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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

The effect of solute additions on the steady-state creep behavior of dispersion-strengthened aluminum.

The effect of solute additions on the steady-state creep behavior of coarse-grained dispersion-strengthened aluminum alloys was studied. Recrystallized dispersion-strengthened solid solutions were found to have stress and temperature sensitivities quite unlike those observed in single-phase solid solutions having the same composition and grain size. The addition of magnesium or copper to the matrix of a recrystallized dispersion-strengthened aluminum causes a decrease in the steady-state creep rate which is much smaller than that caused by similar amounts of solute in single-phase solid solutions. All alloys exhibited essentially a 4.0 power stress exponent in agreement with the model of Ansell and Weertman. The activation energy for steady-state creep in dispersion-strengthened Al-Mg alloys, as well as the stress dependence, was in agreement with the physical model of dislocation climb over the dispersed particles.

Reynolds, G. H.↗
NASA NTRS1972

Geologic setting of the Apollo 15 samples.

The samples and photographs returned from the Apollo 15 site show that Hadley Delta is largely underlain by breccias whose clasts are mainly fragments of coarse-grained feldspathic rocks and nonmare-type basalt. Conspicuous sets of lineaments, visible in surface and orbital photographs of Mount Hadley and Hadley Delta, may represent systematic layering or fracture sets. The mare surface, with regolith about 5 meters thick, is underlain by two major basalt types, at least one of which has extensive lateral continuity and is exposed in the upper wall of Hadley Rille. Gradual erosional recession of the edges and filing of the interior of the rille by talus have contributed to the present cross sectional profile.

Source record↗
NASA NTRS1972

Emission polarization study on quartz and calcite.

Calculation of the spectral emission polarization of quartz and calcite polished plates for observation angles of 20 and 70 deg by the substitution of complex index of refraction values for each mineral into Fresnel's equations. The emission polarization is shown to be quite wavelength-dependent, demonstrating that selected narrow or medium-width spectral bands exhibit a significantly higher percentage of polarization than a broad spectral band for these two minerals. Field measurements with a broadband infrared radiometer yield polarizations on the order of 2% for a coarse-grained granite rock and beach sand (both quartz-rich). This implies that a more sensitive detector with a selected medium-width filter may be capable of measuring emission polarization accurately enough to make this parameter useful as a remote sensing tool for discrimination among rocks on the basis of texture.

Vincent, R. K.↗
NASA NTRS1972

Diffusion of chromium and aluminum in Ni-20Cr and TDNiCr /Ni-20Cr-2ThO2/.

Diffusion coefficients have been measured for Cr51 in fine- and coarse-grained TDNiCr (Ni-20Cr-2ThO2) and in fine-grained Ni-20Cr in the temperature range from 1038 to 1200 C. Selective diffusivities have also been determined for specimens of these alloys which were aluminized to give an initial surface concentration of 5.8 wt % Al. Finally, diffusion coefficients for interdiffusion of aluminum in TDNiCr and Ni-20Cr have been obtained from electron probe microanalysis of the aluminized specimens. For a given grain size and temperature there is no difference in diffusivities for chromium diffusion in TDNiCr or Ni-20Cr. Diffusion coefficients increase with decreasing grain size for both alloys. Comparison of aluminum diffusion data obtained from electron microprobe profiles with radiotracer chromium diffusivities suggests that aluminum diffuses approximately three times faster than chromium in TDNiCr and Ni-20Cr.

Seltzer, M. S.↗
NASA NTRS1973

High-friction mechanical grips

Plasma-arc spraying offers method of preparing required surface at greatly reduced cost. Coarse-grained, tungsten carbide bonded-nickel coating is applied by spraying. Coating has been used successfully on wedge-shaped mechanical test grips.

Stevens, E. G.↗
NASA NTRS1972

Development of single crystal membranes

The design and construction of a high pressure crystal growth chamber was accomplished which would allow the growth of crystals under inert gas pressures of 2 MN/sq m (300 psi). A novel crystal growth technique called EFG was used to grow tubes and rods of the hollandite compounds, BaMgTi7O16, K2MgTi7O16, and tubes of sodium beta-alumina, sodium magnesium-alumina, and potassium beta-alumina. Rods and tubes grown are characterized using metallographic and X-ray diffraction techniques. The hollandite compounds are found to be two or three-phase, composed of coarse grained orientated crystallites. Single crystal c-axis tubes of sodium beta-alumina were grown from melts containing excess sodium oxide. Additional experiments demonstrated that crystals of magnesia doped beta-alumina and potassium beta-alumina also can be achieved by this EFG technique.

Stormont, R. W.↗
NASA NTRS1973

Apollo 16 exploration of Descartes - A geologic summary.

The Cayley Plains at the Apollo 16 landing site consist of crudely stratified breccias to a depth of at least 200 meters, overlain by a regolith 10 to 15 meters thick. Samples, photographs, and observations by the astronauts indicate that most of the rocks are impact breccias derived from an anorthosite-gabbro complex. The least brecciated members of the suite include coarse-grained anorthosite and finer-grained, more mafic rocks, some with igneous and some with metamorphic textures. Much of the transverse area is covered by ejecta from North Ray and South Ray craters, but the abundance of rock fragments increases to the south toward the younger South Ray crater.

Source record↗
NASA NTRS1973

Breccias from the lunar highlands - Preliminary petrographic report on Apollo 16 samples 60017 and 63335.

Lunar samples 60017,4 and 63335,14 are composed of microbreccias and devitrified glass. These components are predominantly anorthositic, with the exception of a cryptocrystalline clast found in the microbreccia portion of 63335,14 which contains 2.7% potassium oxide and 66.7% silicon dioxide. The samples have been subjected to extreme shock and thermal metamorphism. The parent materials of the microbreccias include both a coarse-grained anorthosite and a fine-grained subophitic anorthositic gabbro.

Kridelbaugh, S. J.↗
NASA NTRS1973

Apollo 17 lunar samples - Chemical and petrographic description

Some of the Apollo 17 rocks have the cataclastic, highly crushed textures common in the Apollo 16 return. Many are crystalline breccias whose petrographic characteristics indicate varying degrees of recrystallization or partial melting. Others are friable and dark gray like the many regolith breccias of previous missions. A few have the coarse-grained igneous textures typically developed during the slow crystallization from basaltic melts. Petrographic and soil characteristics are discussed together with the results of X-ray fluorescence analyses.

Source record↗
NASA NTRS1974

Origin of the high-temperature fraction of C2 chondrites

The coarse-grained fraction of C2 chondrites is composed mostly of single crystals and aggregates of crystals of Mg-rich olivine and pyroxene. They do not possess compelling textural evidence of being the solidification products of rapidly-quenched molten droplets. Metal inclusions in the silicates contain 3.82-8.88 mole% Ni, 0.16-0.70% Co, 0.17-1.07% Cr, and up to 5.70% P. Thermodynamic calculations show that alloys of these compositions may be condensates from the solar nebula. The implication is that the high-temperature fraction of C2 chondrites consists mostly of high-temperature condensates.

Grossman, L.↗
NASA NTRS1974

Magnetic properties of Apollo 16 samples and implications for their mode of formation

The Apollo 16 crystalline rocks have a greater average percentage of metallic iron than any other lunar material and are the most reduced in terms of their metallic iron/total iron ratio. They have greater metal content than the mare basalts, the only primary igneous rocks on the moon, and more iron metal than the associated Apollo 16 breccias and soils. This fact and the relatively coarse grain size suggest reduction of the iron during the formation of the crystalline rocks, probably during melts and partial melts in an impact base surge deposit.

Pearce, G. W.↗
NASA NTRS1974

Lunar highland rock types: Their implications for impact induced fractionation

The first step in a petrologic study must be a classification based on observed textures and mineralogy. Lunar rocks, may be classified into three major groups: (1) coarse-grained igneous rocks, (2) fine-grained igneous rocks and (3) breccias. Group 1 is interpreted as primitive lunar crustal rocks that display various degrees of crushing and/or annealing. Group 2 is interpreted as volcanic rocks. Group 3 is interpreted as resulting from impacts on the lunar surface and is subdivided on the basis of matrix textures into fragmental breccias, crystalline breccias that have been annealed, and crystalline breccias with igneous matrices. A synthesis of the relevant data concerning lunar highlands polymict breccias from the fields of petrography, chemistry, photogeology, and impact studies compels the prediction that the breccias should have homogeneous matrices from rock to rock within regions of the highlands of limited size where impact mixing has been efficient and extensive.

Phinney, W. C.↗
NASA NTRS1974

Ferroan anorthosite - A widespread and distinctive lunar rock type

Eight of eleven Apollo 16 rake-sample anorthosites are very similar to each other, to hand-specimen Apollo 16 anorthosites, and to Apollo 15 anorthosites. They have feldspar An-96.6, both high- and low-Ca pyroxene with a restricted range of (low-magnesium) composition, minor olivine, traces of ilmenite and chromite, and originally coarse-grained, but now cataclastic texture. Such ferroan anorthosite is evidently a coherent, distinctive and widespread lunar rock type of cumulate origin which may not necessarily be very closely related genetically to other highland rock types.

Dowty, E.↗
NASA NTRS1974

Chemical compositions of some soils and rock types from the Apollo 15, 16, and 17 lunar sites

The major and minor element compositions of three Apollo 15 mare basalts, four Apollo 16 breccias, one soil, three Apollo 17 soils, one mare basalt, and one breccia have been determined by semimicro combined atomic absorption and colorimetric spectrophotometries. A discussion regarding analysis of small subsamples of coarse-grained lunar materials, such as certain Apollo 15 and 17 basalts, is given in which the suggestion is made that analytical methods designed to determine the bulk 'representative' chemical composition as well as the presence and extent of specimen heterogeneity are fundamentally necessary for a more complete understanding of genesis and history of lunar materials.

Nava, D. F.↗
NASA NTRS1974

Chemical composition of rocks and soils at Taurus-Littrow

Seventeen soils and seven rock samples were analyzed for major elements, minor elements, and trace elements. Unlike the soils at previous Apollo sites, which showed little difference in composition at each collection area, the soils at Taurus-Littrow vary widely. Three soil types are evident, representative of (1) the light mantle at the South Massif, (2) the dark mantle in the valley, and (3) the surface material at the North Massif. The dark-mantle soils are chemically similar to those at Tranquillitatis. Basalt samples from the dark mantle are chemically similar although they range from fine to coarse grained. It is suggested that they originated from the same source but crystallized at varying depths from the surface.

Rose, H. J., Jr.↗
NASA NTRS1974

Chemical evidence for the origin of 76535 as a cumulate

Lunar sample 76535 is a coarse-grained troctolitic granulite. It is characterized by low REE concentrations and a positive Eu anomaly. Its original petrographic character has been disturbed by metamorphic reequilibration. Its chemical characteristics are those of an olivine-plagioclase cumulate. The amount of trapped parent liquid in the rock is estimated to be in the range of 8-16%. The REE concentrations of the parent liquid, if 16%, range from 13 times the chondritic value for Lu to 27 times for La. The parent liquid had no appreciable Eu anomaly.

Haskin, L. A.↗
NASA NTRS1976

Latitudinal variation of wind erosion of crater ejecta deposits on Mars

The characteristics of wind erosion as the dominant process involved in eroding crater ejecta deposits on Mars are studied. Present-day crater formation in mid to high latitudes involves impact into some thickness of aeolian debris, while impact in the equatorial zone is more likely to involve target materials consisting of coarse-grained aeolian lag deposits or even bedrock. Latitudinal variation dominates differences in ejecta emplacement mechanisms and probably differences in patterns of wind erosion of ejecta and surrounding intercrater materials. Escarpments develop as the deposits are eroded back toward crater rims. Erosion only takes places at escarpment edges where surface roughness may be low enough to allow particle entrainment. Preferential preservation of ejecta emplaced in thick debris may occur. An empirical model developed for wind erosion of ejecta deposits in nonmantled areas suggests that removal of ejecta materials on the average is exceedingly slow. Results suggest high differential aeolian erosion rates that are a function of both grain sizes and large-scale surface roughness.

Arvidson, R. E.↗
NASA NTRS1975

Mineralogy of lunar norite 78235 - Second lunar occurrence of P2 sub 1 ca pyroxene from Apollo 17 soils

A thin section of lunar rock 78235 is examined optically as well as with an electron microprobe and is shown to be a highly-shocked coarse norite. The rock is found to consist of approximately 30% low-Ca pyroxene, 55% Ca-rich plagioclase, and 15% glass veins. The composition of the glass veins is analyzed, and it is suggested that they resulted from shock melting of the norite. Comparisons with other noritic rocks indicate that the pyroxene in rock 78235 has P2 sub 1 ca symmetry. Based on this symmetry plus the coarse grain size, it is concluded that rock 78235 was formed under plutonic conditions. The origin of the minor phases in this rock is briefly considered.

Steele, I. M.↗