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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 1,351 records · Page 75
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Meteorites and the Antarctic ice sheet

The majority of the meteorite finds were located in the Allan Hills site. All the expected goals involving the recovery of rare or previously unknown types of meteorites, and even the recovery of lunar ejecta, were realized. The relationship between these remarkable concentrations of meteorites and the Antarctic ice sheet itself were less well documented. Ice flow vector studies were made and concentration models were proposed. Earlier estimates of the abundances of meteorite types were based on the number of falls in the world collections. The accumulated data and the future collected data will allow more reliable estimates of the source region of most meteorites.

Cassidy, W. A.↗
NASA NTRS1985

Advanced silicon sheet

The session chairman's overview of ten presentations made covering research on silicon-shaped sheet technology is presented.

Briglio, A., Jr.↗
NASA NTRS1985

Electrical, structural, and chemical characterization of silicon sheet materials

Progress on the electrical, structural, and chemical characterization of silicon sheet material is reported. In the study on high temperature deformation of dendritic web ribbon, experimental creep tests were performed in four point bending under constant load conditions, and unusual behavior was observed. Also, measurements of oxygen content in web ribbon were made. Two conclusions reached are creep behavior of web which is very different from any seen for single crystal silicon and oxygen level in web silicon which is near the saturation level at the melting point of silicon.

Ast, D. G.↗
NASA NTRS1985

Analysis of high-speed growth of silicon sheet in inclined-meniscus configuration

The study of high speed growth of silicon sheet in inclined-meniscus configurations is discussed. It was concluded that the maximum growth rates in vertical and inclined growth are set by thermal-capillary limits. Also, the melt/crystal interface was determined to be flat. And, vertical growth is qualitatively modelled by one dimensional heat transfer.

Thomas, P. D.↗
NASA NTRS1985

Silicon sheet surface studies

Results of the program are presented on developing an understanding of the basic mechanisms of abrasion and wear of silicon and on the nondestructive measurement of residual stresses in sheet silicon. Experiments were conducted at various temperatures and in the presence of various fluids. In abrasive wear, it was shown that dislocations, microtwins, and cracks are generated beneath the contact surface. Residual stresses in ribbon by the edge defined film growth process were measured by use of a shadow moire interferometry technique.

Danyluk, S.↗
NASA NTRS1985

Subsystem fact sheets for NASA CO2 Project, revision 3

The twenty-seven subsystem fact sheets produced by Ball Aerospace Systems Division are presented. Each instrument is summarized with a description; physical characteristics; data; orbit requirements; sensor; implementation schedule; and experience, problems, modifications.

Lookabaugh, T.↗
NASA NTRS1985

Observations of the right-hand resonant ion beam instability in the distant plasma sheet boundary layer

Examples of the onset of a resonant ion beam instability are illustrated on the basis of ISEE 3 observations of 66 large amplitude wave events at the plasma sheet boundary layer. Analysis of the observational data showed that the observed wave and ion beam parameters were, in general, in agreement with linear theoretical predictions of resonant ion beam instability. The distribution of ion energies at the onset of the instability is given in a table.

Tsurutani, B. T.↗
NASA NTRS1986

Energetic particle beams in the plasma sheet boundary layer following substorm expansion - Simultaneous near-earth and distant tail observations

Simultaneous observations of ions and electron beams in the near-earth and deep magnetotail following the onset of substorm are analyzed in terms of the substorm neutral line model. The observations were collected on March 20, 1983 with ISSE 1 and 3. Energy fluxes and intensity-time profiles of protons and electrons are studied. The data reveal that the reconnection at the near-earth neutral line produces ions and electrons for the plasma sheet boundary layer. The maximum electric potential along the neutral line is evaluated.

Scholer, M.↗
NASA NTRS1986

The use of curved higher order panels for vortex sheet modeling

A method is presented for predicting the geometry of a vortex sheet trailing a lift generating wing in its vicinity. It differs from others in that it uses a continuous vorticity distribution rather than discrete vortex filaments. It was found that the results were in good agreement with available experimental data, after the initial cycle of what was to be a relaxation scheme, so that iterations for this end were unnecessary. While the technique is computing intensive, it becomes attractive when used in conjunction with panel methods applications for complete aircraft configurations. The panel method solution needs to be found only once for each streamwise station downstream of the wing. Corrections applied are geometric in nature and are independent of other computational aspects.

Nagati, M. G.↗
NASA NTRS1986

Calculation of asymmetric vortex separation on slender delta wings with a vortex-sheet model

An inviscid vortex-sheet model based on the slender wing theory is developed to examine asymmetric vortex separation at zero sideslip on delta wings. It is found that multiple asymmetric vortex configurations exist at a given angle of attack. Available data on rolling moment measurements and flow visualization are used for correlation to prove the concept.

Lan, C. E.↗
NASA NTRS1987

Making Ceramic Parts by Laminating and Sintering Thin Sheets

Chemical composition varies as function of depth. Technique developed to fabricate monolithic ceramic component by sintering laminated body made from thin sheets of green ceramic. Method allows discrete changes in chemistry effected across monolith. Component having one-dimensional variation in material composition fabricated in this manner.

Cawley, J. D.↗
NASA NTRS1986

Geological-morphological description of the Ishtar Terra (photomap of the Venusian surface sheet B-5)

The main part of the Ishtar Terra east of the Maxwell Montes is covered with systems of areal dislocations of several directions, which are called Parquet. According to the structural patterns these may be divided into: (1) the central stable block; (2) the lesser peripheral blocks separated from the central one by gaps and grabens; (3) the zones of mobilized parquet, whose substance flowed downward at an incline in the directions away from the central block in the form of plastic flows; and (4) the partially parqueted lava sheets. The Maxwell Montes were formed as a result of the collision between the central parquet block and the Lakshmi Planum.

Sukhanov, A. L.↗
NASA NTRS1986

Technical progress in silicon sheet growth under DOE/JPL FSA program, 1975-1986

The technical progress made in the Silicon Sheet Growth Program during its 11 years was reviewed. At present, in 1986, only two of the original 9 techniques have survived to the start-up, pilot-plant stage in industry. These two techniques are the edge-defined, film-fed growth (EFG) technique that produces closed shape polygons, and the WEB dendritic technique that produces single ribbons. Both the status and future concerns of the EFG and WEB techniques were discussed.

Kalejs, J. P.↗
NASA NTRS1987

Material characterization of superplastically formed titanium (Ti-6Al-2Sn-4Zr-2Mo) sheet

The aerospace industry has focused considerable interest on the near-alpha titanium alloy Ti-6Al-2Sn-4Zr-2Mo (Ti-6242) because of both its high-temperature properties and its superplastic forming (SPF) capabilities. This paper describes current research to characterize selected mechanical properties of Ti-6242 sheet in the SPF-strained condition, both with and without heat treatment, and compares the results with those obtained on as-received material. Tensile and creep tests were conducted, and metallographic analysis was performed to show the effect of 100 to 700 percent SPF strain on titanium properties. Analysis shows that as a result of SPF processing, both tensile and yield strengths, as well as elongation, are moderately reduced. Creep tests at 800 F and 1000 F show that the SPF processed material displays superior creep resistance compared with the as-received material. A post-SPF duplex-anneal heat treatment had no beneficial effect on tensile and creep properties.

Ossa, William A.↗
NASA NTRS1987

Shuttle Ground Operations Efficiencies/Technologies Study (SGOE/T). Volume 5: Technical Information Sheets (TIS)

The Technology Information Sheet was assembled in database format during Phase I. This document was designed to provide a repository for information pertaining to 144 Operations and Maintenance Instructions (OMI) controlled operations in the Orbiter Processing Facility (OPF), Vehicle Assembly Building (VAB), and PAD. It provides a way to accumulate information about required crew sizes, operations task time duration (serial and/or parallel), special Ground Support Equipment (GSE). required, and identification of a potential application of existing technology or the need for the development of a new technolgoy item.

Scholz, A. L.↗
NASA NTRS1986

A numerical method for vortex sheet roll-up

The problem of computing vortex sheet roll-up from periodic analytic initial data is studied. Previous theoretical and numerical work is reviewed. Computational difficulties arising from ill posedness and singularity formation are discussed. A desingularization method is proposed to diminish these difficulties. Computations indicate that this approach converges past the time at which previous numerical investigations have failed to converge.

Krasny, R.↗
NASA NTRS1986

Three-dimensional structure of the heliospheric current sheet

Using a modification of the kinematic method of Hakamada and Akasofu (1982), those solar wind streams which originate near the magnetic neutral line on the source surface are followed to map the three-dimensional structure of the heliospheric current sheet (HCS) out to 5 AU for several Carrington rotations. The Stanford potential analysis magnetic field information of Hoeksema et al. (1983) is used to specify the source surface field.

Fry, C. D.↗
NASA NTRS1986

Evidence for a latitudinal gradient of the cosmic ray intensity associated with a change in the tilt of the heliospheric current sheet

Since mid-1985, the average flux of greater than 70 MeV/nucleon cosmic rays at Voyager 2 (r2 = 17 AU, theta 2 approximately equals 0 deg) has been about 3-5 percent greater than that at Voyager 1 (r1 = 24 AU, theta 1 = 26 deg N). This is the first direct observation over such a large radial range in which the galactic cosmic ray flux closer to the sun is higher than the flux farther from the sun for an extended period of time. This observation is consistent with the presence of a negative latitudinal gradient of -0.36 + or 0.05 (or -0.60 + or - 0.08) percent/deg, assuming a coexistent radial gradient of 1 (or 2) percent/AU. It is suggested that the appearance of this persistent negative latitudinal gradient may be due to the abrupt, large decrease of the heliospheric current sheet tilt to about 20 deg in early 1985.

Christon, S. P.↗