can become economically attractive and competitive. We are continuing these cost studies and, when they are completed, we would be most happy to submit the results to this subcommittee. Our approach has been, and will continue to be, based on a commonsense design-to-cost philosophy. We know that for the program to make economic sense it must provide power at a competitive cost at the time the system is operational. We have used as our design-to-cost goal, bus bar power costs in a range of 20 to 30 mills per kilowatt-hour in 1975 dollars. This cost target appears to be within the competitive range for coal and nuclear-generated electrical costs in the first decade of the next century. And I think this is quite comparable to the answers given in the previous testimony. We then tried to construct a power-satellite concept which both would be within a reasonable extrapolation of current technology and would be capable of being designed, built and operated to produce power in this cost range. In addition, we have estimated the energy payback time for such a concept—that is, the time for the power satellite to generate the amount of energy required to build it, place it in orbit, and operate it over its lifetime of some 30 to 100 years. We find this time could be less than 2 years—in the neighborhood of 2 to 3 or 4 years. Senator Ford. Why is the range so large, so wide—30 to 100 years? It is just unknown how long it will last? Mr. Taylor. Principally because some of the elements of the system have a finite lifetime and you would want to replace them, and that is principally the reason for putting in such a wide range. With this attractive payback time, it appears that the power satellite could be an attractive nondepletable, nonpolluting power source of the future even if our present estimates are off by 100 percent—and I don't believe they are. Powersat should eventually become an economically viable power source of the future. How? Fossil fuel is finite, power consumption steadily is growing and, the cost of energy is constantly rising. The point at which our oil and coal reserves are entirely depleted may be a matter of argument, but the fact that they eventually will be depleted is not. At some point in the not-too-distant future, the cost of these fuels will reach the cost of the development of a nondepletable new source. And the sooner we can develop a competitively priced alternative, the more fossil fuel we will have remaining for critical uses other than the generation of electricity. Again, I must emphasize that space-based solar energy never will be the entire energy answer. But we feel it definitely must be one of the options. Nuclear fission, and with it the breeder reactor, must be developed further. Fusion, though promising no near-term reward, should be pursued. Ground-based solar power should be on line long before we will be grazing at a string of power satellites twinkling in the night sky. What should we do? A logical beginning would be the undertaking of thorough, complete systems and economics analyses to set requirements and cost targets. The Space Shuttle also should be looked upon as a key to the development of power satellite technology. It not only can carry into space
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