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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

The effect of wave-particle interactions on the polar wind: Preliminary results

A Monte Carlo simulation was developed in order to study the effects of wave-particle interactions (WPI) on the plasma outflow in the polar wind. The simulation also considered the other mechanisms included in the `classical' polar wind studies such as gravity, the polarization electrostatic field, and the divergence of geomagnetic field lines. Although the plasma consisted of electrons, H(+) and O(+) ions, we emphasized the behavior of H(+) in this preliminary study. The ion distribution function, as well as the profiles of its moments (density, drift velocity, temperatures, etc.) were found for different levels of WPI, that is, for different values of normalized diffusion rates in the velocity space (normalized D(sub perpendicular) H(+)). We found that as the WPI strength increases: (1) the ion drift velocity increases and its density decreases; (2) the perpendicular temperature T(sub perpendicular) (H(+)) increases; (3) the parallel temperature T(sub parallel) (H(+)) first decreases and then increases due to the balance between the parallel adiabatic cooling and the transfer of the energy from the perpendicular to the parallel direction; and (4) the temperature anisotropy ((T(sub parallel) (H(+))/T(sub perpendicular) (H(+)) is reduced and even reversed in some cases. For strong WPI (normalized D(sub perpendicular) (H(+) much greater than 1), the ion distribution function shows weak conic features at high altitudes.

Barakat, A. R.↗
NASA NTRS1976

An Empirical Model for the Mixing of a Row of Dilution Jets with a Confined Crossflow

An empirical model was developed for predicting the temperature distribution downstream from a row of cool jets injected normally into a hot confined crossflow. The model is based on the assumption that all properly non-dimensionalized vertical temperature profiles can be expressed in a self-similar form. The scaling parameters in this form were correlated in terms of the independent flow and geometric variables. The effect of parametric variation of each of the independent variables on the experimental and predicted profiles are examined. The predicted distributions show excellent agreement with the data over a wide range of the independent variables.

Holdeman, J. D.↗
NASA NTRS1976

An empirical model for the mixing of a row of dilution jets with a confined crossflow

An empirical model has been developed for predicting the temperature distribution downstream of a row of cool jets injected normal to a hot confined crossflow. The model is based on the assumption that all properly non-dimensionalized vertical temperature profiles can be expressed in a self-similar form. The scaling parameters in this form have been correlated in terms of the independent flow and geometric variables. The effect of parametric variation of each of the independent variables on the experimental and predicted profiles are examined. The predicted distributions show excellent agreement with the data over a wide range of the independent variables.

Holdeman, J. D.↗
NASA NTRS1969

Substitution of stable isotopes in Chlorella

Replacement of biologically important isotopes in the alga Chlorella by corresponding heavier stable isotopes produces increasingly greater deviations from the normal cell size and changes the quality and distribution of certain cellular components. The usefulness of isotopically altered organisms increases interest in the study of such permuted organisms.

Flaumenhaft, E.↗
NASA NTRS1973

Ultraviolet observations of peculiar B and A stars from OAO-2

Plotted photometric data in two far-ultraviolet bandpasses at 1550 and 1430 A for both normal and peculiar stars are compared for flux distribution. It is shown that the ultraviolet flux distribution of an A sub p or B sub p star is consistent with its spectral class and is notably inconsistent with its UBV colors. It is assumed that the helium line strength suppression mechanism is related to an abnormal atmospheric structure in the peculiar stars.

Leckrone, D. S.↗
NASA NTRS1979

Further developments in simple total energy sensors

A simple total energy probe concept using principles of laminar flow around a cylinder and pressure distribution is reviewed and flow fields around cylinders normal to and inclined to the flow are described. A variety of bent-up probe configurations were tested to explore variations in geometry. Test results are presented on the effects of sensor length, hole location, and angle of sweep. Comparisons are made with other probe tests reported in the literature. Damping restrictors and their use in filtering gusts are summarized. Flow field effects, indicating the variables involved for different mounting locations on aircraft, are discussed.

Nicks, O. W.↗
NASA NTRS1979

Lunar laser ranging data identification and management

Activity under the subject grant during the first half of fiscal year 1979 at the University of Texas at Austin is reported. Raw lunar laser ranging data submitted by McDonald Observatory, Fort Davis, Texas and by the Australian Division of National Mapping at Orroral Valley, Australia were processed. This processing includes the filtering of signal events from noise photons, normal point formation, data archive management, and data distribution. System-wide program maintenance and up-grade carried out wherever and whenever necessary. Lunar laser ranging data is being transmitted from Austin to Paris for the extraction of earth rotation information during the EROLD campaign.

Source record↗
NASA NTRS1981

The Shuttle tile story

The structural problems associated with the reusable thermal protection system (TPS) of the Space Shuttle Orbiter are assessed. The ceramic insulation was placed on the aluminum in the form of about 30,000 tiles over approximately 70% of the Orbiter's exterior. The tiles were bonded to felt pads, and then the tile-pad structure was attached to the aluminum skin. As Orbiter design progressed, it was discovered that the TPS would have to withstand loads greater than initially predicted. The group tensile strength was less than that of the individual components. This was the primary factor contributing to the delay of the first flight. Values are given for Orbiter isotherms during a normal flight as well as the corresponding TPS distribution. The complete TPS assemblage is shown schematically, noting the sequence of assembling the tile components into a testing specimen. It is noted that tensile loads are applied to the strain-isolation path at discrete regions along transverse fiber bundles, causing a 50% reduction in system tensile strength. Procedures for strengthening the interface between the insulation and strain-isolation path are discussed and flight-simulation tests are outlined.

Cooper, P. A.↗
NASA NTRS1982

Model fitting of the Algol binaries

Energy distribution of the component stars of the Algol type semidetached binaries were studied by combining IUE low dispersion spectra with optical scans made with the same resolution. In most cases the flux distributions are matched by Kuruz model atmospheres with normal solar composition. Deviations from normal atmospheres which indicate a higher level of activity and interaction in the binaries are examined. Eclipse observations in U Cep and V356 Sgr reveal emission lines of the W serpentis type.

Dobias, J. J.↗
NASA NTRS1986

Three dimensional unsteady aerodynamics and aeroelastic response of advanced turboprops

A method for the prediction of steady and unsteady aerodynamic loads and aeroelastic response of advanced turboprops is presented. The aerodynamic analysis uses three dimensional unsteady linearized compressible flow theory to compute the blade pressure distribution. The aeroelastic analysis is based on a normal mode representation of the structure. The method is applicable to both conventional and advanced turbo-prop configurations, provided that blade stall and transonic shock waves are not important factors. Aerodynamic results are presented which validate the model in various limits by comparisons to alternative theories and experimental data. Finally, results of a stability analysis of an advanced turboprop are given, with comparisons to measurements made at NASA Lewis Research Center.

Williams, M. H.↗
NASA NTRS1988

Results of APL rain gauge network measurements in mid-Atlantic coast region and comparisons of distributions with CCIR models

In this effort are described cumulative rain rate distributions for a network of nine tipping bucket rain gauge systems located in the mid-Atlantic coast region in the vicinity of the NASA Wallops Flight Facility, Wallops Island, Virginia. The rain gauges are situated within a gridded region of dimensions of 47 km east-west by 70 km north-south. Distributions are presented for the individual site measurements and the network average for the year period June 1, 1986 through May 31, 1987. A previous six year average distribution derived from measurements at one of the site locations is also presented. Comparisons are given of the network average, the CCIR (International Radio Consultative Committee) climatic zone, and the CCIR functional model distributions, the latter of which approximates a log normal at the lower rain rate and a gamma function at the higher rates.

Goldhirsh, Julius↗
NASA NTRS1987

Current CFD efforts in projectile aerodynamics

Information is given in viewgraph form on current computational fluid dynamics (CFD) efforts in projectile aerodynamics. Topics covered include spinning projectiles, fin stabilized projectiles, model geometry, the variation of base drag with base bleed, the variation of normal force with Mach number, and chordwise pressure distribution.

Nietubicz, Charles J.↗
NASA NTRS1957

The Effects of Boundary-layer Separation over Bodies of Revolution with Conical Tail Flares

The magnitude and the effects of boundary-layer separation on normal-force-curve slopes, centers of pressure, pressure distributions, and lift and drag coefficients were determined for various bodies of revolution with conical tail flares at Mach numbers from 3.0 to 6.3. Some of the experimental results are compared to theoretical predictions of the aerodynamic characteristics of the bodies.

Dennis, David H↗
NASA NTRS1993

Fluvial erosion on Mars: Implications for paleoclimatic change

Fluvial erosion on Mars has been nonuniform in both time and space. Viking orbiter images reveal a variety of different aged terrains exhibiting widely different degrees of erosion. Based on our terrestrial analog studies, rates of fluvial erosion associated with the formation of many of the valleys on Mars is probably on the order of hundreds of meters per million years, while rates of erosion associated with the formation of the outflow channels probably ranged from tens to hundreds of meters in several weeks to months. However, estimated rates of erosion of the Martian surface at the Viking Lander sites are extremely low, on the order of 1 micron/yr or less. At most this would result in a meter of material removed per million years, and it is unlikely that such an erosion rate would be able to produce the degree of geomorphic work required to form the fluvial features present elsewhere on the surface. In addition, single terrain units are not eroded uniformly by fluvial processes. Instead fluvial valleys, particularly in the cratered highlands, typically are situated in clusters surrounded by vast expanses of uneroded surfaces of the same apparent lithologic, structural, and hydrological setting. Clearly throughout its geologic history, Mars has experienced a nonuniformity in erosion rates. By estimating the amount of fluvial erosion on dissected terrains and by studying the spatial distribution of those locations which have experienced above normal erosion rates, it should be possible to place further constraints on Mars' paleoclimatic history.

Gulick, Virginia C.↗
NASA NTRS1994

Variable extinction in HD 45677 and the evolution of dust grains in pre-main-sequence disks

Changes in the UV extinction and IR emission were sought in the Herbig Ae/Be star candidate HD 45677 (= FS CMa) by comparing UV, optical, and IR observations made approximately 10 yr apart. HD 45677 varied significantly, becoming more than 50% brighter in the UV and optical than it was a decade ago. A comparison of the observations between epochs indicates that if the variations are due to changes in dust obscuration, the dust acts as a gray absorber into the near-IR and must be depleted in grains smaller than 1 micron. This is similar to the results obtained on the circumstellar disks of stars like Vega and Beta Pic, and suggests that radiation pressure may be responsible for the small-grain depletion. In addition, the total IR flux seems to have declined, indicating a decrease in the total mass of the dust envelope that contributes to the IR emission in this part of the spectrum. Due to the anomalous nature of the extinction, the use of normal extinction curves to deredden the spectral energy distributions of stars with circumstellar dust may lead to significant errors and should be used with great caution.

Sitko, Michael L.↗
NASA NTRS1996

High Temperature Superconducting Magnets with Active Control for Attraction Levitation Transport Applications

A research program, involving 3 British universities, directed at quantifying the controllability of High Temperature Superconducting (HTS) magnets for use in attraction levitation transport systems will be described. The work includes measurement of loss mechanisms for iron cored HTS magnets which need to produce a flux density of approx. 1 tesla in the airgap between the magnet poles and a ferromagnetic rail. This flux density needs to be maintained and this is done by introducing small variations of the magnet current using a feedback loop, at frequencies up to 10 Hz to compensate for load changes, track variation etc. The test magnet assemblies constructed so far will be described and the studies and modelling of designs for a practical levitation demonstrator (using commercially obtained HTS tape) will be discussed with particular emphasis on how the field distribution and its components, e.g., the component vector normal to the broad face of the tape, can radically affect design philosophy compared to the classical electrical engineering approach. Although specifically aimed at levitation transport the controllability data obtained have implications for a much wider range of applications.

Jones, Harry↗
NASA NTRS1999

Statistical Quality Control of Moisture Data in GEOS DAS

A new statistical quality control algorithm was recently implemented in the Goddard Earth Observing System Data Assimilation System (GEOS DAS). The final step in the algorithm consists of an adaptive buddy check that either accepts or rejects outlier observations based on a local statistical analysis of nearby data. A basic assumption in any such test is that the observed field is spatially coherent, in the sense that nearby data can be expected to confirm each other. However, the buddy check resulted in excessive rejection of moisture data, especially during the Northern Hemisphere summer. The analysis moisture variable in GEOS DAS is water vapor mixing ratio. Observational evidence shows that the distribution of mixing ratio errors is far from normal. Furthermore, spatial correlations among mixing ratio errors are highly anisotropic and difficult to identify. Both factors contribute to the poor performance of the statistical quality control algorithm. To alleviate the problem, we applied the buddy check to relative humidity data instead. This variable explicitly depends on temperature and therefore exhibits a much greater spatial coherence. As a result, reject rates of moisture data are much more reasonable and homogeneous in time and space.

Dee, D. P.↗