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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

Experimental Validation of FE/BEM Dynamic Strain Model Under Diffuse Acoustic Field Loading

Structural finite element (FE) models naturally output displacement or acceleration response data. However, they can also be used to compute stress, internal forces, and strain response. When coupled with a boundary element model (BEM) of the fluid surrounding the structure, a fully coupled analysis can be performed. Modeling a diffuse acoustic field in the BEM fluid provides an excitation like that found when the structure is placed in a reverberation chamber. Fully coupling the structural FE model to the acoustic BEM model provides a means to predict not only the acceleration response of the panel to diffuse field loading, but also the ability to predict the dynamic stress and strain response. This type of model has been available with current predictive tools, but experimental validation of the prediction of dynamic stress or strain is difficult to find. An aluminum panel was instrumented with accelerometers and strain gages and hung in a reverberation room and subjected to a diffuse acoustic field. This paper presents the comparison of the experimental and predicted results.

Tsoi, W. Ben↗
NASA NTRS1992

NASA/DOD Aerospace Knowledge Diffusion Research Project. Paper 27: Knowledge diffusion and US government technology policy: Issues and opportunities for sci/tech librarians

Federal involvement in simulating economic growth through the development and application of technology policy is currently the subject of serious debate. A recession and the recognition that an internationally competitive economy is a prerequisite for the attainment of national goals have fostered a number of technology policy initiatives aimed at improving the economic competitiveness of American industry. This paper suggests that the successful implementation of U.S. technology policy will require the adoption of a knowledge diffusion model, the development of user oriented information products and services, and a more 'activist' approach on the part of sci/tech librarians in the provision of scientific and technical information (STI). These changes will have a dramatic impact on the sci/tech library of the future and the preparation of sci/tech librarians.

Pinelli, Thomas E.↗
NASA NTRS1992

NASA/DoD Aerospace Knowledge Diffusion Research Project. XXVII - Knowledge diffusion and U.S. government technology policy: Issues and opportunities for sci/tech librarians

Federal involvement in stimulating economic growth through the development and application of technology policy is currently the subject of serious debate. A recession and the recognition that an internationally competitive economy is a prerequisite for the attainment of national goals have fostered a number of technology policy initiatives aimed at improving the economic competitiveness of American industry. This paper suggests that the successful implementation of U.S. technology policy will require the adoption of a knowledge diffusion model, the development of user oriented information products and services, and a more 'activist' approach on the part of sci/tech librarians in the provision of scientific and technical information (STI). These changes will have a dramatic impact on the sci/tech library of the future and the preparation of sci/tech librarians.

Pinelli, Thomas E.↗
NASA NTRS2019

Observational Evidence of Magnetic Reconnection in the Terrestrial Bow Shock Transition Region

We report evidence of magnetic reconnection in the transition region of the Earth's bow shock when the angle between the shock normal and the immediate upstream magnetic field is 65°. An ion‐skin‐depth‐scale current sheet exhibits the Hall current and field pattern, electron outflow jet, and enhanced energy conversion rate through the nonideal electric field, all consistent with a reconnection diffusion region close to the X‐line. In the diffusion region, electrons are modulated by electromagnetic waves. An ion exhaust with energized field‐aligned ions and electron parallel heating are observed in the same shock transition region. The energized ions are more separated from the inflowing ions in velocity above the current sheet than below, possibly due to the shear flow between the two inflow regions. The observation suggests that magnetic reconnection may contribute to shock energy dissipation.

Wang, Shan↗
NASA NTRS1993

NASA/DoD Aerospace Knowledge Diffusion Research Project. Paper 29: The US government technical report and the transfer of federally funded aerospace R and D

This article discusses the U.S. government technical report and the transfer of federally funded aerospace research and development in a conceptual framework of the federal government as a producer of scientific and technical information. The article summarizes current literature and research and discusses U.S. government technical report use and the importance of using data obtained from the NASA/DoD Aerospace Knowledge Diffusion Research Project. The authors make a case for changing existing U.S. technology policy and present a research agenda for the U.S. government technical report.

Pinelli, Thomas E.↗
NASA NTRS1985

The effect of the neutral sheet structure of the interplanetary magnetic field on cosmic ray distribution in space

Results of the numerical solution of the anistoropic diffusion equation are presented. The modulation depth of galactic cosmic rays is defined by the degree of curvature of the neutral current sheet in the heliosphere. The effect of the regular interplanetary magnetic field (IMF) on cosmic ray anisotropy in the period of solar activity minimum (in 1976) is analyzed by the data of the neutron super-monitors of the world network, and the heliolatitudinal gradient and cosmic ray diffusion coefficient are defined.

Alania, M. V.↗
NASA NTRS1976

Silicon solar cells from transition metal doped Czochralski and web crystals

The influence of metallic impurities on solar cell characteristics has been examined to establish the cost sensitive purity versus performance trade-offs. Solar cells were fabricated on 2 to 4 ohm-cm p-type substrates obtained by Czochralski and dendritic web growth processes. Controlled amounts of metallic impurities were introduced into the melt during growth and included Fe, Cr, Mn, Ni, Cu, Ti, V, Zr, Mg, Zn, and Al. Impurity concentrations in the crystals were determined using emission and mass spectrographic techniques and in some cases by neutron activation analysis. The solar cells were characterized by means of a computer program to curve-fit measured voltage-current data. The principal effect of the added impurities is a degradation of lifetime and diffusion length.

Davis, J. R.↗
NASA NTRS1979

Modeling of thin, back-wall silicon solar cells

The performance of silicon solar cells with p-n junctions on the nonilluminated surface (i.e., upside-down or back-wall cells) was calculated. These structures consisted of a uniformly shaped p-type substrate layer, a p(+)-type field layer on the front (illuminated) surface, and a shallow, n-type junction on the back (nonilluminated) surface. A four-layer solar cell model was used to calculate efficiency, open-circuit voltage, and short-circuit current. The effect on performance of p-layer thickness and resistivity was determined. The diffusion length was varied to simulate the effect of radiation damage. The results show that peak initial efficiencies greater than 15 percent are possible for cell thicknesses or 100 micrometers or less. After 10 years of radiation damage in geosynchronous orbit, thin (25 to 50 micrometers thick) cells made from 10 to 100 ohm cm material show the smallest decrease (approximately 10 percent) in performance.

Baraona, C. R.↗
NASA NTRS1984

A High-speed Characterization Technique for Solar Silicon

High-speed crystal growth techniques demand high-speed characterization techniques to allow a timely feed-back of information to the crystal growers. The unique properties of the Si electrolyte-contact (SEC) provide for an extremely fast and simple measurement of the light-induced photo-current for any piece of Si without lengthy preparation of the specimen. Electropolishing at high anodic current densities allows for insitu generation of fresh surfaces whereas preferential etching of defects in various modes is possible at low current densities. In n-type Si a simple estimation of the minority-carrier diffusion length is possible in many cases. Laser-scanning enables local probing of the photocurrent and provides data about the homogeneity of a sample. The experimental realization of the method is described in detail and examples are given and discussed.

Lehmann, V.↗
NASA NTRS1985

Preliminary study: Moisture-polymer interaction. Stuby objectives

The problems associated with mathematically modeling water-module interaction phenomena, including sorption and desorption, diffusion, and permeation are discussed. With reliable analytical models, an extensive materials data base, and solar radiation surface meteorological observations (SOLMET) weather data, predicting module lifetimes in realistic environments can become a practical reality. The status of the present techniques of simulating the various transport mechanisms was reported. The Dent model (a modified Brunauer-Emmet-Teller) approach represented polyvinyl butyral (PVB) sorption data. A 100-layer material model and Fick's diffusion model gave diffusivity values exhibiting adequate agreement with those measured for PVB. Diffusivity of PVB is concentration dependent, decreasing as the water content in PVB increases. The temperature dependence of diffusion in PVB is well modeled by the Arrhenius rate equation. Equilibrium conductivity and leakage current data are well represented by Hearle's model for bulk ionic conductivity. A nodal network analysis using the Systems Improved Numerical Differencing Analyzer (SINDA) Thermal Analyzer gave reasonable correlation with measurable data. It is concluded that realistic lifetime predictions seem to be feasible.

Wen, L. C.↗
NASA NTRS1988

Multipoint observations of the magnetopause - Results from ISEE and AMPTE

Multiple spacecraft observations of the magnetopause have made it possible to infer boundary motion and structure, and to compare these with theoretical expectations. the results of the ISEE mission indicate the magnetopause is thicker than expected, often ten magnetosheath ion gyroradii or more, and that its characteristic radial motion is usually sub-Alfvenic. With small spacecraft separations it is possible to infer considerable small-scale magnetic structure within the current layer, suggesting filamentary currents much smaller than an ion gyroradius. Such a microstructure may be important in particle diffusion and, hence, reconnection. There are also phenomena on much larger scales, the highly variable boundary layer, flux transfer events and surface waves due to dynamic pressure variations, the structure of which can be best determined when spacecraft separations are large.

Elphic, R. C.↗
NASA NTRS1989

Physical phenomena and the microgravity response

The living biological cell is not a sack of Newtonian fluid containing systems of chemical reactions at equilibrium. It is a kinetically driven system, not a thermodynamically driven system. While the cell as a whole might be considered isothermal, at the scale of individual macromolecular events there is heat generated, and presumably sharp thermal gradients exist at the submicron level. Basic physical phenomena to be considered when exploring the cell's response to inertial acceleration include particle sedimentation, solutal convection, motility electrokinetics, cytoskeletal work, and hydrostatic pressure. Protein crystal growth experiments, for example, illustrate the profound effects of convection currents on macromolecular assembly. Reaction kinetics in the cell vary all the way from diffusion-limited to life-time limited. Transport processes vary from free diffusion, to facilitated and active transmembrane transport, to contractile-protein-driven motility, to crystalline immobilization. At least four physical states of matter exist in the cell: aqueous, non-aqueous, immiscible-aqueous, and solid. Levels of order vary from crystalline to free solution. The relative volumes of these states profoundly influence the cell's response to inertial acceleration. Such subcellular phenomena as stretch-receptor activation, microtubule re-assembly, synaptic junction formation, chemotactic receptor activation, and statolith sedimentation were studied recently with respect to both their basic mechanisms and their responsiveness to inertial acceleration. From such studies a widespread role of cytoskeletal organization is becoming apparent.

Todd, Paul↗
NASA NTRS2001

First Materials Science Research Rack Capabilities and Design Features

The first Materials Science Research Rack (MSRR-1) will accommodate dual Experiment Modules (EM's) and provide simultaneous on-orbit processing operations capability. The first international Materials Science Experiment Module for the MSRR-1 is an international cooperative research activity between NASA's Marshall Space Flight Center (MSFC) and the European Space Agency's (ESA) European Space Research and Technology Center. (ESTEC). This International Standard Payload Rack (ISPR) will contain the Materials Science Laboratory (MSL) developed by ESA as an Experiment Module. The MSL Experiment Module will accommodate several on-orbit exchangeable experiment-specific Module Inserts. Module Inserts currently planned are a Quench Module Insert, Low Gradient Furnace, Solidification with Quench Furnace, and Diffusion Module Insert. The second Experiment Module for the MSRR-1 configuration is a commercial device supplied by MSFC's Space Products Department (SPD). It includes capabilities for vapor transport processes and liquid metal sintering. This Experiment Module will be replaced on-orbit with other NASA Materials Science EMs.

Schaefer, D.↗
NASA NTRS2003

Integrated RANS-LES Computations of Turbomachinery Components: Generic Compressor/Diffuser

The goal of the current study is to apply the coupled RANS-LES approach to a compressor-diffuser geometry of a gas turbine. This flow configuration is important, since the outflow of the compressor alters the flow field in the subsequent diffuser. A detailed knowledge of the flow field in this section allows to optimize the difuser design in order to to achieve a decrease of pressure loss. Here, the NASA stage 35 compressor is coupled with a generic diffuser in order to assess the integrated RANS-LES approach.

Schlueter, J. U.↗
NASA NTRS2000

The Composition of Dust in the Interstellar Medium

In this talk I will review our current knowledge of the composition, abundance, and distribution of organic and related compounds in the diffuse and dense interstellar media (ISM) of our galaxy. This knowledge is the result of a combined effort of practitioners of telescopic observation, theory, and laboratory studies. We are increasingly coming to understand that the population of organic materials in space is complex and that it contains molecular species that are of direct interest to the fields not only of astrophysics and astrochemistry, but also astrobiology. In this talk I will concentrate my discussion on the various chemical processes that occur in the ISM, the classes of compounds they produce, and the various @-pes of evidence that we have that some of these materials survive incorporation into newly forming stellar/planetary systems. Finally, I will end with some comments on the possible implications of these materials for the origin of life.

Sandford, Scott A.↗
NASA NTRS1999

Validation of the CERES Shortwave Measurements over Desert and Cloud Scenes

The Clouds and the Earth's Radiant Energy System (CERES) broadband shortwave channel, 0.3 - 5 micron, measures atmosphere and surface reflected solar radiation. CERES provides an in-flight tungsten lamp to monitor the shortwave radiometric stability over the lifetime of the instrument. Initial Tropical Rainfall Measurement Mission (TRMM) tungsten calibration results indicate a 0.6% change over the first six months of mission life. The three channel intercomparison technique and the solar diffuser calibration results show shortwave stabilities of 0.2% and 0.3% for the same time period. Current belief is that the tungsten lamp, not the radiometer, has drifted. Radiometers, optics, and onboard calibrators exposed to the harsh space environment often degrade. Independent validation studies based on bright Earth viewing measurements are necessary to support the in-flight filtered calibration results. Instrument measurements of filtered radiances are

Currey, Chris↗
NASA NTRS2004

Optical Sensors for Biomolecules Using Nanoporous Sol-Gel Materials

An important consideration for space missions to Mars is the ability to detect biosignatures. Solid-state sensing elements for optical detection of biological entities are possible using sol-gel based biologically active materials. We have used these materials as optical sensing elements in a variety of bioassays, including immunoassays and enzyme assays. By immobilizing an appropriate biomolecule in the sol-gel sensing element, we have successfully detected analytes such as amino acids and hormones. In the case of the amino acid glutamate, the enzyme glutamate dehydrogenase was the immobilized molecule, whereas in the case of the hormone cortisol, an anti-cortisol antibody was immobilized in the sensing element. In this previous work with immobilized enzymes and antibodies, excellent sensitivity and specificity were demonstrated in a variety of formats including bulk materials, thin films and fibers. We believe that the sol-gel approach is an attractive platform for bioastronautics sensing applications because of the ability to detect a wide range of entities such as amino acids, fatty acids, hopanes, porphyrins, etc. The sol-gel approach produces an optically transparent 3D silica matrix that forms around the biomolecule of interest, thus stabilizing its structure and functionality while allowing for optical detection. This encapsulation process protects the biomolecule and leads to a more "rugged" sensor. The nanoporous structure of the sol-gel matrix allows diffusion of small target molecules but keeps larger, biomolecules immobilized in the pores. We are currently developing these biologically active sol-gel materials into small portable devices for on-orbit cortisol detection

Fang, Jonathan↗