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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 1,531 records · Page 85

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NASA NTRS1976

Characteristics of corona impulses from insulated wires subjected to high ac voltages

Corona discharges arise due to ionization of air or gas subject to high electric fields. The free electrons and ions contained in these discharges interact with molecules of insulating materials, resulting in chemical changes and destroying the electrical insulating properties. The paper describes some results of measurements aimed at determining corona pulse waveforms, their repetition rate, and amplitude distribution during various randomly-sampled identical time periods of a 60-Hz high-voltage wave. Described are properties of positive and negative corona impulses generated from typical conductors at various test high voltages. A possible method for calculating the energies, densities, and electromagnetic interferences by making use of these results is suggested.

Doreswamy, C. V.↗

NASA NTRS1976

Photovoltaic cell array

A photovoltaic cell array consisting of parallel columns of silicon filaments is described. Each fiber is doped to produce an inner region of one polarity type and an outer region of an opposite polarity type to thereby form a continuous radial semi conductor junction. Spaced rows of electrical contacts alternately connect to the inner and outer regions to provide a plurality of electrical outputs which may be combined in parallel or in series.

Eliason, J. T.↗

NASA NTRS1976

Design study of steady-state 30-tesla liquid-neon-cooled magnet

A design for a 30-tesla, liquid-neon-cooled magnet was reported which is capable of continuous operation. Cooled by nonboiling, forced-convection heat transfer to liquid neon flowing at 2.8 cu m/min in a closed, pressurized heat-transfer loop and structurally supported by a tapered structural ribbon, the tape-wound coils with a high-purity-aluminum conductor will produce over 30 teslas for 1 minute at 850 kilowatts. The magnet will have an inside diameter of 7.5 centimeters and an outside diameter of 54 centimeters. The minimum current density at design field will be 15.7 kA/sq cm.

Prok, G. M.↗

NASA NTRS1976

Discrete component bonding and thick film materials study

The bonding reliability of discrete capacitor chips bonded with solders and conductive epoxies was examined along with the thick film resistor materials consisting of iron oxide phosphate and vanadium oxide phosphates. It was concluded from the bonding reliability studies that none of the wide range of types of solders examined is capable of resisting failure during thermal cycling while the conductive epoxy gives substantially lower failure rates. The thick film resistor studies proved the feasibility of iron oxide phosphate resistor systems although some environmental sensitivity problems remain. One of these resistor compositions has inadvertently proven to be a candidate for thermistor applications because of the excellent control achieved upon the temperature coefficient of resistance. One new and potentially damaging phenomenon observed was the degradation of thick film conductors during the course of thermal cycling.

Kinser, D. L.↗

NASA NTRS1977

Thick-film materials for silicon photovoltaic cell manufacture

Thick film technology is applicable to three areas of silicon solar cell fabrication; metallization, junction formation, and coating for protection of screened ohmic contacts, particularly wrap around contacts, interconnection and environmental protection. Both material and process parameters were investigated. Printed ohmic contacts on n- and p-type silicon are very sensitive to the processing parameters of firing time, temperature, and atmosphere. Wrap around contacts are easily achieved by first printing and firing a dielectric over the edge and subsequently applying a low firing temperature conductor. Interconnection of cells into arrays can be achieved by printing and cofiring thick film metal pastes, soldering, or with heat curing conductive epoxies on low cost substrates. Printed (thick) film vitreous protection coatings do not yet offer sufficient optical uniformity and transparency for use on silicon. A sprayed, heat curable SiO2 based resin shows promise of providing both optical matching and environmental protection.

Field, M. B.↗

NASA NTRS1977

Magnetic electrical connectors for biomedical percutaneous implants

A biomedical percutaneous connector is described which includes a socket having an enlarged disk shaped base portion for being implanted below the patient's skin and cylindrical portion which is integral with the base portion and extends outwardly of the skin. A conical recess in an upper end of the cylindrical portion has a magnet located in the base. Inclined conductive strips are carried on an upper end of the cylindrical portion to which electrical conductors are attached and extend into the patient's body. A complementary shaped plug which also has electrical contacts provided thereon is adapted to fit within the conical recess of the socket. The plug is held in the socket by magnetic force.

Owens, L. J.↗

NASA NTRS1975

Urban construction and safety project

The purpose and functions of NASA technology applications temas (TAT) are described, with emphasis on the activities of the Urban and Construction and Safety Project. The transfer and implementation of technology is discussed in five activities. Topics include: flat conductor cable, NASA house and compendium, flood insurance studies, tornado studies, and the controller for stationary diesels.

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NASA NTRS1976

Theoretical analysis of the EWEC report

This analytic investigation shows how the electromagnetic wave energy conversion (EWEC) device, as used for solar-to-electric power conversion, is significantly different from solar cells, with respect to principles of operation. An optimistic estimate of efficiency is about 80% for a full-wave rectifying configuration with solar radiation normally incident. This compares favorably with the theoretical maximum for a CdTe solar cell (23.5%), as well as with the efficiencies of more familiar cells: Si (19.5%), InP (21.5%), and GaAs (23%). Some key technological issues that must be resolved before the EWEC device can be realized are identified. Those issues include: the fabrication of a pn semi-conductor junction with no permittivity resonances in the optical band; and the efficient channeling of the power received by countless microscopic horn antennas through a relatively few number of wires.

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NASA NTRS1977

Polymeric membrane systems of potential use for battery separators

Two membrane systems were investigated that may have potential use as alkaline battery separators. One system comprises two miscible polymers: a support polymer (e.g., polyvinyl formal) and an ion conductor such as polyacrylic acid. The other system involves a film composed of two immiscible polymers: a conducting polymer (e.g., calcium polyacrylate) suspended in an inert polymer support matrix, polyphenylene oxide. Resistivities in 45-percent potassium hydroxide and qualitative mechanical properties are presented for films comprising various proportions of conducting and support polymers. In terms of these parameters, the results are encouraging for optimum ratios of conducting to support polymers.

Philipp, W. H.↗

NASA NTRS1977

Charged-particle absorption by Io

The electrostatic field associated with the rotation of Jupiter, relative to the rest frame of Io, would be distorted if the satellite were an electrical conductor. An idealized two-dimensional model of the distorted electric-field configuration, in the limit of a perfectly conducting satellite or satellite ionosphere, has been constructed and used to trace the adiabatic guiding-center trajectories of energetic protons and electrons across Jupiter's magnetic field lines, which are taken as rectilinear. The adiabatic trajectories of very low-energy particles (cold plasma) are found to avoid the satellite and escape absorption. In the limit of very high particle energies, the adiabatic trajectories are undistorted, and absorption proceeds as if Io were an insulator. The interpolation between these limits is monotonic for protons, such that Io sweeps out a drift shell half as wide as the satellite for first invariants of the order of 1 GeV per gauss. The situation for electrons is more complicated, and no absorption from adiabatic trajectories is found at first invariants not exceeding 46 GeV per gauss. Electrons having first invariants of at least 50 GeV per gauss are typically swept out of drift shells wider than the satellite itself. However, electrons can impact only a portion of Io's exposed hemisphere for first invariants of 50-200 GeV per gauss. Thus, the particle-absorbing characteristics of an electrically conducting Jovian satellite are found to depend on both the species and the energy of the incident particle, and the satellite's particle-absorbing cross section differs systematically from its geometric cross section.

Schulz, M.↗

NASA NTRS1978

Laser wire stripping

Bench-mounted and hand-held laser units cut insulation from wires without nipping or scraping conductor. Process eliminates quality control problems and is fast, clean, precise, and repeatable.

Heisman, R. M.↗

NASA NTRS1978

High-power RF switch

Switch designed for vacuum environments can handle 5 kilowatts of microwave power. Arcing between conductors is prevented by filling gaps with Teflon rather than with inert gas as in conventional switches. Thus, switch is not susceptible to gas leakage, problem faced by conventional switches in high-vacuum applications. Compact three-port switch, developed for microwave radar transmitters aboard spacecraft, is operated by depressing spring-mounted insulating pins that can be remotely actuated by relay. When pin is depressed, it routes microwave signals to selected output port.

Caro, E. R.↗

NASA NTRS1979

Splicing shielded cables

Simple repair technique retains cable characteristic impedance. Shielded-Cable Splicing Technique retains cable characteristic impedance. Procedure involves splicing inner conductors in staggered pattern, installing jumper braid by heat-shrinking two solder sleeves, and placing insulation sleeve over repaired section and heat-shrinking it. Two possible insulation materials are modified polyvinylidene fluoride and polytetrafluoroethylene.

Lind, W. P.↗

NASA NTRS1979

Low partial discharge vacuum feedthrough

Relatively discharge free vacuum feedthrough uses silver-plated copper conductor jacketed by carbon filled silicon semiconductor to reduce concentrated electric fields and minimize occurrence of partial discharge.

Benham, J. W.↗

NASA NTRS1977

Sail GTS ground system analysis: Avionics system engineering

A comparison of two different concepts for the guidance, navigation and control test set signal ground system is presented. The first is a concept utilizing a ground plate to which crew station, avionics racks, electrical power distribution system, master electrical common connection assembly and marshall mated elements system grounds are connected by 4/0 welding cable. An alternate approach has an aluminum sheet interconnecting the signal ground reference points between the crew station and avionics racks. The comparison analysis quantifies the differences between the two concepts in terms of dc resistance, ac resistance and inductive reactance. These parameters are figures of merit for ground system conductors in that the system with the lowest impedance is the most effective in minimizing noise voltage. Although the welding cable system is probably adequate, the aluminum sheet system provides a higher probability of a successful system design.

Lawton, R. M.↗

NASA NTRS1977

Voltages and currents induced on wiring

Aircraft lightning strikes were investigated in regard to their effects on voltages and currents in aircraft wiring. An electrical conductor's response to magnetic fields and electric fields was examined as part of the voltage and current calculations. The wiring system of the space shuttle was briefly considered as an example.

Franklin A Fisher↗

NASA NTRS1977

Effects of shields on cables

Aircraft wiring subjected to rapidly changing electromagnetic fields was considered. The ways in which shielded cables reduce surge voltages were studied along with the ways in which common practice regarding the use of shields may be at variance with the use required for the control of lightning effects. Courses in which this apparent conflict of use may be resolved were suggested. Noise currents flowing on shields of cables related to the noise signals coupled onto signal conductors were also investigated.

Franklin A Fisher↗

NASA NTRS1977

CAVE: A computer code for two-dimensional transient heating analysis of conceptual thermal protection systems for hypersonic vehicles

A digital computer code CAVE (Conduction Analysis Via Eigenvalues), which finds application in the analysis of two dimensional transient heating of hypersonic vehicles is described. The CAVE is written in FORTRAN 4 and is operational on both IBM 360-67 and CDC 6600 computers. The method of solution is a hybrid analytical numerical technique that is inherently stable permitting large time steps even with the best of conductors having the finest of mesh size. The aerodynamic heating boundary conditions are calculated by the code based on the input flight trajectory or can optionally be calculated external to the code and then entered as input data. The code computes the network conduction and convection links, as well as capacitance values, given basic geometrical and mesh sizes, for four generations (leading edges, cooled panels, X-24C structure and slabs). Input and output formats are presented and explained. Sample problems are included. A brief summary of the hybrid analytical-numerical technique, which utilizes eigenvalues (thermal frequencies) and eigenvectors (thermal mode vectors) is given along with aerodynamic heating equations that have been incorporated in the code and flow charts.

Rathjen, K. A.↗