In the late 1960s, Dr. Peter Glaser of Arthur D. Little invented a fundamentally new approach to global energy: the Solar Power Satellite (SPS). The basic concept of the SPS is quite elegant: a large platform, positioned in space in a high Earth orbit continuously collects and converts solar energy into electricity. This power is then used to drive a wireless power transmission (WPT) system that transmits the solar energy to receivers on Earth. Because of its immunity to nighttime, to weather or to the changing seasons, the SPS concept has the potential to achieve much greater energy efficiency than ground based solar power systems (in terms of utilization of fixed capacity). The SPS concept has been the subject of numerous national systems studies and technology development efforts during the 40 years from 1970 to 2010. The International Academy of Astronautics (IAA) has conducted the first broadly based international study of the concept of space solar power.
Three highly promising SPS platform concepts were examined in some detail by the IAA study; the results of this examination provide a framework for the remainder of the report, including the technology assessment, market assessment, etc. All three of the cases examined were geostationary Earth orbit-based SPS concepts; these were: (1) an updated version of the microwave wireless power transmission (WPT) 1979 SPS Reference System concept, involving large discrete structures (e.g., solar array, transmitter, etc.) assembled by a separate facility in space; (2) a modular electric / diode array laser WPT SPS concept, involving selfassembling solar power-laser-thermal modules of intermediate scale; and (3) a extremely modular microwave WPT SPS “sandwich structure” concept, involving a large number of very small solar power-microwave-thermal modules that would be robotically assembled on orbit. Several alternative SSP concepts were also identified but not analyzed, including the low Earth orbit-based “SunTower” SPS concept, lunar solar power, and others.
There are a number of extremely important systems other than the SPS platform itself that must be pursued to provide essential support for the development and operation of SPS platforms. The supporting systems that were examined included (1) Earth-to-orbit (ETO) transportation; (2) affordable in-space transportation; (3) space assembly, maintenance and servicing; and, (4) ground energy and interface systems. A longer term supporting system option was also examined: (5) in-space resources and manufacturing.
In looking toward rest of this century, it is obviously impossible to predict with confidence how the many issues that will frame the market for SPS will unfold. In order to provide a reasonable, but not exhaustive framework, the IAA identified four strategic scenarios for the future that would greatly affect potential SSP/SPS markets and economics. These were: (1) Scenario Alpha – “Business as Usual Works Out” (i.e., conventional and/or available renewable energy sources prove to be capable of meeting future demand, and no adverse changes occur in Earth’s climate); (2) Scenario Beta – “The Frog Gets Cooked” (i.e., the global economy does not deploy massive new renewable sources, and dramatic negative changes in Earth’s climate result); (3) Scenario Gamma – “Fossil Fuels Run Out” (i.e., the global economy does not deploy massive new renewable sources and peak oil, peak gas and peak coal occurs sooner than expected); and, (4) Scenario Delta – “Green Policies Work” (i.e., the deployment of new renewable energy sources is accelerated and succeeds in forestalling changes to Earth’s climate result).
Findings and Recommendations
The successful development and market-competitive deployment of any major new energy technology requires decades to accomplish. Historical examples include coal, oil, electricity, natural gas, etc. It is likely that space solar power (SSP) will be no different. As noted, the original invention of SPS occurred in the late 1960s, and the advancement of specific (e.g., wireless power transmission) and relevant technologies (e.g., reusable launch vehicles) has continued during the subsequent 40 years. As of 2010, the fundamental research to achieve technical feasibility for the SPS was already accomplished. Whether it requires 5-10 years, or 20-30 years to mature the technologies for economically viable SPS now depends more on (a) the development of appropriate platform systems concepts, and (b) the availability of adequate budgets. Based on the results of the IAA assessment of the concept of solar energy from space, the International Academy of Astronautics makes the following findings and offers the associated recommendations regarding the concept of future
space solar power for markets on Earth.
Finding 1: Fundamentally new energy technologies clearly appear to be needed during the coming decades under all examined scenarios – both to support continued (and sustainable) global economic growth, and for reasons of environmental/climate concerns. Solar energy from space appears to be a promising candidate that can contribute to address these challenges.
Finding 2: Solar Power Satellites appear to be technically feasible as soon as the coming 10-20 years using technologies existing now in the laboratory (at low- to moderate- TRL) that could be developed / demonstrated (depending on the systems concept details).
• Finding 2a: There are several important technical challenges that must be resolved for each of the three SPS systems types examined by the IAA study.
• Finding 2b: The mature (high-TRL) technologies and systems required to deploy economically viable SPS immediately do not currently exist; however, no fundamental breakthroughs appear necessary and the degree of difficulty in projected R and D appears tractable.
• Finding 2c: Very low cost Earth to orbit transportation is a critically needed supporting infrastructure in which new technologies and systems must be developed to establish economic viability for commercial markets.
Finding 3: Economically viable Solar Power Satellites appear achievable during the next 1-3 decades, but more information is needed concerning both the details of potential system costs and the details of markets to be served.
• Finding 3a. SPS do appear economically viable under several different scenarios for future energy markets, including potential government actions to mediate environment/climate change issues.
• Finding 3b. The economic viability of particular Solar Power Satellite concepts will depend upon both the markets to be served, and the successful development of the technologies to be used (including required levels of performance (i.e., key figures of merit for SPS systems).
• Finding 3c: The potential economic viability of SPS has substantially improved during the past decade as a result of the emergence both of government incentives for green energy systems, and of “premium niche markets”.
• Finding 3d. Establishing the economic viability of SPS will likely require a step-wise approach, rather than being achieving all at once – in particular SPS platform economics, space transportation economics, in-space operations economics, integration into energy markets, etc., will likely require iterative improvements to build confidence and secure funding for further developments.
• Finding 3e. Given the economic uncertainties in developing and demonstrating SPS technologies and systems and the time required, it is unlikely that private sector funding will proceed alone; i.e., government involvement and funding support is likely needed.
Finding 4: An in-depth end-to-end systems analysis of SSP/SPS is necessary to understand more fully the interactions among various systems / technologies for different concepts and markets; however, no such study has been performed since the conclusion of NASA’s Fresh Look Study in 1997.
• Finding 4a: Scenario-based study approaches can be extremely useful in examining prospective markets for visionary future systems such as SPS, but must provide sufficient detail to enable one to distinguish from among various SPS systems options.
• Finding 4b: Special attention appears needed to refresh understanding of prospects for space applications of SSP systems and technologies, with attention to the enabling role that low-cost electrical power in roughly the megawatt range could play for ambitious future space missions and markets.
Finding 5: Low-cost Earth-to-orbit transportation is an enabling capability to the economic viability of space solar power for commercial baseload power markets.
• Finding 5a: Extremely low cost ETO transportation systems appear to be technically feasible during the coming 20-30 years using technologies existing in the laboratory now (at low- to moderate- TRL) that could be developed / demonstrated (depending on the systems concept details). However, the technologies required for this future space capability are not sufficiently mature for system development to begin at present.
• Finding 5b: Acceptable ETO systems for future SPS must be “environmentally benign” – i.e., space transportation infrastructures to launch the satellites cannot result in harmful pollution of the atmosphere.
Finding 6: Systems studies are not enough. Technology Flight Experiments (TFEs) to test critical technology elements and Technology Flight Demonstrations (TFD) that validate SPS systems concepts to a high level of maturity (“TRL 7”3) appear to be essential in order to build confidence among engineers, policy makers, and the public and allow space solar power technology maturation and SPS deployment to proceed.
• Finding 6a: The International Space Station (ISS) appears to represent a highly attractive potential platform at which various SSP and related technology flight experiments (TFEs) could be performed.
• Finding 6b: Free flying spacecraft appear to be an attractive option for selected SSP TFEs and systems level demonstrations.
Finding 7: Architectural approaches that most efficiently and seamlessly integrate energy delivered from SPS into existing terrestrial energy networks are likely to be the most successful. (The same is true for any transformational new energy technology.)
Finding 8: The SPS concept is sufficiently transformational and entails enough technical uncertainties such that major systems level in-space demonstrations will be necessary to establish technical feasibility, engineering characteristics and economical viability before any organization is likely to proceed with full-scale development.
• Finding 8a. The likely investment in technology maturation, hardware development and system deployment for a very low-cost, highly reusable space transportation (HRST) system will require some 10s of billions of dollars ($, US). If the SPS concept is the sole – or even a significant – market justification for such a development, then it is likely that a large-scale, pilot plant type demonstration of the SPS to be launched will be required prior to a government and/or commercial commitment to fielding HRST systems or supporting infrastructure.
• Finding 8b. In-space systems and infrastructures that will support SPS deployment, assembly, servicing, etc. will be intimately related to the detailed designs and characteristics of the SPS platform, and to the design of supporting ETO systems (see Finding above). Such in-space systems will likely need to be developed and demonstrated in tandem with, if not prior to, the implementation of an SPS pilot plant demonstration.
Finding 9: A variety of key policy-related and regulatory issues must be resolved before systems-level demonstrations – particularly space based tests – of SPS and WPT can be implemented.
• Finding 9a. Spectrum management is an issue of particular importance that must be addressed early due to the time-consuming international processes that are in place vis-à-vis use of the electromagnetic spectrum and orbital slot allocations.
• Finding 9b. A number of operational issues that are related to international cooperation and coordination, including WPT transmission safety requirements, orbital debris generation and management, etc., must also be addressed early.
• Finding 9c. Policy related and regulatory issues will require considerable time to resolve, making the need to begin discussions in a timely way very pressing, particularly for SPS and related technology in-space tests and demonstrations.
Based on the results of the IAA assessment of the concept of space solar
power, the Academy offers the following recommendations for the consideration of the international community.
Recommendation 1: Both government-supported and commercially funded SSP systems analysis studies should be undertaken that have sufficient end-to-end breadth and detail to fully resolve the R and D goals and objectives that must be achieved to establish the viability of SSP.
• Recommendation 1a: Where possible, SSP and related systems analysis studies recommended should be coordinated among various countries and between industry and government agencies.
• Recommendation 1b: It is recommended that focused and rigorous market studies should be included in future integrated /end-to-end SPS systems studies; a scenario-based approach should be considered as a key element of such studies. In addition, such studies should include more detailed analysis of “premium niche markets” in various countries and/or for specific customers.
• Recommendation 1c: Future systems analysis / market studies should examine explicitly the potential integration of SPS / WPT concepts into existing (or projected) terrestrial energy networks. These studies should involve additional non-aerospace sector experts (for example, from the energy and utility sectors).
• Recommendation 1d: Future systems studies should examine in greater detail the comparison of SPS with other energy technologies for various market opportunities, including both nearer-term technologies (such as ground solar) and farther term technologies (such as fusion).
• Recommendation 1e: Future systems studies should address a range of detailed issues, including policy and economic considerations, GEO orbital slot availability, operational issues (e.g., in-space assembly / infrastructure, SPS reliability and failure considerations), and orbital debris. These studies should examine Earth-to-orbit and in-space transportation issues carefully.
• Recommendation 1f: Future systems studies should place appropriate emphasis on better life cycle cost (LCC) estimates of SPS, including examining the impact of new models of large volume production of space systems.
Recommendation 2: Future economic analyses should examine the potential role of non-space related government and international funding agencies in contributing to the development of SPS.
Recommendation 3: Government and commercial organizations should consider undertaking SSP and related technology R&D, including platform systems and supporting infrastructures (e.g., ETO, in-space transportation, in-space operations).
• Recommendation 3a: The International Space Station (ISS) should be considered as a potential platform on and from which a number of useful SSP and related technology flight experiments and tests could be performed.
• Recommendation 3b: Specific space solar power technology R&D activities – such as ground demonstrations and technology flight experiments – should be planned so as to best advance the overall state-of-the-art for SSP, and the results communicated as broadly as possible (consistent with restrictions due to intellectual property or
Recommendation 3c: It is recommended that as studies and technology R&D go forward that are directed toward SPS, WPT and related applications, there should be supporting research concerning WPT health and safety issues.
• Recommendation 3d: SSP technology development efforts should explicitly seek prospective nearer-term applications in support of international space goals and programs, such as space exploration.
• Recommendation 3e: Where possible, governments and commercial sector players should consider the formation of public-private partnerships to implement SSP technology development efforts; government agencies in particular should take steps to enable to encourage the formation of such partnerships.
Recommendation 4: The necessary policy and regulatory steps to enable SPS/WPT and related R&D to be conducted – leading to systems-level demonstrations – should be undertaken in the near term by government, commercial and other interested organizations.
• Recommendation 4a: It is recommended that particular attention should be paid to the allocation of spectrum for WPT technology development efforts and later system applications.
• Recommendation 4b: It is recommended that the formation of
Public-Private Partnerships to pursue SSP technology maturation and
system developments should be considered and encouraged where appropriate.
Recommendation 5: International organizations, such as the International Academy of Astronautics, should play a constructive role in fostering and guiding future SSP/SPS studies, technology developments and policy deliberations.