In space, no one wants any surprises. To avoid being caught off guard where no one can hear you scream, every step of every space mission is practiced on the ground (or underwater, or in the air). We take a look back at NASA's decades of creative methods of astronaut training.

Astronaut Rex Walheim practices spacewalking in the Neutral Buoyancy Laboratory near NASA's Johnson Space Center in 2010, in preparation for working on the exterior of the International Space Station. Walheim is the mission specialist for STS-135, the final flight of the space shuttle Atlantis (and the last shuttle flight ever), which took off on July 8.

Below: Sandy Magnus, STS-135 mission specialist, gets fitted for her emergency spacesuit on March 29, 2011.