But, as with airplane doors (but in the opposite direction), if the door was designed to open outwards then you couldn't open it under pressure no matter how hard you pushed
At those pressures I don't think you would want to open the door even if you could. I was more thinking about being at the surface and having nobody else to unbolt it from the outside.
Oh yes, I am (though I am absolutely not a real engineer nor do I have any experience with subs) just questioning why they would need to bolt it from the outside anyways. If it was to keep occupants in, I would imagine that a door that opens outwards would solve that issue if submerged, and would still be openable on the surface
It is a simpler design to screw the nuts from the outside. Otherwise the hull would need through hull screws attached to the door or some sort of clamp around the hull edge by the door opening.
