STS-51-D

STS-51-D was the sixteenth flight of NASA's Space Shuttle program, and the fourth flight of Space Shuttle Discovery. The launch of STS-51-D from Kennedy Space Center (KSC), Florida, on 12 April 1985 was delayed by 55 minutes, after a boat strayed into the restricted Solid Rocket Booster (SRB) recovery zone. STS-51-D was the third shuttle mission to be extended.

On 19 April, after a week-long flight, Discovery conducted the fifth shuttle landing at KSC. The shuttle suffered extensive brake damage and a ruptured tire during landing. This forced all subsequent shuttle landings to be done at Edwards Air Force Base, California, until the development and implementation of nose wheel steering made landings at KSC more feasible.