STS-61-F

STS-61-F was a United States Space Shuttle mission planned to launch on 15 May 1986 using Challenger. It was cancelled after Challenger was destroyed earlier that year.

Mission objectives
The main objective of STS-61-F was to deploy the Ulysses solar probe, which would travel to Jupiter and use it as a gravitational slingshot in order to be placed into polar orbit around the Sun. This mission would have marked the first use of the Centaur-G liquid-fueled payload booster, which would also be used on the subsequent mission to send the Galileo probe in orbit around Jupiter.

Due to the use of the Centaur-G and its volatile propellants, this mission was considered to be one of the most dangerous shuttle flights attempted, with Chief Astronaut John Young referring to the two Centaur flights as the "Death Star" flights. The flight was risky enough that commander Hauck even gave his crewmates an option to leave the crew if they considered the mission to be too unsafe.

After the loss of Challenger, most of the crew (sans Bridges, who left NASA in 1986) would fly as the crew of the first post-Challenger mission, STS-26. Bridges was replaced by Dick Covey and a third Mission Specialist (George Nelson) was added to the crew. Ulysses was eventually deployed from Discovery on STS-41, using the solid-fueled Inertial Upper Stage and PAM-S instead of the Centaur, which had been cancelled after the Challenger disaster.