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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 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Induced pressure distribution of a jet in a crossflow

The turbulent flow of a subsonic round jet exhausting perpendicularly from a flat plate into a subsonic crosswind of the same temperature was investigated in the Langley V/STOL tunnel. The large test section of this tunnel made it possible to use a jet with the relatively large diameter of 10.16 cm. Pressures were measured on the flat plate at over 400 locations to provide a detailed description of the static pressure distribution. Results are presented in tabular and graphical forms for jet to crossflow velocity ratios ranging from 2 to 10, and comparisons are made with results of other experiments. The results indicate that the dominant flow parameter affecting the pressure distributions is the ratio of jet to crossflow velocities. The distribution of turbulence on the plate also appears to be a function of velocity ratio.

Fearn, R. L.↗
NASA NTRS1975

Research study on multi-KW-DC distribution system

A detailed definition of the HVDC test facility and the equipment required to implement the test program are provided. The basic elements of the test facility are illustrated, and consist of: the power source, conventional and digital supervision and control equipment, power distribution harness and simulated loads. The regulated dc power supplies provide steady-state power up to 36 KW at 120 VDC. Power for simulated line faults will be obtained from two banks of 90 ampere-hour lead-acid batteries. The relative merits of conventional and multiplexed power control will be demonstrated by the Supervision and Monitor Unit (SMU) and the Automatically Controlled Electrical Systems (ACES) hardware. The distribution harness is supported by a metal duct which is bonded to all component structures and functions as the system ground plane. The load banks contain passive resistance and reactance loads, solid state power controllers and active pulse width modulated loads. The HVDC test facility is designed to simulate a power distribution system for large aerospace vehicles.

Berkery, E. A.↗
NASA NTRS1975

Periodic analysis of total ozone and its vertical distribution

Both total ozone and vertical distribution ozone data from the period 1957 to 1972 are analyzed. For total ozone, improved monthly zonal means for both hemispheres are computed by weighting individual station monthly means by a factor which compensates for the close grouping of stations in certain regions of latitude bands. Longitudinal variability show maxima in summer in both hemispheres, but, in winter, only in the Northern Hemisphere. The geographical distributions of the long term mean, and the annual, quasibiennial and semiannual waves in total ozone over the Northern Hemisphere are presented. The extratropical amplitude of the annual wave is by far the largest of the three, as much as 120 m atm cm over northern Siberia. There is a tendency for all three waves to have maxima in high latitudes. Monthly means of the vertical distribution of ozone determined from 3 to 8 years of ozonesonde data over North America are presented. Number density is highest in the Arctic near 18 km. The region of maximum number density slopes upward toward 10 N, where the long term mean is 45 x 10 to the 11th power molecules cm/3 near 26 km.

Wilcox, R. W.↗
NASA NTRS1974

Angular distribution of photoelectrons from atomic oxygen, nitrogen and carbon

The angular distributions of photoelectrons from atomic oxygen, nitrogen, and carbon are calculated. Both Hartree-Fock and Hartree-Slater (Herman-Skillman) wave functions are used for oxygen, and the agreement is excellent; thus only Hartree-Slater functions are used for carbon and nitrogen. The pitch-angle distribution of photoelectrons is discussed, and it is shown that previous approximations of energy-independent isotropic or sin squared theta distributions are at odds with the authors' results, which vary with energy. This variation with energy is discussed, as is the reliability of these calculations.

Manson, S. J.↗
NASA NTRS1975

On the Laplace transform for distributions

A new characterization of the Laplace transform for Schwartz distributions is developed, using sequences of linear transformations on the space of distributions. The standard theorems on analyticity, uniqueness and invertibility of the transform are proved, using the new characterization as the definition of the Laplace transform. It is shown that this sequential definition is equivalent to Schwartz's extension of the ordinary Laplace transform to distributions which he obtained from the Fourier transform.

Price, D. B.↗
NASA NTRS1975

Analysis of measured airfoil pressure distributions

A method for evaluating the Glauert coefficients from airfoil pressure distributions is investigated. The linear operating range of the airfoils in steady-state and periodic operating conditions are considered. A rational method for quantitatively characterizing airfoil pressure distributions relative to their geometry and aerodynamic operating environment is developed. The characteristics of the airfoil operating environment is determined from its measured pressure distribution.

Piziali, R. A.↗
NASA NTRS1975

Elemental composition and size distribution of particulates in Cleveland, Ohio

Measurements were made of the elemental particle size distribution at five contrasting urban environments with different source-type distributions in Cleveland, Ohio. Air quality conditions ranged from normal to air pollution alert levels. A parallel network of high-volume cascade impactors (5-state) were used for simultaneous sampling on glass fiber surfaces for mass determinations and on Whatman-41 surfaces for elemental analysis by neutron activation for 25 elements. The elemental data are assessed in terms of distribution functions and interrelationships and are compared between locations as a function of resultant wind direction in an attempt to relate the findings to sources.

King, R. B.↗
NASA NTRS1976

Analysis of field size distributions, LACIE test sites 5029, 5033, and 5039, Anhwei Province, People's Republic of China

A study was made of the field size distributions for LACIE test sites 5029, 5033, and 5039, People's Republic of China. Field lengths and widths were measured from LANDSAT imagery, and field area was statistically modeled. Field size parameters have log-normal or Poisson frequency distributions. These were normalized to the Gaussian distribution and theoretical population curves were made. When compared to fields in other areas of the same country measured in the previous study, field lengths and widths in the three LACIE test sites were 2 to 3 times smaller and areas were smaller by an order of magnitude.

Podwysocki, M. H.↗
NASA NTRS1976

The galactic distribution (in radius and Z) of interstellar molecular hydrogen

Observations of the galactic longitude and latitude distributions of gamma = 2.6 mm CO emission are presented. Analysis of this spectral line data yields the large scale distribution of molecular clouds in the galactic disk and their z-distribution out of the disk. Strong maxima in the number of molecular clouds occur in the galactic nucleus and at galactic radii 4-8 kpc. The peak at 4-8 kpc correlates well with a region of enhanced 100 Mev gamma ray emissivity. This correlation strongly supports the conclusion that the gamma rays are produced as a result of cosmic ray interactions in molecular H2 clouds rather than HI. One important implication of this is that the interstellar magnetic field lines to which cosmic rays are confined must therefore not be excluded from these dense clouds. The width of the cloud layer perpendicular to galactic plane between half density points is 105 + or - 15 pc near the 5.5 kpc peak. The total mass of molecular gas in the interior of the galaxy exceeds that of atomic hydrogen.

Scoville, N. Z.↗
NASA NTRS1975

Comments on the quiet sun brightness distribution at 1.2 mm wavelength

Data on the center-to-limb brightness distribution of the quiet sun at 1.2-mm wavelength are reanalyzed. The observed brightness distribution at this wavelength is plotted along the equatorial direction and analyzed to determine whether it is uniform, limb-brightened, or limb-darkened. It is concluded that at the present time, there is no evidence for a uniform or limb-brightened distribution at 1.2 mm from either an observational or theoretical point of view.

Kundu, M. R.↗
NASA NTRS1975

Elemental composition and size distribution of particulates in Cleveland, Ohio

Measurements have been made of the elemental particle size distribution at five contrasting urban environments with different source-type distributions in Cleveland, Ohio. Air quality conditions ranged from normal to air pollution alert levels. A parallel network of high-volume cascade impactors (5-stage) were used for simultaneous sampling on glass fiber surfaces for mass determinations and on Whatman-41 surfaces for elemental analysis by neutron activation for 25 elements. The elemental data are assessed in terms of distribution functions and interrelationships and are compared between locations as a function of resultant wind direction in an attempt to relate the findings to sources.

Leibecki, H. F.↗
NASA NTRS1976

Distribution of small channels on the Martian surface

The distribution of small channels on Mars has been mapped from Mariner 9 images at the 1:5,000,000 scale. The small channels referred to here are small valleys ranging in width from the resolution limit of the Mariner 9 wide-angle images (about 1 km) to about 10 km. The greatest density of small channels occurs in dark cratered terrain. This dark zone forms a broad subequatorial band around the planet. The observed distribution may be the result of decreased small-channel visibility in bright areas due to obscuration by a high albedo dust or sediment mantle. Crater densities within two small-channel segments show crater size-frequency distributions consistent with those of the oldest of the heavily cratered plains units. Such crater densities coupled with the almost exclusive occurrence of small channels in old cratered terrain and the generally degraded appearance of small channels in the high-resolution images (about 100 m) imply a major episode of small-channel formation early in Martian geologic history.

Pieri, D.↗
NASA NTRS1976

On the detection of a cometary mass distribution

The problem of detecting a possible cometary distribution on the fringes of the solar system is examined. The acceleration of a space probe due to a hypothetical cometary mass distribution with the surface density rising to a maximum and subsequently falling off with increasing distance from the sun is analyzed. The total minimum detectable cometary mass for the Pioneer and Mariner spacecraft is estimated on the basis of this model to be on the order of 1000 earth masses. Precision tracking of deep space probes is less sensitive by three orders of magnitude for the detection of an unseen cometary mass distribution at the fringes of the solar system than are the secular perturbations of long-period comets.

Boss, A. P.↗
NASA NTRS1976

Angular distributions of electrons of energy greater than 0.06 MeV in the Jovian magnetosphere

Measurements of the angular distribution of electron intensity in the Jupiter magnetosphere were made by the University of Iowa experiment on Pioneer 10. The data were from three directional particle detectors with effective integral threshold of 0.06, 0.55 and 0.5 MeV respectively. It was discovered that the central core of the magnetosphere for radial distances less than 12 Jovian radii is dominated by pitch angle distributions strongly peaked at alpha = 90 degrees, while the region of radial distances 12-25 Jovian radii shows bidirectional and approximately equal maxima at alpha = 0 and 180 degrees. Substantial field-aligned streaming was detected on two occasions, each of about 1 hour duration. No distinctive effects on angular distributions were observed near the L shells of satellites.

Sentman, D. D.↗
NASA NTRS1976

Electron angular distributions above the day side auroral oval

An electrostatic analyzer, a Lepedea, was employed on the low-altitude satellite Ariel 4 in order to gain pitch angle distributions of electron intensities with good temporal resolution within the energy range 205 eV to 12.5 keV over the day side auroral oval. Two major precipitation zones were encountered: an equatorward zone of broad spectra with intensities of about 10 to the 4th el/sq cm/s/sr/eV and a poleward zone, the polar cusp, with intensities typical of those of the magnetosheath. Angular distributions within the equatorward zone are generally isotropic outside of the atmospheric backscatter cone. The precipitation mechanism would appear to be pitch angle scattering near the distant magnetic equator. In contrast, pitch angle distributions within the polar cusp are often found to be strongly field aligned with intensities within the atmospheric loss cone greater by factors of about 10 than the mirroring intensities.

Craven, J. D.↗
NASA NTRS1976

Deviation from a Maxwellian velocity distribution in regions of interstellar molecular hydrogen

The deviation from a Maxwellian velocity distribution caused by excitation of the J = 2 rotational level of parahydrogen (followed by radiative decay) in a molecular hydrogen gas is investigated. It is noted that inelastic collisions deplete the high-velocity tail of the distribution, while elastic collisions tend to refill it; the resulting steady-state distribution has a small depletion in the tail which slightly reduces the cooling rate of the gas. The elastic-collision transport is approximated by a continuous process, a simplified expression is obtained for the inelastic-collision operator, and the Boltzmann equation is then solved analytically. A correction to the inelastic-collision rate is evaluated, and it is found that the relative magnitude of the effect of tail depletion on the inelastic-collision rate is strongly temperature-dependent. The critical molecular density above which the J = 2 level deexcites by superelastic collisions is shown to be a weak function of temperature.

Gould, R. J.↗
NASA NTRS1975

A distributed computing approach to mission operations support

Computing mission operation support includes orbit determination, attitude processing, maneuver computation, resource scheduling, etc. The large-scale third-generation distributed computer network discussed is capable of fulfilling these dynamic requirements. It is shown that distribution of resources and control leads to increased reliability, and exhibits potential for incremental growth. Through functional specialization, a distributed system may be tuned to very specific operational requirements. Fundamental to the approach is the notion of process-to-process communication, which is effected through a high-bandwidth communications network. Both resource-sharing and load-sharing may be realized in the system.

Larsen, R. L.↗
NASA NTRS1977

The galactic distribution (in radius and Z) of interstellar molecular hydrogen

Observations of the galactic longitude and latitude distributions of lambda = 2.6 mm CO emission are presented. Analysis of these spectral-line data yields the large-scale distribution of molecular clouds in the galactic disk and their z-distribution out of the disk. Strong maxima in the number of molecular clouds occur in the galactic nucleus and at galactic radii 4 to 8 kpc. The peak at 4 to 8 kpc correlates well with a region of enhanced 100-MeV gamma-ray emissivity. This correlation strongly supports the conclusion that the gamma-rays are produced as a result of cosmic ray interactions in molecular H2 clouds rather than in H(I). The width of the cloud layer perpendicular to the galactic plane between half-density points is 105 plus or minus 15 pc near the 5.5-kpc peak. The total mass of molecular gas in the interior of the galaxy exceeds that of atomic hydrogen and is 30 to the 9th power solar mass based on these observations.

Scoville, N. Z.↗