United States orbital transfer vehicle programs

Abstract

The United States will rely on five orbital transfer vehicles to carry spacecraft to higher energy orbits than achievable by the Space Shuttle or various Expendable Launch Vehicles (ELV). These vehicles are the Payload Assist Module-Delta (PAM-D), an upgraded version designated PAM-DII, the Inertial Upper Stage (IUS), the Transfer Orbit Stage (TOS), and the Orbital Maneuvering Vehicle (OMV). Development of these vehicles have evolved through contrasting cultures of government and commercial management. The spectrum of their capabilities range from providing spacecraft with only a preprogrammed perigee velocity additions to man-in-the-loop remote controlled spacecraft rendezvous, docking, retrieval and return to a space base; either the Shuttle or the Space Station Freedom. The PAM-D, PAM-DII, and IUS are now nearing maturity. Their characteristics, flight record, costs, and projected future uses are defined. The TOS and OMV are currently in development with first uses scheduled in 1992 and 1993, respectively. The TOS is being commercially developed while the OMV is government developed. The TOS and OMV capabilities, constraints, and costs are reviewed.