Local materials—on Earth—can mean anything from thatched grass to reclaimed wood. On the moon, it means one thing only: the rocky sand that covers the barren, oxygen-less planet. Lunar soil might not lend itself to conventional construction techniques, but the finely grained stuff is perfect for 3-D printing. Now, the inventor of the large-format 3-D printer D-Shape, Enrico Dini, has teamed up with the European Space Agency and Foster + Partners to test whether the first lunar habitats could be printed using the sand.
"3-D printing offers a potential means of facilitating lunar settlement with reduced logistics from Earth," said the ESA’s Scott Hovland. As many an aerospace engineer will tell you, one of the biggest hurdles facing space colonization is the sheer expense of catapulting thousands of pounds of building materials out of orbit. That’s why so many proposals for space habitats are inflatable—the lighter the cargo load, the more feasible a plan becomes. The ESA’s plan would dramatically reduce the amount of materials being shuttled to and from the moon.
To test the idea, Dini created a simulation of lunar soil with magnesium oxide, which together form the "paper" base material. Using a structural salt "ink," he was able to bind the base material into a stone-like solid. "Our current printer builds at a rate of around two meters per hour," Dini says. "Our next-generation design should attain 3.5 meters per hour, completing an entire building in a week."
But it’s not just the weight of the printer that will have to be reconciled. It’s the printer’s systems themselves. For example, how will the ink nozzle function in the vacuum of the moon? The D-Shape works like most printers, by applying liquids to a solid base. But in a vacuum, liquids boil away. "So we inserted the 3-D printer nozzle beneath the [simulated soil]," explains Giovanni Cesaretti, head of the Italian space research agency Alta. They found that the "ink" stays put, thanks to the capillary forces in the soil. "[Which] means the printing process can indeed work in vacuum."
One of the most fascinating discoveries of the program was an accident. Simulation lunar soil tends to be pretty expensive, and is sold by the kilogram. Since Dini’s team needed tons of the stuff to print a scale model, they ended up searching for an alternative and finding one in Italian volcanic rock. "Basaltic rock from one volcano in central Italy turns out to bear a 99.8% resemblance to lunar soil," Dini says.
With the confirmation that the D-Shape can print lunar soil and function in a vacuum, the ESA plans to step up their research on other aspects of the idea. For example, the moon’s extreme temperatures could pose a threat to the D-Shape; it’s also a health hazard to breathe in lunar dust, so whoever’s manning the construction crew will need to be well-protected.
Check out the rest of their report here.