Sting Ray (torpedo)

The Sting Ray torpedo is a current British acoustic homing light-weight torpedo (LWT) manufactured by GEC-Marconi, who were later bought out by BAE Systems. It entered service in 1983.

Design and development
The early 1960s concept was to provide the Royal Navy with a British-built torpedo to replace the imported Mk 44 and Mk 46 US weapons. In the 1950s the Royal Navy was equipped with British designed and built Mk 30 air-dropped torpedoes. These were passive homing weapons which relied on detecting the noise from submarine targets. However as submarine noise levels decreased these weapons became ineffective.

A design for a British Mk 31 torpedo which would have used active echo-location sonar failed to receive Government approval for production and US Mk 44 torpedoes were purchased for the Royal Navy in the 1960s. These were later replaced by US Mk 46 torpedoes.

Design
A desire to not be dependent on US torpedo purchases led to a research programme starting in 1964 to develop a British torpedo. Initially designated Naval and Air Staff Requirement (NASR) 7511, it was (much later in the late 1970s) designated the Sting Ray torpedo.

Design studies in the mid-1960s proposed that a tank of polyethylene oxide be carried behind the warhead. This polymer would be exuded at the nose to reduce the drag coefficient. Experiments using buoyancy-propelled torpedoes in 1969 had shown reductions in the drag coefficient up to 25%. However, by 1969 this scheme had been rejected in favour of carrying a larger battery.

The homing system developed in the mid-1960s incorporated a spinning magnetic disc onto which the acoustic correlation algorithms were etched but this was replaced by integrated circuit technology when the disc sometimes failed to survive the impact of the weapon with the sea from high altitude launches.

The original warhead concept was for a simple omnidirectional blast charge. However, studies in the 1970s showed that this would be inadequate against the large double-hulled submarines then entering service. A directed energy (shaped charge) warhead was used in the production weapon.

In 1976 the designs had to be completely revised. Swapping the project for buying a ready-made US torpedo was not considered because the torpedo was expected to be better, and was all-British. The project manager was Eric Risness CBE.

Manufacture
The torpedo was built at the MSDS plants at Neston (in Cheshire) and MUSL in Farlington Portsmouth. Guidance systems were made by Sperry Gyroscope Company.

Deployment
The original in-service version (Sting Ray Mod 0) entered service in 1983. It is propelled by a pump jet driven by an electric motor. Power is supplied by a magnesium/silver-chloride sea water battery. The propulsion method combines high speed, deep diving, agility and low noise levels. The weapon is provided with target and environmental information by the launching platform. Once launched it operates autonomously, with tactical software searching for the target using active sonar and then homing in without any further assistance. The software is designed to deal with the employment of countermeasures by the target. The weapon is designed to be launched from fixed wing or rotary winged aircraft and surface ships against submarine targets.

The development of the torpedo cost £920 million. The Mark 24 Tigerfish submarine-launched torpedo had also overshot its initial budget.

Dimensions
Sting Ray has a diameter of 324 mm (12¾ inches) and a length of around 2.6 metres (8.5 feet). It has a launch weight of 267 kg (589 lb), and carries a 45 kg (99 lb) Torpex warhead. It has a speed of 45 knots (83 km/h) over a range of 8,000 metres (4.3 nautical miles).

Sting Ray Mod 1 is intended to used against the same targets as Sting Ray Mod 0 but with an enhanced capability against small clad conventional submarines via a shaped-charge warhead, and an improved shallow-water performance. It shares many hull components with the original weapon.

Specifications

 * Length : 2.6 m
 * Diameter : 324 mm
 * Weight : 267 kg
 * Warhead : 45 kg of HE in a shaped charge
 * Speed : 45 knots
 * Range : 8–11 km
 * Depth : 800 m
 * Propulsion : Magnesium/silver chloride seawater battery (Pump-jet)
 * Guidance : Active/Passive sonar

Defence scientists deaths
The deaths of over 20 defence workers closely connected with the project has been the subject of journalistic research and inquiry calls.