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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 NTRS1976

High resolution spectral analyses of the Jovian decametric radiation. I - Burst morphology and drift rates

Morphological analyses of high-resolution spectral recordings of Jovian decametric radiation show a regime of phenomena not seen at lower resolutions. Observed emissions range from narrow-band (50 kHz) simple quasi-periodic bursts to wide-band emissions (extending over a 500-kHz passband) exhibiting complex structural detail. Assuming gyroemission from electrons in a dipole field for which the magnetic moment is 10 Gauss Jupiter-radius-cubed, drift-rate measurements of the bursts indicate that the source size is of the order of 600 km and its location is near 1.3 Jupiter radii at a colatitude of 27.3 deg. The measurements suggest that the emitting electrons belong to a population having a very specific equatorial pitch angle near 3.5 deg. This study concludes that it may be possible to verify gyroemission as the mechanism responsible for the decametric radiation.

Krausche, D. S.↗
NASA NTRS1977

Microbiological profiles of the Viking spacecraft

Planetary quarantine requirements associated with the launch of two Viking spacecraft necessitated microbiological assessment during assembly and testing at Cape Canaveral and the Kennedy Space Center. Samples were collected from the Viking Lander Capsules (VLC), Orbiters (VO), and Shrouds at predetermined intervals during assembly and testing. Levels of bacterial spores per square meter on the VLC-1 and VLC-2 were 1.6 x 10 squared and 9.7, respectively, prior to dry-heat sterilization. The ranges of aerobic mesophilic microorganisms detected on the VO-1 and VO-2 were 4.2 x 10 squared to 4.3 x 10 cubed and 2.3 x 10 squared to 8.9 x 10 cubed/sq m, respectively. Approximately 1300 colonies were picked from culture plates, identified, lyophilized, and stored for future reference. About 75% of all isolates were microorganisms considered indigenous to humans; the remaining isolates were associated with soil and dust. The percentage of microorganisms of human origin was consistent with results obtained with previous automated spacecraft but slightly lower than those observed for manned (Apollo) spacecraft.

Puleo, J. R.↗
NASA NTRS1977

Upper limit for CH/plus/ toward Tau Scorpii

A Fabry-Perot interferometer was used to measure a 2-sigma upper limit of 0.39 mA for CH(plus) toward Tau Sco, a line of sight with a large amount of atomic hydrogen yet only a small amount of molecular hydrogen. The upper limit for the abundance of CH(plus) in a region where hydrogen is primarily atomic shows that no unexpectedly rapid CH(plus) formation processes are occurring and, conversely, that the CH(plus) destruction rate is not smaller than expected. It is argued that either CH(plus) is primarily formed in regions with large amounts of H2 or CH(plus) is formed at least as rapidly as the density-cubes in regions where hydrogen is mostly atomic.

Jura, M.↗
NASA NTRS1977

General relativity and satellite orbits - The motion of a test particle in the Schwarzschild metric

The motion of a satellite of negligible mass about a massive spherically symmetric object in a space of Schwarzschild geometry is calculated by using ordinary Newtonian methods for an inverse-square gravitational field acted upon by an inverse-cube disturbing function. The disturbing function is expressed in terms of the Keplerian elements of the orbit and substituted in the Lagrange planetary equations. The equations can be integrated to calculate the displacement in position of the satellite due to the relativistic potential. For example, the Beacon Explorer C satellite is found to be displaced by about 17.4 cm after one revolution. For Mercury the advance of the perihelion is about 85 km after one orbit, and the maximum periodic displacement is about 13 km.

Rubincam, D. P.↗
NASA NTRS1977

The nature of the gravity anomalies associated with large young lunar craters

The negative Bouguer anomalies (i.e., mass deficiencies) associated with four young lunar craters are analyzed. Model calculations based on generalizations made from studies of terrestrial impact structures suggest that the major contribution to the Bouguer anomaly for these lunar craters is due to a lens of brecciated material confined within the present crater rim crest and extending vertically to at least a depth of one-third the crater rim diameter. Calculations also reveal a systematic variation in the magnitude of the mass deficiencies with the cube of the crater diameter.

Dvorak, J.↗
NASA NTRS1979

"Pseudobackscatter" laser velocimeter

Laser instrument measures speed of fluid flow with sensitivity of forward-scatter velocimeter and convenience of back scatter device. Velocimeter uses corner-cube reflector to return scattered laser beam to source. Device measures airflow around aircraft and in wind tunnels or other fluid-flow measurement applications.

Gunther, W. D.↗
NASA NTRS1977

Dynamic modeling of spacecraft in a collisionless plasma

A new computational model is described which can simulate the charging of complex geometrical objects in three dimensions. Two sample calculations are presented. In the first problem, the capacitance to infinity of a complex object similar to a satellite with solar array paddles is calculated. The second problem concerns the dynamical charging of a conducting cube partially covered with a thin dielectric film. In this calculation, the photoemission results in differential charging of the object.

Katz, I.↗
NASA NTRS1978

Fatigue load spectra for upwind and downwind rotors

Effect of both alternating and mean load on the fatigue life of an upwind and downwind MOD-2 wind turbine system is presented. It was shown that the fatigue damage varies as the product of the stress range cubed and the maximum stress. Hence, the alternating flapwise load caused by tower shadow and wind gradient is an important factor in determining rotor blade life.

Andrews, J. S.↗
NASA NTRS1978

Compression of rehydratable vegetables and cereals

Characteristics of freeze-dried compressed carrots, such as rehydration, volatile retention, and texture, were studied by relating histological changes to textural quality evaluation, and by determining the effects of storage temperature on freeze-dried compressed carrot bars. Results show that samples compressed with a high moisture content undergo only slight structural damage and rehydrate quickly. Cellular disruption as a result of compression at low moisture levels was the main reason for rehydration and texture differences. Products prepared from carrot cubes having 48% moisture compared favorably with a freshly cooked product in cohesiveness and elasticity, but were found slightly harder and more chewy.

Burns, E. E.↗
NASA NTRS1977

Submillimeter photometry of extragalactic objects

Submillimeter flux densities from five extragalactic objects have been measured, and upper limits set for three others. The galaxies NGC 253 and NGC 1068 have submillimeter spectra steeper than the cube of frequency. Of several source mechanisms considered for the far-infrared and submillimeter flux from NGC 1068, only thermal emission from dust at about 30 K is consistent with the data. The source of that flux, if thermal, must have a diameter of at least 5 arcsec. If one assumes radiation from dust, the masses of interstellar material derived for the central 80-arcsec diameter regions of NGC 253, NGC 1068, and NGC 5236 are, respectively, 800 million, 10 billion, and 3 billion solar masses. Measurements of submillimeter flux densities for 3C 273, BL Lac, NGC 1275, and NGC 5128 show no excess above values obtained by interpolation between radio and mid-infrared data.

Hildebrand, R. H.↗
NASA NTRS1978

Wave production in an ultrarelativistic electron-positron plasma

In this paper we calculate the eigenmodes associated with an ultrarelativistic electron-positron beam traversing a low-energy electron-positron plasma under physical conditions that may exist along open magnetic field lines above pulsar polar caps. We assume that both beam and plasma are cold and charge neutral, and that magnetic field strength and particle density decrease as the cube of (1/R). In the superstrong magnetic fields near the stellar surface where cyclotron frequencies exceed plasma frequencies, electrostatic waves and associated transverse low-frequency waves are driven unstable by the two-stream type particle distribution. At larger distances above the stellar surface the slow beam cyclotron wave is driven unstable. At even greater radial distance (approximately when particle energy density exceeds magnetic energy density) both the Ordinary and Alfven modes become unstable. All of these instabilities can lead to generation of radiation. If the particle distribution as generated at the stellar surface, assumed to consist of two streams, is modified only by plasma effects, then electrostatic and associated transverse waves may only be unstable near the stellar surface. The beam cyclotron mode which is driven by a two-stream or an inverted particle distribution may be stable.

Hardee, P. E.↗
NASA NTRS1977

Computer control of a far infrared interferometer

A simple interface has been designed for the automatic control and data collection from a Grubb Parsons Mark III cube interferometer. A computer is used to automatically step the movable mirror on the interferometer. Data may be directly input into the computer for immediate transformation or stored for later analysis via a fast Fourier transformation. The interface is based on a commercial analog-to-digital converter having a parallel-to-serial data converter. The device can also display ASCII characters sent from the computer in parallel binary code. The system is applicable to recording interferograms having long time durations and to measuring multiple interferograms for statistical averaging.

Breecher, J.↗
NASA NTRS1978

Magnetic ordering of the polar airglow

The visible airglow experiment on the Atmosphere Explorer-C satellite has gathered sufficient data over the earth's polar regions to allow one to map the geographic distribution of particle precipitation using emissions at 3371 and 5200 A. Both of these features exhibit large variations in space and time. The 3371 A emission of N2(C cubed pi), excited by low energy electrons, indicates substantial energy inputs on the dayside in the vicinity of the polar cusp. More precipitation occurs in the morning than evening for the sample reported here, while the entire night sector between magnetic latitudes 65 and 77.5 deg is subjected to particle fluxes. Regions of enhanced 5200 A emission from N(D-2) are larger in horizontal extent than those at 3371 A. This smearing effect is due to ionospheric motions induced by magnetospheric convection.

Frederick, J. E.↗
NASA NTRS1975

The saturated activities of Na-22, Mn-54, and Co-56 and the depth of sampling of soils

A multivariate linear regression study shows that the saturated activities of Na-22, Co-56, and Mn-54 are functions of the chemical composition and the reciprocal of the cube root of the sample weight. A procedure for taking the temporal variation in these short-lived radionuclides into account is described. The regression results are used to estimate the average depths of sampling of soil material. The data indicate that all 28 samples were in the same conditions of exposure when recovered as they had been for the last approximately 10 years. The saturation activity of Mn-54 is a very weak function of time.

Keith, J. E.↗
NASA NTRS1980

"Three-dimensional" vibration fixture

Simple cube-shaped fixture reduces vibration-test time to one-third required previously. Three units are supported at once. During one run each unit is tested along one of axes. Units are repositioned on second run for tests along different axes. Three runs complete test; fixture can be set up to test small, lightweight high-production units.

Schumacher, C. A.↗
NASA NTRS1978

Description of the three axis low-g accelerometer package

The three axis low-g accelerometer package designed for use on the Space Processing Application Rocket (SPAR) Program is described. The package consists of the following major sections: (1) three Kearfott model 2412 accelerometers mounted in an orthogonal triad configuration on a temperature controlled, thermally isolated cube, (2) the accelerometer servoelectronics (printed circuit cards PC-6 through PC-12), and (3) the signal conditioner (printed circuit cards PC-15 and PC-16). The measurement range is 0 + or - 0.031 g with a quantization of 1.1 x 10 to the 7th power g. The package was flown successfully on six SPAR launches with the Black Brant booster. These flights provide approximately 300 s of free fall or zero-g environment.

Amalavage, A. J.↗
NASA NTRS1977

An efficient numerical technique for calculating thermal spreading resistance

An efficient numerical technique for solving the equations resulting from finite difference analyses of fields governed by Poisson's equation is presented. The method is direct (noniterative)and the computer work required varies with the square of the order of the coefficient matrix. The computational work required varies with the cube of this order for standard inversion techniques, e.g., Gaussian elimination, Jordan, Doolittle, etc.

Gale, E. H., Jr.↗