How easy is it to create oxygen from water on Mars?
Lead engineer of the project, Gunter Just, said: “We designed and built a small centrifuge that could generate a range of gravity levels relevant to the Moon and Mars, and operated it during microgravity on a parabolic flight, to remove the influence of Earth’s gravity.
“When doing an experiment in the lab, you cannot escape the gravity of Earth; in the almost zero-g background in the aircraft, however, our electrolysis cells were only influenced by the centrifugal force and so we could tune the gravity-level of each experiment by changing the rotation speed. The centrifuge had four 25 cm arms that each held an electrolysis cell equipped with a variety of sensors, so during each parabola of around 18 seconds we did four simultaneous experiments on the spinning system.
“We also operated the same experiments on the centrifuge between 1 and 8 g in the laboratory. In this configuration we had the arms swinging so that the downwards gravity was accounted for. It was found that the trend observed below 1 g was consistent with the trend above 1 g, which experimentally verified that high gravity platforms can be used to predict electrolysis behaviour in lunar gravity, removing the limitations of needing costly and complex microgravity conditions. In our system, we found that 11% less oxygen was produced in lunar gravity, if the same operating parameters were used as on Earth.”
The additional power requirement was more modest at around 1%. These specific values are only relevant to the small test cell but demonstrate that the reduced efficiency in low gravity environments must be taken into account when planning power budgets or product output for a system operating on the Moon or Mars. If the impact on power or product output was deemed too large for a system to function properly, some adaptations could be made that may reduce the effect of gravity, such as using a specially structured electrode surface or introducing flow or stirring.