How many apollo 11 astronauts were there?

Every crewed Apollo flight carried three astronauts, and Apollo 11 was no exception. The Apollo command module had three couches, three pressure suits and consumables sized for that number, because the mission profile demanded a strict division of labour: two men to take the lunar module down to the surface, one to keep the mother ship alive in orbit and ready for rendezvous.

Neil Armstrong flew as commander. Edwin "Buzz" Aldrin was lunar module pilot, responsible for the systems of the lander, named Eagle. Michael Collins was command module pilot and flew Columbia alone for roughly a day while his crewmates were on the surface. All three were experienced spacefarers: each had already flown once in the two-seat Gemini programme, which is precisely why NASA assigned them to the first landing attempt.

Armstrong took manual control of Eagle in the final minute of descent to fly past a boulder-strewn area, and stepped onto the surface first. Aldrin followed some twenty minutes later; together they spent about two and a half hours outside, deploying experiments, collecting samples and planting the flag.

Collins's job is the one most often forgotten. Alone in lunar orbit, out of radio contact with Earth on every far-side pass, he tracked the landing site, kept Columbia's systems trimmed and rehearsed the contingency procedures he would have used to rescue the crew, or to come home without them. Without a successful rendezvous his two colleagues had no way back.

The three-man arrangement held for every subsequent lunar mission, so across the six successful landings twelve astronauts walked on the Moon and six others orbited overhead without ever setting foot on it.