Fig. 9. Effect of lunar surface refining site with baseline propulsion cases. costs. This is evident from Figure 9, which shows that, when the refining process is accomplished at a lunar surface base, the use of lunar material is competitive with propulsion option (T2). Many assumptions are implicit in the results presented above and it is essential in any systems analysis of this type to test the sensitivity of the conclusions presented to these assumptions. As mentioned earlier, the most important parameters of the problem are the productivity in space and the costs of transportation. Figure 10 shows the effect of varying the transportation costs from the values given in Fig. 1. It should be noted that these costs are based on future value in Fig. 6 and all subsequent total system cost presentations (see Appendix C). Fig. 10. Effect of earth launch costs on power cost. Figure 11 shows the cost of varying productivity, one of the most difficult parameters to evaluate. To place this number in context, terrestrial operations show the following productivities: Aircraft assembly 1 kg/hr Light industry 6 kg/hr Construction work 50 kg/hr
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