The oxygen production is accomplished through a process known generically as in situ resource utilization (ISRU). Since the Mars Oxygen ISRU Experiment (MOXIE) Project demonstrated operation of a prototype electrolysis system for converting Martian CO₂ to O₂ on Mars with great success, it is now appropriate to investigate scaling up this prototype to a full-scale system.

In a research paper recently published in Space: Science & Technology, Donald Rapp and Eric Hinterman modeled the performance of a full-scale Mars in situ resource utilization (ISRU) system to produce 30 metric tons of liquid O₂, operated for 14 months as the Mars environment changes diurnally and seasonally.

First, the authors introduce the ISRU system layout, requirements, and settings. The simplified layout of the ISRU system is shown in Fig. 1. The heart of the system is the stack (or, more likely, a set of stacks) of electrolysis cells, producing a flow of O₂ out of the anode and a mixture of CO, CO₂, and inert gases in the cathode exhaust. While the process operates, a compressor first pulls Mars atmosphere into the system and compresses it from Mars pressure to stack pressure.

A heat exchanger recuperates some heat from the exhaust gases to incoming gas from Mars, and this gas is preheated to stack temperature before entering the stack. After the electrolysis in the stack, the effluent from the stack is fed back to the heat exchanger to prewarm incoming Mars gas, and the cathode exhaust is vented, while the anode exhaust is fed to the liquefier.