Space Solar Power (SSP) Exploratory Research and Technology (SERT) program.

1-2 BACKGROUND

From 1979 to 1981, the Committee on Solar Power Systems, Environmental Studies Board, of the National Research Council (NRC) evaluated DOE’s and NASA’s work on SSP from the 1970s (NRC, 1981). The committee was tasked to perform a critical appraisal of this work, including identifying gaps in the DOE/NASA program and examining the results that the DOE/NASA study obtained. The study’s conclusions were not favorable for development of a satellite solar power system. The 1981 NRC report concluded that cost was a major prohibitive factor and the necessary technologies were not of the proper maturity. Estimates of the energy outlook at the time did not indicate that SSP would be a cost-competitive source of electrical energy for the next 20 years. The size and complexity of financing and managing the infrastructure that would be necessary would strain the abilities of the United States. International legal, political, and social acceptability caused by such issues as fear of possible health hazards could make SSP difficult or impossible for the United States to achieve. That earlier report concluded that no funds should be committed specifically to development of a satellite solar power system during the next decade. Realizing, however, that circumstances could change that would make more advanced satellite solar power systems an option in the more distant future, the 1981 NRC report also recommended vigorous investigation of technologies relevant to satellite solar power systems that were synergistic with the goals of other programs.

In August 1981, the U.S. Office of Technology Assessment (OTA) also published a report on the DOE/ NASA efforts that was unfavorable to continued work in SSP (OTA, 1981). According to the OTA report, too little was known about the technical, environmental, or economic aspects to make a sound decision on whether to continue further development and deployment of SSP. Under the circumstances prevailing at the time, OTA concluded that further research would be necessary before any decisions could be made. When the unfavorable assessments, high initial costs, and need for more research, development, and testing were combined with the drop in oil prices that began in 1984, the urgency that drove development of an SSP system largely evaporated, and work essentially stopped. There was little official interest until the mid-1990s.

In 1995, NASA took a fresh look at the feasibility, technologies, costs, markets, and international public attitudes regarding SSP. The Fresh Look study, published in 1997, found that much had changed (Feingold et al., 1997). Several promising concepts were identified as alternatives to the original 1979 reference concept. The study showed that great cost savings, for example, could be achieved over the 1979 reference concept by making use of modular, self-deploying units and on-orbit robotic assembly as opposed to the original concept, involving human-occupied, in-space construction bases. Modularization would also permit the use of smaller launch vehicles in place of a two-stage-to-orbit, reusable, heavy-lift launch vehicle that would require unique ground launch infrastructure. The study noted the critical importance of low-cost transportation to orbit and noted further that, although costs were still too high, the technology to lower launch cost to orbit was separately under development in other NASA programs (although it is uncertain if or when those programs will result in a new generation of launch vehicles or what improvements might be provided in terms of performance or cost). The study asserted that technologies and concepts involved in SSP could become more feasible if both government and commercial non-SSP applications were considered. Finally, the study noted that the market for SSP, though global in nature, might be uncertain for some time to come depending on how various nations’ policies treated SSP in comparison with other means of generating electricity (Feingold et al., 1997).

As a result of the Fresh Look study, both the U.S. Congress and the Office of Management and Budget became interested in SSP once more. NASA conducted a follow-on concept definition study in 1998. The result was funding of $22 million set aside for NASA to conduct the SERT program. In March 2000, the NASA Office of Space Flight (Code M) approached the NRC with a request to evaluate its technology investment strategy in space solar power with a view to determining whether or not the strategy that the agency had adopted would meet the program’s technical and economic objectives.

Although the current NRC committee neither advocates nor discourages SSP, it recognizes that significant changes have occurred since 1979 that might make it worthwhile for the United States to invest in either SSP or its component technologies. Improvements



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