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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 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Magnetosonic waves adjacent to the plasma sheet in the distant magnetotail - ISEE-3

The presence of large-amplitude magnetosonic waves in the distant plasma sheet boundary layers is demonstrated, and their properties are discussed. The waves for almost all the events examined are right-hand circularly polarized, with the degree of polarization varying from 1.04 to 1.87, i.e., from circular to slightly elliptical. The waves are all propagating nearly along the magnetic field. Their periods vary from 3.7 seconds to as long as 35 seconds, with a median value of about 10 seconds, and are slightly larger than the proton gyroperiod in all but two cases. Most waves have a relatively large compressional component varying from 30 to 90 percent of the wave amplitude. Several possible generation mechanisms are discussed, along with the role that the waves may play in the heating and expansion of the plasma sheet.

Tsurutani, B. T.↗
NASA NTRS1983

Sheet silicon cell/module technology

The cost involved in the performance of the standard operations for the manufacture of silicon wafers is insignificant in the case of space photovoltaics applications. It is, however, a decisive factor with respect to terrestrial applications of silicon photovoltaic devices. In 1975, a program was, therefore, begun to develop low cost silicon solar arrays for terrestrial applications. The goal was silicon-based photovoltaic (PV) modules ready for installation at a selling price of $0.50/watt (1975 dollars). Sheet and ribbon silicon growth held out the promise of reduced cost through continuous operation, high material throughput, high material utilization efficiency, and a product whose shape lent itself to the assembly of high packing density modules. Attention is given to ribbon growth technologies, sheet technology generic problems, and ribbon cell and module technology status. It is concluded that the potential for crystalline ribbon silicon appears to be better today than ever before.

Morrison, A. D.↗
NASA NTRS1985

Silicone Coating on Polyimide Sheet

Silicone coatings applied to polyimide sheeting for variety of space-related applications. Coatings intended to protect flexible substrates of solar-cell blankets from degradation by oxygen atoms, electrons, plasmas, and ultraviolet light in low Earth orbit and outer space. Since coatings are flexible, generally useful in forming flexible laminates or protective layers on polyimide-sheet products.

Park, J. J.↗
NASA NTRS1985

Cutting Guide for Fibrous Sheets

Tool facilitates repetitive cutting of fibrous sheets. Flexible aluminum tape allows metal strips folded back on themselves, exposing fresh material for cutting. More than one strip folded back, and cutting width therefore increased in multiples of strip width. Developed for cutting strips of alumina-fiber matting, tool also used on such materials as felts, textiles, and sheet metals.

Warren, A., D.↗
NASA NTRS1986

Synthesis of Metal Phthalocyanine Sheet Polymers

New method for synthesizing metal phthalocyanine tetracarboxylic acids (MPTCA's) yields high purity end product. In addition, high-purity metal phthalocyanine sheet polymers synthesized from compounds. Monomer formed into sheet polymer by heating. Units of polymer linked in manner similar to phenyl-group linkages in biphenyl: Conjugation extends throughout macromolecule, thereby increasing delocalization of TT-electrons. Increases conductivity and thermal stability of polymer.

Achar, B. N.↗
NASA NTRS1983

Cold streams of ionospheric oxygen in the plasma sheet during the CDAW-6 event of March 22, 1979

During magnetospheric substorm events, the plasma and ion composition experiments in the ISEE-1 and 2 satellites detected cold ionospheric O+ streams, moving tailwards in the near Earth magnetotail. Flow is parallel to the magnetic field lines, with drift velocity in agreement with the electric field topology obtained by mapping the model ionospheric field along the magnetic field lines. Fluctuations of the flow velocity of the streams can be related to magnetotail movements. Oscillations of the flow direction and speed with periods ranging from 5 to 10 min that suggest the presence of waves are observed. The streams are observed at all distances between 15 and 6 Re from the Earth. When averaged over 360 deg, the streams show up as a low energy peak, superimposed on the distribution of isotropic plasma sheet ions. This double-peak structure of the energy spectrum seems typical of the disturbed plasma sheet.

Orsini, S.↗
NASA NTRS1985

High-efficiency cell concepts on low-cost silicon sheets

The limitations on sheet growth material in terms of the defect structure and minority carrier lifetime are discussed. The effect of various defects on performance are estimated. Given these limitations designs for a sheet growth cell that will make the best of the material characteristics are proposed. Achievement of optimum synergy between base material quality and device processing variables is proposed. A strong coupling exists between material quality and the variables during crystal growth, and device processing variables. Two objectives are outlined: (1) optimization of the coupling for maximum performance at minimal cost; and (2) decoupling of materials from processing by improvement in base material quality to make it less sensitive to processing variables.

Bell, R. O.↗
NASA NTRS1984

Silicon sheet surface studies

Several activities were performed in the area of silicon sheet surface studies. An interferometry technique was developed for measuring residual stresses in short, thin silicon sheets. Simulation of abrasion of silicon by diamond and by scrating and indentation tests was carried out. The wear rate in silicon was correlated with a wear model.

Danyluk, S.↗
NASA NTRS1985

Detection threshold energy of high energy cascade showers using thermoluminescence PTFE-sheet and hot-gas reader

A new thermoluminescence (TL) sheet was developed as a detector for high energy components in air showers. For the investigation of detection threshold energy for a cascade showeer, TL sheets were exposed at Mt. Fuji with X ray films in emulsion chambers and were scanned by a hot-gas reader. It is concluded that if a gamma ray whose energy is more than 6 TeV enters vertically into lead chambers, the resulting cascade shower is readily detectable at maximum development.

Kino, S.↗
NASA NTRS1985

Spatial distribution read-out system for thermoluminescence sheets

A spatial distribution read-out system of thermoluminescence (TL) sheets is developed. This system consists of high gain image intensifier, a CCD-TV camera, a video image processor and a host computer. This system has been applied to artificial TL sheets (BaSO4:Eu doped) for detecting high energy electromagnetic shower and heavy nuclei tracks.

Yamamoto, I.↗
NASA NTRS1985

Substorm effects on the plasma sheet ion composition on March 22, 1979 (CDAW 6)

One of the potentially most useful aspects of mass spectroscopy in magnetospheric research is related to the ability to distinguish between ions of solar wind and terrestrial origins. Knowing the source of the plasmas in various regions and under various geomagnetic conditions is crucial in improving the understanding of particle flows in the magnetosphere. Sharp et al. (1982) found that the plasma sheet ions in the 0.1- to 16-keV/e range, were predominantly of solar wind origin during low geomagnetic activity, while there was a large terrestrial component during active times. This paper presents a set of data from March 22, 1979. The reported investigation represents the first detailed case study of the relation between geomagnetic substorm activity and the ion composition in the plasma sheet. A decrease in solar wind ion flow at ISEE 1 and the subsequent increase in the flow of ionospheric ions is interpreted as evidence of a fundamental change in the particle flow pattern following the start of substorm activity.

Lennartsson, W.↗
NASA NTRS1984

Ice sheet surface features from satellite radar altimetry

Fourteen SEASAT and ten GEOS-3 satellite radar altimeter groundtracks across a 1 deg x 2.5 deg study area in southwestern Greenland have yielded 3,328 ice sheet surface eievations. The surface elevations derived from SEASAT were recalculated based on a waveform retracking algorithm. The elevations have been utilized to develop a surface profile, a three dimensional surface representation, and surface contours. Analysis of the elevations reveals the presence of surface terraces, some greater than 100 km in length; each terrace is at a discrete elevation. Renormalized SEASAT AGC values are shown to be correlated with the surface slope. The ice surface undulations caused frequent altimeter losses-of-lock. Future satellite radar altimeters could significantly contribute to ice sheet mapping in the next decade, particularly if they incorporate tracking systems with more frequent updates.

Brooks, R. L.↗
NASA NTRS1985

Cold streams of ionospheric oxygen in the plasma sheet during the CDAW 6 event of March 22, 1979

During magnetospheric substorm events, the plasma and ion composition experiments in the ISEE-1 and 2 satellites detected cold ionospheric O+ streams, moving tailwards in the near earth magnetotail. Flow is parallel to the magnetic field lines, with drift velocity in agreement with the electric field topology obtained by mapping the model ionospheric field along the magnetic field lines. Fluctuations of the flow velocity of the streams can be related to magnetotail movements. Oscillations of the flow direction and speed with periods ranging from 5 to 10 min that suggest the presence of waves are observed. The streams are observed at all distances between 15 and 6 Re from the earth. When averaged over 360 deg, the streams show up as a low energy peak, superimposed on the distribution of isotropic plasma sheet ions. This double-peak structure of the energy spectrum seems typical of the disturbed plasma sheet.

Orsini, S.↗
NASA NTRS1985

Observations of steady anomalous magnetic heating in thin current sheets

The Hard X-ray Imaging Spectrometer of the Solar Maximum Mission has yielded observations of a faint, steadily emitting loop-like structure, which have allowed the thermal evolution of this loop over a period of about 15 hr to be followed. Only 0.1 percent of the volume of the loop appears to be steadily heated, at the large rate of 0.6 erg/cu cm sec; this suggests that the heating represents the dissipation of magnetic fields in thin current sheets. Ion-kinetic tearing, as proposed by Galeev et al. (1981), is noted to be especially consonant with these observations. The source of the present X-ray emission is identified with the H-alpha filament in the same region. The present findings are held to constitute the first direct evidence for the steady dissipation of coronal magnetic fields via enhanced thin current sheet resistivity.

Martens, P. C. H.↗
NASA NTRS1985

A simulation study of distortion of the heliospheric sheet caused by solar activity

During major geomagnetic storms, the interplanetary magnetic field angle, phi, changes often abruptly, either from 135 to 315 or 315 to 135 deg, suggesting that the heliospheric current sheet is pushed upward or downward by disturbed solar wind. The distortion of the heliospheric current sheet by three successive solar flares is simulated to show that such a flapping motion can occur.

Fry, C. D.↗
NASA NTRS1986

Entrainment, transport and concentration of meteorites in polar ice sheets

Glaciers and ice sheets act as slow-moving conveyancing systems for material added to both their upper and lower surfaces. Because the transit time for most materials is extremely long the ice acts as a major global storage facility. The effects of horizontal and vertical motions on the flow patterns of Antarctic ice sheets are summarized. The determination of the source areas of meteorites and their transport paths is a problem of central importance since it relates not only directly to concentration mechanisms but also to the wider issues in glaciology and meteorites. The ice and snow into which a meteorite falls, and which moves with it to the concentration area, encodes information about the infall area. The principle environmental conditions being former elevation, temperature (also related to elevation), and age of the ice. This encoded information could be used to identify the infall area.

Drewry, D. J.↗
NASA NTRS1985

Vortex sheet modeling with higher order curved panels

A numerical technique is presented for modeling the vortex sheet with a deformable surface definition, along which a continuous vortex strength distribution in the spanwise direction is applied, so that by repeatedly modifying its shape, its true configuration is approached, in the proximity of its generating wing. Design problems requiring the inclusion of a realistic configuration of the vortex sheet are numerous. Examples discussed include: control effectiveness and stability derivatives, longitudinal stability, lateral stability, canards, propellers and helicopter rotors, and trailing vortex hazards.

Nagati, M. G.↗