Performance Goals

NASA has made a determined effort in the SERT program to focus the effort by beginning the definition of a “strawman” or baseline SSP system to provide 10– 100 GW to the ground electrical power grid with a series of 1.2-GW satellites in geosynchronous Earth orbit (GEO). Since no one knows the time scale to build, launch, and assemble on orbit such a system, the committee did not comment on this particular scenario’s potential for commercial appeal (or any of the potential scenarios for MSC 4). Chosen scenarios will be a direct result of the program’s investment strategy, the progress of technology development, and a competitive selection process. The committee did not feel it was appropriate to evaluate each individual scenario for a full-scale system. As a result, various scenarios are not presented in the report. Time to market and size of investment necessary for such a system will be issues that need to be addressed as the program progresses; however, the SERT program previously funded an independent economic analysis to evaluate such issues. Assessment of this analysis was outside the scope of this study.

Top-level cost targets in cents per kilowatt-hour were developed for each of the major SSP systems that NASA managers believed were necessary to finally deliver baseload power at less than a selected target of 5 cents/kW-hr.1 Major system and subsystem functions were each allocated a “contributory” cost goal by program managers. The sum of the contributory goals should, in theory, be equal to the overall cost target of 5 cents/kW-hr. These targets are shown for various design options in Figure 2-2 (Mankins and Howell, 2000b). For brevity, the specific design concepts and options (Mankins and Howell, 2000a; Carrington and Feingold, 2000) listed in Figure 2-2 are not presented in the report. The NASA program plans to continue monitoring this target as markets for electricity change and to adjust this target and its distribution among technologies accordingly. As such, the manner in which current cost goals are set is justified.

A corresponding set of mass, cost, and performance targets was then used to help define where technology funds should be applied, and detailed roadmaps have been developed to accomplish these technology goals. The result of this work is a set of time-phased plans with associated cost estimates, which provide the basis for an investment strategy. The committee notes that there is a lack of traceability (of cost and mass goals) to the next lower level. The committee expects that in future program documents there will be traceability of cost and mass targets down to the subsystem level and to the component level. Without consistent cost and mass goals with clear traceability from the top level to the component technology level, individual technology teams may not make the most appropriate technology investments.

The major SERT system cost and performance targets, as shown in Figure 2-2, are extremely aggressive.2 Additionally, they include reliance that NASA’s separate Space Launch Initiative (SLI) program will be successful in reducing Earth-to-LEO transportation costs to $400/kg. NASA’s second-generation SLI goal is $2,200/kg, and the third-generation goal is approximately $220/kg (NASA, 1999; Davis, 2000). In a SERT Program Status report (Mankins, 2000b), NASA reported that current SERT concepts (December 13, 2000) result in predicted costs for power in the range of 10–20 cents/kW-hr, versus NASA’s full-scale system goal of 5 cents/kW-hr.

NASA has adopted an allowable cost of 5 cents/ kW-hr as its target goal for competitive terrestrial power production. The committee suggests that this value be revisited as the program proceeds; however, it is viewed by the committee as a reasonable starting point for the investment strategy. This choice sets the revenue stream level for a 1.2-GW facility. Once the revenue stream is known, the net present value of this revenue stream can be computed. A simplified calculation was made by the committee for the required return on investment, assuming zero operating costs and a 40-year operating period. The calculation demonstrates the importance of strengthening the cost analysis for the operational system. For instance, using a 10 percent rate of return, $5 billion is available for the entire system.

1  

This 5 cents/kW-hr goal was based on cost estimates gleaned by NASA from an independent economic analysis (Macauley et al., 2000).

2  

Subsystem cost, mass, and performance targets were also supplied to the committee for each technical area in the program’s work breakdown structure. For brevity, only the top-level program goals are presented in this publication. More specific information can be obtained from the listed reference.



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