The modern torpedo is a powerful weapon which can destroy targets at 40 kms with a speed of 50 knots and a destruction potential equivalent to 400-600 kg of TNT.

Underwater weapons are designed to attack submarines or surface vessels. They can be of three types i.e. guided weapons, non-guided weapons and rocket and mortar weapons. Guided weapon is a torpedo, which is very powerful and most commonly used thus the focus here will be on the mighty torpedo. Non-guided weapons are mines and depth charges. Rockets and mortar weapons, such as anti-submarine grenades and anti-submarine rockets have the advantage of rapid response time since they travel to the target through air and also have the advantage of being less susceptible to decoys etc. A hybrid of this category is the rocket launched torpedo, which is carried to the proximity of the target via a rocket.

Torpedo

The modern torpedo is a powerful weapon which can destroy targets at 40 kms with a speed of 50 knots and are of two types, the heavyweight, launched from submarines, and the lightweight which is launched from ships, dropped from aircraft (both fixed wing and helicopters) or delivered by a rocket. They can be straight-running, wireguided and fire and forget. A modern torpedo could have a speed of 50 knots, range of 40 km, should have a combined acoustic and wake homing with an acquisition range of about 5 km and a destruction potential equivalent to 400-600 kg of TNT. The normal size is 6.5 metres in length with a standard diameter of 533mm or 650mm but will depend on the size of the launch tube. Salient sub-systems are:

Propulsion. Torpedo propulsion is of two types i.e. electrical propulsion powered by batteries and thermal engine powered by combustible fuel.

Propulsion motors. With the advent of Permanent Magnetic Motors, greater power to weight ratio has been achieved and brushless motors allow a continuously variable speed control. Faster torpedoes need more powerful motors.

Homing Head

Homing. The terminal guidance of the torpedo is provided by the homing system, which comprises of homing head and the signal-processing unit. Homing can be acoustic or wake. Homing head of most modern torpedoes have acoustic sensors which can be passive or active. In the passive mode the sensor receives the noise created by the target, whereas in the active mode the torpedo transmits acoustic energy and it receives the echoes reflected from the target. In wake homing a torpedo detects and homes on to bubbles that are created in the wake of the target and is effective only against surface ships.

Guidance. Torpedoes can be controlled by a submarine by means of a wire which provides a two-way communication between the submarine and torpedo. The wire used in modern torpedoes has a length of about 50-60 km, high data handling capacity and is made of fibre optic cable.

Warhead design. The desired explosive power of a heavy weight torpedo is of the order of about 400 kg of TNT and HE required for this purpose is about 250-300 kg. The use of shaped charge delivers the same punch with reduced weight of HE. Some modern torpedoes have an explosive weight of just 45 kg thus giving it high range and speed of the order of 65 kms and 60 knots respectively. A single modern heavy weight torpedo is sufficient to sink a ship of any size by exploding a few metres beneath the target hull almost at its centre. Some examples are:

US

Raytheon’s Mk-48 is a huge 19 feet torpedo with advanced homing, wire guidance capabilities and 300 kg warhead. Its original manufacturer is Hughes Aircraft which was later on acquired by Raytheon. It is designed to kill both fast, deep-diving nuclear submarines and high performance surface ships, and is carried by US Navy and Royal Australian Navy submarines. The Mk 48 Advance Capability (ADCAP) has improved target acquisition range, reduced vulnerability to enemy countermeasures, reduced shipboard constraints and enhanced effectiveness against surface ships. These torpedoes can operate with or without wire guidance, and can use active and/or passive homing, conducting multiple re-attacks if they miss the target. The Common Broadband Advanced Sonar System (CBASS) kit is for the Mk48 which gives the retrofitted torpedoes the ability to transmit and receive over a wide frequency band. In 2011, however, Lockheed Martin stepped into the picture with a key contract win for CBASS kits.

Raytheon’s Mk54. Light weight torpedo. It is a light weight torpedo designed for operating both in deep waters and littoral environment. Mk54 can be deployed on surface ships, helicopters or fixed wing aircraft to track, classify and attack underwater targets. It is integrated onboard the MH-60R maritime helicopter and is its primary weapon for ASW capability. Recently it has been successfully launched by the US Navy from the P-8A Poseidon aircraft, which Indian Navy is also acquiring.

Europe

Whitehead Alenia Sistemi Subacquei(WASS)-Italy

BlackShark. This is a heavyweight torpedo developed for Scorpene submarines. It features an electric-propulsion system, 50 knots top speed, a range of 50 km, active/passive acoustic homing head, multi-target capability and an counter-countermeasures system. It is in service with the French, Italian and the Chilean Navy. An improved version called F21 is being developed by WASS along with DCNS and is likely to be in service by 2015.

Flash Black. This was unveiled during the Defexpo 2012 held at Delhi. As per the WASS, Flash Black is the world’s first next generation lightweight torpedo. The torpedo which is yet to be developed has finished the design stage and will take 26 months from the start of the development. WASS is planning to talk to the DRDO for possible collaboration. The design of the Flash Back is highly versatile with the capability to be launched from multiple platforms(underwater and AUV, UUV and USV), against any target and in any environment, including littoral waters and extremely shallow bottom depths and in the presence of the most sophisticated countermeasures.

Atlas Electronik - Germany

SeaHake DM2 A4. The SeaHake DM2 A4 is currently used by 18 navies on over 150 submarines. At a test-firing in March 2012, the heavyweight torpedo SeaHake® mod4 ER (Extended Range) has achieved a range of over 140 kilometres. SeaHake® mod4 is the latest advancement of the DM 2 A4 heavy weight torpedo, which is in service with the German Navy as well as the navies of Turkey, Pakistan and Spain.

EUROTORP

EUROTORP is a consortium established in 1993 with the purpose of creating a world’s leadership in the field of light weight torpedo to include DCNS, WASS and Thales. Their MU90/IMPACT advanced lightweight torpedo (LWT) is claimed to be a leader of the third generation of LWTs. Its data is classified but it is understood that its linear variable speed is between 29-50 knots and has a range of 10 kms at maximum speed.

Thales

Thales has designed, developed and produced acoustic heads for the Eurotorp MU90 as part of the EURUTORP consortium due to its expertise in underwater acoustic and non-acoustic sensors.

Indian perspective

It is understood that India had made a request to the US Government last year to buy 32 MK-54 all-up-round lightweight torpedoes and allied equipment for P-8I maritime aircraft which the Indian Navyis procuring. The same torpedo is being integrated on the US Navy’s P8 systems. Boeing will be the lead integrator M-54 is Raytheon’s design. Lockheed Martin offers the GPS guided, High Altitude Anti-Submarine Warfare Concept System(HAAWC/Longshot) which enables launch of weapons from high altitudes and long standoff distances. India may like to acquire this system depending upon its operational requirement.

DRDO. DRDO is developing a light weight torpedo called TAL and a heavy weight torpedo called Varunastra.