CO2 Processing and O2 Reclamation: Recent Technology Developments for the First Closed Loop in ECLSS

The longer human beings in closed habitats need to be supplied with life support functions, the more the closure of the ECLSS loops becomes a must. This is certainly valid for habitats in space, where a steady resupply of consumables from Earth is impossible due to excessive distances or prohibitive high cost, but it may apply in general to earthbound habitats as well, if for instance large submarines want to extend their diving time.

In two harmonised programs for the two customers European and German Space Agency (ESA/ESTEC, DARA), Dornier is now in charge with the development of the technologies for the closure of the oxygen loop. This system, designed to eliminate the carbon dioxide (CO₂), produced by the metabolism of three persons, from the cabin atmosphere and to recover the oxygen (O₂) to return it to the cabin again, consists of three assemblies:

• Solid Amine Water steam Desorbed (SAWD) CO₂ concentrator
• Sabatier Methanation Reactor (SMR) to convert the CO₂ and additionally fed hydrogen (H₂) into methane (CH₄) and water (H₂O)
• Fixed Alkaline Electrolyser (FAE) to reclaim the oxygen from the SMR product water and to provide hydrogen for the SMR

All three assemblies have been developed and tested over the past years, the issue for the current program was to investigate their interaction. This paper reports on the following:

• combined operation of SAWD and SMR
• operation of the FAE with water produced by the SMR

Furthermore additional aspects which were investigated on these assemblies, are reported such as:

• improvement of the FAE with respect to its capability to run in a cyclical power on/off - mode
• comparison of the SMR developed under the ESTEC contract with a Russian SMR
• development of a low temperature methanation catalyst for the SMR