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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Pioneer 7 observations of the August 29, 1966, interplanetary shock-wave ensemble.

The detailed plasma (except for electrons) and magnetic field data from Pioneer 7 are presented for a proposed double-shock ensemble. The Ames Research Center plasma probe data are compared with that of the MIT probe. These data are compared with MHD theory to show that the discontinuities themselves satisfy the magnetic Hugoniot equations. The data are also compared with the theoretical predictions for the double-shock structure. The theory requires as input only the forward shock velocity, the original ambient solar wind conditions, and a reasonable assumption regarding the density and azimuthal magnetic field in the 'new' solar wind which is detected after passage of the reverse shock. A unique solution is then obtained for the theoretical piston and reverse shock positions as well as for the temporal plasma behavior for both infinite and finite electrical conductivities.

Dryer, M.↗
NASA NTRS1975

Study of the performance of antennas in magnetized plasmas

The antenna studies were performed in a large magnetized plasma source, a schematic drawing of which is shown. The plasma diagnostics consist of a 70 GHz (4 mm) microwave interferometer for density measurements and of various Langmuir probes for spatially resolved measurements of t sub e, n sub e and the shape of the electron distribution function. All diagnostic data are time-resolved by sample-and-hold techniques so as to yield information about the plasma build-up, the steady-state discharge, and the plasma decay in the afterglow. Whistler waves are excited and detected with various antennas which are inserted into the center of the plasma column through one axial and two orthogonal radial ports. The antennas were tested for their proper dipole response and then calibrated in a known field geometry in air. For the electric dipole, a parallel plate capacitor field was used; the magnetic loop is calibrated in the near-zone field of a long linear conductor of known radio frequency current distribution. Results are presented and discussed.

Stenzel, R. L.↗
NASA NTRS1983

An unusual interplanetary event - Encounter with a comet?

The possibility that the slow rise to a sharp maximum and then decay surrounding a strong current sheet observed in the Venus magnetic field 0.72 AU from the sun was caused by passage of Venus through the wake of an active comet is examined. Data were also gathered by the ISEE 3 satellite magnetometer at 0.99 AU 25 h, 20 min later, a delay corresponding to the transit time for the solar wind. No shock structures bounded the phenomenon. The data indicate the presence of a small body in a much larger field of interaction and the magnetometer, solar wind probe, and electron temperature probe support a behavior similar to a planetary magnetosheath. The observed He structure in interplanetary space ruled out a solar wind source, while consideration of the magnetic equator and magnetic pole suggest that an unknown comet passed through the region between the sun and Venus at a distance where the effects would not be detected at earth.

Russell, C. T.↗
NASA NTRS1985

Thermal microstructure measurement system

A thermal microstructure measurement system (TMMS) operates autonomously h its own internal power supply and telemeters data to a platform. A thermal array is mounted on a cross-braced frame designed to orient itself normal to existing currents with fixed sensor positioning bars protruding from the cross bars. A plurality of matched thermistors, conductivity probes and inclinometers are mounted on the frame. A compass and pressure transducer are contained in an electronics package suspended below the array. The array is deployed on a taut mooring below a subsurface float. Data are digitized, transmitted via cable to a surface buoy and then telemetered to the platform where the data is processed via a computer, recorded and/or displayed. The platform computer also sends commands to the array via telemetry.

Carver, Michael J.↗
NASA NTRS1995

The nightward ion flow scenario at Venus revisited

We indicate how existing Pioneer Venus Orbiter (PVO) data might be used to gain a better understanding of nightward ion flow in the Venusian ionosphere. Calculations based on PVO measurements made at solar maximum suggest that the global nightward flow of O(+) may be signifcantly greater than is required to maintain the observed nightside ionosphere densities. The validity of this conclusion depends upon (1) the accuracy with which the flow can be determined from the PVO ion density and velocity measurements and (2) the validity of the ionosphere theory used to estimate the required downward O(+) flux on the night side. If the measurements and theory are assumed to be accurate, the excess nightward flow implies a significant rate of ion escape from the planet, particularly at times of low solar wind dynamic pressure, Psw, when the ionopause rises to allow increased nightward flow. To illustrate a potentially important mechanism for ion escape from Venus, we present Orbiter Electron Temperature Probe (OETP) observations of plasma clouds and scavenged ionospheric plasma observed above the ionopause. We then employ OETP and Orbiter Retarding Potential Analyzer (ORPA) data to reexamine the global ion flow for average Psw conditions.

Brace, L. H.↗
NASA NTRS1972

Diffusion of chromium and aluminum in Ni-20Cr and TDNiCr /Ni-20Cr-2ThO2/.

Diffusion coefficients have been measured for Cr51 in fine- and coarse-grained TDNiCr (Ni-20Cr-2ThO2) and in fine-grained Ni-20Cr in the temperature range from 1038 to 1200 C. Selective diffusivities have also been determined for specimens of these alloys which were aluminized to give an initial surface concentration of 5.8 wt % Al. Finally, diffusion coefficients for interdiffusion of aluminum in TDNiCr and Ni-20Cr have been obtained from electron probe microanalysis of the aluminized specimens. For a given grain size and temperature there is no difference in diffusivities for chromium diffusion in TDNiCr or Ni-20Cr. Diffusion coefficients increase with decreasing grain size for both alloys. Comparison of aluminum diffusion data obtained from electron microprobe profiles with radiotracer chromium diffusivities suggests that aluminum diffuses approximately three times faster than chromium in TDNiCr and Ni-20Cr.

Seltzer, M. S.↗
NASA NTRS1992

Energetic Particles Investigation (EPI)

The EPI instrument operates during the pre-entry phase of the Galileo Probe. The main objective is the study of the energetic particle population in the inner Jovian magnetosphere and in the upper atmosphere. This will be achieved through omnidirectional measurements of electrons, protons, alpha-particles and heavy ions (Z greater than 2) and recording intensity profiles with a spatial resolution of about 0.02 Jupiter radii. Sectored data will also be obtained for electrons, protons, and alpha-particles to determine directional anisotropies and particle pitch angle distributions. The detector assembly is a two-element telescope using totally depleted circular silicon surface-barrier detectors surrounded by cylindrical tungsten shielding. The lower energy threshold of the particle species investigated during the Probe's pre-entry phase is determined by the material thickness of the Probe's rear heat shield which is required for heat protection of the scientific payload during entry into the Jovian atmosphere. The EPI instrument is combined with the Lightning and Radio Emission Detector and both instruments share one interface of the Probe's power, command, and data unit.

Fischer, H. M.↗
NASA NTRS1984

Characteristics and capacities of the NASA Lewis Research Center high precision 6.7- by 6.7-m planar near-field scanner

A very precise 6.7- by 6.7-m planar near-field scanner has recently become operational at the NASA Lewis Research Center. The scanner acquires amplitude and phase data at discrete points over a vertical rectangular grid. During the design phase for this scanner, special emphasis was given to the dimensional stability of the structures and the ease of adjustment of the rails that determine the accuracy of the scan plane. A laser measurement system is used for rail alignment and probe positioning. This has resulted in very repeatable horizontal and vertical motion of the probe cart and hence precise positioning in the plane described by the probe tip. The resulting accuracy will support near-field measurements at 60 GHz without corrections. Subsystem design including laser, electronic and mechanical and their performance is described. Summary data are presented on the scan plane flatness and environmental temperature stability. Representative near-field data and calculated far-field test results are presented. Prospective scanner improvements to increase test capability are also discussed.

Sharp, G. R.↗
NASA NTRS2022

Cosmological constraints on dark matter interactions with ordinary matter

Dark matter interactions with electrons or protons during the early Universe leave imprints on the cosmic microwave background and the matter power spectrum, and can be probed through cosmological and astrophysical observations. These interactions lead to momentum and heat exchange between the ordinary and dark matter components, which in turn results in a transfer of pressure from the ordinary to the dark matter. We explore these interactions using a diverse suite of data: cosmic microwave background anisotropies, baryon acoustic oscillations, the Lyman-α forest, and the abundance of Milky-Way subhalos. We derive constraints using model-independent parameterizations of the dark matter–electron and dark matter–proton interaction cross sections and map these constraints onto concrete dark matter models. Our constraints are complementary to other probes of dark matter interactions with ordinary matter, such as direct detection, big bang nucleosynthesis, various astrophysical systems, and accelerator based experiments. They exclude sufficiently large cross sections for a large range of dark matter masses, which cannot be accessed by direct-detection experiments due to the overburden from the Earth’s atmosphere or crust.

Manuel A. Buen-Abad↗
NASA NTRS1991

SEPAC data analysis in support of the environmental interaction program

Data analyses of the Space Experiments with Particle Accelerators (SEPAC) data and computer modeling were conducted to investigate spacecraft environmental effects associated with injection of electron beams, plasma clouds, and neutral gas clouds from the Shuttle orbiter. The data analysis indicates that Extremely Low Frequency oscillations from 150 to 200 Hz were seen in the Langmuir probe current when the beam was fired in a continuous mode. The strongest oscillations occurred when the ambient pressure was augmented by neutral gas releases from the SEPAC plasma accelerator magnetoplasma-dynamic (MPD) arcjet. To understand the dependence of spacecraft charging potential on beam density and other plasma parameters, a two-dimensional electrostatic particle code was used to simulate the injection of electron beams from an infinite conductor into a plasma. The simulations show that the conductor charging potential depends critically on the reflection coefficient of the conductor surface, which is defined as the percentage of incident particles reflected by the conductor. The ionization effects on spacecraft charging were examined by including interactions of electrons with neutral gas. The simulations show that the conductor charging potential decreases with increasing neutral background density due to the production of secondary electrons near the conductor surface. The simulations also indicate that the beam radius is generally proportional to the beam electron gyroradius when the conductor is charged to a large potential. It appears that the charge buildup at the beam stagnation point causes the beam radial expansion. A survey of the simulation results suggests that the ratio of the beam radius to the beam electron gyroradius increases with the square root of beam density and decreases inversely with beam injection velocity. These results are useful for explaining the spacecraft charging phenomena observed during SEPAC experiments from Spacelab 1.

Lin, Chin S.↗
NASA NTRS1978

Quiet-time plasma irregularities at 1400 km in the cleft region

The quiet north polar cleft at 1400 km was studied by Isis-2 instruments, and data from the retarding potential analyzer and the cylindrical electrostatic probe show that thermal plasma density fluctuations are distributed in a region between 75 deg and 82 deg invariant latitude and approximately dawn to dusk. Cleft shape and shape variations are described. Thermal ions and thermal electrons usually fluctuated together, but suprathermal electrons fluctuated independently. Data on thermal plasma patterns correlates fairly well with observations of soft particles and auroral optical emissions and not as well with measurements of high-energy particles. The data suggest that the energy source for the thermal irregularities is associated with soft particles and that precipitating high-energy particles do not drive the thermal plasma at these altitudes.

Kayser, S. E.↗
NASA NTRS1988

Automatic Inspection During Machining

In experimental manufacturing process, numerically-controlled machine tool temporarily converts into inspection machine by installing electronic touch probes and specially-developed numerical-control software. Software drives probes in paths to and on newly machined parts and collects data on dimensions of parts.

Ransom, Clyde L.↗
NASA NTRS1988

Model of Jovian F region ionosphere

To date, seven electron density profiles of the Jovian ionosphere have been furnished by the radio occultation experiments aboard the Pioneer and Voyager space probes. The data correspond to various localities (latitudes and longitudes) and times (dawn and dusk) and phases of sunspot cycle (high and low). This renders comparative studies difficult. Nevertheless, the possibility of existence of diurnal variation, equatorial anomaly, and auroral particle precipitation in the Jovian ionosphere have been put forth. The grand magnitude and depth of the equatorial anomaly, in particular, is a matter of great interest and speculation. Correct interpretations of the data and the physical processes in the complex Jovian atmospheric environment will remain a major task for the Aeronomer for decades to come. Model studies of a Jovian ionosphere created by solar EUV radiation and subjected to model ExB drifts showed that equatorial anomaly similar to that in the terrestrial ionosphere can indeed be produced in the Jovian ionosphere. However, owing to the difference in size and rotation period of the two planets and the ionic compositions, much larger drift velocities are required to produce a comparable anomaly in the Jovian atmosphere.

Tan, A.↗
NASA NTRS1989

Comparison of experimental and calculated attachment rate constants for CFCl3 and CCl4 in the temperature range 294-500 K

Electron-attachment cross sections and rate constants have been measured and calculated for the dissociative attachment processes e + CFCl3 - Cl(-) + CFCl2 and e + CCl4 - Cl(-) + CCl3. Good agreement over the electron-energy range 1-200 meV is found in energy dependence between present calculated cross sections and experimental cross sections at 300 K. The same calculation, with suitable adjustment of thermal populations, was used to calculate electron-attachment rate constants in the range 50-600 K. Experimental rate constants for CFCl3 and CCl4 were measured at temperatures of 294, 404, and 496 K (CFCl3) and 294, 400, and 500 K (CCl4) using the Cavalleri electron-density sampling method. Good agreement is found between present measurements and calculations, poor agreement with flowing-afterglow Langmuir-probe (FALP) data in CFCl3 at the higher temperatures, and reasonable agreement with FALP data for CCl4.

Orient, O. J.↗
NASA NTRS1974

Digital temperature sensor performance assessment report

Performance assessment data accumulated during exposure of the digital temperature sensor to simulated shuttle flight type environments are presented. The test parameters were specifically designed to check the sensor for its: (1) ability to resolve temperature relative to the design specifications; (2) ability to maintain accuracy after interchanging the temperature probes with each electronics interface assembly; (3) stability (i.e., satisfactory operation and accuracy during and after exposure to flight environments); and (4) repeatability, or its ability to produce the same output on subsequent exposures to the identical stimulus. Equipment list, test descriptions, data summary, and conclusions are included.

Canniff, J. H.↗
NASA NTRS1995

Interplanetary Scintillation

Interplanetary scintillation (IPS) has been used as a diagnostic of solar wind speed and interplanetary plasma turbulence, allowing inference of speed and electron density power spectrum close to the Sun and out of the ecliptic. In that context, IPS is 'signal' and provides scientifically interesting data. IPS is also of interest because amplitude and phase perturbations imposed on radio waves are 'noise' for telemetry and precision Doppler tracking of deep space probes and for some radio astronomical observations. This paper briefly reviews the connection between scattering observables and the electron density power spectrum. Interplanetary phase scintillation on time scales of 100 to 10 000 seconds is an important noise in mass determinations of small solar system bodies during space-probe fly-bys and in searches for low-frequency gravitational radiation.

waves deep space probes electron density power spe↗
NASA NTRS1977

Correction factors for on-line microprobe analysis of multielement alloy systems

An on-line correction technique was developed for the conversion of electron probe X-ray intensities into concentrations of emitting elements. This technique consisted of off-line calculation and representation of binary interaction data which were read into an on-line minicomputer to calculate variable correction coefficients. These coefficients were used to correct the X-ray data without significantly increasing computer core requirements. The binary interaction data were obtained by running Colby's MAGIC 4 program in the reverse mode. The data for each binary interaction were represented by polynomial coefficients obtained by least-squares fitting a third-order polynomial. Polynomial coefficients were generated for most of the common binary interactions at different accelerating potentials and are included. Results are presented for the analyses of several alloy standards to demonstrate the applicability of this correction procedure.

Unnam, J.↗
NASA NTRS1988

Studies of high latitude mesospheric turbulence by radar and rocket. II - Measurements of small scale turbulence

Measurements of mesospheric small scale turbulence and associated larger scale wave structures were obtained from rocket probe flights during equinox in spring 1985. The measurements were verified by data from the mesosphere-stratosphere-troposphere radar at Poker Flat, Alaska. Electron density irregularities down to an altitude of about 62 km and fluctuations in positive ion density in the altitude region from 50 to 90 km were measured. Turbulence in the inertial subrange was observed at heights where the fluctuations generally were largest. Measurement of background electron density exhibited gradients relative to the monotonically increasing density profile, suggesting the presence of large amplitude wave motions transporting the plasma by mixing. The radar detected the occurrence of 1-3 km wavelike perturbations superimposed on a 7-km wave in the wind velocity field. It is suggested that the 1-3 km waves are more important in the transport of energy and momentum and in the production of turbulence in the lower mesosphere.

Blood, S. P.↗