by clouds. However, the relatively small size of a laser receiver may make possible the use of several interconnected sites which would negate cloud coverage problems over a particular site, by switching the beam to a site that is clear of clouds. A possible laser system approach is presented in Fig. 8 which locates the laser in low Earth orbit with reflectors only in GEO to minimize transportation requirements to the higher orbit. A guideline for the definition of the reference system stated that the system would be constructed of Earth materials. Nevertheless the concept of using extraterrestrial materials for SPS construction was pursued enthusiastically by several groups. One scenario for constructing the SPS from lunar materials is depicted in Fig. 9. In addition to conserving Earth materials the basic rationale for the use of extraterrestrial materials is straightforward, that is, the energy required for transport from the lunar area to geosynchronous orbit is considerably less than from the Earth. Consequently transportation costs would be reduced, and the development of the large space freighter would be unnecessary. These advantages would have to be traded off against the “up front" costs of establishing and operating the lunar base, and developing the techniques associated with producing the necessary building materials on the moon. It was also not clear that the remaining material required from Earth would not require a new launch vehicle anyway, albeit of smaller size. Nevertheless, it would appear that future SPS studies should continue to give consideration to the extraterrestrial materials option.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==