9.2 In being designed for this type of mission, it incurs many choices in design details which render it less than desirable for a one-way high flow rate launch situation such as the one necessary for setting up the colony construction site and the lunar base. What is needed in this situation is not necessarily a man-rated booster, and no definite need exists for a high-mass retrieval capability, such as the shuttle orbiter has. Therefore, it would be of economic advantage to develop a heavy-lift, unmanned "deploy only launcher", or DOL, for the bulk of the construction mass. However, economic factors also set a limit in this direction. According to the current NASA space shuttle traffic model (9.1), there is a demand for only 582 space shuttle flights in the years 1979-1990 inclusive. Even assuming a large growth in necessary payload capability as technology expands to facilitate the use of space in industry, the total noncolony lift mass per year would still seem to be far below the yearly lift mass needed in the years of the setup of the colony construction system. It makes little sense, in this case, to develop a highly advanced booster optimized for the high launch rate and mass flows of the three-year setup period, when the booster so developed cannot be supported in later years by a more normal launch rate. Because of this, it is assumed the only available boosters for this project are either the space shuttle, or near-term derivatives using shuttle technology and hardware. The earth surface-to-orbit launch system used in this report consists of a pair of vehicles: the space shuttle, without modifications from its present form, and a deploy only launcher (DOL) as suggested by Kline (9.2). The DOL would encompass the minimum possible modification to the current space shuttle system as shown in Figure 9.1, in order to minimize RDT&E costs. The only change from the shuttle would be the replacement of the orbiter vehicle with an expendable launch protective cover, enclosing the payload. The propulsion is largely unchanged, with three space shuttle main engines (SSME) mounted on the base of the shroud, in the same position and performing the same functions as the three SSME's
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