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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 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Turbulent disruptions from the Strauss equations

Preliminary results are reported from application of a three-dimensional spectral method model to the solution of the Strauss (1976) reduced MHD equations. The investigation was focused on describing MHD turbulence in a current-carrying bounded magnetofluid. A cylindrical geometry with a square cross-section was considered, with the walls being rigid perfect conductors with free-slip boundary conditions. A uniform magnetic field and the electric current density both point in the z-direction. Initial conditions are specified which feature small amounts of random noise expressed as Fourier modes. Linearized equations are defined for tracing the movement to equlibrium conditions or other temporal development. The model is further refined with nonlinear equations to examine the effects of the appearance of disruptions. Comparisons are drawn between solutions obtained with linear and nonlinear equations, with an eye to the associated physical realities.

Dahlburg, J. P.↗
NASA NTRS1986

Four-micron period ion-implanted bubble test circuits

Packaged magnetic bubble test circuits made with 4-micron period ion-implanted circuits were operated over -55 to +110 C. The circuits used bidirectional transfer and nondestructive detection and were made on bismuth-containing magnetic garnet films. Passivated circuits that incorporated an improved transfer conductor design were operated on films with higher Gilbert damping parameters. Potential advantages to using films with lower bubble aspect ratios for ion-implanted circuits are discussed. However nondestructive read-out detection was not realized with these 'flat' bubbles.

Nelson, T. J.↗
NASA NTRS1987

Radial/Axial Microwave Power Divider/Combiner

Parts made on printed-circuit boards. Impedance-matching and power-dividing transmission-line strips formed on insulation disks and on board by printed-circuit techniques. Power from input transmission line sent equally through radial output conductors to radial output transmission lines and/or coupled in varying degrees to axial output transmission line.

Vaddiparty, Verriah P.↗
NASA NTRS1987

Electromagnetic Repulsive Deicer for Aircraft

Scheme for removing ice from airfoils in flight adds little weight and demands relatively small amount of energy. Employing electromagnetic repulsion of conductors embedded in rubber covering on airfoil, scheme breaks up layer of ice by snapping it in manner of snapping rug to remove dust. Layer of elastomer conforms to shape of airfoil in relaxed state. When carrying large electrical currents, conductive ribbons in elastomer repel each other, creating ridged surface on airfoil. Sheet of ice on airfoil broken up in sudden transition from relaxed state to energized state.

Haslim, Leonard A.↗
NASA NTRS1986

A study of reactive plasma deposited thin films

A state-of-the-art research laboratory was established to grow and characterize amorphous thin films that are useful in semi-conductor devices. Two film systems, nitride films and silicon dioxide films were studied. Over seventy deposition runs for nitride films were made. The films were deposited on silicon substrate using plasma enhanced chemical vapor deposition. It was found that the uniformity of the films were affected by the location of the film on the platen.

Gilchrist, J.↗
NASA NTRS1986

The barium iron ruthenium oxide system

In the system BaFe(1-x)Ru(x)O(3-y), three phases, separated by immiscibility gaps, are present: an Fe-rich phase (x = 0 to 0.75) with hexagonal BaTiO3 structure (6H; sequence (hcc)2), a Ru-rich phase (x = 0.9) of hexagonal 4H-type (sequence (hc)2), and the pure Ru compounds BaRuO3 with rhombohedral 9R structure (sequence (hhc)3). By vibrational spectroscopic investigations in the 6H phase a transition from n-type semiconduction (Fe-rich compounds with complete O lattice) can be detected. The 4H and 9R stacking polytypes are good, metal-like conductors. The lattice parameters are given.

Kemmler-Sack, S.↗
NASA NTRS1987

Containerless high temperature property measurements by atomic fluorescence

Containerless high temperature processing and material property measurements are discussed. Researchers developed methods for non-contact suspension, heating, and property measurement for materials at temperatures up to 3,680K, the melting point of tungsten. New, scientifically interesting results were obtained in Earth-based research. These results and the demonstration of new methods and techniques form a basis for further advances under the low gravity environment of space where containerless conditions are more easily achieved. Containerless high temperature material property investigations that have been completed in this and our earlier projects include measurements of fluorine LaB sub 6 reaction kinetics at 1,000 to 1,500K; optical property measurements on sapphire (Al2O3) at temperatures up to the melting point (2,327K); and vapor pressure measurements for LaB sub 6 at 2,000 to 2,500K, for molybdenum up to 2,890K and for tungsten up to 3,680K. Gas jet levitation which is applicable to any solid material, and electromagnetic levitation of electrical conductors were used to suspend the materials of interest. Non-contact heating and property measurements were achieved by optical techniques, i.e., laser heating, laser induced fluorescence measurements of vapor concentrations, and optical pyrometry for specimen temperatures.

Nordine, Paul C.↗
NASA NTRS1987

Coaxial tube array space transmission line characterization

The coaxial tube array tether/transmission line used to connect an SP-100 nuclear power system to the space station was characterized over the range of reactor-to-platform separation distances of 1 to 10 km. Characterization was done with respect to array performance, physical dimensions and masses. Using a fixed design procedure, a family of designs was generated for the same power level (300 kWe), power loss (1.5 percent), and meteoroid survival probability (99.5 percent over 10 yr). To differentiate between vacuum insulated and gas insulated lines, two different maximum values of the E field were considered: 20 kV/cm (appropriate to vacuum insulation) and 50 kV/cm (compressed SF6). Core conductor, tube, bumper, standoff, spacer and bumper support dimensions, and masses were also calculated. The results of the characterization show mainly how transmission line size and mass scale with reactor-to-platform separation distance.

Switzer, Colleen A.↗
NASA NTRS1987

Method and means for generation of tunable laser sidebands in the far-infrared region

A method for generating tunable far-infrared radiation is described. The apparatus includes a Schottky-barrier diode which has one side coupled through a conductor to a waveguide that carries a tunable microwave frequency; the diode has an opposite side which is coupled through a radiating whisker to a bias source. Infrared light is directed at the diode, and infrared light with tunable sidebands is radiated by the whisker through an open space to a reflector. The original infrared is separated from a tunable infrared sideband by a polarizing Michelson interferometer.

Pickett, Herbert M.↗
NASA NTRS1987

Measurement of opaque film thickness

The theoretical and experimental framework for thickness measurements of thin metal films by low frequency thermal waves is described. Although it is assumed that the films are opaque and the substrates are comparatively poor thermal conductors, the theory is easily extended to other cases of technological interest. A brief description is given of the thermal waves and the experimental arrangement and parameters. The usefulness of the technique is illustrated for making absolute measurements of the thermal diffusivities of isotropic substrate materials. This measurement on pure elemental solids provides a check on the three dimensional theory in the limiting case of zero film thickness. The theoretical framework is then presented, along with numerical calculations and corresponding experimental results for the case of copper films on a glass substrate.

Thomas, R. L.↗
NASA NTRS1987

Polyphase alloys as rechargeable electrodes in advanced battery systems

The rechargeability of electrochemical cells is often limited by negative electrode problems. These may include loss of capacity, increased impedance, macroscopic shape change, dendrite growth, or a tendency for filamentary or whisker growth. In principle, these problems can be reduced or eliminated by the use of alloys that undergo either displacement or insertion reactions at reactant species activities less than unity, rather than pure elements. The fundamental reasons for some of these problems with elemental electrodes, as well as the basic principles involved in the different behavior of alloys, are briefly discussed. More information is now available concerning the thermodynamic and kinetic properties of a number of alloys of potential interest for use as electrodes in elevated temperature lithium battery systems. Recent results have extended these results down to ambient temperatures, indicating that some such materials may be of interest for use with new low temperature molten salt electrolytes, or with organic solvent electrolytes. The all solid mixed conductor matrix concept is also reviewed.

Huggins, Robert A.↗
NASA NTRS1987

Advances in solid polymer electrolyte fuel cell technology with low-platinum-loading electrodes

The Gemini Space program demonstrated the first major application of fuel cell systems. Solid polymer electrolyte fuel cells were used as auxiliary power sources in the spacecraft. There has been considerable progress in this technology since then, particularly with the substitution of Nafion for the polystyrene sulfonate membrane as the electrolyte. Until recently the performance was good only with high platinum loading (4 mg/sq cm) electrodes. Methods are presented to advance the technology by (1) use of low platinum loading (0.35 mg/sq cm) electrodes; (2) optimization of anode/membrane/cathode interfaces by hot pressing; (3) pressurization of reactant gases, which is most important when air is used as cathodic reactant; and (4) adequate humidification of reactant gases to overcome the water management problem. The high performance of the fuel cell with the low loading of platinum appears to be due to the extension of the three dimensional reaction zone by introduction of a proton conductor, Nafion. This was confirmed by cyclic voltammetry.

Srinivasan, Supramaniam↗
NASA NTRS1986

The split-cross-bridge resistor for measuring the sheet resistance, linewidth, and line spacing of conducting layers

A new test structure was developed for evaluating the line spacing between conductors on the same layer using an electrical measurement technique. This compact structure can also be used to measure the sheet resistance, linewidth, and line pitch of the conducting layer. Using an integrated-circuit fabrication process, this structure was fabricated in diffused polycrystalline silicon and metal layers and measured optically and electrically. For the techniques used, the optical measurements were typically one-quarter micron greater than the electrical measurements. Most electrically measured line pitch values were within 2 percent of the designed value. A small difference between the measured and designed line pitch is used to validate sheet resistance, linewidth, and line spacing values.

Buehler, M. G.↗
NASA NTRS1985

Self-structured, current aperture approach for bubble memory

An approach to magnetic bubble memory which incorporates dual conductor current access drive with a self-structured (strongly interacting) bubble lattice is described. This is expected to provide higher operating speeds, defect tolerance, and higher bit density for a given bubble size as compared to present field access bubble devices. Bubble spacings of 2.5 bubble diameters are projected for a prototype device. Experimental work on device components including detectors, major/minor loops, and gates is described. Defect tolerance has also been demonstrated.

Nelson, G. L.↗
NASA NTRS1986

dc electric field meter with fiber-optic readout

The design of a dc electric field meter capable of measuring the magnitude and direction of the electric field at an arbitrary location above the ground plane is described. The meter is based on measuring induced charge on a split cylindrical electrode pair which is rotated around its axis of symmetry. Data readout is by fiber-optic cable using pulse frequency encoding. The sensing head is electrically isolated. Initial results are reported from a series of tests at General Electric's High Voltage Transmission Research Facility, Pittsfield, MA. The electric field was measured in a large test cage and under a dc test line. Measurement of field magnitude and direction around a human subject standing under the conductor was demonstrated.

Johnston, Alan R.↗
NASA NTRS1986

Hybrid analog/digital, large format, photon counting detectors for astronomy

The development of a new microchannel plate photon-counting detector with an analog readout method based on a resistive anode is reported. This detector exhibits extremely high, stable electron gains of 10 to the 8th. At this gain, the spatial resolution is no longer primarily limited by the noise of the resistive anode, so that digital methods of readout, such as discrete conductors, lose their advantage. These detectors can be readily scaled to 40 mm and 70 mm formats to match plate scales of 2-m (and larger) telescopes. New, high speed digital electronics fully exploit the high spatial and time resolution made possible by gains of this level. Analysis of the theoretical performance of this detector shows that the major limitation to the spatial resolution is the proximity focus of the photocathode and the first microchannel plate. The detector has been mated to an echelle spectrograph developed.

Crocker, J.↗
NASA NTRS1988

Flexible Ceramic-Insulated Cable

Cable withstands heat, radiation, and oxidation. Ceramic beads electrically insulate copper conductor from sheath of copper tape. Also suitable for furnaces, nuclear reactors, and robots operating in hot, radioactive environments.

Bouquet, Frank L.↗
NASA NTRS1987

Coaxial cable connector

A coaxial cable connector is provided, which resists radio frequency breakdown in coaxial cables used in the vacuum of outer space. The connector body surrounds an insulator which includes an easily compressible elastomeric portion. An insulated coaxial cable is prepared so that its insulation projects beyond the outer conductor and compresses the elastomeric portion of the connector insulator.

Caro, Edward R.↗