Mark 24 Tigerfish

Tigerfish
Type	Heavyweight homing torpedo
Service history
In service	1979-2004
Used by	Royal Navy
Production history
Manufacturer	Marconi Underwater Systems Ltd (Mod 2 Variant)
Specifications
Weight	1,550 kg (3,417 lb)
Length	6.5 m (21 ft)
Diameter	533 mm (21 in)
Maximum firing range	39 km (21 nmi) at low speed 13 km (7 nmi) at high speed
Warhead	Torpex
Warhead weight	134 to 340 kg (295 to 750 lb)
Engine	Electrical chloride silver-zinc oxide batteries
Speed	35-knot (65 km/h; 40 mph)
Guidance system	Wire-guided to point of passive sonar target acquisition and passive terminal homing sonar. Option of using active acquisition and homing.
Launch platform	submarine

The Mk 24 Tigerfish torpedo was a heavyweight acoustic homing torpedo used by the Royal Navy (RN) for several years. The early Mod0 and Mod1 variants were unreliable and unsuccessful, but were issued to the RN even though they failed Fleet Weapon Acceptance. Reliability was significantly improved in the Mod2 variant as a result of the Consolidation Programme which addressed the complete weapon system i.e. the on-board fire control system (TCSS10 and DCB) and the Mk24 torpedo. The Consolidation Programme was initiated following the torpedo's reliability failures during the Falklands War. It was headed by Marconi Underwater Systems as prime contractor with Ferranti Computer Systems and Gresham Lion as major sub-contractors. The Tigerfish was eventually replaced in Royal Navy service by the more capable Spearfish torpedo.

The Tigerfish was fitted with both active and passive sonar and could be remotely controlled through a thin wire which connected it to the launching submarine. Wire guidance permits a torpedo to be launched on-first-warning, i.e. when a target is first detected at long range. This permits the torpedo the time needed to close the range while target course and speed is being updated by the submarine's superior sensors and transmitted 'down-the-wire'. The torpedo can also be reassigned to another target or recalled. Typically, wire-guided torpedoes initially run at low speed (in order to maximize their range and to minimize their self-generated noise) while they close the range (the approach speed) and speed up during the attack phase (the attack speed).

The initial concept developed in the mid-1950s was for a fast, 55-knot (102 km/h; 63 mph), deep-diving torpedo driven by an internal combustion engine, carrying high pressure oxygen as oxidant, guided by a wire system developed from the Mackle wire-guidance study dated 1952 using data transmitted from the firing submarine sonars and using an autonomous active/passive sonar developed from the abandoned 1950s UK PENTANE torpedo project.