Reprint courtesy: M. Edwards GEC-Marconi Underwater Weapons Division Elettra Avenue Waterlooville Hampshire PO7 7XS United Kingdom Telephone 00 11 44 1705 264 466 "In the UK torpedoes are specifically designed to match existing systems and tubes. Therefore they are limited to 21 inches in diameter and approximately 20 feet in length. Weight restrictions also have to be taken into consideration because of the limitations placed on the lifting capacity of the handling gear. Thus a torpedo is a volume and weight limited device, not only overall, but also in the relationship between its diameter, length and hydrodynamic performance. Two factors prevented the torpedo from breaking away from its simple straight-running condition to become a true underwater-guided weapon. First, the medium of detection and guidance in a very difficult, and continually changing underwater environment. It is only recently that detailed knowledge of the environment, combined with sufficient data and computer power necessary to filter and manipulate such data, has become available. Second, the development of underwater-guided weapons did not have the availability of money, resources, firing ranges and support that was lavished on above-water guided weapons development. It was not until the 1970's and early 1980's that the UK made a breakthrough in detection and homing producing a true underwater-guided weapon, albeit not submarine launched, but the lightweight air and ship launched Sting Ray torpedo. Many of the design and production lessons learnt were incorporated into the heavyweight Tigerfish and Spearfish torpedoes. Based on some brilliant concepts originating in the Admiralty Underwater Weapons Establishment, Portland, in the early 1970's the development of Sting Ray was managed from within the MoD, but was starved of funds and resources. This changed in 1977 with the transfer of development to industry. Sting Ray was, and is, the vehicle for the introduction of the advanced homing techniques, which had previously not been available to designers. Not only were advanced acoustic and transducer devices used but, most important of all, an on-board computer capable of controlling the weapon and its tactics was incorporated with the ability to process, by means of algorithms and software, the data obtained from the torpedoes sensors. Allied to the acoustic and electronic advances were many non-electronic ones, also critical to the performance such as: The introduction of a pump-jet with contra-rotating propulsors in place of conventional propellers. A revolutionary seawater battery system. Special hull joints to allow the torpedo to survive at depth. Aft-mounted control surfaces to provide control and agility. Careful attention to hydrodynamics and boundary flow with much testing in wind and water tunnels. Tigerfish Tigerfish or the Mk 24 torpedo is currently the primary anti-submarine and anti-surface weapon carried by all of the Royal Navy's submarine fleet, both diesel electric and nuclear propelled. It is a very quiet torpedo, indeed arguably the quietest in the world, designed to meet the requirements for covert operation. It was also recognised that the torpedo was only one part of the overall weapons system consisting of: The connecting guidance wire. The torpedo tubes. The discharge and handling gear. The fire control system. The action information system. And of course, the operator. Spearfish 'Faster, quieter, deeper,' is the aim of all submarine designs and much progress has been made in improving these aspects, especially with regard to nuclear submarines coming into service. In addition to titanium hulls, and double skins combined with the protective effect of missile pods mounted externally to the pressure hulls make these extremely tough targets. It was for this reason that in the early 1980's the UK Ministry of Defence decided to embark on a programme to supplement its anti-submarine warfare by a new advanced heavyweight torpedo against a very stringent staff requirement. Two possibilities were considered: To acquire the United States MK 48 ADCAP torpedo. To fund a proposal for a new UK design based on development work already carried out by the Admiralty Underwater research Establishment and Marconi. The MoD opted for the UK solution named Spearfish. Spearfish is a submarine-launched heavyweight torpedo designed to operate totally autonomously from all Royal Navy submarines and interfacing with a minimum of modification to all weapons handling and fire control systems. Spearfish meets the Royal Navy requirement to counter faster, deep diving, quieter and stronger-hulled submarines, as well as dealing with surface targets and is equally capable in shallow coastal waters. The torpedo's advanced sonar and homing system enables it to primarily operate in a passive mode. However, when required to operate against a very quiet target, or in the final stages of attack, the active mode is used. Although it has been possible to design torpedoes to match the historical built-in parameters of submarines, these parameters are beginning to be limiting, and we need to be considering how these may be overcome for future weapons. In particular the need for high speed, short range, quick reaction weapons in large numbers capable of being discharged in almost any direction in a melee situation. It is time to recognize the fact that the torpedo is now an extremely advanced underwater guided weapon."