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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Morphological relationships in the chromospheric H-alpha fine structure

A continuous relationship is proposed between the basic elements of the dark fine structure of the quiet and active chromosphere. A progression from chromospheric bushes to fibrils, then to chromospheric threads and active region filaments, and finally to diffuse quiescent filaments, is described. It is shown that the horizontal component of the field on opposite sides of an active region quiescent filament can be in the same direction and closely parallel to the filament axis. Consequently, it is unnecessary to postulate twisted or otherwise complex field configurations to reconcile the support mechanism of filaments with the observed motion along their axis.

Foukal, P.↗
NASA NTRS1972

Spacecraft platform cost estimating relationships

The three main cost areas of unmanned satellite development are discussed. The areas are identified as: (1) the spacecraft platform (SCP), (2) the payload or experiments, and (3) the postlaunch ground equipment and operations. The SCP normally accounts for over half of the total project cost and accurate estimates of SCP costs are required early in project planning as a basis for determining total project budget requirements. The development of single formula SCP cost estimating relationships (CER) from readily available data by statistical linear regression analysis is described. The advantages of single formula CER are presented.

Gruhl, W. M.↗
NASA NTRS1971

On the relationship between aerosol content and errors in telephotometer experiments.

This paper presents an invariant imbedding theory of multiple scattering phenomena contributing to errors in telephotometer experiments. The theory indicates that there is a simple relationship between the magnitudes of the errors introduced by successive orders of scattering and it is shown that for all optical thicknesses each order can be represented by a coefficient which depends on the field of view of the telescope and the properties of the scattering medium. The verification of the theory and the derivation of the coefficients have been accomplished by a Monte Carlo program. Both monodisperse and polydisperse systems of Mie scatterers have been treated. The results demonstrate that for a given optical thickness the coefficients increase strongly with the mean particle size particularly for the smaller fields of view.

Thomas, R. W. L.↗
NASA NTRS1971

Relationship between Fe /+/ ions and equatorial spread F.

Evaluation of observations from the retarding potential analyzer on Ogo 6 near the magnetic equator, demonstrating an intimate relationship between the presence of Fe(+) ions and irregularities in the total ion concentration. The ionospheric irregularities (or structure) are probably another manifestation of equatorial spread F, although this has not yet been verified. Nearly half the nighttime equatorial crossings below 700 km exhibit both Fe(+) and structure, but only 10% of the passes without Fe(+) have structure. Approximately one-third of the passes with Fe(+) are not structured, which indicates that Fe(+) may be a necessary but not sufficient condition for structure formation. The Atlantic region shows an extremely high and detailed correlation between Fe(+) ions and the irregularities.

Hanson, W. B.↗
NASA NTRS1972

Relationship of dislocation density of silicon to solar cell current loss at low temperature.

Large decreases in short circuit current of silicon solar cells have been reported to occur as temperature is decreased below -60 C. Experimental results are presented which relate high dislocation density of the silicon bulk material of cells to the large current loss effect. These results reveal a direct relationship between low bulk dislocation density and low current loss at low temperature. Oxygen content does not appear to play a significant role in the low temperature-large current loss effect, since some Czochralski cells did not suffer from this effect whereas some float-zone cells did. Other float-zone silicon cells had only medium current losses at low temperature despite their high bulk dislocation density. It appears that use of low-dislocation-density silicon can eliminate the current loss problem in low temperature cell operation.

Mandelkorn, J.↗
NASA NTRS1971

A re-examination of relationships among pyroxene-plagioclase achondrites.

In light of the new data of Jerome (1970), a brief discussion of genetic relationships between eucrites, howardites and diogenites is presented. Howardites are not direct products of magmatic crystallization, as has sometimes been postulated, but instead are interpreted as polymict breccias resulting from the mechanical mixture of eucrites and diogenites. Testing of this model by means of chemical arguments is made complicated however by the probable presence of a chondritic component in howardites and by a sequence analogous to terrestrial differentiation series, among the eucrites themselves.

Jerome, D. Y.↗
NASA NTRS1972

Intrinsic B-V color for galactic cepheids and some comments on the Sandage-Tammann relationship

Transformations are found for converting the b-y color excesses for Cepheids given by Williams (1966) and Kelsall (1971) into B-V excesses. The combination of these results with the E(B-V)'s determined by Sandage and Tammann (1971) gives precise data for eighty-eight galactic Cepheids. The period-color and period-color-(amplitude defect) relationships, that are germane to the LogP intervals 0.4 to 1.4 and 0.4 to 1.3, respectively, are found.

Kelsall, T.↗
NASA NTRS1973

The relationship between eddy-transport and second-order closure models for stratified media and for vortices

The question is considered of how complex a model should be used for the calculation of turbulent shear flows. At the present time there are models varying in complexity from very simple eddy-transport models to models in which all the equations for the nonzero second-order correlations are solved simultaneously with the equations for the mean variables. A discussion is presented of the relationship between these two models of turbulent shear flow. Two types of motion are discussed: first, turbulent shear flow in a stratified medium and, second, the motion in a turbulent line vortex. These two cases are instructive because in the first example eddy-transport methods have proven reasonably effective, whereas in the second, they have led to erroneous conclusions. It is not generally appreciated that the simplest form of eddy-transport theory can be derived from second-order closure models of turbulent flow by a suitably limiting process. This limiting process and the suitability of eddy-transport modeling for stratified media and line vortices are discussed.

Donaldson, C. D.↗
NASA NTRS1973

On the relationship between acoustic energy density flux near the jet axis and far field acoustic intensity

By measurement and analysis, the relationship between the distribution of the outflow of acoustic energy over the jet boundary and the far-field intensity is considered. The physical quantity used is the gradient of the pressure evaluated on a geometrical plane at the smallest possible radial distance from the jet axis, but outside the vortical region, in the area where the homogeneous wave equation is reasonably well satisfied. The numerical and experimental procedures involved have been checked out by using a known source. Results indicate that the acoustic power output per unit length of the jet, in the region from which the sound emanates, peaks at approximately 9 diameters downstream. The acoustic emission for a jet Strouhal number of about 0.3 exceeds the emission for all other Strouhal numbers nearly everywhere along the measurement plane. However, the far-field peak intensity distribution obtained from the contribution of each station was found to depend on the spatial extent of the region where sound emanates from the jet, which, in turn, depends more on the far-field angle than on the Strouhal number.

Maestrello, L.↗
NASA NTRS1972

Voltage and power relationships in lithium-containing solar cells.

Photovoltaic characteristics have been measured on a large number of crucible-grown lithium-containing solar cells irradiated by 1-MeV electrons to fluences ranging from 3 x 10 to the 13th power to 3 x 10 to the 15th power electrons per sq cm. These measurements have established empirical relationships between cell photovoltaic parameters and lithium donor density gradient. Short-circuit current and maximum power measured immediately after irradiation decrease logarithmically with lithium gradient. Open-circuit voltage increases logarithmically with lithium gradient both immediately after irradiation and after recovery, the degree of recovery being strongly gradient-dependent at high fluence. As a result, the maximum power and the power at 0.43 V after recovery from 3 x 10 to the 15th power electrons per sq cm increase with increasing lithium gradient.

Faith, T. J.↗
NASA NTRS1973

Polar cap magnetic variations and their relationship with the interplanetary magnetic sector structure.

The relationship between polar geomagnetic variations and the polarity of the interplanetary magnetic sectors has been studied for the quiet year 1965. It is found that during the day hours a system of ionospheric currents encircles the magnetic poles on every day. The current system may extend up to 15 deg from the pole but is strongest at 8 to 10 deg invariant colatitude. The current direction as seen from near the magnetic poles is counterclockwise during interplanetary sectors with field pointing away from the sun and clockwise during toward sectors. The current strength is dependent on season, being strongest during local summer. When the magnetic pole is on the nightside of the earth, this polar cap current is absent or very weak.

Svalgaard, L.↗
NASA NTRS1973

Design relationships for holographic memories.

The maximum capacity of a block-oriented, random-access memory is determined primarily by the geometrical parameters of the lenses required to create a Fourier transform of a spatial bit pattern and to image the reconstructed bits onto a photodetector array. Furthermore, the maximum packing density is determined primarily by the same parameters. Several important relationships are developed that are useful in the preliminary design of holographic memories.

Lugt, A. V.↗