How could a generation ship maintain a source of potable water?
Some questions about space travel just do not seem to be about world building. I am thinking they should be off topic. However some of them do seem to be about world building:
In space, do "shipping lanes" make sense?
So how should we handle these. Do we want to allow for space travel questions if they could be tangental to world building? I do not think we want to completely rule out space travel but rather limit it only to that which is directly linked to world building.