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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Windblown Features on Venus and Geological Mapping

The objectives of this study were to: 1) develop a global data base of aeolian features by searching Magellan coverage for possible time-variable wind streaks, 2) analyze the data base to characterize aeolian features and processes on Venus, 3) apply the analysis to assessments of wind patterns near the surface and for comparisons with atmospheric circulation models, 4) analyze shuttle radar data acquired for aeolian features on Earth to determine their radar characteristics, and 5) conduct geological mapping of two quadrangles. Wind, or aeolian, features are observed on Venus and aeolian processes play a role in modifying its surface. Analysis of features resulting from aeolian processes provides insight into characteristics of both the atmosphere and the surface. Wind related features identified on Venus include erosional landforms (yardangs), depositional dune fields, and features resulting from the interaction of the atmosphere and crater ejecta at the time of impact. The most abundant aeolian features are various wind streaks. Their discovery on Venus afforded the opportunity to learn about the interaction of the atmosphere and surface, both for the identification of sediments and in mapping near-surface winds.

Greeley, Ronald↗
NASA NTRS1987

High intensity 5 eV atomic oxygen source and Low Earth Orbit (LEO) simulation facility

An atomic oxygen exposure facility has been developed for studies of material degradation. The goal of these studies is to provide design criteria and information for the manufacture of long life (20 to 30 years) construction materials for use in LEO. The studies that are being undertaken using the facility will provide: absolute reaction cross sections for use in engineering design problems; formulations of reaction mechanisms; and calibration of flight hardware (mass spectrometers, etc.) in order to directly relate experiments performed in LEO to ground based investigations. The facility consists of: (1) a CW laser sustained discharge source of O atoms having a variable energy up to 5 eV and an intensity between 10(15) and 10(17) O atoms s(-1) cm(-2); (2) an atomic beam formation and diagnostics system consisting of various stages of differential pumping, a mass spectrometer detector, and a time of flight analyzer; (3) a spinning rotor viscometer for absolute O atom flux measurements; and (4) provision for using the system for calibration of actual flight instruments. Surface analysis equipment is available for the characterization of material surfaces before and after exposure to O atoms.

Cross, J. B.↗
NASA NTRS1980

Practical applications of surface analytic tools in tribology

Many of the currently, widely used tools available for surface analysis are described. Those which have the highest applicability for giving elemental and/or compound analysis for problems of interest in tribology and are truly surface sensitive (that is, less than 10 atomic layers) are presented. The latter group is evaluated in detail in terms of strengths and weaknesses. Emphasis is placed on post facto analysis of experiments performed under 'real' conditions (e.g., in air with lubricants). It is further indicated that such equipment could be used for screening and quality control.

Ferrante, J.↗
NASA NTRS1986

Development of a variational SEASAT data analysis technique

Oceans are data-sparse areas in terms of conventional weather observations. The surface pressure field obtained solely by analyzing the conventional weather data is not expected to possess high accuracy. On the other hand, in entering asynoptic data such as satellite-derived temperature soundings into an atmospheric prediction system, an improved surface analysis is crucial for obtaining more accurate weather predictions because the mass distribution of the entire atmosphere will be better represented in the system as a result of the more accurate surface pressure field. In order to obtain improved surface pressure analyses over the oceans, a variational adjustment technique was developed to help blend the densely distributed surface wind data derived from the SEASAT-A radar observations into the sparsely distributed conventional pressure data. A simple marine boundary layer scheme employed in the adjustment technique was discussed. In addition, a few aspects of the current technique were determined by numerical experiments.

Sasaki, Y. K.↗
NASA NTRS1986

OSAC analysis of the Far Ultraviolet Spectroscopic Explorer (FUSE) telescope

An investigation is made of the sensitivity of the image quality for the proposed FUSE telescope to mirror misalignments and a wide spatial frequency range of figure errors. Representative figure error data was obtained for the analysis from measurements made on the SEUTS (Solar Extreme Ultraviolet Telescope Spectrograph) telescope mirrors. The tolerancing analysis was carried out with the aid of the Optical Surface Analysis Code (OSAC) program.

Saha, Timo T.↗
NASA NTRS2004

Sub-Micrometer Scale Minor Element Mapping in Interplanetary Dust Particles: A Test for Stratospheric Contamination

Combined X-ray microprobe (XRM), energy dispersive x-ray fluorescence using a Transmission Electron Microscope (TEM), and electron microprobe measurements have determined that the average bulk chemical composition of the interplanetary dust particles (IDPs) collected from the Earth s stratosphere is enriched relative to the CI meteorite composition by a factor of 2 to 4 for carbon and for the moderately volatile elements Na, K, P, Mn, Cu, Zn, Ga, Ge, and Se, and enriched to approximately 30 times CI for Br. However, Jessberger et al., who have reported similar bulk enrichments using Proton Induced X-ray Emission (PIXE), attribute the enrichments to contamination by meteor-derived atmospheric aerosols during the several weeks these IDPs reside in the Earth s atmosphere prior to collection. Using scanning Auger spectroscopy, a very sensitive surface analysis technique, Mackinnon and Mogk have observed S contamination on the surface of IDPs, presumably due to the accretion of sulfate aerosols during stratospheric residence. But the S-rich layer they detected was so thin (approximately 100 angstroms thick) that the total amount of S on the surface was too small to significantly perturb the bulk S-content of a chondritic IDP. Stephan et al. provide support for the contamination hypothesis by reporting the enrichment of Br on the edges of the IDPs using Time-of-Flight Secondary-Ion Mass-Spectrometry (TOFSIMS), but TOF-SIMS is notorious for producing false edge-effects, particularly on irregularly-shaped samples like IDPs. Sutton et al. mapped the spatial distribution of Fe, Ni, Zn, Br, and Sr, at the approximately 2 m scale, in four IDPs using element-specific x-ray fluorescence (XRF) computed microtomography. They found the moderately volatile elements Zn and Br, although spatially inhomogeneous, were not concentrated on the surface of any of the IDPs they examined, suggesting that the Zn and the Br enrichments in the IDPs are not due to contamination during stratospheric residence.

Flynn, G. J.↗
NASA NTRS1993

Airport surface operations requirements analysis

This report documents the results of the Airport Surface Operations Requirements Analysis (ASORA) study. This study was conducted in response to task 24 of NASA Contract NAS1-18027. This study is part of NASA LaRC's Low Visibility Surface Operations program, which is designed to eliminate the constraints on all-weather arrival/departure operations due to the airport/aircraft ground system. The goal of this program is to provide the capability for safe and efficient aircraft operations on the airport surface during low visibility conditions down to zero. The ASORA study objectives were to (1) develop requirements for operation on the airport surface in visibilities down to zero; (2) survey and evaluate likely technologies; (3) develop candidate concepts to meet the requirements; and (4) select the most suitable concept based on cost/benefit factors.

Groce, John L.↗
NASA NTRS1992

Screen Cage Ion Plating (SCIP) and scratch testing of polycrystalline aluminum oxide

A screen cage ion plating (SCIP) technique was developed to apply silver films on electrically nonconducting aluminum oxide. It is shown that SCIP has remarkable throwing power; surfaces to be coated need not be in direct line of sight with the evaporation source. Scratch tests, employing a diamond stylus with a 200 micro m radius tip, were performed on uncoated and on silver coated alumina. Subsequent surface analysis show that a significant amount of silver remains on the scratched surfaces, even in areas where high stylus load produced severe crack patterns in the ceramic. Friction coefficients were lowered during the scratch tests on the coated alumina indicating that this modification of the ion planting process should be useful for applying lubricating films of soft metals to electrical insulating materials. The very good throwing power of SCIP also strongly suggests general applicability of this process in other areas of technology, e.g., electronics, in addition to tribology.

Spalvins, Talivaldis↗
NASA NTRS1989

Gravity field determination and error assessment techniques

Linear estimation theory, along with a new technique to compute relative data weights, was applied to the determination of the Earth's geopotential field and other geophysical model parameters using a combination of satellite ground-based tracking data, satellite altimetry data, and the surface gravimetry data. The relative data weights for the inhomogeneous data sets are estimated simultaneously with the gravity field and other geophysical and orbit parameters in a least squares approach to produce the University of Texas gravity field models. New techniques to perform calibration of the formal covariance matrix for the geopotential solution were developed to obtain a reliable gravity field error estimate. Different techniques, which include orbit residual analysis, surface gravity anomaly residual analysis, subset gravity solution comparisons and consider covariance analysis, were applied to investigate the reliability of the calibration.

Yuan, D. N.↗
NASA NTRS1978

Scanning microscopy in microcircuit failure analysis

A three-phase microcircuit failure analysis procedure is presented. In the first phase, the device is nondestructively tested and the data obtained is correlated with the circumstances surrounding the failure event. The device is then subjected to a limited nondestructive analysis dominated by optical and scanning electron microscopy (SEM). Knowing that microcircuits usually fail from manufacturing defects or misuse, the analyst looks for one of the probable mechanisms. The SEM has two special operating modes that provide unique data for nondestructive analysis: voltage contrast and conductive current. These are used with other SEM modes and surface analysis techniques to analyze complicated microcircuits. The last phase includes the destructive procedures. The end product of these analyses is a corrective action that will yield a highly reliable system.

Nicolas, D. P.↗
NASA NTRS1986

Analysis/forecast experiments with a flow-dependent correlation function using FGGE data

The use of a flow-dependent correlation function to improve the accuracy of an optimum interpolation (OI) scheme is examined. The development of the correlation function for the OI analysis scheme used for numerical weather prediction is described. The scheme uses a multivariate surface analysis over the oceans to model the pressure-wind error cross-correlation and it has the ability to use an error correlation function that is flow- and geographically-dependent. A series of four-day data assimilation experiments, conducted from January 5-9, 1979, were used to investigate the effect of the different features of the OI scheme (error correlation) on forecast skill for the barotropic lows and highs. The skill of the OI was compared with that of a successive correlation method (SCM) of analysis. It is observed that the largest difference in the correlation statistics occurred in barotropic and baroclinic lows and highs. The comparison reveals that the OI forecasts were more accurate than the SCM forecasts.

Baker, W. E.↗
NASA NTRS1998

The Impact of NASA Scatterometer Data on GEOS-2 Analyses and Forecasts

Experiments with the evolving GEOS-2 data assimilation system (DAS) delineate the impact of NASA scatterometer (NSCAT) data on ocean surface analysis and numerical weather prediction (NWP). Extensions and refinements of the DAS to account for the characteristics of NSCAT data produced better results than were obtained with the GEOS-1 DAS. The two key extensions are to increase the vertical influence of the surface wind data and to take proper account of the time difference between the observation and the analysis. The results of these experiments show that surface wind analyses are improved by NSCAT data. This is seen in subjective evaluation of synoptic cases and in forecast impacts. NSCAT data have a very significant positive impact on the GEOS-2 forecasts in the southern hemisphere (SH). In the northern hemisphere (NH) the overall statistics show a modest positive impact. However, on a case by case basis, in the NH, the impact is generally neutral or significantly positive. The GEOS-2 results are compared to results obtained using the GEOS-1 DAS and using the 1995 National Center for Environmental Prediction (NCEP95) DAS. The GEOS-2 control forecasts are more accurate than those of GEOS-1. All three impact experiments show a large positive impact in the SH. In the NH, both the GEOS-2 and the NCEP95 NSCAT impacts are positive while the GEOS-1 impact is neutral.

Atlas, R.↗