I. INTRODUCTION The U.S. Department of Energy (DOE) and the National Aeronautics and Space Administration (NASA) are investigating a potential new source of energy called the Satellite Power System (SPS).—/ The SPS concept involves placing in orbit around the earth satellites equipped with large solar arrays. The arrays collect solar radiation from the sun (approximately 99 percent of the time), which is then converted to electromagnetic radiation and beamed by a transmission system located on the satellites to receiving/conversion stations on the ground. The receiving equipment at the conversion station changes the electromagnetic radiation to electricity that can be fed directly into the utility network. The satellite and receiving antenna/rectifier (rectenna), for the current NASA- reference system using solar cells, and microwave power transmission subsystems are approximately 50 and 100 sq. km in size, respectively. The system is designed so that each rectenna will provide power to the utility grid. The scope of the concept can be placed in perspective by considering that the generating capacity of these satellites would be equal to all the electrical power generated in the United States in 1975. Projected energy demand at the turn of the century, as well as basic economics, indicate that at least 60 satellites will need to be programmed. Such a system is anticipated to have far-reaching impacts on society. The SPS will have many features in common with systems of past and current space programs and will build on the technology that these programs have created. System development, production, and deployment will be costly processes, and SPS relative productiveness will be relied on to place it within the cost feasibility range. Lightweight structures and equipment and reliable operation, made possible by the favorable environment of space and design for the market, may hold the secrets to the needed cost control. If it is believed that the SPS will fulfill its postulated role by becoming a supplier of a significant part of the total energy consumed in the United States at some time during the first half of the twenty- first century, then SPS development, production, and deployed assets are valuable to both civilian and military segments of our nation now and in the forseeable future. Furthermore, if the United States decides to depend on the SPS for so great a part of its total energy supply, the system must be secure. Some believe that the SPS cannot be defended successfully, but that if it could be, this defense would cost more than the SPS.
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