A U.S. Department of Energy study in 1979 found the project was technically feasible but prohibitively expensive. Advocates have since developed cheaper scenarios with the help of new technologies. NASA identified several alternatives in a study four years ago. Molly Macauley, who headed up the latest study for Resources for the Future, said that development costs remain a significant barrier today. Macauley, an economist, said a number of technologies would have to be developed for SSP to begin to compete with terrestrial alternatives.
Transportation remains a key barrier.
Launch costs would have to come down by three or four orders of magnitude in order to make SSP feasible, Macauley said. It's difficult to say precisely how much reduction is necessary because SSP satellites are conceptual at this point. NASA is currently working on a number of reusable technologies designed to radically reduce launch costs. The most prominent of these projects, the X-33 vehicle, is running considerably behind schedule and over budget because of technical problems. The report found that SSP faces significant competition from conventional power sources such as coal, oil, and nuclear.