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Proceedings Paper

Oscillating Thermionic Conversion For High-Density Space Power
Author(s): Dean L. Jacobson; James F. Morris
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Paper Abstract

Space nuclear reactors adapt admirably to compact maneuverable multimegawatt power generation. The compactness, maneuverability and productive weight utilization benefit from the use of thermionic converters at high temperatures. These modular static generators reduce waste-heat-radiator weights which loom large in high-power space systems. But greater space-power levels test even thermionic conversion because of its high current densities at low voltages: Relatively low-temperature power conditioning also contributes to large waste-heat-radiator weights. Therefore electromagnetic-wave outputs from thermionic conversion offer important advantages over its traditional direct-current power. In this advantageous operating mode thermionic-conversion lasing yet occupies a theoretic niche. Pulsing and switching with triode thermionic converters appear ready for development guided by continuing applied research. And power-producing thermionic-diode oscillators are excellent prospects for United States research exploitation. This direct thermal power oscillator continues to receive intense experimental and theoretical attention in the USSR--under the aegis of the State Committee for Utilization of Atomic Energy. Now the SDIO through AFWAL has funded a three-year program at Arizona State University to investigate high-temperature oscillatory thermionic conversion. Ascending toward its thermal limits enables thermionic conversion to produce more power at higher voltages and lower currents with greater efficiencies. These gains accrue with minimal collisional damping afforded by surface ionization and Knudsen-arc-mode operation. Here at high neutralization ratios p actual ionization JEXP greatly outstrips the equilibrium ion currents JISL predicted by Saha and Langmuir. In fact for large values of p the value of EXP can exceed JSL by 100-150 times" (Babanin, Ender et alii). And here high neutralization ratios with low collisional damping at reduced cesium pressures favor strong oscillatory thermionic-conversion outputs. Optimization of these effects appears possible through coefficient utilization of cesium for neutralizing ionization and barium for emitter work-function hence emission-current control. These and other related phenomena as well as important material interactions are subjects of the research on oscillating thermionic conversion recently initiated at ASU. This presentation covers some aspects of that SDIO, AFWAL, ASU program.

Paper Details

Date Published: 6 April 1988
PDF: 11 pages
Proc. SPIE 0871, Space Structures, Power, and Power Conditioning, (6 April 1988); doi: 10.1117/12.943631
Show Author Affiliations
Dean L. Jacobson, Arizona State University (United States)
James F. Morris, Arizona State University (United States)


Published in SPIE Proceedings Vol. 0871:
Space Structures, Power, and Power Conditioning
Raymond F. Askew, Editor(s)

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