Figure 14-5. Effects of launch to LEO cost on SPS economics. The HLLV target cost range shown on Figure 14-5 is $30 per kg to $ 150 per kg; however, current HLLV studies indicate that future transportation costs would more likely range between $60 per kg and $200 per kg depending on the class (size) of vehicle and the annual flight rate. Launch costs for a vehicle of the approximately 225 000 kg payload class with a launch rate of 600 per year are actually estimated at $60 per kg. Assuming SPS would require an HLLV with at least that payload capability and an annual flight rate of 600 to 800, the transportation operations cost was estimated at $66 per kg to include a 10 percent or more growth contingency. While this estimate represents a significant reduction from current launch costs, the HLLV concept of large payload capability, maximum reusability, and short turnaround time is expected to establish the required low cost transportation for the SPS program. The sensitivity of generation cost to other SPS cost elements was also determined and found to be less sensitive than those mentioned previously. Figure 14-6 shows the effect of structure cost on generation cost. Although the SPS economic feasibility is not dependent on a significant cost reduction in structural members, it could depend on the ability to develop fast and reliable structural assembly techniques.
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