Skylab 4 Commander Gerald P. Carr is fully suited as he prepares to enter spacecraft 118 (the Skylab 4 vehicle) at the start of a high altitude chamber test at the Kennedy Space Center in this image from Aug. 6, 1973. Also participating in the test were scientist-astronaut Edward G. Gibson, science pilot, and astronaut William R. Pogue, pilot. The Skylab 4 spacecraft was moved to the Vehicle Assembly Building on Aug. 12, where it was mated with the launch vehicle.
See this TED-Ed animation, narrated by Carr, as he discussed his life as an astronaut.
Image Credit: NASA