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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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
NASA NTRS1945

The Elastic Constants for Wrought Aluminum Alloys

There are several constants which have been devised as numerical representations of the behavior of metals under the action of loadings which stress the metal within the range of elastic action. Some of these constants, such as Young's modulus of elasticity in tension and compression, shearing modulus of elasticity, and Poisson's ratio, are regularly used in engineering calculations. Precise tests and experience indicate that these elastic constants are practically unaffected by many of the factors which influence the other mechanical properties of materials and that a few careful determinations under properly controlled conditions are more useful and reliable than many determinations made under less favorable conditions. It is the purpose of this paper to outline the methods employed by the Aluminum Research Laboratories for the determination of some of these elastic constants, to list the values that have been determined for some of the wrought aluminum alloys, and to indicate the variations in the values that may be expected for some of the commercial products of these alloys.

ALUMINUM ALLOYS, WROUGHT-ELASTICITY↗
NASA NTRS1951

:investigation of a 24-inch Shock-in-rotor Type Supersonic Compressor Designed for Simple Radial Equilibrium Behind Normal Shock

A 24-inch-diameter shock-in-rotor supersonic compressor rotor designed to obtain simple radial equilibrium behind the normal shock obtained a maximum total-pressure ratio of 2.02 at an adiabatic efficiency of 0.74 and a weight flow of 61.5 pounds per second at design speed. Although this design method considerably reduced the radial forces, there was no apparent reduction in the radial forces, there was no apparent reduction in the radial redistribution of mass flow over the radial redistribution obtained in the previous investigation. This investigation indicates that the shock boundary-layer interaction pattern and associated effects have a very large effect on the radial redistribution of mass flow through the shock-in-rotor supersonic-compressor rotor.

FLOW, SUPERSONIC↗
NASA NTRS1951

Experimental Investigation of a 16-inch Impulse-type Supersonic-compressor Rotor

Performance data and characteristics of a 16-inch impulse-type supersonic-compressor rotor are presented. The experimental portion of this investigation was conducted in Freon-12. A peak pressure ratio of 3.6 was obtained with an adiabatic efficiency of 0.80 at design conditions. Performance was continuous from impulse operation, at open throttle, to shock-in-rotor operation at the stall condition.

COMPRESSOR FLOW THEORY AND EXPERIMENT↗
NASA NTRS1992

Theoretical support for the Airborne Antarctic Ozone Experiment

This investigation was to provide theoretical support during and after the deployment of NASA research aircraft to Punta Arenas, Chile during August and September of 1987 to conduct the Airborne Antarctic Ozone Experiment. The experiment was very successful in demonstrating the role of anthropogenic chlorine in producing the ozone hole over Antarctica during September and October of 1987. The PI worked primarily on using tracer data from the ER-2 aircraft to show that transport could not have caused the ozone hole in 1987, and that transport of chemical species into the polar vortex was very weak during the period of the experiment. The presence of gravity waves was also very apparent in the ER-2 data, and papers were published on this analysis and on the use of meteorological analyses to position the aircraft within the vortex.

Hartmann, Dennis L.↗
NASA NTRS1994

Investigations of the dynamical evolution of protoplanetary nebulae

The spectral energy distributions (SED's) of all the known Class I (protostellar) sources in the Taurus molecular cloud were modelled. The Tereby, Shu, & Cassen (1984, TSC) density distribution for a rotating, infalling envelope was adopted. The radiative equilibrium temperature distribution from the spherical average of the TSC density distribution was calculated. The resulting spherically-symmetric temperature distribution then provides the source function to obtain the emergent spectrum at a given inclination angle i from the formal solution of the transfer equation, using the exact density (opacity) distribution. Results showed that the SED's of the protostar candidates in Taurus can be reproduced with TSC models having infall rates close to the values predicted by the theory of isothermal cloud collapse. Flat Spectrum T Tauri Stars were studied. The mid- to far-infrared fluxes of 'flat spectrum' T Tauri stars can be explained by radiative equilibrium emission from infalling dusty envelopes. This explanation indicated that models employing 'active' disks, in which the temperature distribution is a parameterized power law, should be invoked with caution. Infall also naturally explains the scattered light nebulae detected around many flat-spectrum sources. Results showed that the SED's of the protostar candidates in Taurus can be reproduced with TSC models having infall rates close to the values predicted by the theory of isothermal cloud collapse. Flattened infalling envelope models are also being studied.

Hartmann, Lee W.↗
NASA NTRS1993

Possible test of ancient dense Martian atmosphere

We have completed preliminary calculations of the minimum sizes of bolides that would penetrate various hypothetical Martian atmospheres with surface pressures ranging from 6 to 1000 mbar for projectiles of various strengths. The calculations are based on a computer program. These numbers are used to estimate the diameter corresponding to the turndown in the crater diameter distribution due to the loss of these bodies, analogous to the dramatic turndown at larger sized already discovered on Venus due to this effect. We conclude that for an atmosphere greater than a few hundred millibars, a unique downward displacement in the diameter distribution would develop in the crater diameter distribution at D approximately = 0.5-4 km, due to loss of all but Fe bolides. Careful search for this displacement globally, as outlined here, would allow us to place upper limits on the pressure of the atmosphere contemporaneous with the oldest surfaces, and possibly to get direct confirmation of dense ancient atmospheres.

Hartmann, W. K.↗
NASA NTRS1993

The Payload Advisory Panel and the Data and Information System Advisory Panel of the Investigators Working Group of the Earth Observing System: A joint report

The Payload Advisory Panel of the Investigators Working Group (IWG) for the Earth Observing System (EOS) met 4 to 6 October 1993 in Herndon, Virginia. The Panel, originally composed of the Interdisciplinary Science Principal Investigators, was expanded to include all Principal Investigators and as such is now the IWG itself. The meeting also addressed directly a report from the EOS Data and Information System (EOSDIS) Advisory Panel. The meeting focused on payload issues in the years 2000 to 2005; however, some subjects in the nearer-term, most significantly EOSDIS, were considered. The overarching theme of convergence in Earth observations set a backdrop for the entire meeting. Other themes included: atmospheric chemistry; remote sensing of the global cycles of energy, water, and carbon in EOS; ocean and land-ice altimetry; and the EOSDIS. The Totol Solar Irradiance Monitoring Report and results from the Accelerated Canopy Chemistry Program are included as appendices.

Moore, Berrien, III↗
NASA NTRS1993

Physical mechanism of comet outbursts - An experimental result

Attention is given to an experimental investigation of the physical mechanism of comet outbursts which is consistent with the general picture of mantle presence on comets and clarifies the relation of mantles to eruptive activity. The experiment and closeup observation of Comet P/Halley suggest a result different from most mathematical models in that the release of gas pressure does not occur only from uniform gas flow out of the entire surface. In some active comets near perihelion within a few AU of the sun, gas production rates and disturbance of the surface may be so high that the outflow is nearly continuous, with the regolith being entirely stripped away, as in many of the models. The present model provides a cyclic eruption and recharge mechanism which is lacking in most other models.

Hartmann, William K.↗