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The current ECLS baseline of the International Space Station ISS contains an open oxygen loop. Breathable oxygen, generated by electrolysis of water, is supplied to all habitable modules. The crew of max. 7 astronauts converts the oxygen into metabolic carbon dioxide, which needs to be removed from the ISS atmosphere. Adsorption of CO2 is achieved through molecular sieves, desorption of CO2 is conducted by evacuation into space. This open process needs approx. 1500 kg of water upload mass annually. More than 75 % of this upload mass can be saved, if the open oxygen loop will be closed. This paper outlines the closed loop air revitalization system of Astrium, ARES, which has been successfully tested in closed chamber tests. It demonstrates in detail the technical application of ARES on ISS and outlines the commercial benefits. The second part of the paper describes ARES for a Mars habitat with a closed oxygen and hydrogen loop.

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.

During the last years extensive work has been done to design and develop the Closed Loop Air Revitalization System ARES. The potential of ARES for future space exploration missions is to significantly reduce the water upload demand, increase the safety of the crew by reducing dependency on re-supply flights and, due to the launch mass restraints, make future exploration missions to other planets possible. The ARES demonstrator includes the functions of CO2 concentration, CO2 reduction and oxygen generation. Whereas in previous phases ARES was designed to operate in NODE3 of the ISS, this has been changed to an intended ARES operation in the Russian Multifunctional Laboratory Module MLM. This year’s activities concentrated on process optimization of the Carbon Dioxide Removal Assembly (CCA) interaction with the Sabatier Reactor (CRA), extreme conditions testing, life time tests with the Sabatier Reactor and the oxygen generation stack and system testing.

At the 2002 ICES, FAVORITE, the orbital flight experiment for a fixed alkaline electrolyte (FAE) electrolyser stack was presented. The planning at that time was to fly the experiment in September 2003 on board the Space-Hab mission STS-118 with the space shuttle COLUMBIA flight ISS-13A.1. Due to the tragic accident of COLUMBIA on Feb. 1st, 2003, these plans became obsolete and alternative launch opportunities were looked for. They were finally found with the unmanned Russian FOTON-M2, which is built by TsSKB-PROGRESS in Samara, Russia and scheduled for launch from the Baikonur cosmodrome in April 2005. Because of the switch from a manned to an unmanned mission and other operational constraints, FAVORITE had to be redesigned in several parts. This paper summarizes the objectives of the flight experiment and describes the required design changes. It also presents an overview of the actual development status as well as of the work ahead.

FAVORITE (Fixed Alkaline Electrolyte Electrolyser Water Vapor Oxygen Reclamation In-flight Technology Demonstration Experiment) is an orbital flight experiment for a fixed alkaline electrolyte (FAE) electrolyser stack dedicated to generate oxygen and hydrogen out of water for life support and other applications. It was originally planned to fly in September 2003 on board the SpaceHab mission STS -118 with the space shuttle COLUMBIA flight ISS-13A.1, but after the tragic accident of COLUMBIA it was adapted to be launched with the unmanned Russian FOTON-M2 in May 2005. FAVORITE was therefore redesigned, manufactured and ground tested in 2004. This paper summarizes the pre-flight ground test results, reports on the lessons-learnt and gives an overview of the intended in-orbit and post-mission test program.