For an earth-launched turbogenerator SSPS the capital cost must be held equal to that of a present-day coal-fired plant; the specific mass must be reduced to about half the value currently attainable; e must be raised to 0.70; and the lift cost must be reduced by about a factor of 10 below the figure now considered to be attainable in the 1980's without substantial postshuttle development. Table 1 summarizes the values of these factors which have been assumed in several studies and, where the information is available, the resulting estimate of power cost extrapolations to vehicles more advanced than shuttle-derived rockets are necessarily subject to large uncertainties; new developments in engines, heat shields, reusable fuel tanks, and other components would all be needed before their construction. For a very large vehicle capable of lifting 180 tons to low orbit, estimates of attainable recurring cost range from $80/kgsy to $900/kgsy, and estimates 12 of development cost range from $5 billion to more than $25 billion. Table 1 (Critical factors in satellite power station economics. The numbers assumed in several studies for the factors specific power plant mass, component lift cost from the earth, transmission loss factor (c-1), and interest rate are summarized; in each case a higher number corresponds to a more conservative assumption. Earth-launched SSPS values are from^ for those with turbogenerators and from7 for those with photovoltaic cells. Data in the last column are from this article. The lift cost from the earth to geosynchronous corbit is approximately equal to the cost for lift to Lagrange point L5. For base-load service, busbar power costs are now typically 15 to 17 mill/kwh.)
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