[Bulwark]

Unless they use Air Independent Propulsion. Then they will be at least as quite as a nuke, and will have plenty of submerged endurance for the SSB mission

Dumb question, but what is Air Independent Propulsion?

I know that diesel electric subs are actually quieter than nukes, at least when they're running on batteries. The ex-UK upholder class (I think) which are now canadian subs were designed to hunt Russian nuclear subs. The only drawback was their range and the need to refuel.

[BladeLWS]

China will be shaking in its boots now...

[THORE JAN SVEN]

A link:

http://www.naval-technology.com/projects/type_212/

The propulsion system combines a conventional system consisting of a diesel generator with a lead acid battery, and an air-independent propulsion (AIP) system, used for silent slow cruising, with a fuel cell equipped with oxygen and hydrogen storage. The system consists of PEM (polymer electrolyte membrane) fuel cells, providing between 30 and 50kW each. Submarines equipped with those systems are capable of long-distance submerged passage to the area of operation.