[Oatka]

The commander, Peter Scott, ordered his stricken submarine to gather speed and blow the ballast tanks to make the submarine lighter. He ordered the sub to rise but it failed to respond, causing hearts to freeze.

It's my understanding that, on nuclear boats, even when all ballast tanks are blown they still need engine power to get to the surface. I think that what killed the Thresher - lost power and went below crush depth. In the old fleet boats (WWII) I was on, if you blew the tanks, even with a flooded compartment, you went UP.

[pfflier]

What contributed to the events that killed Thresher was the screen on her vent tube iced over preventing the ballast tank from being vented. Rickover created the SUBSAFE program to detect and prevent such engineering flaws.

[relee]

... It's my understanding that, on nuclear boats, even when all ballast tanks are blown they still need engine power to get to the surface ...

Perhaps that is true on the newer boats but it is not true on the older SSNs & SSBNs I sailed on.