12. Hiroshi Hashimoto: Topics Relating to the Development of a Satellite Power System 13. Kiyohiko Itoh and Yasuhiro Akiba: A Consideration on “Rectenna” for Microwave Power Reception from SPS Prof. Adachi, Tohoku University, discussed optimization of the microwave power transmission system under the constraint of electromagnetic environments outside of a receiving antenna aperture from standpoint of antenna design, and indicated that if a certain aperture illumination was used, the maximum receivable power significantly increased at slight sacrifice of transmission efficiency. Dr. Mori, Radio Research Laboratories (RRL), considered the experimental condition to study ionosphere heating by the microwave transmitted from a space station in a low Earth orbit. He estimated that a microwave power of several mega watts transmitted from an antenna as large as a few hundred meters in diameter was required. Prof. Tanatsugu, ISAS, presented a concept applying a Stirling engine for space solar power system. As a result of study of a power generation unit of 250 kW electrical output power, it was found that the Stirling engine system is comparable to a high performance solar cell system. The rest of the papers featured a common subject, the 10 MW SPS conceptual study. As described in the fourth paper in the list by Prof. Nagatomo who coordinated the study groups, this study intended to figure an intermediate test model to give the Japanese people a realistic impression of SPS. A basic study guideline was provided in the paper. The reason why the power level of 10 MW had been selected for the study was that it was the approximate geometric average of the maximum power level of the coming space station and the minimum of an operational model, which are estimated to be 100 kW and 1 GW respectively. Mr. Kato, Kawasaki Heavy Industries Ltd. (KHI), represented the KHI study group to report the result of study on the main structure and construction of the SPS. Their approach was to verify the feasibility of building the main structure of the SPS with conventionally designed truss structures made of carbon fiber reinforced poly- salfone, using beam builders. The basic characteristics of the structure were estimated and a construction procedure was planned. It was pointed out that individual technologies should be developed for more detail study. Dr. Kudo, Electrotechnical Laboratory (ETL), representing the study group of power distribution, focussed on the problem of power loss due to the resistance of onboard electrical power lines and high electrical current. To solve this problem, cryogenically cooled superconducting cable was proposed instead of adopting a high voltage and low current system. He also suggested using robots for sophisticated wiring work on the superconducting cable system. Mr. Ohnaka, Fujitsu Ltd., and his study group studied the configurations of a power transmission antenna to be mounted on the SPS as well as a ground powerreceiving panel concept. The onboard microwave power devices considered were klystron, magnetron and GaAs FET. A forecast of technical feasibility of the solidstate power devices was provided. Mr. Suzuki, SHARP Corporation, studied solar cells and array constructions. The recommended system was 50 units of subarray which use 104,000 pieces of Large Area Ultra Thin Silicone Solar Cell (LAUT) array laminated with resin film for each. He chose this system because early development was required. Mr. Kondo, Ishikawajima-Harima Heavy Industries Ltd. (IHI), spoke about a
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