Programmatic effects of utilizing various space tug options

The results are summarized of the computerized (DORCA) analyses of a number of NASA/Non-NASA and DoD payload mission models that have been used in conjunction with studies of the Space Transportation System (STS). The first analysis performed was on the 1971 NASA/Non-NASA and DoD mission models. Subsequent to that, analyses of the June 1972 excursion to the 1971 NASA/Non-NASA mission models were performed. The mission models have two basic versions; i.e., one employing expendable payloads and another employing a best mix of expendable and reusable payloads. Both versions of the models have the same payload deployment schedule. However, in the best mix version, payloads are retrieved from orbit and whenever possible, refurbished payloads are deployed. The analyses were performed to determine the relative merits to different Tug configurations and of Tug combinations employed in several phased development schemes.