In Gundam the O'Neill colonies are less plausible than the giant robots because the huge airspaces require large amounts of inert gases such as nitrogen, argon, helium, or SF6. I find it profoundly annoying that phys.org publishes a story every week or so about how lunar colonists could make oxygen for 'breathing' which is a way to burn out and not fade away unless you have four parts of some other gas.