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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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Arcing and field-included surface erosion reduced by electrostatic shields around windings and ferromagnetic core of 80-kilovolt isolation transformer. Fabricated from high-resistivity polyurethane-based material brushed on critical surfaces, shields maintained at approximately half potential difference of windings.
Hybrid microelectronics relay has characteristics significantly superior to conventional solid state relays. Relay provides 2500 Vdc input to output isolation and operates from high threshold logic signal to switch load of 400 Vdc at 2 mA. Technology should be of interest to manufacturers of discrete components.
A chemical vapor deposition (CVD) process has been used to produce device structures of n- and p-type 6H-SiC epitaxial layers on commercially produced single-crystal 6H-SiC wafers. Mesa-style p-n junction diodes were successfully fabricated from these device structures using reactive ion etching, oxide passivation, and electrical contact metallization techniques. When tested in air, the 6H-SiC diodes displayed excellent rectification characteristics up to the highest temperature tested, 600 C. To observe avalanche breakdown of the p-n junction diodes, testing under a high-electrical-strength liquid was necessary. The avalanche breakdown voltage was 1000 V representing the highest reverse breakdown voltage to be reported for any CVD-grown SiC diode.
Surface-charged particle interactions were investigated for a small 100 sq cm conventionally constructed solar cell panel in ground facilities and in a flight experiment. The flight data substantiated preflight ground test results showing that at high positive biases the cover glass over each solar cell enhances the coupling current and that, at high negative biases, arcs create large transients in the coupling current.
Lunar pyroxenes from Apollo 11, 12, 14, and 15 were investigated. The iron-rich and magnesium-rich pyroxene specimens were crushed to a grain size of ca. 50 microns and studied by a combination of X-ray and electron diffraction, electron microscopy, 57 Fe Mossbauer spectroscopy and X-ray crystallography techniques. Highly ordered, uniform electron-dense bands, corresponding to exsolution lamellae, with average widths of ca. 230A to 1000A dependent on the source specimen were observed. These were?qr separated by wider, less-dense interband spacings with average widths of ca. 330A to 3100A. In heating experiments, splitting of the dense bands into finer structures, leading finally to obliteration of the exsolution lamellae was recorded. The extensive exsolution is evidence for significantly slower cooling rates, or possibly annealing, at temperatures in the subsolidus range, adding evidence that annealing of rock from the surface of the moon took place at ca. 600 C. Correlation of the band structure with magnetic ordering at low temperatures and iron clustering within the bands was studied.
The usefulness of LANDSAT data in the planning of transmission line routes was assessed. LANDSAT digital data and image processing techniques, specifically a multi-date supervised classification aproach, were used to develop a land cover map for an agricultural area near Fresno, California. Twenty-six land cover classes were identified, of which twenty classes were agricultural crops. High classification accuracies (greater than 80%) were attained for several classes, including cotton, grain, and vineyards. The primary products generated were 1:24,000, 1:100,000 and 1:250,000 scale maps of the classification and acreage summaries for all land cover classes within four alternate transmission line routes.
Hexagonal boron nitride (hBN) and Titanium dioxide are both ceramic materials with widespread use in commercial and consumer applications in everything from cosmetics and paint to deep space satellite components. As a dielectric material, hBN is electrically insulating, thermally conductive, and stable to most temperatures and environments. Titanium dioxide is also a good electrical insulator with a wide bandgap and large dielectric constant, as well as high temperature tolerance and chemical stability. This presentation covers our recent efforts to combine the best properties of hBN and titanium dioxide to produce an intercalated hBN:titanium dioxide composite which was then further processed and incorporated into polymer composites, as well as a standalone ceramic material for testing as a novel insulation material.
Presently, hybrid Remote Power Controllers (RPC's) are in production and prototype units are available for systems utilizing 28VDC, 120VDC, 115VAC/400 Hz and 230VAC/400 Hz. This paper describes RPC development in a new area of application: HVDC distribution systems utilizing 270/300VDC. Two RPC current ratings, 1 amp and 2 amps, were selected for development as they are adequate to control 90% of projected system loads. The various aspects and trade-offs encountered in circuit development are discussed with special focus placed on the circuits that see the duress of the high dc potentials. The comprehensive evaluation tests are summarized which confirmed the RPC compliance with the specification and with system/load compatibility requirements. In addition, present technology status and new applications are summarized.
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.
Transonic and supersonic aerodynamic characteristics for two-stage rocket vehicle with blunted nose cone on square body with conical flare termination
Discharge current with oscillation frequency proportional to anode voltage and magnetic field
Prebreakdown currents, conditioning rates and ultimate voltage capability of vacuum gaps and solid insulation, analyzing data on large-gap concentric cylinder configuration
Performance of mercury electron bombardment thrustor at large acceleration potential
Outgassing problems encountered in design of star tracker used on orbiting astronomical observatory
Scanning microscope uses a field-emission tip for the electron source, an electron gun that simultaneously accelerates and focuses electrons from the source, and one auxiliary lens to produce a final probe size at the specimen on the order of angstroms.
Cathode surface whiskers initiating electrical breakdown in ultrahigh vacuum
Malfunctions and failures in OAO spacecraft due to interactions between electrical systems and surrounding ionospheric plasma
Failure analysis of scanning spectrometer of reflecting telescope aboard OSO-4