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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 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Retort braze bonding of borsic/aluminum composite sheet to titanium

Braze bonding studies between Borsic/aluminum composite and titanium sheet were conducted to establish acceptable brazing techniques and to assess potential joint efficiencies. Excellent braze joints were produced which exhibited joint strengths exceeding 117 MPa (17,000 psi) and which retained up to 2/3 of this strength at 589 K (600 F). Noticeable composite strength degradation resulting from the required high temperature braze cycle was found to be a problem.

Webb, B. A.↗
NASA NTRS1976

Finite element computer program to analyze cracked orthotropic sheets

A two dimensional orthotropic sheet with through-the-thickness cracks and temperature gradient was analyzed. The program includes special crack tip elements that account for singular stress fields associated with crack opening and crack sliding displacements at the crack tip. The program also includes a linear spring element and a constant strain, triangular element. A number of problems for which closed form solutions exist were analyzed to demonstrate the capabilities of the program.

Chu, C. S.↗
NASA NTRS1976

Several intact or broken stringers attached to an orthotropic sheet with a crack

Several intact or broken stringers which are continuously attached to a cracked orthotropic sheet through an adhesive are considered. The effect of orthotropy on the stress intensity factors is investigated. The stringers are assumed to be partially debonded due to high stress concentrations. The shear stress distribution between the stringers and the plate and the stress intensity factors are obtained from an integral equation which represents the continuity of displacements along the bond lines.

Arin, K.↗
NASA NTRS1975

Magnetospheric protons and electrons encountered by the moon in the plasma sheet

Results are summarized for a study of plasma-sheet particles (and their flow) encountered by the moon during its passage through the geomagnetic tail. The study is based on analysis of data obtained with a modulated Faraday cup on board the lunar-anchored spacecraft Explorer 35. It is shown that the electrons have a rapidly fluctuating non-Maxwellian energy distribution with a mean energy of several hundred electron volts and a density of approximately 0.2 per cu cm. Protons with energies of the order of 1 keV were usually detected above the instrument background when flowing towards earth at about 200 km/sec. It is suggested that strong terrestrial polar winds during the early history of the earth-moon system could have caused some erosion of the front side of the moon and that the relative smoothness of the same side could be explained in terms of gravitational shielding by the earth from the interplanetary rock flux.

Prakash, A.↗
NASA NTRS1976

Interactions of the plasma sheet with the lunar surface at the Apollo 14 site

Calculations of the magnetic shadow zones of lunar-based particle detectors are extended to include the effects of local remanent magnetic fields. At the Apollo 14 site, the local magnetic field is approximated as that of a dipole. Numerically calculated open and shadowed zones are shown to be in agreement with quiet-time plasma-sheet observations of the charged-particle lunar-environment experiment. An analysis of three storm-time observations indicates that magnetic shadowing can significantly alter the near-lunar-surface electrostatic potential distribution.

Reiff, P. H.↗
NASA NTRS1977

Inexpensive silicon sheets for solar cells

Technique of producing silicon sheets by drawing gridlike or porous graphite gauze through silicon melt is readily adaptable to mass production, making process applicable to inexpensive manufacture of solar cell arrays.

Ciszek, T. F.↗
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 Cf254 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 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.↗