The European Space Agency (ESA) has selected an industrial team, led by Thales Alenia Space in the UK, to design and build the first experimental payload to extract oxygen from the surface of the Moon.
The consortium – which includes AVS, Metalysis, the Open University and Redwire Space Europe, several of which also have UK bases – is tasked with producing a small piece of equipment that will evaluate the prospect of building larger lunar plants to extract propellant for spacecraft, breathable air for astronauts, and metallic raw materials for manufacturing.
Once thought of as a barren rock, the Moon is increasingly seen as a bountiful source of useful materials. Its fine soil, containing larger rocky fragments, includes metals such as iron, aluminium and titanium. Known as regolith, the surface material also contains significant amounts of oxygen, as well as frozen water at the poles, which could be put through electrolysis to provide hydrogen and oxygen for rocket propellant.
The team’s device will need to extract 50-100 grams of oxygen from regolith while delivering precision measurements of performance and gas concentrations. ESA aims to remove 70% of available oxygen from the sample.
Extraction will be a race against time. The solar-powered technology will only be available during a 10-day period within a single fortnight-long lunar day, before the arrival of the pitch black, freezing lunar night.
“The payload needs to be compact, low-power and able to fly on a range of potential lunar landers, including ESA’s own European Large Logistics Lander, EL3,” said David Binns, systems engineer at ESA’s Concurrent Design Facility.
“Being able to extract oxygen from moon rock, along with useable metals, will be a game changer for lunar exploration, allowing the international explorers set to return to the Moon to ‘live off the land’.”
The underlying concept has already been proven. Samples returned from the lunar surface confirm that regolith is made up of 40-45% oxygen by weight, its single most abundant element. Oxygen is bound up chemically as oxides however, in the form of minerals or glass, so is unavailable for immediate use.
A prototype oxygen plant at the European Space Research and Technology Centre (Estec) has shown a promising extraction method. The plant uses an electrolysis-based process to separate simulated regolith into metals and oxygen.
The molten salt electrolysis involves placing regolith in a metal basket with molten calcium chloride salt, which serves as an electrolyte, and heating it to 950°C. At that temperature the regolith remains solid, but passing a current through it causes the oxygen to be extracted from the regolith and to migrate across the salt, to be collected at the anode. The process also converts regolith into useable metal alloys.
The technique is based on a process developed at Metalysis. On Earth, the company takes metal oxide and treats it to produce metal powders. On the Moon, the metal could be used for construction, while oxygen might be used as propellant or life support.
“How can we extract the most amount of oxygen, with the lowest amount of consumed power? From a payload perspective, it needs to be as light as possible and low-footprint as possible,” said Metalysis managing director Ian Mellor, speaking to Professional Engineering previously.
Giorgio Magistrati, studies and technologies team leader at ESA's Expert (Exploration Preparation, Research and Technology) initiative said: “The time is right to begin work on realising this In-Situ Resource Utilisation demonstrator, the first step in our larger ISRU implementation strategy. Once the technology is proven using this initial payload, our approach will culminate in a full-scale ISRU plant in place on the Moon in the early part of the following decade.”
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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.