The Space Tug mission role and program planning.

More than half of the planned payload programs require a velocity increment beyond that nominally provided by the Space Shuttle. The reusable Space Tug system can satisfy this placement requirement and, in addition, can provide other, vital operational services for payloads in the 1980s. To realize maximum operational and economic benefits, it is desired that an orbital propulsive stage such as the Space Tug be available concurrently with Space Shuttle initial operations. Potential tug missions, significant interfaces, system characteristics, and configuration alternatives are discussed in conjunction with salient program planning factors.