Printed in Space
If your star tracker breaks on the way to the moon, just hit Command P.
- By Mark Betancourt
- Air & Space magazine, November 2012
Center for Rapid Automated Fabrication Technologies (Craft) at University of Southern California
At a recent conference on the future of aerospace, 27-year-old entrepreneur Jason Dunn outlined his philosophy of why, after more than 50 years of space exploration, humans are not yet living in space colonies. “Everything manmade that’s ever been in space had to be built and launched from the ground,” he says. “And that puts enormous constraints on what you can actually do in space, because everything has to survive launch. So how do you get around that?”
His suggestion: Don’t manufacture things on the ground.
Dunn’s Silicon Valley startup company, Made In Space Inc., would reinvent the space industry by putting into orbit a cheap, easy mode of manufacturing: the 3D printer. It doesn’t print in the normal sense. But like an ordinary desktop printer, it receives instructions from a computer (in this case a computer-aided design, or CAD, file). Instead of arranging patterns of ink on a 2D sheet of paper, the 3D printer builds a solid object. Whereas traditional manufacturing techniques start with a solid block and cut unwanted material away from it, 3D printing—also called additive manufacturing—builds up material in layers, producing precisely the object desired with almost no waste.
3D printing is a growing industry on Earth, and has the potential to change not just the cost and speed of manufacturing but also the design of everything from airplanes to buildings. It could, in theory, have an even bigger impact on the space industry. For example, a Mars robot probe “printed” from a CAD file in orbit could be made 30 percent lighter than one that has to withstand the stress of a rocket launch from Earth. Human interplanetary missions that don’t have to bring along spare parts—because they can be made en route—will have more room for necessities like food, water, and oxygen. Not only could 3D printing make human space exploration easier, it could make certain kinds of exploration possible.
Today, only a handful of people are working to adapt this technology for space, and their approaches vary. Made In Space’s prototype machines print simple plastic items by extruding a polymer-based material through a nozzle. Other methods of 3D printing use different feedstocks: powder, metal, even glass. Karen Taminger of NASA’s Langley Research Center in Virginia is working with a metal-printing technique called Electron Beam Freeform Fabrication, which she hopes to test on the International Space Station. The EBF3 method, as it’s called, uses a beam of electrons to melt metal wire, like a cross between a laser gun and a soldering iron, and deposits the metal in layers. The technology is ideally suited to space because electron beams require a vacuum, and, as Taminger explains, “in space, you’ve got vacuum for free.”
The current lab version of EBF3, bought from a commercial welding supplier in 2002, sits in the middle of a giant warehouse called the Fabrication Shop at Langley. The shop is filled with machines, including a cluster of 3D printers all quietly chirping away, making objects out of gel, wire, or plastic. The EBF3 device is one of the more imposing pieces. It’s a greenish-blue cube nine feet on a side, with a heavy sliding door and round windows like a space capsule’s. That’s only the vacuum chamber part. Inside, the electron gun and accompanying wire feeder hover over a heavy metal platform where relatively small metal objects (a maximum of six by two by two feet) are fabricated.
The whole apparatus weighs 50 tons. That’s far too heavy, obviously, to launch into orbit. “This system isn’t going anywhere,” says Taminger. But she and her team have built a smaller version that weighs only a ton, and are working on another that’s less than 100 pounds. At first, they’ll have to build a small vacuum chamber to house the printer inside the space station, where astronauts can easily use and maintain it, but in theory an operational version could be mounted on a platform outside, where there’s plenty of vacuum. If the part needs finishing, the astronauts could do that inside, using a glovebox to keep any excess material from floating around the station.
The most useful application of 3D printing in space may be the production of spare parts and tools. If something on the station breaks or gets lost, the crew often has to wait weeks for the next supply ship to bring up a replacement. Because a 3D printer requires only a bit of feedstock and a CAD file, it will be possible to print what the astronauts need as they need it.
The EBF3 technique could even be used for repairs. “One of the alloys we’re working with is 2219, which is the aluminum alloy that the entire [station] is built out of,” says Taminger. “Our goal is to have a small enough system, almost a hand-held type system, so the astronauts could go out and say ‘I need a fix there’ and be able to actually do a repair [on a spacewalk].” To see if the technique could help repair damage from a cosmic hailstorm, Taminger’s team plans to try using EBF3 in their lab to repair aluminum panels shot through with simulated micro-meteorites.
Making parts in space would dramatically reduce the mass sent to the station. Taminger points to a recent Johnson Space Center computer simulation that predicts ISS equipment failures. In any given simulation, five percent of the parts needed replacement. But it was never the same five percent. You could try to predict a replacement part you might need, but chances are you’d end up needing something else. Taminger thinks logistics planners could take advantage of these odds by sending up a 3D printer and enough feedstock (stored, perhaps, in an attached module) for just five percent of the station’s total mass of spare parts. The astronauts would be given CAD files for all the parts that might break, and would print out only what they needed.
That strategy could be important, even essential, on a human Mars mission, where no supply ships would be coming, so the astronauts would have to pack everything with them. Taminger has done some calculations based on NASA’s current Mars mission architecture. A Mars-bound ship would include roughly 20 metric tons of machined parts. To carry one spare for every part would add 20 tons. But if only 10 percent of the parts are likely to fail, and any one of them could be printed from a CAD file in flight, the ship would need to carry only two tons of feedstock. Printers should also, in principle, be able to reconstitute old tools and parts for use in making new ones.