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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

A multi-wavelength study of the peculiar galaxy NGC 2976

Researchers are currently studying NGC 2976 at many wavelengths to investigate the extent to which an interaction with M81 may have affected the star formation history of this galaxy. Here, researchers present observations of NGC 2976 made at 50 microns with the high resolution (CPC) instrument onboard Infrared Astronomy Satellite (IRAS) at 21-cm (both HI line and radio continuum) with the Westerbork Synthesis Radio Telescope (WSRT) and in the H alpha line with the Kitt Peak National Observatory (KPNO) 36 inch telescope. The far infrared emission is not centrally peaked as in other spirals (e.g., Wainscoat et al. 1987), but has obvious intensity peaks near the ends of the disk. The ionized gas as inferred from the H alpha observations, is largely confined to two large, symmetrically placed emission regions near the ends of the disk. Finally, the HI and 21-cm radio continuum emission also exhibit this strongly double-peaked structure. At all of the above wavelengths the emission peaks are roughly coincident and lie approx. 1.2 minutes to the NW and approx. 1.1 minutes to the SE of the optical center of this galaxy.

Tacconi, L. J.↗
NASA NTRS1991

NASA thesaurus aeronautics vocabulary

The controlled vocabulary used by the NASA Scientific and Technical Information effort to index documents in the area of aeronautics is presented. The terms comprise a subset of the 1988 edition of the NASA Thesaurus and its supplements issued through the end of 1990. The Aeronautics Vocabulary contains over 4700 terms presented in a hierarchical display format. In addition to aeronautics per se, the vocabulary covers supporting terminology from areas such as fluid dynamics, propulsion engineering, and test facilities and instrumentation.

Source record↗
NASA NTRS1990

The environments of Markarian galaxies

The extensively studied Markarian sample of 1500 ultraviolet excess galaxies contains many Seyfert, starburst, and peculiar galaxies. Using the 20 minute V plates obtained for the construction of the Hubble Space Telescope Guide Star Catalog, the authors investigated the morphologies of the Markarian galaxies and the environments in which they are located. The relationship between the types of nuclear activity and the morphologies and environments of the Markarian galaxies is discussed. The authors conclude that the type of nuclear activity present in the galaxies of the Markarian sample is not dependent on either the morphology or the local environment of the galaxy. This is not to imply that nuclear activity per se is not influenced by the environment in which the nucleus is located. Rather the type of nuclear activity (at least in the Markarian population) does not appear to be determined by the environment.

Mackenty, John W.↗
NASA NTRS1990

Signs of interaction of the NGC 1275 nucleus with the high-velocity system according to 0.7 sec seeing observations

The nucleus of the Seyfert galaxy NGC 1275 was observed in the B system on 1 December 1989 with seeing 0, 7 seconds using the Zeiss-1000 telescope on Mount Majdanak in Central Asia. Special methods of processing reveal low-contrast details. The nucleus and circumnucleus are stretched in NW-SE direction. There are two narrow filaments near the nucleus in position angles roughly 340 degrees and 320 degrees. The first is directed near the radio jet of the nucleus, the second has broken details curved to the NW or toward the high-velocity system of NGC 1275.

Dudinov, V. N.↗
NASA NTRS1990

Space vehicle propulsion systems: Environmental space hazards

The hazards that exist in geolunar space which may degrade, disrupt, or terminate the performance of space-based LOX/LH2 rocket engines are evaluated. Accordingly, a summary of the open literature pertaining to the geolunar space hazards is provided. Approximately 350 citations and about 200 documents and abstracts were reviewed; the documents selected give current and quantitative detail. The methodology was to categorize the various space hazards in relation to their importance in specified regions of geolunar space. Additionally, the effect of the various space hazards in relation to spacecraft and their systems were investigated. It was found that further investigation of the literature would be required to assess the effects of these hazards on propulsion systems per se; in particular, possible degrading effects on exterior nozzle structure, directional gimbals, and internal combustion chamber integrity and geometry.

Disimile, P. J.↗
NASA NTRS1991

A pointable, helicopter-based remote sensing data acquisition system for collecting bidirectional reflectance data

Discussed here is a new configuration of a helicopter-borne remote sensing system to support field measurements programs such as studies of forest decline damage associated with atmospheric deposition and the Forest Ecosystems Dynamics project. In this new configuration, the sensor payload is mounted externally on a hinged pallet located on the starboard side of the Bell Iroquois UH-1B (HUEY) helicopter. The sensor payload includes a set of bore-sighted instruments consisting of a Barnes Modular Multiband Radiometer (MMR), a Spectron Engineering (SE) 590 spectroradiometer, an Everest infrared temperature sensor, and a Sony CCD video camera with a 10x zoom lens. The system was tested and excellent data was acquired in 1990.

Williams, Darrel L.↗
NASA NTRS1990

Comparison of 7.5-minute and 1-degree digital elevation models

Two digital elevation models are compared for the Echo Mountain SE quadrangle in the Cascade Mountains of Oregon. Comparisons were made between 7.5-minute (1:24,000-scale) and 1-degree (1:250,000-scale) images using the variables of elevation, slope aspect, and slope gradient. Both visual and statistical differences are presented.

Isaacson, Dennis L.↗
NASA NTRS1989

Reflectance and transmittance of snow at high spectral resolution

A radiative-transfer model for the bidirectional reflectance-distribution function (BRDF) shows that snow is moderately anisotropic in the NIR wavelengths. Although the directional-hemispherical albedo of snow decreases as the grains become larger, the forward scattering also increases, with the result that the illumination and viewing geometry must be considered when interpreting physical properties of the surface layer of the snow pack from remote sensing data. Measurements of the BRDF and the transmittance for a variety of snow conditions were made throughout the winter and spring seasons with an SE-590 spectroradiometer, for wavelengths from 0.38 to 1.11 microns. Coincident with these, the surface grain properties were analyzed by stereological methods. A sphere with the same surface-to-volume ratio as the ice grains is used as the equivalent sphere.

Dozier, Jeff↗
NASA NTRS1990

Chemical studies of differentiated meteorites. I - Labile trace elements in Antarctic and non-Antarctic eucrites

Element contents of Ag, Au, Bi, Cd, Co, Cs, Ga, In, Rb, Sb, Se, Te, Tl, U, and Zn were analyzed, using RNAA, in 25 Antarctic and nine non-Antarctic eucrites to determine whether these two populations differ significantly in thermal history and derive from the same or different eucrite parent body. Data for these 15 elements indicate that basaltic Antarctic and non-Antarctic eucrite populations reflect the same genetic processes and, hence, come from the same parent asteroid.

Paul, Rick L.↗
NASA NTRS1991

Ordinary chondrites - Multivariate statistical analysis of trace element contents

The contents of mobile trace elements (Co, Au, Sb, Ga, Se, Rb, Cs, Te, Bi, Ag, In, Tl, Zn, and Cd) in Antarctic and non-Antarctic populations of H4-6 and L4-6 chondrites, were compared using standard multivariate discriminant functions borrowed from linear discriminant analysis and logistic regression. A nonstandard randomization-simulation method was developed, making it possible to carry out probability assignments on a distribution-free basis. Compositional differences were found both between the Antarctic and non-Antarctic H4-6 chondrite populations and between two L4-6 chondrite populations. It is shown that, for various types of meteorites (in particular, for the H4-6 chondrites), the Antarctic/non-Antarctic compositional difference is due to preterrestrial differences in the genesis of their parent materials.

Lipschutz, Michael E.↗
NASA NTRS1991

First results from the Faint Object Camera - Imaging the core of R Aquarii

The Faint Object Camera on the HST was pointed toward the symbiotic long-period M7e Mira variable R Aquarii, and very high resolution images of the inner core, mainly in the ionized oxygen emission lines in the optical, are reported. Both images show bright arcs, knots, and filaments superposed on a fainter, diffuse nebulosity extending in a general SW-NE direction from the variable to the edge of the field at 10 arcsec distance. The core is resolved in forbidden O III 5007 A and forbidden O II 3727 A into at least two bright knots of emission whose positions and structures are aligned with PA = 50 deg. The central knots appear to be the source of a continuous, well-collimated, stream of material extending out to 3-4 arcsec in the northern sector corresponding to a linear distance of about 1000 AU. The northern stream seems to bend around an opaque obstacle and form a spiral before breaking up into wisps and knots. The southern stream is composed of smaller, discrete parcels of emitting gas curving to the SE.

Paresce, F.↗
NASA NTRS1991

Hubble Space Telescope imaging of Eta Carinae

New high spatial resolution observations of the material around Eta Carinae, obtained with the Hubble Space Telescope Wide Field/Planetary Camera, are presented. The star Eta Carinae is one of the most massive and luminous stars in the Galaxy, and has been episodically expelling significant quantities of gas over the last few centuries. The morphology of the bright central nebulosity (the homunculus) indicates that it is a thin shell with very well defined edges, and is clumpy on 0.2 arcsec (about 10 to the 16th cm) scales. An extension to the northeast of the star (NN/NS using Walborn's 1976 nomenclature) appears to be a stellar jet and its associated bow shock. The bow shock is notable for an intriguing series of parallel linear features across its face. The S ridge and the W arc appear to be part of a 'cap' of emission located to the SW and behind the star. Together, the NE jet and the SW cap suggest that the symmetry axis for the system runs NE-SW rather than SE-NW, as previously supposed. Overall, the data indicate that the material around the star may represent an oblate shell with polar blowouts, rather than a bipolar flow.

Hester, J. J.↗
NASA NTRS1991

The stratospheric 4-day wave in NMC data

The observed characteristics of the 4-day eastward-moving wave 1 in the Southern Hemisphere polar winter stratosphere are surveyed using ten years of National Meteorological Center (NMC) geopotential height data. The 4-day wave is shown to be an ubiquitous feature in the Southern Hemisphere polar winter stratosphere and is usually prominent during July and August. Growth of the 4-day wave is characterized by two types of structures. Some episodes exhibit NW to SE phase tilts and a single high-latitude maximum. Others show NE to SW phase tilts during growth and a high-latitude maximum out of phase with a secondary lower-latitude maximum. Stability analyses show that all characteristics of the first type of episode are consistent with barotropic instability of the stratospheric polar night jet. Analyses of climatological fields suggest that characteristics of the second type of episode may be consistent with barotropic instability of the double-peaked mesospheric jet.

Manney, Gloria L.↗
NASA NTRS1991

Timing and formation of wrinkle ridges in the Tyrrhena Patera Region of Mars

Wrinkle ridges are distinctive linear to curvilinear arches topped by crenulated ridges and have been identified on the Moon, Mercury, and Mars. The presence of wrinkle ridges on other planetary surfaces has been used as a criterion for identifying volcanic plains. Recently, due to the presence of lava flow lobes and leveed channels, Greeley and Crown identified an area within Hesperia Planum as a flank flow unit associated with Tyrrhena Patera. Hesperia Planum surrounds Tyrrhena Patera and embays the eroded shield of the volcano to the north and south. The Tyrrhena Patera flank flow unit extends approx. 1000 km from the summit caldera to the southwest. More than 55 wrinkle ridges have been identified on this flank flow unit. The relationships between the lava flows and wrinkle ridges within the flank flow unit allow relative ages to be determined. Wrinkle ridges are classified as post flow if flow lobes appear to arch over the rises undeformed, with no evidence of flow ponding on the upstream side of the ridge, or of flows breaching the rises. Wrinkle ridges within Hesperia Planum and Tyrrhena Patera flank flow unit that trend NW-SE appear younger than the flank flow unit.

Porter, Tracy K.↗
NASA NTRS1992

Issues in NASA program and project management

This volume is the fifth in an ongoing series on aerospace project management at NASA. Articles in this volume cover: an overview of the project cycle; SE&I management for manned space flight programs; shared experiences from NASA Programs and Projects - 1975; cost control for Mariner Venus/Mercury 1973; and the Space Shuttle - a balancing of design and politics. A section on resources for NASA managers rounds out the publication.

Hoban, Francis T.↗
NASA NTRS1992

Computational studies of metal-metal and metal-ligand interactions

The geometric structure of Cr(CO)6 is optimized at the modified coupled-pair functional (MCPF), single and double excitation coupled-cluster (CCSD) and CCSD(T) levels of theory (including a perturbational estimate for connected triple excitations), and the force constants for the totally symmetric representation are determined. The geometry of Cr(CO)5 is partially optimized at the MCPF, CCSD and CCSD(T) levels of theory. Comparison with experimental data shows that the CCSD(T) method gives the best results for the structures and force constants, and that remaining errors are probably due to deficiencies in the one-particle basis sets used for CO. A detailed comparison of the properties of free CO is therefore given, at both the MCPF and CCSD/CCSD(T) levels of treatment, using a variety of basis sets. With very large one-particle basis sets, the SSCD(T) method gives excellent results for the bond distance, dipole moment and harmonic frequency of free CO. The total binding energies of Cr(CO)6 and Cr(CO)5 are also determined at the MCPF, CCSD and CCSD(T) levels of theory. The CCSD(T) method gives a much larger total binding energy than either the MCPF or CCSD methods. An analysis of the basis set superposition error (BSSE) at the MCPF level of treatment points out limitations in the one-particle basis used here and in a previous study. Calculations using larger basis sets reduced the BSSE, but the total binding energy of Cr(CO)6 is still significantly smaller than the experimental value, although the first CO bond dissociation energy of Cr(CO)6 is well described. An investigation of 3s3p correlation reveals only a small effect. The remaining discrepancy between the experimental and theoretical total binding energy of Cr(CO)6 is probably due to limitations in the one-particle basis, rather than limitations in the correlation treatment. In particular an additional d function and an f function on each C and O are needed to obtain quantitative results. This is underscored by the fact that even using a very large primitive se (1042 primitive functions contracted to 300 basis functions), the superposition error for the total binding energy of Cr(CO)6 is 22 kcal/mol at the MCPF level of treatment.

Barnes, Leslie A.↗
NASA NTRS1990

A differential absorption technique to estimate atmospheric total water vapor amounts

Vertically integrated water-vapor amounts can be remotely determined by measuring the solar radiance reflected by the earth's surface with satellites or aircraft-based instruments. The technique is based on the method by Fowle (1912, 1913) and utilizes the 0.940-micron water-vapor band to retrieve total-water-vapor data that is independent of surface reflectance properties and other atmospheric constituents. A channel combination is proposed to provide more accurate results, the SE-590 spectrometer is used to verify the data, and the effects of atmospheric photon backscattering is examined. The spectrometer and radiosonde data confirm the accuracy of using a narrow and a wide channel centered on the same wavelength to determine water vapor amounts. The technique is suitable for cloudless conditions and can contribute to atmospheric corrections of land-surface parameters.

Frouin, Robert↗
NASA NTRS1991

Chemical studies of H chondrites. III - Regolith evolution of the Fayetteville chondrite parent

Radiochemical neutron concentration analysis was used to determine Ag, Au, Bi, Cd, Co, Cs, Ga, In, Rb, Sb, Se, Te, Tl, and Zn contents in consortium samples of solar gas and track-rich dark matrix. Data obtained confirmed that the matrix is chemically homogeneous. Most dark clasts had similar mean trace element concentrations as the matrix but were compositionally much more heterogeneous. It is concluded that material incorporated with soil and compacted to form the dark portion of Fayetteville included soil-melt, the odd C2M fragment, and dark and light clasts which escaped comminution.

Xiao, Xiaoyue↗