The flight crew of NASA’s last space shuttle mission sign autographs following a presentation and a question-and-answer session at NASA’s Dryden Flight Research Center at Edwards Air Force Base, Calif., Aug. 23, 2011. Pictured are (from left) Doug Hurley, pilot; Rex Walheim, mission specialist; Sandra Magnus, mission specialist and Chris Ferguson, mission commander. (U.S. Air Force photo/Kenji Thuloweit)