So, out of the 24 men that went to Moon orbit and back during the Apollo program, just three of them did the trip twice, but landings where always done by a different crew.

From the politician's point of view, it stands to reason that sending a fresh crew each time would provide the US with a bigger pool of heroes to show around. It would also add some variety to something that was old news very quickly. I can imagine people watching TV and commenting "There's that Buzz guy jumping in the Moon again".

From the point of view of crew management, it also makes sense to have a fresh crew on each flight, both from the point of view of the astronauts that miss their chance to flight (Hey, Buzz's been up there three times already, why cant I go at least once?) and from the poor guy that's sent once and again to the same barren wasteland.

But, from a mere Space Agency point of view, is there anything to be gained from sending a new crew each time (perhaps training, or researching how a new team will do things differently). It would have made sense if they sent scientist specialst before Schmitt went on Apollo 17, but the other guys where all pilots.

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    $\begingroup$ Deke Slayton's book may have some insights, but I don't recall the essential reason for training multiple crews from NASA's viewpoint. While we never lost an Apollo crew, each mission was certainly risky enough that you might not want to go more than once or twice. Also, each crew trained very intensively for months leading up to their missions; doing that six times in a row would be quite a strain on both an astronaut and their family. $\endgroup$ May 31, 2018 at 19:27
  • $\begingroup$ @RussellBorogove I guess that intensive training would in fact be a good motivator for repeating crews, you save a lot in simulators when the guy has already been there and experienced the actual thing. $\endgroup$ Jun 1, 2018 at 5:51
  • $\begingroup$ @peterh It's all about improving the question to help generate better answers! $\endgroup$
    – uhoh
    Jun 1, 2018 at 12:13

2 Answers 2


Apollo 7-12 were at very short intervals:

Apollo 7: Oct 1968
Apollo 8: 2 months later
Apollo 9: 3 months later
Apollo 10: 2 months later
Apollo 11: 2 months later
Apollo 12: 6 months later
After that, the schedule stretches.

NASA likes to take their time training the astronauts for each specific mission. Mission training can be a year or more. So they needed 7 crews for Apollo 7-12.

NASA also uses backup crews: 2 crews train for each mission. If there's an issue (one of the astronauts has an accident of gets sick just before launch) he can be replaced without changing the mission schedule.

Several astronauts had 2 Apollo missions:
John Young: 10, 16
Eugene Cernan: 10, 17
David Scott: 9, 15
James Lovell: 8, 13

Apart from Lovell's flights 16 months apart, these missions are at least 2 years apart.

NASA had a fairly large number of astronauts by then (66 were selected as of 1967), as they were counting on more Apollo missions than the 12 that were carried out in the end. Good personnel management suggests you give as many people as possible a chance at a mission, instead of having just one crew have all the fun. You also want to give as many people as you can manage spaceflight experience because those people will be invaluable in developing the next generation of spacecraft.

  • $\begingroup$ Yes, large number of astronauts was one of the mai reasons, I think. People were training for several years, so they wanted to feel it was wotrh. After end of Apollo program, 3 Scylab missions had 2 veterans and 7 rookies in their crews, Apollo-Sous had 1 veteran and 2 rookies. And even after that several astronauts didn't fly in space until Space Shuttle program in 80's. And several Apollo-era astronauts resigned from NASA without spaceflight. $\endgroup$
    – Heopps
    Jun 1, 2018 at 9:47
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    $\begingroup$ "...instead of having just one crew have all the fun." The OP doesn't suggest "one crew" be reused for all missions. "Good personnel management suggests..." do you have any source to back this up in the context of something so uncertain, technically challenging, and with so much at risk as going to the Moon in the 1960's? This isn't just a trip to the annual sales convention. $\endgroup$
    – uhoh
    Jun 1, 2018 at 12:08
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    $\begingroup$ Considering the incredible lengths NASA went to minimize thousands of independently named and characterized risks, the OP (and I) would like to know why such a high rate of "never been on an extended cis-lunar mission before" personnel? So far I don't think you are really answering this question, at least not in a well-supported way. $\endgroup$
    – uhoh
    Jun 1, 2018 at 12:11
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    $\begingroup$ Considering NASA didn't plan on just ending it on the Moon, and intended more ambitious missions, like Mars, which would be definitely less frequent than lunar, this would be a vetting process to pick the best of the best. The Mars crew would most definitely be composed of Moon veterans. $\endgroup$
    – SF.
    Jun 1, 2018 at 13:03
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    $\begingroup$ NASA crew assignments are a contentious, mysterious, political, drama-filled, shadowy thing and always have been. Read Dragonfly for some stories about Shuttle/Mir era, Mike Mullane's book for early Shuttle era stories. $\endgroup$ Jun 1, 2018 at 22:32

It was important to increase the sample size for medical tests on the astronauts themselves. These still are the only people that have gone outside of low earth orbit, ever. The data, especially on radiation poisoning and Moon EVA human factors, is vital for new missions to the Moon or Mars.

  • $\begingroup$ Do you have a reference that states this was a factor in crew assignment? $\endgroup$ Aug 16, 2019 at 16:16
  • $\begingroup$ @OrganicMarble This is close to a direct quote (from memory) from a presentation on ISS astronaut medical data. Even with the ISS astronauts, there are still problems with small sample sizes. $\endgroup$ Aug 16, 2019 at 16:20
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    $\begingroup$ I deeply sympathize, as a former JSC engineer often the hardest part of answering questions is finding a reference for something I know to be true. Sadly though, without that, this is just "something some guy on the internet said". I'm sure you've heard "In God we trust, all others bring data" $\endgroup$ Aug 16, 2019 at 16:40

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