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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 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Spectral line shapes. Volume 4 - Proceedings of the Eighth International Conference, College of William and Mary, Williamsburg, VA, June 9-13, 1986

The present conference discusses topics in line broadening and shift phenomena in low-to-moderately dense plasmas, resonances in the continuum, hot and dense laser-produced plasmas, collisional broadening and intermolecular potentials, molecular broadening and collision-induced spectroscopy, collisional redistribution and laser-assisted collision processes, coherent and nonlinear spectroscopy, astrophysical line-shapes, and short-wavelength lasers. Attention is given to the widths and shifts of Be ion lines, the Stark broadening of Xe II and Fe I lines, perturbed and unperturbed series in the line-shapes of autoionizing Rydberg series, the line-broadening of hydrogenic ions in dense plasmas, Doppler-free line-shapes, the Franck-Condon principle, the dynamics of laser-assisted reactive collisions, the gas-kinetic effects of light, collision-induced processes in nonlinear optics, and line-shaping phenomena in cool stars.

Exton, Reginald J.↗
NASA NTRS1988

Parametric studies of electric propulsion systems for orbit transfer vehicles

The present parametric tradeoff study for OTV electric propulsion systems encompasses ammonia and hydrogen arcjets as well as Xe-ion propulsion systems with performance characteristics currently being projected for 1993 operation. In all cases, the power source is a nuclear-electric system with 30 kg/kW(e) specific mass, and the mission involves the movement of payloads from lower orbits to GEO. Attention is given to payload capabilities and associated propellant requirements. Mission trip time is identified as the key parameter for selection; while arcjets are preferable for shorter trip times, ion propulsion is more advantageous for longer trip times due to reduced propellant mass fraction.

Manvi, R.↗
NASA NTRS1988

Ejection of sodium from sodium sulfide by the sputtering of the surface of Io

The mechanism by which Na is removed from the surface of Io prior to its injection into the plasma torus is investigated experimentally. Na2S films of thickness 3-8 microns were produced by spray coating an Ni substrate in a dry N2 atmosphere and subjected to sputtering by 34-keV Ar(+), Ne(+), Kr(+), or Xe(+) ions up to total doses of about 5 x 10 to the 18th ions/sq cm. The sputtering yields and mass spectra are found to be consistent with ejection of only small amounts of atomic Na and somewhat larger amounts of Na-containing molecules. It is concluded that the amount of Na ejected by magnetospheric-ion sputtering of Na2S would be insufficient to account for the amounts observed in the Io neutral cloud. A scenario involving sputtering of larger polysulfide molecules is considered.

Chrisey, D. B.↗
NASA NTRS1988

Electric propulsion for constellation deployment and spacecraft maneuvering

This paper outlines the near-term (1990s) advantages of electric propulsion for two SDI missions: (1) the launch of a constellation of spacecraft, and (2) continual spacecraft defensive maneuvering. Ammonia arcjet and Xe-ion electric propulsion systems are compared to advanced chemical propulsion for each of these missions. The number of launch vehicles required for constellation deployment can be reduced by up to a factor of 2 when electric propulsion upper stages are used in place of advanced upper stages. Electric propulsion can provide significant benefits when used for continuous defensive maneuvering by enabling a large reduction in the initial spacecraft mass.

Deininger, W. D.↗
NASA NTRS1989

Theoretical studies in support of the 3M-vapor transport (PVTOS-) experiments

Results are reported for a preliminary theoretical study of the coupled mass-, momentum-, and heat-transfer conditions expected within small ampoules used to grow oriented organic solid (OS-) films, by physical vapor transport (PVT) in microgravity environments. It is show that previous studies made restrictive assumptions (e.g., smallness of delta T/T, equality of molecular diffusivities) not valid under PVTOS conditions, whereas the important phenomena of sidewall gas creep, Soret transport of the organic vapor, and large vapor phase supersaturations associated with the large prevailing temperature gradients were not previously considered. Rational estimates are made of the molecular transport properties relevant to copper-phthalocyanine monomeric vapor in a gas mixture containing H2(g) and Xe(g). Efficient numerical methods have been developed and are outlined/illustrated here to making steady axisymmetric gas flow calculations within such ampoules, allowing for realistic realistic delta T/T(sub)w-values, and even corrections to Navier-Stokes-Fourier 'closure' for the governing continuum differential equations. High priority follow-on studies are outlined based on these new results.

Rosner, Daniel E.↗
NASA NTRS1988

Lunar and Planetary Science Conference, 18th, Houston, TX, Mar. 16-20, 1987, Proceedings

Papers on lunar and planetary science are presented, including petrogenesis and chemistry of lunar samples, geology and petrogenesis of the Apollo 15 landing site, lunar geology and applications, cratering records and cratering effects, differentiated meteorites, chondritic meteorites and asteroids, extraterrestrial grains, Venus, Mars, and icy satellites. The importance of lunar granite and KREEP in very high potassium basalt petrogenesis, indentifying parent plutonic rocks from lunar breccia and soil fragments, glasses in ancient and young Apollo 16 regolith breccias, the formation of the Imbrium basin, the chemistry and petrology of the Apennine Front, lunar mare ridges, studies of Rima Mozart, electromagnetic energy applications in lunar resource mining and construction, detecting a periodic signal in the terrestrial cratering record, and a search for water on the moon, are among the topics discussed. Other topics include the bidirectional reflectance properties of Fe-Ni meteorites, the nature and origin of C-rich ordinary chondrites and chondritic clasts, the dehydration kinetics of shocked serpentine, characteristics of Greenland Fe/Ni cosmic grains, electron microscopy of a hydrated interplanetary dust particle, trapping Ne, Ar, Kr, and Xe in Si2O3 smokes, gossans on Mars, and a model of the porous structure of icy satellites.

Ryder, Graham↗
NASA NTRS1988

Solar, planetary, and other inert gases in two sieve fractions of a disaggregated Allende sample - A study by stepwise heating extraction

Inert gases released by stepwise heating of unaltered, strongly magnetic, and weakly magnetic samples from the 0-64 micron and the 105-250 micron fractions of a disaggregated and sieved sample of the Allende meteorite reveal the occurrence of both solar and planetary neon. The origin of the solar neon is thought to be implantation of solar wind ions. The origin of the planetary neon remains unresolved. Heavy isotope enriched components of krypton and xenon have been detected and there are some indications that a light krypton component may also be present. Other than a larger concentration of Xe-129 in the weakly magnetic samples, the signatures of the magnetic separates are isotopically very similar.

Palma, R. L.↗
NASA NTRS1988

Initial Sr-87/Sr-86 and Sm-Nd chronology of chondritic meteorites

Isotopic analyses of the Rb-Sr and Sm-Nd systems in phosphates from ordinary chondritic meteorites (Bjurbole, Mocs, Menow, Elenovka, Ambapur Nagla, and St. Severin) are presented. The Sm-Nd data yield an isochron of age 4.55 + or - 0.45 Ga and an initial Nd-143/Nd-144 consistent with that of Juvinas. Initial Sr-87/Sr-86 ratios are characteristically (possibly excepting St. Severin) elevated with respect to BABI or ALL. Considering both presently and previously reported data, elevation of initial Sr-87/Sr-86 ratios corresponding to metamorphism intervals of the order of 10 to the 8th years seems quite characteristic of chondrites of metamorphic grade 4 or higher. These formation intervals, however, do not correlate with either degree of metamorphism or with I-Xe ages, hence such data for metamorphic chronologies should be interpreted with caution.

Brannon, J. C.↗
NASA NTRS1988

Interstellar silicon carbide - How much older than the solar system?

The SiC grains in C2 chondrites have large isotopic anomalies in Si, C, N, Ne, and Xe, and thus are virtually undegraded interstellar matter that survived formation of the solar system. They also contain excess Ne-21, of which only a minor part can have formed during the recent, 1 Myr cosmic-ray exposure of the meteorite. If the excess Ne-21 is cosmogenic, then the presolar exposure age of the SiC is 41 + 20 or - 14 Myr. This age is surprisingly short compared to the predicted lifetime of refractory interstellar grains, 500-1000 Myr. Possible explanations are: (1) the predicted grain lifetime is wrong, (2) the age of SiC has been falsified by neon losses, or (3) the solar system formed in part from atypically young material.

Ming, Tang↗
NASA NTRS1989

Properties, detectability and origin of interstellar diamonds in meteorites

Laboratory studies suggest that microdiamonds will be quite elusive in interstellar space, being detectable only if more than 10 per cent of the carbon is present as diamond. The diamonds apparently formed by condensation in cool stellar atmospheres, and were then impregnated with isotopically anomalous noble gases, such as Xe, from a supernova.

Lewis, Roy S.↗
NASA NTRS1989

Laboratory simulation of meteoritic noble gases. III - Sorption of neon, argon, krypton, and xenon on carbon - Elemental fractionation

The sorption of Ne, Ar, Kr, and Xe was studied in carbon black, acridine carbon, and diamond in an attempt to understand the origin of trapped noble gases in meteorites. The results support a model in which gases are physically adsorbed on interior surfaces formed by a pore labyrinth within amorphous carbons. The data show that: (1) the adsorption/desorption times are controlled by choke points that restrict the movement of noble gas atoms within the pore labyrinth, and (2) the physical adsorption controls the temperature behavior and elemental fractionation patterns.

Wacker, John F.↗
NASA NTRS1989

Cosmogenic helium and volatile-rich fluid in Sierra Leone alluvial diamonds

Noble gas measurements were carried out on two identical splits of a finely powdered harshly acid-washed sample derived from fragments of a single alluvial diamond from Sierra Leone, with essentially identical results obtained for both splits. Isotopic ratios for Ar, Kr, and Xe were found to be atmospheric. Their elemental abundances were high relative to published data, owing to the effect of shock implantation in the crushing step, as was verified in a supplementary experiment. No Ne was detected above the blank level. The He-3 was exceptionally abundant, while He-4 was exceptionally depleted, possibly due to the acid wash. The He-3/He-4 ratio was anomalously high at an R/Ra value of 246 + or - 16. The results support the hypothesis that the He-3 excess in diamonds is cosmogenic.

Mcconville, P.↗
NASA NTRS1988

Ion formation by electron impact

Dissociative attachment and polar dissociation cross sections were measured for the following molecules: HC1, NO, N2O, C6H6, SiH4, Si2H6, and LiH. Direct ionization and dissociative ionization cross sections were determined for the following molecules: H2, D2, N2, O2, He, Ne, Ar, Kr, Xe, H2O, Co, CO2, CH4, SiH4, Sih4, Si2H6, N2*, and NH3. An experimental apparatus for a pulsed extraction technique was fabricated and successfully tested.

Srivastava, Santosh K.↗
NASA NTRS1990

Positron-inert gas differential elastic scattering

Measurements are being made in a crossed beam experiment of the relative elastic differential cross section (DCS) for 5 to 300 eV positrons scattering from inert gas atoms (He, Ne, Ar, Kr, and Xe) in the angular range from 30 to 134 deg. Results obtained at energies around the positronium (Ps) formation threshold provide evidence that Ps formation and possibly other inelastic channels have an effect on the elastic scattering channel.

Kauppila, W. E.↗
NASA NTRS1989

Nuclear-electric propulsion - Manned Mars propulsion options

Nuclear-electric propulsion can significantly reduce the launch mass for manned Mars missions. By using high-specific-impulse (lsp) electric propulsion systems with advanced nuclear reactors, the total mass-to-orbit for a series of manned Mars flight is reduced. Propulsion technologies required for the manned Mars mission are described. Multi-megawatt Ion and Magneto-Plasma-Dynamic (MPD) propulsion thrusters, Power-Processing Units and nuclear power source are needed. Xenon (Xe)-Ion and MPD thruster performance are detailed. Mission analyses for several Mars mission options are addressed. Both MPD and Ion propulsion were investigated. A four-megawatt propulsion system power level was assumed. Mass comparisons for all-chemical oxygen/hydrogen propulsion missions and combined chemical and nuclear-electric propulsion Mars fleets are included. With fleets of small nuclear-electric vehicles, short trip times to Mars are also enabled.

Palaszewski, Bryan↗
NASA NTRS1990

Tables and intercomparisons of evolutionary sequences of models for massive stars

Tables of evolutionary sequences of models for massive stars have been prepared for a variety of physical input parameters that are normally treated as free. These parameters include the interior convective mixing scheme, the mixing length in the outer convective envelope, the rate of stellar-wind mass loss, the initial stellar mass, and the initial chemical composition. Ranges of specified initial mass and initial chemical composition are M = 10-120 solar masses, Xe = 0.602-0.739, and Ze = 0.021-0.044. The tables cover evolution of the star from the ZAMS to either the end of core H burning or the end of core He burning. Differences among the evolutionary tracks are illustrated primarily in terms of the interior mixing scheme, since the amount and timing of stellar wind mass loss are still very uncertain for initial masses above about 30 solar masses.

Chin, Chao-Wen↗
NASA NTRS1991

Overview of European and other non-US/USSR/Japan launch vehicle and propulsion technology programs

The following subject areas are covered: majority of propulsion technology development work is directly related to the ESA's Ariane 5 program and heavily involves SEP (Societe Europeenne de Propulsion) in all areas; Hermes; advanced work on magnetic bearings for turbomachinery; electric propulsion using Cs and Xe propellants done by SEP in France, MBB ERNO in West Germany, and by Culham Lab in UK; successfully tested fired H/O composite nozzle exit cone on 3rd stage of Ariane; turbine blades made of composites to allow increase in gas temperature and improvement in efficiency; combined cycle (turboramjet-rocket) engine analysis work done by Hyperspace; and ESA advanced program studies.

Rice, Eric E.↗
NASA NTRS1991

A lidar equipped with photon counter for measuring stratospheric aerosols

A large lidar system was developed at the Anhui Institute of Optics and Fine Mechanics. It is composed of a high power frequency doubled Nd:YAG laser (120 mJ at 532 nm, 1 mrad), a 651 mm diameter receiving telescope, and a 64 channel photon counter. The lidar observations are controlled by an IBM PC/AT computer. One of the projects is to use the lidar system to make regular observations of stratospheric aerosols. Profiles of scattering ratio have been obtained since November 1989. Meanwhile, an Xe-Cl laser (308 nm wavelength) was assembled to allow the lidar to make measurements of vertical ozone distributions.

Zhou, Jun↗