8.2. White Paper: Bill Brown RECOMMENDED PROGRAM OF EXPERIMENTAL DEMONSTRATION AND REFINEMENT OF WIRELESS POWER TRANSMISSION TECHNOLOGY IN THE CONTEXT OF SPACE SOLAR POWER William C. Brown Microwave Power Transmission Systems May 1996 I am appreciative of being asked to write a “white paper” for the current Space Solar Power study, from the point of view of one who has had much experience over a long period of time with the technology of wireless power transmission and its application, including the very important one of the Solar Power Satellite. I have a good memory of the DOE/NASA study of the SPS that was successfully carried out in the 1977 to 1980 time period. But my perspective goes further back than that to the 1968 date when Peter Glaser first published his concept of the Solar Power Satellite and we observed how dependent the concept was upon the wireless power transmission technology being investigated and developed at that time by the Raytheon Company. Subsequently the four companies of A. D. Little, the Raytheon Co., the Grumman Aerospace Corp., and Textron, Inc. joined together to evaluate the concept with a four volume technical study which determined that the concept was feasible. The chief executives of the four companies then recommended to NASA that the SPS be incorporated into their long range planning. With this background, and within the constraints of time and support, the author has chosen to limit the subject material of the paper to (1) his response to the SAIC report on the first year’s study effort and a specific proposal for a work effort of demonstration and technology refinement and (2) a review of the critical requirements imposed upon the microwave generator in the space based transmitter in the SPS and a limited discussion of how best to meet these requirements. L RESPONSE TO THE SAIC REPORT AND RECOMMENDED WORK EFFORT Introduction The author has a particularly good perspective on the microwave power transmission subsystem of the SSP system because of his early pioneering efforts in wireless power transmission and the experience of seeing how this technology has changed and progressed in its effort to meet the demanding requirements of suggested applications for it. But although the technology has changed and improved it is still constrained by the laws of nature. These natural constraints are particularly evident in the case of the SPS. There is the constraint of the severe attenuation of the microwave beam in the Earth’s atmosphere at the shorter micro wave wavelengths. On the other hand, for efficient transmission of micro wave power, the law of diffiaction places a constraint on the size of the apertures that are necessary for efficient power transmission. For the longer wavelength microwaves that easily traverse the Earth’s atmosphere the apertures are large. While this provides the opportunity for using such large apertures to transmit very large amounts of power - of the order of five gigawatts, the costs of developing and placing the first of such systems in space represents a very large investment which we would like to avoid.
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