IUS capability for earth orbital spacecraft

A basic element of the Space Transportation System (STS) is the Interim Upper Stage (IUS) currently being planned by the USAF. The prime use of the basic two-stage IUS vehicle by both NASA and DoD will be to place satellites in geosynchronous orbit. High energy missions such as planetary will be accomplished by three- and four-stage vehicles. Various other configurations such as tandem vehicles in a single Shuttle and multiple spacecraft are being planned. Also under study is a smaller stage that can be flown with other payloads on a space available basis. The various concepts being studied offer economical transportation alternatives to potential users. This paper describes details of the IUS program status, design requirements, concepts and applications to Earth orbital spacecraft.