option as the basis for the mass and cost estimates. In this option, the system is sized to provide the specified power as the maximum to be delivered to one or more of the listed ground sites. In other words, some site locations would receive less than the maximum power. This avoids system requirements being driven by the most inaccessible site locations and provides consistency across the different case studies. However, as a result of this groundrule, care should be taken in interpreting the case study values of “Delivered Power per SPS” and “Total Delivered Power” in Tables 6-1 and 6-2. These should be considered as maximum possible values and would probably not be attained at every ground site or over the entire set of ground sites. In fact, the value shown for “Total Delivered Power” also presumes a fidl 24 hour duty cycle for each SPS as well as a sufficient number of appropriately placed ground sites to deliver that power. Many of the modeling assumptions concerning the mass, cost and performance of space segment components and technologies were obtained from the invited participants at the Phase II Technical Interchange Meeting (TIM) held at NASA Lewis Research Center on June 12-13, 1996. Other data were provided by Richard Dickinson, a member of the SSP Study Team, and study consultants whose white papers can be found in the appendix to this report. The sensitivity of the case study results to these and other assumptions and groundrules described above, has been tested and the results reported below in Sections 6.2 and 6.3. Before proceeding to the discussion of the IAAM results and sensitivity analyses, one last space segment topic should be addressed. That topic relates to the issue of non-recurring costs and the assumptions made in arriving at the values used in the model The driving assumption is that the non-recurring costs for all of the SSP concepts would be based on flight testing a 10 MW demo version of the particular concept in LEO. Non-recurring cost estimates for the different subsystems/components were then obtained from various sources: • Non-recurring cost for the Power Transmission subsystem is based on estimates provided by R. M. Dickinson and W. C. Brown. • Non-recurring costs for all other subsystems, including Solar Collection, GN&C, Structure, Telecom and C&DH, are based on estimates obtained through Cost Estimating Relationships (CER’s) from the NASA/GSFC Spacecraft Cost Estimation Model, augmented by new technology development estimates obtained from the Phase II TIM. • Non-recurring costs for System Assembly, Integration, Test and Evaluation, leading up to the flight demo, were also obtained by using relationships from the GSFC cost model The Space Segment Model was then run to determine the estimated cost of a 10 MW LEO-based demo for each SSP concept. Those costs, estimated at the subsystem level, were then used as the non-recurring cost basis for all subsequent analyses. 6.1.3. IAAM Case Study Results There were seventeen cases identified for analysis using IAAM, each representing a unique SSP architecture. Within several of the cases, architectures were analyzed by focusing on specific target markets. A summary of all cases is shown in Table 6-3.
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