noted that return capability from station is also a limitation; however, for this analysis, it was not used to limit growth. Shortfalls between Shuttle return capability and user needs were noted and it is assumed that certain on-orbit trash disposal techniques will serve to reduce the return mass requirement. The set of curves in Fig. 2 illustrate the electrical power requirements on space station over the range of assumed lift capability for the various utilization emphases. These growth power levels include both user needs and housekeeping for station systems operation (e.g. life support system). From the analysis, it was determined that the commercial production emphasis which combines both microgravity research and materials production is the driver for station power, requiring 290 kWe. This can be attributed largely to the crystal growth furnaces which are heavy power consumers. In reality, uninterrupted microgravity required for extensive material production will be difficult, if not impossible, to maintain on a manned station. A more realistic scenario is for space station to support microgrvity research and pilot production in order to validate the processes (microgravity research emphasis). Full-scale production would likely occur at a man-tended facility. The shaded range of Fig. 2 established by the four data points in bold type identify power requirements for the microgravity research and life science emphases constrained by the transportation models identified in Fig. 1. These were recently computed based on updated mission requirements and transportation assumptions and compared with the results developed at the SSF program PRR. The requirements for the life science emphasis and microgravity research emphasis increased somewhat but the conclusion a PRR remains unchanged; i.e., 275 kW of power at the mature operations phase of the SSF is adequate to support all feasible utilization emphases in the R&D arena. Figure 3 illustrates the time-phased power growth on station for the moderate transportation model. Power increases from the 75 kW baseline capability to the 275 kW level by assembly complete plus nine years as a function of lift available per year. A sketch of the R&D Space Station Freedom configuration at the mature operations phase is shown in Fig. 4. Eight solar dynamic modules (25 kW per module) have been added to the 75 kW photovoltaic base. Transportation Node Analysis Analysis of space station evolution in support of Mars exploration and manned lunar
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