Shuttle-Centaur G-Prime
This Shuttle-Centaur was a version of the Centaur upper stage rocket designed to be carried aloft inside the Space Shuttle and used to launch satellites into high Earth orbits or probes into deep space. The Centaur G-Prime was planned to launch the Galileo and Ulysses robotic probes to Jupiter. Just months before the Shuttle-Centaur was scheduled to fly, the Challenger disaster occurred, and the project was canceled.