NASA astronaut Doug Hurley walks up the stairs to the Crew Compartment?s Johnson Space Center Houston.

NASA astronaut Doug Hurley, STS-135 pilot, walks up the stairs to the Crew Compartment Trainer (CCT) mock-up as the crew of STS-135 trains June 29, 2011 at NASA?s Johnson Space Center, Houston. The training marked the crew's final scheduled session in the Space Vehicle Mock-up Facility. Photo credit: NASA photo/Houston Chronicle, Smiley N. Pool