Fig. 2. Systems definition process At midpoint in the assessment, the objectives and the observations on outcome are still valid. Approach The DOE/NASA assessment is an evolutionary process, drawing on past studies, developing new knowledge within an expanding framework of issues, and laying tentative plans for critical studies and for experiments. Public interest groups are actively involved. The evolution of the assessment is illustrated in Fig. 1. The period from late 1977 to 1980 embraces the DOE/NASA CDEP effort in which definition of the Reference System is being further developed, key issues are explored, critical assessments are completed, and contingency plans are formulated. The CDEP will culminate in 1980 with a report including statements of what is known, and equally important, what is not known about the SPS concept and with recommendations and options for consideration by government policy makers. A next phase, a Ground Based Exploratory Development (GBED) Program, is being planned should CDEP identify no “program stoppers” but instead leads to a decision to proceed. The GBED program would include critical experiments, analyses, and technical verification activities that would support, at the end of the program, a soundly-based decision either to (1) stop the program or (2) proceed to technical verification of the concept including orbital experiments. The CDEP facilitates a continuing exchange of information between the systems definition activities and the environmental, societal, and comparative assessment efforts, and an interaction with the interested public. In this interplay, potential problems can be quickly exposed and possible solutions can be developed. The Systems Definition process (Fig. 2) iteratively refines the Reference System in the context of new concepts and technologies. The process provides for the
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