0883-6272/86 $3.00 4- .00 Copyright ' 1986 SUN SAT Energy Council 10 MW SATELLITE POWER SYSTEM : A SPACE STATION MISSION BEYOND 2000 Makoto Nagatomo* Institute of Space and Astronautical Science, 4-6-1, Komaba Meguro-ku, Tokyo 153 Japan ABSTRACT Beyond 2000, more complicated systems will be developed in space, based on ten years of experience of the space station. An example is the 10 MW (mega watts) SPS (Satellite Power System) which was once studied by a Japanese group as a test bed for the technologies developed during the earlier phase of the space station program and the environmental research. The 10 MW SPS consists of main subsystems of an SPS ; solar cell panel, electrical power line, microwave generator and a power transmitting antenna. The area of the solar panel is 400 m x 600 m, which is large enough to generate an electrical power of 30 MW with photovoltaic devices. All phases of this project from construction through operation have been considered to be the objectives of this mission. The concept has been reexamined from standpoint of a space station mission. As a result, several findings have been pointed out to refine the concept. To reduce the cost, the method of the construction should be modified in the direction to take advantage of low cost service of the space infrastructure the space station provides rather than to build an independent space system. It is important to incorporate various missions and technologies inviting more participants of the joint enterprise to share the mission. Possibly there will be users to pay for the mission product. The more benefit of output of the system has to be demonstrated prior to initiation of the project to get financial support. INTRODUCTION The space station is considered to be a stepping stone for large scale space industrialization and development of frontiers. The manned Mars exploration, lunar base and space solar power station are the typical areas of future activities beyond this stepping stone. The missions proposed for the space station are mainly related to basic technologies of space infrastructure and space operation. Accumulated experiences with such missions will make it possible to build a more complex system consisting of several existing systems. Thus the large space power system will be a mission of the next generation. The purpose of this paper is to see possibility to apply a 10 MW SPS concept to a mission of a growth version of the space station beyond 2000. The 10 MW SPS was studied by a voluntier group of Japanese industries. The result was presented at the second ISAS (Institute of Space and Astronautical Science) Space Energy Symposium. An overview of the 10 MW SPS concept will be introduced here based on the proceedings and reexamined from a viewpoint of the space station mission. Potential benefit of the experimental system will be discussed. ORIGINAL CONCEPT OF 10 MW SPS The reference model of the SPS defined by DOE and NASA of the United States gave us a clear but enormous impression of an operational solar power satellite. Inevitably a smaller test model has to be built for verification of various areas of the system. Purpose of the study on the 10 MW SPS model was to provide realistic concept of intermediate test model between an operational SPS and the space station. The guidelines of study for the 10 MW SPS were established generally in the direction of the engineering features of using photovoltaic solar energy conversion and 2.45 GHz microwave for power transmission which had been proposed by Glaser (1968). The objectives of the 10 MW SPS project were given as; 1) construction practice, 2) power transmission test and 3) orbit transfer of the SPS by solar electric propulsion. The power level of the 10 MW SPS was determined by selecting one point between the power range of an DOE/NASA operational model and that of the electrical power supply of the space station. Selection of two power levels in the same power ranges might be possible if the maximum capability for the space station to handle such a large space system is considered as a more critical factor for it. Thus the power level has no special meaning. Actually, the area of the solar cell array of the 10 MW SPS is equivalent to an electrical power of more than 30 MW generated by solar cells. A brief description of the subsystems is given in the following for later discussions.
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