The difficulty is not about joining large structures airtight. otherwise we would have trouble with building commercial aircraft. the problem is when you want

The difficulty is not about joining large structures airtight. otherwise we would have trouble with building commercial aircraft. the problem is when you want to make something out from the absolute minimim weight possible due to economy of putting things into space, then you can't do with any connections whatsoever. The pressure of -1 bar isn't particularly challenging engineering wise.