In Apollo 11 Flight Journal the following is stated:

The crew will make re-entry without suits or helmets on. Although this was a controversial decision on the first Apollo flight, Apollo 7, when the crew wore suits but no helmets contrary to MCC's advice, by now it is regarded as routine.

According to wikipedia, during Apollo 7

They perceived a risk that their eardrums might burst due to the sinus pressure from their colds, and they wanted to be able to pinch their noses and blow to equalize the pressure as it increased during reentry.

From Apollo 7 Flight Journal:

258:23:57 Slayton: Okay. But the mode we wanted was to have them on without being latched down to the neckring. [Pause]

258:24:04 Schirra: Deke, I can't get my hand in there, besides a handkerchief, and we're not at all safely braced for landing. We'll evaluate as carefully as we can. [Pause]

258:24:17 Slayton: Okay. I think you ought to clearly understand there is absolutely no experience at all with landing without the helmet on.

258:24:24 Schirra: And there is no experience with the helmet either on that one.

258:24:27 Slayton: That one we've got a lot of experience with, yes.

258:24:30 Schirra: If we had an open visor, I might go along with that. [Pause]

258:24:35 Slayton: Okay. I guess you better be prepared to discuss in some detail when we land why we haven't got them on. I think you're too late now to do much about it.

258:24:43 Schirra: That's affirmative. I don't think anybody down there has worn the helmets as much as we have.

258:24:50 Slayton: Yes.

258:24:51 Schirra: We tried them on this morning.

258:24:53 Slayton: Understand that. The only thing we're concerned about is the landing. We couldn't care less about the reentry. But it's your neck, and I hope you don't break it."

Was there any kind of official report with risk assessment to implement easing off of the rules and allowing reentry without being pressure suited? Did they consider Soyuz-11 scenario (which happened later in June 1971)?

  • $\begingroup$ This is a good question! $\endgroup$ – user2705196 Dec 5 '19 at 14:19
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    $\begingroup$ I remember reading that the Apollo 13 crew didn't wear their suits during re-entry. I might be wrong though. $\endgroup$ – Star Man Dec 6 '19 at 2:55

Partial answer: They stopped wearing suits for Earth re-entry after Apollo 7, and there is a notable lack of literature why.

  • The Apollo Program Summary Report says Entry and landing.- The Apollo 7 crew performed entry while suited but with helmets and gloves removed. The crewmen had developed head colds, and removal of the helmets provided a means of clearing the sinus and inner ear cavities. Follow-on crews entered the earth atmosphere with their suits stowed under the couches.

  • The Apollo 7 Mission Report states without elaboration

    The suits, without helmets and gloves, were worn during entry.

  • Apollo Experience Report: Command-Module Crew-Couch/Restraint and Load Attenuation Systems D-7440 describes how the crew couches are supposed to work with the suits during re-entry, but does not discuss being unsuited during re-entry.

  • It is not discussed at all in the Apollo Experience Report: Development of the Extravehicular Mobility Unit D-8093.

  • Biomedical Results of Apollo mentions the incident, but neither describes the follow-up nor provides any pertinent references.

  • Neither the Apollo 7 incident nor follow-up are mentioned in the 1355 pages of The Apollo Spacecraft: A Chronology.

  • A search of the NASA Technical Reports Server -- which is supposed to include all publicly-available NASA documentation -- yields no relevant reports or assessments.

  • The 701-page A Continuing Bibliography on Aerospace Medicine and Biology lists no appropriate articles.

My guess is that the suits were unlikely to help in any situation that would compromise the CM during re-entry, and that the astronaut corps felt that the suits were more of an encumbrance than they were worth during re-entry.

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  • $\begingroup$ +1 for all the research, I'm surprised by your comment "the suits were unlikely to help in any situation that would compromise the CM during re-entry" given the Soyuz 11 tragedy. I might be missing something though, do you mean specifically after undocking etc that pressures can be checked to be safe prior to stowing suits and then committing to re-entry? $\endgroup$ – Puffin Apr 4 at 9:46
  • $\begingroup$ As an IVA suit, they were connected to the CM environmental control system. Most scenarios that lose cabin pressure will also compromise the ECS. There would be two oxygen purge systems left: not enough for three people, not wearable in the crew couches, and need to be manually switched over from the ECS. Sudden loss of pressure is easy for crew to notice (Challenger), slow leak is not (Soyuz 11). Even with the Shuttle ACES suit -- which had an OPS on each suit -- most astronauts had gloves off and visors open because the suits were so burdensome. $\endgroup$ – DrSheldon Apr 4 at 13:23

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