- wake homing (ship wake / water disturbance) > no counter yet
This is how a 'wake homing' torpedo works...
Passive sonar sensors detect acoustic anomalies, aka 'bubbles', created by the ship's wake
AND propulsion. The word 'and' is important because the wake cone has distinctive acoustic regions, furthest from the ship would have lesser noise than closer to the ship, and the cone is bounded by the wake lines.
Waterjet Wake Characterization Suite
Such wakes provide an excellent opportunity to wake homing torpedoes because of bubbles large acoustic cross section.
As the torpedo break thru the line, it will pick up, not necessarily a sudden drop, but a rapid decline in 'bubble' acoustics, the torpedo then make a 180deg turn, reenter the wake cone, traverse the cone area, break thru the opposite wake line, and repeat the process.
The important item here is that the torpedo
MUST break a wake line. Or it must think it just broke a wake line. If it does not sense what it was programmed to be 'normal' water acoustic signature, it will continue to traverse what it believe to be the wake zone. So to deceive a 'wake homing' torpedo, the defense is to create as large a wake zone as possible, compelling the torpedo to keep traveling in straight line until it find that rapid decline from 'bubble' acoustics to 'normal' acoustics that would indicate a wake line. It could travel so long that it would run out of fuel. Several ships abreast can create this large wake zone. The problem here is that the fleet must be aware of the threat in the area and coordination of their deception maneuvers may not be so easily developed, documented and trained in peacetime. Another technique is to create acoustic disruptions inside the wake cone.
Decoy device against wake-tracking torpedoes - Patent 6889590
Claims:
1. A decoy device for wake-following torpedoes, the device comprising a body of effervescent material that reacts with sea water to generate a cloud of bubbles simulating a phoney wake, wherein the effervescent material has grains in a size range of less than 100 μm, the device being characterized in that it has a covering of material that is soluble in sea water which delays the reaction of the effervescent material with sea water.
The Prairie/Masker system below illustrate well the differences between an active wake zone and one that is under some form of influences...
Prairie / Masker
Look at the differences between ships as far as their wake zones can be seen. This technique is for masking the acoustic signature of a ship but can be adapted for wake homing torpedo defense. Explosions can also create extreme acoustic disruptions to deceive these torpedoes.
