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Laying the Foundation for Space Solar Power: An Assessment of NASA’s Space Solar Power Investment Strategy Executive Summary NASA’S SPACE SOLAR POWER EXPLORATORY RESEARCH AND TECHNOLOGY (SERT) PROGRAM The National Aeronautics and Space Administration’s Space Solar Power (SSP) Exploratory Research and Technology (SERT) program1 was charged to develop technologies needed to provide cost-competitive ground baseload electrical power2 from space-based solar energy converters. In addition, during its 2-year tenure, the SERT program was also expected to provide a roadmap of research and technology investment to enhance other space, military, and commercial applications such as satellites operating with improved power supplies, free-flying technology platforms, space propulsion technology, and techniques for planetary surface exploration. NASA focused the SERT effort3 by utilizing the definition of a “strawman” or baseline SSP system that would provide 10 to 100 GW to the ground electrical power grid with a series of 1.2-GW satellites in geosynchronous Earth orbit (GEO). For each of the major SSP subsystems, NASA managers developed top-level cost targets in cents per kilowatt-hour (kW-hr) that they felt would have to be met to deliver baseload power at a target of 5 cents/kW-hr. The result of this work was a set of time-phased plans with associated cost estimates that provided the basis for a technology investment strategy. Central to the SERT program was a series of five or six experimental flight demonstrations of progressively larger power-generation capacity, called Model System Categories. These demonstrations will serve as focal points for the advancement of SSP-related technologies and will provide advancements in technologies benefiting other nearer-term military, space, and commercial applications. NASA made extensive use of cost and performance modeling to guide its technology investment strategy. 1 The SERT program was established in FY 1999 and continued through FY 2000 by U.S. congressional appropriation. An additional appropriation was also funded for SSP Research and Technology (SSP R&T) for FY 2001. Decisions on internal NASA budget allocations for FY 2002 were pending during review and publication of this report. During recent agency wide realignments, future SSP programs may be included within other NASA initiatives. 2 Baseload power is defined as the power available to an area at a constant level during a 24-hour period. For example, most of the power available to residential and business areas is considered baseload power. 3 Throughout this report the terms “SERT program” and “SERT effort” refer to both the 2-year Space Solar Power Exploratory Research and Technology (SERT) program during FY 1999 and 2000 and the follow-on effort in FY 2001, the SSP Research and Technology (SSP R&T) program. The terms “SSP program” and “SSP effort” refer to any planned future program in SSP technology development.
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Laying the Foundation for Space Solar Power: An Assessment of NASA’s Space Solar Power Investment Strategy COMMITTEE ASSESSMENT The current SSP technology program4 is directed at technical areas that have important commercial, civil, and military applications for the nation. A dedicated NASA team, operating with a minimal budget, has defined a potentially valuable program—one that will require significantly higher funding levels and programmatic stability to attain the aggressive performance, mass, and cost goals that are required for terrestrial baseload power generation. Nevertheless, significant breakthroughs will be required to achieve the final goal of cost-competitive terrestrial baseload power. The ultimate success of the terrestrial power application depends critically on dramatic reductions in the cost of transportation from Earth to GEO. Funding plans developed during SERT are reasonable, at least during the 5 years prior to the first flight demonstration in 2006 (see Table ES-1). The committee is concerned, however, that the investment strategy may be based on modeling efforts and individual cost, mass, and technology performance goals that may guide management toward poor investment decisions. Modeling efforts should be strengthened and goals subjected to additional peer review before further investment decisions are made. Furthermore, SERT goals could be accomplished sooner and potentially at less cost through an aggressive effort by the SERT program to capitalize on technology advances made by organizations outside NASA. COMMITTEE RECOMMENDATIONS Recommendations to the NASA SSP program can be generally categorized by three main imperatives: (1) improving technical management processes, (2) sharpening the technology development focus, and (3) capitalizing on other work. Figure ES-1 provides a snapshot of the committee’s key recommendations. Each recommendation is numbered to correspond to the text section in which it is discussed. Improving Technical Management Processes NASA’s SERT program’s technical management processes need to be improved. Currently the program TABLE ES-1 Proposed Space Solar Power Program Resources Allocation, FY 2002 to FY 2006 (millions of dollars) Investment Area FY 2002 FY 2003 FY 2004 FY 2005 FY 2006 Systems integration, analysis, and modeling 5 7 8 8 8 Total technology development 73 92 128 149 154 Technology flight demonstrations 10 25 75 125 150 Total investment 88 124 211 282 312 SOURCE: Adapted in part from “Strategic Research and Technology Road Map.” Briefing by John Mankins and Joe Howell, National Aeronautics and Space Administration, to the Committee for the Assessment of NASA’s Space Solar Power Investment Strategy, National Research Council, Washington, D.C., December 14, 2000. has developed a set of integrated roadmaps containing goals, lists of technology challenges and objectives, and a strawman schedule of program milestones that guide technology investment. Appendix C contains a sample set of roadmaps that have been developed for the entire SERT program and each of the program’s 12 individual technology areas. The roadmaps’ performance, mass, and cost goals are tied to research and technology initiatives in various technical areas necessary for SSP. Unfortunately, the committee did not find adequate traceability between the goals at the system level and those at the subsystem level. Integral to the milestone schedule are a series of downselect opportunities that precede each flight test demonstration. However, there is no formal mechanism at this point in the program to guide these downselect decisions. The committee has also seen evidence that the current SERT program’s roadmaps do not adequately incorporate the planned advances in low-cost space transportation, both Earth-to-orbit and in-space options. Since advancements in space transportation are key to the SSP program’s ultimate success, the timing and achievement of technology advances and cost and mass goals by the separate space transportation programs within NASA should be included directly in the SSP roadmaps. A periodic revamping of the roadmaps should be done based on the achievements of NASA in space transportation. SSP 4 This assessment evaluates the SERT program and the followon SSP R&T efforts through December 15, 2000. Program changes after that date are not included.
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Laying the Foundation for Space Solar Power: An Assessment of NASA’s Space Solar Power Investment Strategy FIGURE ES-1 Key recommendations to the NASA SSP program. Each recommendation is numbered to correspond to the text section in which it is discussed.
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Laying the Foundation for Space Solar Power: An Assessment of NASA’s Space Solar Power Investment Strategy program technology investments, flight test demonstrations, and full-scale deployment should be rescheduled accordingly. Recommendation: NASA’s SSP program should improve its organizational and decision-making approach by drawing up a written technology development plan with specific goals, dates, and procedures for carrying out technology advancement, systems integration, and flight demonstration. The SSP program should also establish a consistent process to adjudicate competing objectives within the program and specifically include timing and achievement of technology advances in robotics and space transportation in the roadmaps. NASA’s use of an architecture cost goal estimate based on power costs in the future electricity market is appropriate and commended. As SSP development progresses, however, the architecture cost goal should be adjusted periodically to reflect changes in expectations about future power markets, environmental costs, and other social costs that may arise during development. The NASA SERT program began development of rigorous modeling and system analysis studies, which were used as a basis for technology and programmatic investments. The approach could be developed, with improvements, into one useful technique for determining program priorities. The committee discovered during its meetings that many of the modeling inputs were suspect and that more refinement and better validation were necessary. Recommendation: The SSP program should review its technology and modeling assumptions, subject them to peer review, and modify where indicated. A single SSP concept should be rigorously modeled, incorporating technology readiness levels and involving industry in conceptual design, as a means to improve the credibility of the model input and output but not to prematurely select a single system for ultimate implementation. The SERT program’s oversight advisory structure (called the Senior Management Oversight Committee) includes representatives from various internal NASA organizations, industry, and academia. Further leveraging of technology expertise, management expertise, and funding could be obtained by including representatives from other organizations as well. Additional input would be beneficial from traditional aerospace companies, the Electric Power Research Institute (EPRI), utilities, and other government agencies (particularly the Department of Defense [DOD]/U.S. Air Force, the Department of Energy [DOE], and the National Reconnaissance Office [NRO]). These additions will provide periodic input on the investment strategy and program roadmap and provide further opportunities to validate technological and economic input into the performance and cost models. Individual research and technology working groups have also been established to address planning and technology development in specific technology areas. It would be beneficial to expand these activities. Recommendation: The current SSP advisory structure should be strengthened with industry (including EPRI and electric utility) representatives plus experts from other government agencies (particularly DOD/Air Force, DOE, and NRO) in order to validate technological and economic inputs into the performance and cost models. Also, due to the wide breadth of technologies related to SSP, the program should establish similar advisory committees for specific technologies in addition to the research and technology working groups currently utilized by the program. In designing a full-scale SSP system, an environmental impact analysis must be performed that considers human health issues, environmental impact both on Earth and in space, and possible risks to the SSP system itself. Currently the SERT program has placed only a small priority on this area. However, the committee believes that environmental, health, and safety issues should be considered with more emphasis early in the program. Recommendation: The SSP program should expand its environmental, health, and safety team in order to review SSP design standards (beam intensity, launch guidelines, and end-of-life policies); assess possible environmental, health, and safety hazards of the design; identify research if these hazards are not fully understood; and consider legal and global issues of SSP (spectrum allocation, orbital space, etc.). One approach would be to involve an international organization such as the International Astro-
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Laying the Foundation for Space Solar Power: An Assessment of NASA’s Space Solar Power Investment Strategy nautical Federation Space Power Committee in such studies. Recommendation: Public awareness and education outreach should be initiated during the earliest phases of an SSP program to gain public acceptance and enthusiasm and to ensure ongoing support through program completion. Sharpening the Technology Development Focus Key Technologies for SSP The SERT program must focus its technology development. Currently, the program is funding research in a myriad of technologies that may have potential use in a full-scale SSP system. This research is a valuable endeavor in advancing SSP-related technologies and in determining the extent of development necessary for individual technologies to reach technology readiness levels that can be certified for space flight. The committee recommends that the current long-term focus of the program remain. However, due to current funding levels, most investments in individual technologies are much smaller than SERT program managers feel are necessary for adequate research and development of SSP technologies. Many investments are in areas where the utility and power industry should be the lead investor. Under current funding constraints, most of the investment should be focused on technologies that have nearer-term applications in space or that may be applied to other Earth applications. Specifically, the committee believes that the greatest benefit would be obtained by investing in several key enabling technologies, which include solar power generation; wireless power transmission; space power management and distribution (SPMAD); space assembly, maintenance, and servicing; and in-space transportation. Without substantial advances in these critical areas, a viable, commercial full-scale SSP system that meets NASA’s cost goals may be unattainable in the time frame envisioned by the program. Solar Power Generation Solar power generation is in the midst of an exciting period of advancement. NASA must collaborate with DOD, DOE, and commercial efforts to avoid undue duplication in research and improve overall effectiveness. Successful attainment of the aggressive cost and mass goals that must be met if SSP is to provide commercially competitive terrestrial power will require that NASA focus on high-reward, high-risk solar array research. Cost-competitive SSP terrestrial electric power will require major technology breakthroughs in solar power generation. Wireless Power Transmission Investments in wireless power transmission will also need to be focused on more specific areas in the near-term time frame. Currently, the program is funding work on several different options, both microwave and laser. As long as budget levels remain modest, NASA should select one of the three proposed microwave options, along with the laser option, for further funding. Because of the potential benefits to nearer-term space applications, investment in the laser option should be aimed at bringing this technology to the same level of maturity as the microwave option. Ground demonstrations of point-to-point wireless power transmission should be conducted. NASA should also study the desirability of ground-to-space and space-to-space demonstrations. Space Power Management and Distribution SPMAD is a major contributor to the mass and cost of SSP system designs. Significant investment should be made to reduce the mass and cost of the components to be applied in space while increasing their efficiency and maximum operating temperature. Investments should also be made with companies that are experienced in producing power management and distribution (PMAD) and wireless power transmission components and that will one day have the capability to provide high-volume manufacturing at low cost with high performance and high reliability. Space Assembly, Maintenance, and Servicing As currently envisioned by the SERT program, autonomous robots will accomplish space assembly, maintenance, and servicing. This will require significant advances in the state of the art of robotics. NASA’s SSP program should perform additional systems studies directed at determining the optimal mix of humans and machines and to allow for substantial human involvement on the ground and possibly in space. Focused investments in advancing robotics are expected to have benefits well beyond SSP. In-Space Transportation Space transportation is key to the deployment of any SSP system. In NASA’s initial studies, approximately one-half of the system cost was allocated to ground-to-low-Earth-orbit (LEO)
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Laying the Foundation for Space Solar Power: An Assessment of NASA’s Space Solar Power Investment Strategy transportation. Earth-to-orbit transportation costs and reliability will be crucial to the deployment of any future commercial SSP system. However, ground-to-LEO transportation is covered by the separate NASA Space Launch Initiative (SLI) program and is outside the scope of this assessment. LEO-to-GEO transportation has little funding in other parts of NASA, so it has been included as part of the SERT program. Chemical, electric, and hybrid propulsion systems are under consideration. In-space transportation is a critical technology that should receive significant investment. Recommendation: The NASA SSP program should invest most heavily in the following key enabling technologies, mainly through high-payoff, high-risk approaches: (1) solar power generation (in collaboration with DOD/USAF and DOE to avoid duplication); (2) wireless power transmission; (3) space power management and distribution; (4) space assembly, maintenance, and servicing; and (5) in-space transportation. The SSP program should not invest research and development funds in ground PMAD technologies, ground-based energy storage, or platform system technologies. Utilities, industry, and other government programs already have significant investments in those areas. Recommendation: Under current funding constraints, the SSP program should devote a large portion of its efforts to technologies that have nearer-term applications (e.g., low-mass solar arrays) while continuing to develop technology and concepts for long-term terrestrial baseload power applications. Any long-term, large program such as SSP must strive to maintain a balance between near- and far-term objectives and goals. Significant differences in technology development would occur if either short- or long-term goals are considered most important. The committee has seen this struggle within the SERT program. Long-term progress must be made in many technology areas before space solar power can become economically viable as a full-scale terrestrial baseload power source. However, due to budget realities and the need to prove near-term success, a program must also make contributions to advancing nearer-term technologies that are applicable to many different programs. In several technology areas, the committee sees merit in suggesting that the SSP program, as currently funded, invest in next-generation, revolutionary, high-payoff, high-risk concepts. Each of the 11 individually numbered technical sections in Chapter 3 discusses appropriate long-term recommendations for the program. Systems Integration Systems integration is commonly applied during the development phase of a product. However, due to the large number of SSP subsystems and their strong interactions with one another, it should be of vital importance during early SSP technology development. NASA allocated a portion of its SERT funding to developing an overall SSP concept and cost model that includes system cost, mass, and performance targets. Although not yet complete or independently validated, this model has been used as a tool to predict delivered baseload power costs, assuming that various technology goals have been achieved. The committee endorses this methodology as one useful technique for assigning technology investment priorities and urges that its development continue as an indicator of the relative payoff from technology investments. The model is still coarse at this time, and the scope and detail should be broadened so that cost and mass targets can be accurately allocated down to the component level. It appears to the committee that many of these goals for launch costs and for system mass and cost must be significantly lower than those currently being used by the NASA team if the system is to produce competitive terrestrial power. Sensitivity studies should be an integral part of any large-scale modeling effort in order to quantify the impacts of departures from the nominal input metrics, many of which are simply assumptions for the SERT program at this time. Nominal input metrics should be developed in consultation with acknowledged experts in SSP-related technology fields to assure quality and accuracy of data. Recommendation: The SSP team should broaden the scope and detail of the system and subsystem modeling (including cost modeling) to provide a more useful estimate of technology payoff. The models should incorporate detailed concept definitions and include increased input from industry and academia in the specification of model metrics. The costs of transportation, assembly, checkout, and maintenance must also be included in all cost comparisons to properly evaluate alternative technology investment options.
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Laying the Foundation for Space Solar Power: An Assessment of NASA’s Space Solar Power Investment Strategy Recommendation: The SSP program should review its technology and modeling assumptions, subject them to peer review, and modify where indicated. A single SSP concept should be rigorously modeled, incorporating technology readiness levels and involving industry in conceptual design, as a means to improve the credibility of the model input and output but not to prematurely select a single system for ultimate implementation. Verification of SSP technology and the integration and testing of hardware and software are necessary before deployment of any SSP system. A combination of new modeling techniques and new design methods, which adaptively accommodate errors in predicted performance and function, may be necessary. The committee saw little evidence of the depth of modeling necessary for such complex space platforms but expects that the effort will increase as candidate designs are chosen. Recommendation: The SSP program should increase investments in developing spacecraft integration and testing so that the performance of SSP satellites can be verified with a minimum of ground or in-space testing. This may include the development of specialized integration, test, and verification methodologies for SSP spacecraft. Technology Demonstration A set of technology flight demonstrations (TFDs) is key to NASA’s technology demonstration plan for SSP. Use of these TFDs is commended by the committee as an excellent means of testing available technologies before full-scale integration and deployment. Extensive use of ground demonstration milestones was not observed by the committee in the SERT roadmap. Use of ground demonstrations would provide a lower-cost mechanism to test new technologies before flight. Use of currently available in-space testing mechanisms would also be beneficial to any future SSP program. The current infrastructure on the International Space Station (ISS) could provide an excellent platform for technology demonstration activities. However, because the LEO at which ISS is located may be significantly different from the GEO environment in many ways, demonstration plans should include methodologies that account for the differences between these orbits. Additionally, testing of new robotics and assembly techniques should be incorporated into all flight test demonstrations to further test advanced technologies. Recommendation: The SSP program should continue the use of technology flight demonstrations to provide a clear mechanism for measuring technology advancement and to provide interim opportunities for focused program and technology goals on the path to a full-scale system. Recommendation: The SSP program should define additional ground demonstration milestones to be conducted prior to the far more expensive flight tests in order to test advanced technologies and system integration issues before planned downselects of flight-demonstration technologies occur. Recommendation: NASA should seriously consider utilizing the International Space Station as a technology test bed for SSP during the first set of flight demonstration milestones. Such tests would leverage ISS technology and infrastructure, be independent of new advances in space transportation, and provide an opportunity to test autonomous robotic systems. Recommendation: The SSP program should perform near-term flight demonstrations of robotic assembly techniques, as well as robotic maintenance and servicing operations. Robotics testing should be incorporated into all SSP flight demonstrations, if possible and as applicable. Capitalizing on Other Work NASA’s SSP program must capitalize on other work. Even if the SSP funding level increases dramatically, the technical challenges faced by NASA’s SSP program will require effective utilization of all resources currently being expended on SSP-related technologies in a variety of government agencies (DOD and DOE), commercial entities, and academia, both in the United States and abroad. This is especially true in reducing the cost of Earth-to-orbit transportation. NASA’s SLI is currently working on cost reduction of transportation to LEO. The SSP program must convey program information to the SLI on its transportation cost goals, optimal payload, mass, packaging, launch rate, and reliability requirements and request that a credible plan be defined by SLI to help achieve these goals. In the case of the pro-
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Laying the Foundation for Space Solar Power: An Assessment of NASA’s Space Solar Power Investment Strategy posed use of electric propulsion from LEO to GEO, NASA will need to collaborate with and capitalize on the expertise of commercial firms working on electric propulsion and other in-space transportation options. Recommendation: The SSP program should begin discussions between its management and that of the NASA Space Launch Initiative, so that future milestones and roadmaps for both programs can reinforce one another effectively. This discussion should include specific information on SSP space transportation needs, including cost goals, timelines for deployment, optimal payload mass, packaging requirements, launch rates, and reliability requirements. Recommendation: The SSP program should encourage expansion of the current in-space transportation program within NASA and interact with its technical planning to ensure that SSP needs and desired schedules are considered. Recommendation: The SSP program should increase coordination of industry, academic, and other NASA and non-NASA government investments in advanced in-space transportation concepts, particularly in the areas of electric, solar-electric, magnetohydrodynamic, ion, and solar-thermal propulsion. The components necessary for the ground PMAD subsystem are similar to those used for terrestrial photovoltaic systems. Substantial research and development work is currently supported by the National Center for Photovoltaics, as well as several commercial entities that provide PMAD components for terrestrial photovoltaic applications. In the case of the solar power generation components (i.e., photovoltaics), programs are currently under way in the Air Force to develop high-efficiency, high-specific-power solar cells. The work of the DOE’s National Renewable Energy Laboratory in thin-film solar cells will also be important to the program. Recommendation: NASA should expand its current cooperation with other solar power generation research and technology efforts by developing closer working relationships with the U.S. Air Force photovoltaics program, the National Center for Photovoltaics, industry, and the U.S. government’s Space Technology Alliance. Although it may be beyond the means of any one country to fund the research, development, and implementation of SSP, these tasks could be more achievable with international cooperation, which would allow NASA to profit from the work of experts worldwide as well as to contribute its own expertise. Recommendation: NASA should develop and implement appropriate mechanisms for cooperating internationally with the research, development, test, and demonstration of SSP technologies, components, and systems. Many technologies for SSP (and other space missions) are not currently on the critical path for any near-term NASA mission. Hence, little funding is available that can be leveraged by SSP to develop these technologies. Without this leverage, it is unlikely that the SSP program can be the sole funding source for such technologies. Examples of such technologies are free-flying robotic servicers, specific space structures, reusable in-space transportation, and certain improvements in thermal materials and management and in power management and distribution. While it is beyond the purview of this study to specifically recommend funding increases for programs other than the SSP program assessed in this report, the committee believes that such technologies are important to the ultimate success of SSP. SUMMARY The committee has examined the SERT program’s technical investment strategy and finds that while the technical and economic challenges of providing space solar power for commercially competitive terrestrial electric power will require breakthrough advances in a number of technologies, the SERT program has provided a credible plan for making progress toward this goal. The committee makes a number of suggestions to improve the plan, which encompass three main themes: (1) improving technical management processes, (2) sharpening the technology development focus, and (3) capitalizing on other work. Even if the ultimate goal—to supply cost-competitive terrestrial electric power—is not attained, the technology investments proposed will have many collateral benefits for nearer-term, less-cost-sensitive space applications and for nonspace use of technology advances.
Representative terms from entire chapter: