The term "emergency blow" comes from submarines, where in an emergency all the ballast tanks are blown empty with high-pressure air to force the boat to the surface in the shortest possible time. It's normally not done on the surface, but thanks to Jalopnik's Foxtrot Alpha blog we get to see it. This is the Sturgeon class submarine USS L. Mendel Rivers conducting an emergency blow test in harbor. The action starts at about 1m. 32sec. into the clip.
There are more video clips of emergency and high-speed surfacing maneuvers at the link, including a couple of Soviet submarines. Interesting viewing.
Peter
The last frame...
ReplyDeleteI rode a few Los Angeles-class fast attack subs up from test depth on emergency blow tests. Once they build up a bit of momentum there's no stopping 'em.
ReplyDeleteRode through one on a 637... One helluva elevator ride! And yes, the DO crash back to the surface... Rattles the teeth and anything not tied down! :-)
ReplyDeleteLet's see if I've got this right. They were testing the "high pressure air into ballast tanks" whilst on the surface.
ReplyDeleteThere was me expecting the sub to go down and pop up again. Maybe next time.
I expected it to rise a little. But it didn't even seem to bob on the waves. Any submariners here that can explain?
ReplyDeleteNot a submariner, but my educated guess is that the ballast tanks were already empty. This was just to test the mechanism before taking it down at sea for a real test. IIRC, one of the contributing factors to the loss of the USS Thresher was a problem with the emergency blow. Specifically, moisture in the compressed air freezing in the lines as the air expanded.
ReplyDeleteI know this comment is a bit late (I do have the excuse of having been underway).
ReplyDeleteLarry is correct. Any surfaced submarine is going to have mostly empty ballast tanks, so doing a blow (be it low pressure or high pressure as in an emergency blow) would have little to no observable effect, at least until the POOD checks the draft readings.