<i>In Situ</i> Methanation on Mars: A Process Concept Study on the Impact of H ₂ /CO ₂ and Recycle Ratio

Abstract For return missions from Mars, the supply of rocket fuel is crucial. As transportation of propellant from Earth and storage on Mars are costly and energy intensive, in situ resource utilization (ISRU) for methane production on Mars presents a promising solution. The major challenge is to identify a robust production process, which provides the required propellant purity. In this study, we compare two process concepts, with and without recycle, under realistic operating conditions using thermodynamic modeling and simulation. The H 2 /CO 2 feed ratio is crucial to achieve sufficiently high methane selectivity and thereby reduce the effort in product gas cleaning and the overall process complexity. At the same time, recycling unreacted reactants reduces resource consumption, which is preferable for ISRU scenarios. Hence, our study provides a basis for more detailed process design using kinetic information on the involved process steps.