Space shuttle Endeavour

Space Shuttle Endeavour (R), leaving the Orbiter Processing Facility on its way to the Vehicle Assembly Building (VAB), passes Space Shuttle Discovery at Kennedy Space Center August 11, 2011 in Cape Canaveral, Florida. Space Shuttles Endeavour and Discovery switched buildings as they are being decommissioned with the end of the Shuttle program. (Photo by Roberto Gonzalez/Getty Images)

Space Shuttle Endeavour (R), leaving the Orbiter Processing Facility on its way to the Vehicle Assembly Building (VAB), passes Space Shuttle Discovery at Kennedy Space Center August 11, 2011 in Cape Canaveral, Florida. Space Shuttles Endeavour and Discovery switched buildings as they are being decommissioned with the end of the Shuttle program. (Photo by Roberto Gonzalez/Getty Images)