Scientists at The University of Manchester and The University of Glasgow have provided insight into the possibility of generating oxygen for humans so that they can stay on the Moon or Mars for extended periods of time.
Today, when space travel is more achievable than ever before, a reliable source of oxygen will greatly help humanity establish habitable settlements on other planets. Electrolysis is one potential method to achieve this. Here electricity is passed through a chemical system to start a reaction and can be used to extract oxygen out of lunar rocks or can be utilized to split water into hydrogen and oxygen. This can act to support life as well as for the production of rocket propellant.
However, since the Moon and Mars have low gravitational fields compared to Earth, it was not known how lower gravitational fields might affect the gas-evolving electrolysis. There are high chances that the bubbles from the electrolysis process might remain stuck on the electrode surfaces due to the low gravity and hence create a resistive layer. This can significantly impact the efficiency of electrolysis.
A new study shows how a team of researchers from The University of Manchester and the University of Glasgow undertook experiments to determine how the electrolysis process will be affected when done in reduced gravity situations.
Gunter Just, the lead engineer of the project said that they designed and built a small centrifuge that could generate gravity levels relevant to the Moon and Mars. To negate the influence of Earth’s gravity, they operated it during microgravity on a parabolic flight.
The Earth’s gravity cannot be escaped while working or testing in a lab, so the team tested the system during the microgravity on a parabolic flight. In the almost zero-g background in the aircraft, the electrolysis cells were influenced only by the centrifugal force and so the team fine-tuned the gravity level of each experiment by changing the rotation speed. The electrolysis centrifuge had four arms, each 25 cm long, that held an electrolytic cell equipped with multiple sensors of varying types. Gunter said that the team did four simultaneous experiments on the spinning system during each parabola of around 18 seconds.
He further said that the team also undertook the same experiments on the centrifuge, in the laboratory, ranging between 1 and 8 g. In the laboratory, the arms were left swinging so that the downwards gravity of the earth could be accounted for. They found that the trend observed below 1 g was consistent with the trend above 1 g.
This experimentally verified that the high gravity platforms can be used to predict the behaviour of the electrolysis in lunar gravity, which essentially removes the limitations of the need for costly and complex microgravity conditions. Using the same operating parameters, it was derived that 11 per cent less oxygen was produced in lunar gravity conditions when compared to the Earth gravity.
When compared to the Earth conditions, the additional power requirement was at around 1 per cent. This demonstrates that the reduced efficiency in low gravity environments needs to be taken into consideration when power budgets or product outputs are planned for a system operating that may operate on the Moon or Mars. Some adaptations will have to be made to reduce the effects of gravity, such as using a specially structured electrode surface or introducing flow or stirring.
Journal Reference: Bethany A. Lomax, Gunter H. Just, Patrick J. McHugh, Paul K. Broadley, Gregory C. Hutchings, Paul A. Burke, Matthew J. Roy, Katharine L. Smith, Mark D. Symes. Predicting the efficiency of oxygen-evolving electrolysis on the Moon and Mars. Nature Communications, 2022; 13 (1) DOI: 10.1038/s41467-022-28147-5
