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Appendix F A SUSTAINED MANNED SPACEFLIGHT PROGRAM Perhaps the single most important assumption made in this report is that the nation is committed to a sustained manned spaceflight program. If true, that commitment has direct consequences to shuttle operations. In particular, unless the shuttle fleet is maintained during the l990s at approximately the realistic flight rates given in this report, the necessary foundations will not exist for manned Space Stations, SDI in-flight development, testing of tactical intelligence and battle management concepts, clinical research, countermeasure testing related to space adaptation, and development materials- processing systems that depend on the space environment. The realistic or sustainable flight rates in this report are based on supply constraints and mission demands for presently committed missions, not those still in conceptual design. For example, Space Station needs cannot be supported without what the Space Station Director properly calls a "robust shuttle fleet." The. assumption of a national commitment to a sustained manned spaceflight program would be self-evident were not an alternative under discussion in the government. This alternative would not replace the present Orbiter fleet (either 3 or 4 Orbiters) when and as needed but would let the shuttle fleet decrease through attrition, relying on a future vehicle fleet of more advanced vehicles to pick up the manned flight effort and on ELVs to launch all payloads not requiring astronaut intervention. The advanced manned vehicle usually mentioned is the National Aerospace Plane (NASP), though a modified shuttle (high safety, minimal cargo) is also being discussed. One difficulty with the alternative assumption (shuttle attrition) is timing. As the shuttle is demonstrating, it takes at least a decade to develop a space vehicle to the point of reliable operation even when the technology is believed to be in hand. Technology for the National Aerospace Plane is not yet in hand and the size of the vehicle contemplated for the turn of the century is too small to handle shuttle-equivalent payloads. Modifications to the shuttle are under study, but they are not yet past the conceptual design phase. The alternate assumption, therefore, would predictably result in a hiatus (5 to 10 years) in manned flight, precluding the Space Station planned for the l990s. 47
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48 A more serious difficulty, however, would be the imminent collapse of the shuttle manifest. As discussed in Appendix C, at 10 flights per year and a 1-2 percent loss rate, but with no replacements, the shuttle fleet would be down one Orbiter in about 5 years and down 2 in 10 with corresponding flight rates of 7 and 4, respectively, per year. Those rates would hardly handle the man-critical missions. In anticipation of an uncertain launch future and to protect their missions, mission directors would no longer design shuttle unique payloads and for planning purposes would schedule on ELVs. ELV production facilities would expand accordingly. Thus, even before any losses might occur, the uncertainty in the future of the shuttle fleet could result in a collapse of the l99Os manifest and an increased cost per flight, which would deal manned space flight a serious blow.
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