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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 379 records · Page 21
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NASA NTRS1981

Ion sputtering from satellite surfaces

The manifestations of the induced surface currents as observed by the magnetic ion mass spectrometer (MIMS) and retarding potential analyzer (RPA) instruments on AE-C and AE-D are described. Data from these instruments are used to infer the source of some of the different secondary ions observed, as well as their time history and emission energy. It is noted that the emitted particles have a characteristic energy of approximately 1 eV in the spacecraft frame of reference and lack the normal ram energy possessed by the ambient ions. Alkali ions Na(+) and K(+), in addition to nonionospheric NO(+) and O2(+), are observed at low altitudes. With the exception of NO(+), all these are thought to be released by impacts of neutral N2 or O2 with the surfaces. These ion currents decrease with a time constant of about six weeks for the alkali and four weeks for the O2 ions.

Hanson, W. B.↗
NASA NTRS1981

Petrochemical constraints on lateral transport during lunar basin formation

Lunar ANT petrochemistry correlates with longitude, allowing the sampled region of the moon to be divided into three geochemical provinces: western (Apollo 12 and 14), near-eastern (Apollo 11, 15, 16 and 17) and far-eastern (Luna 16, 20 and 24). A western ANT rock has a far greater Eu anomaly for a given Sm content than does a near-eastern ANT rock, which is in turn has a somewhat greater Eu anomaly than does a far-eastern ANT rock. Distinct differences are also observed in Sc/Sm and Ti/Sm ratios (western ANT rocks have lower ratios) and in the abundances of alkali-rich anorthosites (five of the six known anorthosites from the west are approximately four times richer in Na and K than are ferroan anorthosites, whereas none of the 40 known anorthosites from the near east is alkali-rich). The existence of this distinct correlation of ANT geochemical properties with longitude implies that even during the first few hundred m.y. of lunar history basin-forming impacts were not capable of efficiently redistributing material laterally across the lunar surface.

Warren, P. H.↗
NASA NTRS1981

Metal-halide mixtures for latent heat energy storage

Alkali metal and alkali halide mixtures are identified which may be suitable for thermal energy storage at temperatures above 600 C. The use of metal-halides is appropriate because of their tendency to form two immiscible melts with a density difference, which reduces scale formation and solidification on heat transfer surfaces. Also, the accumulation of phase change material along the melt interface is avoided by the self-dispersing characteristic of some metal-halides, in particular Sr-SrCl2, Ba-BaCl2, and Ba-BaBr2 mixtures. Further advantages lie in their high thermal conductivities, ability to cope with thermal shock, corrosion inhibition, and possibly higher energy densities.

Chen, K.↗
NASA NTRS1983

Radiation energy receiver for laser and solar propulsion systems

The concept of remotely heating a rocket propellant with a high intensity radiant energy flux is especially attractive due to its high specific impulse and large payload mass capabilities. In this paper, a radiation receiver-thruster which is especially suited to the particular thermodynamic and spectral characteristics of highly concentrated solar energy is proposed. In this receiver, radiant energy is volumetrically absorbed within a hydrogen gas seeded with alkali metal vapors. The alkali atoms and molecules absorb the radiant flux and, subsequently, transfer their internal excitation to hydrogen molecules through collisional quenching. It is shown that such a radiation receiver would outperform a blackbody cavity type receiver in both efficiency and maximum operating temperatures. A solar rocket equipped with such a receiver-thruster would deliver thrusts of several hundred newtons at a specific impulse of 1000 seconds.

Rault, D. F. G.↗
NASA NTRS1984

Investigation and Rehabilitation to Extend Service Life of DSS-13 Antenna Concrete Foundation

An investigation to establish the cause and, devise a repair technique to maintain the serviceability of the DSS-13 26 meter antenna is described. Core samples are obtained from the concrete and various laboratory tests conducted. In-place nondestructive type tests are also performed. The tests established that the concrete is deteriorating because of alkali aggregate reactivity. This is a phenomenon wherein certain siliceous constituents present in some aggregates react with alkalies in the portland cement to produce a silica gel which, in turn, imbibes water, swells, and cracks the concrete. The scheme consists of a supplemental steel frame friction pile anchored grade beam encircling the existing foundation. This system provides adequate bracing against base shear and overturning due to seismic loading. Larger cracks are sealed using a pressure injected two-component epoxy.

Riewe, A. A., Jr.↗
NASA NTRS1983

Seventh Foray - Whitlockite-rich lithologies, a diopside-bearing troctolitic anorthosite, ferroan anorthosites, and KREEP

Seventeen nonmare samples, most of them pristine, are characterized, and implications of the new data are discussed. Five pristine samples are from Apollo 14, near the center of the KREEP-rich zone in the moon's western hemisphere. Three of them are alkali anorthosites rich in Ca-phosphate (whitlockite), which apparently crystallized from magmas with REE contents roughly 6 x those of high-K KREEP. The alkali anorthosites probably formed from Mg-rich magmas that assimilated large amounts of urKREEP, but some might have formed by metasomatism of ferroan anorthosite by urKREEP. The gabbronorite/norite classification scheme is not well suited to western hemisphere lithologies, probably due mainly to the overriding effects of longitude-petrochemistry correlations. A diopside-bearing Mg-rich lithology indicates that a low degree of melting was not a prerequisite for producing gabbroic (high-Ca pyroxene-rich) Mg-rich magmas, and suggests that some source regions of Mg-rich magmas were relatively Ca-rich. Several pristine KREEP fragments from Apollo 15 station 2 are texturally and compositionally much like other pristine KREEP, and thus reinforce the evidence that KREEP is highly uniform. The pristine anorthosites, on the other hand, demonstrate further that lunar anorthosites are diverse.

Warren, P. H.↗
NASA NTRS1984

Pristine highland clasts in consortium breccia 14305 Petrology and geochemistry

Data are presented on the petrography and mineral chemistry of six pristine highland clasts chipped from the polymict lunar breccia 14305. Major and trace elements in the clasts were determined by instrumental neutron activation analysis, and mineral analyses were performed by electron microprobe. Mg-suite clasts have 'eastern' geochemical affinities, reaffirming the importance of local variations in geochemistry. These local variations are superimposed on the moon-wide, longitudinal variations noted by Warren and Wasson (1980). Alkali anorthosites and Mg-suite troctolites and anorthosites are not comagmatic, and cannot be related to a single parent magma by either fractional crystallization or variable assimilation of KREEP. Both magma suites may have assimilated varied amounts of KREEP into distinct parent magmas. Alternatively, alkali anorthosites may have crystallized directly from a KREEP-basalt parent magma. A thick crust of ferroan anorthosite probably never existed on the western lunar nearside, or was removed by basin-forming impacts prior to intrusion of later plutonic suites.

Shervais, J. W.↗
NASA NTRS1985

Theoretical transition probabilities between the lowest 2S, 2P and 2D states of Na, K, Rb and Cs

Theoretical transition probabilities between the lowest 2S, 2P and 2D states of the alkali atoms Na through Cs have been computed using near Hartree-Fock quality Slater basis sets. The important core-valence correlation effects are incorporated explicitly by a configuration-interaction procedure. For Cs, the calculations were repeated using a Gaussian basis set so that relativistic effects could be incorporated through an effective core potential procedure. The best calculated electric quadrupole Einstein coefficients are Na(196.3/s), K(103.6/s), Rb(72.4/s) and Cs(19.7/s). Core-valence effects become increasingly important down the column, and reduce the quadrupole transition strengths to about the same degree as for the 2P-2S and 2D-2P dipole-allowed transitions. Relativistic effects increase the quadrupole moment of Cs, but less so than in Ba, presumably because the alkali 2D states are more diffuse.

Langhoff, S. R.↗
NASA NTRS1986

Theoretical dissociation energies for ionic molecules

Ab initio calculations at the self-consistent-field and singles plus doubles configuration-interaction level are used to determine accurate spectroscopic parameters for most of the alkali and alkaline-earth fluorides, chlorides, oxides, sulfides, hydroxides, and isocyanides. Numerical Hartree-Fock (NHF) calculations are performed on selected systems to ensure that the extended Slater basis sets employed for the diatomic systems are near the Hartree-Fock limit. Extended Gaussian basis sets of at least triple-zeta plus double polarization equality are employed for the triatomic system. With this model, correlation effects are relatively small, but invariably increase the theoretical dissociation energies. The importance of correlating the electrons on both the anion and the metal is discussed. The theoretical dissociation energies are critically compared with the literature to rule out disparate experimental values. Theoretical (sup 2)Pi - (sup 2)Sigma (sup +) energy separations are presented for the alkali oxides and sulfides.

Langhoff, S. R.↗
NASA NTRS1988

Biphase Metal Electrodes For AMTEC

New biphase metal electrodes for alkali metal thermoelectric converter (AMETEC) exhibit low electrical resistance, fast alkali metal transport, and good power densities and lifetime at operating temperatures from 1,100 to 1,160 K. Electrodes expected to last as long as 10,000 h in service without significant degradation. Made of two refractory metals, one forms strong bonds with sodium, other inert to sodium.

Williams, R.↗
NASA NTRS1990

Positronium formation in Ss state in e+-Li scattering

There are ample theoretical reasons to investigate positron-alkali atom scattering. Moreover, recent measurement on positron-alkali atom system by a Detroit group has renewed much interest in investigating these processes. Positronium (Ps) formation in excited 2s state in positron-Li scattering at intermediate and high energies were studied including second order effects following Basu and Ghosh.

Sarkar, K. P.↗
NASA NTRS1989

Theoretical study of metal noble-gas positive ions

Theoretical calculations have been performed to determine the spectroscopic constant for the ground and selected low-lying electronic states of the transition-metal noble-gas ions Var(+), FeAr(+), CoAr(+), CuHe(+), CuAr(+), and CuKr(+). Analogous calculations have been performed for the ground states of the alkali noble-gas ions LiAr(+), LiKr(+), NaAr(+), and KAr(+) and the alkaline-earth noble-gas ion MgAr(+) to contrast the difference in binding energies between the simple and transition-metal noble-gas ions. The binding energies increase with increasing polarizability of the noble-gas ions, as expected for a charge-induced dipole bonding mechanism. It is found that the spectroscopic constants of the X 1Sigma(+) states of the alkali noble-gas ions are well described at the self-consistent field level. In contrast, the binding energies of the transition-metal noble-gas ions are substantially increased by electron correlation.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1991

Aqueous alteration in five chondritic porous interplanetary dust particles

Results are presented on AEM observations carried out on chondritic porous (CP) interplanetary dust particles (IDPs), which include data on alkali-rich layer silicates and new observations of nonstoichiometric plagioclase and alkali feldspars in individual CP IDPs. The compositional similarities found between the feldspar minerals and the layer silicates suggest that the latter have formed from these feldspars during low-temperature aqueous alterations at a stage of diagenesis in the CP IDP parent bodies. Small, but persistent, amounts of layer silicates, carbonates, and barite found in several nominally anhydrous CP IDPs support the suggestion of incipient aqueous alterations in their parent bodies, which may include short-period comet nuclei and outer-belt asteroids.

Rietmeijer, Frans J. M.↗
NASA NTRS1991

New observations on the quartz monzodiorite-granite suite

Five new fragments of quartz monzodiorite (QMD) were identified in particles from soil 15403, which was collected from the boulder sampled as rock 15405, an impact-melt breccia containing clasts of KREEP basalt, QMD, granite, and a more primitive alkali norite. Petrographic and geochemical studies of the fragments show considerable variation in modal proportions and bulk composition. This heterogeneity is due to unrepresentative sampling in small fragments of coarse-grained rocks. Variations in the proportions of accessory minerals have marked effects on incompatible-trace-element concentrations and ratios. Semiquantitative calculations support the derivation of QMD from 60-percent fractional crystallization of a KREEP basalt magma as suggested by Hess (1989). Apollo 15 KREEP basalt cannot be the actual parent magma because the evolved rocks predate volcanic KREEP basalts. It is suggested that ancient KREEP basalt magmas have crystallized as plutons, with alkali norite clasts offering the only direct evidence of this precursor.

Marvin, U. B.↗
NASA NTRS1992

Petrogenesis of the western highlands of the moon - Evidence from a diverse group of whitlockite-rich rocks from the Fra Mauro formation

A group of KREEPy basalts has been discovered in Apollo 14 soils. These samples exhibit similarities to both HA and VHK basalts, albeit with much higher REE abundances, and contain up to 2 vol pct whitlockite and can be explained by assimilation of a K-, REE- and P-rich fluids by an original HA or VHK basalt. This KREEP component could have been produced late in the evolution of the lunar magma ocean and is similar in composition to QMD at Apollo 14. Two rocks have trace element compositions that are representative of actual KREEP. One of the samples appears to be petrographically pristine and could represent an actual KREEP basalt rock. Five subophitic high-Al basalts represent sampling of either a slowly cooled impact melt sheet or, more likely, the same basalt flow. Two 'quasi-pristine' highland rocks confirm the postulate of a connection between KREEP and the alkali suite. A newly discovered alkali anorthosite is a plagioclase cumulate with about 15 percent trapped KREEPy liquid.

Snyder, Gregory A.↗
NASA NTRS1993

Global expression for representing cohesive-energy curves. II

Schlosser et al. (1991) showed that the R dependence of the cohesive energy of partially ionic solids may be characterized by a two-term energy relationship consisting of a Coulomb term arising from the charge transfer, delta-Z, and a scaled universal energy function, E*(a *), which accounts for the partially covalent character of the bond and for repulsion between the atomic cores for small R; a* is a scaled length. In the paper by Schlosser et al., the normalized cohesive-energy curves of NaCl-structure alkali-halide crystals were generated with this expression. In this paper we generate the cohesive-energy curves of several families of partially ionic solids with different crystal structures and differing degrees of ionicity. These include the CsCl-structure Cs halides, and the Tl and Ag halides, which have weaker ionic bonding than the alkali halides, and which have the CsCl and NaCl structures, respectively. The cohesive-energy-curve parameters are then used to generate theoretical isothermal compression curves for the Li, Na, K, Cs, and Ag halides. We find good agreement with the available experimental compression data.

Schlosser, Herbert↗
NASA NTRS1993

Os isotopes in SNC meteorites and their implications to the early evolution of Mars and Earth

A new development on the measurement of the Os isotopic composition by mass spectrometry using negative ions opened a new field of applications. The Re-Os systematic provides time information on the differentiation of the nobel metals. The nobel metals are strongly partitioned into metal and sulphide phases, but also the generation of silicate melts might fractionate the Re-Os system. Compared to the other isotopic systems which are mainly dating the fractionation of the alkalis and alkali-earth elements, the Re-Os system is expected to disclose entirely new information about the geochemistry. Especially the differentiation and early evolution of the planets such as the formation of the core will be elucidated with this method.

Jagoutz, E.↗
NASA NTRS1994

Aubrite basalt vitrophyres: High sulfur silicate melts and a snapshot of aubrite formation

Two aubrite basalt vitrophyre clasts have been found within AMNH thin sections from the Parsa EH3 chondrite and the Khor Temiki aubrite. Polished sections of the Parsa Aubrite Inclusion (PAI) and the Khor Temiki Inclusion (KTI) were studied by optical, electron probe microanalysis (EPMA), and scanning electron microscopy (SEM) techniques with broad-beam and low absorbed EPMA currents used to minimize glass volatile loss. Some data have previously been reported for PAI and KTI may possibly correlate to a previously reported inclusion in Khor Tiimiki. In polished sections, PAI and KTI are approximately equal 4 mm in diameter and contain a large volume of glass. The clasts have similar textural characteristics and are akin to lunar vitrophyre textures. The glasses have high alkali rhyodacitic compositions Al-though PAI is peraluminous, KTI is significantly peralkaline. Additionally, the glasses have elevated sulfur concentrations that are extremely high by geochemical standards. SEM examination for beam overlap of microscopic CaS, FeS, and (Mg, Mn, Fe) S inclusions showed no such contamination. Furthermore, homogeneity of glass S content and low FeO contents help rule out contamination. Materials research data show that under reducing conditions alumino-silicate melts can dissolve up to several weight percent sulfur in the absence of Fe. The high S and alkali contents, the lack of associated high shock features, and the rationalized phase equilibria suggest that PAI and KTI are igneous melting products of an E-chondrite-like source material. Although large-scale impact melting cannot totally be ruled out, the above observations eliminate the possibility of in-situ shock melting.

Fogel, R. A.↗