The initial installation in space is therefore more than capable of producing in 90 days the 63 tons of finished products that would constitute 90% of its mass, the remaining 10% for a replica being brought from the Earth. The oxygen produced by the original plant would be far more than required for supply of propellant to bring the necessary 7 tons of Earth-built components for the replica. With the 90-day replication time, the orbital facility, like the lunar facility, would be capable of growth to a value of 300,000 tons/year of throughput in seven doublings, or about two years. The workshop group has not yet studied the optimization of the mix of products in space between replicas of the primary system and machinery designed for the production of SPS components. Presumably, in the simplest scenario, on reaching the 300,000 ton/year figure the entire output of the facility would be turned to the production of those machines. On the basis of the NASA-funded study^ ' directed by R. Miller and D. Smith of M.I.T., the orbital facility could produce in one to two years most of the machines that would be needed for a steady production thereafter of one 10-GW SPS per year. For the installations that would be replicated, the total amount of unique equipment for which R & D would have to be carried out would be approximately 15 tons. Using cost figures based on Shuttle experience (approximately $60 million per ton) the total investment required for establishment of the initial installations on the Moon and in space, for verification of the overall plan and initiation of the replication process, would therefore include one billion dollars for R & D and $0.4 billion for 16 Shuttle flights, needed to lift 107 tons of equipment and 340 tons of propellant to low Earth orbit. Total program investment to the point of first replication appears therefore to be well under five billion dollars. The interim conclusion of the workshop group is that the concepts of scaling, bootstrapping, and replication appear certain to provide major cost savings in any program, such as that of the SPS, which requires the emplacement of large payloads in high Earth orbit. It is also clear that there is great value in an approach of that kind, which can achieve high return on a modest investment without exceeding the lift capabilities of the unaugmented Shuttle system. The workshop studies will continue, turning to a detailed examination of optimized growth scenarios and the details of equipment design. At present (1980) mass-driver development is adequately funded at a level of $250,000 through the NASA Office of Propulsion and Power. Other than the mass-driver, the only item of equipment in the scaling and replication method that is without industrial precedent is the chemical processing plant. Therefore the Space Studies Institute will initiate a grant, approximately in September 1980, of approximately $100,000 (first year) for research and development on a bench-chemistry level system for the separation of simulated lunar soils into pure elements. The research reported in this article was supported by the Space Studies Institute, Box 82, Princeton, NJ 08540.
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