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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Optical Radiation from Shock-Compressed Materials

Recent observations of shock-induced radiation from oxides, silicates, and metals of geophysical interest constrain the shock-compressed temperature of these materials. The relationships between the temperature inferred from the observed radiation and the temperature of the shock-compressed film or foil and/or window were investigated. Changes of the temperature field in each target component away from that of their respective shock-compressed states occur because of: shock-impedance mismatch between target components; thermal mismatch between target components; surface roughness at target interfaces; and conduction within and between target components. In particular, conduction may affect the temperature of the film/foil window interface on the time scale of the experiments, and so control the intensity and history of the dominant thermal radiation sources in the target. This type of model was used to interpret the radiation emitted by a variety of shock-compressed materials and interfaces.

Svendsen, Robert F., Jr.↗
NASA NTRS1987

The wind-disk interaction in X-ray burst sources. II - Collimation by thick accretion disks

The wind-disk interaction model in type I cosmic X-ray bursts is here examined in the case where the accretion disk surrounding the neutron star is geometrically thick. The funnel structure along the rotation axis of such a system may collimate the radiatively driven wind following a thermonuclear flash in the star's surface layers, and could thereby enhance the radiative flux (diffusive plus advective) along the beam direction. It is shown that for plausible conditions, this mechanism can account for the super-Eddington fluxes observed in some bursts. The overall time scale for variability, the color temperature, and the spectral shape in this picture are consistent with the observed properties of type I X-ray bursts.

Melia, Fulvio↗
NASA NTRS1987

Space station onboard propulsion system: Technology study

The objective was to prepare for the design of the space station propulsion system. Propulsion system concepts were defined and schematics were developed for the most viable concepts. A dual model bipropellant system was found to deliver the largest amount of payload. However, when resupply is considered, an electrolysis system with 10 percent accumulators requires less resupply propellant, though it is penalized by the amount of time required to fill the accumulators and the power requirements for the electrolyzer. A computer simulation was prepared, which was originally intended to simulate the water electrolysis propulsion system but which was expanded to model other types of systems such as cold gas, monopropellant and bipropellant storable systems.

Mcallister, J. G.↗
NASA NTRS1987

Bioseparations - Flight experiment support research

While important principles of electrokinetic technology, such as electrophoresis, have been demonstrated for microgravity environments and promise to be able to alleviate many of the practical limitations imposed by gravity, the minimal crew time and sample-handling facilities available in orbit call for almost total reliance on postflight analysis of separated fractions. Since cell separations are the most difficult to accomplish in 1-g, two model cell types have been studied intensively to determine the basic relationships between cell surface charge and secretory functions. A rationale has been developed for selecting and qualifying new cell types and proteins that warrant processing in microgravity.

Morrison, Dennis R.↗
NASA NTRS1988

Analytical models of helical wind-type astrophysical flows

Three classes of analytic solutions of the basic hydrodynamic equations assumed to govern plasma flow in the atmosphere of a rotating astrophysical object are presented. Attention is focused on the balance of the inertial and gravitational forces with suitable pressure gradients in the presence of rotation. The solutions are written in terms of dimensionless physical parameters in order to facilitate their direct application to specific astrophysical flows, such as winds from massive premain sequence objects and T Tauri stars, and bipolar flows in young stellar objects.

Tsinganos, K.↗
NASA NTRS1986

A methodology for the design and evaluation of user interfaces for interactive information systems

The definition of proposed research addressing the development and validation of a methodology for the design and evaluation of user interfaces for interactive information systems is given. The major objectives of this research are: the development of a comprehensive, objective, and generalizable methodology for the design and evaluation of user interfaces for information systems; the development of equations and/or analytical models to characterize user behavior and the performance of a designed interface; the design of a prototype system for the development and administration of user interfaces; and the design and use of controlled experiments to support the research and test/validate the proposed methodology. The proposed design methodology views the user interface as a virtual machine composed of three layers: an interactive layer, a dialogue manager layer, and an application interface layer. A command language model of user system interactions is presented because of its inherent simplicity and structured approach based on interaction events. All interaction events have a common structure based on common generic elements necessary for a successful dialogue. It is shown that, using this model, various types of interfaces could be designed and implemented to accommodate various categories of users. The implementation methodology is discussed in terms of how to store and organize the information.

Dominick, Wayne D.↗
NASA NTRS1990

SINDA '85/FLUINT, Version 2.2

SINDA, Systems Improved Numerical Differencing Analyzer, software system developed for solving physical problems governed by diffusion-type equations modeled by lumped-parameter representations. Used as general thermal analyzer with resistor-and-capacitor-network representations, adapted to wide range of problems represented by such differential equations as Fourier, Poisson, or LaPlace. Software system updated. FLUINT, FLUid INTegrator, is advanced, one-dimensional fluid-analysis program solving equations of arbitrary fluid-flow networks. Written in FORTRAN and ASSEMBLER.

Cullimore, Brent↗
NASA NTRS1989

Investigations on gel forming media use in low gravity bioseparations research

Research on gelling media and conditions suitable for the preservation of the spatial configuration of cell suspensions and macromolecular solutions after separation in free fluid during low gravity experiments is presented. The examples studied included free electrophoresis of cells in a cylindrical column and two-phase aqueous polymer separation. Microgravity electrophoresis experiments were simulated by separating model cell types (animal or human) in a vertical density gradient containing low-conductivity buffer, 1.7-6.5 percent Ficoll, 6.8-5.0 percent sucrose, and 1 percent SeaPrep low-melting temperature agarose. Upon cooling, a gel formed in the column and cells could be captured at the forming locations. Two-phase extraction experiments were simulated using two-polymer solutions in which phase separation occurs in normal saline at temperatures compatible with cell viability and in which one or both phases form a gel upon cooling. Suitable polymers included commercial agaroses (1-2 percent), maltodextrin (5-7 percent), and gelatin (5-20 percent).

Todd, Paul↗
NASA NTRS1990

Evaluation of non-Fourier heat waves influenced by nonlinear/linear boundary effects employing an explicit architecture and controlled stabilization

The present paper is concerned with the problem of heat waves in solids, where, the heat transport due to conduction occurs as propagating thermal disturbances which are transmitted at finite but high speeds. Starting from the general heat flux model of the Jeffrey's-type, and subsequent formulations leading to the Cattaneo-type heat flux model, an evaluation of the heat transport behavior is described for models influenced by non-Fourier effects and subjected to general nonlinear/linear boundary conditions. An explicit time-integration architecture is employed which effectively provides not only accurate representations of the relaxation effects and general boundary conditions but also seeks to provide an understanding of the representative thermal behavior and heat transport mechanisms for a variety of physical situations.

Tamma, Kumar K.↗
NASA NTRS1990

Applicability and evaluation of an implicit self-starting unconditionally stable methodology for the dynamics of structures

The applicability and evaluation of a new self-starting, unconditionally stable, implicit methodology of computation for the dynamics of structures is described. The methodology offers different perspectives and architecture for structural dynamics compared with the traditional (widely advocated and commonly used) time integration methods. It is based on velocity representations and architecture and uses finite elements as the principal analysis tool for structural dynamic modeling/analysis. In particular, the dynamics of beam-type flexural models are considered, and comparative results validate and support the proposed use of the self-starting methodology of computation for the dynamics of linear/nonlinear structures. The overall effectiveness and elegance strongly support its use in most existing commercial codes.

Tamma, Kumar K.↗
NASA NTRS1989

An improved electrothermal model for the ERBE nonscanning radiometer - Comparison of predicted and measured behavior during solar observations

The improved Earth Radiation Budget Experiment nonscanning-channels electrothermal model presented is used to model two types of solar observations: those obtained through the solar port during solar calibration, and and those obtained during the satellite pitch-over maneuver, in which the sun is observed by the radiometer while it is in earth-viewing configuration. Thermal noise has been separately studied to evaluate its contribution to the radiative energy absorbed by the active cavity. It is found that the scattering of the collimated solar radiation contributes an average of 0.071 mW during solar calibration.

Tira, Nour E.↗
NASA NTRS1990

CFD validation for aerodynamic flows - Challenge for the '90's

The process of computational fluid dynamics (CFD) validation is described from two perspectives, numerical error validation and physical model validation. Errors associated with time and space discretization, grid refinement, numerical dissipation, and level of solution convergence, are all possible sources of numerical error. The second aspect of CFD code validation is associated with the governing equations and the physical models, e.g., chemistry and turbulence models. This type of validation requires comparisons with carefully conducted experiments and is the primary aspect of the validation process discussed in this paper. Examples of validation are shown for selected Reynolds-averaged Navier-Stokes codes for conditions from transonic through hypersonic. Since code applications are becoming more complex, it no longer suffices to use data from surface or integral quantities alone to provide the required validation. Flow field surveys and experimental boundary condition measurements are emerging as critical data that must be obtained for CFD code validation. Progress in the overall level of validation is shown to be improving. However, future challenges remain, some of which are enumerated.

Marvin, Joseph G.↗
NASA NTRS1991

Computer Simulation Of A Small Turboshaft Engine

Component-type mathematical model of small turboshaft engine developed for use in real-time computer simulations of dynamics of helicopter flight. Yields shaft speeds, torques, fuel-consumption rates, and other operating parameters with sufficient accuracy for use in real-time simulation of maneuvers involving large transients in power and/or severe accelerations.

Ballin, Mark G.↗
NASA NTRS1990

Modal analysis of UH-60A instrumented rotor blades

The dynamic characteristics of instrumented and production UH-60A Black Hawk main rotor blades were measured, and the results were validated with NASTRAN finite element models. The blades tested included pressure and strain-gage instrumented blades, which are part of the NASA Airloads Flight Research Phase of the Modern Technology Rotor Program. The dynamic similarity of the blades was required for accurate data collection in this program. Therefore, a nonrotating blade modal analysis was performed on the first 10 free-free modes to measure blade similarities. The results showed small differences between the modal frequencies of instrumented and production blades and a close correlation with the NASTRAN models. This type of modal testing and analysis is recommended as a standard procedure for future instrumented blade flight testing.

Hamade, Karen S.↗
NASA NTRS1991

The process group approach to reliable distributed computing

The difficulty of developing reliable distributed software is an impediment to applying distributed computing technology in many settings. Experience with the ISIS system suggests that a structured approach based on virtually synchronous process groups yields systems which are substantially easier to develop, fault-tolerance, and self-managing. Six years of research on ISIS are reviewed, describing the model, the types of applications to which ISIS was applied, and some of the reasoning that underlies a recent effort to redesign and reimplement ISIS as a much smaller, lightweight system.

Birman, Kenneth P.↗
NASA NTRS1990

Modal analysis of UH 60A instrumented rotor blades

The dynamic characteristics of instrumented and production UH-60A Black Hawk main rotor blades were measured, and the results were validated with NASTRAN finite element models. The blades tested included pressure and strain-gage instrumented blades which are part of NASA's Airloads Flight Research Phase of the Modern Technology Rotor Program. The dynamic similarity of the blades was required for accurate data collection in this program. Therefore, a nonrotating blade modal analysis was performed on the first 10 free-free modes to measure blade similarities. The results showed small differences between the modal frequencies of instrumented and production blades and a close correlation with the NASTRAN models. This type of modal testing and analysis is recommended as a standard procedure for future instrumented blade flight testing.

Hamade, Karen S.↗
NASA NTRS1991

Radioactivities and gamma-rays from supernovae

An account is given of the implications of several calculations relevant to the estimation of gamma-ray signals from various explosive astronomical phenomena. After discussing efforts to constrain the amounts of Ni-57 and Ti-44 produced in SN 1987A, attention is given to the production of Al-27 in massive stars and SNs. A 'delayed detonation' model of type Ia SNs is proposed, and the gamma-ray signal which may be expected when a bare white dwarf collapses directly into a neutron star is discussed.

Woosley, S. E.↗
NASA NTRS1992

Evidence for distillation in the formation of HAL and related hibonite inclusions

New Ca- and Ti-isotopic analyses of DH-H1, 7-404, and 7-971, and Mg-isotopic analyses on DH-H1 and 7-404 are reported. O-isotopic analyses of HAL, 7-404, 7-971, and a variety of other refractory inclusions from Murchison were made in order to establish the presence or absence of FUN O-isotopic systematics. A higonite-rich residue produced by the evaporation of kaersutite was analyzed for its trace-element and isotopic abundances to see if any of the characteristics of FUN hibonite inclusions can be produced by distillation in the laboratory. These data are then used to evaluate for all four inclusions the HAL-type formation models originally proposed by Allen et al. (1980) and Lee et al. (1980). The four inclusions were found to have very similar chemical and isotopic features. All are characterized by large Ce depletions and very low Mg, Ti, and V concentrations compared to other meteoritic hibonites. All four inclusions have delta(C-48) within error of -5 per mil. Ca-, Ti-, and O-isotopic compositions are fractionated with enrichments of the heavy isotopes, and the Ti-isotopic mass fractionation is inversely correlated with Ti concentration. It is concluded that the inclusions formed primarily as distillation residues in accord with the early conclusions.

Ireland, Trevor R.↗