This answer poses the possibility of an emergency that would require Apollo astronauts to spend the rest of the mission in their suits:

A hole in the CSM might be more of an issue, since large portions of the pressure vessel are inaccessible during flight. If such an inacessible hole happened, it's likely the crew would have gone to suits, on umbilicals, and taken the very next opportunity to aim for Earth.

At what phase of the mission would such an emergency occur that would maximize the amount of time that the Apollo astronauts would need to spend in their suits?


There briefly was an answer (deleted by its own author) about how running out of supplies would be a limiting factor. True, but that's not how I've asked to approach the question ("what phase of the mission..."). Therefore, I've added the tag.

I had previously said that "Whatever Apollo 13 did" is not a satisfactory answer. My chief concern is that an acceptable answer is backed up by some sort of analysis, and not just idle speculation. You can do the calculations yourself (as in PearsonArtPhoto's answer), or you can cite NASA documentation, just as long as someone has run the numbers. However, if you're going to use a quote from Jim Lovell or Gene Kranz, then you ought to show that they were citing actual analysis rather than making a (very) educated guess.

Will the Apollo 13 scenario end up being the answer? My gut-level feeling is that it will be very close to the worst case, but that there still is an even longer scenario.

  • $\begingroup$ My answer to this question quotes a NASA document that says the maximum duration was 115 hours. space.stackexchange.com/questions/33882/… Posting as a comment because the derivation of the number isn't given. $\endgroup$ Commented Apr 30, 2019 at 1:32
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    $\begingroup$ @OrganicMarble: Thanks. I did find what you quoted in a paper cited in your previous answer. Unfortunately, that paper's references and bibliography don't provide a source to their claim. At least we have a start on an answer. $\endgroup$
    – DrSheldon
    Commented Apr 30, 2019 at 2:07
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    $\begingroup$ I've found Tech Note D-6847: Apollo Experience Report - Abort Planning <klabs.org/history/apollo_experience_reports/…> which may help $\endgroup$
    – DrSheldon
    Commented Apr 30, 2019 at 6:38
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    $\begingroup$ Also maybe useful: Not all segments of Apollo trajectory were free-return. space.stackexchange.com/a/5591/26446 $\endgroup$
    – DrSheldon
    Commented Apr 30, 2019 at 16:44

1 Answer 1


Let's think this through. Some potential scenarios:

  1. The service module to rupture at the same time as the CM. It seems unlikely that anything that killed a service module could have been survivable from reentry that also caused a puncture, but... The worst case for this scenario is probably near that of Apollo 13, a few hours extra. Apollo 13 was about 87 hours from the incident to landing, so let's say 92 or so is the max.
  2. Astronauts on the Moon, hole appears in CSM. The crew would have to leave the lunar surface, dock, and then return to Earth. I can't find an exact time, but let's assume at least 2 hours to get from an EVA back to the command module. Let's say another 3 hours to prep for ascent (Including waiting for the right time). Apollo 11 took 5 hours from launch to discarding the ascent stage. Then another hour to line up and prepare for the return to Earth, and 60 hours to return to Earth, for a total of 70 hours
  3. Something happened near the beginning of the mission, just after TLI. With the main engine working, they could actually turn the craft around using just the main CSM engine, and thus it wouldn't be a significant amount of time. If for some reason that wasn't an option, the time would be much larger, maybe around 120 hours. But that could only happen if the debris event also happened at the same time as a failure to separate, and failures to separate spacecraft are very rare. I can only think of one in recent history, Zuma, and that was likely because it was a one off test.

So I know you don't like the Apollo 13 answer, but that is actually fairly close to the worst case scenario. A worse case of a truly diabolical situation could have lasted as long as 120 hours. But more realistically I would say 70 hours or so.

  • $\begingroup$ I think your option #3 is a better answer. Suppose the trouble happens right after TLI, which was done by the restartable engine of the 3rd stage. Suppose part of the trouble includes the failure of the CSM to separate from the 3rd stage. You couldn't use the SM or LM engines, but you could use the 3rd stage and RCS engines to make corrections to a free-return trip. Upon return to Earth, you'd still be able to separate the CM and land. $\endgroup$
    – DrSheldon
    Commented Apr 30, 2019 at 5:12
  • $\begingroup$ This leads to a separate question, but in scenario #2, was there SM fuel margin to keep the LAM docked for the trip home (approx a 10% increase in mass)? $\endgroup$
    – amI
    Commented Apr 30, 2019 at 9:04
  • $\begingroup$ Failure to separate is an interesting situation that I hadn't considered. Hmmm... $\endgroup$
    – PearsonArtPhoto
    Commented Apr 30, 2019 at 9:46
  • $\begingroup$ Some actual times for your scenario 2, based on Apollo 11: ascent prep takes about an hour, and the worst-case wait adds another hour. A crew following regulations is never more than a 30-minute run or drive from the LM, because that's how long their emergency oxygen supply is good for. A routine EVA closeout takes less than 30 minutes from starting up the ladder to LM repressurization; in an emergency, that could be shortened. The three and a half hours from launch to docking can't be shortened, but almost all of the steps after that prior to jettison can be eliminated. Total time: 7 hours. $\endgroup$
    – Mark
    Commented May 2, 2019 at 22:29

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