Emergency surface - blowing all ballast?

[jmr]

In SH3/SH4 when you conduct an emergency surface only a partial amount of compressed air is used to blow water out of the ballast. Is this correct? I thought when one blows ballast to emergency surface all compressed air is used up in the process.

[vanjast]

It seems to be regulated to certain 'doses' of pressure, or valve timing.

If you're very deep and you do not have enough pressure, you cannot vent.. and down you go.:)

[skookum]

Ballast, by definition, is heavy. The ballast in submarines is the water in the ballast tanks. When the crew "blows all ballast" they need only use enough compressed air to replace all the water in the ballast tanks with air. All subs of reasonable design carry enough compressed air to blow ballast several times over at resonable depth. I say reasonable depth because the deeper the submarine, the lower the volume of water that can be displaced from the ballast tanks by compressed air of a given pressure and temperature. Therefore the number of ballast blows available at crush depth is less than the number of ballast blows available at periscope depth. On top of that, if a submarine sustains flooding inside the pressure hull, then the water inside the pressure hull reduces the total buoyancy of the submarine. No amount of compressed air can increase the total buoancy of a submarine once the ballast tanks are empty. So the crew must pray that the flooding is not "critical," in the sense that the water in the pressure hull would reduce total buoyancy below neutral, thus guaranteeing the boat's demise and loss of her crew.

[vanjast]

There you go :up: