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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Viscosity measurements at high temperature and high pressure: A novel technique

The extensive numerical modelling of transport phenomena was performed for the melt growth of mercury cadmium telluride. To increase the fidelity of modelling the kinematic viscosity of liquid Hg(1-x)Cd(x)Te was determined at various compositions in the range of x between 0 and 0.2 and at temperatures around and below the respective melting point. The phase diagram of Hg(1-x)Cd(x)Te shows that for this range the melting point varies from 670 C for pure HgTe to 790 C at x=0.2. The vapor pressure above the melt varies correspondingly from 15 to about 40 atm. Hence, the measurement of viscosities in this system requires a technique that allows for combinations of high temperatures and pressures. In addition, a closed isothermal system is required. The high pressure melt container must also be inert to molten Hg(1-x)Cd(x)Te to avoid possible errors from contamination of the liquid. A novel technique that largely circumvents the above experimental problems is described. Its theory is also presented.

Jin, Wei-Qing↗
NASA NTRS1990

Microgravity research at LeRC

The NASA Lewis Research Center is conducting a wide variety of ground-based science and microgravity flight experiments in the disciplines of fluid physics and transport phenomena, combustion science, and materials science. Extensive use is made of low-gravity ground-based facilities such as drop towers and a Learjet aircraft, as well as extensive normal-gravity laboratories. The ground-based facilities are utilized to execute science programs, perform precursor tests to define space experiment science requirements and conceptual designs, and also to perform tests for space experiment technology development and verification. Finally, flight hardware is designed, developed and flown on the Space Shuttle.

Kohl, Fred J.↗
NASA NTRS1990

Symmetrization of conservation laws with entropy for high-temperature hypersonic computations

Results of Hughes, France, and Mallet are generalized to conservation law systems taking into account high-temperature effects. Symmetric forms of different equation sets are derived in terms of entropy variables. First, the case of a general divariant gas is studied; it can be specialized to the usual Navier-Stokes equations, as well as to situations where the gas is vibrationally excited, and undergoes equilibrium chemical reactions. The case of gas in thermochemical nonequilibrium is considered next. Transport phenomena, and in particular mass diffusion, are examined in the framework of symmetric advective-diffusive systems.

Chalot, F.↗
NASA NTRS1992

Charge-Carrier-Scattering Spectroscopy With BEEM

Ballistic-electron-emission microscopy (BEEM) constitutes basis of new spectroscopy of scattering of electrons and holes. Pointed tip electrode scans near surface of metal about 100 angstrom thick on semiconductor. Principle similar to scanning tunneling microscope, except metal acts as third electrode. Used to investigate transport phenomena, scattering phenomena, and creation of hot charge carriers in Au/Si and Au/GaAs metal/semiconductor microstructures.

Hecht, Michael H.↗
NASA NTRS1991

Microgravity Science and Applications Program tasks, 1990 revision

The active research tasks as of the end of the fiscal year 1990 sponsored by the Microgravity Science and Applications Division of the NASA Office of Space Science and Applications are compiled. The purpose is to provide an overview of the program scope for managers and scientists in industry, university, and government communities. The report includes an introductory description of the program, the strategy and overall goal; an index of principle investigators; and a description of each task. A list of recent publications is also provided. The tasks are grouped into six major categories: electronic materials; solidification of metals, alloys, and composites; fluid dynamics and transport phenomena; biotechnology; glasses and ceramics; combustion; experimental technology; facilities; and Physics And Chemistry Experiments (PACE). The tasks are divided into ground-based and flight experiments.

Source record↗
NASA NTRS1991

Microgravity Program strategic plan, 1991

The all encompassing objective of the NASA Microgravity Program is the use of space as a lab to conduct research and development. The on-orbit microgravity environment, with its substantially reduced buoyancy forces, hydrostatic pressures, and sedimentation, enables the conduction of scientific studies not possible on Earth. This environment allows processes to be isolated and controlled with an accuracy that cannot be obtained in the terrestrial environment. The Microgravity Science and Applications Div. has defined three major science categories in order to develop a program structure: fundamental science, including the study of the behavior of fluids, transport phenomena, condensed matter physics, and combustion science; materials science, including electronic and photonic materials, metals and alloys, and glasses and ceramics; and biotechnology, focusing on macromolecular crystal growth as well as cell and molecular science. Experiments in these areas seek to provide observations of complex phenomena and measurements of physical attributes with a precision that is enabled by the microgravity environment.

Source record↗
NASA NTRS1992

A Microgravity Science and Applications Program overview

The Microgravity Science and Space Applications Program (MSSAP) is described in terms of the research it supports in fields related to physical processes and materials. Three primary fields are reviewed which include fundamental sciences such as transport phenomena, materials science, and biotechnology issues such as macromolecular crystal growth. The program strategy is to begin with MSSAP studies in ground-based facilities such as drop towers and to evolve to flight experiments as the research achieves technical maturity. Ground-based experiments in progress include the Acceleration Characterization and Analysis Project and the Solid Surface Combustion Experiment (SSCE). Several furnace experiments for materials studies are described including flight tests for the SSCE, and reference is given to a flight for the Protein-Crystal Growth Experiment.

Kicza, M. E.↗
NASA NTRS1991

Theoretical and computational dynamics of a compressible flow

An introduction to the theoretical and computational fluid dynamics of a compressible fluid is presented. The general topics addressed include: thermodynamics and physical properties of compressible fluids; 1D flow of an inviscid compressible fluid; shock waves; fundamental equations of the dynamics of a compressible inviscid non-heat-conducting and radiating fluid, method of small perturbations, linearized theory; 2D subsonic steady potential flow; hodograph and rheograph methods, exact solutions of 2D insentropic steady flow equations, 2D steady transonic and hypersonic flows, method of characteristics, linearized theory of 3D potential flow, nonlinear theory of 3D compressibe flow, anisentropic (rotational) flow of inviscid compressible fluid, electromagnetogasdynamics, multiphase flows, flows of a compressible fluid with transport phenomena.

Pai, Shih-I↗
NASA NTRS1992

Gravitational and thermal effects in CVD flow and deposition

A three-phased approach is used to investigate the transport phenomena occurring in horizontal CVD reactors. The three phases are made up of laser velocimetry experimental investigations, numerical CFD modeling, and metal-organic chemical vapor deposition experimental studies. Laser velocimetry measurements of flow in a horizontal reactor with a cylindrical flow channel and tilted susceptor demonstrate velocity components arising from thermal expansion and buoyancy effects that significantly exceed the velocity components due to the external applied flow. MOCVD of InP and GaAs thin films in a horizontal reactor channel with a rectangular cross section and a tilted susceptor has also been examined.

Clark, I. O.↗
NASA NTRS1991

A survey of spacecraft thermal design solutions

A review of activities at the NASA/Marshall Space Flight Center in the heat transfer and thermodynamics disciplines as well as attendant fluid mechanics, transport phenomena, and computer science applications is presented. Attention is focused on recent activities including the Hubble Space Telescope, and large space instruments, particularly telescope thermal control systems such as those flown aboard Spacelab 2 and the Astro missions. Emphasis is placed on defining the thermal control features, unique design schemes, and performance of selected programs. Results obtained both by ground testing and analytical means, as well as flight and postflight data are presented.

Humphries, R.↗
NASA NTRS1992

A more accurate nonequilibrium air radiation code - NEQAIR second generation

Two experiments, one an equilibrium flow in a plasma torch at Stanford, the other a nonequilibrium flow in a SDIO/IST Bow-Shock-Ultra-Violet missile flight, have provided the basis for modifying, enhancing, and testing the well-known radiation code, NEQAIR. The original code, herein termed NEQAIR1, lacked computational efficiency, accurate data for some species and the flexibility to handle a variety of species. The modified code, herein termed NEQAIR2, incorporates recent findings in the spectroscopic and radiation models. It can handle any number of species and radiative bands in a gas whose thermodynamic state can be described by up to four temperatures. It provides a new capability of computing very fine spectra in a reasonable CPU time, while including transport phenomena along the line of sight and the characteristics of instruments that were used in the measurements. Such a new tool should allow more accurate testing and diagnosis of the different physical models used in numerical simulations of radiating, low density, high energy flows.

Moreau, Stephane↗
NASA NTRS1993

Chemical-Vapor Deposition Of Silicon Carbide

Report describes experiments in chemical-vapor deposition of silicon carbide by pyrolysis of dimethyldichlorosilane in hydrogen and argon carrier gases. Directed toward understanding chemical-kinetic and mass-transport phenomena affecting infiltration of reactants into, and deposition of SiC upon, fabrics. Part of continuing effort to develop method of efficient and more nearly uniform deposition of silicon carbide matrix throughout fabric piles to make improved fabric/SiC-matrix composite materials.

Cagliostro, D. E.↗
NASA NTRS1991

AlGaAs-GaAs quantum-well lasers for direct solar photopumping

The paper theoretically examines the solar power requirements for low-threshold AlGaAs-GaAs quantum-well lasers directly photopumped by focused sunlight. A model of separate-confinement quantum-well-heterostructure (SCQWH) lasers was developed, which explicitly treats absorption and transport phenomena relevant to solar pumping. The model was used to identify separate-confinement single-quantum-well laser structures which should operate at photoexcitation intensities of less than 10,000 suns.

Unnikrishnan, Sreenath↗
NASA NTRS1993

Pressurization and expulsion of a flightweight liquid hydrogen tank

Experimental results are presented for pressurization and expulsion of a flightweight 4.89 cu m liquid hydrogen storage tank under normal gravity conditions. Pressurization and expulsion times were parametrically varied to study the effects of longer transfer times expected in future space flight applications. It was found that the increase in pressurant consumption with increased operational time is significant at shorter pressurization or expulsion durations and diminishes as the duration lengthens. Gas-to-wall heat transfer in the ullage was the dominant mode of energy exchange, with more than 50 percent of the pressurant energy being lost to tank wall heating in expulsions and the long duration pressurizations. Advanced data analysis will require a multidimensional approach combined with improved measurement capabilities of liquid-vapor interfacial transport phenomena.

Van Dresar, N. T.↗
NASA NTRS1993

Ion mixing in the plasma sheet boundary layer by drift instabilities

The linear stability properties of collisionless drift instabilities are analyzed in a Harris equilibrium model of the plasma sheet boundary layer (PSBL). The strearmng ions with drift-type instabilities driven in the PSBL are considered. The fluid approximation leads to growth but predicts that the mode width approaches the gyroradius of the energetic ions. Thus an integral equation theory for the modes is developed taking into account that in the PSBL the curvature drift is weak compared with the grad-B drift. The exact wave particle resonance is kept in the nonlocal response functions. Plasma density, temperature, and magnetic gradient drift motions are taken into account. The drift modes produce an anomalous cross-field momentum transport mixing the PSBL ions on the time scale of tens of seconds. A nonlinear simulation is performed which shows the coalescence of the small scale, fast growing modes into large-scale vortices. The relation between these collective modes and plasma sheet transport phenomena is discussed including the comparison with the competing plasma mixing from single-particle stochasticity.

Horton, W.↗
NASA NTRS1993

Pressurization and expulsion of a flightweight liquid hydrogen tank

Experimental results are presented for pressurization and expulsion of a flight-weight 4.89 cu m liquid hydrogen storage tank under normal gravity conditions. Pressurization and expulsion times are parametrically varied to study the effects of longer transfer times expected in future space flight applications. It is found that the increase in pressurant consumption with increased operational time is significant at shorter pressurization or expulsion durations and diminishes as the duration lengthens. Gas-to-wall heat transfer in the ullage is the dominant mode of energy exchange, with more than 50 percent of the pressurant energy being lost to tank wall heating in expulsions and the long duration pressurizations. Advanced data analysis will require a multidimensional approach combined with improved measurement capabilities of liquid-vapor interfacial transport phenomena.

Vandresar, N. T.↗
NASA NTRS1994

Gravity-dependent transport in industrial processes

Gravity-dependent transport phenomena in various industrial processes are investigated in order to address a broader range of microgravity phenomena and to develop new applications of microgravity. A number of important topics are identified and analyzed in detail. The present article describes results on coating flow, zeolite growth, and rotating electrochemical system.

Ostrach, Simon↗
NASA NTRS1995

Numerical modeling of Bridgman growth of PbSnTe in a magnetic field

In this work we study heat and mass transport, fluid motion, and solid/liquid phase change in the process of steady Bridgman growth of Pb(.8)Sn(.2)Te (LTT) in an axially-imposed uniform magnetic field under terrestrial and microgravity conditions. In particular, this research is concerned with the interrelationships among segregation, buoyancy-driven convection, and magnetic damping in the LTT melt. The main objectives are to provide a quantitative understanding of the complex transport phenomena during solidification of the nondilute binary of LTT, to provide estimates of the strength of magnetic field required to achieve the desired diffusion-dominated growth, and to assess the role of magnetic damping for space and earth based control of the buoyancy-induced convection. The problem was solved by using FIDAP and numerical results for both vertical and horizontal growth configurations with respect to the acceleration of gravity vector are presented.

Yao, Minwu↗