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Building on the moon is a challenge we have yet to fully grasp. Plenty of projects have grandiose plans, from using blood, sweat and tears to create bricks out of regolith to building towers to wirelessly transmit power between isolated locations. However, these projects all but ignore one of the most important types of material we use commonly here on Earth—ceramics.

A on a preprint server from Dr. Alex Ellery, an Engineering professor at Carleton University in Ottawa, discusses why ceramics are so critical to the development of the lunar economy, and points to further developments in materials science that must be completed in order to manufacture and utilize them on the surface of the moon.

Lunar in-situ resource utilization efforts have two primary focuses—utilizing water ice tucked away in the permanently shadowed regions, particularly of the moon's south pole, and utilizing basic regolith as construction feedstock for infrastructure needs like shelter or landing pads. Other resource recovery efforts look at how regolith or other structures could be mined as part of the lunar economy, with a particular focus on shipping those resources back into space as part of an effort to build solar power satellites or giant space habitats.

While water has its own useful characteristics, and will be absolutely critical to any future human settlement of the moon, regular regolith has limited functionality based on its material properties. While good for a basic construction material, it is lacking in some important physical properties, such as thermal and electrical resistivity, or the ability to be used as an adhesive (i.e. mortar).

That is where ceramics come in—many of them are manufacturable using materials made on the moon itself. For example, "weathering" anorthite, one of the most common materials in the regolith of the moon, with hydrochloric acid creates alumina and silica, two ceramics that are widely used on Earth in applications that require better material properties than the regular lunar regolith can provide.

In addition, Dr. Ellery describes a process that produces these ceramics using lunar highland simulant, with a side product of calcium chloride, a necessary component for the molten salt electrolysis reaction required to produce pure aluminum, one of the more widely sought-after building metals on the moon.

Once the ceramics are produced, shaping them into a useful configuration is the next step. Dr. Ellery looks at two different processes to do so—traditional sintering and 3D printing. Sintering, whereby the ceramic is heated to a high temperature to bond the particles of the powdered ceramic together, is probably the most commonly cited method.

On the moon, there is the added bonus of potentially using only concentrated solar energy to power the process. However, it has problems with brittleness and cracking, making many components created using this technique unusable in their intended applications. Adding iron to the mix, which can be found scattered throughout the lunar surface, can potentially improve matter, but this requires an additional processing step and different materials.

3D printing, on the other hand, faces its own challenges. While useful on Earth to create a variety of shapes and configurations, most 3D printing techniques require a binding agent that is composed of polymers. Since polymers are made of carbon, and carbon is relatively scarce on the moon, this "problem of polymers," as Dr. Ellery calls it, is a potential show-stopper for 3D printing ceramics on the moon.

He suggests several work-arounds, such as creating geopolymers out of clays that could be created from lunar materials, or using silicone-based polymers that don't use as much carbon. But, in the end, collecting and utilizing carbon to assist in the creation of ceramic-based objects is a critical path that requires much more research.

Ultimately, that call to action seems to be one of the primary goals of the paper. Dr. Ellery points out the general lack of understanding, from a technical and resource allocation standpoint, the process by which we will eventually create these critical materials exclusively from lunar sources of feedstock and power. Until we're able to do so, he claims, there will never be a fully fledged lunar economy. Even if there's only a slight possibility that he's right, that problem seems worth spending more time trying to solve.