Researchers have made a 3D-printable building material by mixing urea and moon dust.
As NASA plans to return to the moon, scientists are looking for ways to protect and shelter astronauts.
The combined material is homogeneous in texture and can be piped into shape.
Was The Martian a documentary after all? In a new paper in the Journal of Cleaner Production, scientists looked at the ways space travelers might end up building structures on the moon, and one avenue they studied combines urea (from urine) with different materials to utilize urea’s unique chemical properties.
The researchers say this is a way to capitalize on what the moon already has, which is tons of rock, regolith (smaller rock particulate), and fine, silky lunar soil. By combining some distillate of urea from astronaut urine and the lunar silt, scientists have made a kind of geopolymer cement that can be piped using a 3D printer. In their experiments, they used a syringe to pipe the composite material in a similar way to a 3D printer.
Why urea? Well, once you decouple the ick factor, it’s a useful chemical. “Urea can break hydrogen bonds, and therefore reduces the viscosities of many aqueous mixtures. Since urea is the second most abundant component in urine (after water), it is readily available anywhere there are humans,” the researchers explain.
In the experiment, the scientists used powdered urea, which is available for purchase as a fertilizer, adhesive, and beauty additive. It’s also given to patients with very specific kidney problems and diseases. Humans naturally produce urea, of course, but it can also be derived from animals and plants.
Once blended with water, this liquid is combined with fine rock powder. We colloquially call all moon surface gravel regolith, but what this team used is technically more like lunar soil.
On Earth, we think of soil as something that’s often pretty damp and filled with organic material and microorganisms. Moon soil is simply rocks that have been ground down until they’re the consistency of dust—it’s just the pure mineral component, without the enlivening nutrients and living things that plants need.
This dry, lifeless dust is made almost exclusively by wind erosion. What results is more like plaster of Paris or Portland cement, ideal for mixing into a paste.
In their tests, the researchers found their piped urea mixture dried into a strong solid that they hope will be structural grade for things astronauts might need. They explain:
“Further studies are needed in order to assess how these lunar regolith geopolymers will behave under the severe lunar conditions, with a vacuum that can cause the volatile components to evaporate, and large temperature fluctuations which might cause crack formation.”
There are logistical and safety challenges, too. How could astronauts set up and shelter a 3D printing environment? Even if the material holds up to the extreme vacuum conditions on the moon’s surface, it’s not very useful if it can’t withstand meteor activity or shelter astronauts from powerful cosmic radiation. All of this is work for subsequent tests.