ESA testing metal 3D printing in space

Building the infrastructure that can sustain life is the first step to living outside of Earth's atmosphere. Seeing as it is currently impractical to launch hundreds of rockets laden with all the equipment and supplies needed for a space colony, the European Space Agency is testing extraterrestrial additive manufacturing with the first metal 3D printer delivered to the International Space Station.

Although several 3D printers already exist on board the ISS, the first of which arrived back in 2014, the ESA announced at the end of January that its most recent supply mission would hold the first one that can print with metal.

Developed by Airbus, its printer will be tested aboard the Columbus module to help improve the understanding of metal printing in orbit and provide valuable insights into operating this blossoming technology in space.

"This new 3D printer printing metal parts represents a world first, at a time of growing interest in in-space manufacturing," said ESA technical officer Rob Postema. "Polymer-based 3D printers have already been launched to, and used aboard the ISS, using plastic material that is heated at the printer's head, then deposited to build up the desired object, one layer at a time."

Printing stronger metal parts

With a 50-year track record of innovation, technological firsts, and industry milestones, Airbus is a leader in designing, manufacturing, and delivering aerospace products, services and solutions to its customers that span the globe.

With over 130,000 employees, Airbus is the largest aeronautics and space company in Europe and sits at the forefront of the aviation industry with operations for commercial aircraft, helicopters, defense, space, and security.

Foreseeing the need for manufacturing in future lunar and Martian outposts, Airbus has taken the first step to bringing a technology that can build and maintain those facilities aboard the ISS.

While 3D printers have already been used to replace or repair some of the parts aboard the ISS, since one of the major problems of extended missions in orbit is the resupply of parts and equipment that can take months to arrive, the crew remains limited in what it can accomplish with plastic.

"The metal 3D printer will bring new on-orbit manufacturing capabilities, including the possibility to produce load-bearing structural parts that are more resilient than a plastic equivalent," said Gwenaëlle Aridon, space assembly lead engineer at Airbus. "Astronauts will be able to directly manufacture tools such as wrenches or mounting interfaces that could connect several parts together. The flexibility and rapid availability of 3D printing will greatly improve astronauts' autonomy."

This logistical constraint is felt by nearly every leading space agency, and it will only intensify on future Moon and Mars stations in the coming decades.

Airbus

An infograph made by Airbus detailing the exacting measurements and specifications of the first metal 3D printer in space.

Space printing challenges

While the process of 3D printing has continued to be mastered on Earth, printing metal in space presents its own set of technical challenges.

"The first challenge with this technology demonstrator was size," said Airbus metal 3D printer system engineer Sébastien Girault. "On Earth, current metal 3D printers are installed in a minimum ten square meter laboratory. To create the prototype for the ISS, we had to shrink the printer to the size of a washing machine."

This miniaturization is needed in order to fit inside the rack in which the printer will be housed on board the ISS' Columbus Laboratory.

"At this size, we can print parts with a volume of nine centimeters high and five centimeters wide," Girault said.

The second challenge is safety. As it is paramount to protect the station from an inflammable printing environment caused by lasers and heat. The printer will sit in a sealed metal box, which acts like a safe.

Generally, the melting point of metal alloys compatible with this type of additive manufacturing can be in excess of 1,200 degrees Celsius (2,192 degrees Fahrenheit), compared to the roughly 200 C (392 F) for plastic.

"Gravity management is also key, which is why we chose wire-based printing technology. The wire is independent of gravity unlike the powder-based system, which always has to fall to the ground," added Girault.

In addition to the drastic thermal control, whether it's plastic or metal, fumes are emitted that have to be dealt with by filters and captured inside the machine so that they do not contaminate the air inside the ISS.

"Safety and contamination are key drivers for us not only for the ISS, but for future use on the Moon," said Aridon.

With so many aspects to consider, the team must have felt confident in its printer for it to be aboard the ISS. With metal printing capabilities now online, questions on its viability can now begin to be answered.

Can it be done in space?

One of the first questions the researchers asked surrounding metal 3D printing in space was, "Is metal printing suited to a microgravity environment?"

Hoping to get this answered first, two printers were used for this experiment: the "flight model" inside the ISS; and the "engineering model" on Earth.

Starting by printing four samples in space, which would then be sent back to Earth for analysis, the same specimens – in as much the same replicable environment – would be manufactured using the engineering model.

"In order to evaluate the effects of microgravity, ESA and Danish Technical University will perform mechanical strength and bending tests and microstructural analysis on the parts made in space and compare them to the other specimens," Girault explained.

With the samples completed, the first metal 3D prints will enable insight into the unique environment that space encapsulates. From this, it will help scientists determine next steps to correct faults or flaws and make improvements toward the first permanent structures on the Moon.

"Increasing the level of maturity and automation of additive manufacturing in space could be a game changer for supporting life beyond Earth," Aridon said. "Thinking beyond the ISS, the applications could be amazing. Imagine a metal printer using transformed regolith [moondust] or recycled materials to build a lunar base!"