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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

The petrology of the Apollo 12 ilmenite basalt suite

Mineral chemistry data and petrographic interpretations as well as fractionation modeling determined independently indicate that the bulk chemical variations in the ilmenite suite can be reconciled with differentiation within a single cooling unit. Olivine porphyritic basalts, medium-grained basalts with evolved compositions, and coarse-grained olivine cumulates are found in the suite. It is suggested that most of the chemical variation within the suite could result from fractionation of olivine equivalent to the composition of phenocrysts in vitrophyre 12008 which serves well as a parental magma for the other textural-chemical variants. The relative cooling rate sequence within all three textural-chemical subgroups was determined, and systematic correlations between the degree of olivine addition or subtraction and the relative cooling rate is indicated.

Dungan, M. A.↗
NASA NTRS1978

Hypervelocity impact tests on Space Shuttle Orbiter RCC thermal protection material

It is noted that the Shuttle Orbiter will be more subject to meteoroid impact than previous spacecraft, due to its greater surface area and longer cumulative time in space. The Orbiter structural material, RCC, a reinforced carbon-carbon laminate with a diffused silicon carbide coating, is evaluated in terms of its resistance to hypervelocity impact. It was found that the specimens (disks with a mass of 34 g and a thickness of 5.0 mm) were cratered only on the front surface when the impact energy was 3 J or less. At 3 J, a trace of the black carbon interior was exposed. The specimens were completely penetrated when the energy was 34 J or greater.

Humes, D. H.↗
NASA NTRS1975

Shock-induced subsolidus reduction-decomposition of orthopyroxene and shock-induced melting in norite 78235

Lunar rock 78235 is a coarse-grained igneous rock which was chipped from the top of a boulder about 1/2 m in size at Station 8 at the base of the Sculptured Hills, Taurus-Littrow Valley. The rock is a shocked coarse-grained norite with a relict subophitic texture; it is composed of about equal proportions of chromian bronzite and anorthite. Evidence is presented for the shock history of the rock. It is concluded that 78235 is a deep-seated norite of cumulate origin which has been intensely shocked. Although it may be possible to account for the observed shock-induced features by invoking a single shock event, the evidence is best explained by a history which includes at least two discrete shock events. In the first identifiable shock event much of the plagioclase was transformed to maskelynite and the associated bronzite was deformed and acquired a mosaic structure. In a later shock event, localized melting of both plagioclase pyroxene occurred.

Sclar, C. B.↗
NASA NTRS1975

Agglutinates as indicators of lunar soil maturity - The rare gas evidence at Apollo 16

The weight percent of lunar agglutinic glass (glass-welded aggregates resulting from micrometeorite impacts) in Apollo 16 bulk soils is considered with respect to quantities of trapped rare gases, e.g., He-4, Ne-20, Ar-36, Kr-84, and Xe-132, in an effort to determine the cumulative time a given soil sample has spent exposed on the lunar surface. The agglutinic glass, which reacts strongly in a magnetic field, is obtained by the standard fluid (methanol)-magnetic technique. It is noted that the absolute concentrations of trapped rare gases all show a linear relationship with increasing agglutinic glass content.

Charette, M. P.↗
NASA NTRS1975

Some correlation of rock exposure ages and regolith dynamics

Exposure age information on lunar rocks and regolith turnover rates are correlated. If plotted in a cumulative fashion, the distribution of spallogenic noble-gas exposure ages is remarkably parallel to the rate at which various fractions of the regolith surface are cratered and/or excavated. It appears that the rate at which lunar rocks are excavated from within the regolith is strongly controlled by the impact environment. Some suggestions for future refinement of regolith dynamics are presented.

Horz, F.↗
NASA NTRS1978

Plant canopy light absorption model with application to wheat

A light absorption model (LAM) for vegetative plant canopies has been derived from the Suits reflectance model. From the LAM the absorption of light in the photosynthetically active region of the spectrum (400-700 nm) has been calculated for a Penjamo wheat crop for several situations including (a) the percent absorption of the incident radiation by a canopy of LAI 3.1 having a four-layer structure, (b) the percent absorption of light by the individual layers within a four-layer canopy and by the underlying soil, (c) the percent absorption of light by each vegetative canopy layer for variable sun angle, and (d) the cumulative solar energy absorbed by the developing wheat canopy as it progresses from a single layer through its growth stages to a three-layer canopy. This calculation is also presented as a function of the leaf area index and is shown to be in agreement with experimental data reported by Kanemasu on Plainsman V wheat.

Chance, J. E.↗
NASA NTRS1980

JANTX1N649-1 diode

Samples mamufactured by Semtech and Micro Semiconductor were tested. Both lots did quite well in tests. Plot showing cumulative failure distribution for group 2 was drawn for both lots. Graphs for groups 1 and 3 failures could not be drawn because of extremely low occurence.

Source record↗
NASA NTRS1979

Structural analysis of cylindrical thrust chambers, volume 1

Life predictions of regeneratively cooled rocket thrust chambers are normally derived from classical material fatigue principles. The failures observed in experimental thrust chambers do not appear to be due entirely to material fatigue. The chamber coolant walls in the failed areas exhibit progressive bulging and thinning during cyclic firings until the wall stress finally exceeds the material rupture stress and failure occurs. A preliminary analysis of an oxygen free high conductivity (OFHC) copper cylindrical thrust chamber demonstrated that the inclusion of cumulative cyclic plastic effects enables the observed coolant wall thinout to be predicted. The thinout curve constructed from the referent analysis of 10 firing cycles was extrapolated from the tenth cycle to the 200th cycle. The preliminary OFHC copper chamber 10-cycle analysis was extended so that the extrapolated thinout curve could be established by performing cyclic analysis of deformed configurations at 100 and 200 cycles. Thus the original range of extrapolation was reduced and the thinout curve was adjusted by using calculated thinout rates at 100 and 100 cycles. An analysis of the same underformed chamber model constructed of half-hard Amzirc to study the effect of material properties on the thinout curve is included.

Armstrong, W. H.↗
NASA NTRS1978

Hydrogen energy. A bibliography with abstracts

Hydrogen Energy is a continuing bibliographic summary with abstracts of research and projections on the subject of hydrogen as a secondary fuel and as an energy carrier. This update to Hydrogen Energy cites additional references identified during the fourth quarter of 1978. It is the fourth in a 1978 quarterly series intended to provide current awareness to those interested in hydrogen energy. A series of cross indexes are included which track directly with those of the cumulative volume.

Source record↗
NASA NTRS1974

User's instructions for the Guyton circulatory dynamics model using the Univac 1110 batch and demand processing (with graphic capabilities)

The model presents a systems analysis of a human circulatory regulation based almost entirely on experimental data and cumulative present knowledge of the many facets of the circulatory system. The model itself consists of eighteen different major systems that enter into circulatory control. These systems are grouped into sixteen distinct subprograms that are melded together to form the total model. The model develops circulatory and fluid regulation in a simultaneous manner. Thus, the effects of hormonal and autonomic control, electrolyte regulation, and excretory dynamics are all important and are all included in the model.

Archer, G. T.↗
NASA NTRS1979

Effects of truncation of a predominantly compression load spectrum on the life of a notched graphite/epoxy laminate

The fatigue behavior of a notched, graphite/epoxy (T300/5208) laminate subjected to predominantly compressive loading was explored in a series of constant-amplitude and transport wing spectrum tests. Results of these tests indicate that (1) the amount of local (near the notch) buckling allowed in the tests significantly affected fatigue life; (2) spectrum truncation of either the high- or low-load end of the spectrum produced lives greater than those obtained in the baseline, complete-spectrum test, but life was much more sensitive to truncations at the high-load end; and (3) the Palmgren-Miner linear cumulative damage theory always predicted lives much longer than the actual spectrum loading test lives.

Phillips, E. P.↗
NASA NTRS1979

Nonlinear ordinary difference equations

Future space vehicles will be relatively large and flexible, and active control will be necessary to maintain geometrical configuration. While the stresses and strains in these space vehicles are not expected to be excessively large, their cumulative effects will cause significant geometrical nonlinearities to appear in the equations of motion, in addition to the nonlinearities caused by material properties. Since the only effective tool for the analysis of such large complex structures is the digital computer, it will be necessary to gain a better understanding of the nonlinear ordinary difference equations which result from the time discretization of the semidiscrete equations of motion for such structures.

Caughey, T. K.↗
NASA NTRS1977

Implementation of wind performance studies for large antenna structures

Structural design procedures are described for a large antenna system to meet performance requirements under gravity and wind loading. A computational method is shown for the evaluation of performance in response to wind loading. Cumulative probability distribution curves for wind loading gain reductions for 100-m-diameter antennas are developed to compare a relatively heavy baseline reflector backup structure with two lighter-weight structures; all have equivalent, acceptable performance for gravity loading.

Levy, R.↗
NASA NTRS1978

An engineering approach to the prediction of fatigue behavior of unnotched/notched fiber reinforced composite laminates

An engineering approach is proposed for predicting unnotched/notched laminate fatigue behavior from basic lamina fatigue data. The fatigue analysis procedure was used to determine the laminate property (strength/stiffness) degradation as a function of fatigue cycles in uniaxial tension and in plane shear. These properties were then introduced into the failure model for a notched laminate to obtain damage growth, residual strength, and failure mode. The approach is thus essentially a combination of the cumulative damage accumulation (akin to the Miner-Palmgren hypothesis and its derivatives) and the damage growth rate (similar to the fracture mechanics approach) philosophies. An analysis/experiment correlation appears to confirm the basic postulates of material wearout and the predictability of laminate fatigue properties from lamina fatigue data.

Kulkarni, S. V.↗
NASA NTRS1979

Precipitation attenuation studies based on measurements of ATS-6 20/30-GHz beacon signals at Clarksburg, MD.

COMSAT Laboratories participated in the millimeter wavelength propagation experiment, performing measurements of the 20/30-GHz ATS-6 satellite beacon signals and auxiliary measurements such as radiometric sky temperature and minute precipitation at Clarksburg, MD. These measurements were intended to broaden the data base required to advance satellite path at frequencies over 10 GHz. A correlation is established between direct measurement of attenuation of the signal radiated from the satellite and the indirect measurement of attenuation by auxiliary ground-based equipment. The indirectly derived statistics agreed reasonably well or can be reconciled with earlier published results and may therefore be used as a basis for estimating long-term cumulative attenuation statistics.

Fang, D. J.↗
NASA NTRS1979

Higher-order skewness and excess coefficients of some probability distributions applicable to optical propagation phenomena

Expressions are derived for higher-order skewness and excess coefficients using central moments and cumulants up to 8th order. These coefficients are then calculated for three probability distributions: (1) Log-normal, (2) Rice-Nakagami, and (3) Gamma distributions. Curves are given to shown the variation of skewness with excess coefficients for these distributions. These curves are independent of the particular distribution parameters. This method is useful for studying fluctuating phenomena, which obey non-Gaussian statistics.

Majumdar, A. K.↗
NASA NTRS1979

Standard techniques for presentation and analysis of crater size-frequency data

In September 1977 a crater studies workshop was held for the purpose of developing standardized data analysis and presentation techniques. The present report contains the unanimous recommendations of the participants. Recommendations are devoted primarily to crater size-frequency data and refer to cumulative and relative size-frequency distribution plots and to morphological analysis.

Arvidson, R.↗