Space shuttle Discovery approaches the device or MDD at the Shuttle Landing Facility at NASA's Kennedy Space Center.

Space shuttle Discovery approaches the mate-demate device, or MDD, at the Shuttle Landing Facility at NASA’s Kennedy Space Center in Florida.

The MDD is a large gantry-like steel structure used to hoist a shuttle off the ground and position it onto the back of a Shuttle Carrier Aircraft, or SCA. The SCA is a Boeing 747 jet, originally manufactured for commercial use, which was modified by NASA to transport the shuttles between destinations on Earth. The SCA designated NASA 905 is assigned to the remaining ferry missions, delivering the shuttles to their permanent public display sites. Discovery’s new home will be the Smithsonian's National Air and Space Museum Steven F. Udvar-Hazy Center in Chantilly, Va. For more information on the SCA, visit http://www.nasa.gov/centers/dryden/news/FactSheets/FS-013-DFRC.html. For more information on shuttle transition and retirement activities, visit http://www.nasa.gov/transition. Photo credit: NASA/Tim Jacobs