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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Flight MPT Development, Qualification and Thrust Measurement Campaign

A torsional thrust stand, calibrated for impulse bits in the range of 0.1mNs -0.5 mNs, was used to measure impulse bits during two campaigns at the NASA/GRC VF-3 Vacuum test Facility. Metal Plasma Thrusters (MPTs) with targets of Molybdenum, Copper and Stainless Steel (as used in upper stages of launch vehicles that are abandoned in LEO) were tested. This paper describes data from Mo targets (called pucks). The Cu and ss data will be presented elsewhere. Model predictions (based on a simple circuit model and published plasma parameters) were validated by data from the calibrated torsional thrust stand. The Metal Plasma Thruster uses solid metal propellant, hence requires no liquids, gases, flow valves or flow controls and has no moving parts. Total impulse ~5000Ns/U provides orbit raising and drag compensation capability.

Electric Propulsion↗
NASA NTRS1975

Correlation of boundary layer quantities for hypersonic laminar flows with zero pressure gradient for several gases

The laminar boundary layer has been theoretically studied for six gases for flows over cold walls with zero pressure gradient at Mach numbers between 5.5 and 12.5 to correlate boundary layer quantities for the various gases. The flow conditions considered correspond to those that can be generated in test facilities such as the shock tunnel and the expansion tube. Computed results obtained using real gas properties indicate that the Eckert number based on edge conditions serves to correlate the results in terms of the wall shear stress and enthalpy gradient, the Stanton number, and the momentum thickness for the various gases within plus or minus 10 per cent for Te = Tw and Te approximately 3Tw. Computed Reynolds analogy factors exhibit very good agreement with those predicted by the Colburn analogy. Velocity and displacement thicknesses correlate well with Eckert number for Te = Tw, but fail to correlate for Te approximately 3Tw. Differences in results are traced to property variations. Results show that the Eckert number is a significant correlating variable for the flows considered.

Cook, W. J.↗
NASA NTRS1990

Flow-Control Unit For Nitrogen And Hydrogen Gases

Gas-flow-control unit installed and removed as one piece replaces system that included nine separately serviced components. Unit controls and monitors flows of nitrogen and hydrogen gases. Designed for connection via fluid-interface manifold plate, reducing number of mechanical fluid-interface connections from 18 to 1. Unit provides increasing reliability, safety, and ease of maintenance, and for reducing weight, volume, and power consumption.

Chang, B. J.↗
NASA NTRS1973

Fluid undercutting in the successive channel flow of two gases.

A fluid piston technique wherein one gas displaces another gas from a horizontal channel was investigated experimentally in a laboratory simulation of the operating concept of a Mach number 9, true-energy wind tunnel. Tests were conducted over a Froude number range from 0.0015 to 0.543 at driver-to-driven gas density ratios from 0.637 to 11.0 to find the effect of fluid undercutting (or overcutting) on test duration. Other variables studied, either experimentally or analytically, include channel cross-sectional shape, channel inlet design, channel length-to-diameter ratio, Reynolds number, pretest pressurization, and channel inclination angle. Results from shadowgraph movies and pressure measurements provide a correlation of actual-to-ideal test durations for a wide range of Froude numbers and gas density ratios and indicate that the application of the fluid piston technique to the wind-tunnel concept is feasible. However, severe fluid undercutting (or overcutting) in horizontal channels occurs at lower Froude numbers and at density ratios significantly different from unity.

Guy, R. W.↗
NASA NTRS1973

Raman scattering applied to gas mixing in the successive channel flow of two gases

The Raman scattering technique has been applied to investigate the effects of fluid undercutting in a simulation of the fluid-piston concept for wind-tunnel design. Measurements of the structure of the driver-driven gas interface and of the effect of undercutting on test duration were performed. Tests were conducted over a Froude number range of 0.0021 to 0.526 at driver-to-driven gas density ratios of 1.103 and 1.573. The effects of inlet design, test-channel inclination angle, and pretest pressurization were also examined. The results are compared with shadowgraph and pressure measurements to illustrate the characteristics of the Raman technique and to explain the discrepancy between the shadowgraph and pressure results.

Hillard, M. E., Jr.↗
NASA NTRS1985

Polarization (ellipsometric) measurements of liquid condensate deposition and evaporation rates and dew points in flowing salt/ash-containing combustion gases

An application of an optical polarization technique in a combustion environment is demonstrated by following, in real-time, growth rates of boric oxide condensate on heated platinum ribbons exposed to seeded propane-air combustion gases. The results obtained agree with the results of earlier interference measurements and also with theoretical chemical vapor deposition predictions. In comparison with the interference method, the polarization technique places less stringent requirements on surface quality, which may justify the added optical components needed for such measurements.

Seshadri, K.↗
NASA NTRS2012

Modeling the Flow of Rarefied Gases at NASA

At modest temperatures, the thermal energy of atmospheric diatomic gases such as nitrogen is primarily distributed between only translational and rotational energy modes. Furthermore, these energy modes are fully excited such that the specific heat at constant volume is well approximated by the simple expression C(sub v) = 5/2 R. As a result, classical mechanics provides a suitable approximation at such temperatures of the true quantum mechanical behavior of the inter-molecular collisions of such molecules. Using classical mechanics, the transfer of energy between rotational and translation energy modes is studied. The approach of Lordi and Mates is adopted to compute the trajectories and time dependent rotational orientations and energies during the collision of two non-polar diatomic molecules. A Monte-Carlo analysis is performed collecting data from the results of many such simulations in order to estimate the rotational relaxation time. A Graphical Processing Unit (GPU) is employed to improve the performance of the Monte-Carlo analysis. A comparison of the performance of the GPU implementation to an implementation on traditional computer architecture is made. Effects of the assumed inter-molecular potential on the relaxation time are studied. The seminar will also present highlights of computational analyses performed at NASA Johnson Space Center of heat transfer in rarefied gases.

Forrest E. Lumpkin, III↗
NASA NTRS1978

Effect of pyrolysis temperature and air flow on toxicity of gases from a polycarbonate polymer

A polycarbonate polymer was evaluated for toxicity of pyrolysis gases generated at various temperatures without forced air flow and with 1 L/min air flow, using the toxicity screening test method developed at the University of San Francisco. Time to various animal responses decreased with increasing pyrolysis temperature over the range from 500 C to 800 C. There appeared to be no significant toxic effects at 400 C and lower temperatures.

Hilado, C. J.↗
NASA NTRS1991

HANA - A three-dimensional Navier-Stokes code for chemically reacting flows

A recently developed computer program for analyzing chemically reacting flows is described. The program uses a diagonal implicit algorithm to solve the equations of viscous flow for a gas in thermochemical nonequilibrium. The diagonal scheme eliminates the expense of inverting large block matrices that arise when species conservation equations are introduced. The program uses multiple zones of grids patched together and includes a k-epsilon turbulence model. Solutions are presented for hypersonic flows of air, hypersonic flows of Martian atmospheric gases, combusting flows of hydrogen/air mixtures, and combusting flows of methane/air mixtures.

Imlay, Scott T.↗
NASA NTRS1930

The boundary layer as a means of controlling the flow of liquids and gases

According to one of the main propositions of the boundary layer theory the scarcely noticeable boundary layer may, under certain conditions, have a decisive influence on the form of the external flow by causing it to separate from the wing surface. These phenomena are known to be caused by a kind of stagnation of the boundary layer at the point of separation. The present report deals with similar phenomena. It is important to note that usually the cause (external interference) directly affects only the layer close to the wall, while its indirect effect extends to a large portion of the external flow.

Schrenk, Oskar↗