Bold decoy pellet
A sonar decoy is a device for decoying sonar. Most are released from submarines to act as a false target.
Submarine decoys[]
Bold launch tube, in the stern compartment of a type XXI U-boat
The first submarine decoys were the German Bold fitted to U-boats of WWII. These were a pellet of calcium hydride in a simple metal container. On contact with sea water, the calcium hydride decomposed to produce a trail of hydrogen gas bubbles that acted as a bubble curtain and reflected ASDIC impulses to produce a false target. The container trapped hydrogen and floated, with a crude spring valve to maintain buoyancy to keep it at a constant depth.
Later decoys, such as Sieglinde, were motorised and could deploy their false target away from the host submarine, increasing safety.
Torpedo decoys[]
Decoys were also used by surface ships to decoy the developing acoustic torpedoes. These were usually towed behind the host.
Example decoys[]
Bubble decoys[]
Reflective bubble targets
Hammer and explosive decoys[]
These were intended to swamp the listening device with noise
- Siegmund
Signature decoys[]
Towed decoys[]
- Foxer, a British towed decoy to decoy acoustic torpedoes away from surface ships. Also used by the US as FXR and the Canadians as CAT.
- T-Mk 6 Fanfare, US development of Foxer
References[]
- ↑ Gannon, Robert (2009). Hellions of the Deep. Penn State Press. pp. 132–133. ISBN 0271038403. http://books.google.com/books?id=hiwd4xsBGu4C&pg=PA132&lpg=PA132.
External links[]
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The original article can be found at Sonar decoy and the edit history here.