What is needed to sink a US Navy task force?

[lwd]

...If you drop a depth charge in the vicinity of one of the US submarines ... remember you don't know where they are ... you have just given the TF commander an excuse to solve the whole problem by sinking all of your ships.
....

Wouldn't dropping depth charges anywhere near also tend to produce echos from the subs that might be detected? You wouldn't get a good fix but ...

[Legend]

If you drop depth charges your sonar systems are basically paralyzed. Unless you have a direct hit on the sub, the bubbles and vortices resulting from the charge disturb the water enough that the sound created from the bubbles are enough to mask out any sub. The bubbles last for a varying amount of time, depending on the depth and current, so there is a good chance a sub commander will take advantage of that and move in closer... or reposition and wait it out.

[lwd]

But that's if the sub and the ASW vessel are fairly close. If a depth charge is dropped say 10 or 20 miles away and the sub is 5 miles away off bearing then there shouldn't there be a detectable echo?

[Bgile]

But that's if the sub and the ASW vessel are fairly close. If a depth charge is dropped say 10 or 20 miles away and the sub is 5 miles away off bearing then there shouldn't there be a detectable echo?

If the submarine was that far away it would depend on the characteristics of the sonar on your ship and where you were pointing it. You would get echoes from the bottom and all the other ships and wrecks in the area. Active sonar is based on sending a directional sound pulse out on a specific bearing and listening on that bearing for the return echo. The pulse frequency is optimized for the characteristics of your sonar receiver. An explosion is a broad band omnidirectional noise and generally not all that helpful at submarine detection. Explosions are sometimes used by hydrographic ships under carefully controlled circumstances.

[lwd]

I wouldn't expect it to give much info. Indeed the math is none trivial for even figuring the curve along which the target could be. On the other hand if you've got good people listening they might get a hint that something is out there. My impression is that that is a lot of what the US attack boats do ... listen.

[Bgile]

I wouldn't expect it to give much info. Indeed the math is none trivial for even figuring the curve along which the target could be. On the other hand if you've got good people listening they might get a hint that something is out there. My impression is that that is a lot of what the US attack boats do ... listen.

Well, when I served on them, that is ALL we did. Active sonar was shut down and tagged out on patrol so it couldn't be accidentally triggered. We really only used it on exercises. Whether that is still the case I can't say, but it gives away your location and you can get good ranges without it.

[lwd]

It's not much more that hear say as far as I know but my impression is that there are some very talented listners on US subs. You might be able to address that better than me.

[Bgile]

It's not much more that hear say as far as I know but my impression is that there are some very talented listners on US subs. You might be able to address that better than me.

We had means of determining range based on bearing rate, target type and screw rpm, and own ship's course and speed. We would track the target for a few minutes and then change own ship's course and would soon have a good passive solution. And yes we were very good with passive sonar because it was our only sensor below periscope depth. Sonar is not an additional sensor for an SSN. It's THE main sensor for the ship and everyone relies on it implicitly, so the sonar operators have to be very good at what they do and the sonars themselves (each ship has several different types) are the best technology available. Unlike in most movies, there were always three to five sonar tecs on watch at any given time.

[Legend]

I am sure. The more I think upon it the more all of that makes sense. So Bgile, what is the chances of a diesel or old nuc to be picked up if it was sitting on the bottom silently, infront of the moving Task Force... assuming they could guess the course of the CVN...

[Bgile]

I am sure. The more I think upon it the more all of that makes sense. So Bgile, what is the chances of a diesel or old nuc to be picked up if it was sitting on the bottom silently, infront of the moving Task Force... assuming they could guess the course of the CVN...

First, nuclear submarines can't sit on the bottom because they suck muck into the sea water inlets. Secondly, old nukes, especially old Soviet Nukes, are very noisy.

Diesels can be very hard to detect under any circumstances unless they have to actually run the diesel, and then they are easy to detect. The problem is trying to guess where the CVN is going to be and be there. In practice it's very difficult to do. If you get lucky, you probably have a good chance to attack a CVN.

[Legend]

I seem to recall "Black Missions" back in the Cold War where a USN Sturgeon or Los Angeles class situated itself onto the seafloor while a dive team left the sub, placed line taps on Soviet communications, and returned to the submarine. Or did I just hear some old, high end, conspiracy theory?

[Bgile]

I think the story might be at least partly true, but I can't imagine how a nuke could sit on the bottom. Maybe it was a diesel.

[Legend]

I remember it was a Sturgeon... although I vaguely remember something about modifications... I'll try to find the source!

[Legend]

Down this page under Variants...
http://www.absoluteastronomy.com/topics ... _submarine

About 3/5 of the way down under label 191 it talks about the Operations...
http://jya.com/usic08.htm

This also came up... an earlier ship than I thought...
http://en.wikipedia.org/wiki/USS_Halibut_(SSGN-587)

[Bgile]

I was aware of Halibut's special function, but not personally involved. It appears from the article that they anchored and hovered with slight positive boyancy, which would make it unnecessary to set down on the bottom.

I was directly involved in Cold War submarine intelligence operations but I still don't feel comfortable talking about it very much even though it was many years ago. We were far superior to the Soviets in most areas of submarine technology.