Vacuum Laser welding is very much a thing already. Years back the old president wanted my team to build one from an old Wentgate e-beam chamber. Shipper destroy

Vacuum Laser welding is very much a thing already. Years back the old president wanted my team to build one from an old Wentgate e-beam chamber. Shipper destroyed the chamber in transit and my boss got into a silly fight with the vendor and shipper which killed the project. We then got a quote from EVO Beam who builds electron beam welders and other e-beam machines who does dual process, laser and EB in the same machine. Wound up buying another EB machine instead. The challenge of welding in a vacuum is the molten weld pool emits metal weld vapor which impinges on surfaces in a linear trajectory from the pool. Think PVD, physical vapor deposition. So your beam delivery optics get a nice coating of whatever you are welding. I had some fun ideas for mitigating this in our design but never put it to test.