Colonel Carr was one of the 19 astronauts selected by NASA in April 1966. He served as a member of the astronaut support crews and as CAPCOM for the Apollo 8 and 12 flights, and was involved in the development and testing of the lunar roving vehicle which was used on the lunar surface by Apollo flight crews. Carr was subsequently commander of Skylab 4 (third and final manned visit to the Skylab Orbital Workshop) launched November 16, 1973, and concluded February 8, 1974. This was the longest manned flight (84 days, 1 hour, 15minutes) in the history of manned space exploration to date. From February 1974 until March 1978, Colonel Carr and his Skylab 4 teammates shared the world record for individual time in space: 2,017 hours 15 minutes 32 seconds, and Carr logged 15 hours and 48 minutes in three EVAs outside the Orbital Workshop.