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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 1,369 records · Page 76
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Displacement of plasma protein and conduction velocity in rats under action of acceleration forces and hypokinesia

The permeability of capillary vessels was investigated in order to determine if acceleration alone or following prolonged hypokinesia would induce changes in the vascular wall leading to the penetration by l-albumins and/or proteins with larger molecules. In rats undergoing action of +5 Gz accelerations, no increase in vascular permeability, as tested with the use of (Cr-5k)-globulin, was demostrated. In rats immobilized for 4 weeks before centrifugation, rather weak migration of (Cr-51)-globulin from the vessels was observed. Immobilization resulted also in lowering of conduction velocity in the sciatic nerve.

Baranski, S.↗
NASA NTRS1979

Electrical conductivity of the lunar interior - Theory, error sources, and estimates

Estimates of the electrical conductivity of the lunar interior were previously obtained by comparison of magnetometer data at the lunar surface and in near lunar space. In studies based on solar wind observations, IR was assumed that fields induced in the lunar interior by time-varying external fields are confined by the solar wind within the lunar interior on the dayside and within a cylindrical plasma cavity on the nightside. In the present paper, the induced fields are calculated for a more realistic conical plasma cavity geometry.

Goldstein, B. E.↗
NASA NTRS1979

Evaluation of finite element formulations for transient conduction forced-convection analysis

Conventional versus upwind convective finite elements, and lumped versus consistent formulations for practical conduction/forced convection analysis are evaluated on the basis of numerical studies, with finite element and finite difference lumped-parameter temperatures compared to closed-form analytical solutions for convection problems. Attention is given to two practical combined conduction and forced convection applications, stressing that the finite element method, showing superior accuracy, is competitive with the finite difference lumped-parameter method. Also considered are the computational time savings offered by the zero capacitance nodes procedure and comparative finite element and finite difference lumped-parameter computer times. The present study has reference to the design of actively cooled engine and airframe structures for hypersonic flight.

Thornton, E. A.↗
NASA NTRS1979

Qualification of black electrically conductive paint

A paint having low electrical resistance has been developed. Using a low outgassing polyurethane resin, specific amounts of conductive carbon particles were added to produce paint compositions having a range of electrical resistance. Methods of testing for electrical resistance are discussed. The adhesion of these paints has been tested successfully over the temperature range from liquid nitrogen temperature up to 80 C (176 F).

Park, J. J.↗
NASA NTRS1982

Electrically-conductive Low-Permeability Pressure Seal

Metal-plated butyl rubber seal has been devised for enclosures of electronic equipment that must be maintained under dry, inert atmosphere. Seal prevents gas leakage over prolonged periods, while conductivity suppresses electromagnetic emissions from sealed equipment. Seal is formed by depositing aluminum or gold onto molded-in-place butyl rubber gasket and surrounding areas of flange.

Krieg, H. C.↗
NASA NTRS1980

The potential for damage from the accidental release of conductive carbon fibers from aircraft composites

Carbon and graphite fibers are known to be electrically conductive. The rapidly accelerating use of carbon fibers as the reinforcement in filamentary composite materials brought up the possibility of accidental release of carbon fibers from the burning of crashed commercial airliners with carbon composite parts. Such release could conceivably cause widespread damage to electrical and electronic equipment. The experimental and analytical results of a comprehensive investigation of the various elements necessary to assess the extent of such potential damage in terms of annual expected costs and maximum losses at low probabilities of occurrence are presented. A review of NASA materials research program to provide alternate or modified composite materials to overcome any electrical hazards from the use of carbon composites in aircraft structures is described.

Bell, V. L.↗
NASA NTRS1979

Gas release and conductivity modification studies

The behavior of gas clouds produced by releases from orbital velocity in either a point release or venting mode is described by the modification of snowplow equations valid in an intermediate altitude regime. Quantitative estimates are produced for the time dependence of the radius of the cloud, the average internal energy, the translational velocity, and the distance traveled. The dependence of these quantities on the assumed density profile, the internal energy of the gas, and the ratio of specific heats is examined. The new feature is the inclusion of the effect of the large orbital velocity. The resulting gas cloud models are used to calculate the characteristics of the field line integrated Pedersen conductivity enhancements that would be produced by the release of barium thermite at orbital velocity in either the point release or venting modes as a function of release altitude and chemical payload weight.

Linson, L. M.↗
NASA NTRS1981

Exact finite elements for conduction and convection

An approach for developing exact one dimensional conduction-convection finite elements is presented. Exact interpolation functions are derived based on solutions to the governing differential equations by employing a nodeless parameter. Exact interpolation functions are presented for combined heat transfer in several solids of different shapes, and for combined heat transfer in a flow passage. Numerical results demonstrate that exact one dimensional elements offer advantages over elements based on approximate interpolation functions.

Thornton, E. A.↗
NASA NTRS1980

Finite-element analysis of nonlinear conduction problems subject to moving fields

Through the use of a space-time warp, specialized moving finite elements are developed that can be employed to generate a nonlinear heat conduction model for situations involving traveling boundary and heat generation fields superposed on an initial state. To facilitate the solution of the resulting nonlinear finite-element formulation, a multilevel heuristic iterative solution strategy is developed. In order to demonstrate the versatility and accuracy of the moving elements and their associated nonlinear solution strategy, the results of several numerical experiments are presented.

Padovan, J.↗
NASA NTRS1980

On equilibrium states of heated self-gravitating gas clouds cooling by conduction in an external gravitational field

Exact analytic solutions are presented for equilibrium states of a self-gravitating one-dimensional cloud of gas, embedded in an external gravitational field due to a plane of 'stars' being heated at a rate proportional to the local gas density, and cooling by thermal conduction. It is found that the general topology of the solutions is such that the gas density has a minimum on the plane of 'stars', rising to an infinite but integrable peak away from the plane so that the total mass of gas in the cloud is finite. The results may be of interest in investigations of interstellar molecular clouds and of filamentary structures in supernova remnants as well as in the modeling of gas distributions around 'cocoon' protostars.

Lerche, I.↗
NASA NTRS1981

Low thermal conductance rigidizer for reducing torsional oscillations in cryogenic Dewars

A rigidizer, which provides greater rigidity against torsional oscillations, is highly resistant to radial motions, and has low thermal conductivity, has been developed to decrease vibrational levels affecting infrared detectors operated in cryostats (e.g., HD-3L Dewar) in aircraft such as NASA's Kuiper Airborne Observatory. The rigidizer is composed of two triangular elements and an intermediate support structure which joins them at the centers of their sides. The reentrant design provides a long heat path, while the triangular truss structure provides high rigidity in the horizontal plane. The structure is relatively compliant in the vertical direction, a desirable feature since the internal structure of the Dewar contracts as it cools. Rigidity in the vertical direction is provided by the neck tube. The support structure is quite compact. Several variants of the rigidizer have been fabricated, using flat sheets of G-10 fiberglass epoxy in thicknesses between 0.75-1.5 mm for the upper and lower truss assemblies, and either G-10 or stainless steel for the intermediate structure.

Harper, D. A.↗
NASA NTRS1981

Thermal conductivity of partially ionized gas mixtures

A method is proposed for predicting the translational component of the thermal conductivity of partially ionized gas mixtures. It is approximate but simple in form and offers a significant improvement over commonly utilized approximations. It does not require large computer run times nor storage, thus it is suitable for use with complex flow fields and heat transfer calculations. Results for gas mixtures which are representative of the atmosphere of Jupiter, Earth, and Venus are presented and they compare favorably with results from detailed kinetic theory analyses.

Armaly, B. F.↗
NASA NTRS1981

The plasma wake of mesosonic conducting bodies. I - An experimental parametric study of ion focusing by the plasma sheath

The experimental investigation considered is concerned with the deflection of ion streams resulting from the interaction of conducting test bodies with an unmagnetized, mesosonic (supersonic with respect to ions but subsonic with respect to electrons) plasma stream. The investigation is, therefore, limited to plasma-electrostatic interactions. The experimental conditions are similar to those of the spacecraft-ionospheric interaction in that the ionic mass and number density, the electron temperature, and the plasma drift velocity ranges include values appropriate for small satellites or diagnostic probes at 200 to 400 km altitude. The study provides direct observations of deflected ion streams for cylindrical test bodies and gives a detailed description of the effects of the governing, dimensionless parameter ratios obtained from the steady-state, nonmagnetic Maxwell-Vlasov system of equations.

Stone, N. H.↗
NASA NTRS1981

Intraband optical conductivity sigma/omega,T/ of Cu, Ag, and Au - Contribution from electron-electron scattering

The frequency and temperature dependence of the intraband optical conductivity of the noble metals Cu, Ag and Au is measured and contributions of electron-electron scattering are assessed. Optical measurements were performed at temperatures of 77, 295 and 425 K to obtain values of the Drude electron scattering rate with a linear dependence on temperature which may be attributed to electron-phonon scattering, and a quadratic dependence on photon energy, which is suggestive of electron-electron scattering but is a factor of two to three times greater than would be expected. Comparison of the optical data with dc electrical and thermal resistivity data which also show behavior attributed to electron-electron scattering reveals discrepancies of up to an order of magnitude. Other possible mechanisms for the frequency dependence, including absorptance, electron-surface plasmon interactions, a two-carrier model, and a structure dependence are considered, and it is concluded that the frequency dependence in the Drude scattering rates of the noble metals is not yet quantitatively understood

Parkins, G. R.↗
NASA NTRS1981

Small conductive particle sensor

An electrostatic conductive fiber detector is disclosed for use in detecting, counting and measuring the length of fibers down to 0.1 mm and below with increased accuracy and reliability over prior art devices. It can be used for detection of fibers suspending in a flowing gas, in a nonflowing gas, or in a vacuum and its accumulated counts over a period of time is essentially unaffected by velocity of the fibers being detected.

Taback, I.↗
NASA NTRS1981

Contributions of orbital mechanics to conducting experiments in space

Orbital mechanics as a discipline is principally concerned with solving the set of equations for analyzing the motion of a satellite under various conditions. This activity on the surface may not seem crucial to conducting experiments in space, but it provides insights into the way in which forces may influence these experiments. More directly, for experiments concerned with external targets, it provides predictions of the satellites's position and velcoity verus time, enabling extensive preflight planning and resulting in optimum use of on-orbit time.

Mullins, L. D.↗