Endeavour launch attempt scrubbed (17 images)

Space Shuttle Endeavour Commander Mark Kelly (right) waves after departing with his crew and boarding the Astrovan on their way to the launchpad for Endeavour's last flight at Kennedy Space Center, Florida on April 29, 2011. The launch attempt was scrubbed minutes later. Behind Kelly is Pilot Greg Johnston and mission specialists Mike Finke and Roberto Vittori (left). Kelly is the husband of Arizona Congresswoman Gabrielle Giffords, who was recovering from an assassination attempt and at the Cape to watch the possible liftoff. UPI/ Pat Benic

The crew of NASA's space shuttle "Endeavour", lead by Commander Mark Kelly (front right), departs from their quarters to Launch Complex 39A at the Kennedy Space Center on April 29, 2011. Endeavour and her crew were to fly on a fourteen day mission, STS 134, to the International Space Station. The launch attempt has been postponed due to a faulty auxiliary power unit heater. NASA has rescheduled the launch to occur in 48 hours. UPI /Joe Marino - Bill Cantrell

NASA's space shuttle "Endeavour" Commander Mark Kelly gives a "thumb's up" after departing the Operations and Checkout Building at the Kennedy Space Center on April 29, 2011. Kelly was scheduled to fly Endeavour on her twenty fifth and final mission; STS 134, to the International Space Station. Shortly after, NASA decided to postpone Endeavour's launch due to a faulty auxiliary power unit heater. NASA may perform a second attempt in 48 hours. UPI/Joe Marino, Bill Cantrell)

The crew of NASA's space shuttle "Endeavour", lead by Commander Mark Kelly (front right), departs from their quarters to Launch Complex 39A at the Kennedy Space Center on April 29, 2011. Endeavour and her crew were to fly on a fourteen day mission, STS 134, to the International Space Station. The launch attempt has been postponed due to a faulty auxiliary power unit heater. NASA has rescheduled the launch to occur in 48 hours. UPI /Joe Marino - Bill Cantrell