Issues associated with the levels of human productivity needed to realize these benefits are discussed under cast study 3, below. This scenario, case study 1, does not justify development of extraterrestrial resources except in reducing cost of building and supporting a lunar base. If economic uses of lunar resources are sought as a rationale for a lunar base, supporting the base itself is clearly not that rationale. Case Study 2. Export of Lunar Materials for Use Elsewhere in Space. In this case study, I consider establishment of a lunar base for delivery of lunar materials to another location in space for use, compared to delivery from Earth. This is the ‘company town' scenario: is it a worthwhile investment to put a ‘company town' on the Moon, given the reduction in transportation delivery costs as compared to shipment of all resources from Earth? For this scenario, one may construct relatively simple ‘break-even' equations that shed considerable light on the economic issues. Before we get into the break-even equations, some discussion of mission capabilities is appropriate. We will take as an example the supply of liquid oxygen to low Earth orbit from the Moon. This case is one of the simplest to analyse since production of a bulk commodity liquid oxygen can almost certainly be done with relatively little labour; differential labour costs between Earth and space are probably not a main factor. Typical mission modes were briefly discussed in Woodcock (1985). In this reference, it was shown that reasonable payoff factors are obtained only with use of a mass driver for launching lunar oxygen off the lunar surface. There are three options for mass driver targets: low lunar orbit, a libration point (L2 is the preferred one), and direct launch to low Earth orbit. Table II presents a comparison; Fig. 1 illustrates a typical trajectory from the lunar surface to low Earth orbit. Note that the mass driver locations from launch to L2 and direct to low Earth orbit are markedly different (any equatorial location is satisfactory for launch to low lunar orbit). The direct-to-LEO case still requires hydrogen from Earth because it is presumed that the oxygen carriers launched from the Moon must be returned to the Moon by conventional rocket propulsion systems. For this paper, I selected direct launch to LEO because it has the simplest
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