Past and Current Space Solar Power Projects____________________________ The purpose of this appendix is to provide a limited amount of information on all significant space power projects, proposals and demonstrations. There are references provided where available for those interested to locate more information on the individual designs. We outline the main properties - power levels, orbit selection and technology choice - and innovations of each project. In addition, some are illustrated for clarity. References for all projects are given at the end of the entry for that project. The projects have been divided into two main groups. Firstly large scale projects, those of 500kW and over, and secondly those below this figure. This second category will include purely experimental projects with direct space power application. Within these categories the projects are arranged roughly chronologically. The three basic types of space power are outlined in the diagram below. Most of the concepts mentioned below correspond to one of these models, with the exception of those concerned with powering satellites and the demonstrations. 1. Big Projects (over 500kW) Glaser's concept (1968) The initial serious proposal for space power utilisation, Glaser suggested the use of large platforms in geostationary orbit. Photovoltaics were used for conversion of solar energy to electricity and the power beamed to earth using microwaves at 2.45GHz. Also suggested were nuclear reactors in orbit, as they are safer in orbit than on the Earth's surface, beaming power down to earth. Glaser, P.E., Power from the Sun: Its Future, Science, vol 162 no 3856, pp 857-861, 1968 NASA/DOE Reference System (1980) In 1980 NASA and the U.S. Department of Energy (DOE) completed their Space Solar Power study, started in 1977, which considered all relevant technologies and many design concepts before creating one detailed point design, called the reference design. This consisted of a system of 10km by 5km platforms of silicon photovoltaic cells in geosynchronous orbit, with a 1km diameter transmitting antenna for 2.45GHz microwaves. These satellites would be used to provide 5GW of continuous baseload power to earth, collected at 5km diameter rectenna sites on Earth. The study concluded that such a system would be economically viable, but a subsequent overview by the National Academy of Sciences rejected this saying that certain assumptions, notably the low launch costs assumed in the initial study, were unrealistic. _____, Solar Power Satellite System Definition Study, NASA/DOE, 1980
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