arbitrarily chosen, being the time before the Space Shuttle becomes operational. No contribution from existing programs was assumed. In fact, many of the activities would be performed anyway, although perhaps not to the required depth. In particular, some advanced studies required in the transportation, operations, and structures areas are already part of the NASA overall program in their own right. A space-based technology development program, necessary to resolve those issues that can only be studied in the space environment, is seen as the second phase. The objectives of this program phase would be similar to those of the previous phase, but would involve space-based efforts rather than ground-based efforts. No efforts have yet been made to scope this program phase. Only a general look at what it would probably involve is reasonable at the present time. The Space Shuttle (as shown in Figure 6, p. 215) would serve as both transportation and as a test bed for the orbital development work. Requirements for space development (that could not be done on the ground) would involve zero gravity (e.g. assembly techniques), the space environment (e.g. materials properties or hardware performance), or the .orbit-to-ground capability (e.g. micro wave transmission). It seems reasonable to predict that some type of subscale, orbital demonstration would be required prior to further development of any satellite power system. Only general observations about this third phase are possible now, but the probable timeframe would be the mid-to-late 80's, utilizing the Space Shuttle Transportation System. This intermediate step would not require the large development commitment of the following phases. The likely objectives of a subscale, orbital demonstration program would be to demonstrate to the extent reasonable the end-to-end performance of the system elements, to verify predicted performance of critical system elements, and to add to the data base for projecting operational system costs. One possible concept is shown in Figure 7, page 217. This very preliminary concept is the result of a six- week study. In addition to these specific objectives, any subscale orbital demonstration program could be expected to contribute to the strength of the space program in general, in particular with regard to the areas of large space structures, assembly, space operations, power conversion, and power transmission. To summarize, the potential of satellite power systems appears promising, and further investigations should be made. There is a large commonality between the objectives required by a satellite power system program and those of the space program in general. The problems ahead are seen as large scale advanced technology and engineering development. Scientific breakthroughs are not required. Only a modest commitment to the next phase is required at this time; a large scale commitment is not appropriate. In many ways, satellite power systems would be a different kind of space effort from those of the past. Figure 8a suggests the analogy to large scale terrestrial engineering and construction effort in a hostile environment. Further system analysis and definition accompanied by technology studies and development are the next step in the considerations of satellite power systems. These efforts should include vigorous studies into the possible environmental effects. This is also the time to initiate preliminary planning for the use of the Space Shuttle for space-based technology development when the Shuttle becomes available in the early 1980's. Based on a forecast of U.S. electrical energy consumption, the potential impact of satellite power systems could be significant as shown by Figure 8 (see p. 218). We have assumed that the first operational 5000 mw satellite would be on-line in 1995 and to illustrate the cumulative impact have assumed a rate of five satellites per year by 2005. These calculations imply that about % of the capacity to be added after 1995 might be obtained from satellite power systems. Based on this and previous testimony, I am sure you appreciate that a significant number of critical technical problems must be solved to achieve the indicated capacity. These problems are the major areas identified in the Critical Areas Report and include: System Definition, Microwave Power Transmission, Space Structures and Assembly, Transportation, Attitude Control, Power Conversion and Operations. It is generally accepted that solar energy will play a significant role in the solution of the energy growth problem facing the country and the world. I feel strongly that the prospects are very good that solar energy from space will prove to be feasible and economical. Thank you.
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