A modern conventional submarine has a formidable array of weapons at its disposal for dealing with the adversaries, be it a ship, another submarine or a target on land. Torpedoes are a choice when targeting surface ships and submarines in vicinity, and missiles when surface and land targets are far away. Submarines also lay mines clandestinely in enemy harbours ‘as wait and strike’ weapons. Succeeding paragraphs discuss some of the more prominent submarine weapons.

Torpedoes. The Mk 48 and the Mk 48 ADCAP wire-guided torpedoes are the main underwater weapons of the US submarines. Gould/Honeywell and Hughes Aircraft manufacture them respectively. This thermal torpedo has a range of 30 km at 65 kts (about 120 kmph) and 50 km at 40 kts (about 78 kmph). Self-guidance in active/passive acoustic homing mode is also feasible. The Royal Navy uses the Spearfish thermal torpedo by BAE Systems. It has a range of 65 km at a speed of 60 kts (110 kmph). It is a wire-guided torpedo with an autonomous active/passive acoustic homing mode. The Swedish Tp-62 (Torpedo 2000 export version) is also a thermal torpedo with a pump jet propulsor and a range of 50+km at a speed of 45+kts (about 83 kmph). It is also wire-guided with autonomous acoustic homing; Saab Bofors Underwater Systems are the manufacturers. The Russian 53-65KE is a wake homer using kerosene and oxygen for propulsion. It has speeds in excess of 45 kts and a range of 50 km. Whitehead Sistemi Subacquei has developed the Italian A184, also known as Blackshark. It uses electrical propulsion; for guidance, optical fibre as well as autonomous active passive acoustic sonar is used. The Mod 3 has advanced ECCM, better motor design and battery giving it a speed of 50+km at 50+kts. The German DM2A4Seehecht, manufactured by Atlas Elecktronik (SeaHake Mod 4, export version), was the first torpedo to be fitted with a fibre optic wire guidance system. It is the only modular design torpedo offering up to four silver-zinc battery modules to achieve a range of 50+km and speeds of 50+kts. It has a unique homing head using transducers in conformal array permitting it to detect targets in +/-100 degree in the horizontal plane and in +/-24 degree in the vertical plane. It also claims the least selfnoise among its competitors. Indian Navy has reissued RFI for a heavy weight torpedo for its ships and Scorpene submarines. In future, Indian Navy is likely to also deploy the indigenous Varunashtra on its ships as and when it is available.

Missiles. BGM-109 Tomahawk, manufactured by Raytheon, is perhaps the most famous and widely used submarine fired missile. The current version of this modular missile is equipped with network-centric warfare capabilities and can utilise data from a variety of inputs like UAVs, satellites, ground forces, etc. Loitering feature enables retargeting of its tactical version. It can also be preprogrammed to attack targets as per GPS stored data. The latest land attack upgrade can hit hardened targets (including large ships) up to a range of 1,700 km. A submarine uses its torpedo tubes to fire the MBDA produced SM39 Exocet missile. It is sea skimming turbojet missile with a range of more than 180 km, GPS waypoint guidance in addition to inertial and active radar, and has a warhead of 165 kg. Indian Navy has ordered it for the Scorpene submarines under acquisition. The Klub-S is the Russian anti-shipping missile with a warhead of 200 kg and a range of 220 km. It is subsonic missile with a supersonic terminal speed of 2.9 Mach. IDAS (Interactive Attack and Defence System for Submarines) is a new submarine torpedo tube fired missile under development by HDW and Diehl BGT Defence in Germany. It aims to target helicopters, medium-sized ships, as well as coastal land targets. The Indian Naval submarines may also field a mix of indigenous Shaurya and BrahMos missiles, as and when they are ready for deployment.

In the Indian context, with the fresh RFI for heavy-weight torpedoes, the field is again thrown open for 98 torpedoes required for submarines as well as unspecified number for warship Projects 15A & 15B. The Indian Navy would in all probability also look at submarine fired cruise missiles of smaller sizes than the BrahMos and tube-launched mines.

The author is former DG NAI and Senior Fellow at New Westminster College, Canada