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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 1,369 records · Page 76
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NASA NTRS1980

Multispectral imaging of the lunar regolith core samples - Preliminary results for 74002

Multispectral images of a lunar core segment are a new form of continuous data along the length of the core. A new laboratory arrangement was developed to obtain these images. Data processing and initial data analysis for core section 74002 were performed. The images are sensitive to variations in mineralogy and/or maturity of the soil and are easily used (1) in stratigraphic studies of the lunar regolith, (2) for sample selection of representative material, and (3) as ground truth for remote sensing studies.

Pieters, C. M.↗
NASA NTRS1982

Tests of general relativity using Starprobe radio metric tracking data

The potential of a proposed spacecraft mission, called Starprobe, for testing general relativity and providing information on the interior structure and dynamics of the sun is investigated. Parametric, gravitational perturbation terms are derived which represent relativistic effects and effects due to spatial and temporal variations in the solar potential at a given radial distance. A covariance analysis based on Kalman filtering theory predicts the accuracies with which the free parameters in the perturbation terms can be estimated with radio metric tracking data through the process of trajectory reconstruction. It is concluded that Starprobe can contribute significant information on both the nature of gravitation and the structure and dynamics of the solar interior.

Mease, K. D.↗
NASA NTRS1982

Total ozone-solar activity relationship

Approximately six years of global ozone monthly mean data from the Nimbus 4 BUV instrument are compared with monthly values of solar activity using 10.7-cm flux, F(10.7), as a parameter. Several techniques are explored in calculating the correlation between the two data sets, and all are found to yield relatively high correlations, ranging from R = 0.68 for 'raw' monthly means to 0.94 using a six-month running mean for each data set. It is shown, however, that the bulk of the correlation derives from the long-term decreasing trends in both data sets. When the long-term trends are removed, a cross-correlation analysis produces a maximum with no phase shift or with the ozone variations leading the solar variations by one month, thereby reducing the likelihood of a cause and effect relationship on time scales of this order. In view of the current uncertainty in the long-term stability of the BUV instrument and the resulting uncertainty in any long-term trend derived from its data, it is considered unrealistic to draw firm conclusions about a solar cycle influence on total ozone from this satellite data set.

Reber, C. A.↗
NASA NTRS1982

Japanese MAGSAT team

Construction of a model of the regional magnetic field and investigation of the local magnetic anomalies and their origin were approaches used in attempts to study the crustal structure near Japan and its Antarctic bases. Spatial properties of the regional magnetic field and comparison of the regional model with that derived from MAGSAT data are discussed. Possible causes of the magnetic anomalies, and results of aeromagnetic surveys incorporating gravity and seismic data are explored. Ionospheric and magnetospheric contributions to geomagnetic variations, field-aligned currents, magnetic geomagnetic pulsations, and hydromagnetic waves by analysis of MAGSAT data are also examined.

Fukushima, N.↗
NASA NTRS1983

Wall-temperature effects on the aerodynamics of a hydrogen-fueled transport concept in Mach 8 blowdown and shock tunnels

Results are presented from two separate tests on the same blended wing-body hydrogen fueled transport model at a Mach number of about 8 and a range of Reynolds numbers (based on theoretical body length) of 0.597 x 10 to the 6th power to about 156.22 x 10 to the 6th power. Tests were made in conventional hypersonic blowdown tunnel and a hypersonic shock tunnel at angles of attack of -2 deg to about 8 deg, with an extensive study made at a constant angle of attack of 3 deg. The model boundary-layer flow varied from laminar at the lower Reynolds numbers to predominantly turbulent at the higher Reynolds numbers. Model wall temperatures and stream static temperatures varied widely between the two tests, particularly at the lower Reynolds numbers. These temperature differences resulted in marked variations of the axial-force coefficients between the two tests, due in part to the effects of induced pressure and viscous interaction variations. The normal-force coefficient was essentially independent of Reynolds number. Analysis of results utilized current theoretical computer programs and basic boundary-layer theory.

Penland, J. A.↗
NASA NTRS1983

The relationship of total Birkeland currents to the merging electric field

Magsat data were used to examine the behavior of Birkeland currents during 1100-2000 UT in consecutive orbits passing near the dawn-dusk meridian. The field was measured with a three-axis fluxgate instrument with a resolution of within 0.5 nT, with the sampling occurring every 1/16th sec. A total of 32 crossings of the Northern Hemisphere auroral zone were available for analysis. The changes in the magnetic readings were correlated more closely with variation in the IMF parameters than to the latitudinal width of the changes. Evidence was found for a relationship between the reconnection electric field and the intensity of the large-scale Birkeland current system. The total conductance of the auroral zone was calculated to be about 18.7 mhos.

Bythrow, P. F.↗
NASA NTRS1982

Empirical testing of structural deflection modeling of large photovoltaic modules

The objective of the structural deflection test was to verify the analytical models used to predict solar cell stress, load-bearing layer stress, and module deflection that result from a uniform pressure load on the module surface. The verification process consisted of measuring module deflection, stress in the solar cell, and stress in the load-bearing member as a functon of normal pressure load, pottant modulus of elasticity, pottant thickness, and cell location. Four glass superstrate modules, two plain wood substrate modules, two ribbed wood substrate modules, and a steel substrate module were tested. Consistent with analysis predictions, all unribbed specimens exhibited nonlinear load vs. deflection characteristics. With the exception of the steel module, test results and analysis predictions for panel deflectons agreed to within 10 percent. A wider variation of agreement was found for stress in the load-bearing members and cells.

Duncan, L. B.↗
NASA NTRS1985

LSS 2018: A double-lined spectroscopic binary central star with an extremely large reflection effect

LSS 2018, the central star of the planetry nebulae DS1, was found to be a double-lined spectroscopic binary with a period of 8.571 hours. Light variations with the same period were observed in U, B, and V; in the wavelength regions defined by the two IUE cameras; and in the strength of the CIII 4647 emission line. The light variations can be accurately predicted by a simple reflection effect, and an analysis of the light curves yields the angular diameter and effective temperature of the primary, the radii of the two stars in terms of their separation, and the inclination of the system. Analysis of the radial velocities then yields the masses of the two stars, their separation, the distance of the system, the absolute magnitude of the primary, and the size of the nebula.

Drilling, J. S.↗
NASA NTRS1985

Quantitative determination of mineral types and abundances from reflectance spectra using principal components analysis

A procedure was developed for analyzing remote reflectance spectra, including multispectral images, that quantifies parameters such as types of mineral mixtures, the abundances of mixed minerals, and particle sizes. Principal components analysis reduced the spectral dimensionality and allowed testing the uniqueness and validity of spectral mixing models. By analyzing variations in the overall spectral reflectance curves, the type of spectral mixture was identified, mineral abundances quantified and the effects of particle size identified. The results demonstrate an advantage in classification accuracy over classical forms of analysis that ignore effects of particle-size or mineral-mixture systematics on spectra. The approach is applicable to remote sensing data of planetary surfaces for quantitative determinations of mineral abundances.

Smith, M. O.↗
NASA NTRS1985

LSS 2018 - A double-lined spectroscopic binary central star with an extremely large reflection effect

LSS 2018, the central star of the planetary nebulae DS1, was found to be a double-lined spectroscopic binary with a period of 8.571 hours. Light variations with the same period were observed in U, B, and V; in the wavelength regions defined by the two IUE cameras; and in the strength of the CIII 4647 emission line. The light variations can be accurately predicted by a simple reflection effect, and an analysis of the light curves yields the angular diameter and effective temperature of the primary, the radii of the two stars in terms of their separation, and the inclination of the system. Analysis of the radial velocities then yields the masses of the two stars, their separation, the distance of the system, the absolute magnitude of the primary, and the size of the nebula.

Drilling, J. S.↗
NASA NTRS1985

Tropospheric ozone - Seasonal behavior, trends, and anthropogenic influence

In the present analysis of tropospheric ozone data, attention is given to spatial and temporal variations. Two modes of seasonal behavior are noted for surface ozone at mid-latitudes: a broad summer maximum within a few hundred km of industrial/urban areas in Europe and the U.S., and a minimum in summer or autumn in sparcely populated regions that are remote from industrial activity. These and limited historical data indicate that summertime concentrations of ozone near the surface in the rural areas of Europe and the U.S. may have increased between 20 and 100 percent since the 1940s. It is suggested that the summer maximum in ozone and other observed trends are due to photochemical production associated with anthropogenic emissions of NO(x), hydrocarbons, and CO from fossil fuel combustion.

Logan, J. A.↗
NASA NTRS1986

Fault latency in the memory - An experimental study on VAX 11/780

Fault latency is the time between the physical occurrence of a fault and its corruption of data, causing an error. The measure of this time is difficult to obtain because the time of occurrence of a fault and the exact moment of generation of an error are not known. This paper describes an experiment to accurately study the fault latency in the memory subsystem. The experiment employs real memory data from a VAX 11/780 at the University of Illinois. Fault latency distributions are generated for s-a-0 and s-a-1 permanent fault models. Results show that the mean fault latency of a s-a-0 fault is nearly 5 times that of the s-a-1 fault. Large variations in fault latency are found for different regions in memory. An analysis of a variance model to quantify the relative influence of various workload measures on the evaluated latency is also given.

Chillarege, Ram↗
NASA NTRS1987

Stratospheric O3, H2O, and HDO distributions from balloon-based far-infrared observations

Limb thermal emission spectra of the earth's stratosphere in the FIR obtained as part of the Balloon Intercomparison Campaign (BIC), have been analyzed for retrieval of trace constituent distributions. The observations analyzed here were made with a balloon-borne high-resolution Michelson interferometer operating in the 20-100/cm region, with an unapodized spectral resolution of 0.0033/cm. In this paper the vertical profiles of O3, H2O, and HDO retrieved from the observed spectra are presented and compared with the results from other BIC experiments. The retrieved profiles are found to be in good agreement with other measurements. The measurement of the HDO profile provides information about the sources of stratospheric water vapor. The variation of the D/H ratio of water vapor is derived from an analysis of HDO and H2O lines observed in the FIR spectra and is compared with the available measurements in the literature.

Abbas, M. M.↗
NASA NTRS1988

Aeroassist vehicle requirements for a Mars Rover/Sample Return Mission

A three degree-of-freedom computer simulation has been developed to perform Martian aeroassist trajectories using the HYPAS guidance algorithm. This simulator was used to perform a parametric study at the Johnson Space Center of various low L/D vehicles and their performance with the inclusion of vehicle and atmospheric dispersions. The ultimate goal is to define an extreme (minimum L/D) aeroassist configuration for the Mars Rover/Sample Return Mission to compare with the previously defined biconic aeroshell. The study shows that a raked cone vehicle with L/D betweeen 0.3 and 0.6 will perform adequately in the Martian environment in the presence of dispersions. Average apoapsis error for the 0.6 L/D vehicle was 11.9 km (6.4 nm) above the 2000 km target which compares fairly well with an error of 3.5 km (1.9 nm) for the 1.5 L/D biconic vehicle. The study concluded that the low L/D raked configuration warrants further study which could include stability analysis as well as the inclusion of density shears and dynamic atmospheric variations.

Meyerson, Robert E.↗
NASA NTRS1989

The development of power specific redlines for SSME safety monitoring

Over the past several years, there has been an increased awareness in the necessity for rocket engine health monitoring because of the cost and complexity of present and future systems. A current rocket engine system, the Space Shuttle Main Engine (SSME), combines a limited redline system with closed-loop control of the engine's thrust level and mixture ratio. Despite these features, 27 tests of the SSME have resulted in major incidents. A SSME transient model was used to examine the effect of variations in high pressure turbopump performance on various engine parameters. Based on analysis of the responses, several new parameters are proposed for further investigation as power-level specific redlines.

Maul, William A.↗
NASA NTRS1989

The development of power specific redlines for SSME safety monitoring

Over the past several years, there has been an increased awareness in the necessity for rocket engine health monitoring because of the cost and complexity of present and future systems. A current rocket engine system, the Space Shuttle Main Engine (SSME), combines a limited redline system with closed-loop control of the engine's thrust level and mixture ratio. Despite these features, 27 tests of the SSME have resulted in major incidents. An SSME transient model was used to examine the effect of variations in high pressure turbopump performance on various engine parameters. Based on analysis of the responses, several new parameters are proposed for further investigation as power-level specific redlines.

Maul, William A.↗
NASA NTRS1990

Spacecraft attitude impacts on COLD-SAT non-vacuum jacketed LH2 supply tank thermal performance

The Cryogenic On-Orbit Liquid Depot - Storage, Acquisition and Transfer (COLD-SAT) spacecraft will be launched into low earth orbit to perform fluid management experiments on the behavior of subcritical liquid hydrogen (LH2). For determining the optimum on-orbit attitude for the COLD-SAT satellite, a comparative analytical study was performed to determine the thermal impacts of spacecraft attitude on the performance of the COLD-SAT non-vacuum jacketed LH2 supply tank. Tank thermal performance was quantified by total conductive and radiative heat leakage into the pressure vessel due to the absorbed solar, earth albedo and infra-red on-orbit fluxes, and also by the uniformity of the variation of this leakage on the vessel surface area. Geometric and thermal analysis math models were developed for the spacecraft and the tank as part of this analysis, based on their individual thermal/structural designs. Two quasi-inertial spacecraft attitudes were investigated and their effects on the tank performance compared. The results are one of the criteria by which the spacecraft orientation in orbit was selected for the in-house NASA Lewis Research Center design.

Arif, Hugh↗
NASA NTRS1990

A probabilistic approach to the dynamic analysis of ducts subjected to multibase harmonic and random excitation

The dynamic behavior of the discharge duct of the high-pressure oxidizer turbopump of a cryogenic rocket motor is investigated analytically. The probabilistic analysis program NESSUS (Numerical Evaluation of Stochastic Structures Under Stress; Cruse et al., 1988) is used to treat the uncertainties due to random and harmonic excitation (e.g., pump noise, pump-induced harmonics, and combustion noise), variations in engine inlet pressure, and changes in system damping. The load modeling procedure, the variation in power-spectral density in different zones of the engine structure, and the dynamic structural-analysis technique are described, and the numerical results of the NESSUS analysis are presented in extensive tables and graphs and discussed in detail.

Debchaudhury, Amit↗