Electrotechnical Laboratory [ETL] 1. Introduction The Electrotechnical Laboratory of the Agency of Industrial Science and Technology, MITI is not carrying out research oriented toward solar power satellite, but related space technology research on space robots, receivers for space solar dynamic power generation and large radiators. In addition, it is developing the solar cell and sodium thermoelectric converter (AMTEC) for use on the earth, which also have high potential for space use. 2. Space Robot The Space Technology Section is researching a space robot for use in the construction and maintenance of large space structures such as solar power satellites. In space environments, extravehicular activity will be extremely hazardous and inefficient, making the use of robots indispensable for operations other than intelligent tasks. The laboratory investigated a "space manipulator" in 1982, ahead of other research institutes, and began a project to develop a manipulator compatible with the space environment In 1988 research started on flying robot motion control and system technology based on research into “space teleoperator technology," the precursory research in Japan. The teleoperator shown in Fig. 1 is a space robot moving freely on a two-dimensional simulator on the ground. Mobile service robots capable of moving about with great flexibility for both service and operations in space will be required. This prototype simulator was made to investigate tracking, capturing and conveying floating bodies, flight maneuvers to space facilities for offering services, and controlling landing, walking operations in gravity-free environments. The teleoperator on a platform jets a gas downward, so friction force is eliminated allowing free movement on the two dimensional simulator. 3. Receiver (or Space Solar Dynamic Power Generation The Energy Materials Section is doing research on a receiver for space solar dynamic power generation to supply electricity to low-orbit space stations. For thermal storage of the receiver, LiF and LiF-CaF, with high latent heat are promising. However, the latent thermal storage system with the fluoride salts has drawbacks. Since they melt under micro gravity and the volume change on fusion is so large that there might be thermal stress on the container as well as reduction of heat conduction due to void formation in the fluoride storage materials. To overcome these problems, a concept of composite latent thermal storage materials has been proposed. They are produced by impregnating molten fluoride salts in porous silicon carbide or carbon materials with high thermal conductivity. To investigate the heat transfer and thermal stress characteristics of the thermal storage unit under practical conditions, a test loop (Fig. 2) using He-Xe as the working medium was built This experimental loop is designed primarily for testing a thermal Fig. 2 He-Xe loop for receiver component evaluation Fig. 1 Space teleoperator
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