In the second case - the circumstances - the urgency to keep up with Soviet space developments for national security led to using what were essentially modified military munitions - ICBM's with saddles on them - to get into space quickly instead of developing transportation vehicles optimized solely for transportation purposes. These two conditions led to the development, use, acceptance, and almost standardization of multiple stage, wholly or partly expendable, rocket systems which were derived from munitions with all their associated risks and costs. Even when technological advances in materials, in the 1970's, started to make single stage recoverable, reusable, and relatively safe lift systems interesting a combination of resistance to change and demands for ever heavier payloads kept government from exploiting these advances to develop new types of launch vehicles until now. Once billions have been committed to any one approach to doing something it is very difficult for those involved to start over. They would make their expertise obsolete along with the systems they are accustomed to using, and risk becoming redundant themselves. Another major factor in the high cost of space travel has been that associated with the Operations and Maintenance (O & M) of the munitions derived systems. Literally, field armies of people are now required to service and operate these. It has been estimated that it takes over 15,000 employees to refurbish, assemble, test, launch and safely supervise and operate a Shuttle flight. This compares to a U.S. airline average of 140 people per aircraft and some 400 people per aircraft for the most sophisticated military systems such as the Blackbird (SR-71) fleet. Such personnel costs, when coupled with the low turn around rates of shuttles and throw away features of expendable rocket launchers are obviously major factors in their high operating costs. To minimize costs vehicles designed for any transportation mission, including access to and from space, must benefit from simple designs for ease of maintenance and servicing, provide a reliable abort capability throughout their flight regime in the event of non catastrophic failures, and have turn around times equivalent to aircraft. The new family of SSTO transports now being developed are expected to meet these criteria. By some estimates failures in today's launch fleet nearly double the cost of space launches. SSTO rockets can potentially reduce these losses due to their intrinsic reliability. Designs now under consideration can lose one main engine and complete their mission or lose two and still safely abort, similar to conventional aircraft. Given these capabilities the savings in insurance alone become substantial. If the new vehicles are not only designed for safety in all operating regimes, but also for rapid refueling, ground processing, and turn around, and to be able to operate with minimum use of unique base facilities and equipment such as assembly buildings and gantries, the potential cost savings are truly great. All this can now be done, and with existing technology.
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