Now research by the European Space Agency (ESA) has demonstrated how to produce oxygen from moon dirt (regolith), actually well-simulated moondust as only modest quantities of the real thing exist on Earth.
These samples returned from the lunar surface in past missions confirm that the lunar regolith comprises 40-45 per cent oxygen by weight, the single most abundant element.
However, this oxygen is bound up chemically as oxides in the form of minerals or glass and needs to be separated.
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A prototype oxygen plant has been set up in the Materials and Electrical Components Laboratory of the European Space Research and Technology Centre (ESTEC) in Noordwijk in the Netherlands.
“Having our own facility allows us to focus on oxygen production, measuring it with a mass spectrometer as it is extracted from the regolith simulant,” said Beth Lomax of the University of Glasgow.
Her doctoral work is being supported through ESA’s Networking and Partnering Initiative, harnessing advanced academic research for space applications.
“Being able to acquire oxygen from resources found on the moon would obviously be hugely useful for future lunar settlers, both for breathing and in the local production of rocket fuel,” she said.
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ESA research fellow Alexandre Meurisse said now that the prototype facility was in operation, it could be fine tuned, for example, by reducing the operating temperature.
He objective is to develop a version of this system which could one day operate.
ESTEC’s oxygen extraction system uses a method called molten salt electrolysis – placing regolith in a metal basket with molten calcium chloride salt to serve as an electrolyte and heating to 950 degrees.
At this temperature the regolith remains solid. But an electric current extracts oxygen, which migrates to an anode for collection. As a bonus this process also converts the regolith into useful metal alloys.
This molten salt electrolysis method was developed by UK company Metalysis for commercial metal production.
Lomax’s PhD work involved working at the company to study the process before recreating it at ESTEC.
“At Metalysis, oxygen produced by the process is an unwanted by-product and is instead released as carbon dioxide and carbon monoxide, which means the reactors are not designed to withstand oxygen gas itself,” she said.
“So we had to redesign the ESTEC version to be able to have the oxygen available to measure. The lab team was very helpful in getting it installed and operating safely.”
Tommaso Ghidini, head of ESA’s Structures, Mechanisms and Materials Division, said ESA and NASA were heading back to the moon with crewed missions, this time with a view to staying.
“Accordingly, we’re shifting our engineering approach to a systematic use of lunar resources in-situ,” he said.
“We are working with our colleagues in the Human and Robotics Exploration Directorate, European industry and academia to provide top-class scientific approaches and key enabling technologies like this one, towards a sustained human presence on the moon and maybe one day Mars.”
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