NASA has delayed their Artemis mission to the Moon, but that doesn’t mean a return to the Moon isn’t imminent. Space agencies around the world have their sights set on our rocky satellite. No matter who gets there, if they’re planning for a sustained presence on the Moon, they’ll require in-situ resources.
Oxygen and water are at the top of a list of resources that astronauts will need on the Moon. A team of engineers and scientists are figuring out how to cook Moon rocks and get vital oxygen and water from them. They presented their results at the Europlanet Science Congress 2021.
Professor Michèle Lavagna of Politecnico Milano led the experiments. A consortium of companies and agencies, including the ESA and the Italian Space Agency, is behind the work. Lavagna and others presented a laboratory demonstration of their work at EPSC2921.
When we talk about lunar soil, we mean lunar regolith, the layer of dust that coats the Moon. The same layer that confounded Apollo astronauts by finding its way into the lunar module, clogging mechanisms and interfering with instruments. The dust constitutes an ongoing hazard that space agencies are still trying to mitigate. But the same dust is also a critical resource.
An Apollo 17 astronaut digs in the lunar regolith to study the mechanical behaviour of moon dust. Credit: NASAThere’s lots of oxygen in the lunar regolith because oxygen readily reacts with other elements, especially group one elements. Lunar soil is rich in oxides, especially silicon dioxide, iron oxide, magnesium oxide, etc. According to the ESA, about 50% of lunar soil is iron and silicon dioxide, and about 26% of those compounds are oxygen. The trick is getting the oxygen out.
Lavagna demonstrated a two-step process that’s regularly used in industrial applications here on Earth. First, the simulated lunar regolith is vaporized in the presence of hydrogen and methane then washed with hydrogen gas. A furnace heats the minerals to 1,000 Celsius (1800 F), which turns them directly from a solid to a gas. By doing so, the minerals skip the liquid phase, making the entire process simpler.
Then the gases and the residual methane go to a catalytic converter and then a condenser which separates the water. After that, hydrolysis separates the oxygen, and the system recycles the hydrogen and methane by-products.
Engineers and scientists have been working on the challenge of extracting in-situ resources on the Moon for many years now. One method involves using molten salt electrolysis to extract oxygen. That method is adapted from mining, and it also produces useful metal alloys from lunar regolith.
But one of the critical features of this newer process, according to Lavagna, is it’s almost hands-off.
“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 Professor Lavagna.
This video shows water extracted by the process. Credit: Politecnico Milano, CC BY-NC-CDThe team is still working on optimizing the process in anticipation of an eventual fight test. They’re working with the furnace temperature, length and frequency of the washing, the ratio of the gas mixtures, and the size of soil batches. So far, they’ve learned that small batches of soil produce maximized yields when combined with the highest possible temperatures and long washing phases.
The system produces silica as a by-product. It also produces metals that require further processing before being used as in-situ resources.
‘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 a very good starting point.’
