Originally Posted by
air pig
I think that spheres are far harder to compress than a tube like structure as such and the vessel can work in a 1atm environment just the same a SSN/SSBN. If you loook at the Trieste, the occupied part was indeed a sphere. Sphere's 6 & 7 obvioulsy contain the nuclear power plant which for any reason has a failure at those depths being isolated may protect the crew whilst the emergency blow even if the stern end was either seriously damaged or even missing. Pure supposition I know.
I understand that the sphere is better than a cylinder for resisting pressure - it's just that I'd never seen such a design used on anything but a small diving bell - not a full blown sub.
It seems like a (heavy duty) pressure hatch between the aft and forward compartments could achieve the same isolation while allowing the crew to move around (something similar to what they use to ingress/egress on the surface) . Being locked into that aft reactor area on a long mission would be a nasty duty.