The European Space Agency (ESA) is exploring how to convert astronauts’ urine into a valuable building material that could lead to the construction of a stronger 3D-printed lunar base,media reported. Like NASA, ESA hopes to one day build buildings on the moon and even a gathering place for astronauts there.
Of course, one of the biggest challenges of this new one is raw materials. While several projects have been exploring 3D printing as a quick and flexible way to build structures, researchers hope to avoid hauling materials from Earth for the process, which would make it easier.
THE IDEA OF ESA IS TO USE A SO-CALLED LUNAR GEOPOLYMER MIXTURE — A CONCRETE-LIKE SUBSTANCE THAT CAN BE SQUEEZED OUT BY A 3D PRINTER AND THEN FORMED INTO SOLIDS FOR CONSTRUCTION. However, printing this material has an ingredient that is necessary, and that is some kind of plasticizer. The demand for water in the mixture is usually reduced by the choice of radon or polysacchamate.
Although the moon’s own soil — also known as the lunar weathering layer — can form the body of the printed material, traditional plasticizers need to be extracted from Earth. NASA estimates that the cost of putting a pound of material into orbit is about $10,000, which would be unrealistic for any useful lunar base.
In contrast, urea is the second-most abundant component in human urine — the first is water — and new ESA research suggests that urea is actually a good plasticizer. Urea not only breaks down hydrogen bonds to reduce fluid viscosity, but also the calcium minerals in urine can improve the curing process of lunar geopolymers.
“We hope that astronauts’ urine will be used at future lunar bases as it is now, with only minor adjustments to water content,” explained Marlies Arnhof, co-author of the study and a member of the ESA Senior Concept Group. “
It is understood that the average astronaut produces more than three pints of liquid waste per day. This makes it cheap and easy to obtain, and it is very useful in mixing. The samples were made from simulated lunar soil and subjected to a cycle of vacuum and freeze-thaw, similar to what moon concrete might face on the moon.
The ESA team found that samples using urea were able to withstand heavy weight shortly after mixing, with little effect on their shape. This is critical because 3D printing will effectively layer the structure from bottom to top.
But researchers still have a lot of work to do before they can do it, like further testing for more extreme conditions, which is currently under way. They will also study whether basalt fibers found on the moon could be used to strengthen the moon’s concrete to make it stronger and increase its shape and structure.