Table 3.1 Recent Intelsat Communications Satellites FMarirv 1QQ91 The same operational time-period of eclipse servicing might be of interest for satellites other than those at the end of their lives. By designing satellites to take advantage of beamed power rather than relying on batteries during an eclipse, significant mass savings might be achieved. Figure 3.2 shows the relationships between power needed during eclipse and battery masses for current levels of technology. Keeping in mind that nickel-hydrogen batteries are likely to replace nickel cadmium within the near future and that in the next three decades power levels are likely to increase substantially, one might optimistically guess that a mass savings of about 150 kg per satellite could be achieved. If one makes the rather conservative assumption that transponder mass remains the same over the mid term to balance the above optimistic assumption, and assumes the current transponder earning potential of $5 million/year remains constant, one can calculate the potential market value. Taking 150 kg at 20 kg/transponder, the additional earning potential comes to $37.5 million/satellite. Multiplying as before by 20 satellites, the market comes out to be about $750 million/satellite, or $1 billion for the constellation case where each power satellite services on average 27 clients. The same 150 kg of mass savings could be used to add propellant to the satellite and extend its possible lifetime in orbit. The problem with this, however, is that unlike the lifetime extension market described above, these satellites would require servicing throughout their lifetimes, instead of just at the end. A communications company would by no means be assured that the satellite would live long enough in orbit to benefit from this extra propellant, so any revenues would either be small relative to the former lifetime extension case or would come 20 years after the servicing began, if at all. Also, the total worth of the extension would have to be divided by the whole satellite lifetime instead of just the added years. As with the life-extension market described above, several factors must be considered when examining the numbers above. The first thing to be noted is that servicing this market segment takes up only a small portion of the satellite's total yearly capacity. Power not needed for eclipse operations of GEO satellites could conceivably be used for reducing or eliminating dependence on batteries for satellites in lower orbits. Mass savings in batteries are more difficult to assess in terms of monetary value for such satellites, however, so any numbers generated here would probably be next to meaningless. Qualitatively, however, one can note that lower orbiting satellites are much more dependent on batteries so that potential weight savings are greater, but also that lower satellites are harder to track and have longer eclipse duty cycles so that the number of clients which could be serviced by a single power satellite would be significantly reduced.
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