Japanese Perspective on Power from Space for Earth Y. KURODA/ M. NAGATOMO AND P. COLLINS" This paper does not represent any Japanese national organization, nor does it express any official view on this subject. Japanese activities in the field of space power systems consist of two different types: one is technology development in the context of the national space program, and the other is more basic research pursuing authorization in the near future. Power from space belongs to the second category of activities, which is conducted mainly by university researchers and voluntary participants from the private sector, including the SPS 2000 task team and supporting members. Space is believed by some people to provide mankind with the opportunity to expand their activities into limitless growth; space industrialization has been rationalized in this way. However, few studies have examined or certified this forecast quantitatively. We present results obtained by Dr. Yamagiwa showing how a World Dynamics model can be modified by introducing extraterrestrial energy and materials to human activities on Earth. These figures show the future trend of key factors of human activities, such as population, carbon dioxide and others. It should be noted that the growth rate goes down next century in the case of a closed Earth system, while the trend is improved in another case in which power from space begins to be introduced at the beginning of the next century. However, such improvement is only possible when it is assumed that the cost for SPS is similar to that for existing terrestrial industry, such as cars and machinery. The present high cost of space technology would not satisfy the required condition for power from space to benefit the Earth. The scientific principles of SPS are so well-known that there is no substantial obstacle to realize power from space. The major question is how to start to build such a system. The SPS 2000 task team’s conceptual study is a feasibility study on the first step of power from space to Earth, following four requirements: 1. SPS 2000 is to be realized as soon as possible. There is no special reason to make it a future system, so this study assumes construction of the system should start before 2000, which means practically as soon as possible. It also means that the satellite must be in low Earth orbit, and so, in order to deliver power to the receivers on Earth as often as possible, it must orbit the Equator. f Shimizu Corporation " ISAS, Japan
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