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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 1,801 records · Page 100
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

A finite element procedure for nonlinear prebuckling and initial postbuckling analysis

A procedure cast in a form appropriate to the finite element method is presented for geometrically nonlinear prebuckling and postbuckling structural analysis, including the identification of snap-through type of buckling. The principal features of this procedure are the use of direct iteration for solution of the nonlinear algebraic equations in the prebuckling range, an interpolation scheme for determination of the initial bifurcation point, a perturbation method in definition of the load-displacement behavior through the postbuckling regime, and extrapolation in determination of the limit point for snap-through buckling. Three numerical examples are presented in illustration of the procedure and in comparison with alternative approaches.

Mau, S. T.↗
NASA NTRS1971

Development and applications of Fluorel

The development of a nonflammable elastomer for use in Apollo spacecraft is discussed. The requirements for the material to be foamed, extruded, compression molded, and cast into various configurations are examined. A fluorine-based hydrocarbon is considered a promising candidate. An acceptable material known as Fluorel is examined. Procedures for applying fluorel to a flood light glare shield are presented. The process for preparing 20 percent homogenized Fluorel is analyzed.

Supkis, D. E.↗
NASA NTRS1972

Metallurgy: A compilation

A compilation on the technical uses of various metallurgical processes is presented. Descriptions are given of the mechanical properties of various alloys, ranging from TAZ-813 at 2200 F to investment cast alloy 718 at -320 F. Methods are also described for analyzing some of the constituents of various alloys from optical properties of carbide precipitates in Rene 41 to X-ray spectrographic analysis of the manganese content of high chromium steels.

Source record↗
NASA NTRS1972

Oxidation and thermal fatigue of coated and uncoated NX-188 nickel-base alloy in a high velocity gas stream

A cast nickel-base superalloy, NX-188, coated and uncoated, was tested in a high-velocity gas stream for resistance to oxidation and thermal fatigue by cycling between room temperature and 980, 1040, and 1090 C. Contrary to the behavior of more conventional nickel-base alloys, uncoated NX-188 exhibited the greatest weight loss at the lowest test temperature. In general, on the basis of weight change and metallographic observations a coating consisting of vapor-deposited Fe-Cr-Al-Y over a chromized substrate exhibited the best overall performance in resistance to oxidation and thermal fatigue.

Johnson, J. R.↗
NASA NTRS1971

Development of a collapsible reinforced cylindrical space observation window

Existing material technology was applied to the development of a collapsible transparent window suitable for manned spacecraft structures. The effort reported encompasses the evaluation of flame retardants intended for use in the window matrix polymer, evaluation of reinforcement angle which would allow for a twisting pantographing motion as the cylindrical window is mechanically collapsed upon itself, and evaluation of several reinforcement embedment methods. A fabrication technique was developed to produce a reinforced cylindrical space window of 45.7 cm diameter and 61.0 cm length. The basic technique involved the application of a clear film on a male-section mold; winding axial and girth reinforcements and vacuum casting the outer layer. The high-strength transparent window composite consisted of a polyether urethane matrix reinforced with an orthogonal pattern of black-coated carbon steel wire cable. A thin film of RTV silicone rubber was applied to both surfaces of the urethane. The flexibility, retraction system, and installation system are described.

Khan, A. Q.↗
NASA NTRS1970

Remote sensing of changes in morphology and physiology of trees under stress

Results of continuing studies of forest trees subjected to varying types of stress are reported. Both greenhouse and field studies are included. Greenhouse work with tree seedlings exposed to varying levels of NaCl and CaCl2 in the soil indicated that, in the initial stages, palisade cells shrink and the amount of air space in the leaf increases. As the severity of damage increases, the cells of the spongy mesophyll shrink and flatten, and the amount of air space in the leaf decreases. Statistical analysis of foliar reflectance and associated moisture content data led to a series of regression equations for predicting foliar moisture content from reflectance data. Equations were calculated for three species, yellow birch (Betula alleghaniensis Britton), sugar maple (Acer saccharum Marsh.) and white ash (Fraxinus americana L.) having multiple correlation coefficients of 0.98, 0.94 and 0.93 respectively. Interpretation of multispectral imagery of the Ann Arbor Forestry Test Site (NASA Site 190) provided evidence that infections of Fomes annosus can be detected in the early stages. Infections of two needle cast diseases were also detected in conifer plantations in the test site. A study of automatic interpretation of multispectral scanner imagery for tree species recognition provided encouraging results.

Olson, C. E., Jr.↗
NASA NTRS1972

Apollo 14 mission report. Supplement 7: Inflight demonstrations

Experiments performed on board the Apollo 14 are reviewed. These include a liquid transfer demonstration during the transearth coast, electrophoresis separation, a composite casting demonstration, and a heat flow and convection demonstration.

Source record↗
NASA NTRS1971

Solid propellant processing factor in rocket motor design

The ways are described by which propellant processing is affected by choices made in designing rocket engines. Tradeoff studies, design proof or scaleup studies, and special design features are presented that are required to obtain high product quality, and optimum processing costs. Processing is considered to include the operational steps involved with the lining and preparation of the motor case for the grain; the procurement of propellant raw materials; and propellant mixing, casting or extrusion, curing, machining, and finishing. The design criteria, recommended practices, and propellant formulations are included.

Source record↗
NASA NTRS1972

Properties of materials in high pressure hydrogen at room and elevated temperatures

Experimental efforts in this program for this period. Mechanical property tests of wrought and cast nickel-base alloys and one wrought cobalt-base alloy were conducted in 34.5 MN/sq m (5000-psig) helium and hydrogen or hydrogen mixtures. Comparison of test results was made to determine degradation of properties due to the hydrogen environments. All testing was conducted on solid specimens exposed to external gaseous pressure. Specific mechanical properties determined and the testing methods used are summarized.

Harris, J. A., Jr.↗
NASA NTRS1972

Determination of solid-propellant transient regression rates using a microwave Doppler shift technique

A microwave Doppler shift system, with increased resolution over earlier microwave techniques, was developed for the purpose of measuring the regression rates of solid propellants during rapid pressure transients. A continuous microwave beam is transmitted to the base of a burning propellant sample cast in a metal waveguide tube. A portion of the wave is reflected from the regressing propellant-flame zone interface. The phase angle difference between the incident and reflected signals and its time differential are continuously measured using a high resolution microwave network analyzer and related instrumentation. The apparent propellant regression rate is directly proportional to this latter differential measurement. Experiments were conducted to verify the (1) spatial and time resolution of the system, (2) effect of propellant surface irregularities and compressibility on the measurements, and (3) accuracy of the system for quasi-steady-state regression rate measurements. The microwave system was also used in two different transient combustion experiments: in a rapid depressurization bomb, and in the high-frequency acoustic pressure environment of a T-burner.

Strand, L. D.↗
NASA NTRS1971

Formulation of boundary integral equations for three-dimensional elasto-plastic flow.

A general theory of elastoplastic flow is formulated for work-hardening materials that may be both anisotropic and compressible. Because the theory is quasi-linear, it may be cast in terms of integral equations and the result is an extended form of Somigliana's identity. When these relations are evaluated on the boundary of a solid, their dimensionality is reduced. Previous experience with simpler materials shows that arbitrary problems may be solved in a direct manner.

Swedlow, J. L.↗
NASA NTRS1971

An investigation of oxidation-resistant solid lubricant materials.

Recent research at NASA-Lewis on solid lubricants for use at high temperatures in air and other gaseous environments is presented. The characteristics of oxide and fluoride lubricants at temperatures to 1700 F are described. Data is presented for fluoride coatings with silicate and other additives incorporated to give improved wear life and better oxidation protection to the substrate metal. Experience is described for fluoride-metal self-lubricating composites with improved metal oxidation resistance to 1700 F. The concept of cast, self-lubricating ceramics is also explored.

Sliney, H. E.↗
NASA NTRS1971

The attenuation of Love waves and toroidal oscillations of the earth.

An attempt has been made to invert a large set of attenuation data for Love waves and toroidal oscillations in the earth, using a recent method by Backus and Gilbert. The difficulty in finding an acceptable model of internal friction which explains the data, under the assumption that the internal friction is independent of frequency, casts doubt on the validity of this assumption. A frequency-dependent model of internal friction is presented which is in good agreement with the seismic data and with recent experimental measurements of attenuation in rocks.

Jackson, D. D.↗
NASA NTRS1971

Development of a full-length external-fuel thermionic converter for in-pile testing.

Description of an external-fuel thermionic converter which utilizes a thoriated-tungsten fuel-emitter body. Performance in out-of-pile tests was comparable to that of an arc-cast tungsten emitter body, with 400-eW output power (about 5 W/sq cm) at 10.8% efficiency. Maximum fuel clad temperature averaged from 1650 to 1700 C during the 300-hour test. This converter has been processed for in-pile testing. The various processing steps, including the installation of six emitter thermocouples, encapsulation in the secondary container, and joining to the fission-gas collection system, are described in detail. In addition to the converter assembly, a doubly contained fission gas collection assembly with radiation-hardened differential pressure transducers was fabricated. The experiment support plate required for the in-pile test, containing electrically insulated instrumentation feedthroughs and coolant line feedthroughs to the vacuum test chamber, was also fabricated.

Schock, A.↗
NASA NTRS1972

N2 positive and N2/+/ band systems and the energy spectra of auroral electrons.

Use of the relative emission rates of the auroral N2 positive and N2(+) band systems to limit the permissible range of differential electron fluxes in auroras, due to remarkable differences in electron excitation functions for the two kinds of systems. Use of recently measured electron cross sections and many observational data from ground based and rocket studies shows that the results are consistent with spectra equivalent to a power law E to the minus 1.4 power for primaries and secondaries combined. The unified primary spectra of Rees (1969) and secondary spectra of Rees et al. (1969) fail seriously to predict the optical ratios. It is shown that Rees' primary spectrum is deficient in slow primaries, owing to the use of defective Monte Carlo results of Maeda (1965). Doubt is thereby cast on the validity of experimental results for the differential spectrum below 50 eV reported by Feldman et al. (1971) because of the rapid decrease in flux with energy shown by those measurements.

Shemansky, D. E.↗
NASA NTRS1972

The radiative transfer equation and environmental effects in the upper atmosphere.

A highly effective approach to the solution of the radiative transfer equation, including the effects of emission, absorption, and multiply scattered radiation, is described. The transfer equation is cast in its unsteady hyperbolic form which is amenable to several different numerical methods of solution. Comparisons of solutions with emission, absorption, and scattering of radiation, are presented to demonstrate the validity of the present approach.

Callis, L. B.↗
NASA NTRS1972

New space processing experiments for the Skylab missions.

The M512 Materials Processing Facility, which is the main item of equipment for the Skylab space manufacturing experiments is described. It is basically an electron-beam welding apparatus, consisting of a battery power supply, a 20-kV electron beam source, and a spherical 40-cm-diam vacuum chamber. It will be used to perform the M551 Metals Melting Experiment, the M552 Exothermic Brazing Experiment, the M553 Sphere Forming Experiment, the M554 Composite Casting Experiment, the M555 Gallium Arsenide Crystal Growth Experiment, the M561 Whisker-Reinforced Composites Experiment, the M562 Indium Antimonide Crystal Growth, Experiment, the M563 Mixed III-V Crystal Growth Experiment, the M564 Alkali Halide Eutectics Experiment, the M565 Silver Grids Melted in Space Experiment, and the M566 Copper-Aluminum Eutectic Experiment. Three apparatus systems designed to broaden the technical scope of the experiments and to gain experience with new experimental techniques are described. These are an electrophoretic separator, an electromagnetic levitation system, and a versatile electric furnace with an electronic control system.

Bredt, J. H.↗

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