Airstat Power Transponder Concept: Relay station(s) deployed in the upper atmosphere would relay beamed energy to ground sites, thereby reducing the required ground site dimensions. The relay could also convert frequencies, from laser to microwave for example, to take advantage of the best features of each for safe and efficient overall power transmission. Suggestor/Source: Richard Dickinson - JPL, G. O'Neill (in O'Neill, Gerard, K., 2081, Simon and Shuster, New York, 1981.), et al. Discussion The use of frequencies above approximately 6 GHz is difficult due to the strong attenuation caused by atmospheric water vapor. In particular optical frequencies are effectively blocked prohibiting the use of coherent energy beams. Two general classes of airborne relay have been proposed to address this issue. One utilizes an airborne platform with conductive tethers. The second accepts energy at one frequency and converts it to another, typically lower frequency for retransmission to the Earth's surface. O'Neill suggested the use of the Franklin Institute's STARS solar aerostat as a rectenna site in his book 2081. Dickinson suggested both aerostats and aircraft for the purpose of frequency conversion and coined the term Airstat Power Transponder in 1995. Advantages Disadvantages Could permit laser to be used for 'space' segment of transmission while not bringing beams to surface. Aircraft version is small and difficult to maintain. Aerostat version is difficult to station keep.
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