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

All the replies about using air are right, but it’s not the highly compressed air from the ship’s air bank. That’s only used to surface in emergencies. For normal surfacing, it goes something like this:

1. Sub goes to periscope depth to make sure it’s safe to surface
2. Sub raises snorkel mast to bring in outside air
3. Sub fires up a device called the low pressure blower. This is provides air at low pressure but in tremendous volumes
4. The blower output is sent to the ballast tanks to push the water out of the bottom.