ISRU atmosphere harvesting. Robert Dyck. Mars Atmosphere. CO 2 95.23% N 2 2.7% Ar 1.6% O 2 0.13% CO 0.07% H 2 O 0.03% Ne 0.00025% Kr 0.00003% Xe 0.000008% O 3 0.000003%. CO 2 freezer. filter dust/fines compress air to 10 bar freeze to 170°K (-103.15°C) Vapour pressure:
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compress air to 10 bar
freeze to 170°K (-103.15°C)
CO2 = 0.1 bar
H2O = 3.4x10-277 mbar
As pressure drops, compressing more air to maintain 10 bar
Continue until pressure doesn’t drop any more
Gas will be primarily N2 & Ar, ideal for diluent gas in habitat.
After freeze: CO = 0.045%, O2 = 0.096%
CO: 0.001% symptoms of poisoning, 0.5% fatal
O2 + 2 CO → 2 CO2 with catalyst
2 O3 → 3 O2
After compressor stops, continue to heat catalyst until CO below detection threshold of sensor.
After catalyst heater is turned off, continue to run freezer until pressure stops dropping.
Release mix gas to storage tank and rapidly pump out.
Release residual pressure to Mars, then reseal.
Heat dry ice to sublimate, use pressure to fill CO2 tank.
Resulting gas, by volume: Breathing gas:
CO2 0.74935% CO2 0.52%
N2 61.0% N2 42.4%
Ar 36.1% Ar 25.1%
O2 2.1% O2 32.0%
Ne 0.0056% Ne 0.0039%
Kr 0.00068% Kr 0.00047%
Xe 0.00018% Xe 0.00013%
@ 8.43333 psi
2.7 psi PP O2
CO2 not noticeable below 2% for several hours.
Spacesuit is the primary determinant of habitat pressure.
Shuttle oxygen pre-breathe time prior to EVA: 17 hours.
Mars 1 EVA per day, demands zero pre-breathe time.
Partial pressure N2 vs. suit total pressure: 1.2:1
Partial pressure O2 on Earth at sea level: 3.0 psi
Higher altitude cities have lower pressure but 21% O2, lower partial pressure is fine with acclimation.
2.7 psi habitat pressure is 90% of Earth sea level, reduces risk of fire, easily acclimated.
3.0 psi pure O2 suit reduces movement counterforce but leak of 10% pressure would reduce O2 to habitat level.
Compressor: 113 litres/minute (Mars air)
Assumed Mars atmosphere average: 7mbar, -38.15°C
Compression time: ¾ sol (18 hours, 29 min., 41.4 sec.)
CO2 1,882.9 g
mix gas 66.0675 g
Vessel volume: 5.880 l
Water ice accumulated per cycle: 0.24 g
N2 + 3 H2 → 2 NH3
O2 + 2 H2 → 2 H2O
First remove all CO2 with sorbent, any trace would combine with H2 to form H2O and CO.
NH3 + H2O → NH4OH
separate ammonia @ -77.7°C (freeze to solid)
Remaining: all noble gas
More energy efficient
Hollow fibres thinner than human hair, maintainable on Mars colony?
Membranes can be used with Sabatier, to separate non-combusted H2 from CH4.