involving the precision folding of thin metal sheet which minimizes labor and material costs (8). A low-cost microwave beam guidance and focussing arrangement, as applied to an active phased array of large area, has been derived. It is based upon angular tracking of a microwave beacon located in the interorbital vehicle by a precision microwave interferometer on the Earth and using the angular tracking data to energize a row and column digitized phase control matrix to control the phase of the output of each radiating module (6). The digitized matrix can also be used to focus the beam and to correct for distortion of the physical dimensions of the array. Transportation The development of the ground-to-LEO shuttle is significant in that it makes highly visible the need for its LEO to GEO counterpart, as well as making it possible to deploy the LEO to GEO vehicle from its cargo bay. Electric Propulsion The general technology for ion engines is in an advanced state and could support the early development of the advanced engines needed for the vehicle. But because of the current lack of a mission for the ion-engine, the current support for its further development is minimal. It is likely to be the longest lead item in any development of the proposed LEO to GEO interorbital vehicle (7,10). EXPANSION OF THE SYSTEM AND OTHER USES Expansion of the System Transit times can be decreased and the amount of material transported increased by adding more transmitting stations on the equator. These do not necessarily have to be of the same size. For example, if nearly 100% duty cycle were desired for the interorbital vehicle, four high-powered transmitting antennas would nearly provide this at altitudes of the vehicle over 15,000 km, but many more lower powered transmitters would be needed for orbits close to the Earth. The duty cycle on the ground based transmitters is also proportional to the number of vehicles that it is servicing. Although it is difficult to imagine at this time what applications would need such a large fleet of large-mass carrying interorbital vehicles, a system utilizing the technology described in this paper could be easily expanded to meet almost any requirement of transferring mass from low-Earth-orbit to geostationary orbit. The larger the amount of material to be transferred, the more attractive the system becomes economically. Other Applications The microwave power transmission technology associated with the interorbital transfer vehicle has other potential applications. One of these is the direct transfer of power from the Earth to geosynchronous orbit. The vehicle with its rectenna could be held in geostationary orbit and serve as a permanent source of power there, serviced whenever necessary by directing the ground array to the “permanent”
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