Laying the Foundation for Space Solar Power An Assessment of NASA's Space Solar Power Investment Strategy (2001) / Chapter Skim
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3 Individual Technology Investment Evaluations
3 Individual Technology Investment Evaluations
Pages 29-62
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NASA has established a working process for integrating the SERT effort. This program decision-making and organization process to integrate SERT technology working groups and task forces has been well coordinated and has succeeded in advancing the SERT program definition during the past 2 years.
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30 o o ~: ~ - : ~ lo · ' :: ~ .¢s ~ ~ a.
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commercial sponsors and their funding sources. The committee considers that the present SERT cost and performance targets for several of the technologies are beyond present credibility, particularly in solar power generation (SPG)
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The adaptive approach may require the developLAYING THE FOUNDATION FOR SPACE SOLAR POWER ment of self-healing structures, self-tuning adaptive control systems, autonomous robots, and failure-tolerant structural concepts. Some of these developments may be very far into the future, requiring rigorous, long-term investment before they will yield practical success.
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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. Capitalizing on Other Work The committee realizes that a full-scale SSP system is greatly dependent on future space transportation technologies not yet defined.
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The SSP program should review previous modeling efforts and integrate successful methods, as appropriate. For example, it does not appear to the committee that the current SERT program has looked for lessons learned from modeling efforts used during the 1970s space solar power efforts (Hazelrigg, 1977)
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Technical Performance Goals Needed for Economic Competitiveness Successful development of an economically viable SSP will require substantial leaps in development of space solar array, PMAD, thermal control, wireless transmission, and launch technologies. However, improvements in PV solar array technologies alone will not enable SSP to be economically competitive with terrestrial utility electricity.
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It is important to note that there is actually little difference between space and terrestrial PV technologies. There is virtually no difference in the electrically active part of the PV cell that controls conversion LAYING THE FOUNDATION FOR SPACE SOLAR POWER efficiency, called the pin junction.
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Recommendation 3-2-2 [also 2-1-X] : NASA should expand its current cooperation with other solar power generation research and technology efforts by developing closer working relationships with the U.S.
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Technical Performance Goals Needed for Economic Competitiveness The NASA subsystem team has adopted the folLAYING THE FOUNDATION FOR SPACE SOLAR POWER lowing goals for this SPMAD subsystem: end-to-end efficiency greater than 94 percent, mass less than 2 kg/ kW (power density greater than 500 W/kg) , and a cost of less than $300/kW (30 cents/W)
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A few percentage points of improvement in PMAD efficiency will translate to a larger percentage point reduction in SSP mass and cost, reduced system heat load, and thus fewer thermal management problems. However, large breakthroughs should not be expected but, rather, slow, incremental progress.
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For the baseline system at 1.2-GW output to the utility interface, this results in a dense concentration of transmitting elements in a 500-m-diameter circle. LAYING THE FOUNDATION FOR SPACE SOLAR POWER Laser Option The laser option will probably operate in the nearinfrared spectrum at 1.03 ,um (Er:YAG laser)
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Recommendation 3-4-4: Larger-scale, system-level wireless power transmission demonstrations should be planned, either ground or space-to-space demonstrations. Some might involve the International Space Station.
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LAYING THE FOUNDATION FOR SPACE SOLAR POWER The final output could be high-voltage AC or DC depending on the utility network to which the system is being connected. For the laser option technical needs are similar.
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Clearly, it will be essential to consider robotic assembly and maintenance early in the design phase of space solar power system concepts. The cost and logistics related to assembly operations
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) with an LAYING THE FOUNDATION FOR SPACE SOLAR POWER end effecter specialized for a single grapple fixture design.
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It is possible to discuss qualitatively, however, the types of robotic activities and levels of performance that may be necessary to enable SSP assembly and maintenance. While a solar power satellite is orders of magnitude beyond anything ever built in space, it is similar in scale to a number of everyday Earth construction projects, including large bridges, deep-water drilling platforms, skyscrapers, or large ships.
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3TRLs 4-6 consist of technology development and demonstration both in the laboratory and in a relevant environment. LAYING THE FOUNDATION FOR SPACE SOLAR POWER programs to nurture them through to flight demonstration.
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The early concepts for SSP were some of these. In the 1980s, NASA investment in construction of large space structures was largely funded and motivated by the problem of constructing early concepts of the International Space Station.
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In addition, SSP loads include assembly, verification, and maintenance loads, which are loads not ordinarily considered design drivers in modern satellite structures. The primary design objective for the structural subLAYING THE FOUNDATION FOR SPACE SOLAR POWER system is to meet the geometric requirements under the prescribed loads while minimizing cost.
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For example, it has been pointed out that existing space structures, whether communication antennas or the Hubble Space Telescope, are designed for packaged densities on the order of 65 kg/m3 (Lake, 2001~. This is close to the typical payload density of existing large boosters.
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LAYING THE FOUNDATION FOR SPACE SOLAR POWER Challenges to Be Me! NASA provided no basis for establishing what goals are currently achievable with existing structural technology.
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This means SSP can have a vibration frequency perhaps 1/lO,OOOth that of an Earth-pointing satellite. 3-8 THERMAL MATERIALS AND MANAGEMENT Thermal Management Concepts Thermal management is a critical spacecraft capability needed to maintain all spacecraft components and parts within a specified operational temperature range.
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Air Force Small Business Innovation Research program entitled "Freeze-Tolerant, Lightweight, Flexible Radiator," Contract Number F2960198-C-01 15. LAYING THE FOUNDATION FOR SPACE SOLAR POWER of space solar array, PMAD, thermal control, wireless transmission, and launch technologies.
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Similarly, although extrapolations and estimates may be made, no one can accurately determine, today, the costs of space transportation 30 and more years in the future. As a result, decisions on the viability of future space solar power efforts should not be based solely on the space transportation segment of the program.
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Low-cost options for in-space transportation may require large advancements in technology advances that may not occur within the next 510 years without program stimulus. As a result, LAYING THE FOUNDATION FOR SPACE SOLAR POWER investments need to be made in this area, whether under the purview of the SSP program or as a separate NASA initiative.
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Recommendation 3-9-3: The SSP program should develop detailed space transportation requirements for all technology flight demonstrations (MSC 1, MSC 1.5, and MSC 3) that include data from studies on packaging, cost and mass estimates, and other important parameters.
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LAYING THE FOUNDATION FOR SPACE SOLAR POWER In designing a full-scale SSP system, the environmental impact analysis must also include pollution that may occur during emplacement of the facility (production and launch of transport vehicles) , as well as environmental effects during the operational phase.
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The committee understands that the relevance of such cellular phone research to space solar power may be questionable. However, program managers must be aware that the long-term effects of SSP wireless power transmission on humans must be quantified before public acceptance is found.
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In addition, to assuage any fears that this technology could be reworked to be used as a weapon, the program should be international in structure, with full disclosure of information to all participating countries so that no strategic advantage can be gained by any one nation. LAYING THE FOUNDATION FOR SPACE SOLAR POWER Challenges to Be Me!
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Such programs might include development of demonstration models (Pignolet, 2001) , a children's book on SSP, or op-ed pieces on space solar power.
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2000. "Environmental and Safety Factors." Briefing by John Anderson, NASA Marshall Space Flight Center, to the Committee for the Assessment of NASA's Space Solar Power Investment Strategy, National Academy of Sciences, Washington, D.C., September 13.
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Feingold, Harvey.2000. "SERT Systems Integration, Analysis, and Modeling." Briefing by Harvey Feingold, Science Applications International Corporation, to the Committee for the Assessment of NASA's Space Solar Power Investment Strategy, National Academy of Sciences, Washington, D.C., October 23.
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2000. "Space Solar Power: Space Transportation and SSP Deployment Support Studies." Briefing by John Olds, Georgia Institute of Technology, to the Committee for the Assessment of NASA's Space Solar Power Investment Strategy, National Academy of Sciences, Washington, D.C., September 14.
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