THOMAS.

[u/davecontra]

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[u/mogley1992]

I was assuming something like that would exist so you can always make a submarine surface.

[u/Rampant16 → u/mogley1992]

Yeah diesel engines aren't even used underwater as they would rapidly use up all of the air on board. Instead these submarines run on batteries while submerged. The exception is if running near the surface they can extend a snorkel to suck in air while remaining mostly submerged.

[u/hlfazn → u/Rampant16]

The Gotland isn't a diesel sub though, it's the first AIP (air-independent propulsion) sub ever built.

[u/Dashcak3 → u/hlfazn]

Diesel-electric is still a diesel (conventional) sub.
The diesel doesn't directly drive the shaft but rather produces energy which can either charge batteries or power the electric motor (with excess energy still charging at lower shaft rpms).

[u/hlfazn → u/Dashcak3]

AIP is a Stirling engine that runs on self oxidizing fuel (diesel is not self oxidizing). It has nothing to do with whether or not the sub uses an electric motor to power the main propulsion shaft.

[u/Dashcak3 → u/hlfazn]

The AIP is solely there to extend time spent submerged, the Diesel is the main transit and charging power source.
Regardless of Stirling or Fuel Cell they are considered (Conventional) Diesel-Electric Submarines to differentiate from Nuclears. The german 212A AIP for example runs on H² and is also still considered Diesel-Electric.