Comment on the Possibility of Space Generated Solar Electricity for the Antarctic ANDREW HALL CUTLER1 Broman|l] raises the interesting possibility of using SPS generated power in the Antarctic. He bases his discussion on the ‘reference design' where the SPS is a reliable and mature large scale technology and is emplaced in geostationary orbit. For example, polar orbits, as discussed by Freeman.[2] Geostationary orbit is a special case where the satellite appears stationary in the sky from any location on Earth which can observe it. There are a family of orbits which have related interesting properties. One of these is the Molniya orbit. In a Molniya orbit, a satellite in a highly elliptical orbit with a perigee of a few hundred kilometers and an apogee near geostationary distance passes over points separated by 180 degrees in latitude every twelve hours. The inclination of a Molniya orbit is about 68°, and it has a period of 12 hours. There are similar orbits with periods of 8, 6, 4, ... hours which pass over the same point once per day and pass over 3, 4, 5, ... points equally spaced in longitude each day. These orbits are all at relatively high inclination. For the case of the Arctic or Antarctica, there is much to be said for clean solar power, and this clearly cannot be collected effectively on the ground. A space based collection system beaming power down to Earth could be economically justified here at much higher cost and lower efficiency than would be the case anywhere else on Earth. Solar Power Satellites in Molniya or similar orbits would not provide continuous power unless there were more than one of them. In addition, unlike geostationary SPS's, the transmitting antenna would have to track in one dimension to stay pointed at the receiver. The solar panels would have to reorient for each perigee passage, or drag makeup propellant would be required. There are, however, advantages to such orbits as well. Nongeostationary repeating orbits are much cheaper to reach than is geostationary orbit. The low repeat number orbits also do not experience eclipses, as geostationary orbit does, during the equinoxes. Since the southern hemisphere Molniya orbits are not used at all, and the northern hemisphere ones are only sparsely populated, there would be little interference with communications satellites from a microwave power transmitter. With the microwaves coming down from almost directly overhead, as opposed to near the horizon, a much smaller rectenna could be used for a desired collection efficiency, and the transmitted beam would be less sensitive to weather. In Antarctica, a Molniya t Andrew Hall Cutler, space Engineering Research Center, the University of Arizona, 4717 E. Ft. Lowell, Tucson, AZ 85712 USA.
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