Vol. 4 No. 6 September 11, 2000
Solar Power Satellites Desirable but Years Away
On September 7, 2000, the House Science Committeeäs Subcommittee on Space and Aeronautics held a hearing on Solar Power Satellites (SPS). First proposed in 1968, the concept involves the capturing of solar energy using gigantic photovoltaic arrays placed in geostationary orbit. The collected energy could be converted into electricity and beamed to Earth via a microwave beam for worldwide use. According to Subcommittee chairman Dana Rohrabacher (R-CA), the Subcommittee convened this hearing energy has once again become a major concern. Oil prices have soared. Rohrbacher indicated that those in his home state of California are experiencing frequent electrical shortages. In many parts of the world, people are burning off clean energy resources such as natural gas simply because they do not have a way to get these resources to markets. Rohrabacher insisted that "we should be looking for new, cleaner sources of energy." Rohrabacher believed that SPS is an alternative whose utility and economy was worth exploring. The Subcommittee last considered SPS in a 1997 hearing, after NASA had completed a study of the concept. Four witnesses supplied testimony on SPS at the hearing. Their input is summarized below.John C. Mankins, Manager, Advanced Concepts Studies, Office of Space Flight, NASA
Dr. Peter Glaser of Arthur D. Little invented the SPS concept in 1968, and since that time, NASA, industry, and the Department of Energy (DOE) have all conducted studies on SPS. A study conducted by DOE and supported by NASA between 1976 and 1980 indicated that a major SPS system, consisting of 60 satellites, would cost over $275 billion (FY 2000 dollars). According to Mankins, NASA revisited the SPS concept in 1995 "to determine whether or not technology advances since the 1970s might enable new SSP [space solar power] systems concepts that were more viable--both technically and programmatically." This "Fresh Look Study" concluded that since the 1970s, several promising SSP concepts had emerged due to recent technology advances, making space power systems far more viable than they had been in 1980. At the suggestion of the House Science Committee, NASA completed an SSP Concept Definition Study in 1998. Testing the results of the Fresh Look Study, the new study affirmed the improved viability of SSP and led to NASAäs development of strategic research and technology roadmaps for SSP technology development. Since 1999 NASA has been conducting the Space Solar Power Exploratory Research and Technology Program to further define both new systems concepts as well as the technical challenges of SSP. Led by NASAäs Marshall Space Flight Center and costing $22 million, the program should be completed by the end of this year, Mankins said. The preliminary results of NASAäs latest study indicate a number of challenges ahead for SSP systems in areas such as systems integration; solar power generation; power management and distribution; robotics assembly, maintenance, and servicing; platform and ground systems; transportation from Earth to orbit; and in-space transportation. Mankins also said that further study of terrestrial markets for SPS is required. Mankins said that NASA currently believes that technology advances and technology flight experiments and demonstrations needed to make space-based power a reality could occur by 2007. By the 2011-2012 time frame, NASA could be ready to demonstrate the technology for a 1-megawatt class SSP platform bus. Technology needed for a 1-2-gigawatt power SSP platform could be demonstrated between 2025 and 2035. Only after 2050, NASA predicts, would large-scale, in-space SSP platforms more powerful than 10 gigawatts become viable. Mankins acknowledged that the development cost of such systems would be substantial. NASAäs FY 2001 budget request does not include funding for SPS work.Ralph H. Nansen, President, Solar Space Industries
Nansen pointed to program size, cost, the uncertain safety of wireless energy transmission, and international implications as the chief obstacles to SPS development. He further emphasized that SPS would not become a reality in the present absence of low-cost, heavy lift space transportation. "The existing space transportation market has not been large enough to justify the huge development cost of a reusable heavy lift launch vehicle system," Nansen said. Citing the increasing world demand for energy, Nansen suggested that the U.S. government and industry should form a partnership to develop SPS. According to Nansen, the governmentäs primary role in such a partnership should be to provide leadership and funding to start the program, coordinate international agreements, support the development of high technology, multi-use infrastructure, and purchase the first operational satellite. Several government agencies, such as DOE, NASA, and the Departments of State and Commerce, would play a role in this effort. Industry would supply most developmental funding and design and develop the system. Nansen noted that the government should take several initial steps to aid the commercial development of SPS. Such measures, according to Nansen, should include:
Grey summarized the findings of an AIAA assessment of NASAäs recent SSP studies. He noted that the AIAAäs study comprised three aspects of SSP work:
Grey indicated that the AIAA found these areas worth examining for international cooperation: computer modeling; solar array technology development; wireless power transmission; research facilities; innovative concepts and technologies; multiple-use applications; and demonstrations. Grey noted that SPS was the topic of a workshop at the UNISPACE III meeting held in Vienna in 1999, where participants reached the conclusion that the concept could not be realized without international cooperation and worldwide acceptance. The AIAA recommended that an international organization such as the United Nations needs to work on resolving global concerns regarding SPS including health and safety requirements for a SPS system, frequency and orbital allocations for SSP satellites, and economic and market issues. The AIAA explored the use of SSP technologies in a number of applications including solar power generation, wireless power transmission, power management and distribution, and in-space transportation. According to Grey, SSP-enabling technologies could be used in a range of activities such as human space exploration, science and robotic exploration, national security missions, commercial space development, and terrestrial applications. The AIAA applauded NASAäs SSP study efforts for identifying and defining key technologies for SPS despite the programäs modest funding. "Perhaps the most important [result of NASAäs study] was the emergence and validation of a viable alternative to microwave power transmission: laser power beaming, at intensities that comply with current health regulations and at acceptable projected overall system efficiencies," Grey said. Like Nansen, Grey believes that the lack of low-cost, reliable space transportation is the major barrier to a space-based power system.
John Fini, Senior Associate, Strategic Insight, Ltd., (on behalf of Molly Macauley, Senior Fellow, Resources for the Future)
Fini submitted for the record the prepared statement of Macauley, who was unable to present her testimony due to illness. Fini made no comment on Macauleyäs written statement.
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