Experiments for a future Moon Base
ESA's technical heart has begun to produce oxygen out of simulated moondust. A prototype oxygen plant has been set up in the Materials and Electrical Components Laboratory at ESA/ESTEC (European Space Research and Technology Center), based in Noordwijk, The Netherlands. 1)
"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," Beth Lomax of the University of Glasgow, whose PhD 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."
ESA research fellow Alexandre Meurisse adds: "And now we have the facility in operation we can look into fine-tuning it, for instance by reducing the operating temperature, eventually designing a version of this system that could one day fly to the Moon to be operated there."
Samples returned from the lunar surface confirm that lunar regolith is made up of 40–45% percent oxygen by weight, its single most abundant element. But this oxygen is bound up chemically as oxides in the form of minerals or glass, so is unavailable for immediate use.
Figure 1: On the left side of this before and after image is a pile of simulated lunar soil, or regolith; on the right is the same pile after essentially all the oxygen has been extracted from it, leaving a mixture of metal alloys. Both the oxygen and metal could be used in the future by settlers on the Moon (image credit: Beth Lomax, University of Glasgow)
ESTEC's oxygen extraction is taking place using a method called molten salt electrolysis, involving placing regolith in a metal basket with molten calcium chloride salt to serve as an electrolyte, heated to 950°C. At this temperature the regolith remains solid.
But passing a current through it causes the oxygen to be extracted from the regolith and migrate across the salt to be collected at an anode. As a bonus this process also converts the regolith into usable metal alloys.
In fact this molten salt electrolysis method was developed by the UK company Metalysis for commercial metal and alloy production. Beth's PhD involved working at the company to study the process before recreating it at ESTEC.
Figure 2: ESA research fellow Alexandre Meurisse and Beth Lomax of the University of Glasgow producing oxygen and metal out of simulated moondust inside ESA's Materials and Electrical Components Laboratory (image credit: ESA, A. Conigili)
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," explains Beth. "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."
The oxygen plant runs silently, with the oxygen produced in the process is vented into an exhaust pipe for now, but will be stored after future upgrades of the system.
"The production process leaves behind a tangle of different metals," adds Alexandre, "and this is another useful line of research, to see what are the most useful alloys that could be produced from them, and what kind of applications could they be put to.
Figure 3: Scanning electron microscope view of lunar simulant particles before the oxygen extraction process (image credit: Beth Lomax, University of Glasgow)
"Could they be 3D printed directly, for example, or would they require refining? The precise combination of metals will depend on where on the Moon the regolith is acquired from – there would be significant regional differences."
The ultimate aim would be to design a ‘pilot plant' that could operate sustainably on the Moon, with the first technology demonstration targeted for the mid-2020s.
Figure 4: Moondust simulant undergoing oxygen extraction (image credit: Beth Lomax, University of Glasgow)
"ESA and NASA are heading back to the Moon with crewed missions, this time with a view towards staying," says Tommaso Ghidini, Head of ESA's Structures, Mechanisms and Materials Division.
"Accordingly we're shifting our engineering approach to a systematic use of lunar resources in-situ. 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."
Figure 5: Analysing results. ESA research fellow Alexandre Meurisse and Beth Lomax of the University of Glasgow producing oxygen and metal out of simulated moondust inside ESA's Materials and Electrical Components Laboratory (image credit: ESA, A. Conigili)
Human exploration and habitation of the Moon and other nearby planetary bodies are goals that have long fascinated scientific and public imagination. Sourcing resources locally will likely be essential for sustainable, long-duration activities in space . For extended future missions to the lunar surface (and beyond), oxygen will undoubtedly be one of the most valuable resources. 2)
Figure 6: Artist impression of activities in a Moon Base. Power generation from solar cells, food production in greenhouses and construction using mobile 3D printer-rovers (image credit: ESA, P. Carril) 3)
1) "ESA opens oxygen plant – making air out of moondust," ESA / Enabling & Support / Space Engineering & Technology, 17 January 2020, URL: http://www.esa.int/Enabling_Support/Space_Engineering_Technology
2) Bethany A. Lomax, Melchiorre Conti, Nader Khan,Nick S. Bennett, Alexey Y. Ganin, Mark D. Symes, "Proving the viability of an electrochemical process for the simultaneous extraction of oxygen and production of metal alloys from lunar regolith," Planetary and Space Science, Volume 180, January 2020, 104748, https://doi.org/10.1016/j.pss.2019.104748
3) "Artist impression of activities in a Moon Base," ESA Enabling & Support, 4 July 2019, URL: http://www.esa.int/Enabling_Support/Space_Engineering_Technology
The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (firstname.lastname@example.org).