Countermeasure and Counter-Countermeasure Between Surface Ship and Wake Homing Torpedo

The countermeasures of surface ship is based on ship wake signature suppression or making false wakes. Ship wake signature suppression includes wake bubble coalescing and wake energy absorbing. For producing a good degree of bubble coalescence, ultrasonic transducer (or array) must be towed to the join region of the bow wake, the turbulent boundary layer wake, and the initial spreading end of the propeller wake. Wake energy absorber mounted on the ship aft of the propulsor weakens the wake and renders the wake less pronounced acoustically. These two methods reduce the quantity of microbubbles in the wakes, so current wake-homing torpedoes are not able to counter these measures. Nevertheless, the wake homing torpedoes can be able to recognize actual wakes and false wakes. By estimating the average values of instantaneous frequencies of wake echoes, the actual wake of a ship and the false wake of a decoy can be identified based on the difference between motion properties of real wake bubbles and false wake bubbles. Two principles of trajectory design for anti-false wake are suggested.