Lunar Base Architecture Erected by 3D Printing
The idea to use a 3D printer for building lunar base structures from local materials is not just hypothetical anymore, but is now in the process of being experimentally tested by an ESA project. The tools and possible architecture were explored and tested on moon-like material with industrial partners including renowned architects Foster + Partners to test the feasibility of 3D printing using lunar soil.
Foster + Partners devised a weight-bearing dome design with a cellular structured wall to shield against micrometeoroids and space radiation, incorporating a pressurised inflatable to shelter astronauts. The base's design was guided by the properties of 3D-printed lunar soil, with a 1.5 tonne building block produced as a demonstration.
"3D printing offers a potential means of facilitating lunar settlement with reduced logistics from Earth," said Scott Hovland of ESA's human spaceflight team.
The UK's Monolite supplied the D-Shape printer, with a mobile printing array of nozzles on a 6 m frame to spray a binding solution onto a sand-like building material. 3D 'printouts' are built up layer by layer - the company more typically uses its printer to create sculptures and is working on artificial coral reefs to help preserve beaches from energetic sea waves. "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."
One of the most obvious differences to Earth, and also most problematic, is the vacuum and extreme temperatures in space. It was the task of Italian space research firm Alta SpA , teaming up with Pisa-based engineering university Scuola Superiore Sant'Anna, to adapt 3D printing techniques, also known as additive manufacturing, to a Moon mission
"The process is based on applying liquids but, of course, unprotected liquids boil away in vacuum," said Giovanni Cesaretti of Alta. "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."
They also made their own simulated lunar regolith, since the material can be quite expensive when bought, and the team required many tonnes for their work. "As another useful outcome, we discovered a European source of simulated lunar regolith," added Enrico. "Basaltic rock from one volcano in central Italy turns out to bear a 99.8% resemblance to lunar soil."
The project demonstrated a first example, and will continue to work on difficult issues to implement this on Moon, namely the extreme range of temperatures which the structures and the construction process needs to cope with, or controlling lunar dust.