The Centaur G-prime upper stage, designed for use in the Space Shuttle, never flew. After the space shuttle Challenger exploded on January 28, 1986, NASA decided that the Centaur was too risky to fly in the shuttle. Initiated before Challenger, this report describes plans for developing Centaur G-prime as an OTV (orbital transfer vehicle) that would be serviced and refueled at the Space Station. Proposed specific TDMs (Technology Demonstrations Missions) that would involve the Space Shuttle, the Space Station and a Titan-Centaur are described in some detail. These missions would have also required a Co-Orbiting Platform (COP) and ultimately culminated in an orbital launch.