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In the book on the ill-fated Apollo 13 mission there is a chapter that contains an overview of the consumables on board the spacecraft, and whether or not they might pose a problem to the survival of the astronauts. Because the CDR and LMP were scheduled to perform two EVAs on the lunar surface, they had ample oxygen (the atmosphere of the LEM would be vented and completely replaced twice for these EVAs) but the LEM could not support the three men because the CO2-scrubbers were insufficient.

With them having sufficient oxygen I was wondering if the crew might have survived if they had all donned their space suits (or at least the CDR and LMP, taxing the scrubbers less). My reasoning is:

  • The suits can be used inside the spacecraft using umbilical connections that draw on the LEM's ample oxygen supplies
  • For suits worn only inside the craft cooling water (another thing they did not have in excess) is not needed as the flow of oxygen provides cooling
  • If they used the PLSS backpack the CDR and LMP could even stretch the LEMs resources another 14 hours

The only way I can think of that would invalidate this approach was if the suits umbilical connectors also relied on the scrubbers on the LEM to function, but I can't find anything to confirm or deny this.

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    $\begingroup$ Note that there are two problems that must both be solved. Obviously, if there's not enough oxygen in the air, you asphyxiate and die. However, your breathing is controlled by a reflexive action that causes you to exhale whenever the CO2 concentration in your blood or lungs gets too high. That means that, if there's too much CO2 in the air (and the critical concentration is actually quite low), you can't breathe, even if there's plenty of oxygen available. So you do need both the scrubbers and the oxygen supply. $\endgroup$
    – David Richerby
    Jan 7, 2015 at 12:20
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    $\begingroup$ The book states that they had sufficient oxygen in the LEM to last the three of them at least a week. They returned to earth three and a half days after the accident (accident occured April 14 at 03:07:53, splashdown on April 17 at 18:07:41 UTC) so they had practically twice the oxygen they needed. I'm thinking maybe they could have vented the exhaled air from the suits along with the CO2, eliminating the need for scrubbers. I'm pretty sure NASA figured that wouldn't work but I'm wondering why exactly... $\endgroup$
    – JDT
    Jan 7, 2015 at 12:39
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    $\begingroup$ The problem is almost certainly CO2 concentration. According to Wikipedia, 1% CO2 causes drowsiness and 7+% may be fatal. I would guess they didn't have enough oxygen available to do enough atmosphere dumps to keep the CO2 concentration within safe levels. $\endgroup$
    – David Richerby
    Jan 7, 2015 at 13:14
  • $\begingroup$ Is there room enough inside a LM for three people wearing a 60s' space suite?!? Probably they should have been sit and don't move for the whole 3 days of the journey. $\endgroup$
    – jumpjack
    Feb 3, 2015 at 10:58
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    $\begingroup$ I doubt that there were more than two connections for suits in the LM. $\endgroup$
    – Uwe
    Feb 19, 2017 at 15:34

2 Answers 2

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The CO2 scrubbers were certainly an issue to be solved on Apollo 13, but I believe the most difficult problem was that of power. The fuel cells on the spacecraft needed oxygen that was lost in the tank that ruptured. I doubt there would have been enough power available to operate the suits.

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    $\begingroup$ I suspected this to be the right answer, but I couldn't confirm it. However, the EECOM section of the Mission Operations Report (hq.nasa.gov/alsj/a13/A13_MissionOpReport.pdf) states: C02 scrubbing could have been accomplished by operating the CM suit compressor with two canisters installed in the canister assembly in their normal configuration. This technique would have eliminated the makeshift setup plus creating some much needed heat in the CM cabin environment. However, the power requirement for this and the initial unknown condition of the CSM Main Bus B eliminated this setup. $\endgroup$
    – JDT
    Apr 20, 2015 at 15:23
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    $\begingroup$ @JDT I wonder what the tradeoff would have been in terms of CO2 production and oxygen consumption vs scrubbing ability if they'd pulled the suit compressor apart and run it by hand... Although they likely didn't have the tools necessary to do that anyway. $\endgroup$
    – Perkins
    Jun 13, 2018 at 22:31
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The suits themselves did not have CO$_2$ scrubbers. However, they were connected to one of three life support systems:

  1. The portable life support system (PLSS). This is the "backpack" that the astronauts wore on the moonwalks. It held one LiOH cartridge which scrubbed CO$_2$ from the air.

    The first problem is that no mission carried enough PLSS's for all 3 astronauts. Apollo 7 and 8 carried none, 9 carried at least one, 10 carried one, and 11 and later (including Apollo 13) carried two. So this option leaves out one astronaut.

    The second problem is that there weren't enough cartridges. The cartridges had a nominal capacity for one astronaut for 4 hours. There simply were not enough of these cartridges to last the entire mission for 1 person, let alone 3 people.

    Before taking off from the moon, the PLSS's were thrown out of the LM hatch to save weight. It wasn't a factor for Apollo 13, but could be in other scenarios.

  2. The lunar module environmental control system. It had one slot for a PLSS cartridge (described above) and another slot for larger canisters of LiOH. Most of the time the canisters were in use, as they had a much greater capacity. The cartridges were only used when changing canisters, or as a contingency. In any case, the astronauts could connect their suits to the ECS by an umbilical; this was done during landing and takeoff from the moon. If no umbilical was attached to the ECS connectors, it would simply intake/exhaust the cabin air; this is how the ECS operated when they were unsuited.

    The first problem is that there were only connectors for 2 spacesuits. So again you have the problem of one astronaut being left out. What was actually done was to not connect the suits, and simply let the ECS condition the cabin air for all 3 astronauts.

    The second problem is that all of the LM canisters and cartridges combined still did not have enough capacity for all 3 crewmen for the duration of the mission. That's why the CM canister hack was needed.

Trying to combine #1 and #2 merely shuffles the already inadequate supply of LiOH cartridges and canisters. It doesn't gain you any time.

  1. The command module environmental control system. It had its own canisters with more than enough capacity for 3 astronauts for the entire mission. Usually the ECS vented directly to the cabin, but there were also umbilical connectors for 3 spacesuits (used during launch and also for the service module spacewalk on Apollo 15-17).

    The problem here is that Apollo 13's command module did not have enough electrical power available to run the CM ECS.

Thus wearing spacesuits would not have changed the amount of CO$_2$ scrubbing available, and in some instances would have made the situation worse by leaving out a crewman.

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