Waste water production/ tank size

Miriam

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I'm currently flying Apollo 11 and came along an odd thing: either our FCs produce too much water or our waste water tank is too small.
According to air/ground transscripts, they made a waste water dump to 0% at 56:56:00, the last one before lunar orbit. The next was done at 84:00:00, about 27 hours later. Now I'm at 82:00:00 and my waste water tank is full. Using the formula given in 4.2.7.2.1 of the operational data handbook, I should have about 30 hours to the next dump with an empty tank (assuming the CSM draws its usual 80 A). So something isn't right here. Ideas?
 

N_Molson

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I'd say 3 hours is quite a small difference, especially "assuming the CSM draws its usual 80A". Are you 100% sure of your power levels for the previous 27 hours ? Or might Apollo 11 did something specific that added load to the FCs ?
 

Miriam

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Those 80A are already rounded up very generously. When I look at the FC loads very sharply, it's rather 70 A (which would give me about 35 hours). But you do have two SPS burns during that period, so I rounded it up to 80 A. I even think that 80 A are still too much, as quite a lot of the load is shared with the batteries during those periods.
Plus that those times are real, flown times. Houston had better ways to predict water production (and surely bigger safety margins then those 10% of remaining waste water tank capacity I get with my rough estimates) and still flew out those 27 hours.
 

n72.75

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I should have an update to fuel cells eventually, based on Faraday's 2nd law of electrolysis. (Amp hours = x mols of H2/O2)

I think we have fairly accurate load levels in the csm right now, but if particular systems were powered off during the mission, that can effect reactant consumption and water production rates.

I'll have to look into this a little further.
 
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