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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS2015

Towing Asteroids with Gravity Tractors Enhanced by Tethers and Solar Sails

Material collected from an asteroid's surface can be used to increase gravitational attraction between the asteroid and a Gravity Tractor (GT); the spacecraft therefore operates more effectively and is referred to as an Enhanced Gravity Tractor (EGT). The use of tethers and solar sails to further improve effectiveness and simplify operations is investigated. By employing a tether, the asteroidal material can be placed close to the asteroid while the spacecraft is stationed farther away, resulting in a better safety margin and improved thruster efficiency. A solar sail on a spacecraft can naturally provide radial offset and inter-spacecraft separation required for multiple EGTs.

Shen, Haijun↗
NASA NTRS1979

Grain carriers of isotopic anomalies

The dynamics of grain motion through gas are examined in terms of the injection of isotopically anomalous (compared to solar abundances) material into the early solar nebula. Calculations indicate that the injected grains cannot penetrate to the center of any of a range of reasonable configurations, suggesting the formation of an edge region enriched in injected material. Furthermore, the dynamical behavior of grains in turbulent flows indicates that pockets of grains can have some resistance to turbulent diffusion. The constraints developed here are used to delineate a set of consistent, injected-grain models for the origin of the isotopic anomalies in meteorite inclusions.

Margolis, S. H.↗
NASA NTRS1975

Studies of encapsulant materials for terrestrial solar-cell arrays

Study 1 of this contract is entitled ""Evaluation of World Experience and Properties of Materials for Encapsulation of Terrestrial Solar-Cell Arrays.'' The approach of this study is to review and analyze world experience and to compile data on properties of encapsulants for photovoltaic cells and for related applications. The objective of the effort is to recommend candidate materials and processes for encapsulating terrestrial photovoltaic arrays at low cost for a service life greater than 20 years. The objectives of Study 2, ""Definition of Encapsulant Service Environments and Test Conditions,'' are to develop the climatic/environmental data required to define the frequency and duration of detrimental environmental conditions in a 20-year array lifetime and to develop a corresponding test schedule for encapsulant systems.

Carmichael, D. C.↗
NASA NTRS1979

Development and evaluation of die and container materials. Low cost silicon solar array project

Specific compositions of high purity silicon aluminum oxynitride (Sialon) and silicon beryllium oxynitride (Sibeon) solid solutions were shown to be promising refractory materials for handling and manipulating solar grade silicon into silicon ribbon. Evaulation of the interaction of these materials in contact with molten silicon indicated that solid solutions based upon beta-Si3N4 were more stable than those based on Si2N2O. Sibeon was more resistant to molten silicon attack than Sialon. Both materials should preferably be used in an inert atmosphere rather than under vacuum conditions because removal of oxygen from the silicon melt occurs as SiO enhances the dissolution of aluminum and beryllium. The wetting angles of these materials were low enough for these materials to be considered as both die and container materials.

Wills, R. R.↗
NASA NTRS1988

Interplanetary dust particles

The ways of establishing the extraterrestrial nature of different subsets of interplanetary dust collected in the stratosphere by high-altitude aircraft are discussed. Consideration is given to microanalytic techniques which make it possible to obtain detailed experimental information on the mineralogical and petrographic characteristics, the mid-IR absorption spectra, the Raman spectra, and the isotopic properties of individual particles. The implications of data obtained by these techniques for the origin of interplanetary dust are examined, showing that the particles are less altered than those solar-system material samples found in meteorites. It is suggested that many of the particles come from comets, although an unknown fraction originate from asteroids. Small regions of isotopically distinct material suggest that part of the dust consists of interstellar-cloud material that predates the solar system.

Bradley, John P.↗
NASA NTRS1979

Performance prediction evaluation of ceramic materials in point-focusing solar receivers

A performance prediction was adapted to evaluate the use of ceramic materials in solar receivers for point focusing distributed applications. System requirements were determined including the receiver operating environment and system operating parameters for various engine types. Preliminary receiver designs were evolved from these system requirements. Specific receiver designs were then evaluated to determine material functional requirements.

Ewing, J.↗
NASA NTRS1977

Space-based solar power conversion and delivery systems study. Volume 4: Energy conversion systems studies

Solar cells and optical configurations for the SSPS were examined. In this task, three specific solar cell materials were examined: single crystal silicon, single crystal gallium arsenide, and polycrystalline cadmium sulfide. The comparison of the three different cells on the basis of a subsystem parametric cost per kW of SSPS-generated power at the terrestrial utility interface showed that gallium arsenide was the most promising solar cell material at high concentration ratios. The most promising solar cell material with no concentration, was dependent upon the particular combination of parameters representing cost, mass and performance that were chosen to represent each cell in this deterministic comparative analysis. The potential for mass production, based on the projections of the present state-of-the-art would tend to favor cadmium sulfide in lieu of single crystal silicon or gallium arsenide solar cells.

Source record↗
NASA NTRS1986

Economics of polysilicon processes

Techniques are being developed to provide lower cost polysilicon material for solar cells. Existing technology which normally provides semiconductor industry polysilicon material is undergoing changes and also being used to provide polysilicon material for solar cells. Economics of new and existing technologies are presented for producing polysilicon. The economics are primarily based on the preliminary process design of a plant producing 1,000 metric tons/year of silicon. The polysilicon processes include: Siemen's process (hydrogen reduction of trichlorosilane); Union Carbide process (silane decomposition); and Hemlock Semiconductor process (hydrogen reduction of dichlorosilane). The economics include cost estimates of capital investment and product cost to produce polysilicon via the technology. Sensitivity analysis results are also presented to disclose the effect of major paramentes such as utilities, labor, raw materials and capital investment.

Yaws, C. L.↗
NASA NTRS1997

Optical Waveguide Solar Energy System for Lunar Materials Processing

This paper discusses results of our work on development of the Optical Waveguide (OW) Solar Energy System for Lunar Materials Processing. In the OW system as shown, solar radiation is collected by the concentrator which transfers the concentrated solar radiation to the OW transmission line consisting of low-loss optical fibers. The OW line transmits the solar radiation to the thermal reactor of the lunar materials processing plant. The feature of the OW system are: (1) Highly concentrated solar radiation (up to 104 suns) can be transmitted via flexible OW lines directly into the thermal reactor for materials processing: (2) Solar radiation intensity or spectra can be tailored to specific materials processing steps; (3) Provide solar energy to locations or inside of enclosures that would not otherwise have an access to solar energy; and (4) The system can be modularized and can be easily transported to and deployed at the lunar base.

Nakamura, T.↗
NASA NTRS1972

Stress Analysis and Design of Silicon Solar Cell Arrays and Related Material Properties

A systematic approach is presented for the design of solar cell arrays to eliminate mechanical failures that might arise in components of the arrays in a thermal environment. A prerequisite to the approach is the characterization of material properties at different temperatures. Significant data is obtained for the thermal behavior of the silicon solar cell material and adhesives. Upon determining the mechanical and thermal material properties of the components of the solar cell array, utilizing a finite element idealization for predicting the stress fields in the components, and employing the von Mises failure criterion, potential failure areas in various design configurations in a given thermal environment are identified. Guide lines and means to optimize a given design are illustrated by two examples.

Salama, A. M.↗
NASA NTRS2021

The Formation of Carbonaceous Material in the Early Solar Nebula: The Role of Metal Dusting

For many years it has been suggested that the carbonaceous material found in association with Fe/Ni metal and metal carbides in primitive bodies is linked to the Fischer–Tropsch reaction. This is especially true with chondritic-porous interplanetary dust particles, which are considered to have a cometary origin and are among some of the most primitive and least processed materials available for study. Another phenomenon which occurs under the same carburizing conditions as the Fischer–Tropsch reaction is called metal dusting and could be a possible pathway to forming some of the carbonaceous material found in primitive bodies. Metal dusting is a catastrophic corrosion of metal under these carburizing conditions that results in a porous mixture of carbonaceous material, metal, and metal carbides. In the case of pure iron, type I metal dusting results in the formation of a metastable iron carbide, typically cementite, Fe3C. While metal dusting has been studied industrially for over 50 years, it does not appear to have been applied to the formation of carbonaceous material in astrophysical settings. In this work, the general mechanism of metal dusting on iron is described and a thermodynamic analysis of the dusting phenomena applied to solar nebula conditions. Rate measurements are made with pure iron samples over the temperature range from 400°C to 950°C. In addition, the products from experimental runs at 500°C and 600°C are studied by transmission electron microscopy. Results show that iron carbide particles are formed with carbonaceous material consisting of poorly graphitized carbon.

Interplanetary dust↗
NASA NTRS1973

Thermoelastic analysis of solar cell arrays and their material properties

A thermoelastic stress analysis procedure is reported for predicting the thermally induced stresses and failures in silicon solar cell arrays. A prerequisite for the analysis is the characterization of the temperature-dependent thermal and mechanical properties of the solar cell materials. Extensive material property testing was carried out in the temperature range -200 to +200 C for the filter glass, P- and N-type silicon, interconnector metals, solder, and several candidate silicone rubber adhesives. The analysis procedure is applied to several solar cell array design configurations. Results of the analysis indicate the optimum design configuration, with respect to compatible materials, effect of the solder coating, and effect of the interconnector geometry. Good agreement was found between results of the analysis and the test program.

Salama, M. A.↗
NASA NTRS1981

Evaluation of silicon-on-ceramic material for low-cost solar cells

The silicon-on-ceramic (SOC) process produces thin layers of silicon on inexpensive ceramic substrates. The layers are produced by unidirectional solidification of molten silicon, and are polycrystalline. Solar cells made from SOC material have performed with a conversion efficiency of 10.5%. In connection with the objective to improve the efficiency of SOC solar cells, an investigation was conducted to assess the relative importance of grain boundaries and impurities. In order to separate the two effects, light-beam-induced current (LBIC) measurements of the short-circuit current were made using a micron-sized light beam from a monochromator. The LBIC measurements are closely related to solar cell performance since the technique identifies the various spatial and spectral contributions to solar cell current. On the basis of the obtained results, it appears that structural defects are more important than chemical defects in limiting the performance of present SOC solar cells.

Zook, J. D.↗
NASA NTRS1974

Thermoelastic analysis of solar cell arrays and their material properties

Description of a thermoelastic stress analysis procedure for predicting the thermally induced stresses and failures in silicon solar cell arrays. A prerequisite for the analysis is the characterization of the temperature-dependent thermal and mechanical properties of the solar cell materials. Extensive material property testing was carried out in the temperature range from -200 to +200 C for the filter glass, P- and N-type silicon, interconnector metals, solder, and several candidate silicone rubber adhesives. The analysis procedure is applied to several solar cell array design configurations, which were tested in the Space Molecular Sink. Results of the analysis indicate the optimum design configuration with respect to materials and geometry, effect of the solder coating, and effect of the interconnector geometry.

Salama, M. A.↗
NASA NTRS1980

High resolution measurements of galactic cosmic-ray neon, magnesium, and silicon isotopes

High-resolution measurements of the abundances of individual isotopes of neon, magnesium and silicon in galactic cosmic rays are reported. The Caltech Heavy Isotope Spectrometer Telescope on board the ISEE 3 spacecraft was used to obtain measurements in the range 30 to 180 MeV/n at an rms mass resolution of 0.20 amu. Results indicate excesses of Ne-22 as well as Mg-25 and Mg-26 in galactic cosmic rays with respect to their solar system abundances. Calculations of the effects of interstellar propagation and solar modulation on cosmic-ray isotope abundances also imply an Mg-25 + Mg-26 cosmic ray source fraction significantly greater than the solar system fraction, and it is suggested that the cosmic ray source material and solar system material were synthesized under different conditions.

Mewaldt, R. A.↗
NASA NTRS2008

Using Global Simulations to Relate the Three-Part Structure of Coronal Mass Ejections to in Situ Signatures

White-light observations of coronal mass ejections (CMEs) often show the classic "three-part" structure consisting of (1) a bright front; (2) a dark cavity; and (3) a bright, compact core. It has proven difficult to unambiguously associate these features with in situ measurements of interplanetary CMEs (ICMEs), in all but a few cases. In this study we use a global MHD model to simulate the eruption and evolution of a CME out to 0.25 AU, allowing us to continuously track these features from the Sun and through the solar wind. Our results support the generally held view that the interplanetary flux rope corresponds to the dark cavity. We find that the bright front merges with solar wind material swept up by the ICME. Thus, the sheath material found ahead of fast ejecta is in fact composed from both ambient solar wind material, as well the bright front. We also note that, in this simulation, the bright front is formed from the overlying streamer configuration from within which the CME erupted and is not itself coronal material swept up during the early phase of the eruption. The conclusions reached in this study are undoubtedly sensitive to the initial configuration and mechanism used to initiate the CME, and thus care should be taken when using them to interpret specific observations. On the other hand, they provide a unique, unbroken connection between remote solar and interplanetary observations. Ultimately, detailed comparisons between observations and simulation results may be able to constrain or even rule out some mechanisms of CME initiation.

Riley, Pete↗
NASA NTRS2008

Using Global Simulations to Relate the Three-Part Structure of Coronal Mass Ejections to In Situ Signatures

White-light observations of coronal mass ejections (CMEs) often show the classic "three-part" structure consisting of (1) a bright front; (2) a dark cavity; and (3) a bright, compact core. It has proven difficult to unambiguously associate these features with in situ measurements of interplanetary CMEs (ICMEs), in all but a few cases. In this study we use a global MHD model to simulate the eruption and evolution of a CME out to 0.25 AU, allowing us to continuously track these features from the Sun and through the solar wind. Our results support the generally held view that the interplanetary flux rope corresponds to the dark cavity. We find that the bright front merges with solar wind material swept up by the ICME. Thus, the sheath material found ahead of fast ejecta is in fact composed from both ambient solar wind material, as well the bright front. We also note that, in this simulation, the bright front is formed from the overlying streamer configuration from within which the CME erupted and is not itself coronal material swept up during the early phase of the eruption. The conclusions reached in this study are undoubtedly sensitive to the initial configuration and mechanism used to initiate the CME, and thus care should be taken when using them to interpret specific observations. On the other hand, they provide a unique, unbroken connection between remote solar and interplanetary observations. Ultimately, detailed comparisons between observations and simulation results may be able to constrain or even rule out some mechanisms of CME initiation

Riley, Pete↗