complexes or power plants, and might, in fact, be les^vulnerable since no terrestrial fuel supply lines are required. A follow-on study has been initiated to improve upon the preliminary assessment. Its purpose is to make an in-depth analysis of the ways to counteract real and perceived potential military threats and vulnerabilities of the SPS and its components. This study will be completed in May 1980. IV.7 Will development of the SPS seriously deplete any of the earth's resources? Two independent studies have been completed which address the question.51in both cases the answer is "no." Both studies screened the twenty two basic materials required for SPS production and both found some problems in the supply or production of certain materials. The more serious problems are those associated with the solar cell materials (gallium, gallium arsenide, sapphire, and solar grade silicon), and the graphite fiber required for the satellite structure and space construction facilities. In addition to these mercury, tungsten and silver were found by both investigators to be potential problems as were kapton, borosilicate glass and liquid hydrogen. Most of these are problems in terms of currently identified reserves, production capabilities, import requirements and the like and could be ameliorated. For example, gallium, which both investigators class as perhaps the most serious problem is judged "not to be a limiting factor over the long term'' by the Aluminum Company of America. $0”Key Crude Oil and Product Pipelines are Vulnerable to Disruption,” EMD-79-63, U.S. General Accounting Office, August 27, 1979. ^Kotin, Alan, SPS Preliminary Societal Assessment: Resources Requirements, DOE HCP/R-4024-02, October 1978. 52Teeter, R.R. and W.M.Jamieson, "Preliminary Materials Assessment for the Satellite Power System," Battelle Columbus Laboratories, September 1979. 53 "Survey of Availability and Economical Extractability of Gallium from Earth Resources," Aluminum Company of America, October 1976.
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