Engineers have successfully shown how water and oxygen can be extracted by
cooking up lunar soil, in order to support future Moon bases. A laboratory
demonstrator, developed by a consortium of the Politecnico Milano, the
European Space Agency, the Italian Space Agency and the OHB Group, is
presented this week at the Europlanet Science Congress (EPSC) 2021.
The set-up uses a two-step process, well known in industrial chemistry for
terrestrial applications, that has been customised to work with a mineral
mixture that mimics the lunar soil. Around 50% of lunar soil in all regions
of the Moon is made up of silicon or iron oxides, and these in turn are
around 26% oxygen. This means that a system that efficiently extracts oxygen
from the soil could operate at any landing site or installation on the Moon.
In the experimental set-up, the soil simulant is vaporised in the presence
of hydrogen and methane, then “washed” with hydrogen gas. Heated by a
furnace to temperatures of around 1000 degrees Celsius, the minerals turn
directly from a solid to a gas, missing out a molten phase, which reduces
the complexity of the technology needed. Gases produced and residual methane
are sent to a catalytic converter and a condenser that separates out water.
Oxygen can then be extracted through electrolysis. By-products of methane
and hydrogen are recycled in the system.
“Our experiments show that the rig is scalable and can operate in an almost
completely self-sustained closed loop, without the need for human
intervention and without getting clogged up,” said Prof Michèle Lavagna, of
the Politecnico Milano, who led the experiments.
To accurately understand the process and prepare the technology needed for a
flight test, experiments have been carried out to optimise the temperature
of the furnace, the length and frequency of the washing phases, the ratio of
the mixtures of gases, and the mass of the soil simulant batches. Results
show that yield is maximised by processing the soil simulant in small
batches, at the highest temperatures possible and using long washing phases.
The solid by-product is rich in silica and metals that can undergo further
processing for other resources useful for in-situ exploration of the Moon.
‘The capability of having efficient water and oxygen production facilities
on site is fundamental for human exploration and to run high quality science
directly on the Moon,’ said Lavagna. ‘These laboratory experiments have
deepened our understanding of each step in the process. It is not the end of
the story, but it’s very a good starting point.’
Reference:
Lavagna, M., Prinetto, J., Colagrossi, A., Troisi, I., Dottori, A., and
lunghi, P.: Water production from lunar regolith through carbothermal
reduction modelling through ground experiments, Europlanet Science Congress
2021, online, 13–24 Sep 2021, EPSC2021-527,
https://doi.org/10.5194/epsc2021-527
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