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The Closed-Loop Air REvitalisation System ARES is a regenerative life support system for closed habitats. With regenerative processes the ARES covers the life support functions: 1. Removal of carbon dioxide from the spacecraft atmosphere via a regenerative adsorption/desorption process, 2. Supply of breathable oxygen via electrolysis of water, 3. Catalytic conversion of carbon dioxide with hydrogen to water and methane. ARES will be accommodated in a double ISPR Rack which will contain all main and support functions like power and data handling and process water management. It is foreseen to be installed onboard the International Space Station (ISS) in the Columbus Module in 2013. After an initial technology demonstration phase ARES shall continue to operate thus enhancing the capabilities of the ISS Life Support System as acknowledged by NASA [5]. Due to its regenerative processes ARES will allow a significant reduction of water upload to the ISS.

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.

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.

An air revitalization system is being designed for the ISS. The name of this system is ARES, which stands for Atmosphere Regeneration System. Its major functions in the Life Support System of the ISS would be to: - Generate breathable oxygen from water - Collect the produced CO2 from air cabin and to control cabin CO2-level as required - Convert CO2 into water and methane - Recover the produced water for use in the water management system. ARES is based on ESA ECLS Technology Program developments. The prototype, so-called ARES Elegant Breadboard, has been manufactured and has just been tested at EADS. In parallel to the design and manufacture activities of the ARES Elegant Breadboard, an EcosimPro simulation model of the overall hardware system has been developed. The simulation model has been used intensively in the design process and it is going to be correlated according to test data.

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.

The on-board production of oxygen is demanded for future long-term missions such as International Space Station, Lunar base and missions to Mars. The needed oxygen can be recovered by electrolysing the water produced by the carbon dioxide processing system or other on-board water sources like water condensate. This way the oxygen loop will be closed. Since 1985 in a harmonised programme sponsored by the European Space Agency (ESA) and the German Space Agency (DARA), the required technology for an air revitalisation system (ARS) is being developed. The system is based on carbon dioxide concentration using solid amine water steam desorption, carbon dioxide hydrogenation (Sabatier) and fixed alkaline electrolysis. This paper reports on the manufacturing and testing of the fixed alkaline electrolyser (FAE) system designed for a 3-person capability and it discusses the current status of the ARS.

Environment Control and Life Support Systems (ECLSS) are necessary for missions of human beings into outer space. The longer the missions are the more the closure of the ECLSS loops is demanded. Since 1985 in a harmonised multi-phased programme under ESA (European Space Agency) and DARA comtract (German Space Agency) the Air Revitalisation System ( ARS )and its technologies are being developed. This paper reviews the current status of the complete system and presents the latest development results of the three key elements: The solid amine CO2 concentrator. The Sabatier reactor. The fixed alkaline electrolyser.

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.

In support of the Columbus ECLSS, a technology development program has been performed on four items: Regenerative CO2 removal Trace Gas Contamination Control Trace Gas Contamination Monitoring Low Noise Variable Speed Fan This paper describes the contents and results of the concluding Subsystem Level Tests and consecutive programme extensions which concentrated on: performance of the Contamination Monitoring Unit noise generation of the Variable Speed Fan lifetime tests of the CO2 removal solid amine closed water loop operation of a solid amine CO2 removal unit

This paper presents the design and the test results of a regenerative carbon dioxide control system, using solid ion exchange materials. The system applies a two bed approach with regeneration by steam and is designed far a 3 man operation. Two adsorber materials were investigated and applied throughout the tests. The system contains an evaporator, two adsorber beds, a condensing heat exchanger and an electronic controller. Test results concern the major performance parameters like CO2-loading, pressure loss, moisture range, stability ranges and energy required for dessorption. Furthermore, material dedicated analysis has been performed regarding offgassing products during operation.

The European Spacelab uses expendable means for CO2 -control. Early investigations of an extension of the mission time beyond the 7 day nominal mission showed a remarkable mass penalty for this approach, compared with regenerative CO2 -control. In view of long duration missions regenerative CO2 -nontrol is mandatory. Therefore a technology program has been setup, harmonized between ESA and DFVLR, screening possible methods, selecting one or two favoured ones and finally to build and test a breadboard. This paper shortly summarizes the selection process of the methods, describes the initial breadboard and presents first test results. The scope of this paper will address the selection of adsorber materials, methods for regeneration, design of evaporators, the test hardware and the test data acquisition. Preliminary conclusion from the previous work will be drawn and the planning of the further program will be given.