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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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NASA NTRS1975

Selected Theoretical Studies Group contributions to the 14th International Cosmic Ray conference

The galactic distribution of H2 was studied through gamma radiation and through X-ray, optical, and infrared absorption measurements from SAS-2 and other sources. A comparison of the latitude distribution of gamma-ray intensity with reddening data shows reddening data to give the best estimate of interstellar gas in the solar vicinity. The distribution of galactic cosmic ray nucleons was determined and appears to be identical to the supernova remnant distribution. Interactions between ultrahigh energy cosmic-ray nuclei and intergalactic photon radiation fields were calculated, using the Monte Carlo method.

Source record↗
NASA NTRS1975

Emission-line strengths and the chemical compositions of quasi-stellar objects

Estimates of emission-line strengths in 160 QSOs are listed. They are used, together with those for 60 objects published earlier, to compile a table of rest-frame equivalent widths for a composite QSO containing 28 lines seen in objects with z from 0.06 to 3.53. Models are computed for matter partially filling a spherical volume, ionized by ultraviolet flux from a central object and optically thick with absorption from heavy elements taken into account. Constant temperature and density are taken for the He II region, where most of the important lines are emitted. Allowance is made for lower and higher temperatures in the H I and He III regions. Emergent emission-line equivalent widths are computed and compared with the observations. An abnormally low helium abundance is not needed to achieve a fit, since the only anomalously weak line is He II 4686 A whose upper level may be depopulated by stimulated emission of He II 1215 A caused by very strong L-alpha 1216 A flux.

Chan, Y.-W. T.↗
NASA NTRS1976

H2 molecules and the intercloud medium

The paper discusses expected column densities of H2 in the intercloud medium and the possible use of molecules as indicators of intercloud physical conditions. Molecule formation by the H(-) process and on graphite grains is treated, and it is shown that the Barlow-Silk hypothesis of a 1-eV semichemical hydrogen-graphite bond leads to a large enhancement of the intercloud molecule-formation rate. Rotational-excitation calculations are presented for both cloud and intercloud conditions which show, in agreement with Jura (1975), that the presently observed optically thin H2 absorption components are more likely to originate in cold clouds than in the intercloud medium.

Hill, J. K.↗
NASA NTRS1977

An optical catalog of quasi-stellar objects

A catalog containing the basic optical information on all QSOs which have been certainly identified, meaning that redshifts have been measured (complete to August 1976), is given. Included are the coordinate designations, other names, equatorial coordinates, visual magnitudes, (U-B) and (B-V) colors, emission-line redshifts, emission lines detected in the optical spectrum, absorption-line redshifts, and references for finding charts, absorption- and emission-line redshifts, and photometry and polarimetry for 633 QSOs and four BL Lacertae objects. Cross-reference tables are provided for finding coordinate designations of objects known by noncoordinate names.

Burbidge, G. R.↗
NASA NTRS1979

Measuring moisture in the atmosphere

Report describes instruments for measuring moisture in air by categorizing instruments according to their thermodynamic, hygroscopic, condensation, absorption, diffusion, and optical properties.

Johnson, D. L.↗
NASA NTRS1979

Theory of the intercluster medium

A set of computer models for the evolution of intercluster matter (ICM) in expanding cosmologies which includes processes of electron impact ionization/excitation, radiative and dielectronic recombination, thermal bremsstrahlung, Compton scattering, and photoionization is presented. The thermal, ionization, and excitation histories of major constituents were found as functions of time, and predictions of emission spectra, the possible distortions of the cosmic 3 K microwave background, and optical depths of absorption troughs in QSO continua at various redshifts were obtained. It is concluded that the present Friedmann cosmology can be dominated by hot intercluster matter which would contain H and He in their cosmic ratio and traces of heavier elements. For a narrow range of parameters it is possible to generate cosmologies with a closure density of ICM which do not exceed the diffuse X-ray measurements. In open cosmologies distortion of the 3 K microwave background occurs, while closed cases show negligible change from the unperturbed spectrum.

Sherman, R. D.↗
NASA NTRS1980

The discovery of an 81 minute modulation of the X-ray flux from 2A0311-227

The X-ray flux from 2A0311-227 was modulated at the 81 min orbital period of its optical counterpart. An absorption dip with N sub H equivalent to 5 x 10 to the 22nd power H atoms per square cm was observed at magnetic phase 0.42. It was interpreted as the accretion column of a magnetic white dwarf passing in front of the X-ray source. The spectrum was thermal with a temperature of 18 keV and a 300 eV equivalent width iron line at 6.6 keV.

White, N. E.↗
NASA NTRS1981

An 81 minute modulation of the X-ray flux from 2A 0311-227

It is demonstrated that the X-ray flux from 2A 0311-227 is modulated at the 81 minute orbital period of its optical counterpart. An absorption dip with N sub H approximately equal to 5 x 10 to the 22nd H atoms per sq cm is observed at magnetic phase 0.42 that is interpreted as the accretion column of a magnetic white dwarf passing in front of the X-ray source. The spectrum is thermal with a temperature of 18 keV and a 300 eV equivalent-width iron line at 6.6 keV.

White, N. E.↗
NASA NTRS1981

The role of geological surfaces in determining visible-near infra red spectral signatures

The goal of the study described here is to determine new criteria for improved target discrimination in areas of hydrothermal mineralization. It is noted that the portion of materials, that is, geological surfaces detected by sensing devices, must be accurately determined before elemental and mineralogical characterization. The depth from which visible-near infrared radiation is reflected from target surfaces depends on composition and fabric. Reflectance spectra are obtained from binary mixtures of hematite, goethite, kaolinite and montmorillonite with a reflecting sphere spectrometer over a wavelength range of 400-2500 nm. The reflection (or absorption) intensity is plotted vs. the sample thickness (determined by scanning electron microscopy) to determine the sample thickness at which absorption saturates. The optical depth is seen to vary as a function of mineralogy and wavelength. In general, the maximum depth from which reflection features are discerned is from 12 to 47 microns measured in the visible-near infrared spectral region.

Sommer, S. E.↗
NASA NTRS1982

The photochemistry and dynamics of a dusty cometary atmosphere

The solving of a simultaneous set of differential equations representing conservation of number density, momentum, and energy together with solar radiation transfer in the streams which result in photolytic processes and the heating of the nucleus yields a self-consistent solution of the dynamical and thermal structure of an H2O-dominated two-phase dusty gas cometary atmosphere. Two models are considered for the transfer of solar radiation through the circumnuclear dust halo. The first considers only the direct extinction by the dust, and in the second the diffuse radiation field due to multiple scattering by the dust halo, which compensates for radiation removed by direct absorption when the optical depth is near unity, is approximated by neglecting the attenuation of radiation given off by the dust. It is shown that while dust attenuation has a strong effect on the H2O production rate, it also increases the electron density in the inner coma over the unattenuated case.

Marconi, M. L.↗
NASA NTRS1983

The unique cometary nebula Parsamian 13

Parsamian 13 is found to be a cometary nebula, with a deeply embedded star suffering strong absorption by silicate grains. A feature near 2.7 microns, attributed to absorption by terminal OH groups, may represent the first detection in an astrophysical environment of water ice grains diluted by another molecule, for example by CO. The bolometric luminosity suggests that this star is either an extremely young T Tauri star or an evolved low-mass star, now a red giant, high on its convective track. Most unusual is the presence of cold (50 K) TiO gas in sufficient abundance to show in absorption in the optical and very near-infrared regions; this material probably represents very recently expelled photospheric layers.

Cohen, M.↗
NASA NTRS1984

The Smallest Sizes of Diffuse Interstellar Clouds

By observing the difference in optical depths between absorption spectra toward the two components of double sources, the variations in opacity over lengths of less than 0.1 up to 10 pc inside diffuse interstellar clouds were measured. Significant variations were detected on scales larger than about 0.2 pc, but not less. This may represent the minimum size for diffuse cloud structure. By comparing the variations of Gaussian fitted line parameters, it was found that variations in the internal velocity field of diffuse clouds explain the data better than tiny independent cloudlets.

Dickey, J. M.↗
NASA NTRS1987

An upper limit on the sizes of shepherding satellites at Saturn's ring G

An accurate analytical theory of the absorption of energetic magnetospheric particles by an inert satellite is developed for the case in which the radius b of the satellite is much less than the equatorial gyroradius r(g) of the particles and in which r(g) is in turn much less than the radius r of the satellite's orbit. In previous interpretations of Pioneer 11 observations, an estimate of the lifetime against absorption of energetic protons at Saturn's ring G has been made. This lifetime is used in the framework of the absorption theory to establish an upper limit on the sizes of shepherding satellites associated with the ring. The resulting upper limit, ignoring the absorption of the optically observed particulate matter, is given for an assemblage of N satellites of various radii. It is noted that ring G lies outside the Roche limit. No shepherding satellites at ring G were detected optically by Voyagers 1 and 2, and the searches were not comprehensive in longitudinal coverage.

Van Allen, James A.↗
NASA NTRS1987

Element abundances in the interstellar atomic material

In the interstellar medium, a significant fraction of the free atoms for elements heavier than helium must have condensed into solids, in the form of small, interstellar dust grains. Observations of optical and ultraviolet absorption lines in the spectra of hot stars indicate that the depletions below the cosmic abundances of various elements range from almost none at all to a factor of 0.0001 and seem to be enhanced along lines of sight with higher mean density. Other methods of measuring abundances confirm the absorption line results. The available evidence supports the notion that the grains form in both the atmospheres of cool stars and in dense interstellar clouds, and they are destroyed by shocks which frequently pass through the low density gas.

Jenkins, Edward B.↗
NASA NTRS1989

Comparative thermal analysis of the space station Freedom photovoltaic deployable boom structure using TRASYS, NEVADA, and SINDA programs

The proposed Space Station Photovoltaic Deployable Boom was analyzed for operating temperatures. The boom glass/epoxy structure design needs protective shielding from environmental degradation. The protective shielding optical properties (solar absorptivity and emissivity) dictate the operating temperatures of the boom components. The Space Station Boom protective shielding must also withstand the effects of the extendible/retractable coiling action within the mast canister. A thermal analysis method was developed for the Space Station Deployable Boom to predict transient temperatures for a variety of surface properties. The modeling procedures used to evaluate temperatures within the boom structure incorporated the TRASYS, NEVADA, and SINDA thermal analysis programs. Use of these programs led to a comparison between TRASYS and NEVADA analysis methods. Comparing TRASYS and NEVADA results exposed differences in the environmental solar flux predictions.

Baumeister, Joseph F.↗
NASA NTRS1988

Lidar atmospheric sounder and altimetry for the Earth Observing System (EOS) satellite

The NASA Space Station Program includes development of a polar orbiting platform as part of the Earth Observing System (EOS) Program. A lidar facility is in turn being developed for the EOS polar platforms to make atmospheric science measurements utilizing techniques of laser atmospheric backscatter (optical radar), Differential Absorption Lidar (DIAL) and altimetry. The science for this facility has been developed by the Lidar Atmospheric Sounder and Altimetry (LASA) panel for the Earth Observing System and will be addressed in an Announcement of Opportunity which will be released early in 1988 to solicit science proposals and experiment proposals for the EOS missions.

Woerner, Charles V.↗
NASA NTRS1988

A conceptual design study for the EOS Lidar Atmospheric Sounder and Altimeter facility

A preliminary design study is presented for the Lidar Atmospheric Sounder and Altimeter (LASA), an active remote sensor for the Earth Observing System. LASA is designed to measure the global vertical distributions of aerosols, cloud top heights, atmospheric trace gases, atmospheric temperature and pressure, and the height of the PBL. The measurements are made using optical radar, differential absorption lidar, and laser altimetry. An experiment proposed for the LASA facility, the EOS Atmospheric Global Lidar Experiment (EAGLE) is described in detail. The EAGLE program is planned to determine aerosol and cloud distributions, water vapor concentrations, and temperature profiles over the troposphere and aerosol distribution over the stratosphere. The measurement techniques, receiver system, and transmitter for the EAGLE program are examined and the conceptual design of the EAGLE experiment and the LASA/EAGLE interface is outlined.

Mauldin, Lemuel E., III↗
NASA NTRS1989

Comparative thermal analysis of the Space Station Freedom photovoltaic deployable boom structure using TRASYS, NEVADA, and SINDA programs

The proposed Space Station Photovoltaic Deployable Boom was analyzed for operating temperatures. The boom glass/epoxy structure design needs protective shielding from environmental degradation. The protective shielding optical properties (solar absorptivity and emissivity) dictate the operating temperatures of the boom components. The Space Station Boom protective shielding must also withstand the effects of the extendible/retractable coiling acting within the mast canister. A thermal analysis method was developed for the Space Station Deployable Boom to predict transient temperatures for a variety of surface properties. The modeling procedures used to evaluate temperatures within the boom structure incorporated the TRASYS, NEVADA, and SINDA thermal analysis programs. Use of these programs led to a comparison between TRASYS and NEVADA analysis methods. Comparing TRASYS and NEVADA results exposed differences in the environmental solar flux predictions.

Baumeister, Joseph F.↗