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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Plasma wave observations near the plasmapause with the S3-A satellite.

Description of the electric field noise phenomena observed by the S3-A spacecraft near the plasmapause during the magnetic storm of Dec. 16, 17, 1971. The most striking and unusual feature of these storm time electric field observations is the occurrence of a region of intense low-frequency (20 to 500 Hz) electrostatic noise bursts just outside the plasmapause boundary. These noise bursts occurred concurrently with the rapid decrease in low-energy (E ranging from 20 to 50 keV) ring current protons mirroring near the equator during this storm and may be responsible for the loss of these particles. The characteristics of other phenomena, such as whistlers, ELF hiss, and banded chorus, observed near the plasmapause during this period are also discussed.

Anderson, R. R.↗
NASA NTRS1973

Radar signal return from near-shore surface and shallow subsurface features, Darien Province, Panama

The AN/APQ-97 radar imagery over eastern Panama is analyzed. The imagery was directed toward extraction of geologic and engineering data and the establishment of operational parameters. Subsequent investigations emphasized landform identification and vegetation distribution. The parameters affecting the observed return signal strength from such features are considered. Near-shore ocean phenomena were analyzed. Tidal zone features such as mud flats and reefs were identified in the near range, but were not detectable in the far range. Surface roughness dictated the nature of reflected energy (specular or diffuse). In surf zones, changes in wave train orientation relative to look direction, the slope of the surface, and the physical character of the wave must be considered. It is concluded that the establishment of the areal extent of the tidal flats, distributary channels, and reefs is practical only in the near to intermediate range under minimal low tide conditions.

Hanson, B. C.↗
NASA NTRS1974

Interplanetary and near-Jupiter meteoroid environments - Preliminary results from the meteoroid detection experiment

Data on interplanetary and near-Jupiter micrometer-sized particle encounters from the meteoroid-detection experiment on Pioneer 10 indicate that Jupiter is much 'dustier' than interplanetary space. Whereas the near-earth particulate flux showed very little increase over the interplanetary flux, the near-Jupiter penetration flux was over two orders of magnitude higher than the interplanetary flux.

Kinard, W. H.↗
NASA NTRS1973

Lifetimes of enhanced chromospheric network features near active regions

Centerline H alpha filtergrams providing nearly full-day coverage of the sun are used to study the lifetimes of enhanced network features near active regions. In the two cases studied the fraction remaining of those features present at an original epoch remains near unity for 50 hr, then drops exponentially with a 1/e decay time of 30 hr. Histories of representative enhanced network features are discussed.-

Prata, S. W.↗
NASA NTRS1974

The interplanetary and near-Jupiter meteoroid environments

The meteoroid penetration detectors on the Pioneer 10 spacecraft recorded 67 meteoroid penetrations through the 25-micron stainless steel test material while the spacecraft was between 1.0 and 5.1 AU. Ten of these penetrations occurred during the encounter with Jupiter. The cumulative spatial density of meteoroids with masses greater than 2 nanograms has been calculated from these data for interplanetary space and for the near-Jupiter space. The spatial density is found to be essentially constant in interplanetary space between 1 and 5 AU, approximately 1 meteoroid per cubic km, and 1-2 orders of magnitude greater near Jupiter. There was no increase in the spatial density of meteoroids in the asteroid belt and hence no evidence that there is a significant asteroidal component of 2-nanogram meteoroids. It is uncertain whether the meteoroids detected near Jupiter were in orbit about Jupiter or were gravitationally focused toward the planet from solar orbits.

Humes, D. H.↗
NASA NTRS1975

Prediction of sonic boom from experimental near-field overpressure data. Volume 1: Method and results

A computerized procedure for predicting sonic boom from experimental near-field overpressure data has been developed. The procedure extrapolates near-field pressure signatures for a specified flight condition to the ground by the Thomas method. Near-field pressure signatures are interpolated from a data base of experimental pressure signatures. The program is an independently operated ODIN (Optimal Design Integration) program which obtains flight path information from other ODIN programs or from input.

Glatt, C. R.↗
NASA NTRS1975

Wind tunnel investigation of the wake near the trailing edge of a distributed upper-surface-blown flap

An investigation of the flow field near the trailing edge of a distributed upper-surface-blown propulsive-lift transport was conducted in the Langley V/STOL tunnel. This model used blowing slots across the entire wing span to produce a thin jet efflux near the leading edge and at the knee of the flap. Velocity surveys of the flow field were taken near the trailing edge of the model, and are presented as plots of the individual velocity vectors. The test conditions include an angle-of-attack range from 4 deg to 16 deg and a thrust coefficient range from 0 to 1.3 at a free-stream dynamic pressure of 814 Newton per square meter (17 pounds per square foot).

Forsyth, D. R.↗
NASA NTRS1975

A flying hot wire study of the turbulent near wake of a circular cylinder at Reynolds number of 140,000

The phenomenology was studied of the processes of vortex formation and transport in the near wake, at a Reynolds number sufficiently high to insure a fully turbulent wake, but low enough to insure a laminar separation. The apparatus developed for measuring this flow consisted of X-array hot wire probes mounted on the ends of a pair of whirling arms. A computer controlled data acquisition system was slaved to the position of the rotating arm and managed, monitored, edited, and recorded the vast profusion of data which is continuously poured out by the device. Results are presented which show the instantaneous velocity, intermittency, vorticity, and stress fields as a function of phase for the first six diameters of the near wake. The stresses in the near wake emerge as a concatenation of peaks and valleys, some the result of strong induced motions in the outer flow which cause free stream fluid to move rapidly inward toward the center of the wake, others the result of the random motions of the background turbulence.

Cantwell, B. J.↗
NASA NTRS1975

Acceleration of H, He, and heavy ions observed in the magnetosheath, magnetotail, and near-by interplanetary space

Pulses of electrons and ions composed of H, He, and heavier elements were observed in the magnetosheath, magnetotail, and near-by interplanetary space. From the spatial positions where these particles were detected and the ion flow directions, it is concluded that they were accelerated at the bow shock near the sub-solar point and in the near-earth region of the neutral sheet of the magnetotail.

Fan, C. Y.↗
NASA NTRS1976

Static and wind tunnel near-field/far field jet noise measurements from model scale single-flow baseline and suppressor nozzles. Volume 2: Forward speed effects

A model scale flight effects test was conducted in the 40 by 80 foot wind tunnel to investigate the effect of aircraft forward speed on single flow jet noise characteristics. The models tested included a 15.24 cm baseline round convergent nozzle, a 20-lobe and annular nozzle with and without lined ejector shroud, and a 57-tube nozzle with a lined ejector shroud. Nozzle operating conditions covered jet velocities from 412 to 640 m/s at a total temperature of 844 K. Wind tunnel speeds were varied from near zero to 91.5 m/s. Measurements were analyzed to (1) determine apparent jet noise source location including effects of ambient velocity; (2) verify a technique for extrapolating near field jet noise measurements into the far field; (3) determine flight effects in the near and far field for baseline and suppressor nozzles; and (4) establish the wind tunnel as a means of accurately defining flight effects for model nozzles and full scale engines.

Jaeck, C. L.↗
NASA NTRS1977

Static and wind tunnel near-field/far-field jet noise measurements from model scale single-flow base line and suppressor nozzles. Summary report

A test program was conducted in the Boeing large anechoic test chamber and the NASA-Ames 40- by 80-foot wind tunnel to study the near- and far-field jet noise characteristics of six baseline and suppressor nozzles. Static and wind-on noise source locations were determined. A technique for extrapolating near field jet noise measurements into the far field was established. It was determined if flight effects measured in the near field are the same as those in the far field. The flight effects on the jet noise levels of the baseline and suppressor nozzles were determined. Test models included a 15.24-cm round convergent nozzle, an annular nozzle with and without ejector, a 20-lobe nozzle with and without ejector, and a 57-tube nozzle with lined ejector. The static free-field test in the anechoic chamber covered nozzle pressure ratios from 1.44 to 2.25 and jet velocities from 412 to 594 m/s at a total temperature of 844 K. The wind tunnel flight effects test repeated these nozzle test conditions with ambient velocities of 0 to 92 m/s.

Jaeck, C. L.↗
NASA NTRS1977

Charge distributions near metal-dielectric interfaces before and after dielectric surface flashover

A technique was developed for measuring surface charge distribution near interfaces without placing any measuring apparatus near the face of the samples. The results of measurements which were made on FEP Teflon and Kapton dielectrics, before and after are given flashover, with various types of interfaces. Also given are data showing mean time between flashovers for various configurations exposed to a variety of environmental conditions. Several charge transfer mechanisms are considered as a means by which stable charge distributions may be maintained near interfaces.

Robinson, J. W.↗
NASA NTRS1978

On the configuration of the magnetotail near midnight during quiet and weakly disturbed periods - State of the magnetosphere

Particle and field data are analyzed for a number of magnetically quiet days. It is shown that the magnetotail near midnight may exist for hours at a time in widely different quasi-stable configurations which, in their limit, can be characterized as being (1) fairly dipolelike to about 15 R(E), beyond which the field becomes taillike; and (2) dipolelike to only about 10 R(E), beyond which the field becomes taillike. These different states affect both the dynamics of the substorm and the evolution of the pitch angle distributions of energetic electrons in the near-earth plasma sheet past midnight. During quiet times, the plasma sheet in its azimuthal variation is at its thinnest in the region near midnight.

West, H. I., Jr.↗
NASA NTRS1979

Voyager 1 Planetary Radio Astronomy Observations Near Jupiter

Results are reported from the first low frequency radio receiver to be transported into the Jupiter magnetosphere. Dramatic new information was obtained both because Voyager was near or in Jupiter's radio emission sources and also because it was outside the relatively dense solar wind plasma of the inner solar system. Extensive radio arcs, from above 30 MHz to about 1 MHz, occurred in patterns correlated with planetary longitude. A newly discovered kilometric wavelength radio source may relate to the plasma torus near Io's orbit. In situ wave resonances near closest approach define an electron density profile along the Voyager trajectory and form the basis for a map of the torus. Studies in progress are outlined briefly.

Warwick, J. W.↗
NASA NTRS1979

Voyager 1 planetary radio astronomy observations near Jupiter

Results from the first low-frequency radio receiver to be transported into the Jupiter magnetosphere are reported. Dramatic new information was obtained, both because Voyager was near or in Jupiter's radio emission sources and because it was outside the relatively dense solar wind plasma of the inner solar system. Extensive radio spectral arcs, from above 30 to about 1 MHz, occurred in patterns correlated with planetary longitude. A newly discovered kilometric wavelength radio source may relate to the plasma torus near Io's orbit. In situ wave resonances near closest approach define an electron density profile along the Voyager trajectory and form the basis for a map of the torus. Detailed studies are in progress and are outlined briefly.

Warwick, J. W.↗
NASA NTRS1979

A comparison of intense electrostatic waves near f-UHR with linear instability theory

Intense electrostatic waves near the upper hybrid resonance frequency (f-UHR) have recently been detected near but beyond the plasmapause between + or -50 deg magnetic latitude at all local times. The paper shows that the electrostatic waves observed with the ISEE 1 plasma wave receiver near f-UHR are in qualitative agreement with linear theory of multicyclotron harmonic emissions. The peak amplitudes and bandwidths observed are similar to those calculated for maximum spatial growth rates. Measurements on Hawkeye of similar waves suggest that the electric field polarization is also consistent with theory. For a wide range of plasma parameters, nonconvective instability or large spatial growth rates occur within the cyclotron band encompassing the cold upper hybrid frequency.

Kurth, W. S.↗
NASA NTRS1979

Intense electrostatic waves near the upper hybrid resonance frequency

Plasma wave measurements using instruments on the Imp 6 and Hawkeye satellites are utilized in a study of very intense electrostatic waves near the upper hybrid resonance frequency in the region just outside the plasmapause. Studies of these electrostatic disturbances show that the events occur at local times and at magnetic latitudes varying from the equator to 50 deg, and the polarization of these waves is such that the wave electric field vector is oriented perpendicular to the geomagnetic field. In most cases the center frequency of the intense waves corresponds to an (n + 1/2) fg(-) harmonic near the upper hybrid resonance frequency. The hot distribution on function is described for a few events showing temperature anisotropy and a loss cone distribution. A possible mechanism for producing intense waves near the upper hybrid resonance frequency is suggested, and evidence which indicates that the intense electrostatic waves may be a source of nonthermal continuum radiation is given.

Kurth, W. S.↗
NASA NTRS1980

Radar altimeter mean return waveforms from near-normal-incidence ocean surface scattering

Under assumptions common in radar altimetry, the mean backscattered return power for a short-pulse radar and near-normal-incidence scattering from a rough ocean surface is given by the convolution of several terms. For a nearly Gaussian transmitted pulse shape scattered from a nearly Gaussian distributed sea surface, a small-argument series expansion of one of the terms within the convolution leads to a several-term power series expansion for the mean return waveform. Specific expressions are given for the first four terms. These results, which require much less computer time than would the otherwise necessary numerical convolution, are useful for data analysis from current or past radar altimeters and for design studies of future systems. Several representative results are presented for an idealized Seasat radar altimeter.

Hayne, G. S.↗