dozen satellites simultaneously. At the present, however, this market route seems unlikely to lead to commercial viability. One other is to illuminate solar arrays which have degraded due to the adverse effects of radiation. It is thought that perhaps this treatment could extend the life of a satellite or allow weight savings in solar panels. Solar panels are now sized to take degradation into account and are hence larger than necessary at the beginning of life so as to generate adequate power levels at the end of life. If this extra panel area was not needed, perhaps the weight savings would be enough to provide a market for beamed power. Table 3.2 presents the statistics for a hypothetical satellite in GEO making use of this service. The satellite is assumed to consume 10 kW of power, a number much higher than the consumption of current communications satellites, but may be reasonable for satellites launched 20 to 30 years from now. Mass savings are calculated as the mass necessary to generate the 10 kW at the beginning of life subtracted from the mass of solar panels necessary to generate the same power at the end of the number of years shown in the left column. The mass and degradation models used were for solar arrays of the type used on the European satellite Olympus. [Pidgeon, 1991] The duty cycle, or percentage of time which the laser must be focused on the client's solar panels, was calculated assuming laser intensity of 5 Suns producing 8 times the array's normal power level. It was also assumed that the client satellite had batteries for power storage, so that the necessary energy could be imparted in a short burst instead of a continuous beam. The maximum mass savings possible with current technologies seems to be about 35 kg for a satellite with life expectancy of 20 years. Using the figures presented above of $5 million/year of revenue for each transponder and 20 kg/transponder, it seems that the weight savings for each satellite would amount to a value of $8.75 million. Since a single client requires on average about 2.5% of a power satellite's time, at most 40 clients may be served by a single power satellite giving a total saturated market worth of $350 million/year. Unfortunately, as with the other potential markets described above, there are problems which reduce the attractiveness of the market. First of all, the case described above assumed no significant advances in solar cell technology. No solar cell weight reductions or increases in efficiency were considered, nor was the possible introduction of radiation-resistant indium phosphide cells. It is conceivable that for structural and vibrational reasons large flimsy arrays of lightweight solar cells will not come into widespread use over the next two decades, but some advance in the state of the art should be expected. However, given present trends in the photovoltaic industry it seems likely that indium phosphide solar cell costs will drop substantially and that they will come into widespread use on geostationary satellites. Such a development would preclude exploitation of this market niche.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==