1. 2 I.2: PROJECTED USES OF SPACE COLONIES I.2.1: General Remarks: Space colonies need economic as well as philosophical justification. The establishment of a space colony program is financially one-sided. The mother planet, Earth, provides research and development, construction facilities and materials, manpower, training, and transportation; the initial investment is considerable. Once the major systems (transportation, materials procurement) are operational, and the first colony is complete (becoming the trained manpower supply and the construction facility), the program costs are greatly reduced. However, material imports and services from Earth to the colony still add to the bill. To offset the mother planet's expenditures, space colonies are expected to provide economic returns in the form of specialized goods and services, taking advantage of the colonies' unusual location and environment. This section describes the principal anticipated products of space colonies. The list will grow and change as our abilities in space and our requirements for space products become better defined. Though it is not the purpose of this study to evaluate the benefits of space colonies, the design of any space colony must be based in part on the requirement for such economic returns. I.2.2: Manufacture: A number of manufacturing processes benefit from a zero-g environment. In a gravity field, density and temperature effects cause sedimentation and convection currents in fluids, thus affecting crystal growth, refining of substances, and separation of components in fluid mixtures. The Skylab missions performed fourteen experiments to determine how the absence of sedimentation and convection affected processes such as float-zone refining, growth or ultrapure crystals from liquid melts and vapors, production of infrared optical materials, and doping of electronic semiconductors by liquid diffusion. The results of these tests (1.2) demonstrate a significant improvement in the desired properties of the spaceprocessed products over their Earth-produced counterparts. Space processing extends the metallurgist's or crystallographer's control over his materials down to the microscopic-even molecular-level.
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