Nebraska, SPS Program Review Conference. As a preamble, it must be remembered that the immediate SPS program decision is not whether or not to invest in the capability for placement of the SPS network (the investment phase) but rather whether or not to place “at risk” a much smaller sum to continue the research phase of the SPS to conduct the “ground-based exploratory development” (GBED) activities. The significance of the operational space transportation system cost estimates is, instead, whether the necessary investment in space transportation is so large as to preclude a positive decision in some future year to deploy an operational SPS network, given development success in all other areas. The breakout of estimated resource requirements for space transportation during the investment phase was given by NASA as follows: Cargo to LEO (HLLV) Development — $10.6 Billion Cargo to LEO Fleet Acquisition — $6.1 Billion Launch and Recovery Facilities — $7.3 Billion Cargo OTV Fleet — $6.0 Billion Total — $30.0 Billion It is evident from these numbers that the HLLV is the most important element in the transportation system for detailed consideration, requiring more than 80% of the total investment phase transportation funding. This vehicle, a part of the “SPS Reference System,” is large, with a payload in excess of 400 metric tons. It was appropriate that much of the transportation session at Lincoln was devoted to alternative concepts for the HLLV, with significant emphasis upon the issue of the appropriate scale and, therefore, payload capability of and investment required for this vehicle. NASA-MSFC introduced the transportation session: describing the reference transportation system, the task this system has to accomplish, and observing that approximately $1.0 million had been dedicated to the area of space transportation in the four-year DOE/NASA SPS assessment program. As a consequence of this low level of activity, the transportation system is characterized as having only a shallow definition. The HLLV has been studied in numerous configurations. The concept selected for reference is a two-stage, winged recovery vehicle. It is not yet clear where the vehicle payload capability should lie within the range of 100 to 500 metric tons capability and whether the two stages of the vehicle should provide impulse in series or in parallel. The near term technological activities are those related to: (1) performance; (2) productivity; and (3) environmental impact. The NASA presentation properly set the stage for the subsequent papers and accurately characterized the HLLV as the prime candidate for innovative approaches. The motivations for new approaches are to delay large investments until the SPS program is generating revenue and to consider more than a single generation system (and technology level) for this long-term (30 years) operational phase with the goal of reducing HLLV operational costs. A representative of the Federal Republic of Germany (FRG) presented the second paper of the session on the European Space Agency (ESA) view of the space transportation system appropriate to an SPS program and other large scale space transportation tasks such as the disposal in space of nuclear waste material. He used in his analysis for ESA a universal “figure of merit,” which is related to costs, of man-years per megagram (MY/Mg) placed in low Earth orbit. He characterized the United States Space Shuttle “figure of merit” as 12 to 15 MY/Mg at the 29 ton payload size. He stated that the SPS target was a figure of merit of 1 MY/Mg, equivalent to about
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