Sponge iron process for manned space exploration
The Sponge Iron Process (SIR) is a well-known technology for the production and purification of hydrogen.
It consists of a cyclic process in which a feed gas, rich in carbon monoxide and hydrogen (e.g. syngas), is passed on an iron oxide (magnetite Fe3O4) at high temperature. Magnetite is reduced to wuestite (FeO) or iron while carbon monoxide and hydrogen are oxidised to carbon dioxide and water.
In a second step the reduced iron oxide/iron is re-oxidised with steam to form magnetite and hydrogen.
Impurities in the feed gas are removed during the process (the iron oxide acting as a trap for contaminants like hydrogen sulphide and hydrogen chloride); carbon monoxide level in the obtained hydrogen is very low (<10 ppm). The produced hydrogen has a high purity grade compliant with the requirements of fuel cell noble metal catalysts, which would be otherwise irreversibly poisoned. The process is therefore very interesting for production and purification of hydrogen for both high and low temperature fuel cells.
Since iron oxides are present in the regolith of both the Moon and Mars the process is promising in the frame of In Situ Utilisation Resources for space exploration.
Iron oxides, especially on the Moon might as well be used as a source of oxygen; the latter could be extracted from the oxide in the form of water via the SIR process. Water could then be decomposed into oxygen and hydrogen by electrolysis.
The study Assessed the feasibility of the process during exploration missions of the Moon and Mars taking into account the environmental conditions and gave an estimation of the efficiency and overall energy balance of the process.
 V. Hacker. A novel process for stationary hydrogen production: the reformer sponge iron cycle (RESC). Journal of Power Sources 118 (2003) 311-314.
 V. Hacker et al. Hydrogen Production by Steam-Iron Process. Journal of Power Sources 86 (2000) 531-535.