Decoy in TMO

[titlis]

Does Decoy have no effect for destroyer's passive sonar at all?
And does Decoy have effect for Active sonar?

[Dogfish40]

As far as I know, the decoy is a noise-maker, so this would effect there listening devices. There have been several opinions as to the realism of the decoy launcher being in the game at all. Now that you mention it, I was reading a couple of different sources that said that there was some decoy technology being used, or at least developed in some of the fleet boats.:salute: I Quote [/QUOTE] From Admrl C. Lockwood, from his book 'Sink em' all'
Early one morning I went to the San Diego Naval Labora-
tory of the University of California Division of War Research
(UCDWR) at the invitation of Dr. G. P. Harnwell. He said
they were developing gadgets for both submarine and antisub-
marine warfare and that perhaps I might be interested in them.
Thus, by a casual visit, was begun one of the most valuable
contacts which submarines had with the scientific world. They
did indeed have gadgets in which I was interested: noisemakers
to jam enemy listening gear; decoys to throw antisubmarine
craft off the track of hard-pressed submarines and an FM Sonar
(Frequency Modulated Sonar) , which could be used for locating
submerged objects.

[TorpX]

I'm not 100% sure but based on what I've read the decoys are simply containers with c chemical, calcium carbide, which produces a gas (acetylene), when it comes into cantact with water. The bubbles of gas reflect sound back, but do not themselves create sound. Thus, they would mainly be useful in combating active sonar operation. This is the same as the germans used in their U-boats. It was said that it was initially very effective, but as allied sound operators caught on and became more experienced, much less so.

[Mescator]

As Torpx said, the Decoy produces bubbles which reflect active sonar. They have no effect on Passive sonar to my knowledge.

[WernherVonTrapp]

To the best of my knowledge (w/o references), the decoys affect both passive and active sonar but, to what extent, is debatable. Submarines would sometimes release bubbles that become trapped in various nooks & crannys in it's hull. DD sonar operators were trained to listen for this. Sub design was geared toward minimizing this as effectively as possible but I don't know how far it got in eliminating it. The bubbles released by decoy cannisters would fool the passive sonar operator into thinking he had located the telltale bubbles of a submersible while the bubbles themselves would assist in diffusing or deflecting the ASDIC.
In essence, it was supposed to make the enemy think you're over here, when you're actually over there.

[Dogfish40]

Well, There you go, I stand corrected as to the mechanics of the decoy. That's one of the reasons I love this forum, I learn a lot of stuff that's sometimes very hard to find in typical history books. My previous quote from the book "Sink em all !" finds Admrl Lockwood being shown some of this early technology. In the movie, "Hunt for Red October", there was one scene where Captain Ramious (sic) launches four or six of these decoys to confuse the torpedos coming at his stern. I'm wondering if these are the same type of decoys as (in the movie) they start bubbling like crazy after they are launched.
Good Hunting!
D40:salute:

[WernherVonTrapp]

Well, There you go, I stand corrected as to the mechanics of the decoy. That's one of the reasons I love this forum, I learn a lot of stuff that's sometimes very hard to find in typical history books. Not necessarily. I was speaking off the cuff from a memory that hasn't been very reliable for me lately. I could very well be mistaken about some (or all) of what I posted. I haven't checked any of my references (books) before posting.
The only thing I've been learning (thankfully still) in this forum is how incorrect I am about a lot of what I think I know.:D