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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Laminar natural convection under nonuniform gravity.

Laminar natural convection is analyzed for cases in which gravity varies with the distance from the leading edge of an isothermal plate. The study includes situations in which gravity varies by virtue of the varying slope of a surface. A general integral solution method which includes certain known integral solutions as special cases is developed to account for arbitrary position-dependence of gravity. A series method of solution is also developed for the full equations. Although it is more cumbersome it provides verification of the integral method.

Lienhard, J.↗
NASA NTRS1972

Evidence for the binary nature of Centaurus X-3 from Uhuru X-ray observations.

Analysis of data spanning a year of observations of the pulsating X-ray source Cen X-3 from Uhuru has revealed the existence of periodic variations in intensity of the source and correlated sinusoidal variations in the period of the 4.8-sec pulsations. We interpret this effect as due to an occulting binary system. The changes in intensity are then due to occultation of the X-ray source by a large massive companion, and the sinusoidal variations in the period of the 4.8-sec pulsations are due to Doppler effect. Physical parameters for the system are derived, and evidence for the existence and nature of an extended atmosphere surrounding the massive occulting object is discussed.

Schreier, E.↗
NASA NTRS1972

Nature of the secondary component of beta Lyrae.

Development of a hypothesis concerning the nature of the secondary component of beta Lyrae which is regarded as more plausible than the suggestion that this component is a black hole. Adopting Huang's (1962) and Woolf's (1965) basic model for beta Lyrae, it is suggested that the secondary star may be a massive 'main-sequence' star in rapid, nonuniform motion. Certain findings regarding mu Sco and V356 Sgr, which have primaries that are very cool and underluminous for their masses, are cited as evidence for such an inference, since their underluminosity is probably due to high angular momentum and they are normal enough not to be suspected of harboring a black hole.

Stothers, R.↗
NASA NTRS1972

On the nature of some faint infrared stars.

Results of photometric observations of additional Haro-Chavira (H-C) infrared stars, which yield information regarding the nature of these objects. The observations, extending from 0.7 to 3.4 micrometers, were obtained with the 60-in. NASA telescope located at the Catalina Observatory of the University of Arizona. The late M-type spectra of these objects suggests that many of them may be variable. Their apparent concentration to the galactic plane notwithstanding, the fainter late M-type H-C stars must be distinctly less luminous (of luminosity class II or III).

Lee, T. A.↗
NASA NTRS1972

Quartz and feldspar glasses produced by natural and experimental shock.

Refractive index, density, and infrared absorption studies of naturally and experimentally shocked-produced glasses formed from quartz, plagioclase, and alkali-feldspar confirm the existence of two main groups of amorphous forms of the framework silicates: solid-state and liquid-state glasses. These were apparently formed as metastable release products of high-pressure-phases above and below the glass transition temperatures. Solid-state glasses exhibit a series of structural states with increasing disorder caused by increasing shock pressures and temperatures. They gradually merge into the structural state of fused minerals similar to that of synthetic glasses quenched from a melt. Shock-fused alkali feldspars can, however, be distinguished from their laboratory-fused counterparts by infrared absorption and by higher density.

Stoeffler, D.↗
NASA NTRS1972

A synoptic study of the nature and effects of field aligned low energy electron precipitation in the auroral regions

A synoptic study is presented of field-aligned precipitation events observed during a 16-month period, representing a full 4 pi precession of the satellite orbital plane in magnetic local time. The morphology of this type of precipitation, its nature, and relationships between this phenomenon and other geophysical events are discussed in the context of the 16-month data base.

Berko, F. W.↗
NASA NTRS1972

Effects of fuel nozzle design on performance of an experimental annular combustor using natural gas fuel

Tests of various fuel nozzles were conducted with natural gas fuel in a full-annulus combustor. The nozzles were designed to provide either axial, angled, or radial fuel injection. Each fuel nozzle was evaluated by measuring combustion efficiency at relatively severe combustor operating conditions. Combustor blowout and altitude ignition tests were also used to evaluate nozzle designs. Results indicate that angled injection gave higher combustion efficiency, less tendency toward combustion instability, and altitude relight characteristics equal to or superior to those of the other fuel nozzles that were tested.

Wear, J. D.↗
NASA NTRS1972

Tables of critical-flow functions and thermodynamic properties for methane and computational procedures for both methane and natural gas

Procedures for calculating the mass flow rate of methane and natural gas through nozzles are given, along with the FORTRAN 4 subroutines used to make these calculations. Three sets of independent variables are permitted in these routines. In addition to the plenum pressure and temperature, the third independent variable is either nozzle exit pressure, Mach number, or temperature. A critical-flow factor that becomes a convenient means for determining the mass flow rate of methane through critical-flow nozzles is tabulated. Other tables are included for nozzle throat velocity and critical pressure, density, and temperature ratios, along with some thermodynamic properties of methane, including compressibility factor, enthalpy, entropy, specific heat, specific-heat ratio, and speed of sound. These tabulations cover a temperature range from 120 to 600 K and pressures to 3 million N/sq m.

Johnson, R. C.↗
NASA NTRS1973

Monitoring the vernal advancement and retrogradation (green wave effect) of natural vegetation

The author has identified the following significant results. Preliminary evaluation of autumnal phase ground truth data suggests that the sampling procedures at the Great Plains Corridor network test sites are adequate to show relatively small temporal changes in above-ground vegetation biomass and vegetation condition. Vegetation changes measured August through December, reflect grazing intensity and environmental conditions at the test sites. Preliminary analysis of black and white imagery suggests that detail in vegetation patterns is much greater than originally anticipated. A first look analysis of single band imagery and digital data at two locations shows that woodland, grassland, and cropland areas are easily delineated. Computer derived grey-scale maps from MSS digital data were shown to be useful in identifying the location of small fields and features of the natural and cultivated lands. Single band imagery and digital data are believed to have important application for synoptic land use mapping and inventory. Initial ratio analysis, using band 5 and 7 data, suggests the applicability in the greenness of a vegetative scene.

Rouse, J. W., Jr.↗
NASA NTRS1973

Performance gains by using heated natural-gas fuel in an annular turbojet combustor

A full-scale annular turbojet combustor was tested with natural gas fuel heated from ambient temperature to 800 K (980 F). In all tests, heating the fuel improved combustion efficiency. Two sets of gaseous fuel nozzles were tested. Combustion instabilities occurred with one set of nozzles at two conditions: one where the efficiency approached 100 percent with the heated fuel; the other where the efficiency was very poor with the unheated fuel. The second set of nozzles exhibited no combustion instability. Altitude relight tests with the second set showed that relight was improved and was achievable at essentially the same condition as blowout when the fuel temperature was 800 K (980 F).

Marchionna, N. R.↗