a threshold speed, such a system is inherently stable, and has the additional benefit of having greater flexibility to system construction tolerances in that the magnet vertical position can change by as much as 5 cm. A stacked magnet design is considered which couples into a set of interleave coils which are interconnected in such a way as to yield both lift and guidance forces. A mutual coupling analysis is embraced wherein the mutual inductance between the permanent magnets on board the vehicle and the coils are computed using closed form analytical expressions for filaments. The derivatives of these expressions are then averaged to compute both the induced current and the forces on the coils as a function of the system geometry and speed. A full transient analysis must be performed to accurately account for entry and exit effects. The results are compared to those experimentally measured on a test track and extrapolations are offered to suggest future design considerations.

  9. Space Station tethered refueling facility operations

    NASA Technical Reports Server (NTRS)

    Kiefel, E. R.; Rudolph, L. K.; Fester, D. A.

    1986-01-01

    The space-based orbital transfer vehicle will require a large cryogenic fuel storage facility at the Space Station. An alternative to fuel storage onboard the Space Station, is on a tethered orbital refueling facility (TORF) which is separated from the Space Station by a sufficient distance to induce a gravity gradient to settle the propellants. Facility operations are a major concern associated with a tethered LO2/LH2 storage depot. A study was carried out to analyze these operations so as to identify the preferred TORF deployment direction (up or down) and whether the TORF should be permanently or intermittently deployed. The analyses considered safety, contamination, rendezvous, servicing, transportation rate, communication, and viewing. An upwardly, intermittently deployed facility is the preferred configuration for a tethered cryogenic fuel storage.

  10. [Computer modeling of electrodynamic processes in SHF-based water disinfection and heating system as part of the spacecrew life support system].

    PubMed

    Klimarev, S I; Zaĭtsev, K A

    2012-01-01

    To optimize the design of SHF-based potable water disinfection and heating subsystem within the life support system (LSS), computer modeling of the super-high frequency electromagnetic field in SHF-based waveguide-coaxial and coaxial running water heaters was performed Software package CST Microwave Studio 2010 was used as the main instrument in the investigation. Results of the investigation can contribute to the development and prototyping of an HSF-based water heater as an integral part of advanced life support system for spacecrews

  11. Analytical investigation of the dynamics of tethered constellations in Earth orbit (phase 2)

    NASA Technical Reports Server (NTRS)

    Lorenzini, Enrico C.

    1987-01-01

    Simulation of two short distance crawling maneuvers of the elevator both with and without environmental perturbations acting upon the system is discussed. These simulation runs were performed in order to provide results useful for the interpretation of the data from the tests, on the ground, of a scaled down engineering model of the elevator. In these simulation runs the elevator crawls along the tether in accordance to the developed mirror image motion control law (MIMCL). Results from the simulation of the 4 km long maneuver run were compared to those obtained by adopting the modified hyperbolic tangent control law (MHTCL). A preprocessor was developed for setting up the initial conditions of a tethered system with L platforms, M longitudinal dampers, and N lumped masses (platforms plus tether beads). A short test run of the 4-platform system with 3 longitudinal dampers and 10 lumper mass without any perturbation acting upon the system is illustrated. In support of the Tether Applications Working Group, SAO is preparing a catalog of tether simulations, has prepared a set of simulator test cases, obtained results from SKYHOOK, and solicited results from simulators at other institutions, and prepared a paper on a specific analytic solution.

  12. Mesoscale modeling and computer simulation of tethered nanoparticle "Shape-amphiphile" assemblies

    NASA Astrophysics Data System (ADS)

    Iacovella, Christopher R.

    In this dissertation, we explore the use of polymer-tethered nanoparticles as a means to self-assemble highly ordered arrays of nanoparticles and nanometer-sized domains. We perform Brownian dynamics simulations to study the self-assembly of polymer functionalized spherical and rod-like nanoparticles. Immiscibility between tethers and nanoparticles facilitates assembly into highly ordered structures reminiscent of phases formed by surfactants and block copolymers, but with greater complexity. We explore the influence of key factors such as the nanoparticle size and shape, tether architecture, solvent selectivity, and bulk volume fraction on the resulting structures. In this thesis we perform several studies. First, we explore the phase behavior of mono-tethered nanospheres. Under solvent conditions that are poor for the tethers, we find phase behavior that is similar to surfactants with structures including lamellae, perforated lamellae, hexagonally packed cylinders, and spherical micelles. We report quasicrystalline-like ordering between the spherical micelles and propose an entropic model to explain this behavior. We also explore the phase behavior of a mono-tethered nanosphere system where nanospheres are in poor solvent. We find phases similar to surfactants including lamellae, perforated lamellae, double gyroid, and hexagonally packed cylinders. We see a predominance of icosahedral arrangements of nanospheres in phases with 2D confinement and crystalline packing of nanospheres in structures with 1D confinement. We also compare and contrast the formation of the double gyroid structure for tethered nanospheres and tethered nanorods. We show that the ability of the nanoparticles to locally order into icosahedra (nanospheres) and hexagonally splayed bundles (nanorods) reduces packing frustration making these structures more stable than their block copolymer counterparts. We also explore the phase behavior of di-tethered nanospheres. We find a complex phase

  13. CATCHR, HOPS and CORVET tethering complexes share a similar architecture.

    PubMed

    Chou, Hui-Ting; Dukovski, Danijela; Chambers, Melissa G; Reinisch, Karin M; Walz, Thomas

    2016-08-01

    We show here that the Saccharomyces cerevisiae GARP complex and the Cog1-4 subcomplex of the COG complex, both members of the complexes associated with tethering containing helical rods (CATCHR) family of multisubunit tethering complexes, share the same subunit organization. We also show that HOPS, a tethering complex acting in the endolysosomal pathway, shares a similar architecture, thus suggesting that multisubunit tethering complexes use related structural frameworks. PMID:27428774

  14. Protein synthesis by ribosomes with tethered subunits.

    PubMed

    Orelle, Cédric; Carlson, Erik D; Szal, Teresa; Florin, Tanja; Jewett, Michael C; Mankin, Alexander S

    2015-08-01

    The ribosome is a ribonucleoprotein machine responsible for protein synthesis. In all kingdoms of life it is composed of two subunits, each built on its own ribosomal RNA (rRNA) scaffold. The independent but coordinated functions of the subunits, including their ability to associate at initiation, rotate during elongation, and dissociate after protein release, are an established model of protein synthesis. Furthermore, the bipartite nature of the ribosome is presumed to be essential for biogenesis, since dedicated assembly factors keep immature ribosomal subunits apart and prevent them from translation initiation. Free exchange of the subunits limits the development of specialized orthogonal genetic systems that could be evolved for novel functions without interfering with native translation. Here we show that ribosomes with tethered and thus inseparable subunits (termed Ribo-T) are capable of successfully carrying out protein synthesis. By engineering a hybrid rRNA composed of both small and large subunit rRNA sequences, we produced a functional ribosome in which the subunits are covalently linked into a single entity by short RNA linkers. Notably, Ribo-T was not only functional in vitro, but was also able to support the growth of Escherichia coli cells even in the absence of wild-type ribosomes. We used Ribo-T to create the first fully orthogonal ribosome-messenger RNA system, and demonstrate its evolvability by selecting otherwise dominantly lethal rRNA mutations in the peptidyl transferase centre that facilitate the translation of a problematic protein sequence. Ribo-T can be used for exploring poorly understood functions of the ribosome, enabling orthogonal genetic systems, and engineering ribosomes with new functions.

  15. Non-US electrodynamic launchers research and development

    SciTech Connect

    Parker, J.V.; Batteh, J.H.; Greig, J.R.; Keefer, D.; McNab, I.R.; Zabar, Z.

    1994-11-01

    Electrodynamic launcher research and development work of scientists outside the United States is analyzed and assessed by six internationally recognized US experts in the field of electromagnetic and electrothermal launchers. The assessment covers five broad technology areas: (1) Experimental railguns; (2) Railgun theory and design; (3) Induction launchers; (4) Electrothermal guns; (5) Energy storage and power supplies. The overall conclusion is that non-US work on electrodynamic launchers is maturing rapidly after a relatively late start in many countries. No foreign program challenges the US efforts in scope, but it is evident that the United States may be surpassed in some technologies within the next few years. Until recently, published Russian work focused on hypervelocity for research purposes. Within the last two years, large facilities have been described where military-oriented development has been underway since the mid-1980s. Financial support for these large facilities appears to have collapsed, leaving no effective effort to develop practical launchers for military or civilian applications. Electrodynamic launcher research in Europe is making rapid progress by focusing on a single application, tactical launchers for the military. Four major laboratories, in Britain, France, Germany, and the Netherlands, are working on this problem. Though narrower in scope than the US effort, the European work enjoys a continuity of support that has accelerated its progress. The next decade will see the deployment of electrodynamic launcher technology, probably in the form of an electrothermal-chemical upgrade for an existing gun system. The time scale for deployment of electromagnetic launchers is entirely dependent on the level of research-and-development effort. If resources remain limited, the advantage will lie with cooperative efforts that have reasonably stable funding such as the present French-German program.

  16. Middle Atmosphere Electrodynamics (MAE). Middle atmospheric electrodynamics during MAP

    NASA Technical Reports Server (NTRS)

    Goldberg, R. A.

    1989-01-01

    The recent revival and strong motivation for research in middle atmospheric electrodynamics can be attributed, in large part, to the discovery of large (V/m) electric fields within the lower mesosphere during the decade prior to MAP. Subsequent rocket soundings appeared to verify the preliminary findings. During the MAP era, more sophisticated techniques have been employed to obtain measurements which respond positively to criticisms of earlier results, and which provide more insight regarding the character of the fields. The occurrence of mesospheric V/m electric fields now seems to require the presence of aerosols, of local winds and related dynamics, and of an atmospheric electrical conductivity less than 10(-10)S/m. Furthermore, new theoretical ideas describing the origin of the V/m fields are consistent with the measurements. The current status of results regarding V/m fields in the middle atmosphere is reviewed in light of the more widely accepted electric field structure for this region from rocket, balloon and modeling results.

  17. Electrodynamic Approach for Visualization of Sound Propagation in Solids

    NASA Astrophysics Data System (ADS)

    Völz, U.; Mrasek, H.; Matthies, K.; Wü; stenberg, H.; Kreutzbruck, M.

    2009-03-01

    The visualization of sound propagation in solids is vital for transducer adaptation and better understanding of complex test samples and their wave propagation modeling. In this work we present an electrodynamic technique detecting the grazing sound beam with a 10 mm-sized electrodynamic probe. The particle displacement along the sample's surface was then measured as a function of time and position. Adapting the electrodynamic probe and its coil alignment allows for measuring the displacement components in all three dimensions. Thus horizontal and vertical particle displacement with respect to the surface can be detected. A SNR of up to 40 dB could be achieved within ferromagnetic and high conductive chrome steel when using a shear wave generated by an angle beam probe. When dealing with nonconductive materials such as PMMA we obtained a reduced SNR of 12 dB. We report on measurements of the sound field in complex weld joints. One example shows a narrow gap weld joining a nickel alloy with a chrome steel. The weld of the 80 mm-thick test block shows a distinct anisotropic texture. The system enables us to visualize the wave propagation within the weld and indicates the reflection and scattering scenario and the energy losses due to both the anisotropic structure and material defects.

  18. Global ionospheric dynamics and electrodynamics during geomagnetic storms (Invited)

    NASA Astrophysics Data System (ADS)

    Mannucci, A. J.; Tsurutani, B.; Verkhoglyadova, O. P.; Komjathy, A.; Butala, M. D.

    2013-12-01

    Globally distributed total electron content (TEC) data has become an important tool for exploring the consequences of storm-time electrodynamics. Magnetosphere-ionosphere coupling during the main phase is responsible for the largest ionospheric effects observed during geomagnetic storms, mediated by global scale electrodynamics. Recent research using case studies reveals a complex picture of M-I coupling and its relationship to interplanetary drivers such as the solar wind electric field. Periods of direct coupling exist where the solar wind electric field is strongly correlated with prompt penetration electric fields, observed as enhanced vertical plasma drifts or an enhanced electrojet in the daytime equatorial ionosphere. Periods of decoupling between low latitude electric fields and the solar wind electric field are also observed, but the factors distinguishing these two types of response have not been clearly identified. Recent studies during superstorms suggest a role for the transverse (y-component) of the interplanetary magnetic field, which affects magnetospheric current systems and therefore may affect M-I coupling, with significant ionospheric consequences. Observations of the global ionospheric response to a range of geomagnetic storm intensities are presented. Scientific understanding of the different factors that affect electrodynamic aspects of M-I coupling are discussed.

  19. Tethered acoustic doppler current profiler platforms for measuring streamflow

    USGS Publications Warehouse

    Rehmel, Michael S.; Stewart, James A.; Morlock, Scott E.

    2003-01-01

    A tethered-platform design with a trimaran hull and 900-megahertz radio modems is now commercially available. Continued field use has resulted in U.S. Geological Survey procedures for making tethered-platform discharge measurements, including methods for tethered-boat deployment, moving-bed tests, and measurement of edge distances.

  20. Centralized Dynamics and Control of Novel Orbiting Formations of Tethered Spacecraft

    NASA Astrophysics Data System (ADS)

    Quadrelli, Marco B.; Hadaegh, Fred Y.

    acting as leader of the tethered formation. An application of this problem arises when a distributed sensor array formed by a chain of tethered data-gathering vehicles is being commanded to reconfigure from a remote location by the formation leader. Another application is in radar mapping where multiple free-flying vehicles synthesize multiple apertures with the main tethered vehicle for increased coverage. In this way, a centralized control architecture distributes the information flow among the members of the sensor array. Defining an orbiting formation as an ensemble of orbiting spacecraft performing a cooperative task, we point out that, until now, only spacecraft modeled as rigid bodies have been analyzed in the literature of orbiting formations and constellations. After the formation is in place, one may identify what is known as the virtual truss, i.e. the connection between the elements of the formation, which provides structural rigidity on account of the information flow between them. Our problem is different than conventional formation dynamics problems in that the presence of a tethered spacecraft within the formation demands an investigation of the dynamics coupling between spacecraft caused by tether viscoelasticity. The dynamics model takes into account the orbital and spacecraft dynamics of each vehicle. The control architecture features a separated spacecraft, which has visibility to the entire group of tethered vehicles. This vehicle is the leader of the formation, and ensures that the spacecraft on the tether remain connected and move according to a pre-specified program. The control system design consists of a proportional-derivative feedback plus acceleration feedforward. This ensures that modeling errors are compensated appropriately, and that the commanded slew is tracked accurately. The leader is also where the centralized estimator is located. This estimator continuously updates the state of the formation and estimates inter

  1. Yielding elastic tethers stabilize robust cell adhesion.

    PubMed

    Whitfield, Matt J; Luo, Jonathon P; Thomas, Wendy E

    2014-12-01

    Many bacteria and eukaryotic cells express adhesive proteins at the end of tethers that elongate reversibly at constant or near constant force, which we refer to as yielding elasticity. Here we address the function of yielding elastic adhesive tethers with Escherichia coli bacteria as a model for cell adhesion, using a combination of experiments and simulations. The adhesive bond kinetics and tether elasticity was modeled in the simulations with realistic biophysical models that were fit to new and previously published single molecule force spectroscopy data. The simulations were validated by comparison to experiments measuring the adhesive behavior of E. coli in flowing fluid. Analysis of the simulations demonstrated that yielding elasticity is required for the bacteria to remain bound in high and variable flow conditions, because it allows the force to be distributed evenly between multiple bonds. In contrast, strain-hardening and linear elastic tethers concentrate force on the most vulnerable bonds, which leads to failure of the entire adhesive contact. Load distribution is especially important to noncovalent receptor-ligand bonds, because they become exponentially shorter lived at higher force above a critical force, even if they form catch bonds. The advantage of yielding is likely to extend to any blood cells or pathogens adhering in flow, or to any situation where bonds are stretched unequally due to surface roughness, unequal native bond lengths, or conditions that act to unzip the bonds.

  2. Nonlinear electrodynamics and CMB polarization

    SciTech Connect

    Cuesta, Herman J. Mosquera; Lambiase, G. E-mail: lambiase@sa.infn.it

    2011-03-01

    Recently WMAP and BOOMERanG experiments have set stringent constraints on the polarization angle of photons propagating in an expanding universe: Δα = (−2.4±1.9)°. The polarization of the Cosmic Microwave Background radiation (CMB) is reviewed in the context of nonlinear electrodynamics (NLED). We compute the polarization angle of photons propagating in a cosmological background with planar symmetry. For this purpose, we use the Pagels-Tomboulis (PT) Lagrangian density describing NLED, which has the form L ∼ (X/Λ{sup 4}){sup δ−1} X, where X = ¼F{sub αβ}F{sup αβ}, and δ the parameter featuring the non-Maxwellian character of the PT nonlinear description of the electromagnetic interaction. After looking at the polarization components in the plane orthogonal to the (x)-direction of propagation of the CMB photons, the polarization angle is defined in terms of the eccentricity of the universe, a geometrical property whose evolution on cosmic time (from the last scattering surface to the present) is constrained by the strength of magnetic fields over extragalactic distances.

  3. Nanofriction in Cavity Quantum Electrodynamics.

    PubMed

    Fogarty, T; Cormick, C; Landa, H; Stojanović, Vladimir M; Demler, E; Morigi, Giovanna

    2015-12-01

    The dynamics of cold trapped ions in a high-finesse resonator results from the interplay between the long-range Coulomb repulsion and the cavity-induced interactions. The latter are due to multiple scatterings of laser photons inside the cavity and become relevant when the laser pump is sufficiently strong to overcome photon decay. We study the stationary states of ions coupled with a mode of a standing-wave cavity as a function of the cavity and laser parameters, when the typical length scales of the two self-organizing processes, Coulomb crystallization and photon-mediated interactions, are incommensurate. The dynamics are frustrated and in specific limiting cases can be cast in terms of the Frenkel-Kontorova model, which reproduces features of friction in one dimension. We numerically recover the sliding and pinned phases. For strong cavity nonlinearities, they are in general separated by bistable regions where superlubric and stick-slip dynamics coexist. The cavity, moreover, acts as a thermal reservoir and can cool the chain vibrations to temperatures controlled by the cavity parameters and by the ions' phase. These features are imprinted in the radiation emitted by the cavity, which is readily measurable in state-of-the-art setups of cavity quantum electrodynamics. PMID:26684118

  4. Nanofriction in Cavity Quantum Electrodynamics.

    PubMed

    Fogarty, T; Cormick, C; Landa, H; Stojanović, Vladimir M; Demler, E; Morigi, Giovanna

    2015-12-01

    The dynamics of cold trapped ions in a high-finesse resonator results from the interplay between the long-range Coulomb repulsion and the cavity-induced interactions. The latter are due to multiple scatterings of laser photons inside the cavity and become relevant when the laser pump is sufficiently strong to overcome photon decay. We study the stationary states of ions coupled with a mode of a standing-wave cavity as a function of the cavity and laser parameters, when the typical length scales of the two self-organizing processes, Coulomb crystallization and photon-mediated interactions, are incommensurate. The dynamics are frustrated and in specific limiting cases can be cast in terms of the Frenkel-Kontorova model, which reproduces features of friction in one dimension. We numerically recover the sliding and pinned phases. For strong cavity nonlinearities, they are in general separated by bistable regions where superlubric and stick-slip dynamics coexist. The cavity, moreover, acts as a thermal reservoir and can cool the chain vibrations to temperatures controlled by the cavity parameters and by the ions' phase. These features are imprinted in the radiation emitted by the cavity, which is readily measurable in state-of-the-art setups of cavity quantum electrodynamics.

  5. Nanofriction in Cavity Quantum Electrodynamics

    NASA Astrophysics Data System (ADS)

    Fogarty, T.; Cormick, C.; Landa, H.; Stojanović, Vladimir M.; Demler, E.; Morigi, Giovanna

    2015-12-01

    The dynamics of cold trapped ions in a high-finesse resonator results from the interplay between the long-range Coulomb repulsion and the cavity-induced interactions. The latter are due to multiple scatterings of laser photons inside the cavity and become relevant when the laser pump is sufficiently strong to overcome photon decay. We study the stationary states of ions coupled with a mode of a standing-wave cavity as a function of the cavity and laser parameters, when the typical length scales of the two self-organizing processes, Coulomb crystallization and photon-mediated interactions, are incommensurate. The dynamics are frustrated and in specific limiting cases can be cast in terms of the Frenkel-Kontorova model, which reproduces features of friction in one dimension. We numerically recover the sliding and pinned phases. For strong cavity nonlinearities, they are in general separated by bistable regions where superlubric and stick-slip dynamics coexist. The cavity, moreover, acts as a thermal reservoir and can cool the chain vibrations to temperatures controlled by the cavity parameters and by the ions' phase. These features are imprinted in the radiation emitted by the cavity, which is readily measurable in state-of-the-art setups of cavity quantum electrodynamics.

  6. Ice-Tethered Profiler Contributions to the Arctic Observing Network

    NASA Astrophysics Data System (ADS)

    Toole, J.; Krishfield, R.; Proshutinsky, A.; Timmermans, M.

    2008-12-01

    One of the hoped-for legacies of the International Polar Year is a sustained observational program such as the Arctic Observing Network to document and build understanding of future climate and ecosystem change. In the spirit of the now-operational international Argo float program, investigators from North America, Europe and Japan are collaborating to deploy drifting, ice-based observatory instrument systems on and below floes in the Arctic to sample the polar atmosphere-ice-ocean system and to make the resulting data available to researchers world-wide in real time. One element of these observatories is the WHOI Ice-Tethered Profiler, first deployed in August 2004. The ITP consists of a surface float and electronics package that sits atop an ice floe, a weighted, plastic-jacketed wire-rope tether extending from the surface float through the ice and down to 750-800 m depth, and a profiling vehicle with sensor package that moves up and down the tether. To date, 30 ITP systems (funded by research programs in 5 countries) have been deployed in the Arctic that together have returned more than 10,000 high-vertical-resolution temperature and salinity profiles spanning approximately 7 to 760 m depth over all seasons. Examples of the science being conducted with these data will be presented, along with performance statistics for the ITP instruments and engineering improvements/enhancements that are being implemented. Plans for sustaining the ITP contribution to the Arctic Observing Network will also be reviewed and future international collaborations invited.

  7. Microcinematographic analysis of tethered Leptospira illini.

    PubMed Central

    Charon, N W; Daughtry, G R; McCuskey, R S; Franz, G N

    1984-01-01

    A model of Leptospira motility was recently proposed. One element of the model states that in translating cells the anterior spiral-shaped end gyrates counterclockwise and the posterior hook-shaped end gyrates clockwise. We tested these predictions by analyzing cells tethered to a glass surface. Leptospira illini was incubated with antibody-coated latex beads (Ab-beads). These beads adhered to the cells, and subsequently some cells became attached to either the slide or the cover glass via the Ab-beads. As previously reported, these cells rapidly moved back and forth across the surface of the beads. In addition, a general trend was observed: cells tethered to the cover glass rotated clockwise around the Ab-bead; cells tethered to the slide rotated counterclockwise around the Ab-bead. A computer-aided microcinematographic analysis of tethered cells indicated that the direction of rotation of cells around the Ab-bead was a function of both the surface of attachment and the shape of the cell ends. The results can best be explained by assuming that the gyrating ends interact with the glass surface to cause rotation around the Ab-beads. The analysis obtained indicates that the hook- and spiral-shaped ends rotate in the directions predicted by the model. In addition, the tethered cell assay permitted detection of rapid, coordinated reversals of the cell ends, e.g., cells rapidly switched from a hook-spiral configuration to a spiral-hook configuration. These results suggest the existance of a mechanism which coordinates the shape of the cell ends of L. illini. Images PMID:6501226

  8. Tangling of Tethered Swimmers: Interactions between Two Nematodes

    NASA Astrophysics Data System (ADS)

    Backholm, Matilda; Schulman, Rafael D.; Ryu, William S.; Dalnoki-Veress, Kari

    2014-09-01

    The tangling of two tethered microswimming worms serving as the ends of "active strings" is investigated experimentally and modeled analytically. C. elegans nematodes of similar size are caught by their tails using micropipettes and left to swim and interact at different separations over long times. The worms are found to tangle in a reproducible and statistically predictable manner, which is modeled based on the relative motion of the worm heads. Our results provide insight into the intricate tangling interactions present in active biological systems.

  9. Technology update: Tethered aerostat structural design and material developments

    NASA Technical Reports Server (NTRS)

    Witherow, R. G.

    1975-01-01

    Requirements exist for an extremely stable, high performance, all-weather tethered aerostat system. This requirement has been satisfied by a 250,000 cubic foot captive buoyant vehicle as demonstrated by over a year of successful field operations. This achievement required significant advancements in several technology areas including composite materials design, aerostatics and aerodynamics, structural design, electro-mechanical design, vehicle fabrication and mooring operations. This paper specifically addresses the materials and structural design aspects of pressurized buoyant vehicles as related to the general class of Lighter Than Air vehicles.

  10. Phase 3 study of selected tether applications in space. Volume 2: Study results

    NASA Technical Reports Server (NTRS)

    1986-01-01

    Engineering designs were developed relative to a tethered launch assist from the Shuttle for payloads up to 10,000 kg mass and the tethering of a 15,000 kg science platform from the space station. These designs are used for a cost benefit analysis which assesses the feasibility of using such systems as a practical alternative to what would otherwise be accomplished by conventional means. The term conventional as related to both these applications is intended to apply to the use of some form(s) of chemical propulsion system.

  11. Tether-Based Investigation of the Ionosphere and Lower Thermosphere Concept Definition Study Report

    NASA Technical Reports Server (NTRS)

    Johnson, L. (Editor); Herrmann, M. (Editor)

    1997-01-01

    Understanding the plasma and atmosphere around the Earth in the lower altitude regions of the mesosphere, lower thermosphere, and ionosphere is important in the global electric system. An upper atmosphere tether has been proposed to NASA that would collect much-needed data to further our knowledge of the regions. The mission is proposed as a shuttle experiment that would lower a tethered probe into certain regions of Earth's atmosphere, collecting data over a 6-day period. This report is a summary of the results of a concept definition study to design engineering system that will achieve the scientific objectives of this mission.

  12. Resolution of a paradox in classical electrodynamics

    SciTech Connect

    Pinto, Fabrizio

    2006-05-15

    It is an early result of electrostatics in curved space that the gravitational mass of a charge distribution changes by an amount equal to U{sub es}/c{sup 2}, where U{sub es} is the internal electrostatic potential energy and c is the speed of light, if the system is supported at rest by external forces. This fact, independently rediscovered in recent years in the case of a simple dipole, confirms a very reasonable expectation grounded in the mass-energy equivalency equation. However, it is an unsolved paradox of classical electrodynamics that the renormalized mass of an accelerated dipole calculated from the self-forces due to the distortion of the Coulomb field differs in general from that expected from the energy correction, U{sub es}/c{sup 2}, unless the acceleration is transversal to the orientation of the dipole. Here we show that this apparent paradox disappears for any dipole orientation if the self-force is evaluated by means of Whittaker's exact solution for the field of the single charge in a homogeneous gravitational field described in the Rindler metric. The discussion is supported by computer algebra results, diagrams of the electric fields distorted by gravitation, and a brief analysis of the prospects for realistic experimentation. The gravitational correction to dipole-dipole interactions is also discussed.

  13. PT-symmetric quantum electrodynamics and unitarity.

    PubMed

    Milton, Kimball A; Abalo, E K; Parashar, Prachi; Pourtolami, Nima; Wagner, J

    2013-04-28

    More than 15 years ago, a new approach to quantum mechanics was suggested, in which Hermiticity of the Hamiltonian was to be replaced by invariance under a discrete symmetry, the product of parity and time-reversal symmetry, PT. It was shown that, if PT is unbroken, energies were, in fact, positive, and unitarity was satisfied. Since quantum mechanics is quantum field theory in one dimension--time--it was natural to extend this idea to higher-dimensional field theory, and in fact an apparently viable version of PT-invariant quantum electrodynamics (QED) was proposed. However, it has proved difficult to establish that the unitarity of the scattering matrix, for example, the Källén spectral representation for the photon propagator, can be maintained in this theory. This has led to questions of whether, in fact, even quantum mechanical systems are consistent with probability conservation when Green's functions are examined, since the latter have to possess physical requirements of analyticity. The status of PT QED will be reviewed in this paper, as well as the general issue of unitarity.

  14. Study of certain launching techniques using long orbiting tethers

    NASA Technical Reports Server (NTRS)

    Colombo, G.; Arnold, D. A.

    1981-01-01

    A study of the basic equations governing orbital transfers using long orbiting tethers is presented. A very simple approximation to the general transfer equation is derived for the case of short tethers and low eccentricity orbits. Numerical examples are calculated for the case of injection into a circular orbit from a platform in eccentric orbit and injection into eccentric orbit from a platform in circular orbit. For the case of long tethers, a method is derived for reducing tether mass and increasing payload mass by tapering the tether to maintain constant stress per unit of tether cross section. Formulas are presented for calculating the equilibrium orbital parameters taking into account the mass of the platform, tether, and payload.

  15. Interference of the surface of the solid on the performance of tethered molecular catalysts.

    PubMed

    Hong, Junghyun; Zaera, Francisco

    2012-08-01

    The catalytic performance of cinchonidine in the promotion of thiol additions to conjugated ketones was used as a probe to assess the tethering of molecular functionality onto solid surfaces using well-known "click" chemistry involving easy-to-react linkers. It has been assumed in many applications that the tethered molecules retain their chemical properties and dominate the chemistry of the resulting solid systems, but it is shown here that this is not always the case. Indeed, a loss of enantioselectivity was observed upon tethering, which could be accounted for by a combination of at least three effects: (1) the nonselective catalytic activity of the surface of the solid itself; (2) the activity of the OH species generated by hydrolysis of some of the Si-alkoxy groups in the trialkoxy moieties used to bind many linkers to oxide surfaces; and (3) the bonding of the molecule to be tethered directly to the surface. Several ideas were also tested to minimize these problems, including the silylation of the active OH groups within the surface of the oxide support, the selection of solvents to optimize silane polymerization and minimize their breaking up via hydrolysis or alcoholysis reactions, and the linking at defined positions in the molecule to be tethered in order to minimize its ability to interact with the surface.

  16. Renormalizable Electrodynamics of Scalar and Vector Mesons. Part II

    DOE R&D Accomplishments Database

    Salam, Abdus; Delbourgo, Robert

    1964-01-01

    The "gauge" technique" for solving theories introduced in an earlier paper is applied to scalar and vector electrodynamics. It is shown that for scalar electrodynamics, there is no {lambda}φ*2φ2 infinity in the theory, while with conventional subtractions vector electrodynamics is completely finite. The essential ideas of the gauge technique are explained in section 3, and a preliminary set of rules for finite computation in vector electrodynamics is set out in Eqs. (7.28) - (7.34).

  17. Electrodynamics of the middle atmosphere: Superpressure balloon program

    NASA Technical Reports Server (NTRS)

    Holzworth, Robert H.

    1987-01-01

    In this experiment a comprehensive set of electrical parameters were measured during eight long duration flights in the southern hemisphere stratosphere. These flight resulted in the largest data set ever collected from the stratosphere. The stratosphere has never been electrodynamically sampled in the systematic manner before. New discoveries include short term variability in the planetary scale electric current system, the unexpected observation of stratospheric conductivity variations over thunderstorms and the observation of direct stratospheric conductivity variations following a relatively small solar flare. Major statistical studies were conducted of the large scale current systems, the stratospheric conductivity and the neutral gravity waves (from pressure and temperature data) using the entire data set.

  18. ELECTRODYNAMICS à la HOŘAVA

    NASA Astrophysics Data System (ADS)

    Romero, Juan M.; Santiago, José A.; González-Gaxiola, O.; Zamora, Adolfo

    We study an electrodynamics consistent with anisotropic transformations of spacetime with an arbitrary dynamic exponent z. The equations of motion and conserved quantities are explicitly obtained. We show that the propagator of this theory can be regarded as a quantum correction to the usual propagator. Moreover, we obtain that both the momentum and angular momentum are not modified, but their conservation laws do change. We also show that in this theory the speed of light and the electric charge are modified with z. The magnetic monopole in this electrodynamics and its duality transformations are also investigated. For that we found that there exists a dual electrodynamics, with higher derivatives in the electric field, invariant under the same anisotropic transformations.

  19. Computer program for the load and trajectory analysis of two DOF bodies connected by an elastic tether: Users manual

    NASA Technical Reports Server (NTRS)

    Doyle, G. R., Jr.; Burbick, J. W.

    1973-01-01

    The derivation of the differential equations of motion of a 3 Degrees of Freedom body joined to a 3 Degrees of Freedom body by an elastic tether. The tether is represented by a spring and dashpot in parallel. A computer program which integrates the equations of motion is also described. Although the derivation of the equations of motions are for a general system, the computer program is written for defining loads in large boosters recovered by parachutes.

  20. Drop Tower tests in preparation of a Tethered Electromagnetic Docking space demonstration

    NASA Astrophysics Data System (ADS)

    Olivieri, Lorenzo; Francesconi, Alessandro; Antonello, Andrea; Bettiol, Laura; Branz, Francesco; Duzzi, Matteo; Mantellato, Riccardo; Sansone, Francesco; Savioli, Livia

    2016-07-01

    A group of students of the University of Padova is recently developing some technologies to implement a Tethered Electromagnetic Docking (TED) experiment, a novel system for close rendezvous and mating manoeuvres between two spacecraft, consisting in a small tethered probe ejected by the chaser and magnetically guided by a receiving electromagnet mounted on the target. Because of the generated magnetic field, automatic self-alignment and mating are possible; then, as the tether is rewinded, the chaser is able to dock with the target. This concept allows to simplify standard docking procedures, thanks to the reduction of proximity navigation and guidance requirements, as well as consequent fuel reduction. Other interesting applications are expected, from active debris removal to space tugging; in particular, the utilization of the tethered connection for detumbling operations is considered. The realization of a space demonstrator requires a preliminary verification of the critical technologies employed in TED, in particular the magnetic guidance and the probe deploy and retrieve; in the framework of ESA "Drop your Thesis!" 2014 and 2016 campaigns the experiments FELDs (Flexible Electromagnetic Leash Docking system) and STAR (System for Tether Automatic Retrieval) have been focused on the test of such critical elements in the relevant microgravity environment of ZARM Drop Tower in Bremen. In particular, FELDs consisted in a simplified model of TED with a magnetic target interface, a passive tethered probe and its launch system: the experiment allowed to assess the passive self-alignment of the probe with respect to the target and to study the effect of friction between the tether and the release system. Similarly, STAR is investigating the tether actively controlled deployment and retrieval, with the experiment campaign planned on November 2016. In addition, another microgravity experiment is in preparation for the investigation of active magnetic navigation: PACMAN

  1. Stability analysis and trend study of a balloon tethered in a wind, with experimental comparisons

    NASA Technical Reports Server (NTRS)

    Redd, L. T.; Bland, S. R.; Bennett, R. M.

    1973-01-01

    A stability analysis and trend study for a balloon tethered in a steady wind are presented. The linearized, stability-derivative type analysis includes balloon aerodynamics, buoyancy, mass (including apparent mass), and static forces resulting from the tether cable. The analysis has been applied to a balloon 7.64 m in length, and the results are compared with those from tow tests of this balloon. This comparison shows that the analysis gives reasonable predictions for the damping, frequencies, modes of motion, and stability boundaries exhibited by the balloon. A trend study for the 7.64-m balloon was made to illustrate how the stability boundaries are affected by changes in individual stability parameters. The trends indicated in this study may also be applicable to many other tethered-balloon systems.

  2. Construction and structural analysis of tethered lipid bilayer containing photosynthetic antenna proteins for functional analysis.

    PubMed

    Sumino, Ayumi; Dewa, Takehisa; Takeuchi, Toshikazu; Sugiura, Ryuta; Sasaki, Nobuaki; Misawa, Nobuo; Tero, Ryugo; Urisu, Tsuneo; Gardiner, Alastair T; Cogdell, Richard J; Hashimoto, Hideki; Nango, Mamoru

    2011-07-11

    The construction and structural analysis of a tethered planar lipid bilayer containing bacterial photosynthetic membrane proteins, light-harvesting complex 2 (LH2), and light-harvesting core complex (LH1-RC) is described and establishes this system as an experimental platform for their functional analysis. The planar lipid bilayer containing LH2 and/or LH1-RC complexes was successfully formed on an avidin-immobilized coverglass via an avidin-biotin linkage. Atomic force microscopy (AFM) showed that a smooth continuous membrane was formed there. Lateral diffusion of these membrane proteins, observed by a fluorescence recovery after photobleaching (FRAP), is discussed in terms of the membrane architecture. Energy transfer from LH2 to LH1-RC within the tethered membrane was observed by steady-state fluorescence spectroscopy, indicating that the tethered membrane can mimic the natural situation.

  3. Quantum gravitational contributions to quantum electrodynamics.

    PubMed

    Toms, David J

    2010-11-01

    Quantum electrodynamics describes the interactions of electrons and photons. Electric charge (the gauge coupling constant) is energy dependent, and there is a previous claim that charge is affected by gravity (described by general relativity) with the implication that the charge is reduced at high energies. However, that claim has been very controversial and the matter has not been settled. Here I report an analysis (free from the earlier controversies) demonstrating that quantum gravity corrections to quantum electrodynamics have a quadratic energy dependence that result in the electric charge vanishing at high energies, a result known as asymptotic freedom.

  4. Tethered and Polymer Supported Bilayer Lipid Membranes: Structure and Function

    PubMed Central

    Andersson, Jakob; Köper, Ingo

    2016-01-01

    Solid supported bilayer lipid membranes are model systems to mimic natural cell membranes in order to understand structural and functional properties of such systems. The use of a model system allows for the use of a wide variety of analytical tools including atomic force microscopy, impedance spectroscopy, neutron reflectometry, and surface plasmon resonance spectroscopy. Among the large number of different types of model membranes polymer-supported and tethered lipid bilayers have been shown to be versatile and useful systems. Both systems consist of a lipid bilayer, which is de-coupled from an underlying support by a spacer cushion. Both systems will be reviewed, with an emphasis on the effect that the spacer moiety has on the bilayer properties. PMID:27249006

  5. Tethered and Polymer Supported Bilayer Lipid Membranes: Structure and Function.

    PubMed

    Andersson, Jakob; Köper, Ingo

    2016-01-01

    Solid supported bilayer lipid membranes are model systems to mimic natural cell membranes in order to understand structural and functional properties of such systems. The use of a model system allows for the use of a wide variety of analytical tools including atomic force microscopy, impedance spectroscopy, neutron reflectometry, and surface plasmon resonance spectroscopy. Among the large number of different types of model membranes polymer-supported and tethered lipid bilayers have been shown to be versatile and useful systems. Both systems consist of a lipid bilayer, which is de-coupled from an underlying support by a spacer cushion. Both systems will be reviewed, with an emphasis on the effect that the spacer moiety has on the bilayer properties. PMID:27249006

  6. The Study of the Tether Motion with Time-Varying Length Using the Absolute Nodal Coordinate Formulation with Multiple Nonlinear Time Scales

    NASA Astrophysics Data System (ADS)

    Kawaguti, Keisuke; Terumichi, Yoshiaki; Takehara, Shoichiro; Kaczmarczyk, Stefan; Sogabe, Kiyoshi

    In this study, the modeling and formulation for tether motion with time-varying length, large rotation, large displacement and large deformation are proposed. A tether or cable is an important element in lift systems, construction machines for transportation and often is used with a time-varying length. In some cases, these systems are large and the tether has a long length, large deformation and large displacement. The dynamic behavior of a tether in extension and retraction using the proposed method is discussed in this paper. In the passage through resonance, significant tether motions with large rotation and large deformation result. In the analysis of this phenomenon, the transient fluctuations of the motion amplitudes are examined and compared with the corresponding steady state motions. The accuracy and the cost of the calculations are also verified by comparison with the experimental results.

  7. Precision tethered satellite attitude control. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Kline-Schoder, Robert J.

    1990-01-01

    Tethered spacecraft possess unique dynamic characteristics which make them advantageous for certain classes of experiments. One use for which tethers are particularly well suited is to provide an isolated platform for spaceborne observatories. The advantages of tethering a pointing platform 1 or 2 km from a space shuttle or space station are that, compared to placing the observatory on the parent spacecraft, vibrational disturbances are attenuated and contamination is eliminated. In practice, all satellites have some requirement on the attitude control of the spacecraft, and tethered satellites are no exception. It has previously been shown that conventional means of performing attitude control for tethered satellites are insufficient for any mission with pointing requirements more stringent than about 1 deg. This is due mainly to the relatively large force applied by the tether to the spacecraft. A particularly effective method of implementing attitude control for tethered satellites is to use this tether tension force to generate control torques by moving the tether attach point relative to the subsatellite center of mass. A demonstration of this attitude control technique on an astrophysical pointing platform has been proposed for a space shuttle flight test project and is referred to as the Kinetic Isolation Tether Experiment (KITE).

  8. Cholesterol-based tethers and markers for model membranes investigation.

    PubMed

    Eicher-Lorka, O; Charkova, T; Matijoška, A; Kuodis, Z; Urbelis, G; Penkauskas, T; Mickevičius, M; Bulovas, A; Valinčius, G

    2016-02-01

    A series of new bifunctional cholesterol compounds for tethered bilayer membrane (tBLM) systems were synthesized and tested. The compounds containing cyclic disulfide group may be used as molecular anchors for phospholipid bilayers. Anchoring occurs through the insertion of the cholesterol moiety into the hydrophobic slab of the phospholipid layer, while the surface density of anchor molecules may be adjusted using disulfides terminated spacers. Five ethylene oxide segments between the disulfide group and the cholesteryl provide hydration of the layer separating solid support and model membrane. Another group of cholesterol derivatives described in this work contains either fluorescence probe or electroactive functional groups. We demonstrated the practical utility of these compounds for visualization of cholesterol extraction from and loading to tBLMs. We demonstrated that electroactive group containing cholesterol derivatives can be reconstituted either into vesicles or tBLMs. In both cases an electrochemical signal can be generated on electrodes from these probes. In general, the newly synthesized compound may be utilized in a variety of applications involving tethered bilayer systems and vesicles.

  9. Capabilities of electrodynamic shakers when used for mechanical shock testing

    NASA Technical Reports Server (NTRS)

    Keegan, W. B.

    1973-01-01

    The results of a research task to investigate the capabilities of electrodynamic vibrators (shakers) to perform mechanical shock tests are presented. The simulation method employed was that of developing a transient whose shock response spectrum matched the desired shock response spectrum. Areas investigated included the maximum amplitude capabilities of the shaker systems, the ability to control the shape of the resultant shock response spectrum, the response levels induced at frequencies outside the controlled bandwidth, and the nonlinearities in structural response induced by a change in test level.

  10. Space Environmental Testing of the Electrodynamic Dust Shield Technology

    NASA Technical Reports Server (NTRS)

    Calle, Carlos I.; Mackey, P. J.; Hogue, M. D.; Johansen, M .R.; Yim, H.; Delaune, P. B.; Clements, J. S.

    2013-01-01

    NASA's exploration missions to Mars and the moon may be jeopardized by dust that will adhere to surfaces of (a) Optical systems, viewports and solar panels, (b) Thermal radiators, (c) Instrumentation, and (d) Spacesuits. We have developed an active dust mitigation technology, the Electrodynamic Dust Shield, a multilayer coating that can remove dust and also prevents its accumulation Extensive testing in simulated laboratory environments and on a reduced gravity flight shows that high dust removal performance can be achieved Long duration exposure to the space environment as part of the MISSE-X payload will validate the technology for lunar missions.

  11. Hybrid circuit cavity quantum electrodynamics with a micromechanical resonator.

    PubMed

    Pirkkalainen, J-M; Cho, S U; Li, Jian; Paraoanu, G S; Hakonen, P J; Sillanpää, M A

    2013-02-14

    Hybrid quantum systems with inherently distinct degrees of freedom have a key role in many physical phenomena. Well-known examples include cavity quantum electrodynamics, trapped ions, and electrons and phonons in the solid state. In those systems, strong coupling makes the constituents lose their individual character and form dressed states, which represent a collective form of dynamics. As well as having fundamental importance, hybrid systems also have practical applications, notably in the emerging field of quantum information control. A promising approach is to combine long-lived atomic states with the accessible electrical degrees of freedom in superconducting cavities and quantum bits (qubits). Here we integrate circuit cavity quantum electrodynamics with phonons. Apart from coupling to a microwave cavity, our superconducting transmon qubit, consisting of tunnel junctions and a capacitor, interacts with a phonon mode in a micromechanical resonator, and thus acts like an atom coupled to two different cavities. We measure the phonon Stark shift, as well as the splitting of the qubit spectral line into motional sidebands, which feature transitions between the dressed electromechanical states. In the time domain, we observe coherent conversion of qubit excitation to phonons as sideband Rabi oscillations. This is a model system with potential for a quantum interface, which may allow for storage of quantum information in long-lived phonon states, coupling to optical photons or for investigations of strongly coupled quantum systems near the classical limit.

  12. Lamb Shift in Nonrelativistic Quantum Electrodynamics.

    ERIC Educational Resources Information Center

    Grotch, Howard

    1981-01-01

    The bound electron self-energy or Lamb shift is calculated in nonrelativistic quantum electrodynamics. Retardation is retained and also an interaction previously dropped in other nonrelativistic approaches is kept. Results are finite without introducing a cutoff and lead to a Lamb shift in hydrogen of 1030.9 MHz. (Author/JN)

  13. Electrodynamics in One Dimension: Radiation and Reflection

    ERIC Educational Resources Information Center

    Asti, G.; Coisson, R.

    2011-01-01

    Problems involving polarized plane waves and currents on sheets perpendicular to the wavevector involve only one component of the fields, so it is possible to discuss electrodynamics in one dimension. Taking for simplicity linearly polarized sinusoidal waves, we can derive the field emitted by currents (analogous to dipole radiation in three…

  14. Linear Response Laws and Causality in Electrodynamics

    ERIC Educational Resources Information Center

    Yuffa, Alex J.; Scales, John A.

    2012-01-01

    Linear response laws and causality (the effect cannot precede the cause) are of fundamental importance in physics. In the context of classical electrodynamics, students often have a difficult time grasping these concepts because the physics is obscured by the intermingling of the time and frequency domains. In this paper, we analyse the linear…

  15. Testing Born-Infeld electrodynamics in waveguides.

    PubMed

    Ferraro, Rafael

    2007-12-01

    Waveguides can be employed to test nonlinear effects in electrodynamics. We solve Born-Infeld equations for TE waves in a rectangular waveguide. We show that the energy velocity acquires a dependence on the amplitude, and harmonic components appear as a consequence of the nonlinear behavior.

  16. Nonlinear quantum electrodynamics in vacuum and plasmas

    SciTech Connect

    Brodin, Gert; Lundin, Joakim; Marklund, Mattias

    2010-12-14

    We consider high field physics due to quantum electrodynamics, in particular those that can be studied in the next generation of laser facilities. Effective field theories based on the Euler-Heisenberg Lagrangian are briefly reviewed, and examples involving plasma- and vacuum physics are given.

  17. Quantum Hall effect in quantum electrodynamics

    SciTech Connect

    Penin, Alexander A.

    2009-03-15

    We consider the quantum Hall effect in quantum electrodynamics and find a deviation from the quantum-mechanical prediction for the Hall conductivity due to radiative antiscreening of electric charge in an external magnetic field. A weak dependence of the universal von Klitzing constant on the magnetic field strength, which can possibly be observed in a dedicated experiment, is predicted.

  18. Students' Difficulties with Vector Calculus in Electrodynamics

    ERIC Educational Resources Information Center

    Bollen, Laurens; van Kampen, Paul; De Cock, Mieke

    2015-01-01

    Understanding Maxwell's equations in differential form is of great importance when studying the electrodynamic phenomena discussed in advanced electromagnetism courses. It is therefore necessary that students master the use of vector calculus in physical situations. In this light we investigated the difficulties second year students at KU Leuven…

  19. Strong field electrodynamics of a thin foil

    SciTech Connect

    Bulanov, Sergei V.; Esirkepov, Timur Zh.; Kando, Masaki; Bulanov, Stepan S.; Rykovanov, Sergey G.; Pegoraro, Francesco

    2013-12-15

    Exact solutions describing the nonlinear electrodynamics of a thin double layer foil are presented. These solutions correspond to a broad range of problems of interest for the interaction of high intensity laser pulses with overdense plasmas, such as frequency upshifting, high order harmonic generation, and high energy ion acceleration.

  20. Dynamics and Power Generation Potential from a Tethered Kite Moving in a Horizontal Flightpath

    NASA Astrophysics Data System (ADS)

    Gavi, Glenn Romo

    Tethered-wing power systems are a viable possibility for collecting energy from stronger, more consistent winds found in the upper regions of the atmosphere where conventional wind turbines are incapable of reaching. To date, all of the tethered-wing systems fly with the tether oriented down-wind of the ground attachment point. Examined here are the dynamics and performance of a novel system where the tether is oriented both upwind and downwind of the ground attachment point during normal operation of the device. Certain prototypes built by Makani and Ampyx Power are considered to have motions analogous to the motions of the blade tips on conventional horizontal-axis wind turbines. If true, this system has motions that are analogous to conventional vertical-axis wind turbines. The system has a ground-based generator which is mechanical coupled to the aircraft and energy is generated on the reel-out phase of each cycle while a smaller amount of energy is consumed during the reel-in phase of each cycle. A simple model was developed which captures the dominant dynamics of this system and shows, via simulation, that the proposed system is viable and capable of stable and unstable periodic motions with a simulated closed-loop tether tension controller or a simple open loop reel-rate controller. In addition, it is capable of motions which produce net positive power. The small system examined, where parameter optimization was not performed, predicts an average cycle power of more than 500 watts in a 10 m/s wind.

  1. Single photon delayed feedback: a way to stabilize intrinsic quantum cavity electrodynamics.

    PubMed

    Carmele, Alexander; Kabuss, Julia; Schulze, Franz; Reitzenstein, Stephan; Knorr, Andreas

    2013-01-01

    We propose a scheme to control cavity quantum electrodynamics in the single photon limit by delayed feedback. In our approach a single emitter-cavity system, operating in the weak coupling limit, can be driven into the strong coupling-type regime by an external mirror: The external loop produces Rabi oscillations directly connected to the electron-photon coupling strength. As an expansion of typical cavity quantum electrodynamics, we treat the quantum correlation of external and internal light modes dynamically and demonstrate a possible way to implement a fully quantum mechanical time-delayed feedback. Our theoretical approach proposes a way to experimentally feedback control quantum correlations in the single photon limit.

  2. Coat/Tether Interactions-Exception or Rule?

    PubMed

    Schroeter, Saskia; Beckmann, Sabrina; Schmitt, Hans Dieter

    2016-01-01

    Coat complexes are important for cargo selection and vesicle formation. Recent evidence suggests that they may also be involved in vesicle targeting. Tethering factors, which form an initial bridge between vesicles and the target membrane, may bind to coat complexes. In this review, we ask whether these coat/tether interactions share some common mechanisms, or whether they are special adaptations to the needs of very specific transport steps. We compare recent findings in two multisubunit tethering complexes, the Dsl1 complex and the HOPS complex, and put them into context with the TRAPP I complex as a prominent example for coat/tether interactions. We explore where coat/tether interactions are found, compare their function and structure, and comment on a possible evolution from a common ancestor of coats and tethers. PMID:27243008

  3. Coat/Tether Interactions—Exception or Rule?

    PubMed Central

    Schröter, Saskia; Beckmann, Sabrina; Schmitt, Hans Dieter

    2016-01-01

    Coat complexes are important for cargo selection and vesicle formation. Recent evidence suggests that they may also be involved in vesicle targeting. Tethering factors, which form an initial bridge between vesicles and the target membrane, may bind to coat complexes. In this review, we ask whether these coat/tether interactions share some common mechanisms, or whether they are special adaptations to the needs of very specific transport steps. We compare recent findings in two multisubunit tethering complexes, the Dsl1 complex and the HOPS complex, and put them into context with the TRAPP I complex as a prominent example for coat/tether interactions. We explore where coat/tether interactions are found, compare their function and structure, and comment on a possible evolution from a common ancestor of coats and tethers. PMID:27243008

  4. Rigorous approaches to tether dynamics in deployment and retrieval

    NASA Technical Reports Server (NTRS)

    Antona, Ettore

    1987-01-01

    Dynamics of tethers in a linearized analysis can be considered as the superposition of propagating waves. This approach permits a new way for the analysis of tether behavior during deployment and retrieval, where a tether is composed by a part at rest and a part subjected to propagation phenomena, with the separating section depending on time. The dependence on time of the separating section requires the analysis of the reflection of the waves travelling toward the part at rest. Such a reflection generates a reflected wave, whose characteristics are determined. The propagation phenomena of major interest in a tether are transverse waves and longitudinal waves, all mathematically modelled by the vibrating chord equations, if the tension is considered constant along the tether. An interesting problem also considered is concerned with the dependence of the tether tension from the longitudinal position, due to microgravity, and the influence of this dependence on the propagation waves.

  5. Isothermal pumping analysis for high-altitude tethered balloons.

    PubMed

    Kuo, Kirsty A; Hunt, Hugh E M

    2015-06-01

    High-altitude tethered balloons have potential applications in communications, surveillance, meteorological observations and climate engineering. To maintain balloon buoyancy, power fuel cells and perturb atmospheric conditions, fluids could be pumped from ground level to altitude using the tether as a hose. This paper examines the pumping requirements of such a delivery system. Cases considered include delivery of hydrogen, sulfur dioxide (SO2) and powders as fluid-based slurries. Isothermal analysis is used to determine the variation of pressures and velocities along the pipe length. Results show that transport of small quantities of hydrogen to power fuel cells and maintain balloon buoyancy can be achieved at pressures and temperatures that are tolerable in terms of both the pipe strength and the current state of pumping technologies. To avoid solidification, transport of SO2 would require elevated temperatures that cannot be tolerated by the strength fibres in the pipe. While the use of particle-based slurries rather than SO2 for climate engineering can reduce the pipe size significantly, the pumping pressures are close to the maximum bursting pressure of the pipe. PMID:26543573

  6. Behavior and dynamics of the tethered bacterium Thiovulum majus

    NASA Astrophysics Data System (ADS)

    Petroff, Alexander; Libchaber, Albert

    2014-03-01

    The organization of microorganisms into communities plays a vital role in determining how nutrients flow through an ecosystem. Here we use a combination of experimental observations and mathematical analysis to investigate a simple example of community formation and dynamics. In their natural environment, Thiovulum majus cells attach to surfaces using a tether. As a tethered cell beats its flagella, it creates a flow that pulls nutrients to the cell. As cells form a dense community, fluctuations in cell density drive large-scale convective flows that pull nutrients through the water. We show how the behavior of cells responding to the flow of nutrients through the community gives rise to soliton-like collective modes that efficiently stir the environment. Additionally, we present new techniques for visualizing the flow of nutrients through these communities and the resulting collective phenomena. Because these dynamics arise from hydrodynamic coupling between cells and their environment, this system can be understood using classical techniques from fluid mechanics. In this way, T. majus communities provide a tractable example of the general behavior of community formation in response to nutrient flow.

  7. Isothermal pumping analysis for high-altitude tethered balloons

    PubMed Central

    Kuo, Kirsty A.; Hunt, Hugh E. M.

    2015-01-01

    High-altitude tethered balloons have potential applications in communications, surveillance, meteorological observations and climate engineering. To maintain balloon buoyancy, power fuel cells and perturb atmospheric conditions, fluids could be pumped from ground level to altitude using the tether as a hose. This paper examines the pumping requirements of such a delivery system. Cases considered include delivery of hydrogen, sulfur dioxide (SO2) and powders as fluid-based slurries. Isothermal analysis is used to determine the variation of pressures and velocities along the pipe length. Results show that transport of small quantities of hydrogen to power fuel cells and maintain balloon buoyancy can be achieved at pressures and temperatures that are tolerable in terms of both the pipe strength and the current state of pumping technologies. To avoid solidification, transport of SO2 would require elevated temperatures that cannot be tolerated by the strength fibres in the pipe. While the use of particle-based slurries rather than SO2 for climate engineering can reduce the pipe size significantly, the pumping pressures are close to the maximum bursting pressure of the pipe. PMID:26543573

  8. Cardiorespiratory adjustments to tethered-swimming in the horse.

    PubMed

    Thomas, D P; Fregin, G F; Gerber, N H; Ailes, N B

    1980-05-01

    The cardiorespiratory and metabolic responses to various levels of tethered-swimming were evaluated in 5 sedentary horses. Cardiac output (Q) and heart rate (HR) correlated highly (r = 0.89 and 0.94 respectively) with work effort (WE) expressed as kg pulled . kg body wt-1 . 10-2. While swimming, stroke volume (SV) was reduced at the lowest workloads, but increased with increasing WE so that at the highest workloads it had returned to the on-land standing SV. Pressures in the pulmonic as well as on both sides of the systemic circulation were considerably elevated by this form of exercise, although only mean carotid artery pressure (CAP) correlated highly (r = 0.83) with WE. During tethered-swimming plasma lactic acid (LA) rose exponentially from 1 to 10 mmol . 1-1 with increasing HR over the range 150-200 beats . min-1. Oxygen uptake (VO2) increased linearly (r = 0.95) from 25-112 ml . kg-1. min-1 over the We range of 3.0-7.8 kg pulled . kg body wt-1. 10-2. The aerobic capacity of the equine species would appear to be twice that of man. The greater increase in VO2 in the exercising horse cannot be explained solely on the basis of increases in Q. Therefore alterations in hematocrit, hemoglobin and oxygen extraction appear to play a more important role in the horse during exercise than they do in man.

  9. Tethers as Debris: Simulating Impacts of Tether Fragments on Shuttle Tiles

    NASA Technical Reports Server (NTRS)

    Evans, Steven W.

    2004-01-01

    The SPHC hydrodynamic code was used to simulate impacts of Kevlar and aluminum projectiles on a model of the LI-900 type insulating tiles used on Space Shuffle Orbiters The intent was to examine likely damage that such tiles might experience if impacted by orbital debris consisting of tether fragments. Projectile speeds ranged from 300 meters per second to 10 kilometers per second. Damage is characterized by penetration depth, tile surface-hole diameter, tile body-cavity diameter, coating fracture diameter, tether and cavity wall material phases, and deformation of the aluminum backwall.

  10. Electrodynamic Balance for Studies of Cosmic Dust Particles

    NASA Technical Reports Server (NTRS)

    Spann, J. F.; Abbas, M. M.; Venturini, C. C.; Comfort, R. H.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    Knowledge of the formation and distribution of interstellar, interplanetary, and planetary dust grains, and their physical, chemical and optical characteristics provide valuable information about many issues dealing with the origin and formation of the solar system bodies, interplanetary and interstellar environments as well as various industrial processes. Understanding the microphysics of individual grains and their interaction with the surrounding, environment is key to properly model various conditions and interpret existing data. The theory and models of individual dust grains are well developed for environments that vary from dense planetary atmospheres to dusty plasmas to diffuse environments such as interplanetary space. However, experimental investigations of individual dust grains in equilibrium are less common, perhaps due to the difficulty of these experiments. Laboratory measurements of dust grains have primarily measured ensemble properties or transient properties of single grains. A technique developed in the 1950's for ion spectroscopy, generally referred to as a quadrupole trap has recently been employed as an electrodynamic balance to investigate single micron-sized dust grains and for atmospheric aerosol research. A description of the theoretical basis and the experimental setup of the electrodynamic balance being developed in our laboratory are given. This laboratory technique lends itself to many applications that relate to planetary atmospheres, heliospheric environments, pre-stellar and pre-planetary conditions, and industrial settings. We present results from some recent experiments carried out to investigate the equilibrium potential of dust grains exposed to far ultraviolet light or to an electron beam. Some future experiments using an electrodynamic balance to investigate the optical characteristics, and condensation process involving dust grains in various astrophysical environments are discussed.

  11. The stochastic dynamics of tethered microcantilevers in a viscous fluid

    NASA Astrophysics Data System (ADS)

    Robbins, Brian A.; Radiom, Milad; Ducker, William A.; Walz, John Y.; Paul, Mark R.

    2014-10-01

    We explore and quantify the coupled dynamics of a pair of micron scale cantilevers immersed in a viscous fluid that are also directly tethered to one another at their tips by a spring force. The spring force, for example, could represent the molecular stiffness or elasticity of a biomolecule or material tethered between the cantilevers. We use deterministic numerical simulations with the fluctuation-dissipation theorem to compute the stochastic dynamics of the cantilever pair for the conditions of experiment when driven only by Brownian motion. We validate our approach by comparing directly with experimental measurements in the absence of the tether which shows excellent agreement. Using numerical simulations, we quantify the correlated dynamics of the cantilever pair over a range of tether stiffness. Our results quantify the sensitivity of the auto- and cross-correlations of equilibrium fluctuations in cantilever displacement to the stiffness of the tether. We show that the tether affects the magnitude of the correlations which can be used in a measurement to probe the properties of an attached tethering substance. For the configurations of current interest using micron scale cantilevers in water, we show that the magnitude of the fluid coupling between the cantilevers is sufficiently small such that the influence of the tether can be significant. Our results show that the cross-correlation is more sensitive to tether stiffness than the auto-correlation indicating that a two-cantilever measurement has improved sensitivity when compared with a measurement using a single cantilever.

  12. Membrane tether formation from outer hair cells with optical tweezers.

    PubMed Central

    Li, Zhiwei; Anvari, Bahman; Takashima, Masayoshi; Brecht, Peter; Torres, Jorge H; Brownell, William E

    2002-01-01

    Optical tweezers were used to characterize the mechanical properties of the outer hair cell (OHC) plasma membrane by pulling tethers with 4.5-microm polystyrene beads. Tether formation force and tether force were measured in static and dynamic conditions. A greater force was required for tether formations from OHC lateral wall (499 +/- 152 pN) than from OHC basal end (142 +/- 49 pN). The difference in the force required to pull tethers is consistent with an extensive cytoskeletal framework associated with the lateral wall known as the cortical lattice. The apparent plasma membrane stiffness, estimated under the static conditions by measuring tether force at different tether length, was 3.71 pN/microm for OHC lateral wall and 4.57 pN/microm for OHC basal end. The effective membrane viscosity was measured by pulling tethers at different rates while continuously recording the tether force, and estimated in the range of 2.39 to 5.25 pN x s/microm. The viscous force most likely results from the viscous interactions between plasma membrane lipids and the OHC cortical lattice and/or integral membrane proteins. The information these studies provide on the mechanical properties of the OHC lateral wall is important for understanding the mechanism of OHC electromotility. PMID:11867454

  13. The stochastic dynamics of tethered microcantilevers in a viscous fluid

    SciTech Connect

    Robbins, Brian A.; Paul, Mark R.; Radiom, Milad; Ducker, William A.; Walz, John Y.

    2014-10-28

    We explore and quantify the coupled dynamics of a pair of micron scale cantilevers immersed in a viscous fluid that are also directly tethered to one another at their tips by a spring force. The spring force, for example, could represent the molecular stiffness or elasticity of a biomolecule or material tethered between the cantilevers. We use deterministic numerical simulations with the fluctuation-dissipation theorem to compute the stochastic dynamics of the cantilever pair for the conditions of experiment when driven only by Brownian motion. We validate our approach by comparing directly with experimental measurements in the absence of the tether which shows excellent agreement. Using numerical simulations, we quantify the correlated dynamics of the cantilever pair over a range of tether stiffness. Our results quantify the sensitivity of the auto- and cross-correlations of equilibrium fluctuations in cantilever displacement to the stiffness of the tether. We show that the tether affects the magnitude of the correlations which can be used in a measurement to probe the properties of an attached tethering substance. For the configurations of current interest using micron scale cantilevers in water, we show that the magnitude of the fluid coupling between the cantilevers is sufficiently small such that the influence of the tether can be significant. Our results show that the cross-correlation is more sensitive to tether stiffness than the auto-correlation indicating that a two-cantilever measurement has improved sensitivity when compared with a measurement using a single cantilever.

  14. A new tether system for captive raptors

    USGS Publications Warehouse

    Ellis, D.H.

    1995-01-01

    Several types of jesses are used to restrain captive raptors. The Hollywood jess described here has been tested on six species during two decades. Like the Aylmeri jess now in common use in North America, the Hollywood jess consists of a removable rolled button jess and an anklet. Unlike the Aylmeri anklet, however, the Hollywood anklet can be removed and reattached without restraining the bird. This anklet makes the Hollywood jess the safest of all jesses. It can also be used repeatedly on different individuals and allows for the bird to be released in its pen or to the wild without encumbrances.

  15. Open-Loop Thrust Profile Development for Tethered Towing of Large Space Objects

    NASA Astrophysics Data System (ADS)

    Jasper, Lee E. Z.

    Towing objects in space has become an increasingly researched mission concept. Active debris removal, satellite servicing, and asteroid retrieval concepts in many cases rely on a thrusting vehicle to redirect and steer a passive object. Focus is often placed on the method of attachment, considering techniques such as grappling or netting the passive object. However, the actual process of towing, once capture has occurred, has not yet received much attention. This research considers the process of towing in space with the tug and passive object attached by a tether. Tethers are not only an effective way of transmitting forces, but they are utilized on many of the towing concepts considered, especially in orbital debris removal. Because the two end bodies are tethered, there is a potential for collision after any maneuver. To avoid collisions, the maneuver, and therefore thrust profile, must be designed in such a way as to limit separation distance reduction between the end bodies. Open-loop input shaping techniques are developed and employed in order to control the flexible system in both deep space and on-orbit environments. To study the behavior, an active debris removal system is proposed as a case study. This system, called the tethered-tug, considers using the reserve fuel from a recently launched upper stage rocket to rendezvous with, capture, and tow a near-by debris object. The system's performance is considered for five distinct open-loop thrust control profiles including on-off/step, frequency notched, discretized notch, Posicast, and bang-off-bang. Tether property variations are also considered along with off-axis towing, slack tethers, and debris with initial rotation rates. Input shaping is not only necessary but, it can be robust to unknown system properties while nearly zeroing relative motion between the end bodies. When considering on-orbit behavior specifically, the system settles into a tumbling or gravity gradient oscillation formation. This is

  16. Analysis and design of a friction brake for momentum exchange propulsion tethers

    NASA Astrophysics Data System (ADS)

    Lennert, Simone; Cartmell, Matthew P.

    2003-11-01

    The purpose of this paper is to present an engineering assessment of a proposal for a deployment brake for a momentum exchange tether. Tethers have attracted considerable interest amongst the propulsion community for many years for orbit raising, energy conversion, de-orbiting, and injection into interplanetary transfers, and the motivation for the work described in the paper is directly mission-oriented. The YES2 SpaceMail mission has been planned as a low-cost international effort to provide a facility for the return of small samples from the ISS back to Earth, based on an inflatable re-entry capsule and a mechanical tether system. The system will be lofted into orbit as part of a payload on a Foton/Bion rocket launcher. The brake design concept is based on the use of friction between the deploying tether and a short pole onto which several turns are wound, and the paper summarises the modelling work that has been done, and then discusses an experiment in which the premise was tested in the laboratory. The paper concludes with certain practical proposals for implementation.

  17. Analysis and design of a friction brake for momentum exchange propulsion tethers

    NASA Astrophysics Data System (ADS)

    Lennert, Simone; Cartmell, Matthew P.

    2006-10-01

    The purpose of this paper is to present an engineering assessment of a proposal for a deployment brake for a momentum exchange tether. Tethers have attracted considerable interest amongst the propulsion community for many years for orbit raising, energy conversion, de-orbiting, and injection into interplanetary transfers, and the motivation for the work described in the paper is directly mission-oriented. The YES2 SpaceMail mission has been planned as a low-cost international effort to provide a facility for the return of small samples from the ISS back to Earth, based on an inflatable re-entry capsule and a mechanical tether system. The system will be lofted into orbit as part of a payload on a Foton/Bion rocket launcher. The brake design concept is based on the use of friction between the deploying tether and a short pole onto which several turns are wound, and the paper summarises the modelling work that has been done, and then discusses an experiment in which the premise was tested in the laboratory. The paper concludes with certain practical proposals for implementation.

  18. Aerobic and anaerobic performances in tethered swimming.

    PubMed

    Papoti, M; da Silva, A S R; Araujo, G G; Santiago, V; Martins, L E B; Cunha, S A; Gobatto, C A

    2013-08-01

    The purpose of this study was to investigate whether the critical force (CritF) and anaerobic impulse capacity (AIC) - estimated by tethered swimming - reflect the aerobic and anaerobic performance of swimmers. 12 swimmers performed incremental test in tethered swimming to determine lactate anaerobic threshold (AnTLAC), maximal oxygen uptake ( ˙VO2MAX) and force associated with the ˙VO2MAX (i ˙VO2MAX). The swimmers performed 4 exhaustive (tlim) exercise bouts (100, 110, 120 and 130% i ˙VO2MAX) to compute the CritF and AIC (F vs. 1/tlim model); a 30-s all-out tethered swimming bout to determine their anaerobic fitness (ANF); 100, 200, and 400-m time-trials to determine the swimming performance. CritF (57.09±11.77 N) did not differ from AnTLAC (53.96±11.52 N, (P>0.05) but was significantly lower than i ˙VO2MAX (71.02±8.36 N). In addition, CritF presented significant correlation with AnTLAC (r=0.76; P<0.05) and i ˙VO2MAX (r=0.74; P<0.05). On the other hand, AIC (286.19±54.91 N.s) and ANF (116.10±13.66 N) were significantly correlated (r=0.81, p<0.05). In addition, CritF and AIC presented significant correlations with all time-trials. In summary, this study demonstrates that CritF and AIC can be used to evaluate AnTLAC and ANF and to predict 100, 200, and 400-m free swimming.

  19. Molecular Crowding Effects on Microgel-Tethered Oligonucleotide Probes.

    PubMed

    Ma, Youlong; Libera, Matthew

    2016-06-28

    Microgel tethering is a nontraditional method with which to bind oligonucleotide hybridization probes to a solid surface. Microgel-tethering physically positions the probes away from the underlying hard substrate and maintains them in a highly waterlike environment. This paper addresses the question of whether molecular crowding affects the performance of microgel-tethered molecular beacon probes. The density of probe-tethering sites is controlled experimentally using thin-film blends of biotin-terminated [PEG-B] and hydroxyl-terminated [PEG-OH] poly(ethylene glycol) from which microgels are synthesized and patterned by electron beam lithography. Fluorescence measurements indicate that the number of streptavidins, linear DNA probes, hairpin probes, and molecular beacon probes bound to the microgels increases linearly with increasing PEG-B/PEG-OH ratio. For a given tethering-site concentration, more linear probes can bind than structured probes. Crowding effects emerge during the hybridization of microgel-tethered molecular beacons but not during the hybridization of linear probes, as the tethering density increases. Crowding during hybridization is associated with conformational constraints imposed by the close proximity of closed and hybridized structured probes. The signal-to-background ratio (SBR) of hybridized beacons is highest and roughly constant for low tethering densities and decreases at the highest tethering densities. Despite differences between microgel tethering and traditional oligonucleotide surface-immobilization approaches, these results show that crowding defines an optimum tethering density for molecular beacon probes that is less than the maximum possible, which is consistent with previous studies involving various linear and structured oligonucleotide probes. PMID:27253904

  20. Molecular Crowding Effects on Microgel-Tethered Oligonucleotide Probes.

    PubMed

    Ma, Youlong; Libera, Matthew

    2016-06-28

    Microgel tethering is a nontraditional method with which to bind oligonucleotide hybridization probes to a solid surface. Microgel-tethering physically positions the probes away from the underlying hard substrate and maintains them in a highly waterlike environment. This paper addresses the question of whether molecular crowding affects the performance of microgel-tethered molecular beacon probes. The density of probe-tethering sites is controlled experimentally using thin-film blends of biotin-terminated [PEG-B] and hydroxyl-terminated [PEG-OH] poly(ethylene glycol) from which microgels are synthesized and patterned by electron beam lithography. Fluorescence measurements indicate that the number of streptavidins, linear DNA probes, hairpin probes, and molecular beacon probes bound to the microgels increases linearly with increasing PEG-B/PEG-OH ratio. For a given tethering-site concentration, more linear probes can bind than structured probes. Crowding effects emerge during the hybridization of microgel-tethered molecular beacons but not during the hybridization of linear probes, as the tethering density increases. Crowding during hybridization is associated with conformational constraints imposed by the close proximity of closed and hybridized structured probes. The signal-to-background ratio (SBR) of hybridized beacons is highest and roughly constant for low tethering densities and decreases at the highest tethering densities. Despite differences between microgel tethering and traditional oligonucleotide surface-immobilization approaches, these results show that crowding defines an optimum tethering density for molecular beacon probes that is less than the maximum possible, which is consistent with previous studies involving various linear and structured oligonucleotide probes.