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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 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Mesospheric heating due to convectively excited gravity waves - A case study

A series of at least daily rocket soundings of the mesosphere at Wallops Island, Virginia (37 deg 50 min N, 75 deg 29 min W), in August and September 1976 reveal near simultaneity between rapid temperature rises and tropospheric convection in the form of squall lines. A multilevel numerical model is developed to test the hypothesis that the convection and warmings are related via internal gravity waves. Some features of the model are (1) the wave energy source is expressed in terms of cloud-base mass flux, plume diameter and buoyant updraft velocity; (2) the turbulent-viscous gravity wave dissipation is limited to above 55 km and is parameterized on the basis of findings by Hines (1965). Significant findings are: (1) mesospheric heating rates of the same order as those observed result for reasonable values of the convective parameters and in situ dissipation time scales; (2) only gravity waves confined to a well-defined wavelength and frequency interval are able to propagate upward to mesospheric altitudes; (3) heating rates are strongly dependent on plume diameter and updraft velocity; and (4) for a given cloud-base mass flux, heating rates are optimized for a plume updraft velocity of 10 m/s.

Clark, J. H. E.↗
NASA NTRS1981

Observations and models of inertial waves in the deep ocean

A study of the structure of the inertial peak in deep ocean kinetic energy is presented, based on records taken from Polymode arrays deployed in the western North Atlantic Ocean. Results are interpreted in terms of both local sources and turning point effects on internal waves generated at lower latitudes, and it is found that three classes of environment and their corresponding spectra emerge from peak height variations: (1) the 1500-m level near the Mid-Atlantic Ridge, with the greatest peak height of 18 dB; (2) the upper and deep ocean over rough topography and the deep ocean underneath the Gulf Stream, with the intermediate peak height of 11.5 dB; and (3) the deep ocean over smooth topography, with the lowest peak height of 7.5 dB. Using the globally valid wave functions obtained by Munk and Phillips (1968), frequency spectra near f are calculated numerically. The model is latitudinally dependent, with the frequency shift and bandwidth of the inertial peak decreasing with latitude.

Fu, L.-L.↗
NASA NTRS1983

Current collection from the space plasma through defects in high voltage solar array insulation

For spacecraft operation in the near Earth environment, solar cell arrays constitute the major source of reliable long term power. Optimization of mass and power efficiency results in a general requirement for high voltage solar arrays. The space plasma environment, though, can result in large currents being collected by exposed solar cells. The solution of a protective covering of transparent insulation is not a complete solution, inasmuch as defects in the insulation result in anomalously large currents being collected through the defects. Tests simulating the electron collection from small defects in an insulation have shown that there are two major collection modes. The first mode involves current enhancement by means of a surface phenomenon involving the surrounding insulator. In the second mode the current collection is enhanced by vaporization and ionization of the insulators materials, in addition to the surface enhancement of the first mode. A model for the electron collection is the surface enhanced collection mode was developed. The model relates the secondary electron emission yield to the electron collection. It correctly predicts the qualitative effects of hole size, sample temperature and roughening of sample surface. The theory was also shown to predict electron collection within a factor of two for the polymers teflon and polyimide.

Stillwell, R. P.↗
NASA NTRS1984

A radiometric Bode's Law: Predictions for Uranus

The magnetospheres of three planets, Earth, Jupiter, and Saturn, are known to be sources of intense, nonthermal radio bursts. The emissions from these sources undergo pronounced long term intensity fluctuations that are caused by the solar wind interaction with the magnetosphere of each planet. Determinations by spacecraft of the low frequency radio spectra and radiation beam geometry now permit a reliable assessment of the overall efficiency of the solar wind in stimulating these emissions. Earlier estimates of how magnetospheric radio output scales with the solar wind energy input must be revised greatly, with the result that, while the efficiency is much lower than previously thought, it is remarkably uniform from planet to planet. The formulation of a radiometric Bode's Law from which a planet's magnetic moment is estimated from its radio emission output is presented. Applying the radiometric scaling law to Uranus, the low-frequency radio power is likely to be measured by the Voyager 2 spacecraft as it approaches this planet.

Desch, M. D.↗
NASA NTRS1984

Hy-wire measurements of atmospheric potential

A method for directly measuring the electric potential drop across the lowest portion of the atmosphere by using an apparatus called Hy-wire is described. The Hy-wire system consists of a long, high-voltage, insulated conductor connected at the top to a wire-mesh braid and terminated at the bottom inside a large-diameter corona ball mounted on 1 m Teflon legs. The system impedance is near 10 billion ohms, while the grounded mode, Hy-wire draws about 10 micro-a at 500 m altitude. Around-the-clock measurements with characteristic peaks near 1530 and 1900 UT of potentials near 125,000 volts are presented, with total daily average potential near 90,000 volts at 507 m altitude. The experimental weather conditions varied from clear to local fog, except that there was only trace precipitation. The data have been interpreted in terms of the possible source of the potential variations; neither a local nor a global source is clearly indicated.

Holzworth, R. H.↗
NASA NTRS1984

Implications of Observed Frequencies of Solar P Modes

A preliminary comparison is made of the observed frequencies of 5 min P modes with theoretical frequencies for a traditional solar model. The differences between observations and theory can be understood qualitatively in terms of two separate sources of error in the frequency calculation, one near the solar surface and the other at the base of the convection zone. There is no indication of errors in the deep interior of the model.

Christensen-Dalsgaard, J.↗
NASA NTRS1985

Germanium and lead: Significant differences between meteoritic and photospheric abundances?

The order of the Galactic cosmic ray source (GCRS) composition in terms of first ionization potential (FIP) was examined. For most elements, the degree of volatility is (positively) correlated with the value of the FIP, so that it is not easy to distinguish a correlation of GCRS abundances anomalies with FIP from a correlation with volatility. Only a few permit to distinguish between the two kinds of ordering: if they are depleted relative to refractory metals, volatility must be relevant, if not, FIP is relevant. Among them Cu and Zn would seem to favor FIP. Among the best indicators are Ge and Pb. The abundance anomalies in GCRS are defined relative to a standard which, for the heavy elements concerned, is commonly taken as C1 Carbonaceous Chondrites. Photospheric abundances are more directly representative of the protosolar nebula, and hence of ordinary local galactic (LG) matter. The Ge and Pb reference abundance determinations in the Photosphere and in C1 meteorites are examined and their relevance to the problem with FIP vs. volatility in GCRs is discussed.

Grevesse, N.↗
NASA NTRS1986

The Kolar Schist Belt: A possible Archaean suture zone

The Kolar Schist Belt represents a N-S trending discontinuity in the structures, lithologies, and emplacement and metamorphic ages of late Archean gneisses. The suggestion of a much older basement on the west side of the belt is not seen on the east. Within the schist belt amphibolites from each side have distinctly different chemical characteristics, suggesting different sources at similar mantle depths. These amphibolites were probably not part of a single volcanic sequence, but may have formed about the same time in two completely different settings. Could the amphibolites with depleted light REE patterns represent Archean ocean floor volcanics which are derived from a mantle source with a long term depletion of the light REE? Why are the amphibolites giving an age which may be older than the exposed gneisses immediately on either side of the belt? These results suggest that it is necessary to seriously consider whether the Kolar Schist Belt may be a suture between two late Archean continental terranes.

Hanson, G. N.↗
NASA NTRS1985

Very high potassium (VHK) basalt - Complications in mare basalt petrogenesis

The first comprehensive report on the petrology and geochemistry of Apollo 14 VHK (Very High Potassium) basalts and their implications for lunar evolution is presented. The reported data are most consistent with the hypothesis that VHK basalts formed through the partial assimilation of granite by a normal low-Ti, high-Al mare basalt magma. Assimilation was preceded by the diffusion-controlled exchange of alkalis and Ba between basalt magma and the low-temperature melt fraction of the granite. Hypotheses involving volatile/nonvolatile fractionations or long-term enrichment of the source regions in K are inconsistent with the suprachondritic Ba/La ratios and low initial Sr-87/Sr-86 ratios of VHK basalt. An important implication of this conclusion is that granite should be a significant component of the lunar crust at the Apollo 14 site.

Shervais, J. W.↗
NASA NTRS1985

Sun, weather, and climate

The general field of sun-weather/climate relationships, that is, apparent weather and climate responses to solar activity is introduced and theoretical and experimental suggestions for further research to identify and investigate the unknown causal mechanisms are provided. Topics of discussion include: (1) solar-related correlation factors and energy sources; (2) long-term climatic trends; (3) short-term meteorological correlations; (4) miscellaneous obscuring influences; (5) physical processes and mechanisms; (6) recapitulation of sun-weather relationships; and (7) guidelines for experiments.

Herman, J. R.↗
NASA NTRS1986

Regional-scale estimates of surface moisture availability and thermal inertia using remote thermal measurements

A review is presented of numerical models which were developed to interpret thermal IR data and to identify the governing parameters and surface energy fluxes recorded in the images. Analytic, predictive, diagnostic and empirical models are described. The limitations of each type of modeling approach are explored in terms of the error sources and inherent constraints due to theoretical or measurement limitations. Sample results of regional-scale soil moisture or evaporation patterns derived from the Heat Capacity Mapping Mission and GOES satellite data through application of the predictive model devised by Carlson (1981) are discussed. The analysis indicates that pattern recognition will probably be highest when data are collected over flat, arid, sparsely vegetated terrain. The soil moisture data then obtained may be accurate to within 10-20 percent.

Carlson, T. N.↗
NASA NTRS1985

Backscattered ultraviolet measurements of ozone 1970-2000 - An overview

The history of the Backscattered Ultraviolet Experiment (BUV) is recounted and related future efforts are discussed. Satellite measurement of backscattered UV radiation will be the major source of long-term global information about total ozone and ozone profiles for the rest of this century. These measurements started with the BUV experiment flown on Nimbus 4 from 1970 to 1977 and are presently being continued with the Solar and Backscattered Ultraviolet/Total Ozone Mapping Spectrometer (SBUV/TOMS) launched on Nimbus 7 in 1978. NOAA's improved version (SBUV/2) is to fly until sometime in the 1990s and NASA plans to fly an SBUV/2 on the Upper Atmosphere Research Satellite in 1989. Differences between these instruments and in the algorithms for deriving ozone amounts from these data sets are discussed.

Fleig, A. J.↗
NASA NTRS1987

A systematic search for long-term variability in a large sample of X-ray sources

A method which uses the correct measurement error distribution (Poisson) and which naturally takes into account detections as well as upper limits has been developed to search for flux variability in X-ray sources. The method is applied to 256 sources observed at least twice with the Einstein Observatory Imaging Proportional Counter. These sources have, in the very large majority of cases, an X-ray flux in the range 1 x 10 to the -13th to 6 x 10 to the -12th erg/sq cm/s (0.2-3.5 keV). Thirty-one sources show flux variations with amplitude ranging from about 20 percent to a factor of 6. Flux variations of small amplitude seem to be fairly common, but can be detected only in bright sources or in sources observed with very long exposures. Variations of a factor of 2 or more are seen in about 15 percent of the sources for which variations of such an amplitude are detectable.

Maccacaro, Tommaso↗
NASA NTRS1988

Flat-spectrum, variable radio sources

The general behavior of flat-spectrum (compact) radio sources is examined in terms of adiabatic-jet models. Two puzzling properties - namely, (1) the broad, rather flat spectrum (over a large range of radio frequencies) and (2) the relatively slow decay of burst amplitude (with decreasing radio frequency) - are explained. Acceptable models are characterized by the following: (1) a nearly conical, adiabatic jet, with conserved magnetic flux transverse to the axis of the jet; (2) prolonged injection (for which the duration of an event exceeds the apparent transit time scale); and (3) a transparent spectral index which is not too steep. It is suggested that the acceleration mechanism in the core of compact jets may differ substantially from that far from the core, producing a flatter electron number index s = 1.4-2.6.

O'Dell, S. L.↗
NASA NTRS1988

Magnetic confinement of cosmic clouds

The role of the magnetic field in the confinement or compression of interstellar gas clouds is reconsidered. The virial theorem for an isolated magnetized cloud in the presence of distant magnetic sources is reformulated in terms of moments of the internal and external currents, and an equilibrium condition is derived. This condition is applied to the interaction between isolated clouds for the simple- and artificial-case in which the field of each cloud is a dipole. With the simplest of statistical assumptions, the probability of any given cloud being compressed is calculated as about 10 percent, the magnetic field acting as a medium which transmits the kinetic pressure between clouds. Even when compression occurs the magnetic pressure 1/2 B-squared may decrease on leaving the cloud surface.

Azar, Michel↗
NASA NTRS1989

Sweet potato growth parameters, yield components and nutritive value for CELSS applications

Sweet potatoes have been grown hydroponically using the nutrient film technique (NFT) to provide a potential food source for long-term manned space missions. Experiments in both sand and NFT cultivars have produced up to 1790 g/plant of fresh storage root with an edible biomass index ranging from 60-89 percent and edible biomass linear growth rates of 39-66 g/sq m day in 105 to 130 days. Experiments with different cultivars, nutrient solution compositions, application rates, air and root temperatures, photoperiods, and light intensities indicate good potential for sweet potatoes in CELSS.

Loretan, P. A.↗
NASA NTRS1989

Effect of channel size on sweet potato storage root enlargement in the Tuskegee University hydroponic nutrient film system

The potential of the sweet potato as a food source for future long term manned space missions is being evaluated for NASA's Controlled Ecological Life Support Systems (CELSS) program. Sweet potatoes have been successfully grown in a specially designed Tuskegee University nutrient film technique (TU NFT) system. This hydroponic system yielded storage roots as high as 1790 g/plant fresh weight. In order to determine the effect of channel size on the yield of sweet potatoes, the width and depth of the growing channels were varied in two separate experiments. Widths were studied using the rectangular TU NFT channels with widths of 15 cm (6 in), 30 cm (12 in) and 45 cm (18 in). Channel depths of 5 cm (2 in), 10 cm (4 in), and 15 cm (6 in) were studied using a standard NASA fan shaped Biomass Production Chamber (BPC) channel. A comparison of preliminary results indicated that, except for storage root number, the growth and yield of sweet potatoes were not affected by channel width. Storage root yield was affected by channel depth although storage root number and foliage growth were not. Both experiments are being repeated.

Morris, Carlton E.↗
NASA NTRS1990

Initialization and assimilation of cloud and rainwater in a regional model

The initialization and assimilation of cloud and rainwater quantities in a mesoscale regional model was examined. Forecasts of explicit cloud and rainwater are made using conservation equations. The physical processes include condensation, evaporation, autoconversion, accretion, and the removal of rainwater by fallout. These physical processes, some of which are parameterized, represent source and sink in terms in the conservation equations. The question of how to initialize the explicit liquid water calculations in numerical models and how to retain information about precipitation processes during the 4-D assimilation cycle are important issues that are addressed.

Raymond, William H.↗