concern. However, the limited volume provides a fundamental inhibitor to the size of the torus. One possible way around this problem is to reduce the rectification elements to simple patches located at strategic positions across the diaphragm. This is as an alternative to having a complete rectenna able to receive all the incident power. (Figure 5.1-10) This approach would still allow the incident beam power and dynamics to be fully characterised while reducing the complexity of the rectenna. Using rectenna patches would also reduce concerns over damage that might be inflicted during the folding of the rectenna, as noted by Oerlikon-Contraves in the Appendix. Discussions with Texas A&M has confirmed that this rectenna design would be adequate for the needs of an inexpensive/near-term demonstrator. The Electromagnetic and Microwave Laboratory of Texas A&M has also performed a number of experiments of microstrip rectenna designs for both 10 GHz and 35 Ghz applications. Measured conversion efficiencies were 60% at 10 GHz and 39% at 35 GHz. [32] This compares to 85% at 2.45 GHz proposed for space-to-ground applications. Further work is expected to improve these efficiencies. An interesting aspect of the PIC rectenna is that it meets many of the design requirements for an operational space station rectenna design, particularly because it is simple, lightweight and requires little assembly operations. Essentially, the ASAP PIC is about one-half the size needed for space station use, as defined in PART I. The inexpensive/near-term Powersat demonstrator therefore provides an opportunity to experiment with systems that could be directly applicable to future operational Powersat concepts. Rather like the tether discussion above, considerable ground-based technology development has occurred, but space flight verification is still awaited. Inflatable structures have many potential space applications in future space activities, ranging from simple support structures [33] to habitable
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