The strawman model study guideline The results of the CDEP give us a basic reference for interpolation of the growth of SPS from the present. The first problem the working group faced was that each member researcher could not find a definite image of his research related to the CDEP reference system. Then it was proposed to conceptualize what they would consider a more realistic SPS in terms of their research subjects. As a result of discussion, the size of the model should be as small as can be realized by the present space technology and space infrastructure, but should be large enough to be considered as an SPS. A 10 MW model once studied by an industry study group was known and reexamined by the group. The original concept was substantially a smaller version of the Reference Model, which was built in a low earth orbit and transported to the geosynchronous orbit for operational tests. The mechanical configuration and power transmission method are similar to those of the Reference System, which used solar panel and antenna structures connected by a gimbal mechanism with a slip ring [4], In the guidelines for the new 10 MW model study, a low earth equatorial orbit is chosen for all the operations and the gimbal mechanism is eliminated. The primary reason to use the orbit is to make it possible to use launch systems available in or before 2000 Consequently all the rectennas will be sited in developing countries located in the equatorial zone. This assumption implies the objective of this system is more than an experiment and could include evaluation of a pilot plant of SPS for power supply to the earth. Overall, the concept emphasizes demonstration of electric power supply to customers at the earliest opportunity rather than being designed first for research and development. This model of SPS is intended to be realized as soon as possible. In this respect, most of the technologies employed are conventional or available in the near future. This means that the performance of the SPS is allowed to be relatively low, for example with high specific mass, low efficiencies of power conversion and transmission. The few exceptions are the significant amount of space assembly work with multiple launches, and high technology for beam control. The latter is concerned with the operational constraints due to low earth orbit that is the most crucial point of this system for final evaluation. Although the microwave frequency to transmit microwave power to a rectenna on the ground is the same as the Reference System, the beam has to sweep more widely to track ground rectennas while it passes over them. SPS 2000 system There have been several general configurations proposed at the initial study phase. The following system designated as SPS 2000 is based on one which features the gravity gradient attitude stabilization of the entire system.
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