Features of the prospective project The CDEP has indicated that even if an SPS is technically feasible, it is difficult to realize it as an actual project or program because of other reasons. To look into this aspect, we would like to list and briefly discuss the important features required for the 10 MW class SPS which is much smaller than the Reference System, and the possibility for SPS 2000 to be realized from these viewpoints. Realistic demand research A 10 MW class SPS discussed here is equivalent to a 300 kW terrestrial electrical power plant in terms of the average daytime power supply. Although just an experimental facility in industrialized nations, it could be useful in remote land. We need to find out the demand to use such a system as an operational power generating system, to justify the investment. Without such a demand, the SPS will not be successfully demonstrated as a power system for terrestrial application. This approach and the simplicity of the system will make SPS 2000 significantly realistic, compared with the Reference System whose concept has been developed as a hypothetical national electrical power system. Growth and technology update strategy The first commercial electrical power station made by Edison started service with a single 200 HP engine in 1882 (9], The present terrestrial electrical power systems have evolved gradually from the early age models, responding to the demands and incorporating the progress of technologies. The situation of SPS 2000 should be similar to the Edison's first power station. It will not be a planned step of technology development of a future system in a framework of a huge single program. Space projects well defined in advance according to phased project planning, often give new technologies little chance to be employed when available. Since the mission of SPS 2000 is to simply supply electrical power from space, and the system is modularized, technology updates which allows technologies used for major subsystems to be changed to avoid outdating of the system after it is planned can be applied more easily than in the traditional sophisticated spacecraft. To ensure this, SPS 2000 definition of detail will be made only for each flight unit, but not for the overall system. Low cost policy The cost estimation of the Reference System suggested that the SPS electrical power would be economically competitive with conventional power systems. However, the estimation is based on a low cost transportation system specially developed for this purpose. In the space industrialization era, the transportation service should be provided by the space infrastructure. Therefore, SPS 2000 project will use available commercial transportation systems. The present transportation price is very expensive. The approach taken by the communications industry to make space business pay off the high price is to increase the performance of a space system per flight by employing expensive high
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