Wikipedia:Reference desk/Archives/Science/2022 February 6

= February 6 =

Apollo 13
On Apollo 13, did the severe cold conditions (caused by the need to turn off all non-essential systems such as heating in order to conserve power) contribute to the premature failure of the CO2 scrubbers, as was the case on the Johnson Sea Link? 2601:646:8A81:6070:6C67:B2B6:D530:3F2A (talk) 10:20, 6 February 2022 (UTC)
 * My understanding is the scrubbers did not fail prematurely. The LEM filters were only designed to support two men for two days, and it instead had to support three men for four days, thus the need for adapting the filters from the command module.  Do you have a source that says they failed prematurely? RudolfRed (talk) 22:32, 6 February 2022 (UTC)
 * That's what I was asking about -- was it only the increased load, or did the cold contribute as well? 69.181.91.208 (talk) 07:41, 7 February 2022 (UTC)
 * The lithium hydroxide in the canisters could only bind a limited amount of CO2 and needed to be replaced regularly. At some point, the crew ran out of the limited supply of canisters that fit into the LM system. The scrubber itself did not fail, and while most LM systems were shut down, this would not have included the scrubber. I suppose (but cannot find definitive confirmation) that the scrubber may have included an internal heating system. But another issue is that the temperature-dependency properties of LiOH granules are rather different from those of the Baralyme used in the Johnson Sea Link scrubber. At a relative humidity in the air stream above 40%, LiOH is even reported to have a higher CO2 absorption capacity at lower temperatures. --Lambiam 09:55, 7 February 2022 (UTC)
 * So are you saying that the cold, damp conditions which prevailed in the LM actually stretched the scrubber's capacity longer? 69.181.91.208 (talk) 10:33, 7 February 2022 (UTC)
 * It would not have changed the capacity, which is only dependent on the stoichiometry of the reactants (which is to say, there are only so many formula units of LiOH available to react with CO2), and temperature doesn't change that. The temperature would have affected only the kinetics of the reaction, which is to say the speed at which the reaction would have happened.  AFAIK, the problem was not the kinetics, it is that they were literally out of usable LiOH in the LM scrubber system; which is why they needed to use the Command Module canisters.  -- Jayron 32 13:39, 7 February 2022 (UTC)