The Space Shuttle is the next logical step in space transportation. As pointed out in Figure 19, a principal objective of future space systems development is reduction of cost of performing space applications missions, in order to provide economic practicality for these applications of a level commensurate with largescale benefit. Major reduction in cost can only be achieved by working on all three aspects of the high cost of space flight.

The most promising way to attack this problem is the development of a reusable round-trip transportation system. In addition to reductions in launch costs, the operational characteristics of such a system will permit reductions in payload and mission-operations costs.

Studies conducted under contract to NASA as part of the Grumman/Boeing space-shuttle team effort, and other conducted under Boeing-sponsored research, have examined a broad spectrum of alternate approaches to round-trip reusable and partially reusable space transportation. Many concepts have been proposed as alternatives to the two-stage fully reusable space-shuttle system with the objective of reducing costs. However, the analysis has shown that these concepts incur penalties in cost per flight, and operational restrictions due to jettisoned equipment, which more than offset potential development cost reduction. Figure 20 illustrates the fully reusable concept identified as preferred by Boeing studies and indicates approximate size and weights.

Low cost per flight will allow the space shuttle to supplant existing expendable launch-vehicle systems (Figure 21), eliminating program costs for sustaining these systems in operational status, as well as reducing direct launch cost. Although the space shuttle payload is approximately equal to that of Saturn IB, its routine operational capability will allow modularization of heavyweight missions, such as those presently launched on Saturn V.

Boeing analysis showed that the Space Shuttle has significant money-saving potential (Figure 22). The Boeing-sponsored economic analysis was patterned after methods used to assess market potential of commercial aircraft. Based on traffic projections of approximately current levels, the analysis showed a total savings of about $8 billion over the first 10 years of space shuttle operations. As noted, the analysis included only NASA and Department of Defense missions and considered payload savings resulting only from payload recovery and reuse. Results were considered quite conservative, since other potential sources of savings have been identified.