(Published article in SP’s Naval Forces Feb-Mar 2013)
MUNITIONS FOR ANTI SUBMARINE AND ANTI SHIPPING
“Everywhere on the surface . . . extending as far as the circular horizon was mute evidence of the effectiveness of Germany’s unrestricted submarine campaign. We were constantly shifting our zigzag course to avoid smashed lifeboats, drifting hatch gratings, and the odd clutter of gear that rises to the surface from a sunken ship. Occasionally a shapeless undulating mass buoyed by a cork life jacket would drift by, and a brine bleached face would stare with empty eye sockets at the glaring sun.”
Attributed to an American sailor, Ray Mulholland, on the wreckage left behind by sinking’s in the Mediterranean in 1918 by German submarines.
The devastation caused by the German submarines in WWI led to evolving a standoff anti submarine warfare solution involving use of aircraft in detecting a submarine at sea and attacking it with depth charges, bombs and guns. In 1914, the Royal navy converted an old ocean liner in to a seaplane tender ship and christened it HMS Campania, for this ship, specially designed seaplanes were ordered. The first of such seaplanes, F.22, accepted in to the Royal Navy, had Sunbeam Maori engine of 260 hp, for armament it carried a 7.7mmLewis machine gun and a bomb load of up to 6x116lb bombs. Towards end of the WWI when the US joined the war effort, the US Navy in 1917 asked for a long range flying boat which could patrol and provide security cover to the supply ships crossing the Atlantic. The Curtiss Aeroplane and Motor Company constructed the Curtiss NC-1 to stringent US Naval standards and the first flight of the same took place on 4th of Oct 1918. Despite the fact that Armistice was signed in Nov 1918, US Navy went ahead with its order of 10 Curtiss NC air craft and utilised them.
During WW II, lot of scientific work was being done for detecting the hostile submarines, notable amongst them were the Magnetic Anomaly Detector (MAD) and the use of sono buoys. Interestingly since the MAD detects a submarine only after the aircraft has flown over it, a retro rocket system was developed (to fly backwards) to release the depth charge over the submarine.
The armament carried today by maritime aircraft and helicopters includes, anti ship cruise missiles, lightweight torpedoes, depth charges and bombs. The aim of this article is to focus on anti submarine and anti shipping air armament currently in use by major navies.
Air Dropped Depth Charges and Bombs. Finland was the first to use air dropped depth charges from its Tupolev SB aircraft in 1942. Subsequently the methodology was adopted by RAF Coastal Command. Later depth charges were designed for aerial deployment and have recently once again come into focus because of the ASW threat in littorals. These can be very effectively utilised for flushing out the lurking diesel submarines. Two depth charges are worthy of mention, these are the MK11 depth charge of UK and the BDC 204 depth charge of Sweden.
The Mk 11 depth charge was developed by British Aerospace(now BAE Systems) for air delivery from maritime aircraft and helicopters. The Mk 11 depth charge was designed for shallow water operations against submarines on the surface or at periscope depths. It is fully compatible for carriage and release from a wide range of ASW helicopters and fixed-wing maritime patrol aircraft. The Mod 3 version incorporates a 4 mm mild steel outer case and nose section, which is designed to withstand entry into the water at high velocities without distortion. It has been cleared for carriage on Lynx, Merlin, NH90, Sea King, and Wasp helicopters.
The BDC 204 depth charge was developed by Bofors Underwater Systems (now Saab Dynamics) for air delivery from maritime aircraft and helicopters of the Swedish Navy. It was designed for use against submarines operating in shallow waters or at periscope depth, and in order to cover a wide range of applications was produced in four different weight categories and with different sinking speeds ranging between 5.2 and 6.8 m/s. The depth charge can be deployed in patterns, with different depth charges set to detonate at different depths to achieve profound shock and damage to submarines. The BDC 204 family of depth charges is fitted with standard NATO suspension lugs and their design allows them to be carried as a high drag general purpose bomb or torpedo. They have been cleared for carriage on the Boeing Vertol 107 helicopter and CASA C-212 Aviocar maritime patrol aircraft.
Two air dropped bomb upgrade kits worth mentioning are Joint Direct Attack Munition (JDAM) by Boeing Corporation and the Dual Mode Laser Guided Bomb (DMLGB) by Lockheed Martin. The JDAM upgrades unguided bombs to all weather smart bombs. These bombs then acquire GPS aided inertial navigation system with a range of up to 24km.The DMLGB kit, upgrades existing laser guided bombs,LGBs and is used for precision bombing against non-hardened targets, it provides LGBs with a semi active laser, GPS/INS guidance.
Air Launched Torpedoes Few of the prominent air launched torpedoes are described below.
Stingray is a LWT manufactured by BAE Systems. It has a diameter of 324mm, weight of 267kg, and length of 2.6m. Its speed is 45kts with a range of 8km and its warhead is 45kg of Torpex. It can dive up to 800m.Stingray is fed with target data and other associated information prior to its launch, after entering water it searches for target autonomously in active mode and on acquiring the same, attacks it. It is carried by Nimrod aircraft. Stingray Mod1 is reported to have a shaped charge warhead and improved shallow water performance.
Mk46 Mod5 torpedo is the mainstay of US Navy’s air launched lightweight torpedoes. It is manufactured by Alliant Tech systems. It has a diameter of 324mm, length of 2.59m, with a weight of 231kg.It runs on Otto fuel, has a range of 11km with a speed of 40kts and can dive upto365m. It has a PBXN-103 warhead of 44kg. It has an advanced digital computer control system with a built in logic and tactics for search and re-attack. It has effectively performed in both deep and shallow waters and can attack both the nuclear as well as the smaller diesel submarine. Over 25000 MK46 torpedoes have been supplied to customers till date. Interestingly the Chinese YU-7 torpedo is said to have been developed from the MK46 Mod2.
The Mk 54 Lightweight Torpedo is a hybrid of technologies taken from MK 46, MK48 and MK50 torpedoes. It is supposed to have homing and warhead of the MK50 and propulsion package of the MK46 torpedo. It has incorporated COTS processing technologies for an advanced guidance and control system. It is stated to have sophisticated shallow water capabilities for littoral threats. It is understood that the MK54 torpedo has been requested for P8i aircraft by India.
The A244/S developed by WAAS and currently manufactured by the Euro Torp consortium is a 324mm diameter, 2.8m long, and 244kg weight torpedo. It has a cruise/surge speed of 30/39kts, with a range of 6km and depth up to 600m. Its Homing head can function in mixed, active or passive modes. It has special signal processing to distinguish target from decoys.
A244/S Mod.3 is the latest upgrade of the A244/S. It has more powerful propulsion battery, with an increased number of cells, which ensures a 50% increase in the endurance of the weapon to13.5 km. It has an Advanced Digital Signal Processor module to counter sophisticated torpedo countermeasures .The homing head has preformed multiple transmission and reception beams and multi-frequency operating capability. It can classify and track several targets simultaneously, and discriminate between the target and countermeasures.
MU90/Impact is in mass production for 6 major NATO and Allied Countries. The MU90/IMPACT torpedo is 323.7mm ‘NATO Standard’ calibre, 2.85 mm long with a weight of 304 kg. It is powered by an Aluminium-Silver Oxide sea water battery
using dissolved sodium-dioxide powder as electrolyte with a closed-loop electrolyte re-circulation system, the torpedo is propelled by an electronically controlled high-RPM brush-less motor driving a skewed multi-blade pump jet propulsor allowing a continuously variable torpedo speed automatically selected by in built logic of the torpedo. The control and guidance electronics, has embedded operational and tactical software including the signal processing, the data processing and the torpedo guidance algorithms, which enable the MU90 to continuously self-adapt its configuration and tactics. The inertial system is based on ‘strap-down’ technology enabling all-attitudes capability including bottom following capability. The warhead consists of V350 explosive, fully insensitive, shaped charge warhead, with an impact type exploder incorporating two mechanical and six electrical independent safety devices.
Low Cost Anti Submarine Weapon (LCAW) A200/A is a miniature torpedo developed by WASS. LCAW has been developed as an intermediary between air launched torpedoes and conventional depth charges. It is a low cost option which provides propulsion and guidance to a depth charge without the costs of a torpedo. The air dropped version A200/A is deployed from aerial sonar buoy dispensers. The weapon is primarily designed to engage targets in shallow water, like midget submarines. The A200/A version has a length of 914.4mm, weight of 12kg, and a diameter of 123.8 mm. The warhead is a 2.5kg PBX shaped charge and the LCAW has an operating depth from 15m to300m. It has a speed of about 18kts with a range of 2km.
Anti Ship Missiles. Some of the note worthy anti ship missiles are described in the succeeding paragraphs in a random order.
Sea Skua manufactured by MBDA (UK) is a 145 kg, 2.5m long ASM primarily launched from helicopters like Westland Lynx. It uses solid fuel and has a 30 kg SAP, RDX war head and has range of 25 kms. It utilises semi-active radar guidance system. FASGW-ANL; being developed by MBDA; is a 100kg, 2.5m long, high subsonic, over the horizon helicopter launched missile. It will have an IR seeker with two way data link and selectable target aim point.
RBS-15 is a long range ASM manufactured by Saab Bofors Dynamics. It is an 800kg, 4.33m long turbojet missile with a range of 250kms and has a 200kg HE warhead. It is a sub sonic sea skimmer using, GPS, inertial and active radar guidance. The MKIV version under development is likely to have a range of over 1000kms, dual seekers and warheads which can be changed depending upon the mission.
KH 35 is a Russian subsonic missile manufactured by Tactical Missiles Corporation. It has a weight of 520kg-610kg and a length of 3.85m-4.40m depending upon the launch platform. It has a turbo fan engine, a 145 kg HE warhead and a range of 130km.It flies at 0.8 Mach and uses inertial and ARGS-35E X band active Radar.
Yingji-82 (YJ-82) is a Chinese ASM manufactured by the China Haiying Electromechanical Technology Academy. It is a 715kg, 6.4m long missile with 165kg SAP warhead. It flies at .9Mach and uses inertial and terminal active radar guidance. It has range of ~500km to 120km depending upon the variant. This missile is in use by PLA Navy, Pakistan Air Force and Bangladesh Navy amongst others.
EXOCET AM 39 is from the EXOCET family being manufactured by MBDA. It is a 670kg, 4.69m long high subsonic missile with a range of 70 km. It uses solid propellant turbo jet engine and has inertial and terminal active radar guidance with a165 kg insensitive warhead.
AGM-84 Harpoon Block II being manufactured by Boeing is an 1160lb, 151.5in missile with a range of 67 nm. It has turbo jet cruise engine with a solid booster and uses GPS aided inertial guidance with terminal active guidance .It has a 500lb last warhead. Indian Navy has ordered this missile as a weapon outfit for its P-8i aircraft on order. Boeing also has an export permit for its Standoff Land Attack Missile Expanded Response (SLAM-ER). It has a range of ~250km with a 500lb Tomahawk derivative warhead. SLAM-ER is a high subsonic, 674.5 kg 4.4m long missile with Teledyne turbojet propulsion. The guidance system is Ring Laser Gyro Inertial Navigation System (INS) with multi-channel GPS. It has infrared seeker for terminal guidance with Man-in-the-Loop control data link from the controlling aircraft.
The quest for ultimate weapon against the lurking submarine and longer range ship attack appears unending as the advances in airborne sensors and weapons spur a similar trend in stealth, speed and lethality of the submarine and the ship, this in turn leads to further advances in airborne systems.