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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 1,675 records · Page 93
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Giant solar flares in Antarctic ice

A new hypothesis proposes an explanation for the presence of four prominent spikes in a long time record of the NO3(-) concentration inside the Antarctic ice. This solar flare hypothesis suggests that the ionizing radiation necessary in the spike formation could have come from extremely powerful solar flares. It is proposed that these flares would have occurred during the times of the largest maxima in the solar cycle. The solar flare hypothesis is compared with the supernova hypothesis.

Stothers, R.↗
NASA NTRS1973

Mariner 9 ultraviolet spectrometer experiment - Mars atomic oxygen 1304-A emission.

Selected results are presented for an analysis of Mariner 9 1304-A data from the first 100 passes. Based on a comparison of limb data, the exospheric temperature appears lower on several Mariner 9 passes than when Mariner 6 and 7 encountered the planet in 1969. Temperatures of 300 and 350 K are considered in the atmospheric modeling. At 300 K, derived values of the atomic oxygen concentration are typically between 0.5 and 1% of the total density at 135 km, based on fitting theoretical intensities to limb data from several passes. Structure in the limb data below 200 km suggests the possibility that approximately 0.2 kR of the observed approximately 0.8 kR near 150 km is due to dissociative excitation of CO2. There is variability in limb profiles, thus indicating changes in the O distribution with time. The variability does not appear to follow a recognizable pattern. Interpretation of the 1304-A disk data shows a correlation in intensity with the 10.7-cm solar flux and larger O concentrations in the afternoon than in the morning. The correlation in intensity with the 10.7-cm flux is probably due largely to variation in the solar 1304-A fluxes.

Strickland, D. J.↗
NASA NTRS1977

Mariner 9 Ultraviolet Spectrometer Experiment: Mars Atomic Oxygen 1304-A Emission

Selected results are presented for an analysis of Mariner 9 1304-A data from the first 100 passes. Based on a comparison of limb data, the exospheric temperature appears lower on several Mariner 9 passes than when Mariner 6 and 7 encountered the planet in 1969. Temperatures of 300 and 350 K are considered in the atmospheric modeling. At 300 K, derived values of the atomic oxygen concentration are typically between 0.5 and 1 percent of the total density at 135 km, based on fitting theoretical intensities to limb data from several passes. Structure in the limb data below 200 km suggests the possibility that approximately 0.2 kR of the observed approximately 0.8 kR near 150 km is due to dissociative excitation of CO2. There is variability in limb profiles indicating changes in the O distribution with time. The variability does not appear to follow a recognizable pattern. Interpretation of the 1304-A disc data shows a correlation in intensity with the 10.7 cm solar flux and larger O concentrations in the afternoon than in the morning. The correlation in intensity with the 10.7 cm flux is probably due largely to variation in the solar 1304-A fluxes. Selected disc data show localized and random enhancements in the intensity.

Strickland, D. J.↗
NASA NTRS1990

Soft X-ray spectroscopy of solar flares - An overview

An overview of the current status of high spectral resolution soft X-ray observations of solar flares is given. The review concentrates primarily on recent results and interpretations of results obtained from orbiting Bragg crystal spectrometers flow during the last solar maximum on the US DoD P78-1 spacecraft, the NASA SMM, and the ISAS Hinotori spacecraft. Results and several key issues regarding interpretation of the spectra are presented. Specifically, the dynamics of coronal flare plasmas as revealed by X-ray line profiles and wavelength shifts are discussed. Recent results concerning the theory of chromospheric evaporation are given. The temperature of coronal flare plasma is discussed within the context of a differential mission measure. Results concerning electron density measurements, nonequilibrium processes, and relative element abundances are also reviewed.

Doschek, G. A.↗
NASA NTRS1986

Monte Carlo models for the terrestrial exosphere over a solar cycle

Improved Monte Carlo exosphere simulations for the concentration and velocity distribution of hydrogen in the terrestrial exosphere were formulated for minimum, medium, and maximum solar cycle conditions. Both the classical exobase source of hot hydrogen and the plasmaspheric source were included, along with solar radiation pressure and photoionization. It was found that at solar minimum the hydrogen from the charge exchange of hot ions in the plasmasphere exceeds that from the exobase source not only for escape but for the population at geocentric distances greater than 2 earth radii. At about two earth radii, the equivalent temperature is about 50 percent greater than that of the exobase, a situation similar to that of the 'two-temperature' Venusian exosphere. Diurnal variations were calculated for altitudes of up to 30 earth radii; for all levels of solar activity, the inclusion of radiation pressure led to a semidiurnal variation at 3-8 earth radii and a high-altitude night/day asymmetry constituting the 'geotail'.

Tinsley, B. A.↗
NASA NTRS1980

Dish Stirling solar receiver program

A technology demonstration of a Dish Stirling solar thermal electric system can be accomplished earlier and at a much lower cost than previous planning had indicated by employing technical solutions that allow already existing hardware, with minimum modifications, to be integrated into a total system with a minimum of development. The DSSR operates with a modified United Stirling p-40 engine/alternator and the JPL Test Bed Concentrator as a completely integrated solar thermal electric system having a design output of 25 kWe. The system is augmented by fossil fuel combustion which ensures a continuous electrical output under all environmental conditions. Technical and economic studies by government and industry in the United States and abroad identify the Dish Stirling solar electric system as the most appropriate, efficient and economical method for conversion of solar energy to electricity in applications when the electrical demand is 10 MWe and less.

Haglund, R. A.↗
NASA NTRS1981

The response of ozone to solar activity variations - A review

The effects of solar UV variations on the ozone concentration in the atmosphere are studied with respect to determinations of the global mean ozone concentrations as measured by satellite instrumentation. The Nimbus 4 satellite revealed an NO presence, which catalytically destroys ozone, during a solar proton event. An 11-year UV variability has been detected at increasing wavelengths above 1500 A, an energy band which causes photolysis of O2 into O3, N2O into NO, and NO production in the stratosphere. The latter two reactions decrease ozone destruction. IR interferometer spectrometer (IRIS) data is cited to show an ozone variation of about 3%, which is possible with a 20% solar UV variability at 1800 A; the variability has been confirmed to exist by measurements taken from the Atmospheric Explorer E satellite.

Keating, G. M.↗
NASA NTRS1981

Satellite observed ozone variations and solar activity

The degree of association between total and stratospheric ozone and solar ultraviolet irradiance is evaluated based on mean monthly latitudinally averaged ozone observations from the Nimbus-4 BUV data set. The mean monthly 10.7 cm solar flux f(10.7), adjusted for varying earth-sun distance, is used as a convenient index of solar UV variation. Results show no obvious relationship between total ozone and solar ultraviolet irradiance based on analysis of satellite data over a period of seven years, even though such a relationship has been suggested from theoretical considerations. However, the analysis does indicate that there may be a positive response in the upper tropical stratosphere, at a height of about 45-50 km such that there is an increase in the ozone concentration following an increase in solar UV radiation, which is assumed to be indicated by an increase in f(10.7) flux

London, J.↗
NASA NTRS1992

Advances in photovoltaic technology

The advances in solar cell efficiency, radiation tolerance, and cost in the last 10 years are presented. The potential performance of thin-film solar cells in space is examined, and the cost and the historical trends in production capability of the photovoltaics industry are considered with respect to the needs of satellite solar power systems. Attention is given to single-crystal cells, concentrator and cascade cells, and thin-film solar cells.

Landis, G. A.↗
DOE OSTI2024

Design, performance, and field operation of twisting heliostats for 3,000-sun concentration and high temperature

The idea is to combine the solar energy reflected from a field of many heliostats to obtain a single focus of high concentration and high power. We exploit a new type of “twisting” heliostat” in which as the mount is moved to track the sun through the day, the reflector shape is twisted to maintain a focused image of the sun’s disc on the target, through the day over a wide range of angles of incidence. By combining the light reflected by many twisting heliostats into a single focus, we are not only able to accomplish but also maintain very high concentration and temperature through the day, with higher efficiency than has previously been possible with conventional heliostats having a fixed shape. A circular field of twisting heliostats is used to power a single intense focus atop a central tower. The light from all the heliostats is relayed to an upward facing receiver at the focus via a central Cassegrain secondary reflector located above the receiver. In a specific design targeting 1 MW of power, a 100 m diameter field arrays 431 twisting heliostats, each with a 7 m2 reflector. The secondary reflector ,7.2 m in diameter, is located 24 m above the heliostat field, bringing sunlight with annual average power of 1 MW to a circular focus 0.8 m in diameter, at a concentration averaging 3,000 suns.

14 SOLAR ENERGY↗
NASA NTRS1992

He(2+) in field-aligned beams - ISEE results

He(2+) concentrations are determined for 14 field-aligned proton-beam events observed in the ion-foreshock region upstream from the earth's bow shock by the ISEE spacecraft. For all 14 events, most under normal solar-wind conditions, the He(2+) concentrations were a factor of 10 or more below the H(+) concentrations in the field-aligned beams when normalized by the solar wind He(2+) to H(+) density ratio. These results indicate that field-aligned beams do not provide the principal He(2+) seed population for ion acceleration in the ion-foreshock region.

Fuselier, Stephen A.↗
DOE OSTI2020

Pumped Thermal Energy Storage: Thermodynamics and Economics

This presentation gives an overview of Pumped Thermal Energy Storage (PTES), and in particular concentrates on the performance and cost of a Joule-Brayton cycle with liquid storage. Results for systems with supercritical CO2 are also presented. PTES may be hybridized with solar heat, and some examples are provided as well as an overview of potential issues.

41 EE - Solar Energy Technologies Office (EE-4S)↗
NASA NTRS1980

Study of multi-kW solar arrays for Earth orbit application

Low cost low Earth orbit (LOW) and geosynchronous Earth orbit (GEO) Solar Array concepts in the 300 to 1000 kW range which could be reduced to hardware in the mid 1980's, are identified. Size scaling factors and longer life demands are recognized as the prime drivers for the designs if low life cycle costs for energy are to be achieved. Technology is identified which requires further development in order to assure component readiness and availability. Use of the low concentration ratio (CR) concentrator, which uses gallium arsenide solar cells for both LEO and GEO applications, is recommended.

Source record↗
NASA NTRS1976

Solar astrophysics - Ghettosis from, or symbiosis with, stellar and galactic astrophysics

The purpose of the paper is to show how the solar-stellar symbiotic approach has led to the modeling of a star as a concentration of matter and energy. By 'solar-stellar symbiosis' is meant the philosophy of investigation according to which one asks what change in our general understanding of stellar structure and of stellar spectroscopic diagnostics is required to satisfy both the sun and an unusual star when, for example, some feature of an unusual star is discovered. The evolution of stellar models is traced, from walled, thermodynamic-equilibrium models to de-isolated models featuring transition zones and nonlocal thermodynamic equilibrium.

Pecker, J.-C.↗
NASA NTRS1978

Ion Propulsion Module design and mission performance

This paper describes the design options, processes and tradeoffs that occur during the establishment of viable Ion Drive vehicle and mission designs. The options identify those internal vehicle design alternatives which are being considered for future Ion Drive missions, such as sunlight concentrating arrays and direct drive thrust subsystems, and their effect on mission performance. Also, the highly interactive nature of the Ion Drive design process, which occurs between the spacecraft and mission designers, is described. The results of design tradeoffs, performed for three Ion Drive comet rendezvous missions, are presented. These results include the following: (1) the power profile is determined primarily by the trajectory while second order effects include the solar cell characteristics and array concentration factor and degradation; and (2) the dominant parameter in mission performance determination, Ion Propulsion Module (IPM) mass, and IPM design, is the total cell power evaluated without concentration, at the beginning of life and at 1 AU.

Graf, J. E.↗
NASA NTRS1984

High-Temperature Helical-Tube Solar Receiver

Solar-thermal receiver used with circular parabolic concentrator to supply about 58 kW thermal power to Brayton engine or industrial process. Solar radiation focused into open end of cylindrical ceramic thermal inertial sleeve 8 in. in diameter that reradiates energy to helical heatexchanger tube surrounding sleeve.

Robertson, C. S., Jr.↗
NASA NTRS1995

Analysis of shadowing effects on MIR photovoltaic and solar dynamic power systems

The NASA Lewis Research Center is currently working with RSC-Energia, the Russian Space Agency, and Allied Signal in developing a flight demonstration solar dynamic power system. This type of power system is dependent upon solar flux that is reflected and concentrated into a thermal storage system to provide the thermal energy input to a closed-cycle Brayton heat engine. The solar dynamic unit will be flown on the Russian Mir space station in anticipation of use on the International Space Station Alpha. By the time the power system is launched, the Mir will be a spatially complex configuration which will have, in addition to the three-gimbaled solar dynamic unit, eleven solar array wings that are either fixed or track the Sun along one axis and a variety or repositionable habitation and experiment modules. The proximity of arrays to modules creates a situation which makes it highly probable that there will be varying solar flux due to shadowing on the solar dynamic unit and some of the arrays throughout the orbit. Shadowing causes fluctuations in the power output from the arrays and the solar dynamic power system, thus reducing the energy capabilities of the spacecraft. An assessment of the capabilities of the power system under these conditions is an important part in influencing the design and operations of the spacecraft and predicting its energy performance. This paper describes the results obtained from using the Orbiting Spacecraft Shadowing Analysis Station program that was integrated into the Station Power Analysis for Capability Evaluation (SPACE) electrical power system computer program. OSSA allows one to consider the numerous complex factors for analyzing the shadowing effects on the electrical power system including the variety of spacecraft hardware geometric configurations, yearly and daily orbital variations in the vehicle attitude and orbital maneuvers (for communications coverage, payload pointing requirements and rendezvous/docking with other vehicles). The geometric models of the MIR with a solar dynamic power unit that were used in performing shadowing analyses are described. Also presented in this paper are results for individual orbits for several flight attitude cases which include assessments of the shadowing impacts upon the solar dynamic unit and the solar arrays. These cases depict typical MIR flight attitudes likely to have shadowing impact. Because of the time varying nature of the Mir orientation with respect to the Sun and the lack of knowledge of the precise timing of the attitude changes, strategies must be devised to assess and depict the shadowing impacts on power generation throughout the year. To address this, the best, nominal and worst impacts of shadowing considering a wide possible range of parameter changes for typical mission operation period are shown.

Fincannon, James↗