HIGH-POWER MICROWAVE OPTICS... stantially to the typical user cost of SPS electricity. By breaking up the power beam into smaller blocks, transmission lines can be made shorter, thereby lowering their construction costs and increasing their efficiency. Smaller power blocks will increase market penetration by opening smaller markets (including those in the Third World), by lowering costs of service to decentralized markets, and by smoothing introduction of SPS power into the grid. In the geometric optics approximation (appropriate to larger phased arrays and larger beam powers than those discussed above), defocused optics can map a tophat power density distribution at the phased array into a tophat distribution at the ground. On the ground, this cuts land requirements by about a factor of three, given a constant peak power density, while increasing power conversion efficiency. In space, this cuts phased array area per unit power by a comparable factor. Diffraction will reduce this performance, but the cost savings should still be large enough to reduce busbar costs substantially. FIGURE Is A gravity-gradient stabilized configuration, incorporating a rotating solar mirror and no rotating electrical joint. Length about 100 kilometers.
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