Last week on Wired.co.uk we covered the Dutch architects who are planning on building the world's first 3D-printed house. It turns out that the European Space Agency (ESA) and architecture firm Foster + Partners have also been working on the same idea -- though they'll be building lunar colonies using 3D-printed bricks made out of moon dust.

Using an inflatable dome as a base, a giant 3D printer -- based on the same one developed by Enrico Dini that will be used by Universe Architecture to build the house in Amsterdam -- will build up a 1.5m wall over it that would protect a team of up to four astronauts from space radiation and meteorite impacts. It'll do this by building rock out of moon dust, and while the ESA has picked out a site at the Moon's south pole, the ultimate aim is to build bases on Mars.

Foster + Partners won a competition run by the ESA to conduct research into 3D printing in space, and the 1.5 tonne sample brick they've built is the culmination of their work (and the work of consortium partners the Scuola Superiore Sant'Anna and Alta) so far. Wired.co.uk spoke to Xavier de Kestelier, co-head of Foster + Partners' specialist modelling group, about building houses on the Moon.


He said: "[We looked] into previous research that has been done. They brought moon dust back in the 60s and 70s and there's been a lot of testing on that, so we know pretty well what moon dust is and how it behaves. So we're actually looking at the environment parameters -- gamma radiation, temperature fluctuations, meteorite impacts -- and we've made some good guesses as to what kind of protection you would need from printed material.

From that we were able to calculate the thickness for the dome structure. "The Moon doesn't protect us from radiation like the Earth does with its magnetic field and atmosphere, so it doesn't hit you straight away. During solar flares there's a much higher element of gamma radiation, so we actually start looking at a dome structure that can protect you from that, and the thickness that we need for that is 1.5m. Then there are other factors, for example meteorite impact. Meteorites can't burn up in the atmosphere of the Moon because there is none, which means they hit the Moon's surface at a speed of roughly 18km/s. Compare that to a bullet, which is roughly 2km/s. Don't think it rains meteorites there, but you have a high probability."

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The different stresses that came into play in the model, and the flexibility of the 3D printing process, gave de Kestelier and his team the chance to develop a unique "bubble" structure -- the Moon bricks that they settled on have periodic holes in them filled with soft regolith.

He explained: "You have the 'bubble', or the foam structure, with hard walls while inside. It's not empty, you'd have loose regolith inside. So if something hits it then it would hit a hard wall, soft material, hard material, soft material -- like a sandbag between concrete."


The dome will be around two storeys high, providing four astronauts with a large space within which to work. The buildings are inherently modular, as their architecture is directly influenced by the existing design of space stations orbiting Earth.

De Kestlier explained: "When we started this project we thought,

'let's look at the current architectural shapes and geometry of space stations'. We don't have any on the Moon, but we have the International Space Station, we have Mir, we have Skylab. They're always cylindrical elements connected to each other with certain geometries, and that's because it's the maximum space you can fit into a rocket. They're quite standardised. But internally these things aren't great spaces to live in, so we started looking at research done in the past on inflatables, because with an inflatable, it's much lighter. Every kilo you bring to the Moon is hugely expensive, so if you have more space with less material, the better. [With this] we only have to print small bits for the dome structure, but also for the living space itself, we have just a cylindrical element, and out of the cylindrical element we have a dome shape coming out."


Wired.co.uk also reported last month on Nasa's contract with Bigelow Industries to test an inflatable extension to the International Space Station. Inflatable modules appear to be a cheaper way of constructing habitable areas in space, while at the same time they have the benefit of being made of material that doesn't ionise when radiated, like metal. Their thinner skins can actually provide astronauts with greater protection from space radiation than thicker metal ones.

The site identified for the printed structure is at the Moon's south pole, on the edge of the Shackleton Crater -- a position that receives almost constant sunlight, and which is in direct line of sight of Earth for radio contact for most of each day. The eventual goal for the ESA, though, is to test this technology and get it ready for use in manned missions to Mars.

De Kestelier said: "As an architect, we are educated in thinking about materials all with a particular geometry. If I think steel, I think of an I-beam. It comes with a certain shape and geometry that is inherent to these materials. But when you start to 3D-print you have to think that geometry is now free. Look at nature -- nature doesn't have I-beams. I think for me that's hopefully where the future lies in 3D printing."