Space Shuttle Endeavour STS-134 crew (R-L front to back) Commander Mark Kelly, Pilot Greg H. Johnson, Mission Specialist Mike Fincke, Roberto Vittori, European Space Agency astronaut, Mission Specialists Andrew Feustel and Greg Chamitoff walk out of the Operations and Checkout Building to the waiting Astrovan for the ride to pad 39A at the Kennedy Space Center on May 15, 2011 in Cape Canaveral, Florida. NASA has given Endeavour the all clear to embark on its final flight to the International Space Station on May 16. STS-134 will deliver the Express Logistics Carrier-3 (ELC-3) and the Alpha Magnetic Spectrometer (AMS-2) to the International Space Station. (Photo by Joe Raedle/Getty Images)

NASA space shuttle Endeavour lifts off from Launch Pad 39A at the Kennedy Space Center on May 16, 2011 in Cape Canaveral, Florida. After 20 years, 25 missions and more than 115 million miles in space, Endeavour is on its final flight to the International Space Station before being retired and donated to the California Science Center in Los Angeles. (Photo by Joe Raedle/Getty Images)

Jeff Barber of Virginia Beach watches from the water as NASA Space Shuttle Endeavour launches from Kennedy Space Center May 16, 2011 in Cocoa Beach, Florida. (Photo by Roberto Gonzalez/Getty Images)

Crowds gather and watch the launch of NASA space shuttle Endeavour from Kennedy Space Center on the beach May 16, 2011 in Cocoa Beach, Florida. (Photo by Roberto Gonzalez/Getty Images)

The space shuttle Endeavour lifts off from Launch Pad 39A at the Kennedy Space Center, on May 16, 2011 in Cape Canaveral, Florida. Endeavour is on its final flight to the International Space Station before being retired, and donated to the California Science Center in Los Angeles. (Photo by Mark Wilson/Getty Images)