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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 1,279 records · Page 71
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Large area silicon sheet by EFG

Progress in a program to produce high speed, thin, wide silicon sheets for fabricating 10% efficient solar cells is reported. An EFG ribbon growth system was used to perform growth rate and ribbon thickness experiments. A new, wide ribbon growth system was developed. A theoretical study of stresses in ribbons was also conducted. The EFG ribbons were observed to exhibit a characteristic defect structure which is orientation dependent in the early stages of growth.

Morrison, A. D.↗
NASA NTRS1977

Effect of simulated Earth reentry exposure on mechanical properties of several oxide dispersion strengthened and superalloy sheet materials

The effects of simulated multiple reentry into the earth's atmosphere on the mechanical properties of several high temperature metallic sheet materials were evaluated. The materials included five tin-gage (nominally 0.025- or 0.037-cm) oxide dispersion strengthened (ODS) alloys and two thin-gage (nominally 0.037-cm) superalloys. Multiple reentry conditions were simulated through cyclic Plasma Arc Tunnel (PAT) exposure. PAT exposure generally consisted of 100 cycles of 600 second duration at 1255, 1366, or 1477 K in a Mach 4.6 airstream with an impact pressure of nominally 800 N/m2. PAT exposure generally produced a uniform oxide scale, oxide pits or intergranular oxidation, Kirkendall porosity, and alloy depletion zones except for the aluminum-containing ODS alloys. Only a uniform oxide scale was formed on the aluminum-containing ODS alloys. PAT exposure did not significantly affect the mechanical properties of the thin-gage (nominally 0.025- or 0.037-cm) alloys evaluated. Thus it appears that the microstructural changes produced by Plasma Arc Tunnel exposure has little influence on mechanical properties.

Whittenberger, J. D.↗
NASA NTRS1976

A thrust-sheet propulsion concept using fissionable elements

A space propulsion concept is proposed and analyzed which consists of a thin sheet coated on one side with fissionable material, so that nuclear power is converted directly into propulsive power. Thrust is available both from ejected fission fragments and from thermal radiation. Optimum thicknesses are determined for the active and substrate layers. This concept is shown to have potential mission capability (in terms of velocity increments) superior to that of all other advanced propulsion concepts for which performance estimates are available. A suitable spontaneously fissioning material such as Cf-254 could provide an extremely high-performance first stage beyond earth orbit. In contrast with some other advanced nuclear propulsion concepts, there is no minimum size below which this concept is infeasible.

Moeckel, W. E.↗
NASA NTRS1977

The Apollo 17 'melt sheet' - Chemistry, age and Rb/Sr systematics

Major, minor, and trace-element compositions, age data, and Rb/Sr systematics of Apollo 17 boulders have been compiled, and additional analyses performed on a norite breccia clast (77215) included in the Apollo 17, Station 7 boulder. The Apollo 17 boulders are found to be identical or nearly so in major, minor, and trace-element composition, suggesting that they all originated as an impact melt analogous to melt sheets found in larger terrestrial craters. The matrix dates (Ar-40/Ar-39) and Rb/Sr systematics available suggest that this impact melt formed by a single impact about 4 billion years ago. This impact excavated, shocked, brecciated, and melted norites, norite cumulates, and possibly anorthositic gabbros and dunites about 4.4 billion years old. The impact was likely a major one, possibly the Serenitatis basin-forming event.

Winzer, S. R.↗
NASA NTRS1979

Analysis of cracked orthotropic sheets

Computer program performs two dimensional elastostatic analysis of plane anisotropic homogeneous sheets with through-the-thickness cracks and temperature gradients.

Aberson, J. A.↗
NASA NTRS1979

Process for growing thin polished silicon sheets

Single-crystal sheets pulled from polten silicon floating on refractory melt require no slicing or polishing. Possible materials are chlorides and fluorides of barium, calcium, and strontium. Refractory melt may be able to absorb impurities from silicon and thus obviate postgrowth purification.

Radics, C. C.↗
NASA NTRS1977

Assessment of present state-of-the-art sawing technology of large diameter ingots for solar sheet material

The objective of this program is to assess the present state-of-the-art sawing technology of large diameter silicon ingots (3 inch and 4 inch diameter) for solar sheet materials. During this period, work has progressed in three areas: (1) slicing of the ingots with the multiblade slurry saw and the I.D. saw, (2) characterization of the sliced wafers, and (3) analysis of direct labor, expendable material costs, and wafer productivity.

Yoo, H. I.↗
NASA NTRS1976

Some observations on the characteristics of low-cost silicon sheets

To meet the need for low cost silicon sheet material in the ERDA/JPL photovoltaics program, JPL has initiated a wide ranging technology development effort in crystal growth that includes several different technology thrusts. They range in scope from innovative ingot growth and multislice wafering, to shaped growth techniques, substrate-related processes and hot forming techniques. In this paper, some salient observations on materials resulting from these processes are reported. Included are multiblade wafering-induced damage studies, interface morphology studies on the heat exchanger cast silicon, some diffusion length measurements in thin silicon layers on ceramic substrates, and results on the equilibrium structure found in laser zone ribbon growth.

Digges, T. G., Jr.↗
NASA NTRS1976

Dip-coated sheet silicon solar cells

A cost-effective method is being developed for producing solar cell quality sheet silicon by dip coating inexpensive ceramic substrates with a thin layer of large grain silicon. Mullite (Aluminum Silicate) ceramic substrates coated with a thin layer of graphite have been dipped into molten silicon to produce 20-150 micron thick layers having grain sizes as large as .4 cm x 4 cm. With these silicon layers photovoltaic diodes have been fabricated with measured and inherent conversion efficiencies of 4% and 7%, respectively.

Heaps, J. D.↗
NASA NTRS1976

Integral glass sheet encapsulation for terrestrial panel applications

Concepts for integral glass sheet encapsulation of terrestrial solar cell modules using techniques based upon electrostatic bonding are being developed. It is possible for the glass to provide hermetic encapsulation, the structural support, and a vehicle for integral interconnection of the solar cells. Anticipated capabilities, present status, and cost projections for large scale terrestrial utilization are discussed.

Minnucci, J. A.↗
NASA NTRS1978

The thermal history of the Manicouagan impact melt sheet, Quebec

Calculations for the heat transfer between superheated silicate melt and evenly dispersed 1-mm cold clasts indicate that most of the thermal gradients are smoothed out in 100 s and that the rate of equilibrium is sufficiently high so that clasts whose dissolution in the melt is slow may be preserved. The calculations also show the extent to which cold debris and clasts are melted. Calculations for cooling of the 200-m-thick melt sheet at Manicouagan suggest that complete crystallization takes 35 years at 10 m from the edge and 1600 years at the center.

Onorato, P. I. K.↗
NASA NTRS1979

Room-temperature bonding of thin plastic sheets

Thin sheets of plastic are bonded together, without heat, by depositing metal films on plastic and applying light pressure. Films are pressed together at room temperature, technique which makes it possible to join organic material without high temperatures necessary for conventional adhesive bonding.

Frazer, R. E.↗
NASA NTRS1979

Anti-reflection Coatings on Large Area Glass Sheets

The first quarter of a one-year program designed to research and perfect a method of producing antireflective coatings on large glass sheets through the use of sodium silicate hardened by exposure to acid is reported. The requirements for a linear motion device used to produce uniform sodium silicate films were determined. A search for a commercially available device is underway. Sodium silicate solutions of varying concentrations were prepared. Determinations of the physical properties relevant to film thickness are in progress. In addition, material costs are being recorded for later use in a cost analysis of the method. All tasks of the project are proceeding according to schedule. Of the tasks, only the sodium silicate solution preparation is complete.

Pastirik, E.↗
NASA NTRS1979

LSA Large Area Silicon Sheet Task Continuous Czochralski Process Development

A commercial Czochralski crystal growing furnace was converted to a continuous growth facility by installation of a small, in-situ premelter with attendant silicon storage and transport mechanisms. Using a vertical, cylindrical graphite heater containing a small fused quartz test tube linear from which the molten silicon flowed out the bottom, approximately 83 cm of nominal 5 cm diamter crystal was grown with continuous melt addition furnished by the test tube premelter. High perfection crystal was not obtained, however, due primarily to particulate contamination of the melt. A major contributor to the particulate problem was severe silicon oxide buildup on the premelter which would ultimately drop into the primary melt. Elimination of this oxide buildup will require extensive study and experimentation and the ultimate success of continuous Czochralski depends on a successful solution to this problem. Economically, the continuous Czochralski meets near-term cost goals for silicon sheet material.

Rea, S. N.↗
NASA NTRS1979

Vacuum Die Casting of Silicon Sheet for Photovoltaic Applications

The development of a vacuum die-casting process for producing silicon sheet suitable for photovoltaic cells with a terrestrial efficiency greater than 12 percent and having the potential to be scaled for large quantity production is considered. The initial approach includes: (1) obtaining mechanical design parameters by using boron nitride, which has been shown to non-wetting to silicon; (2) optimizing silicon nitride material composition and coatings by sessile drop experiments; (3) testing effectiveness of fluoride salt interfacial media with a graphite mold; and (4) testing the effect of surface finish using both boron nitride and graphite. When the material and mechanical boundary conditions are established, a finalized version of the prototype assembly will be constructed and the casting variables determined.

Source record↗
NASA NTRS1979

Plasma in the Jovian current sheet

A large body of spectral data for protons with energies greater than 200 keV has been analyzed. It is concluded that the main body of plasma in the Jovian current sheet observed by Pioneer 10 on its outbound pass probably has an energy well below the lowest threshold of the Pioneer 10 detectors. This premise is examined using a semiempirical model of the magnetic field in the magnetodisk and simple magnetohydrodynamic theory. Results indicate that the dominant contribution to the plasma pressure in the region from 25 to 65 Jovian radii is from as yet unobserved protons (ions) with energies of the order of 0.1 to 10 keV.

Goertz, C. K.↗
NASA NTRS1979

Particle boundary structures at the magnetopause and the plasma sheet

There are three classes of particle events in the vicinity of the magnetopause: a layer of particles right at the magnetopause which we identify with the boundary layer particles; spikes of particles just ahead of the magnetopause; and, sometimes, magnetosheath-like ions appearing inside the magnetosphere, the inclusion events. The energy spectra of these three classes of events are very similar, indicating a common particle source. The presence of a particle layer at the outer boundary of the plasma sheet is shown. This layer has typical dimensions of a few thousand km at 20 Earth radii. A typical velocity is a few tens of km/sec. These velocities and dimensions projected to ionospheric heights resemble those of visual auroras and suggest that aurorally associated particle phenomena are being detected.

Parks, G. K.↗