□ nd env ironmenlal welfare. Some of the experiment- included are funded a- candidate experiment- for -pace station and SFU free fix er mission-. F/x. 2 Artist's concept ut the first SFU mission 3. Research Activities of SPS Working Group In 19S8. the Solar Power Satellite working group was organized by ISAS with the participation of researchers from universities and national laboratories, specializing in related technologies among the following thirteen subgroups: • Study on Subsystems and Technologies Microw as e transmission Microwave reception Large -pace structures Guidance and control Laser power technology Photovoltaic cells Thermodynamic power generators Propulsion Space robotics • Study on Environmental Interaction Effects Spacecraft environment Space electromagnetic environment Communication systems Biology and ecology The research activities of (he working group are divided into four research projects supported by different budgetary categories. (1) SFU Energy Mission Study The space station mission requirement study encouraged researchers to prepare small scale space energy experiments in space. Some basic studies are being funded as space station experiments, and the first SFL mission will allow the earliest chance to realize others. The SFU is a free flying platform retrievable by Space Shuttle, now under development as a Japanese national project with the first flight scheduled to take place in 1994 (Fig. 2). Tire SPS Working Group is proposing the SFU Energy Mission as an SFU follow-on mission to conduct SPS related research. The experiments now proposed aire the Thermo-Dynamic Power Generation Experiment (TDPGE). Elecirtv Propulsion Experiment (EPEX). Microwawe Energy Transmission in Space tMETSt. Space Tether Experiment- (STEX) Autonomous Satellite Retrieval Experiment lASREX). and Laser Propulsion Experiment . The TDPGE (Fig. 3) is intended to demonstrate the operation of a solar dy namic system in a space environment by operating continuously for more than I(X) days. The system will consist of an AC generator and a Stirling engine, equipped with a solar concentrator and thermal -tor- age. A free-pision ty pe w ill be used for the engine. The system will generate about 2 kW of electric power on average. which will be used by the electric propulsion experiment. The EPEX will have 2 kW MPD aejets for orbit transfer and DC arejets lor altitude control (Fig. 4). The primary objective of the EPEX is to verify the system performance at full power, by raising the SFU orbit up to 100 km in two week-. The propellant will be hydrazine. The electric pow'er will be generated by the thermo-dynamic engine generator. A preliminary model will fly on the first SFU mission. The METS experiment Fig.5 is planned to develop and verify energy transmission technology u-ing micros jve beam in space. It is also intended to mitigate the nonlinear interaction between intense microwaves and the ionospheric plasma. The microwave pulse of 5 kW will be transmitted from a phased-airay antenna and will be received by a rectenna on a subsatelliic. Plasma diagnostic instruments, such as plasma probes and plasma wave detectors, are onboard both the SFU and the siibsatellite. The STEX (Fig. 6) will deploy a tethered satellite up to 10 kin from the SFU. A Kevlar tether of 0.5 mm diameter will be used. The tethered satellite will contain various environment monitors. STEX is aimed at studying a large-scale space environment modified by SPS elements (large space structure, electric propulsion, microwave transmission, and high voltage solar array). It is also intended lo study the dynamics and control laws of a large flexible structure in -pace. The ASREX (Fig. 7) will verify important techniques necessary for space robotics, including laser radar, autonomous rendezvous. image processing, an autonomous motion analysis, and manipulator control. The system contains a laser radar, a manipulator, a cold gas jet subsystem, a target satellite, and a satellite latch mechanism. In this experiment, the target satellite will move 20 km apart from the SFU, and will be autonomou-ly retrieved. The LPE is to develop the technologies of laser assissted propulsion in space. A la-
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