substitute, especially since it ranks second in abundance behind silicon. Of course, the need for oxygen can be eliminated by employing electric or very advanced nuclear propulsion (e.g. gaseous core reactors). But each of these alternatives has its own set of disadvantages and problems that keep the lunar oxygen a competitive option. As shown in the chart MAIN SPACE INDUSTRIAL TRANSPORTATION DECISION/EVOLUTION TREE, what constitutes an optimum transportation system depends on many decisions regarding space industrial objectives and systems functions as well as growth prospects. The early lunar opportunities themselves depend on this decision process, as is reflected in the chart LUNAR INDUSTRIAL DEVELOPMENT DECISION TREE.

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Lunar settlements offer an ideal and , compared to space colonies, inexpensive (especially in terms of initial investments) proving ground for exploring, testing and perfecting all aspects involving the post-exoindustrial phases and the development of neocosms from technological and biological factors to the intricacies of socio-psychological and behavioral aspects. Creating new industrial and living environments is an intensive learning process. Trial and error will continue to be an unavoidable part of the evolutionary process. It can only be kept to a non-negligible minimum. Failures will occur. The lunar environment, especially the lunar underground, offer comparatively more forgiving features than does orbital space. Through the exoindustrial, exourbanization and extraterrestrialization phases, the Moon will play an increasingly important role.

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The evolution of lunar industrial development can follow different paths, depending upon decisions during earlier phases of space industrialization, especially decisions related to a space energy industry and to transportation systems 1.e. chemical (oxygen/hydrogen consuming) or nonchemical (electric or nuclear-hydrogen consuming) propulsion systems. Beginning at left, assuming the nod on using lunar resources and if microwave transmission is selected, and if fusion is used as primary energy source, a relatively comprehensive lunar industrial development could be stimulated, since the great majority of materials needed for fusion-powered microwave plants (metals, silicon) is available on the

If solar energy is used in conjunction with microwave transmission, a lesser stimulation of lunar industrial development through space energy systems is expected. Solar systems are not heated independently as are fusion systems Therefore, their materials are subject to considerable temperature variations. This and other considerations suggest that different materials not available on the Moon should be used extensively (carbon fiber, graphite epoxy, protected by metallic coating from solar UV and particles). Thus, the choice of interorbital transportation becomes a factor. If chemical drives are used, the supply load from Earth could be reduced significantly (at an insignificant reduction in terrestrial jobs) by using lunar oxygen. Since sodium would be a highly effective metallic coating material for structural components of the power satellites, a more limited lunar industry providing liquid lunar oxygen (LLOX) and sodium could be stimulated.