0191 -9067/82/010045-27$03.00/0 Copyright ® 1982 SUNSAT Energy Council LASER SATELLITE POWER SYSTEMS: CONCEPTS AND ISSUES EDWARD W. WALBRIDGE Energy and Environmental Systems Division Argonne National Laboratory Argonne, Illinois 60439, USA Abstract — A laser satellite power system (SPS) converts solar power captured by Earthorbiting satellites into electrical power on the Earth's surface, the satellite-to-ground transmission of power being effected by a laser beam. The laser SPS is an alternative to the microwave SPS. Lasers and how they work are described, as are the types of lasers — electric discharge, direct and indirect solar pumped, free electron, and closed-cycle chemical — that are candidates for application in a laser SPS. The advantages of a laser SPS over the microwave alternative are pointed out. One such advantage is that, for the same power delivered to the utility busbar, land requirements for a laser system are much smaller (by a factor of 21) than those for a microwave system. The four laser SPS concepts that have been presented in the literature are described and commented on. Finally key issues for further laser SPS research are discussed. 1. INTRODUCTION Alternative satellite power system (SPS) concepts have been scrutinized under the sponsorship of the U.S. Department of Energy (DOE) and the National Aeronautics and Space Administration (NASA). To date, concepts using microwaves for power transmission have received the most attention, and microwave power transmission was selected for the reference design (1). An intriguing alternative to the reference design is an SPS that uses a laser beam to transmit power to Earth. A laser SPS would provide the same electrical power output to the utility grid, but with significantly reduced land requirements and without some of the uncertainties in the environmental effects of microwave transmission. Sections 2, 3, and 4 of this report explain how lasers work, review the different types of lasers, and describe the advantages of a laser SPS. Sections 5, 6, and 7 describe alternative subsystems, the Lockheed laser SPS, and alternative laser SPS concepts. Section 8 identifies key issues for further research. 2. LASERS AND HOW THEY WORK A laser amplifies light by stimulated emission of photons. It can be operated so that all the photons in its output beam have the remarkable properties of being in phase and having very nearly the same frequency and direction. As a result, the output beam can propagate for great distances with very little beam spreading.
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