[nradov]

And yet most large merchant ships are designed with a single engine, propeller, and rudder to optimize for cost instead of reliability. We have seen some spectacular failures of that approach recently, although it probably still makes sense in aggregate.

A major mechanical casualty beyond what the crew can repair usually means a tow to a shipyard. Flying more engineers in by helicopter would seldom help, and often isn't feasible.

[bumby]

This is true, but different than the maritime platforms I was talking about. The ones that tend to focus on reliability-centered optimization are platforms used for drilling, not transport. Even then, you will see instances where they decide to optimize for cost/schedule (eg Deepwater Horizon). IMO, that is a company-cultural issue.

Btw- reliability optimization doesn’t necessarily mean it is optimized to not fail. They are optimized to fail within some predetermined risk level. What that risk level should be is an entirely different discussion.

[LorenPechtel]

The bridge that collapsed wasn't due to a single engine, propeller or rudder. It was due to a single electrical system. One intermittent electrical issue left the ship basically helpless even though all propulsion and steering was undamaged.