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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS2013

Aspects of Collisionless Magnetic Reconnection in Asymmetric Systems

Asymmetric reconnection is being investigated by means of particle-in-cell simulations. The research has two foci: The direction of the reconnection line in configurations with nonvanishing magnetic fields; and the question why reconnection can be faster if a guide field is added to an otherwise unchanged asymmetric configuration. We find that reconnection prefers a direction, which maximizes the available magnetic energy, and show that this direction coincides with the bisection of the angle between the asymptotic magnetic fields. Regarding the difference in reconnection rates between planar and guide field models, we demonstrate that a guide field can provide essential confinement for particles in the reconnection region, which the weaker magnetic field in one of the inflow directions cannot necessarily provide.

Hesse, Michael↗
NASA NTRS1974

The influence of a constant magnetic field on the coagulatory system of the blood in an experiment

The influence of a constant magnetic field with a strength of 2500 oersteds on the coagulatory system of the blood in rabbits was studied; the animals were subjected to this field for one and five hours. The magnetic field acts on the coagulatory system of the blood after only one hour exposure. Repeated 5-hour exposures cause activation of the anticoagulatory system in the blood and causes distinctive effects on the subsequent changes in the coagulatory system of the blood. It is quite likely that in this instance the adaptational properties of the organism make themselves felt.

Zabrodina, L. V.↗
NASA NTRS1994

Superconducting Electromagnetic Suspension (EMS) system for Grumman Maglev concept

The Grumman developed Electromagnetic Suspension (EMS) Maglev system has the following key characteristics: a large operating airgap--40 mm; levitation at all speeds; both high speed and low speed applications; no deleterious effects on SC coils at low vehicle speeds; low magnetic field at the SC coil--less than 0.35 T; no need to use non-magnetic/non-metallic rebar in the guideway structure; low magnetic field in passenger cabin--approximately 1 G; low forces on the SC coil; employs state-of-the-art NbTi wire; no need for an active magnet quench protection system; and lower weight than a magnet system with copper coils. The EMS Maglev described in this paper does not require development of any new technologies. The system could be built with the existing SC magnet technology.

Kalsi, Swarn S.↗
NASA NTRS1986

Text Exchange System

Text Exchange System (TES) exchanges and maintains organized textual information including source code, documentation, data, and listings. System consists of two computer programs and definition of format for information storage. Comprehensive program used to create, read, and maintain TES files. TES developed to meet three goals: First, easy and efficient exchange of programs and other textual data between similar and dissimilar computer systems via magnetic tape. Second, provide transportable management system for textual information. Third, provide common user interface, over wide variety of computing systems, for all activities associated with text exchange.

Snyder, W. V.↗
NASA NTRS1995

Safety analysis

We are engaged in a research program in safety-critical computing that is based on two case studies. We use these case studies to provide application-specific details of the various research issues, and as targets for evaluation of research ideas. The first case study is the Magnetic Stereotaxis System (MSS), an investigational device for performing human neurosurgery being developed in a joint effort between the Department of Physics at the University of Virginia and the Department of Neurosurgery at the University of Iowa. The system operates by manipulating a small permanent magnet (known as a 'seed') within the brain using an externally applied magnetic field. By varying the magnitude and gradient of the external magnetic field, the seed can be moved along a non-linear path and positioned at a site requiring therapy, e.g., a tumor. The magnetic field required for movement through brain tissue is extremely high, and is generated by a set of six superconducting magnets located in a housing surrounding the patient's head. The system uses two X-ray cameras positioned at right angles to detect in real time the locations of the seed and of X-ray opaque markers affixed to the patient's skull. the X-ray images are used to locate the objects of interest in a canonical frame of reference. the second case study is the University of Virginia Research Nuclear Reactor (UVAR). It is a 2 MW thermal, concrete-walled pool reactor. The system operates using 20 to 25 plate-type fuel assemblies placed on a rectangular grid plate. There are three scramable safety rods, and one non-scramable regulating rod that can be put in automatic mode. It was originally constructed in 1959 as a 1 MW system, and it was upgraded to 2 MW in 1973. Though only a research reactor rather than a power reactor, the issues raised are significant and can be related to the problems faced by full-scale reactor systems.

Knight, John C.↗
NASA NTRS1982

A jet controlled magnetic referenced attitude control system for spinning payloads

An attitude control system was designed permitting large angle acquisition and alignment of the principle axis of a spinning payload to within 1 degree of the earth's magnetic field. Signals from magnetometer and gyro sensors are fed to the control algorithm to generate commands for the jet thrusters. The algorithm contains a cross axis magnetometer signal to prevent a large angle magnetometer signal to prevent a large angle equilibrium solution. The acquisition will occur within 50 seconds from initial precession and nutation angles of 30 degrees. An electronic spin filter passes signals at spin and nutation frequencies and rejects bias signals due to sensor misalignment and principle axis offset. Describing function analysis and total analog simulation techniques were used. The flight ACS hardware was interfaced with the analog computer simulation for design and verification. The controller has flown on four successful missions.

Celmer, J. J.↗
NASA NTRS2012

The Role of Geometry in Magnetic Reconnection

Magnetic reconnection is arguably the most effective energy conversion and transport process in plasmas. Reconnection is subject to topological considerations in two ways. First, the process itself involves a change in topology of the combined plasma-magnetic field system. This change in topology transcends that of the magnetic field alone and accounts for flux transport relative to the motion of the plasma in the system under investigation. The second way topology is important to magnetic reconnection is through modifications of the diffUSion/dissipation physics brought about by the structure of the reconnecting system. This presentation will present an overview and summary of both past and recent results pertaining to both aspects.

Hesse, Michael↗
NASA NTRS2005

Magnetic Characterization of Micro Shutters for James Web Space Telescope (JWST)

Summary of Research that was part of the grant: NASA NAG5 - 13405: Magnetic Characterization of Micro Shutters for James Web Space Telescope (JWST) Period: May 1 2003-October 31 2005 The above funding resulted in following major achievements related to microshutter system for JWST. 1. The original rectangular pattern of magnetic material was changed into magnetic striped pattern to prevent unnecessary twisting during the actuation. The Original geometry favored magnetic remanence vector being oriented along the longer side of the shutter and thus resulting torque caused out of plane twist. Stripe pattern minimizes the out of plane motion and thus prolongs the life-time of microshutter device. 2. We built a new magnetic system (magnetic rotisserie) allowing an accelerated life test of microshutters at various temperatures. This system identified that shutter are capable to withstand as many as several millions of actuating cycles. Our system also identified fabrication related features, like bowing with temperature, collisions with the frame due to misalignment, delaminating of the light shields due to uncontrolled voltage release and poorly fabricated light shields.

Wasilewski, P.↗
NASA NTRS2006

Heat Transfer of Thermocapillary Convection in a Two-Layered Fluid System Under the Influence of Magnetic Field

Heat transfer of a two-layer fluid system has been of great importance in a variety of industrial applications. For example, the phenomena of immiscible fluids can be found in materials processing and heat exchangers. Typically in solidification from a melt, the convective motion is the dominant factor that affects the uniformity of material properties. In the layered flow, thermocapillary forces can come into an important play, which was first emphasized by a previous investigator in 1958. Under extraterrestrial environments without gravity, thermocapillary effects can be a more dominant factor, which alters material properties in processing. Control and optimization of heat transfer in an immiscible fluid system need complete understanding of the flow phenomena that can be induced by surface tension at a fluid interface. The present work is focused on understanding of the magnetic field effects on thermocapillary convection, in order to optimize material processing. That is, it involves the study of the complicated phenomena to alter the flow motion in crystal growth. In this effort, the Marangoni convection in a cavity with differentially heated sidewalls is investigated with and without the influence of a magnetic field. As a first step, numerical analyses are performed, by thoroughly investigating influences of all pertinent physical parameters. Experiments are then conducted, with preliminary results, for comparison with the numerical analyses.

Ramachandran, N.↗
NASA NTRS1989

Prototype of a magnetically suspended flywheel energy storage system

The authors describe recent progress in the development of a 500-Wh magnetically suspended flywheel stack energy storage system. The design of the system and a critical study of the noncontacting displacement transducers and their placement in the stack system are discussed. The storage system has been designed and constructed and is currently undergoing experimental analysis. The results acquired from the noncontacting displacement transducer study show that currently available transducers will not function as desired and that further research is essential.

Plant, David P.↗
NASA NTRS1988

An electrostatically and a magnetically confined electron gun lens system

Focal properties, electron trajectory calculations, and geometries are given for two electron 'gun' lens systems that have a variety of applications in, for example, electron-neutral and electron-ion scattering experiments. One nine-lens system utilizes only electrostatic confinement and is capable of focusing electrons onto a fixed target with extremely small divergence angles, over a range of final energies 1-790 eV. The second gun lens system is a simpler three-lens system suitable for use in a uniform, solenoidal magnetic field. While the focusing properties of such a magnetically confined lens systenm are simpler to deal with, the system does illustrate features of electron extraction and Brillouin flow that have not been suitably emphasized in the literature.

Bernius, Mark T.↗
NASA NTRS1995

Modeling using optimization routines

Modeling using mathematical optimization dynamics is a design tool used in magnetic suspension system development. MATLAB (software) is used to calculate minimum cost and other desired constraints. The parameters to be measured are programmed into mathematical equations. MATLAB will calculate answers for each set of inputs; inputs cover the boundary limits of the design. A Magnetic Suspension System using Electromagnets Mounted in a Plannar Array is a design system that makes use of optimization modeling.

Thomas, Theodore↗
NASA NTRS1985

Status of wind tunnel magnetic suspension research

This paper reports the status of the NASA Langley Research Center program aimed at the development of the technology required for large-scale Magnetic Suspension and Balance Systems. The use of magnetic suspension of the model in a wind tunnel is seen to be the only viable method to eliminate aerodynamic interference problems arising with mechanical model-supports. The two small-scale magnetic suspension systems in operation at Langley are the only ones now active in the U.S. The general features and capabilities of these two systems and all of the ongoing research in the use of magnetic suspension are described.

Boyden, R. P.↗
NASA NTRS1989

Antiproton powered propulsion with magnetically confined plasma engines

Matter-antimatter annihilation releases more energy per unit mass than any other method of energy production, making it an attractive energy source for spacecraft propulsion. In the magnetically confined plasma engine, antiproton beams are injected axially into a pulsed magnetic mirror system, where they annihilate with an initially neutral hydrogen gas. The resulting charged annihilation products transfer energy to the hydrogen propellant, which is then exhausted through one end of the pulsed mirror system to provide thrust. The calculated energy transfer efficiencies for a low number density (10(14)/cu cm) hydrogen propellant are insufficient to warrant operating the engine in this mode. Efficiencies are improved using moderate propellant number densities (10(16)/cu cm), but the energy transferred to the plasma in a realistic magnetic mirror system is generally limited to less than 2 percent of the initial proton-antiproton annihilation energy. The energy transfer efficiencies are highest for high number density (10(18)/cu cm) propellants, but plasma temperatures are reduced by excessive radiation losses. Low to moderate thrust over a wide range of specific impulse can be generated with moderate propellant number densities, while higher thrust but lower specific impulse may be generated using high propellant number densities. Significant mass will be required to shield the superconducting magnet coils from the high energy gamma radiation emitted by neutral pion decay. The mass of such a radiation shield may dominate the total engine mass, and could severely diminish the performance of antiproton powered engines which utilize magnetic confinement. The problem is compounded in the antiproton powered plasma engine, where lower energy plasma bremsstrahlung radiation may cause shield surface ablation and degradation.

Lapointe, Michael R.↗
NASA NTRS1994

Neural network controller development for a magnetically suspended flywheel energy storage system

A neural network controller has been developed to accommodate disturbances and nonlinearities and improve the robustness of a magnetically suspended flywheel energy storage system. The controller is trained using the back propagation-through-time technique incorporated with a time-averaging scheme. The resulting nonlinear neural network controller improves system performance by adapting flywheel stiffness and damping based on operating speed. In addition, a hybrid multi-layered neural network controller is developed off-line which is capable of improving system performance even further. All of the research presented in this paper was implemented via a magnetic bearing computer simulation. However, careful attention was paid to developing a practical methodology which will make future application to the actual bearing system fairly straightforward.

Fittro, Roger L.↗
NASA NTRS1978

Magnetic suspension and pointing system

An apparatus is reported for accurate pointing of instruments on a carrier vehicle and for isolation of the instruments from the vehicle's motion disturbances. The apparatus includes two assemblies with connecting interfaces. The first assembly is attached to the carrier vehicle and consists of an azimuth gimbal and an elevation gimbal which provide coarse pointing by allowing two rotations of the instruments relative to the carrier vehicle. The second or vernier pointing assembly is made up of magnetic suspension and fine pointing actuators, roll motor segments, and an instrument mounting plase which provides appropriate magnetic circuits for the actuators and the roll motor segments. The vernier pointing assembly provides attitude fine pointing and roll positioning of the instruments as well as six degree-of-freedom isolation from carrier motion disturbances.

Anderson, W. W.↗