At the Shuttle Landing Facility space shuttle Discovery hovers above the ground inside the device.

At the Shuttle Landing Facility at NASA’s Kennedy Space Center in Florida, space shuttle Discovery hovers above the ground inside the mate-demate device. Operations are under way to position Discovery on top of a Shuttle Carrier Aircraft.

The device, known as the MDD, is a large gantry-like steel structure used to hoist a shuttle off the ground and position it onto the back of the 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. NASA 905 is scheduled to ferry Discovery to the Washington Dulles International Airport in Virginia on April 17, after which the shuttle will be placed on display in the Smithsonian's National Air and Space Museum Steven F. Udvar-Hazy Center. 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/Dimitri Gerondidakis