The Mark 24 Tigerfish was a heavyweight acoustic homing torpedo used by the Royal Navy (RN) during the 1980s and 90s. Conceptual development dates to the mid-1950s, and formally started in 1959 with a target introduction date in 1969. A lengthy development process led to a greatly reduced performance requirement, including the removal of anti-surface capabilities. The first prototype "Tiger Fish" examples were delivered in 1967.
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 and speed up during the attack phase.
Testing in 1969 revealed many problems, especially with the seeker system. An upgrade program was ordered, producing the Mod 1 which regained the surface-attack mode. Testing from 1975 led to a production order in 1977, but it was not until 1983 that these officially entered service. Service during the 1982 Falklands War revealed serious reliability problems. A more significant upgrade program followed, the Consolidation Programme, which addressed the complete weapon system including the fire control system. This emerged as the much more reliable Mod 2, which entered service in 1987. A final upgrade series, Mod 2*, entered service in 1992. A simplified inexpensive version, Mod 3, was not produced.
While Tigerfish was being deployed, a new project was started that more closely followed the original performance requirement, and ultimately greatly surpassed it. This became the much more capable Spearfish torpedo, which began replacing Tigerfish starting in 1988. The last examples of the Tigerfish retired in RN service in 2004. Tigerfish was also operated by Turkey, Chile, Brazil, Colombia and Indonesia. A total of 2,184 Mk. 24s were produced.
Design and development
The initial concept developed in the mid-1950s was for a fast, , 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.
The weapon was known as Project ONGAR because Ongar railway station was, until 1994, the last on the Central line of the London Underground system. The engineers developing this weapon were confident that it would be so advanced that it would be "...the end of the line for torpedo development".
The programme ran into serious problems in the late 1950s because the technology required was too advanced to meet an in-service target date of 1969. In addition, the closure of the Torpedo Experimental Establishment, Greenock, Scotland in 1959 and the transfer of its staff to Portland in Dorset disrupted the pace of development.
In the early 1960s a series of wide-ranging reviews (one report was titled "Whither ONGAR?" - the pun being intentional) led to a greatly reduced performance specification which was realistically expected to achieve an in-service date of 1969.
The propulsion system was changed from an internal combustion engine to an electric motor with a silver zinc battery as the power source. This reduced the planned speed of the weapon from with a short final-attack-phase capability at .
The homing system was simplified by the exclusion of the anti-surface ship capability in the Mod 0 weapon.
Only the wire-guidance system was retained relatively unchanged. This was similar to the system used on the earlier Mk 23 torpedo.
The original requirement for a crush depth of was overtaken by rapid advances in SSN deep-diving performance and the requirement was progressively increased to and then .