VI. Conclusion: Results & Recommendations One of our major recommendations is to intensify ongoing research into 35 GHz transmission technology. We feel that this conclusion is exemplary of the ISU philosophy because it was brought about by our multidisciplinary character. This recommendation is based not only on technical and financial rectenna sizing and power considerations but also on such diverse factors as the reduced heating produced by 35 GHz in the ionosphere and the more likely legal availability of this frequency for allocation. Perhaps an even more important result is what we shall call the US $800 Million “demo barrier.” At this funding level, we feel that space to Earth demonstrations in the next ten years simply do not make financial sense. Instead, we propose that the money be spent on more valuable efforts such as additional space to space demonstrations like the Mir-Progress experiment proposed and ground- based demonstrations such as the proposed Arecibo experiment. Additionally, ground to ground applications should be pursued in order to reduce beaming technology costs for future space to ground demonstrations and to provide such space-based experiments with a much needed ground infrastructure. Furthermore, we feel it makes the most sense to test the environmental and safety effects of beaming through a progressive series of ground to ground and ground to space tests. This step in particular will be pivotal in terms of gaining scientific and public acceptance. To use a five-step terrace analogy, the “demo barrier” can be thought of as a particularly large step equal in height to any of the other three. The ramifications of this “demo barrier” might be better understood within the context of our proposed program schedule (Figure 3). Both the Mir and Arecibo experiments, as well as others like them, would fit into the level “Demo 1 program” in the technological and spacecraft development lines. Then comes the level “Demo 2 program,” which because of the existence of the “demo barrier” will probably not be centered around a single demonstration per se (though the possibility is accounted for) but rather will contain a combination of fundamental research and development, additional “Demo 1 program” type experiments, as well as a thorough series of ground-based experiments. We think that the beaming technology advancements produced by this research-oriented phase will then enable “Demo 3 program” level demonstrations, such as SPS-2000 or our proposed 1 MW class solar power satellite, which we consider to be precursor commercial demonstrations. The first true commercial demonstration would occur at the 100 MW level and is represented by “Demo 4 and SPS development program.” The fifth step would be the launch and assembly of a final solar power satellite prototype leading to the final level, “First SPS Operational.” We feel that this 50-year program represents a realistic portrayal of the length of time required to make large-scale space solar power operational, if a reasonable level of technological advancement is assumed. However, we also considered specific technological advances or milestones that might accelerate this schedule by at least 10 and perhaps as much as 20 years, which have been previously identified as “high-leverage” issues. We believe that perhaps the most important high leverage issue is the advance of laser technology. Lasers offer immense potential for space solar power for numerous reasons, including their high power densities, low divergence, small transmitters and receiver unit size, and potential ability to generate power by means of the illumination of existing solar arrays. However, the technology to do these things affordably does not yet exist. In fact, for the first assigned design example we considered in-depth a laser space to space demonstration for purposes of powering the arrays of an existing satellite, but we determined that the concept was premature. In this sense, the current “demo barrier” is not at US $800 Million but at US $80 Million. However, once this initial large step is surpassed, then because of the great potential for more immediate market applications, subsequent steps become much smaller. As with microwaves, this barrier can be overcome through a combination of intensified research and development and ground-based beaming tests. One interesting application of laser beaming for space solar power is to use a powerful ground-based laser on Earth to transmit power to a remote photovoltaic array. The laser power could be transmitted to ground-based solar arrays, currently existing satellites, or future spacecraft such as Space Station Freedom. In all of these cases the environmental effects of laser beaming should be fully investigated. Therefore in either the microwave or laser space solar power beaming scenario, we believe it is necessary to conduct extensive ground-based experiments. This leads us to the ironic conclusion that
RkJQdWJsaXNoZXIy MTU5NjU0Mg==