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3D Printers

Lunar Architecture Becomes Feasible with 3D Printing

27 Nov, 2012 By: Heather Livingston

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Space may be the next frontier for construction.

The idea of an exploratory base on the moon has long been a dream for space (and science fiction) enthusiasts such as myself. But the lunar surface is not a hospitable building site; it lacks the basic human necessities of an atmosphere, water, and food, and poses significant challenges unique to that environment. Prospective builders must determine how to transport materials, including water, a necessary part of standard construction processes, to the moon; how to build on site without heavy machinery; and how to protect the structure from the bombardment of solar radiation and staggering temperature extremes.

NASA has considered prefabricated construction for the lunar environment, but the complexity and cost of transporting such a heavy and cumbersome payload have ruled out that idea. Given these extraordinarily difficult circumstances, an equally extraordinary solution is required.

Two Approaches, One Goal

Two entities are striving to deliver a viable solution to the lunar construction challenge — and both require stationing large-scale 3D printers on the moon's surface. Enrico Dini, an Italian civil engineer by training and the inventor of the D-Shape 3D printer, is working with the European Space Agency (ESA) to explore the feasibility of using stereo­lithography to build structures from moon dust and an inorganic binder. D-Shape's building process lays down one ultrathin layer of material at a time to create its 3D structures.

In a segment on the Discovery Channel's Daily Planet, Enrico Dini describes his quest to create a 3D printer capable of producing large-scale building structures; see Cadalyst.com/moonbuild.

Here in the United States, Behrokh Khoshnevis, director of the Center for Rapid Automated Fabrication Technologies (CRAFT) at the University of Southern California Information Sciences Institute, is working closely with NASA to create concrete-based structures, also using moon dust, with his Contour Crafting machine. Contour Crafting's brand of 3D printing "is a hybrid system of extrusion and troweling that exudes paste material while smoothing out the outer surface," explains Khoshnevis.

Dini's moment of epiphany came the first time he saw a 3D printer, he reveals in a short film about D-Shape aired by the Discovery Channel. He subsequently gave up his career in robotics to pursue his passion to create the world's first 3D printer capable of fabricating a building. Dini has encountered many personal and financial bumps in the road — as often is the case with people of vision — but he has realized his dream. The D-Shape is now the world's largest 3D printer, measuring six meters square.

One Layer at a Time

The D-Shape process, based on CAD/CAM technology, begins with designing a structure as intricate as the imagination allows. The process is not limited by traditional construction challenges, such as the need for scaffolding or the skill of the tradespeople working on the building. The D-Shape machine begins construction with the foundation and continues to the top of the structure in one uninterrupted session. Thin layers of sand are laid while the printer nozzles apply a coating of a specially produced inorganic binder to solidify areas that will ultimately form the finished object, similar to how an inkjet printer applies ink to create an image on paper. Drying happens almost instantaneously as each layer is laid, 5–10 millimeters at a time. Upon completion of the layering process, unbound silica that remains in place around the printed object is brushed or scooped away to reveal a product that resembles marble, both in strength and appearance.

D-Shape could be the answer to constructing in the vacuum of space because once the building design has been prepared, no further human intervention is required. A robotic device could be directed to erect the printer in the appropriate location, remove the loose silica residue upon completion of the work, and relocate D-Shape to its next build site. Because there are no materials to be deployed other than the printer and the inorganic binder, the payload costs are minimal in comparison to prefab construction. (Presumably, the machine runs on solar power, but requests to Dini for verification were not answered.) Dini currently is working with the European Space Agency to test this process, using the D-Shape to construct objects in a vacuum at the Alta space facility in Pisa, Italy.

 

 

Extrusion Equals Rapid Construction

Unlike D-Shape's stereo­lithography process, which builds structures from thin layers, Khoshnevis's Contour Crafting machine produces thick layers of concrete slurry. In a paper titled "Mega-scale Fabrication by Contour Crafting" that appeared in the International Journal of Industrial and Systems Engineering, Khoshnevis and his co­authors explain, "Thicker material deposition cuts down fabrication time, which is essential for building large-scale objects. In CC, maximum height is limited by the side trowel height."

Behrokh Khoshnevis is director of the Center for Rapid Automated Fabrication Technologies (CRAFT) at USC and developer of the Contour Crafting machine. Image courtesy of CRAFT.

At an event in February 2012 organized by TEDxOjai, Khoshnevis spoke about the potential for using Contour Crafting to create emergency and low-cost shelter on Earth. Though he is excited about the possibilities of meeting real human needs with his Contour Crafting machine, Khoshnevis believes that its use in space has the better possibility of fruition in the near term. Interestingly, progress on Earth has been impeded by factors that don't affect construction on the moon, including building regulations, environmental threats such as seismic and wind forces, and lack of financial backing.

Khoshnevis notes that the largest structure they've completed thus far is a wall approximately 7' x 7', but Contour Crafting holds great promise, he says. Not only can it deliver intricately shaped structures in a very short amount of time, but it also can lay wiring and plumbing concurrently with the concrete — ultimately producing an average-sized home in one day, Khoshnevis says. That capability means the machine could create a fully operational lunar base before personnel arrive.

"We are now in Phase 2 of our project with NASA, and it involves using in situ material on the moon, Mars, and possibly asteroids to build the structures with only the sun power and the local material — without utilization of water or anything like that, so our process is based on extruding the molten material," says Khoshnevis.

"We are supposed to build the basic infrastructure elements, which [include the] landing pad and blast walls to protect the settlement from the projectiles created by the exhaust fumes from the landers," he adds. "We have to build the roads to take the landers to the settlements. We have to build hangars to protect landers from sunlight radiation, cosmic radiation, and micrometeorites, and we have to build shade walls. … These are [structures] that will be needed for any planetary exploitation — colonization — in the future."

 

 

First the Moon ...

Despite the efforts of Khoshnevis and Dini, the prospect of a lunar base is still uncertain. Many challenges remain, including questions about the moral and environmental implications of colonizing an extraterrestrial body.

One thing that's undisputed, however, is that 3D printing is changing our own world in leaps and bounds. The effect that the technology is having on manufacturing is no less dramatic than that created by Henry Ford's assembly line — and now that innovation is being tapped for architecture and construction. Khoshnevis hopes to have a commercially viable Contour Crafting product within two years.

Other companies are pursuing this market as well. On September 24, 2012, DUS Architects and Ultimaker announced the opening of the KamerMaker (RoomBuilder), a portable pavilion that produces 3D-printed rooms from a corn-based plastic.

Printed-on-demand architecture is one trend that will profoundly influence our built environment. Time will tell how this powerful technology, once limited to manufacturing applications, changes building design and construction as we know it.