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During the last years extensive work has been done to design and develop the Closed-Loop Air Revitalization System ARES. The potential of ARES e.g. as part of the ISS ECLSS is to significantly reduce the water upload demand and to increase the safety of the crew by reducing dependence on re-supply flights. The design is adapted to the interfaces of the new base lined Russian MLM module as possible location for a future installation of ARES. Due to the lack of orbital support equipment and interfaces to a waste water bus, to a feed water supply line and due to the availability of only one single vent line it was necessary to make the ARES process water loop as independent as possible from the host vehicle. Another optimization effort was to match the CO2 desorption profile with the available hydrogen flow to achieve a sufficient water recovery performance, while meeting all related safety requirements, minimizing complexity and improving reliability.

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.

The development of the air revitalisation system ( AR) for a crewed spacecraft was initiated in 1985. The selected technical approach is a three-step process consisting of (1) a solid amine water steam desorption system to concentrate (the mainly) metabolically produced carbon dioxide(CO2) from the air (2) a Sabatier reactor to reduce the CO2 to water and methane (CH4) and (3) a fixed alkaline electrolyser to reclaim from the water the oxygen O2 for the crew. During 1996 / 1997 the AR system was successfully demonstrated on a laboratory scale configuration for a crew of three persons equivalent. During 1998 / 2000 the AR system was transformed into a rack-mounted so-called Air Revitalisation System Technology Demonstrator (ARSD) for ‘closed loop’ testing in a dedicated Closed Chamber, to demonstrate the readiness of the technology for a possible incorporation in the ISS enhancement programme.

Since 1985 in a step by step approach an advanced air revitalisation system has been developed for a crewed spacecraft. The metabolically produced carbon dioxide is concentrated through a solid amine water steam desorp-tion system and reduced to water and methane in a so-called Sabatier reactor. The water is currently fed into a fixed alkaline electrolyser to reclaim the oxygen for the crew. However, also water from other sources may be used. The hydrogen is recycled into the Sabatier reactor. The present system handles methane as a waste product closing so far the oxygen loop only. The system has been already successfully demonstrated in a laboratory scale configuration for a crew of three persons in 1996/1997. This paper discusses the results of the current development phase in which the system is reconfigured to fit into an International Space Station payload rack (ISPR). For this purpose the complete system design has been reviewed and upgraded where necessary.

1 The Closed-Loop Air REvitalisation System ARES is a proof of technology Payload. The objective of ARES is to demonstrate with regenerative processes: the provision of the capability for carbon dioxide removal from the module atmosphere, the return supply of breathable oxygen within a closed-loop process, the conversion of the hydrogen, resulting from the oxygen generation via electrolysis, to water. The ARES Payload is foreseen to be installed - in 2012 - onboard the ISS in the Columbus Module. The operation of ARES - in a representative manned microgravity environment - will produce valuable operational data on a system which is based on technologies which are different from other air revitalization systems presently in use. The ARES Technology Demonstrator Payload development started in 2003 with a Phase B, see references [1], [2], [3] and [4]. ARES is presently in Phase C1 and a PDR is scheduled for the beginning of 2009.