ISRU atmosphere harvesting Robert Dyck

Mars Atmosphere CO % N 2 2.7% Ar1.6% O % CO0.07% H 2 O0.03% Ne % Kr % Xe % O %

CO 2 freezer filter dust/fines compress air to 10 bar freeze to 170°K ( °C) Vapour pressure: CO 2 = 0.1 bar H 2 O = 3.4x mbar As pressure drops, compressing more air to maintain 10 bar Continue until pressure doesn’t drop any more Gas will be primarily N 2 & Ar, ideal for diluent gas in habitat.

Carbon Monoxide After freeze: CO = 0.045%, O 2 = 0.096% CO: 0.001% symptoms of poisoning, 0.5% fatal O CO → 2 CO 2 with catalyst 2 O 3 → 3 O 2 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 CO 2 tank.

Mix gas Resulting gas, by volume:Breathing gas: CO %CO % N %N % Ar36.1%Ar25.1% O 2 2.1%O % Ne0.0056%Ne0.0039% Kr %Kr % psi 2.7 psi PP O 2 CO 2 not noticeable below 2% for several hours.

Spacesuit & habitat pressure 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 N 2 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 O 2 suit reduces movement counterforce but leak of 10% pressure would reduce O 2 to habitat level.

Equipment size Compressor: 113 litres/minute (Mars air) Assumed Mars atmosphere average: 7mbar, °C Compression time: ¾ sol (18 hours, 29 min., 41.4 sec.) Gas collected: CO 2 1,882.9 g mix gas g Vessel volume: l Water ice accumulated per cycle: 0.24 g

Ammonia & Argon N H 2 → 2 NH 3 O H 2 → 2 H 2 O First remove all CO 2 with sorbent, any trace would combine with H 2 to form H 2 O and CO. NH 3 + H 2 O → NH 4 OH separate -77.7°C (freeze to solid) Remaining: all noble gas Ar99.98% Ne0.0156% Kr % Xe %

Uses of ammonia Nitrogen fertilizer for greenhouse Mars regolith has no nitrogen compounds Refrigerant, especially absorption cycle

Membranes More energy efficient Hollow fibres thinner than human hair, maintainable on Mars colony? Membranes can be used with Sabatier, to separate non-combusted H 2 from CH 4.