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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 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Work function measurement of lanthanum-boron compounds

The relationship between emission properties and sample composition is studied for lanthanum-boron compounds. Specifically, the La-B system is considered between 1400 and 2100 K and between LaB(4.24) and LaB(29.2) to determine the phase relationship, chemical activity of the compounds, vapor composition, and vaporization rate. The results indicate that: (1) a blue-colored phase near LaB(9) exists between a purple-colored LaB(6) and elemental boron, (2) vaporization is sufficiently more rapid than diffusion so that great compositional differences exist between the surface and the interior, (3) an activation energy lowers the boron vaporization rate from LaB(6), and (4) a steady-state surface composition between LaB(6.04) and LaB(6.07) exists for freely vaporizing materials as a function of interior composition, purity, and temperature. It is noted that the ultimate life of a thermionic diode is governed by electrode vaporization rate whereas efficiency is governed by the electrode work function.

Jacobson, D. L.↗
NASA NTRS1978

Electron emission from nickel-alloy surfaces in cesium vapor

The cesiated electron emission was measured for three candidate electrodes for use as collectors in thermionic converters. Nickel, Inconel 600 and Hastelloy were tested with a 412 K cesium reservoir. Peak emission from the alloys was found to be comparable to that from pure nickel. Both the Inconel and the Hastelloy samples had work functions of 1.64 eV at peak emission. The minimum work functions were estimated to be 1.37 eV at a probe temperature of 750 K for Inconel and 1.40 eV for Hastelloy at 665 K. The bare work function for both alloys is estimated to be approximately the same as for pure nickel, 4.8 eV.

Manda, M.↗
NASA NTRS1978

Investigations of negative and positive cesium ion species

A direct test is provided of the hypothesis of negative ion creation at the anode or collector of a diode operating under conditions simulating a cesium thermionic converter. The experimental technique involves using direct ion sampling through the collector electrode with mass analysis using a quadrupole mass analyzer. Similar measurements are undertaken on positive ions extracted through the emitter electrode. Measurements were made on a variety of gases including pure cesium, helium-cesium mixtures and cesium-hydrogen as well as cesium-xenon mixtures. The gas additive was used primarily to aid in understanding the negative ion formation processes. Measurements were conducted using emitter (cathode) temperatures up to about 1000 F. The major negative ion identified through the collector was Cs(-) with minor negative ion peaks tentatively identified as H(-), H2(-), H3(-), He(-) and a mass 66. Positive ions detected were believed to be Cs(+), Cs2(+) and Cs3(+).

Chanin, L. M.↗
NASA NTRS1977

The 25 kN space station

The capabilities of photovoltaic, nuclear reactor, and solar thermal systems are assessed for the space construction base. Topics covered include Brayton conversion, thermionic conversion, and thermo-electric conversion. The effectiveness of nickel cadmium and nickel hydrogen batteries are discussed as well as that of regenerative fuel cells. The verification of long cycle life for nickel hydrogen systems is recommended.

Clark, B.↗
NASA NTRS1979

Solar thermal power generation. A bibliography with abstracts

Bibliographies and abstracts are cited under the following topics: (1) energy overviews; (2) solar overviews; (3) conservation; (4) economics, law; (5) thermal power; (6) thermionic, thermoelectric; (7) ocean; (8) wind power; (9) biomass and photochemical; and (10) large photovoltaics.

Source record↗
NASA NTRS1979

Summary of the two year NASA program for active control of ATS-5/6 environmental charging

Experiments conducted on the ATS 5 and ATS 6 which have demonstrated the feasibility of modifying or clamping the environmentally induced potential of these spacecraft are described. The results of these experiments indicate that a thermionic electron source is capable of replacing photo-emitted electrons during eclipse. However, the utility of this type of device is limited if its emission is suppressed by local electric fields. On the other hand, it is shown that a plasma source will not only serve as a substitute for photo-emitted electrons but will also suppress differential charging of isolated elements of the spacecraft which would tend to suppress electron emission. This later device is therefore capable of clamping the potential of a spacecraft without special considerations of its coupling to the ambient plasma.

Bartlett, R. O.↗
NASA NTRS1979

Benefits of advanced technology in industrial cogeneration

This broad study is aimed at identifying the most attractive advanced energy conversion systems for industrial cogeneration for the 1985 to 2000 time period and assessing the advantages of advanced technology systems compared to using today's commercially available technology. Energy conversion systems being studied include those using steam turbines, open cycle gas turbines, combined cycles, diesel engines, Stirling engines, closed cycle gas turbines, phosphoric acid and molten carbonate fuel cells and thermionics. Specific cases using today's commercially available technology are being included to serve as a baseline for assessing the advantages of advanced technology.

Barna, G. J.↗
NASA NTRS1979

Energy and cost saving results for advanced technology systems from the Cogeneration Technology Alternatives Study (CTAS)

An overview of the organization and methodology of the Cogeneration Technology Alternatives Study is presented. The objectives of the study were to identify the most attractive advanced energy conversion systems for industrial cogeneration applications in the future and to assess the advantages of advanced technology systems compared to those systems commercially available today. Advanced systems studied include steam turbines, open and closed cycle gas turbines, combined cycles, diesel engines, Stirling engines, phosphoric acid and molten carbonate fuel cells and thermionics. Steam turbines, open cycle gas turbines, combined cycles, and diesel engines were also analyzed in versions typical of today's commercially available technology to provide a base against which to measure the advanced systems. Cogeneration applications in the major energy consuming manufacturing industries were considered. Results of the study in terms of plant level energy savings, annual energy cost savings and economic attractiveness are presented for the various energy conversion systems considered.

Sagerman, G. D.↗
NASA NTRS1978

Future thrusts of the NASA space power program

General objectives and plan directions are given for current program support in the following areas: (1) solar cells and arrays; (2) batteries and fuel cells; (3) thermoelectric, thermionic, and Brayton cycle conversion systems; (4) circuits and subsystems for the management and distribution of power; and (5) the interactions of the environment with the power system and the spacecraft. Particular emphasis is given to the electrochemical energy conversion storage portion of the program where efforts are directed to improving the energy density and life of nickel cadmium batteries, to validating flight-weight silver hydrogen cells, to promoting the safe use of lithium primary batteries, to completing the silver zinc batteries and the orbital transfer fuel cell technology, to increasing the capacity of space batteries, to and to evaluating new electrochemical concepts for very high energy density. The use of the fuel cell electrolyzer concept for energy storage in both the dedicated and the truly regenerative mode is also being investigated.

Holcomb, L.↗
NASA NTRS1978

A search for space energy alternatives

This paper takes a look at a number of schemes for converting radiant energy in space to useful energy for man. These schemes are possible alternatives to the currently most studied solar power satellite concept. Possible primary collection and conversion devices discussed include the space particle flux devices, solar windmills, photovoltaic devices, photochemical cells, photoemissive converters, heat engines, dielectric energy conversion, electrostatic generators, plasma solar collectors, and thermionic schemes. Transmission devices reviewed include lasers and masers.

Gilbreath, W. P.↗
NASA NTRS1978

Negative and positive cesium ion studies

Mass spectrometric analyses have been performed on the positive and negative species from discharges in Cs, He-Cs, and He-H2-Cs mixtures. Sampling was conducted through the electrodes of normal glow discharges and from close-spaced heated-cathode conditions, which approximate a cesium thermionic converter. No negative Cs ions were observed for Cs pressures less than .01 torr. Identified species included Cs(+), Cs2(+), Cs(-), and what appeared to be multiply charged ions. Low-mass negative and positive ions attributed to H2 were observed when an He-H2 mixture was also present in the discharge region.

Kuehn, D. G.↗
NASA NTRS1979

Geometries and focal properties of two electron-lens systems useful in low-energy electron or ion scattering

Geometries and focal properties are given for two types of electron-lens system commonly needed in electron scattering. One is an electron gun that focuses electrons from a thermionic emitter onto a fixed point (target) over a wide range of final energies. The other is an electron analyzer system that focuses scattered electrons of variable energy onto a fixed position (e.g., the entrance plane of an analyzer) at fixed energy with a zero final beam angle. Analyzer-system focusing properties are given for superelastically, elastically, and inelastically scattered electrons. Computer calculations incorporating recent accurate tube-lens focal properties are used to compute lens voltages, locations and diameters of all pupils and windows, filling factors, and asymptotic rays throughout each lens system. Focus voltages as a function of electron energy and energy change are given, and limits of operation of each system discussed. Both lens systems have been in routine use for several years, and good agreement has been consistently found between calculated and operating lens voltages.

Chutjian, A.↗
NASA NTRS1979

Transport of majority and minority carriers in 2-micron-diameter Pt-GaAs Schottky barriers

An experimental study of small area (2-micron diameter) Pt-GaAs Schottky barrier diodes has been made, by using a wafer chip with a matrix of these diodes lying within approximately a minority carrier diffusion length of one another. Using one diode as collector and another as emitter, transistor measurements indicated that the dominant contribution to the current is the majority-carrier thermionic field emission current for large forward-bias voltage of the emitter junction (V-EB no less than about 0.4 V), whereas the smaller forward-bias (V-EB no greater than about 0.4 V) recombination in the space-charge region was most important. The minority carrier injection ratio is measurable only for large forward-bias voltages, decreasing from about 0.02 to 0.00001 as VEB increases from 0.5 to 1.0 V. The minority carrier diffusion length was measured to be about 1.3 microns. These results are of considerable significance for the understanding and optimization of the performance of these devices as classical detectors and mixers.

Chan, E. Y.↗
NASA NTRS1979

Energy and cost savings results for advanced technology systems from the Cogeneration Technology Alternatives Study /CTAS/

The Cogeneration Technology Alternatives Study (CTAS), a program undertaken to identify the most attractive advanced energy conversion systems for industrial cogeneration applications in the 1985-2000 time period, is described, and preliminary results are presented. Two cogeneration options are included in the analysis: a topping application, in which fuel is input to the energy conversion system which generates electricity and waste heat from the conversion system is used to provide heat to the process, and a bottoming application, in which fuel is burned to provide high temperature process heat and waste heat from the process is used as thermal input to the energy conversion system which generates energy. Steam turbines, open and closed cycle gas turbines, combined cycles, diesel engines, Stirling engines, phosphoric acid and molten carbonate fuel cells and thermionics are examined. Expected plant level energy savings, annual energy cost savings, and other results of the economic analysis are given, and the sensitivity of these results to the assumptions concerning fuel prices, price of purchased electricity and the potential effects of regional energy use characteristics is discussed.

Sagerman, G. D.↗
NASA NTRS1979

Reactor design for nuclear electric propulsion

The paper analyzes the consequences of heat pipe failures, that resulted in modifications to the basic design of a heat-pipe cooled, fast spectrum nuclear reactor and led to consideration of an entirely different core design. The new design features an integral laminated core configuration consisting of alternating layers of UO2 and molybdenum sheets that span the diameter of the core. Design characteristics are presented and compared for two reactors. A conceptual design for a heat exchanger between the core and the thermionic converter assembly is described. This heat exchanger would provide design and fabrication decoupling of these two assemblies.

Koenig, D. R.↗
NASA NTRS1979

Low cost cylindrical converter for measuring lead efficiency

A low cost cylindrical thermionic converter has been designed, fabricated, and tested for use in a NASA-JPL program to directly measure converter lead efficiencies using various electrode materials and surfaces. Efficiency measurements are made using input emitter heater power, output power at the leads, and calculated values of the parasitic losses that would not be present in the application configuration. This information can be used to predict the performance characteristics of the advanced converters currently under development. A series of five converters has been tested. Both structured and smooth molybdenum collectors have been used. Emitters included smooth molybdenum, smooth rhenium, and microstructured rhenium. Cesium pressure families of current-voltage curves are presented for emitter temperatures of 1600, 1700, and 1800 K, along with measured efficiencies as a function of converter current densities for each temperature.

Hatch, G. L.↗
NASA NTRS1980

Simple buck/boost voltage regulator

Circuit corrects low or high supply voltage, produces regulated output voltage. Circuit has fewer components because inductory/transformer combination and pulse-width modulator serve double duty. Regulator handles input voltage variation from as low as one half output voltage to as high as input transistor rating. Solar arrays, fuel cells, and thermionic generators might use this regulator.

Paulkovich, J.↗
NASA NTRS1979

Analysis of S-band solid-state transmitters for the solar power satellite

The possibility of replacing the Reference System antenna in which thermionic devices are used for the dc-to-microwave conversion, with solid-state elements was explored. System, device, and antenna module tradeoff investigations strongly point toward the desirability of changing the transmitter concept to a distributed array of relatively low power elements, deriving their dc power directly from the solar cell array and whose microwave power outputs are combined in space. The approach eliminates the thermal, weight, and dc-voltage distribution problems of a system in which high power tubes are simply replaced with clusters of solid state amplifiers. The proposed approach retains the important advantages of a solid state system: greatly enhanced reliability and graceful degradation of the system.

Belohoubek, E. F.↗