Yes, I don't know what the norm is in submarines, but I don't really trust simple engineering models, and think at least 5x is what I'd want in almost any conte

Yes, I don't know what the norm is in submarines, but I don't really trust simple engineering models, and think at least 5x is what I'd want in almost any context. I did see that DeepFlight Challenger, Steve Fossett's unused/untested carbon fiber sub which used the same basic design as Titan, was only built to a 1.5x margin of safety. Experimental tests suggested it was only safe for a one time use, and shouldn't be used for multiple dives.