Unfortunately, Shuttle launch costs are effectively independent of flight rate. Therefore, using a Powersat to support Freedom would not directly realise such savings, but it would effectively ‘free-up*’ much needed Shuttle capacity - about 50-75% of one Shuttle flight. The Powersat approach would probably not save as much money in Shuttle launch costs as indicated above - although it would still save the overhead and other costs - but it would provide the opportunity cost savings equivalent to this by effectively increasing the Shuttle launch rate by 10%. Reducing the annual logistics burden on the Shuttle is perhaps the single most important reason for a Powersat, as it enables the Station’s power to be upgraded relatively easily. As mentioned earlier, the Shuttle's launch rate is limited to about 6-8 flights per year. This means that if the actual logistics and maintenance burdens for Freedom turn out to be even a little greater than that currently planned (i.e. one extra Shuttle flight), the US may be unable to expand Freedom to any higher power level even if they wanted to. This is simply because the Shuttle cannot fly frequently enough to carry the additional solar arrays and increased annual propellant and battery load. A Powersat approach, should it be technically feasible, might be one of a few alternatives which could allow Freedom’s power level to be significantly expanded. This is especially the case if the Powersats can be assembled as fully integrated (i.e. non-serviceable) spacecraft launched on expendable launchers (e.g. Ariane 5). In addition to saving some money, Powersats might make power expansion of Freedom practical.
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