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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Spectral properties /0.04 to 0.75 microns/ of soils exposed at the Viking 1 landing site

The bidirectional reflectance and photometric function (Hapke, 1981) was determined for seven patches of soil located near the Viking Lander 1 spacecraft. The soil photometric function has a prominent opposition effect in addition to a phase function that is strongly backscattering. The ratio of reflectances at a 1 deg phase angle to that at a 10 deg phase angle averages 1.25, 1.24, and 1.19 for blue, green, and red wavelengths respectively. The photometric function has a wavelength dependence, which causes color ratios to vary by up to 33% as a function of phase angle. Estimates of soil reflectance at a 5 deg phase angle averaged over the blue and green passbands of the Viking Lander cameras are 0.11 and 0.17, respectively, while estimates over the red channel range from 0.30 to 0.39. Brightness and color variations within the soil can be correlated with particle size, finer-grained soil being brighter and redder than coarser-grained soil. Lander soils, homogeneous in nature, are typical of brighter soils covering a large portion of the Martian surface.

Guinness, E. A.↗
NASA NTRS1982

Failure mechanisms of thermal barrier coatings exposed to elevated temperatures

The failure of a ZrO2-8%Y2O3/Ni-14% Al-0.1% Zr coating system on Rene 41 in Mach 0.3 burner rig tests was characterized. High flame and metal temperatures were employed in order to accelerate coating failure. Failure by delamination was shown to precede surface cracking or spalling. This type of failure could be duplicated by cooling down the specimen after a single long duration isothermal high temperature cycle in a burner rig or a furnace, but only if the atmosphere was oxidizing. Stresses due to thermal expansion mismatch on cooling coupled with the effects of plastic deformation of the bond coat and oxidation of the irregular bond coat are the probable life limiting factors. Heat up stresses alone could not fail the coating in the burner rig tests. Spalling eventually occurs on heat up but only after the coating has already failed through delamination.

Miller, R. A.↗
NASA NTRS1981

Delayed darkening of radiation-exposed radiochromic dye dosimeters

Experiments have verified the existence of considerable delayed darkening in FWT-60 dosimetry films that may, depending on relative humidity, last for several hours. The amount of delayed darkening depends very strongly on the relative humidity at which the films are equilibrated before irradiation. It is pointed out that the delayed darkening effect must be taken into account before any meaningful dosimetric measurements may be made using these nylon-based thin dosimetry films. The particular radiation-sensitive compound used in the FWT-60 films is the hexahydrosyethyl pararosanaline cyanide with the Dupont nylon resin, Elvamide 8061, which forms the host matrix of a solid-state solution.

Danchenko, V.↗
NASA NTRS1982

Altered auditory function in rats exposed to hypergravic fields

The effect of an orthodynamic hypergravic field of 6 G on the brainstem auditory projections was studied in rats. The brain temperature and EEG activity were recorded in the rats during 6 G orthodynamic acceleration and auditory brainstem responses were used to monitor auditory function. Results show that all animals exhibited auditory brainstem responses which indicated impaired conduction and transmission of brainstem auditory signals during the exposure to the 6 G acceleration field. Significant increases in central conduction time were observed for peaks 3N, 4P, 4N, and 5P (N = negative, P = positive), while the absolute latency values for these same peaks were also significantly increased. It is concluded that these results, along with those for fields below 4 G (Jones and Horowitz, 1981), indicate that impaired function proceeds in a rostro-caudal progression as field strength is increased.

Jones, T. A.↗
NASA NTRS1984

Growth and differentiation of mammalian embryonic tissues exposed to hypergravity in vivo and in vitro

In about 10 years or so, men and women from Earth will be long-term inhabitants of a space station aboard which plants and animals will be growing and developing in gravities other than that of Earth. The effect of gravitational changes on development was examined. It is indicated that differentiation is speeded up under excess G and slowed in low or null G. The effects of exposure to excess gravity on fusion of the embryonic mouse secondary palate were studied. During fusion, the palatal shelves first adhere by means of glycoproteins appearing along the medial epithelial edge (MEE). The contacting epithelia then reorganize and undergo programmed cell death, allowing the underlying mesenchymes to come in contact. The process of cell death occurs in vitro at about the same rate that it occurs in vivo.

Duke, P. J.↗
NASA NTRS1984

Space-exposed experiment developed for students

This experiment will offer students the opportunity to evaluate the survivability of seeds stored in the space environment and to determine possible mutants and changes in the mutation rate which may occur. The objectives of this experiment are to involve a very large number of students in a national project to generate interest in science and related disciplines; to offer students from the elementary through the university level an opportunity to participate in a first-hand experiment with materials flown in space; to permit active involvement in classroom experiment design, decision making, data gathering, and comparison of results; and to emphasize a multidisciplinary approach to the project involving subject areas other than science.

Grigsby, D. K.↗
NASA NTRS1984

Patterns of behavior in lodgings exposed to traffic noise

Threshold values for public services interferent on the attenuation to noise nuisance were defined. Daily life at home was described and collected on the use of residences, the effects of noise on health and sleep, and the incidence of running away from home. A correlation was made with the equipment and noise insulation of homes. It is shown that there are behavior patterns in the modification of considerable manner in the way of life for people who live in apartments and in individual houses, above 66 dB during daytime.

Lambert, J.↗
NASA NTRS1985

Lunar and Martian impact basins: Exposed records of terrestrial bombardment?

The unrecycled surfaces of the Moon, Mercury, and Mars preserve the very early history of impact bombardment and its effect on crustal evolution. Previous studies indicated that the post accretion impact flux by large bodies on Mars may have been dificient, but systematic studies recently have revealed that this deficiency is largely the result of active erosional and depositional processes during the first 0.8 by. Ancient Martian impact basins larger than 300 km in diameter are revealed by subtle but unequivocal topographic and structural control of drainage patterns. In addition, the largest basins have left a deep seated imprint of concentric and radial structural patterns that control the occurrence of most Martian volcanic and tectonic provinces. If 10(-6)/km(2) is considered to be a reasonable approximation for the density of impact basins ( 300 km) of the Moon and Mars, then the Earth should have recorded more than 500 impacts that resulted in basins larger than 300 km in diameter over its post accretion geologic history. If calibrated with the Moon, then most of these impacts occurred prior to 3.8 by.

Schultz, P. M.↗
NASA NTRS1984

Discoloration of poly(vinyl butyral) in cells exposed to real and simulated solar environments

The discoloration of poly(vinl butyral) (PVB) films used in solar cell modules is described. Transmission absorption, Fourier transformation IR absorption and atomic absorption spectroscopy as well as scanning electron microscopy were used for this study. The discoloration of the PVB has been found to be affected by oxygen, moisture, temperature and light. However, the most severe discoloration observed is clearly associated with the migration of positive silver ions, which can be accelerated in the presence of electric fields. The metallization is the source of the silver, and the data are consistent with an interfacial reaction between the silver and PVB followed by transport into the polymer.

Kim, Q.↗
NASA NTRS1984

Core temperature of tailless rats exposed to centrifugation

The role of the tail in the altered thermoregulation of rats during acute exposure to hypergravity was investigated, using groups of rats of two ages: 55 days (young) and 138 days (old). Rectal and foot temperature changes were measured in intact and tailless rats subjected to 1 h centrifugation of 2.8 G, with preceding (1 h) and following (1-3 h) 1 G periods. At 22 C, the loss of body heat from the tail per se does not measurably contribute to the hypothermia induced by hypergravity. However, the heat loss from the feet was greater in the tailless rats than in the intact rats from the young group of animals, although there was no significant difference between the tailless and intact rats in the old animal group. It is concluded that the inhibition of heat production is a significant factor in the hypothermia of centrifuged tailless rats, as it has been previously shown to be in the intact animals.

Monson, C. B.↗
NASA NTRS1986

Regulation of hematopoiesis in rats exposed to antiorthostatic hypokinetic/hypodynamia. II - Mechanisms of the 'anemia'

The cause of the red cell mass (RCM) deficit, which occurs in rats during suspenion, is investigated. The experimental conditions and procedures, in which male Sprague-Dawley rats are subjected to antiorthostatic hyypokinetic/hypodynamia and changes in RCM are monitored, are described. The influences of stress, reduced food and water consumption, and antiorhostatic posture on RCM are analyzed. Changes in body weight, RCM, radioiron incorporation, red blood cells (RBC), and reticulocytes, for the rats after head-down suspension are graphically presented; only the changes in RBC are related to the antiorthostatic posture. The data reveal that anemia is primarily caused by reduced food and water consumption and secondly by restricted movements.

Dunn, C. D. R.↗
NASA NTRS1987

Morphology of zirconia particles exposed to D.C. arc plasma jet

Zirconia particles were sprayed into water with an arc plasma gun in order to determine the effect of various gun operating parameters on their morphology. The collected particles were examined by XRD and SEM techniques. A correlation was established between the content of spherical (molten) particles and the operating parameters by visual inspection and regression analysis. It was determined that the composition of the arc gas and the power input were the predominant parameters that affected the melting of zirconia particles.

Zaplatynsky, Isidor↗
NASA NTRS1987

Mechanistic studies of polymeric samples exposed aboard STS 8

The early Shuttle flights and the attendant opportunity to deploy material samples to the near-Earth space environment, along well-defined trajectories and accompanied by detailed characterization of these samples prior to and following the flight exposure, have brought to light several novel phenomena associated with interaction of these materials with the space environment. JPL, in coordination with other NASA Centers, has carried out a research program to study the degradation and oxidation processes caused by interaction of these materials with atomic oxygen at an energy of 5 eV. In addition, energetic atomic oxygen is believed to be responsible for the shuttle glow first observed during the flight of STS-3. The shuttle glow phenomenon has been extensively studied and modeled because of its long-range potential impact on optical communication schemes and its more immediate impact on the Space Telescope. This report summarizes the results of certian material degradation and erosion experiments carried out aboard STS-8 between August 30, 1983 and September 5, 1983. Based on these data, a generic degradation model has been developed for common structural polymers.

Liang, Ranty H.↗
NASA NTRS1988

Exposed high-voltage source effect on the potential of an ionospheric satellite

A pulsed, high-voltage source, which is able to draw a current from the surrounding plasma, is seen to induce large changes in the potential of an ionospheric satellite (the Iowa Plasma Diagnostics Package flown on Space Shuttle flight STS-51F). This, in turn, may affect the operation of other instruments that use the chassis of the satellite as a ground for electrical circuits. The magnitude of the change in satellite potential is dependent upon both the orientation of the high-voltage source, relative to the plasma flow, and the characteristics of the high-voltage source. When the satellite is grounded to the Shuttle Orbiter, this effect is sufficient to change the potential of the Orbiter by a small, but noticeable, amount.

Tribble, A. C.↗
NASA NTRS1988

AVIRIS data characteristics and their effects on spectral discrimination of rocks exposed in the Drum Mountains, Utah: Results of a preliminary study

Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) data collected over a geologically diverse field site and over a nearby calibration site were analyzed and interpreted in efforts to document radiometric and geometric characteristics of AVIRIS, quantify and correct for detrimental sensor phenomena, and evaluate the utility of AVIRIS data for discriminating rock types and identifying their constituent mineralogy. AVIRIS data acquired for these studies exhibit a variety of detrimental artifacts and have lower signal-to-noise ratios than expected in the longer wavelength bands. Artifacts are both inherent in the image data and introduced during ground processing, but most may be corrected by appropriate processing techniques. Poor signal-to-noise characteristics of this AVIRIS data set limited the usefulness of the data for lithologic discrimination and mineral identification. Various data calibration techniques, based on field-acquired spectral measurements, were applied to the AVIRIS data. Major absorption features of hydroxyl-bearing minerals were resolved in the spectra of the calibrated AVIRIS data, and the presence of hydroxyl-bearing minerals at the corresponding ground locations was confirmed by field data.

Bailey, G. B.↗