is not designed nor intended to establish a “go” or “no go” decision on the construction of one or a fleet of geosynchronous space power stations. The major product of the 16 million dollars spent to date on these studies will be a series of approximately 200 reports. A very thorough system of documentation is being employed to allow the tracing of every decision step and datum derived in the studies. This will allow the expedient challenging of conclusions and results. Major objects of study have included the microwave beam to be used for power transmission, the conversion of direct current to radio frequency energy and the specific possibility of utilizing solid state devices, the effects of the space environment on materials which are likely to be used in an SPS, and structural dynamics of the large structures. Considerable attention is being given to the use of lasers for power transmission to Earth because of the smaller transmitting and receiving equipment which might be used and the possibility of direct pumping in space of the lasing gas by sunlight. Transportation and rectenna construction each constitute approximately 1/3 of the total costs of SPS production. One can anticipate that approximately 1000 people would be present in space during the construction of the SPS's. Following detailed investigations, the problem of radio frequency interference with terrestrial communications and other electronic systems is considered to be manageable. Technical fixes appear possible. There is a greater possibility of radio frequency interference with satellites in earth orbit, and there may be significant problems with satellite electronics which view an SPS antenna directly. Terrestrial radio telescope observations may be limited by SPS operations. Light reflected from the structure of an SPS may be a problem for several days twice a year. Viewing the satellite with binoculars might produce eye damage due to the intensity of the reflected light and the small angular size of the satellite. There are several problems receiving continued attention. The SPS would make large use of gallium, sapphire, graphite fiber materials and other reasonably exotic materials, some are in short supply. Many of the terrestrial users of large quantities of power (primarily large urban areas) are not located close to land areas where a 5 km diameter rectenna could be conveniently located. Identification is needed of a version of the SPS which is clearly non-threatening from a military viewpoint. There are major problems with social acceptability of the microwave approach, land use and centralized power, high start-up costs and pollution by the launch vehicles. Extensive experiments are in progress on the effects of low level microwaves, 10 gW/cm2 to 20 mW/cm2, on various insects (bees) and animals. These experiments are necessary because of the paucity of reliable data in either controlled experiments or medical histories. Research has been conducted with the Aericebo radar installation in Puerto Rico into the heating of ionospheric electrons and the ionosphere by microwaves at somewhat different frequencies and lower power levels than proposed for the SPS. To date the experiments indicate less heating than predicted. The creation of radio wave scattering layers in the ionosphere by the microwave heating effects are negligible in the initial experiments. At this point in time there is no clear cost advantage in the power expected to be produced by light water reactors, coal/steam systems, terrestrial photovoltaics, SPS, coal/gas fired turbines, light metal fast breeder reactors or magnetically confined fusion systems. The Department of Energy has taken as an important part of its tasks, a search for systems which can supply the power needs of the world. It is looking at all options. It is expected that careful early studies of the societal acceptability of the SPS will
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