SSK Agosta 90B Class Attack Submarine, France

The Agosta submarines designed by DCN (now DCNS) of France, are currently in service with the French, Spanish and Pakistan navies. The Agosta 90B is an improved version featuring higher performance and a new combat system.

The new submarine features a higher level of automation, which has resulted in the ship's crew being reduced from 54 to 36. Other improvements include a new battery for increased range, a deeper diving capability of 350m resulting from the use of new materials including HLES 80 steel, and a reduced acoustic signature through the installation of new suspension and isolation systems.

Three Agosta 90Bs were ordered by the Pakistan Navy in September 1994. The first, Khalid (S137), was built at DCN’s Cherbourg yard and was commissioned in 1999. The second, Saad, assembled at Karachi Naval Dockyard, was launched in August 2002 and was commissioned in December 2003. The third, Hamza, which has been constructed and assembled in Karachi, was launched in August 2006 and will commission in 2007.

Work on the third vessel halted after a terrorist attack in May 2002, which killed 11 French engineers in Karachi. It has since restarted.

The third submarine is being fitted with the MESMA air-independent propulsion system, which will be retrofitted to the first two. The MESMA AIP has successfully completed Pakistan Navy acceptance trials.

In March 2007, Pakistan placed an order with DCNS for the retrofit of the MESMA AIP to the first two Khalid Class submarines. The retrofit kits will be delivered to the Karachi dockyard in 2011.

Pakistan has been given a license by DCNS to offer commercial production of the submarines to potential customers.

SUBTICS COMMAND AND CONTROL SYSTEM

The Agosta 90B submarines are equipped with a SUBTICS fully integrated combat system. This is supplied by UDS International, a joint subsidiary of DCN International and Thales, now wholly owned by DCNS. SUBTICS processes signals from the submarine's sensors, determines the tactical situation by track association, fusion, synthesis, trajectory plotting and management and handles all weapon command and control functions.

TORPEDOES

The Agosta 90B submarine is fitted with four bow 533mm torpedo tubes and has the capacity to carry a mixed load of up to 16 torpedoes and missiles. The submarine can be equipped with the ECAN F17 Mod 2 torpedo, which is a wire-guided torpedo with active and passive homing to a range of 20km. The torpedo delivers a 250kg warhead to a depth of 600m.

MBDA EXOCET SM39 MISSILES

The Agosta 90B is equipped with the torpedo tube launched MBDA (formerly EADS Aerospatiale) Exocet SM39 missile. Target range and bearing data is downloaded into the Exocet's computer.

The missile approaches the target area in sea-skimming mode using inertial navigation and then active radar homing. The missile travels at speeds over Mach 0.9, and has a range of 50km. Exocet has a 165kg high-explosive shaped-charge warhead.

ELECTRONIC WARFARE

The Agosta 90B submarines are equipped with the Thales DR-3000U radar warning receiver, operating in D to K bands.

The system uses a masthead antenna array with omnidirectional and monopulse directional antennae and a separate periscope warning antenna.

SENSOR SUITE

The submarine is fitted with a Thales Underwater Systems (formerly Thomson Marconi Sonar) TSM 223 sonar suite, which includes bow-mounted sonar and towed sonar arrays, SAGEM periscopes and navigation system and Thales I-band navigation radar.

PROPULSION SYSTEMS

The Agosta 90B class submarines can be equipped with a diesel-electric propulsion system or the MESMA air-independent propulsion system. The diesel-electric system consists of two SEMT-Pielstick 16 PA4 V 185 VG diesels providing 3,600hp and a 2200kW electric motor driving a single propeller.

A diesel-electrical submarine has to surface to periscope depth to recharge the batteries using the diesel engine, leading to increased risk of detection. The MESMA air-independent propulsion system, being fitted to the Agosta 90B submarines for Pakistan, allows the submarine to remain submerged three times longer.

The MESMA system consists essentially of a turbine receiving high-pressure steam from a combustion chamber, burning a gaseous mixture of ethanol and liquid oxygen. The Agosta 90B's performance remains the same in all other respects, except that the length increases from 67m to 76m and submerged displacement from 1,760t to 2,050t.