A consortium headed by the European Space Agency is exploring the possibility of building a lunar base by using 3D printing.
Top architects Foster + Partners have joined with ESA to test the feasibility of 3D printing using lunar soil, known as regolith, as building matter.
“Terrestrial 3D printing technology has produced entire structures,” said Laurent Pambaguian, heading the project for ESA. “Our industrial team investigated if it could similarly be employed to build a lunar habitat.”
Foster + Partners 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.
A hollow closed-cell structure – reminiscent of bird bones – provides a good combination of strength and weight. The base’s design was guided in turn by the properties of 3D-printed lunar soil, with a 1.5-tonne building block produced as a demonstration.
The base can house four people, protecting them from meteorites, gamma radiation and high temperature fluctuations. It is first unfolded from a tubular module that can be transported by space rocket. An inflatable dome then extends from one end of this cylinder to provide a support structure for construction.
Layers of regolith are then built up over the dome by a robot-operated 3D printer to create a protective shell. To ensure strength while keeping the amount of binding “ink” to a minimum, the shell is made up of a hollow closed cellular structure similar to foam.
The geometry of the structure was designed by Foster + Partners in collaboration with consortium partners, demonstrating the potential of 3D printing to create structures that are close to natural biological systems.
Simulated lunar soil has been used to create a 1.5 tonne mockup and 3D printing tests have been undertaken at a smaller scale in a vacuum chamber to echo lunar conditions.
The planned site for the base is at the Moon’s southern pole, where there is near perpetual sunlight on the horizon.
The consortium includes Italian space engineering firm Alta SpA, working with Pisa-based engineering university Scuola Superiore Sant’Anna.
Monolite UK supplied the D-Shape printer and developed a European source for lunar regolith stimulant, which has been used for printing all samples and demonstrators.
The printer includes a mobile printing array of nozzles on a six metre 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,” said 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 metres per hour, while our next-generation design should attain 3.5 metres per hour, completing an entire building in a week.”
“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 new possibilities this work opens up can then be considered by international space agencies as part of the current development of a common exploration strategy.”
“As a practice, we are used to designing for extreme climates on Earth and exploiting the environmental benefits of using local, sustainable materials,” said Xavier De Kestelier of Foster + Partners Specialist Modelling Group. “Our lunar habitation follows a similar logic.”
3D printing, otherwise known as additive layer manufacturing, is regarded as a very promising technology for the space industry. It involves the construction of a solid object from a series of layers – each one printed on top of the last.
The raw material is generally powder that is heated or chemically cemented into a solid. Alternatively, liquids or wires can be used as raw materials.
Additive layer manufacturing is a hugely versatile technique: anything that can be designed within computer-aided design (CAD) software can then be printed as a physical item, providing that the specific design limits of the process are respected.
This allows building items of a complexity far beyond what can be achieved using conventional machining technologies.
It is also extremely resource-efficient, offering mass savings of anything between 50 per cent and 95 per cent compared to traditional manufacturing, where surplus materials are cut away to form the desired component.
With additive layer manufacturing, only what is needed is used and the number of manufacturing steps are reduced as well.
ESA is investigating additive layer manufacturing as part of its Clean Space initiative, seeking to apply innovative technologies to reduce the environmental impacts of the space industry.