A small, unassuming metal object sits on a workbench at the European Space Research and Technology Centre (ESTEC) in the Netherlands. At first glance, it seems ordinary—just another piece of stainless steel. But this is no simple object. It is the first metal part ever 3D-printed in space, a milestone that could redefine how humans build in the harsh environment of space.

The part, which was produced aboard the International Space Station (ISS) last year, recently returned to Earth for extensive testing and studying. If its qualities are confirmed, it could usher in a new age for space exploration.

3D printing metal in space

Space exploration is a logistical nightmare. Every piece of equipment, every tool, and every spare part must be carefully designed, tested, and transported potentially across millions of miles—often at staggering costs. If something breaks unexpectedly, astronauts must either rely on what they have or wait for the next resupply mission, which could take months or even years. That’s why technologies like in-space 3D printing, especially with durable materials like metal, are game changers.

The story of this metal part begins with that bold idea: that astronauts could manufacture parts in space, without having to rely on costly and infrequent resupply missions. That idea took a major step forward in January 2024, when ESA astronaut Andreas Mogensen installed the first-ever metal 3D printer inside the Columbus module of the ISS.

The 3D printer was developed by Airbus. It’s a 180-kilogram machine designed to work in a zero-gravity environment, using a high-powered laser to melt stainless steel wire layer by layer. It was a far more complex challenge than previous 3D printing efforts on the ISS, which had been limited to plastic. Metal printing requires extreme heat—around 1,400°C (2,552°F)—and a carefully controlled atmosphere to prevent oxidation.

After months of setup and fine-tuning, the printer produced its first test shape: an “S”-shaped curve. Then, in mid-2024, it created the first fully realized 3D-printed metal object—a small, round part with several cylindrical features. A second object was printed in December.

A big technological challenge

Printing in microgravity isn’t as simple as pressing a button. On Earth, molten metal naturally settles into place due to gravity. In orbit, engineers had to ensure that surface tension alone could hold the liquid metal steady as each layer was deposited.

Furthermore, scientists need to prevent oxidation. The printer operated in a sealed environment filled with nitrogen and before astronauts could retrieve the finished part, oxygen had to be carefully reintroduced into the environment.

Despite these challenges, the results were promising and the 3D-printed objects look solid. Now, one of those objects has completed its return journey to Earth. It will be studied at ESTEC’s Materials and Electrical Components Laboratory for structural strength, while the second object will go to the Technical University of Denmark for further research. If these objects are as good as researchers hope, it could be a game-changer for space exploration.

“Metal 3D printing represents a greater technical challenge, involving much higher temperatures and metal being melted using a laser. With this, the safety of the crew and the Station itself have to be ensured – while maintenance possibilities are also very limited. If successful, though, the strength, conductivity and rigidity of metal would take the potential of in-space 3D printing to new heights,” says technical officer Rob Postema from the European Space Agency (ESA).

Why this is such a big deal

Currently, every nut and bolt needed aboard the ISS—or on future missions to the Moon and Mars—must be manufactured on Earth and launched into space. That process is expensive, time-consuming, and limits astronauts’ ability to adapt to unexpected problems.

Beyond printing spare parts, future versions of this technology could help build large structures in space. Instead of launching pre-assembled satellites or habitats, astronauts could manufacture them on-site, reducing the weight and cost of missions.

Even more ambitiously, ESA envisions a future where in-space recycling could repurpose old satellite components into new tools.

“Metal 3D in space printing is a promising capability to support future exploration activities, but also beyond, to contribute to more sustainable space activities, through in-situ manufacturing, repair and perhaps recycling of space structures, for a wide range of applications. This includes in-orbit large infrastructure manufacturing and assembly as well as long-term planetary human settlement. These aspects are key focuses in ESA’s upcoming technology cross-cutting initiatives,” says Tommaso Ghidini, Head of the Mechanical Department at ESA.

Four interesting shapes have been chosen for now. These objects will be compared to reference objects 3D printed on the ground to see if and how the space environment affects the printing projects. The objects are all smaller than a can of soda, but they’re valuable proof of concept.

If studies confirm their properties, researchers will move on to more complex objects as well as faster 3D printing. For now, it takes two to four weeks to print objects, with the printer operating four hours per day.