This is a cutaway illustration of the Saturn V command module (CM) configuration. The CM was crammed with some of the most complex equipment ever sent into space at the time. The three astronaut couches were surrounded by instrument panels, navigation gear, radios, life-support systems, and small engines to keep it stable during reentry. The entire cone, 11 feet long and 13 feet in diameter, was protected by a charring heat shield. The 6.5 ton CM was all that was finally left of the 3,000-ton Saturn V vehicle that lifted off on the journey to the Moon.