reliability, safety and frequency of service, with commercial aircraft, we should be able to reduce the above costs to under $500 per pound. By 1990 the prospects of doing this within a few years time were sufficiently persuasive to cause the U.S. Defense Department's Strategic Defense Initiative (SDI) office to allocate 15 million dollars towards the development of a prototype SSTO rocket transport. Four major U.S. Aerospace Corporations competed on the first Phase of this effort. Their Phase I findings, rendered last December, were sufficiently optimistic to result in some 57 million 1992 dollars being allocated to the Phase II effort which calls for actually building and flying test vehicles. As of this writing McDonnell-Douglas, now teamed up with Aeroject, Pratt and Whitney, Honeywell and Martin Marietta, are planning for a first flight in 610 days with the second flight some 8 days later to demonstrate turn around time. What all this means is that there now is general agreement among most of our space experts and engineers that the technology exist to build several types of reusable, low cost SSTO rockets that can be made to operate much like conventional aircraft. Many of those now working with this program are confident that this would reduce the cost of transportation into space by at least 2 orders of magnitude. With only a 4 vehicle fleet this would bring space transportation costs to LEO to well under $500 per/lb and per flight costs to about 8 million dollars. Given a slightly larger fleet these costs could come down to below $ 100 per/lb. The prospects that a family of safe, recoverable, reliable, and low cost space transports, with turnaround times and other characteristics equivalent to large aircraft, will be available by the turn of the Century to support any and all types of space programs are now almost a foregone conclusion. If so the associated cost reductions in space these will provide should generate an economic revolution in space activities greater than that brought about by jet aircraft. In any event, they will make large space systems, such as Solar Power Satellites (SPS) much easier to deploy and more cost effective, hence more attractive to governments or private investors. Why is Cheap Lift Now Possible? The initial reaction of most audiences to predictions of such dramatic cost reduction in the near term is incredulity. The first question is invariably, "if this is true why have not governments involved in space operations done this long ago, or at least moved towards achieving these cost goals?" The answer here lies partly in technological progress, especially in materials, but mainly in the fact that today's worldwide fleet of space lift systems were not built from the start to be cost effective transportation vehicles. Instead they are modified military rockets, due to the circumstances existing in the 1960's when most were designed. In the first case - that of technological limitations - the possibility of building low cost transportation systems was limited by the types and weights of structural materials available in the 1950's and 1960's. It was also limited to a lesser degree by rocket engine technology.
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