where N is the total number of years required for production. There is also a cost associated with refurbishment: an older satellite needs some repair to stay on-line over an indefinite period of time. Defining m to be the fraction of the satellite replaced each year (equivalent to 1/operational life without refurbishment), this cost is However, the system is capable of continuing indefinitely after production ceases; the additional cost associated with operation until year/, is mCR(L-R) where CR is C, at j=R. The total refurbishment cost is then Most parameters assumed are listed in the body of the text. The following individual system R&D costs were assumed: SPS $10B Earth Launch System $ 5B Space Manufacturing $ 5B Lunar Mass Driver $10B MD Reaction Engine $10B Lunar MD x MDRE $15B Thus, a system which included a lunar mass driver, mass driver reaction engine, and space manufacturing of an SPS with an earth launch system for support would have an R&D cost of $35B.
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