• Frequency 12 GHz • Power output (nominal) 130 W • Input power level (approximately) 220 W • Efficiency 55-60% • Mass of TWT 1.3 kg • Mass of EPC 2.5 kg • Thermal control passive, radiation The cost per TWT would be in the region of 0.2-0.3 MAU, a factor of 1.5-2 less than that for a communications satellite because life and product assurance testing can be significantly reduced as they would be used for only a few hours, compared to 10 years of continuous operations for a comsat Another possibility might be to use 30 GHz TWTs, although this high frequency might represent a significant technical challenge for the rectenna system. However, if such TWTs could be used, together with the PIC rectenna design and inflatable reflector, this enable an experiment over some 3 kilometres at 60% efficiency or about 2 km at 90% efficiency. If packaging of the TWTs and feed horn cluster on top of the service module was found to be more difficult than anticipated, it would be possible to locate them on a sixth ASAP position adjacent to the Service Module. If the mass margin is large enough, this may also allow a fifth or sixth TWT to be included to increase the transmitted power to around 800 W. Splitting the Service Module from the TWTs and feed horns would also simplify the interfaces considerably. It is interesting to note that even though the TWT solution will not prove anything from a technology perspective, the Powersat Microwave Solution adopted in PART I also uses TWTs. In this sense there could be a direct linkage between the initial demonstrator and a future operational Powersat
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