subsystems which are more technologically developed now. Since up to now no detail subsystem designs are available, the only thing we can do is to break down the cost of solar power satellite according to the relative technique readiness level by subsystems as shown in Table 10.3.12. Table 10.3.12 Spacecraft Cost Breakdown S.U — full scale space qualified hardware not available, development work needed. S.Q — full scale space qualified hardware could be built with the existing technology. The phased array is the most complex part of the satellite, because of the large size (10 m by 10 m) and the simultaneous phase control requirement of every element for pointing the beam to the given target. For the power conversion of 100 kW level, problems such as power balance, thermal control and high efficiency conversion hardware in space need to be solved. Finally for the AOCS.the satellite's large flexible solar array will cause attitude stabilization problem which may need new control techniques to be developed. And the magnetic torquers for attitude control may also cause EMC problems which can only be solved by system test. Based on the above facts, we come to the cost breakdown which needs to be improved with the progress of this demonstration project. In conclusion, much more research and development work need to be done with regard to the technology we need to put solar power satellite into orbit. We need to convert the lab scaled technology to the space qualified full scale technology with low cost. It is found that the budget of $800M is a strong constraint to this demo project. And a new concept for the $800 M demonstration may be needed. Alternative Design (Solar Dynamic Power generation) In Chapter 7, it was shown that over a long period, a solar dynamics system was potentially less expensive (almost 1/2 the cost) than an equivalent photovoltaic system. Therefore, in this section an alternative design based on a solar dynamic system will be discussed. At the moment no solar dynamic systems have flown in space. Therefore it was not thought feasible to baseline the SDS as the power source of the satellite, since this is aimed for a near term launch (in ten years time). However if technology became sufficiently developed and systems were space qualified then it may be possible to integrate this system on the satellite in time for the launch on this mission, thereby taking advantage of the benefits of a SDS demonstration. Even if this was not feasible then it would be possible to plan a follow on mission, which could be used to demonstrate solar dynamic systems before expanding the scale to much larger systems. It should also be noted that for a launch on Energia the photovoltaic baseline is also power limited, the SDS mission would allow the power generated to be increased over the present level. In this section various design concepts are discussed before the proposed design is detailed. System Requirements The Solar dynamic system (SDS) has been designed to supply the same power as the photovoltaic baseline system, i.e. 120 kW electrical output to the satellite. This will allow a direct comparison to
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