Carbon Dioxide Problem

[PhantomWolf]

Okay I have been trying to revise my Apollo 13 page and hit a snag.

According to the information I have found on the LM ECS (Environment Control System) there were two LiOH canisters, a large primary canister and a smaller secondary canisters, identical to the PLSS canisters. Now my problem is trying to figure out what they had onboard as the sources don't make it clear. One tells me that they has 4 primary ECS canisters and 4 secondary ones from the suits (including backups), but they started having problems about 36 hours after the explosion. A second source tells me that the large canisters had 41 person hours of life and the suit canisters 14 person hours. 36 x 3 = 108 person hours, so the number of canisters can't be more than that. If they had 4 large canisters, that would give them 164 hours, plus another 56 from the suits, so 220 person hours, meaning that they wouldn't have experienced CO₂ build up for 72 hours, not 36. If they had a spare large canister and two suit canisters, plus the ones already in the system then they would have had 124 hours, still more than the 108 hours that had passed. I suspect that they actually had just a single large canister and three suit canisters (one in the ECS and two from the PLSSs) which would have only given 83 hours, meaning that at the 108 point they would have had a 25 person hours build up of CO₂. This would make sense since most sources say that the spare LM ECS canisters and PLSS LiOH canisters were all packed in the MESA, and so would have been imposible to get too. However, I'd like to know for sure exactly what they had onboard and what the story was since it seems that the sources I have found don't actually spell it out and indeed seem to conflict with their accounts and the math...

[PhantomWolf]

Hmmmm, okay I kept looking and a third source says that they keept the two canisters on line for 107 hours allowing the CO₂ levels to increase above normal, but that they had a second primary on hand that they keep in reserve incase the CSM LiOH fix didn't work. This seems to ignore the fact that they would have has an extra 28 person hours minimum (maybe 54 if pushed as they seem to suggest the others were) from the two PLSS canisters that were stowed in the LM. Add to the spare large canister, this could have provided another 134 odd hours if they has streched them like they did the first ones, or another 44 hours, nearly 2 days to solve the problem..... I'm confused.

[PhantomWolf]

Note here that I'm not saying they didn't need to jerry-rig the CSM canister, just that it shouldn't have been as big a problem as it's often made out. They still would have needed the mocked-up system for the last 17 hours, as the LM's supplies could only have reached hour 126 of the 143 hour mission, but that they had plenty of time to have gotten the solution working because they only appeared to have used half the LM supplies.

[PhantomWolf]

Okay the italiced part is what I am adding to the page:

Still even with that news, things still weren't going to be easy. Carbon Dioxide was steadily building up in the cabin of the LM and the main supply of Lithium Hydroxide canisters were the wrong shape. This was because different manufacturers made the CSM and the LM, and each used different systems for the Environment Control. While the CSM used a large square canister, the LM ECS used two round canisters; a large primary was to last for at least 41 person hours, and a smaller secondary, identical to the PLSS ones, that was to last 14 person hours. The secondary canister was placed in parallel to the primary, but was generally only used when the primary was being swapped out. On a normal mission the primary canister would have been swapped out after around 18 hours of use for two the two astronauts, however with three crewmembers, they were pushing these canisters to their limits and beyond. With all but one of their spares stowed safely in the MESA, mere centimetres away, but impossible to reach, a decision was make to keep that one spare large LM canister and both PLSS canisters in reserve just in case a solution failed, and instead try to adapt the square CSM canisters to the round LM ECS.

comments?

[Kiwi]

I'll look up my "Apollo XIII" CD-ROM tomorrow to see if it helps, but in the meantime you have a typo: for two the two astronauts.

To clarify, it might be best to say something about that's what was intended for the two astronauts in the LM.

[Kiwi]

No luck. While the CD-ROM is detailed in places, this is not one of them. It only says there were sufficient canisters for the remainder of the mission, then goes on to the incompatibility of the fittings.

One other thing of interest about Apollo 13 is that Sy Liebergot, in his book Apollo EECOM, page 148, says,
Actually, LM lifeboat procedures had already been developed a year before the Apollo 13 disaster occurred...
and goes on to explain how they were developed after an Apollo 10 simulation in which a hydrogen leak in the CSM and the loss of all three fuel cells caused the crew to be lost.

He also says,
Since it is not mentioned in his book, Lost Moon, Jim Lovell probably was unaware of this critical planning activity.