Submarines dive by allowing water to expel air from their … tanks? How do they regain buoyancy in order to surface?

Question

Submarines dive by allowing water to expel air from their … tanks? How do they regain buoyancy in order to surface?

In: Engineering

Answer 1

I think submarines are generally pretty close to neutral buoyancy most of the time when submerged and because they don’t compress (much) that buoyancy doesn’t change with depth like a scuba divers BCD does.

At neutral buoyancy as long as they are moving forward, they fly along wherever their control surfaces dictate.

At the surface they would add extra buoyancy so they can stay surfaced without forward movement, and then expell that air to dive.