Would exposure to a vacuum “weld” metal objects together?
I was reading the first Rama novel which describes how an Astronaut fears an airlock may be vacuum welded shut after long exposure to a vacuum. Its written by Arthur C Clarke so it must have some basis or is it just another way of saying that the mechanism may have siezed?
Probably the latter but that depends on how broad your definition of welding is. Materials that outgas and change composition would do so more in a vaccuum.
It’s a real effect. Lack of a film of air between metal surfaces increases friction and makes them tend to adhere to each other. In the early days of space launches, many people were concerned about it. You don’t hear about it much anymore, because it hasn’t proved to be nearly the problem that was anticipated. The “golden age” SF writers were from the era when it was being discussed a lot.
As yabob says, it’s a real effect. Many metals are more reactive than they appear because they are covered with a thin oxide at the surface. Aluminum is a notable example. But if you cut aluminum in a vacuum so the oxide can’t form and make the two surfaces very smooth they will form a weld on contact. It doesn’t happen IRL because the parts are manufactured in the atmosphere even though they’re used in space.
WARNING: This is all recollection from a metallurgy class taken long ago. I’ll see if I can’t find something more definitive, as my memory has failed me more than once in the past. (I think it did, anyway. I can’t really remember.)