the full scale SPS the latter option is inevitably chosen. The disadvantage of this is that the operational feasibility of safe and efficient high power microwave beaming and reception is not demonstrated. A solution to the above problem is to use a large microwave reflector to increase the transmitting aperture. Since reflectors are likely to be less massive than full scale satellite waveguides by almost an order of magnitude the substitution of reflector aperture for waveguide aperture can be favorably made. The critical technical aspect of reflectors is keeping the proper shape and attitude. By using active control a great reduction in structural stiffening mass and complexity may be achieved. Two basic approaches to implementation of actively controlled microwave reflectors are being considered: mechanical and electrostatic. Both methods show great promise and are currently under study by groups sponsored by Langley Research Center and others. (Refs. 3“5) For reflectors of the size required, a mass per unit area of .5 kg/sq meter or less appears feasible. Figure 1 and Table IV present a comparison of typical conventional and augmented aperture SPS prototypes. It may be seen that the aperture augmented conventional prototype has a clear mass and cost advantage. For a sandwich type of SPS (where the solar array, microwave power amplifiers and antenna elements form a planar sandwich) this advantage is slight due to the already very low power density at the transmitting aperture. Because aperture augmentation is not a necessary technology for full scale SPS's (although it does offer some advantages--see Ref. 6) its use on the prototype will increase the risk involved somewhat. However, it is likely to reduce the cost involved to a degree that more than compensates for this. If an aperture augmented prototype meets all the other basic SPS demonstration requirements (and we see no reason why it shouldn't) it will almost surely be possible to construct and operate a conventional SPS because a technically more rigorous test article has been demonstrated. Space does not allow detailed discussion of several other similar choices between risk and cost on the prototype SPS. They include whether or not to build a full scale heavy lift launch vehicle and construction base for the prototype and whether or not to use full scale production methods on various components. It is recommended that similar quantitative methods be used to make the decisions involved. References 1) Kierolff, H.E., "Satellite Power System (SPS) Financial/Management Scenario," DOE HCP/R-4024-13, Oct. 1978. 2) Reiffa, Howard, "Decision Analysis," Addison Wesley, Reading MA, 1968. 3) Lang, Gersh and Staelin, "Electrostatically Controlled Wire-Mesh Antenna," Electronics Letters, 14, 655-656, Sept. 28, 1978. 4) Tankersley, B.C., "Maypole (Hoop/Column) Deployable Reflector Concept for 30 to 100 m Antenna," AIAA Paper 79-0935. 5) Ward, J.C., Editor, "Large Space Systems Technology - 1979," NASA Conf. Publication 2118, Nov. 7-8, 1979. 6) Drexler and Sperber, "High-Power Microwave Optics for Flexible Power Transmission Systems," Proc, of 1980 DOE/NASA SPS Program Review, April 1980.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==