Methane utilisation in life support systems

Due to high resupply costs, especially for space habitats beyond low earth orbit, future manned space missions will require environmental control and life support systems with a high degree of regenerativity. On the international space station ISS, the longest-duration space mission up to now, water recycling from urine was just recently established while all exhaled carbon dioxide is still vented over board. Possible ways to overcome this waste of resources and to save on resupply mass are examined in this thesis, mainly focusing on the utilisation of carbon dioxide. Various methods for its decomposition are pointed out, which would facilitate complete recycling of oxygen within the life support system. Ways to make use of the generated excess carbon for partial food synthesis or ion propulsion are presented as well. The ACLS air revitalisation system, which is currently being developed by EADS Astrium under contract with ESA, will be able to recover the oxygen from exhaled carbon dioxide, but the employed Sabatier process generates methane as a side product. If this methane was to be vented over board, hydrogen would be lost and had to be resupplied. Therefore, a pyrolysis device is proposed, cracking the methane into its constituents and recovering the hydrogen. Assuming the scenario of a space station in orbit around an atmosphere bearing planet, the excess carbon is used for ion propulsion allowing for station keeping. Plans to develop such a device and to prove its practicability on board the ISS round off this thesis.Validerat; 20101217 (root