would enlarge the beachhead and begin manufacture of power satellites by "living off the land'1, that is by processing lunar materials, rather than by depending wholly on a long, expensive supply line from the earth. By that approach, the three most serious economic barriers to satellite power could all be avoided: 1) Satellite powerplants to satisfy U. S. energy growth demands during a five-year period about 20-25 years from now would weigh more than six million tons. The establishment of orbital facilities to process and construct those plants from lunar materials would require launch from the earth of only about 1 or 2% as much mass. Therefore, the power satellite/ orbital manufacturing program could be carried out with shuttle- derived launch vehicles, and more advanced vehicles could be developed later if they became justified economically by increasing traffic and profits. 2) Once released from the constraints forced by ground-launch lift-costs, there would be no need to choose solar-cell arrays in preference to turbogenerators. The achievement of great improvements in solar-cell mass and cost, if those improvements turn out to be achievable, might permit further reductions in power costs, but the attainment of the improvements would no longer be a condition for the economic viability of satellite power. 3) The transport of lunar materials to the orbital facility should be relatively inexpensive ($1 to $2/lb including
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