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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Evaluation of radiation interference in the Voyager Sun Sensor's cadmium sulfide detector

The simulation of radiation interference effects and the results of a radiation interference test on two Voyager Sun Sensor prototype detector assemblies are reported. The derivation of test levels and requirements are discussed and show that cobalt 60 gamma radiation is an effective and practical simulator of the ionization dose rate effects induced by high-energy electron flux incident on the spacecraft at a rate of 3.7 x 10 to the 8th e/sq cm-sec (10 rad(Si)/s) during closest approach to Jupiter. The test results provide information that is used to confirm an analytic correlation, and to predict satisfactory performance of a spacecraft sun sensing device having stringent angular resolution requirements. The measured detector response shows that at dose rates incident on the detector elements of 2 rad(Si)/sec, which is four times that expected during Jupiter encounter, the radiation-induced angle error is almost an order of magnitude less than that allowed by the acceptance criteria.

Clarke, T. C.↗
NASA NTRS1979

Iron-nickel sulfides in the Murchison meteorite and their relationship to phase Q1

Pentlandite from the Murchison meteorite survives HF-HCl attack and dissolves in HNO3 at room temperature, thus satisfying the operational definition of phase Q1, the proposed major carrier of carbonaceous chondrite fission xenon. However, identification of pentlandite with that phase is problematical in view of apparently differing thermal stabilities.

Kerridge, J. F.↗
NASA NTRS1981

Long wavelength carbonyl sulfide photodissociation

The aeronomic implications of a preliminary observation of weak OCS photoabsorption above 270 nm are investigated. It is argued that the measured cross section is consistent with a forbidden transition in this wavelength region. Model calculations are made for the OCS photodissociation rates in daylight, the OCS and SO2 distributions in the upper atmosphere, and the budgets of sulfur in the stratosphere and OCS in the troposphere, assuming various extrapolations of the measured OCS absorption cross sections and quantum yields to longer wavelengths. It is shown that weak OCS absorption above 300 nm can have important consequences for all of these quantities. Laboratory and field experiments are identified which might lead to a better understanding of the atmospheric OCS cycle.

Turco, R. P.↗
NASA NTRS1981

A High Resolution Spectroscopic Study of the Nu2 Band of Hydrogen Sulfide and the 1-0 Band of Hydrogen Iodide

A tunable diode laser spectrometer was constructed and used to study: (1) the effects of centrifugal distortion on the transition frequencies and strengths of the nu sub 2 band of H2S, and (2) nuclear quadrupole hyperfine structure in the 1-0 band of HI. A total of 126 line frequencies and 94 line strengths in the nu sub 2 band of H2S were measured. The average accuracy of the line frequency measurements was + or - 0.0016 cm. The line strengths were measured to an average accuracy of about 3 percent. The effect of the finite spectral width of the diode laser on the measurement of line strengths is discussed. The observed H2S line frequencies were fit to Watson's AS and NS reduced Hamiltonian in both the Ir and IIIr coordinate representations in order to determine the best set of rotation distortion constants for the upper state of the nu sub 2 band. Comparisons of the observed line strengths in this band to rigid rotor line strengths are also presented. Nuclear quadrupole hyperfine structure in the low J lines of the 1-0 band of HI was observed. The upper vibrational state nuclear quadrupole coupling constant, determined from the observed splittings, was -1850 MHz + or - 12 MHz or 1.2 percent + or - 0.7 percent larger than the ground state coupling constant.

Strow, L. L.↗
NASA NTRS1982

A monolithic lead sulfide-silicon MOS integrated-circuit structure

A technique is developed for directly integrating infrared photoconductive PbS detector material with MOS transistors. A layer of chromium, instead of aluminum, is deposited followed by a gold deposition in order to ensure device survival during the chemical deposition of the PbS. Among other devices, a structure was fabricated and evaluated in which the PbS was directly coupled to the gate of a PMOS. The external bias, load, and source resistors were connected and the circuit was operated as a source-follower amplifier. Radiometric evaluations were performed on a variety of different MOSFETs of different geometry. In addition, various detector elements were simultaneously fabricated to demonstrate small element capability, and it was shown that elements of 25 x 25 microns could easily be fabricated. Results of room temperature evaluations using a filtered 700 K black body source yielded a detectivity at peak wavelength of 10 to the 11th cm (root Hz)/W at 100 Hz chopping frequency.

Jhabvala, M. D.↗
NASA NTRS1985

Microbial colonization and growth on metal sulfides and other mineral surfaces

To determine whether a bacterial film forms on sulfur minerals in situ, various sulfur containing and other minerals were incubated in Penitencia Creek. The rate of cell growth and attachment within the surface microenvironment of mineral surfaces was also determined. To determine whether surfaces enriched with soluble sulfur substrates (cysteine, glutathione, thioglycolate, sulfite, and thiosulfate) increased the rate of growth or attachment of natural communities, membrane enrichments were incubated. These rates were determined as described by Caldwell et al. (1981, 1983). The growth of Pseudomonas fluorescens, a heterotrophic sulfur oxidizer, was studied in batch cell suspensions and in continuous culture. In batch culture the cells were oxygen limited (growth rate 0.33 per hour under oxygen limitations and 0.52 per hour when vigorously aerated). Growth within the film was glucose limited. Several behavioral phenomena were observed for cells growing within the hydrodynamic boundary layer. Despite a flow of 10 cm per second in the environment, the bacteria were able to move freely in both directions within the hydrodynamic boundary layer.

Caldwell, D.↗
NASA NTRS1985

Sulfide and sulfate saturation in hydrous silicate melts

A series of hydrothermal experiments was performed over a wide range of pressures, temperatures, oxygen fugacities, and melt FeO content, in order to examine the effects of physical changes on sulfur solubility in fractionated hydrous silicate melts. On the basis of the experimental results, it is concluded that upper crustal oxidation-reduction reactions and crystal fractionation processes may exert considerable influence on the amount of sulfur contained in magmas erupted at the surface. The application of the experimental results to investigations of volatile transport and volcanic degassing processes on the earth, Venus, and Mars is discussed

Carroll, M. R.↗
NASA NTRS1985

Thermoelectric properties of lanthanum sulfide

The Seebeck coefficient, electrical resistivity, thermal conductivity, and Hall effect have been studied in gamma-phase La(3-x)S4(LaS/y/) for compositions with x in the range from 0.04 to 0.3 (y in the range from 1.35 to 1.48) in order to ascertain its suitability for high-temperature (300 to 1400 K) thermoelectric energy conversion. In this temperature and composition range the material behaves as an extrinsic semiconductor whose degenerate carrier concentration is controlled by the stoichiometric ratio of La to S. A maximum figure-of-merit (Z) of approximately 0.0005 per K at a composition x = 0.3, y = 1.48 (LaS/1.48/) was obtained.

Wood, C.↗