I’m not a submarine engineer, but I would have expected that some of the more complex systems would have failed before the pressure vessel. Then again, it seems like they chose a seemingly cost effective design that was apparently susceptible to fatigue. Combine that with a profit motive to dive as many times as possible before retiring the hull and I suppose an implosion was practically inevitable. Oh well.
I think it largely is a solved problem. They just didn’t use one of the known, well tested solutions. Instead they used a shape (cylinder with spherical end caps) known to have force concentration problems as well as a composite material known to be weaker under compression than in tension.
Then they bonded the titanium rings to the CF tube in a flippin’ warehouse. Not a dust free, temperature controlled clean room. Not under vacuum to ensure no trapped air in the epoxy weakened the seal. Nope, in a regular ass warehouse, by hand. And while the titanium rings would be pressed into place by the enormous amount of pressure from the water column, any leak no matter how tiny, would be catastrophic.
Not to mention the other corners they cut. What about all the other hazards for submersibles? Was there any way to protect the passengers if there was a fire, or smoke from the off the shelf electrical gear? What about restraints for the passengers should they surface under heavy seas or if the submersible were to become unstable? Would the ballasts be deployable if power is lost?
It’s a shock to me that it survived the first dive, let alone multiple. It’s negligent arrogance, plain and simple.