This means no welds have been performed in orbit for four decades – until this recent automated experiment, involving an electron beam welding gun, flown on a SpaceX Falcon 9 launched from Cape Canaveral on 6 May.

This experiment employed electron beam welding, the very same method used during the 1969 Soyuz-6 experiment. It involves directing a beam of high-velocity electrons onto the metal, so that kinetic energy is transformed into heat. Electron beam welding has the advantage of being highly controllable, penetrating deep into the metal to be welded, with no wasted energy. It can only be performed in high-quality vacuum, making electron beam welding a good fit for space. And this system may be capable not just of welding, but also cutting and 3D printing.