[Monkey Face]

Er...if they’re “outside,” where do they get the oxygen to weld a good seam? I know there are oxygen tanks, but for a fire to be hot enough for a weld, it needs air.

Like the stuff we breathe, or even the stuff in water. But outer space?

[NicknamedBob]

"Er...if they’re “outside,” where do they get the oxygen to weld a good seam? I know there are oxygen tanks, but for a fire to be hot enough for a weld, it needs air."

They use electric arc welding. It works just fine in space (vacuum).

You're probably thinking of gas-welding, as with acetylene. That's often done underwater.