5. ECONOMIC ANALYSIS OF POWERSATS FOR SPACE STATIONS 5.1 Analysis Approach As noted earlier the cost to develop a Powersat is all but impossible to calculate with any real confidence. Given the immature status of Powersat studies, such estimates might be inaccurate by perhaps as much as one order of magnitude, thus making economic assessment of Powersats meaningless. The approach adopted by this study is to determine the cost envelope under which Powersats would have to be developed in order to be economically attractive. This is achieved by taking the above discussions and calculating the cost savings of not having to launch the extra propellant and batteries otherwise required to expand the station’s power with additional solar arrays. In other words, this analysis indicates the maximum total annual revenues a Powersat operator could expect to achieve from supplying power to a space station the size of Freedom. 5.2 Launch Costs In Section 3 it was shown that small, one-off mass savings do not necessarily translate into financial savings. The same is not true for space stations because the mass savings are on the order of several tonnes launched every year. Importantly, the cost to deliver large quantities of mass to a space station is more expensive than to just launch that mass into Earth orbit. For Freedom, the Shuttle is used because it provides all the propulsion and guidance systems necessary to rendezvous and dock with the station. Europe has proposed the development of a “smart” upper stage designated the Ariane Transfer Vehicle (ATV) that would provide many of the same rendezvous functions as the Shuttle Orbiters. (Figure 5.2-1) [15] Hermes is incapable of delivering any propellant.
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