Sun Tower Concept: Constellation of medium-scale, gravity gradient-stabilized, RF transmitting satellites. Modular, evolvable low-orbit design scaled to 100 MW per spacecraft. Each satellite resembles a large, Earth-pointing sunflower in which the face of the flower is the transmitter array, and the ‘leaves” on the stalk are solar collectors. Key Features: Modular Construction in both solar-electric conversion and RF transmission Inflatable Fresnel Reflecting Concentrators Gravity gradient stabilization Suggestor/Source: John C. Mankins, NASA Discussion This concept, owing to its extensive modularity, will entail relatively small individual system components which can be developed at a moderate price, ground tested with no new facilities, and demonstrated in a flight environment with a sub-scale test. Manufacturing can be “mass production” style from the first satellite system. Each hexagonal transmitting element, about 16.76 cm across, delivers about 400 W output. These elements are pre-integrated into sub-assemblies for final assembly on orbit. Advantages Disadvantages Modular constniction Simple Gravity gradient stabilization Simple deployment Fits needs of multiple markets Only modest investment before first revenue achieved Intermittent power production Requires constellation of satellites before expenditure of ground site warranted Traveling power beam issue Probably requires ground storage system
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