generate multi-billion dollar profit over a 20 year period, but this depends crucially on the price and amount of power sold. Pessimistic assessments of both of these parameters drives the program into net loss, but a large lunar market would seem likely to ensure the viability of the laser power beaming project The decision on whether to implement a microwave or laser system in the medium term must depend on a more thorough economic and technical analysis in the future, when developments in laser and microwave technology can be re-assessed, along with the potential market size and value. This latter consideration depends largely on the degree to which large scale space development and exploration will occur in the time-scales considered. Space to Space Power Beaming Space to space power beaming offers an alternative approach to servicing the same markets examined for ground to space beaming above. As discussed in Section 3.1.1, however, space to space power beaming is essentially a mid term market (because space based laser systems are not yet technically feasible), that is a market that involves delivery of power to satellites that are designed specifically for such power reception. The Mid to Long Term Market In general, the transmission medium may be either laser or microwave, and while the former has advantages in terms of antenna and receiver size, microwave techniques offer greater efficiency and generally cheaper technology (see section 7.2 for an explanation of transmission fundamentals). It terms of cost, die size of the required antenna for microwave transmission will offset the savings of cheaper technology and greater efficiency. Accurate costing of power satellites is not practical at this stage without some details of satellite design, so for the purposes of a NPV model and sensitivity analysis for a commercial space to space power project, we will assume the cost of microwave and laser stations to be the same. In determining the cost of a 1MW class space power station, we note that Brauch [Brauch et al 91] estimates the mass of a 1MW diode array laser system in the 100 ton class (187 tons). In section 10.4 of this report, the 1MW class microwave beaming station is also in the 100 ton class (130 tons), with estimated costs of order $1B ($1.3B). This cost corresponds to a widely accepted rule of thumb for space hardware costs of $100M per ton. A baseline cost of development and launch of a 1MW power satellite of $10B is assumed for this analysis. Recurring costs for subsequent stations is taken to be 60% of this value, so that we can designate development costs at $4B and construction costs at $6B per satellite. The development and construction costs are assumed to be evenly spread over a 5 year period, with revenue operations beginning in year 5. Operational costs can be taken at $50M per year per satellite, since fairly complex monitoring, tracking and control will be required for such a system. However, we will take an optimistic baseline assumption that regular space based maintenance of the satellites would not be required, and that the power station design life is 10 years. Inflation and discount rate are 5 and 20% as before. Three power stations in 7500km equatorial Earth orbit can supply power to both low and high equatorial orbits, with only minimal and short term gaps in coverage [Eurospace, 92]. To cover polar orbiting spacecraft, we assume a further 3 power satellites are required. Though power hungry OTV clients might not be serviced by such a system (each OTV would require a dedicated power satellite at 1MW), the high inclination LEO customer base which cannot be supplied by the ground based power system should more than compensate for this. We therefore assume the market related parameters (price and amount sold) used in the mid term analysis above. These give the results shown in Table 11.4.
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