Atmospheric processing
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Atmospheric processing describes the extraction of substances out of the Martian atmosphere and the usage as raw material for further processing. Unlike surface and sub-surface mining, the atmospheric mining does not require the movement of large amounts of regolith or rock with heavy machinery, nor is expensive transport per rover or railroad necessary. The atmosphere can simply be sucked in through a pipe at every location, and the processing is done inside of buildings. Also, the maintenance of all the mining machinery is in-house, which is a major safety advantage.
Contents
Collection of Atmosphere
A fan collects martian atmosphere and passes it through filters to separate out the dust. Then a compressor increases the pressure of the clean gases to the liquefaction point of CO2. The liquid CO2 is removed, then the rest of the gas is cooled further, to condense out the other atmospheric gases.
Process
Compression
Compression above 5,19 bar (520 kPa) allows the liquefaction of carbon dioxide. The liquid carbon dioxide can be separated by gravity from other gasses. The initial martian atmospheric pressure is approximately 600 Pa, so the compression ratio from 600 to 520 000 Pa is about 860 times. The compression may be carried out in two or more stages.
Condensation
The atmosphere is cooled to remove water vapor as a condensate. Then the dry gas is cooled further to condense the carbon dioxide that can be removed by gravity. The other gases are removed by condensing the gases in further cooling stages. All of the cooled gas may be used for process purposes, or some of the CO2, or other gases, may be released back into the atmosphere. The expansion of the gas back to atmospheric pressure produces cooling that can be used to condensate out the atmospheric gases.
Results
Dust
The Martian atmosphere contains variable amounts of dust, which consists of similar minerals like regolith. Electrostatic filters or other technologies will be used to remove the dust to prevent it from damaging the equipment.
Water
The 0.03 % water vapor (H2O) is equivalent to about 10 % air humidity after adiabatic compression and cooling to around 1°C. A device similar to an air dehumidifier can be used to extract this water.
Carbon Dioxide
Carbon dioxide is the main part of the Martian atmosphere with 96 %. It can be used for the hydrocarbon synthesis, including the production of methane based fuel.
Nitrogen
The balance of the remaining gas after carbon dioxide condensation contains mostly nitrogen and argon. This mixture can serve as a buffer for oxygen to produce a breathable atmosphere. remaining traces of Carbon monoxide must be catalytically removed if the gas is to be used for the settlement atmosphere.
Nitrogen can be used to create ammonia and nitrates in fertilizer and as nitric acid in industry.
Argon
Argon is useful for industrial processes that must be performed in an inert atmosphere. It can also be used for electric rocket propulsion. It may be used as a complement for nitrogen in a martian settlement if it proves to be safe for that purpose.
