Design and Testing of a Magnetohydrodynamic Oxygen Generation Cell for Microgravity Operation

As public and private enterprises prepare for crewed exploration missions to the Moon and Mars, life-support systems must consider reliability beyond current ISS standards. Prior work has shown that adapting the Oxygen Generation Assembly (OGA) architecture on the ISS for a Mars mission would not save mass over consumables. This is mostly due to the mass of spares required for failure-prone components in the phase-separating recirculation loop, many of which would require four or more replacements for even the shortest Mars transit of 375 days of round-trip travel. Instead of a proton exchange membrane and pumped recirculation loop, the Magnetohydrodynamic Oxygen Generation Assembly (MOGA) discussed here employs an alkaline architecture where extraction of gas products from the liquid electrolyte is performed in the electrochemical cell itself via vortical phase separation. Prior analysis indicates that this architecture could reduce the system mass by 33% and 10% compared to the OGA and in-development Advanced OGA, respectively, with 20% crew-time savings in both cases. In this work, the simulation and development of the first MOGA cell prototype are described, based on the optimal design output of a five-parameter genetic algorithm. Benchtop tests are conducted on the ground using a full-scale single-cell prototype with its rotation axis aligned with gravity, where angular velocities are recorded between 0.8-1.45 rad/s at current densities between 10-302 mA/cm2. Experimental angular velocities are within 18% of the model, whereas electrochemical performance is significantly worse due to gravity-induced gas-accumulation on the upper electrode. Demagnetization is significant for neodymium magnets at 60°C, indicating the need for a robust thermal control system. Goals for future work include parabolic flight testing as well as thermal modeling and validation in long-duration trials.