A year ago, a USC research project on contour crafting let us fantasize about 3D printing bases on the surface of the moon--or sending robots out into space to build us some nice lunar lodgings before we make the trip ourselves. Apparently that project drew a lot of attention, or some other scientists caught the 3D printing bug and decided it's the way to go to establish long-term living quarters on the moon. Wired reports that the European Space Agency has taken up the cause, teaming up with Monolite UK to build a moon printer based on the D-Shape robotic printer, which can build house-size structures.
The D-Shape creates its own concrete by combining sand with a liquid binding solution, so you can see how the printer would be ideal for building a lunar base. Shipping building materials up on shuttle runs would be prohibitively expensive, so the ideal base would be constructed from the lunar surface. The ESA is also working with designers Foster+Partners, who "devised a weight-bearing ‘catenary’ dome design with a cellular structured wall to shield against micrometeoroids and space radiation, incorporating a pressurised inflatable to shelter astronauts."
We're still years away from loading up a 3D printing bot onto a shuttle and sending it to the moon, but what seemed like a far-out idea last year now seems to be somewhat plausible. The ESA's post about the project goes into a little detail about the 3D printing process being tested here on Earth.
“First, we needed to mix the simulated lunar material with magnesium oxide. This turns it into ‘paper’ we can print with,” explained Monolite founder Enrico Dini.
“Then for our structural ‘ink’ we apply a binding salt which converts material to a stone-like solid.
“Our current printer builds at a rate of around 2 m per hour, while our next-generation design should attain 3.5 m per hour, completing an entire building in a week.”
Printing a structure in a week sounds remarkably fast for a space project--after all, the ISS has been cobbled together piece-by-piece for more than a decade. 3D printing on the moon won't be quite as easy as it is on Earth, of course--one of the adaptations to the D-Shape had to overcome the challenge of printing without an atmosphere.
“The process is based on applying liquids but, of course, unprotected liquids boil away in vacuum,” said Giovanni Cesaretti of Alta.
Even if the building process seems doable, there are other obstacles to overcome, like creating a livable atmosphere on the moon.
“So we inserted the 3D printer nozzle beneath the regolith layer. We found small 2 mm-scale droplets stay trapped by capillary forces in the soil, meaning the printing process can indeed work in vacuum.”
Even if the building process seems doable, there are other obstacles to overcome, like creating a livable atmosphere on the moon, for a base to be truly viable. But it's an exciting start.
One other interesting tidbit about the project: Testing out the printing process required multiple tons of lunar material. Even though there are companies that specialize in creating synthetic lunar regolith (the dirt, dust, and broken rock bits that cover a rocky surface), it's expensive even in small batches. The ESA found that the basaltic rock from an Italian volcano bears a 99.8 percent resemblance to the material on the surface of the moon, making it perfect (and plentiful) for experimentation.