4. Space Segment Model Description Analysis of the technical and financial performance, cost, and potential benefits of the various SSP concepts/architectures required the development of analytical tools that could provide a systematic and rapid evaluation of key elements and options. One of these tools, the Integrated Architecture Assessment Model (IAAM), simulates the performance and energy markets associated with the deployment and operation of SSP architectures and generates costs and revenues to assess and compare their economic feasibility. The model, described in detail in Section 5, consists of several segments that analytically capture the major elements of an SSP architecture. The most important of these elements is the space segment, which covers the constellation of solar power satellites, their masses, costs, deployment, and operations. Because of the complexity associated with the numerous options and trades available to the space segment, we developed a separate analytical model for this portion of the SSP architecture. Called the Space Segment Model (SSM), it incorporates the most significant aspects of the space segment’s design, including number of satellites, power delivery capability, subsystem and component technologies, ground site locations, and orbital configuration, and produces an evaluation of relevant system size, mass and cost. The SSM can be run independently to evaluate technical and cost issues related to specific design choices, and it can also interface easily with the IAAM model to investigate the economic and financial implications of such choices. 4.1. Model Organization The SSM has been developed as a Microsoft Excel 6.0 workbook of 19 worksheets representing basic space segment elements, such as flight systems, subsystems and orbital geometry; and utility worksheets that take care of the required input/output functions, and provide convenient databases of ground site locations and default system parameter values. The model also contains a worksheet that estimates the impact of high volume manufacturing on flight system production costs and the associated ground facility investment requirements. Figure 4-1 lists the major worksheet groups and describes their functionality. Figure 4-2 depicts the top-level organizational structure of the SSM, illustrating the key interconnections of the various worksheets, including the external interface with the IAAM model (partially represented by the shaded blocks). The IAAM Interface worksheet functions as an intermediary between the two models, taking the results produced by the SSM and organizing them into the designated cells and formats used by the IAAM input worksheet so that they can be inserted into IAAM either directly or by cut-and-paste. Much of the information provided to the IAAM Interface comes from links to the Space Segment Summary worksheet which has been designed as the primary source of resuhs and hard-copy output information for users of the SSM. An example of the types of information contained in the Space Segment Summary is shown in Figure 4-3. The summary sheet is a combination of system architecture and configuration information representing the user input, confuted performance results indicating the power and daily kWe-hrs delivered to user-selected ground sites, and computed estimates of required flight system (wet) mass and cost.
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