Question

At what rate would oxygen concentration in the gas within the international space station decrease if the system for the electrolytic generation of oxygen failed? Give your answer as mole fraction per day. How many days would it take after the failure for the oxygen in the ISS to fall to 15% assuming it starts at 21%?

Answer 1

Solution:

Intially the data is given at 21% the production mode of O₂ startswhen elctrolytic generation of oxygen fails, the below is the representation of oxygen consumption from standard data.

Production Mode	Oxygen Consumption kg/day	# of crew
Standby	0.20	0.24
25%	2.31	2.8
50%	4.63	5.5
100%	9.25	11.1
100% (day/night)	5.44	6.5

If considering as standby mode and consumption of oxygen by one crew member then the total number of days to reach 15% from 21% is,

0.20 kg/day for 0.24 crew then for 1 crew = 0.20*4 = 0.80 kg / day

at 21% the amount of oxygen generated is 131.25 kg

so for 15% of 131.25 = 19.6875 kg

Consumed oxygen = 131.25 - 19.6875 =112 kg (approx)

(112 kg) / (0.8 kg/day) = 140 days