Attainment of the commercial feasibility objective means that high- risk technical solutions should be avoided as should solutions that imply tying up large sums of capital over extended periods of time. C. SCALE The study will be funded at a level not to exceed $35,000, and must be completed, with final report delivered, within one year of contract award. D. SPS HISTORY AND STATUS The SPS allows tapping the inexhaustible energy resource of sunlight in space, to sustain human activities on Earth. The use of nonterrestrial resources for SPS construction could help meet the energy requirements of the growing global population in the 21st century, as the majority of the world's population enters the industrial revolution. Preliminary studies of the SPS concept were carried out from 1968 to 1972, when a plan for an SPS R&D program was outlined by the National Science Foundation and NASA. Between 1974 and 1978 a series of feasibility studies by NASA addressed key technological environmental and economic issues. In 1978 the U.S. Dept, of Energy evaluated the SPS concept with the objective to develop by 1981 an initial understanding of the technical feasibility, economic practicality, and societal and environmental acceptability of the SPS concept. In that concept solar cell arrays were to convert solar energy directly into electricity, and feed it to microwave generators forming part of a planar, phased-array transmitting antenna. The antenna would direct
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