the study were: (1) to develop a comprehensive prototype assessment of the non-microwave-related impacts on the natural and human environments of the SPS reference systems ground receiving station (GRS); (2) to assess the impacts of GRS construction and operations in the context of actual baseline data for the specific site; and (3) identify the critical GRS characteristics or parameters that are most significant in terms of both the natural and human environment. The prototype EIS concluded that the critical project parameters include: the sheer size and intensivity of use of the contiguous land area required by an SPS GRS; the lack of flexibility in siting individual rectenna structures once the rectenna boundaries are established; the difficulties in finding suitable sites that do not conflict with other societal needs and values; uncertainties relating to reestablishing nature ecosystems following total ecosystem modifications during construction, and the related need for further research into microclimatic effects near the ground-surface beneath the rectenna panels; the proposed two-year GRS construction schedule which has significant implications for project socioeconomic impacts, air quality, water supply and biological resources and possible logistical problems for GRS construction - all of which could be reduced by extending the construction schedule; and the public versus private GRS ownership which has significant implications for GRS impacts on the local tax base. Since the earth and space components of the SPS will require enormous amounts of materials, a materials assessment was conducted to detail the material requirements for SPS and to identify potential availability problems and constraints so that responsive action could be defined and incorporated into overall SPS planning. The materials assessment analysis identified 22 materials used in the SPS, and tracing the production processes for these 22 materials, identified a total demand for over 20 different bulk materials and revealed a requirement for nearly 50 raw materials. The analysis evaluates each material in terms of world and domestic supply, manufacturing capacity and adequacy of the data base. The refined methodology uses computerized screening of the materials with the flags raised at various threshold levels as a function of several parameters, such as current domestic and world production rates and domestic and world reserves. Thresholds can be changed and the analysis rapidly run to determine sensitivities. Assessment of these SPS material requirements produced a number of potential material supply problems (Exhibit 2), the more serious 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 general, the gallium arsenide SPS option exhibits more serious problems than the silicon option, possibly because gallium arsenide technology is not as well developed as that for silicon.
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