In all the plans which use self-reproducing manufacturing facilities, the only vehicle required for transportation from earth to low earth orbit is the current version of the space shuttle. The plan taken from the NASA study of 1977 on Space Resources and Space Settlements, which is used for comparison, requires a modified space shuttle, however, with greater payload, since more material is brought to space from earth. It is possible to use only the space shuttle in the plans using self-reproduction because this makes the total mass from earth sufficiently small. In the extended versions of the SSI plan, the mass of a self-reproducing manufacturing facility for use on the moon is 25 tons. This can be taken to earth orbit in one flight of the space shuttle. This manufacturing facility is used both to create copies of itself and to eject matter to a space manufacturing facility, using a mass driver. The self-reproducing space manufacturing facilities have a mass of 58 tons each. The material ejected from the moon is caught at L2 and used by the initial space manufacturing facility to make copies of itself. It is assumed in the SSI paper that both the lunar and space manufacturing facilities are able to produce a copy of themselves every three months. This assumption is based on rates of assembly and chemical processing throughput in the most advanced facilities which now exist on earth. This self-reproduction continues on the moon until 128 copies exist there, which requires seven generations of self-reproduction. In space, the self-reproduction continues until 259 copies of the space manufacturing facility exist, which requires slightly more than eight generations. At this point, the space manufacturing facility is able to construct one solar power satellite per year, with a mass of 105 tons. After construction of the first solar power satellite, in these plans the lunar and space manufacturing facilities are further expanded to the point at which the rate of construction of solar power satellites is sixteen per year, which rate is maintained indefinitely. In the plan which most closely follows the SSI plan, the first set of sixteen solar power satellites is delivered to the final position in geosynchronous orbit eight years and four months after the first launch of a space shuttle carrying equipment for the project. In a plan which uses pure self-reproduction and some construction of equipment in low earth orbit by a manufacturing facility, the time is nine years and nine months. The time from first launch of equipment to the arrival of the first solar power satellite in geosynchronous orbit for the first plan of the preceding paragraph is six years and one month. In the second of the plans, this time is seven years and six months. In comparison, the time until completion of the manufacturing facility in the plan of the 1977 NASA study on Space Resources and Space Settlement is six years, at which point three solar power satellites are complete. The costs of each of these plans up to this point are $42.56 billion, $11.24 billion, and $136.54 billion, respectively (1983 dollars). Times and costs are also derived for the construction from asteroids of solar power satellites and habitats. A plan worked out for construction of both uses two asteroids, one of mass 10$ tons, the other of mass 10^ tons. A self-reproducing manufacturing facility is sent first to the smaller, then makes one copy of itself for continued use there before moving to the larger. On both, self-reproduction proceeds until enough construction capability is built up to allow, in the minimum length of time, the construction of sufficient numbers of large mass driver reaction engines to return the
RkJQdWJsaXNoZXIy MTU5NjU0Mg==