Fig. 1. Effect of number of SPS produced on cost of transportation to LEO, as a function of payload mass, WPL, per launch. breakthroughs which appear to be imminent. Since in the case of silicon cells the raw material is abundant and cheap, both on earth and the moon, and since the primary cost is in the labor required in their manufacture, it seems reasonable to extrapolate this potential cost reduction. It is also important to consider the effect which the space environment may have on the manufacture of solar cells there, which recent studies (5) have indicated could well be beneficial. A detailed explanation of the rationale used in the solar cell cost estimation process can be found in Appendix A. 3. TRANSPORTATION TO LEO The first step in transportation is the transfer from earth to LEO. It has been recognized for some time that reusability is one of the keys to reducing space transportation costs: this fact has led to the development of the Space Shuttle. However, what may not be as obvious is that these costs, as in any transportation system, are critically dependent on utilization. The factors which have resulted in a four-fold decrease in air transportation costs during the past two decades can be attributed directly to the increased productivity of the jet transport, resulting largely from increased utilization of the capital equipment represented by the airline fleets. A similar cost reduction may be anticipated as space transportation matures into a fully developed transportation system. Such maturing requires a demand capable of utilizing the full capacity of the system. The fifty or sixty flights per year which comprise
RkJQdWJsaXNoZXIy MTU5NjU0Mg==