Torpedo defence

Torpedo defence includes evasive maneuvers, passive defense like torpedo belts, torpedo nets, torpedo bulges, and sonar torpedo sensors, "soft-kill" active countermeasures like sonar decoys and sonar jammers, and "hard-kill" active defenses, like anti-torpedo torpedoes similar in idea to missile defense systems.^[1] Surface Ship Torpedo Defense and Countermeasure Anti-Torpedo systems are highly experimental and the US Navy ended trials on them in 2018.^[2]

Examples of Countermeasure Anti-Torpedo (CAT) Systems

Soft-Kill Countermeasures

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Soft-kill torpedo countermeasures include a variety of decoys and jammers designed to deceive or disrupt the tracking systems of acoustic torpedoes. These countermeasures can be towed, stationary, or self-propelled, and typically rely on acoustic signals, magnetic signatures, or bubble screens to mislead incoming weapons. E.g.

• Bubble decoys: Create reflective noise via chemical or gas discharge (e.g., Bold, Sieglinde).
• Sonar jammers: Saturate acoustic sensors with disruptive noise (e.g., Siegmund, ADC).
• Signature decoys: Simulate ship acoustics or magnetic fields to lure torpedoes away (e.g., Foxer, Nixie, Maareech, MG-series).
• Mobile/swimming decoys: Self-propelled, often reusable systems simulating ship movement (e.g., Rafael's SCUTTER Mk 3, Mobile Submarine Simulator).
• Integrated systems: Combine sensors, jammers, and decoys in one suite (e.g., Leonardo C30/S, Ultra SSTD, Rafael's Torbuster).

Hard-kill Countermeasures

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Hard Kill Countermeasure anti-Torpedo (CAT) systems are generally divided into two categories: Antitorpedo Mines (ATM) and Anti-Torpedo-Torpedoes (ATT). Both types rely on Torpedo Detection, Classification, and Localization (TDCL) systems to identify incoming threats. E.g.

Torpedo Detection, Classification and Localisation (TDCL):

• Ultra Electronics DCL Technology Demonstrator programme
• Surface Ship Torpedo Defence
• Rafael's BlackFish/MonkFish HMS (DSIT)^[3]

Anti-Torpedo-Torpedo (ATT) systems:

• Rafael's TORBUSTER a fourth-generation torpedo defense countermeasure developed by Rafael Advanced Defense Systems. Designed to neutralize incoming torpedoes in both shallow and deep water, it combines soft- and hard-kill capabilities. ^[4]
• The U.S. Navy’s Countermeasure Anti-Torpedo Torpedo (CAT), developed by Penn State’s Applied Research Laboratory. The CAT system was designed to counter wake-homing torpedoes, which detect a ship’s wake rather than its acoustic signature. The CAT torpedo operates autonomously after launch with “fire-and-forget” capability, using onboard sensors to search, target, and maneuver against threats. Developed under a high-priority program, CAT was produced within 24 months through extensive simulation-based design and modular construction, reducing costs significantly compared to legacy torpedoes. It was first deployed aboard the USS George H.W. Bush in 2013 and subsequently installed on additional vessels. ^{[5] [6]}
• The SeaSpider ATT system by ATLAS ELEKTRONIK has undergone successful live-fire trials. These tests involved detection and localization of incoming Mk 37-derived autonomous underwater vehicles (AUVs) and DM2A3 torpedoes using passive and active TDCL sonar systems. Upon detection, the SeaSpider interceptor was launched from an above-water launcher to intercept threats at their closest point of approach, with successful intercepts confirmed through acoustic and optical means. ^[7]

Antitorpedo Mines (ATM)

• ATM systems are considered a low-cost, broad-spectrum defense solution. These systems deploy neutrally buoyant mines into a ship’s stern wake, where they maintain depth and detect incoming torpedoes using acoustic and magnetic sensors. The mines then detonate to disrupt torpedoes following predictable paths. ^[8]
• In addition, the RBU-1000 anti-submarine rocket launcher is alleged to have anti-torpedo capability.

See also

• AN/SLQ-25 Nixie – sonar decoy that fakes passive, active and wake-homing returns