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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

A comparison of intense electrostatic waves near f-UHR with linear instability theory

Intense electrostatic waves near the upper hybrid resonance frequency (f-UHR) have recently been detected near but beyond the plasmapause between + or -50 deg magnetic latitude at all local times. The paper shows that the electrostatic waves observed with the ISEE 1 plasma wave receiver near f-UHR are in qualitative agreement with linear theory of multicyclotron harmonic emissions. The peak amplitudes and bandwidths observed are similar to those calculated for maximum spatial growth rates. Measurements on Hawkeye of similar waves suggest that the electric field polarization is also consistent with theory. For a wide range of plasma parameters, nonconvective instability or large spatial growth rates occur within the cyclotron band encompassing the cold upper hybrid frequency.

Kurth, W. S.↗
NASA NTRS1979

Electrostatic beneficiation of ores on the moon surface

The feasibility of the electrostatic beneficiation of lunar ores is studied. It is shown that the lunar environment with its sustained high vacuum, low temperature, and low acceleration of gravity, is suitable for the use of the electrostatic technique with magnetic as well as nonmagnetic ores. Only an initial coarse screening will be required prior to processing, as the lunar soil is already in fine particulate form. The low temperature and the absence of water suggest the use of tribo-electrification for the electric charging of lunar soils.

Inculet, I. I.↗
NASA NTRS1980

Electrostatic waves in the Jovian magnetosphere

Observations by the plasma wave receivers on Voyagers 1 and 2 show that a wide variety of electrostatic waves are present within the Jovian magnetosphere and that the Jovian electrostatic waves are for the most part very similar to those observed in the terrestrial magnetosphere. Bands of emission near the upper hybrid resonance frequency in the dayside outer magnetosphere are detected between higher harmonics of the electron gyrofrequency. Inside of about 23 Jupiter radii, electron cyclotron harmonic emissions appear to be durable features of the inner Jovian magnetosphere and are extremely well confined to the Jovian magnetic equator. The cyclotron emissions extend from just above the local electron gyrofrequency to the upper hybrid resonance frequency.

Kurth, W. S.↗
NASA NTRS1981

Electrostatic antenna space environment interaction study

The interactions of the electrostatic antenna with the space environment in both low Earth orbit and geosynchronous orbit are investigated. It is concluded that the electrostatically controlled membrane mirror is a viable concept for space applications. However, great care must be taken to enclose the high voltage electrodes in a Faraday cage structure to separate the high voltage region from the ambient plasma. For this reason, metallized cloth is not acceptable as a membrane material. Conventional spacecraft charging at geosynchronous orbit should not be a problem provided ancillary structures (such as booms) are given nonnegligible conductivity and adequate grounding. Power loss due to plasma electrons entering the high field region is a potentially serious problem. In low earth orbit any opening whatever in the Faraday cage is likely to produce an unacceptable power drain.

Katz, I.↗
NASA NTRS1981

Additional application of the NASCAP code. Volume 2: SEPS, ion thruster neutralization and electrostatic antenna model

The interactions of spacecraft systems with the surrounding plasma environment were studied analytically for three cases of current interest: calculating the impact of spacecraft generated plasmas on the main power system of a baseline solar electric propulsion stage (SEPS), modeling the physics of the neutralization of an ion thruster beam by a plasma bridge, and examining the physical and electrical effects of orbital ambient plasmas on the operation of an electrostatically controlled membrane mirror. In order to perform these studies, the NASA charging analyzer program (NASCAP) was used as well as several other computer models and analytical estimates. The main result of the SEPS study was to show how charge exchange ion expansion can create a conducting channel between the thrusters and the solar arrays. A fluid-like model was able to predict plasma potentials and temperatures measured near the main beam of an ion thruster and in the vicinity of a hollow cathode neutralizer. Power losses due to plasma currents were shown to be substantial for several proposed electrostatic antenna designs.

Katz, I.↗
NASA NTRS1981

Numerical simulation of the generation of electrostatic turbulence in the magnetotail

A two-dimensional plasma model is used to investigate the development of electrostatic turbulence in a magnetized plasma from plasma instabilities. The simulation consists of following the motion of 100,000 ions in their self-consistent electrostatic field. The electrons are treated as a constant neutralizing background. The instabilities modeled are driven by a ring-type velocity distribution and by interpenetrating ion beams in a time-variable magnetic field. Instability growth times are of the order of an ion gyroperiod in the case of the ring distribution and of the order of an ion plasma period in the case of the beam simulation. Maximum potential differences generated are of the order of the ion kinetic energies. These simulations demonstrate the cascade of wave energy to long wavelengths, thus showing the E x B turbulence can be generated from plasma microinstabilities. After the free energy feeding, the instabilities are exhausted, and wave energy at wavelengths less than an ion gyrodiameter decays quickly to equilibrium levels, while longer wavelength modes persist for much longer times. In one model with a time dependent, but spatially uniform, magnetic field the electric field energy at long wavelengths appeared to increase as a result of the increase of the magnetic field.

Swift, D. W.↗
NASA NTRS1981

Double layers and electrostatic shocks

It is shown that it is useful to define double layers and shocks so that the ion phase spaces of double layers are the mirror image (about zero ion velocity) of the ion phase spaces for laminar electrostatic shocks. The distinguishing feature is the direction of the free ion velocity. It is also shown that double layers can exist without the presence of trapped ions. The Bohm condition for double layers, that the ion drift velocity on the high potential side must be greater than the ion sound velocity, is shown to be related to a requirement of a lower limit on the Mach number of laminar electrostatic shocks

Hershkowitz, N.↗
NASA NTRS1981

Test progress on the electrostatic membrane reflector

An extemely lightweight type of precision reflector antenna, being developed for potential deployment from the space shuttle, uses electrostatic forces to tension a thin membrane and form it into a concave reflector surface. The typical shuttle-deployed antenna would have a diameter of 100 meters and an RMS surface smoothness of 10 to 1 mm for operation at 1 to 10 GHz. NASA Langley Research Center built and is currently testing a subscale (16 foot diameter) model of the membrane reflector portion of such an antenna. Preliminary test results and principal factors affecting surface quality are addressed. Factors included are the effect of the perimeter boundary, splicing of the membrane, the long-scale smoothness of commercial membranes, and the spatial controllability of the membrane using voltage adjustments to alter the electrostatic pressure. Only readily available commercial membranes are considered.

Mihora, D. J.↗
NASA NTRS1982

Conceptual design of electrostatic antenna

The concept of using electrostatic forces to tension a thin, conducting membrane and maintain it in a precision antenna shape is discussed. This electrostatically controlled membrane mirror is an adpative structure which maintains surface quality despite errors in construction, irregularities of materials, solar heating, and on board disturbances.

Coyner, J. V.↗
NASA NTRS1981

Energization of ionospheric ions by electrostatic hydrogen cyclotron waves

Interactions between ionospheric ions and electrostatic hydrogen cyclotron waves are studied numerically in an investigation of a possible mechanism for the energization of the low-energy ionospheric ions flowing along geomagnetic field lines to high altitudes. Ion equations of motion are solved numerically for a given number of O(+), He(+) and He(2+) ions initially in a Maxwellian distribution. All the ions considered are found capable of undergoing stochastic acceleration by a coherent electrostatic hydrogen cyclotron wave with parameters typical of the auroral plasma above 1 earth radius. The fraction of the initial ion population undergoing heating depends strongly on the mass, charge and initial temperature of the ion species, with O(+) ions only heated when their initial temperature is approximately greater than the hydrogen temperature and the lighter ions able to be heated even when cold, due to cyclotron resonant stochastic heating.

Singh, N.↗
NASA NTRS1981

Stationary electrostatic solitary waves in the auroral plasma

Time-stationary fluid equations are used to describe electrostatic solitons in an auroral plasma of cold ionospheric and hot plasma sheet particles. A one-dimensional fluid analysis of the four component model auroral plasma indicates that at least two different, weakly damped, small amplitude electrostatic solitons can propagate along the geomagnetic field. The slower of the two is a generalization of an ion-acoustic solitary wave in a multi-component plasma, and ion inertia is negligible for the faster mode which is supported by the two electron components and resembles a clump of shielded negative space charge convected by the drifting plasma sheet electrons. Some expected features of the large amplitude properties are indicated qualitatively, and an analogy is considered between the theory of ion-acoustic shocks and a theory of double layers.

Lotko, W.↗
NASA NTRS1981

Electron and ion acceleration by strong electrostatic turbulence

It is noted that, for waves observed on auroral field lines, ion trapping may be important, affecting models of transverse ion acceleration. The strength of the electrostatic ion cyclotron turbulence observed in the auroral zone may be attributed to the large convective growth rate that is associated with this mode. These waves may be destabilized by the enhancement in the field-aligned current that results from the onset of a magnetospheric substorm. The rise in the field-aligned current is associated with the passage of shear mode Alfven waves between the magnetosphere and ionosphere. When these Alfven waves have a perpendicular wavelength comparable to the ion gyroradius, they carry a parallel electric field that can accelerate the plasma in the topside auroral ionosphere, destabilizing the electrostatic ion cyclotron mode.

Lysak, R. L.↗
NASA NTRS1981

Electric fields and electrostatic potentials in the high latitude ionosphere

Recent interpretive studies of electric field-driven ionospheric plasma convection data from the AE-C satellite are described, where the instruments employed include an ion drift meter and an ion-retarding potential analyzer. Electrostatic potential curves are derived from ion drift velocity measurements for high-latitude segments of the satellite's orbit. The potential curves are shown to be useful in determining the character of the global electrostatic potential pattern, with emphasis on the separation of convective cells. Results are given for six orbits, with attention to the mid-day auroral region.

Banks, P. M.↗
NASA NTRS1984

Blowing Dust Away With Electrostatic Wind

Ionized air molecules drive away contaminants. Electrostatic wind prevents dust buildup and subsequent electrical breakdown in powerlines, transformers, switchgears, Van de Graaff generators, electrostatic precipitators, and other high-voltage equipment. Makes periodic cleaning or airblasting unnecessary.

Utter, M. G.↗
NASA NTRS1983

A search for Saturn electrostatic discharges in the Voyager plasma wave data

A search of Voyager spacecraft plasma wave data for evidence of Saturn electrostatic discharges, whose detection was suggested to be likely on the basis of radio astronomy observations, has yielded no evidence of this phenomenon. The statistical significance of this null result is analyzed, and its ramifications are commented upon. The explanations entertained for the lack of plasma wave observations of electrostatic discharges include the possibility that many events are of much shorter duration than previously reported, or that there may be a nonlinear distortion in the radio astronomy receiver employed which may have artificially broadened the spectrum of the discharges.

Kurth, W. S.↗
NASA NTRS1982

Electrostatic waves and the strong diffusion of magnetospheric electrons

A comprehensive review of electron pitch angle scattering in the magnetosphere and the plasma waves responsible for it is presented, emphasizing the strong diffusion of diffuse auroral electrons by electrostatic electron cyclotron harmonic waves. The weak diffusion of energetic radiation belt electrons within the plasmasphere is reviewed briefly. Several new suggestions concerning the quasilinear diffusion from and saturation of electrostatic waves are included.

Kennel, C. F.↗
NASA NTRS1984

Galactic heavy-ion shielding using electrostatic fields

The shielding of spacecraft against galactic heavy ions, particularly high-energy Fe(56) nuclei, by electrostatic fields is analyzed for an arrangement of spherical concentric shells. Vacuum breakdown considerations are found to limit the minimum radii of the spheres to over 100 m. This limitation makes it impractical to use the fields for shielding small spacecraft. The voltages necessary to repel these Fe(56) nuclei exceed present electrostatic generating capabilities by over 2 orders of magnitude and render the concept useless as an alternative to traditional bulk-material shielding methods.

Townsend, L. W.↗
NASA NTRS1983

A survey of electrostatic waves in Saturn's magnetosphere

The Voyager 1 and 2 plasma wave instruments have provided initial observations of electrostatic waves in Saturn's magnetosphere. In general, the emissions at Saturn are similar to those found at earth and Jupiter, although there are significant differences in some of the detailed characteristics. In this paper an overview is presented of the various types of electrostatic waves in the Saturnian magnetosphere, including Langmuir waves and electron cyclotron harmonic emissions. The temporal and spectral character, amplitude, and regions of occurrence for the various classes of emissions are summarized. These characteristics are compared with those of the terrestrial and Jovian counterparts with the goal of understanding how major differences in the magnetospheric configuration might contribute to the observed differences. Finally, the theory of electron cyclotron harmonic emissions is used to gain an insight into the electron distributions and possible wave-particle interactions in Saturn's magnetosphere.

Kurth, W. S.↗