Last updated on April 20, 2014 at 0:02 EDT
439 of 1107

August 13, 2012
NASA astronaut Rex Walheim, STS-135 mission specialist, is lowered into the water March 22, 2011 to train for a contingency spacewalk in the Neutral Buoyancy Laboratory (NBL) in Houston. Photo credit: NASA Photo/Houston Chronicle, Smiley N. Pool