for improving converter performance were investigated in order to either improve overall system performance or lessen the burden on the nuclear heat source to the converters. The use of inert gas plasma and structured emitter and collector surfaces were found to be promising means for lowering the voltage drop between the emitter and the collector and thus improving the converter ATTACHMENT : performance. The test results available indicate that the base technology exists for the development of an in-core thermionic nuclear system of a life of about one year, and for out-of-core thermionic conversion system with a life exceeding five years. In the latter case, the life-limiting factors rest with the reactor heat source, not the converters. Further work on converter performance improvement and fuel and insulator material development will lead to thermionic systems of longer life and better performance. Title: Thermionic technology for spacecraft power: progress and problems Source: Proceedings of the AFOSR Special Conference on Prime-Power for High Energy Systems, Norfolk, Virginia, USA, Feb. 22-25, 1982. (Paper No. IX-2) Authors: Huffman, Fred; Lieb, David; Reagan, Peter; Miskolczy, Gabor; <Thermo Electron Corporation, Waltham, Mass 02254> Date: 02-22-82 Classification: u Keywords: space energy conversion, alternative systems Abstract.: Thermionic conversion is one of the most attractive options for use with space reactors. It has a combination of characteristics favorable for space application. The mechanical simplicity associated with no moving parts implies reliability. The high temperature of heat rejection minimizes the mass ATTACHMENT : of the radiator - which is usually the heaviest component of large space power systems. The high heat rejection temperature also limits the size of the radiator, which is an important consideration, since all space reactor systems in the foreseeable future must fit inside the space shuttle bay. Modularity maximizes reliability by eliminating single point system failures. Although thermionic efficiencies up to 15 percent have been demonstrated, much higher efficiencies are theoretical 1y possible with reduced electrode and plasma losses. In addition, thermionics is a demonstrated conversion technology couple to nuclear reactors. Unfortunately, the most impressive demonstrations have been in the Soviet Union. Title: Materials technology for large space structures Source: Proceedings of the AFOSR Special Conference on Prime-Power for High Energy Space Systems, Norfolk, Virginia, USA, Feb. 22-25, 1982. (Paper No. VI1-14) Authors: Blankenship, Charles P.; Tenney, Darrel R.; <Langley Research Center> Date: 02-22-82 Classification: u Keywords: structure and design, materials and coatings, fabrication technology Abstract: This paper will outline several of the key material technology needs that have been identified for large space structures. They include lightweight structural materials, materials durability in the space environment, and some special aspects of materials fabrication technology. Examples of current ATTACHMENT : materials research directed toward large space structures are described. Additional research needs and opportunities are noted. A short bibliography is included of selected references that describe large space structural concepts and related technology needs in detail.
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