Masses launched from earth each year are given for both the case in which the solar power satellite is constructed only from lunar resources and the case in which 9% of the mass of a solar power satellite comes from earth [39], It will be assumed here that solar power satellites are constructed solely of lunar material. The time between first shuttle launch and arrival of the first solar power satellite at geosynchronous orbit is 6 years [40], Transportation to low earth orbit is provided for the first two years by the space shuttle only, then by the space shuttle and the advanced space shuttle. The advanced space shuttle is estimated to cost (1975 dollars) $1.3 x 10$ to develop, have payload 113 t. and cost $1.96xl07 per flight, compared to $2x107 per flight given for the space shuttle [41], Since the cost of the space shuttle per flight will actually be $9 x 10' by 1985, it will be assumed that the cost per launch of the advanced shuttle is increased by the same proportion, to $8.82 x 107. The 60% increase of actual over expected development costs for the shuttle will be assumed to also apply to the advanced shuttle development, yielding 1.6 • $1.3 x 10$ = $2.08 x 10$. All equipment for manufacturing and transportation is complete at the end of 1991 in this plan [42], The number of shuttle flights through this time is 272, and the number of advanced shuttle launches is 344 [43], Since a fleet of 5 shuttles, with 30 flights per 6 months, is used exclusively for this plan, each shuttle would make However, the present planned fleet of 4 shuttles must provide 18 flights per year for other purposes, so a total of 7 shuttles would be required, or 3 more for this plan. Four advanced shuttles are required also, [44] and it will be assumed their cost is the same as that of the standard shuttles, $10$ each. The total transportation cost from earth to low earth orbit is therefore The first space shuttle trip is assumed to take place in January 1985 in this plan. To determine the cost of construction of the space manufacturing facility, assume that the average number of men in space from then to the end of 1991 is 1000. In SP-428, it was assumed that they consume 3 kg/(man • day) until the beginning of 1990, when oxygen from the space manufacturing facility begins supplying 1.5 kg of the 3 kg [45], It will be assumed therefore that the average mass of consumables from earth is 2 kg/(man • day), so the required mass is
RkJQdWJsaXNoZXIy MTU5NjU0Mg==