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RISS 인기검색어
- 검색키워드
- 저자 : Yoshihiro ARAKAWA (검색결과 4 건)
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ADVANCED SPACE PROPULSION ACTIVITIES IN JAPAN
Arakawa, Yoshihiro 한국 항공대학교 항공산업기술연구소 1994 航空宇宙産業技術硏究所 硏究誌 Vol.4 No.-
In ths seminar, the outline of advanced space propulsion sctivities in Japan is introduced. The National Space Development Agency of Japan(NASDA) is developing a high-performance liquid rocket engine for the first stage of the H-Ⅱ launch vehicle. The H-Ⅱ is designed to boost 2-tonne class satellites into geostationary orbit. The rocket engine, which is powered by liquid hydrogen and liquid oxygen and named LE-7, is a staged combustion-cycle engine capable of producing about 100-tonnes of thrust and a high impulse (450 sec in vacuum). The engine is manufactured by Mitsubishi Heavy Industries(MHI) and Ishikawajima Heavy Industries (IHI). Powering the second stage of the H-Ⅱ rocket is the LE-5A liquid engine which is an improved version of LE-5 that thas been used to drive the second stage of the H-I rocket. The LE-5A hydrogen/oxygen engine produces a thrust of 12 tonnes and has a restart capability. Japan is also developing high-performance electric thrusters which should be considered a replace technology in future space missions. Electric heating and/or by electrostatic and electromagnetic forces, produces much higher specific impulses than chemical propulsion. The specific impulse is typically ranged form 500 sec to 10,000sec. Such a high specific impulse produced by electric propulsion offers significant propellant mass saving compared to chemical propulsion. Japan covers a large variety of electric propulsion activities, on electrothermal propulsion(arcjet), electrostatic propulsion(Magneto Plasma Dynamic thruster), electrostatic propulsion(ion engine) and other types of thrusters, from fundamental studies to space flight tests. These activities have been performed by governmental research institutes, such as Institute of Space and Astronautical Science(ISAS), National Aerospace Laboratory(NAL), NASDA, and several universities. Several manufacturers such as Mitsubishi Electric Corporation, IHI, and Toshiba Corporation, join and support these activities. In the arcjet, propellant gas introduced in the electrode region is heated by electric are discharge and attain temperatures of 10,000K or more and expands into vacuum through a nozzle with super sonic flow. As the gas temperature is much higher than that of chemical propulsion, the arcjet produces relatively high specific impulses (500-2,000 sec). The energy conversion efficiency, which is defined as the ratio of jet power to electric input power, is around 30%, although is depends on power level, propellant type, etc. The present research in universities, research efforts are concentrated on the improvement of the efficiency and durability. A MPD thruster has been studied and developed in particularly in ISAS and universitis since 1970. Its thrust is produced mainly by electromagnetic forces due to discharge current and induced or externally applied magnetic field. The feature of this type is 1)easy to produce a high thrust density(high-power thruster), 2)a wide range of specific impulses(1,000-10,000 sec). A space test of a sub-kilowatts thruster designed in ISAS is planned to be conducted onbord a Japanese unmanned free flying platform, which will be launched by the H-Ⅱ rocket in early 1995. Tto improve the performance and to obtain scaling laws, much efforts are concentrated on the plasma acceleration mechanism and discharge phenomena. As for ion engine, this type of thruster is considered the most progressive one and will be operated in space for application to a station keeping of satellites and orbit maneuvering within several years. Ions produced in the discharge chamber are extracted and accelerated by electrostatic fields established between the grids to produce a thrust. Its energy conversion efficiency is in a high level(70-80%) at a specific impulse of more than 3,000 sec. NASDA is developing a 1kW-class ion engine system in cooperation with MHI to utilize it for the station keeping of ETS-Ⅳ satellite which will be launched in 1994. Endurance tests of several thousand hours were performed and are continued before the space flight.
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