The European Space Agency will test 3D printing metal on the ISS

The first metal 3D printer that will be used in space is on its way to the International Space Station. The Cygnus NG-20 supply mission, which is carrying the 180kg (397 lbs) printer, launched on Tuesday and is set to arrive at the ISS on Thursday.

Astronaut Andreas Mogensen will install the printer, which Airbus developed for the European Space Agency. The machine will then be controlled and monitored from Earth.

Polymer-based 3D printers have been employed on the ISS in the past, but metal 3D printing in orbit is said to pose a trickier challenge. The machine will use a form of stainless steel that’s often used for water treatment and medical implants because of how well it resists corrosion.

After the stainless steel wire is pushed into the printing area, the printer melts it with a laser said to be a million times more powerful than a typical laser pointer. The printer then adds the melted metal to the print.

The melting point of the metal is around 1,400°C and the printer will run inside a completely sealed box. Before the printer can operate, it needs to vent its oxygen into space and replace its atmosphere with nitrogen. Otherwise, the melted metal would oxidize when it became exposed to oxygen.

Given the higher temperatures that are employed compared with a plastic 3D printer (which heats to around 200°C), "the safety of the crew and the Station itself have to be ensured — while maintenance possibilities are also very limited," ESA technical officer Rob Postema told the agency's website. "If successful though, the strength, conductivity and rigidity of metal would take the potential of in-space 3D printing to new heights.”

Four test prints are scheduled. The printer will replicate reference prints that have been created back on Earth. The two versions will be compared to help scientists understand how printing quality and performance differs in space. Even though each print will weigh less than 250g (8.8 ounces) and be smaller than a soda can, it will take the printer between two and four weeks to create each one. The printer will only be in operation for a maximum of four hours each day, since its fans and motor are fairly loud and the ISS has noise regulations.

If the experiment goes well, it will pave the way for astronauts and space agencies to print required tools or parts without having to send the items on resupply missions. Metal 3D printing could also help with the construction of a lunar base using recycled materials or transformed regolith (moon soil and rock). It may come in useful for missions to Mars too.