The Space Shuttle Crew Escape System consisted of two spring-loaded telescoping poles in a curved housing mounted on the middeck ceiling. A magazine at the end of the pole held eight sliding hook and lanyard assembles. In an emergency, crew members could open the side hatch, deploy the pole, attach to a lanyard, and slide out along the pole to parachute away from the orbiter. The crew escape system was intended for emergency bailout use only when the orbiter was in controlled gliding flight and unable to reach a runway. It gave the crew an alternative to ditching in water or landing on terrain other than a landing site, neither option being survivable.NASA added crew escape systems to the Space Shuttle orbiters after the 1986 Challenger tragedy. This equipment was removed from Discovery after its last flight (STS-133 in 2011) so NASA could release the high-tension springs for safety before delivering the orbiter to the Museum. The pole assembly was reinstalled in Discovery; the springs remain in storage.