British 21-inch torpedo

During the early part of the Second World War, apart from some older British ships, it was used with the old US (destroyers-for-bases deal) Town-class destroyers provided to the UK.

During the First World War, the Mark II was primarily used by battleships and battlecruisers, as well as submarines fitted with 21-inch launch tubes, such as the L, M, and G classes.

The Royal Navy employed a system whereby successive modifications of torpedoes were marked with increasingly numerous asterisks.

The RGF Mark III incorporated features of the RGF Mark II***, as well as a novel design for the water bottle, a different gas generator, a double reducer adapted for the use of heavy fuel oil, and a direct oil injection system which was projected to increase the weapon's endurance to 13,000 yd (12,000 m).

This was not realized, causing the weapon's introduction to be indefinitely postponed, favor being passed on to improved variants of the Mark II.

In the Second World War they were carried as auxiliary armament on submarines and various surface ships, including HMS Hood.

Considerable self-noise and reverberation hampered the effort, and the project was halted with funding being cut off as the war ended.

[17] At the beginning of the 1960s, the Mark VIII was the only feasible anti-surface ship weapon available to the Royal Navy submarine service.

During the torpedo capability crisis, in 1969, Admiral Michael Pollock, Flag Officer Submarines, proposed multiple solutions.

In 1943 it was decided to further improve the Mark IX** by lengthening it 12 inches (30.5 cm), and the weapon mass limit to 4,000 lb (1,800 kg), up to the capacity of torpedo tubes and ships under construction.

The final version of what would have become Mark IX*** took up the extra space by enlarging the warhead to 930 lb (420 kg) of Torpex.

Prior to the Second World War, the Royal Navy was mostly uninterested in electric torpedoes as they had poor performance compared to the piston-driven units already in service, and trackless torpedoes were deemed of dubious use, since their low speeds and stealthy nature rendered them most suited to sneak attacks against slow vessels, e.g. unrestricted submarine warfare.

The project commenced in earnest after the Royal Navy saw a need for a weapon which did not leave a bubble track on the surface in the Mediterranean sea.

The first production rounds were finally issued to the fleet in August 1944 and some were delivered to the Far East, with the war ending before any were used in action.

Self-noise, the noise generated by the torpedo's own propulsion system, has a large effect on the sensitive hydrophones of the seeker head.

[31] Specifications:[32][33] Mark XI A design for a high-speed torpedo propelled by high-test peroxide (HTP), based on wartime research by Hellmuth Walter during the Second World War.

Crewmen on the submarine were in the process of loading one of the prototype torpedoes into a launch tube, when the stop valve on the weapon was accidentally opened, triggering the release of reactant in its propulsion unit.

As of 1958, the E variant was still not ready for service due to problems with its programming, and the prospect of a medium-range ASW torpedo being carried by the upcoming Westland Wasp helicopter was deemed more desirable.

This led to several of the frigates that were intended to have used them (Rothesay and Whitby classes) never being fitted with torpedo tubes or having them removed.

It featured weight reductions to its synchromechanisms and the contra-rotating propeller gearing, and the earlier mechanical course and depth setting devices were replaced by electronic ones, receiving data from the launch console via an umbilical link.

This was an alternate version of the S configuration, fitted with the same warhead, using elements of the E project in an effort to make a marginally faster weapon for both ASW and ASuW.

This was an underwater, submarine-launched, equipment delivery vehicle designed to support clandestine operations, particularly those of the frogmen of the Special Boat Service.

Like other such vehicles of the type, the "Archimedes" could beach itself in a controlled manner, allowing frogmen or other clandestine agents to open the capsule and retrieve its contents.

[50] The Mark 20 was the only torpedo in service which could fit the short stern launch tubes of the Oberon and Porpoise-class submarines.

[53][54] Development commenced in 1949, and a final design was selected in 1954, delivering functional prototypes with a speed of 30 knots and an endurance of 12000 yards.

Following the 1957 Defence White Paper, which de-emphasized the role of aircraft carriers, the RAF Coastal Command was left as the sole operator and the project was cancelled in 1958 due to cost considerations and an assessment that the weapon lacked the speed to counter upcoming nuclear submarine designs.

An operator onboard the submarine would listen to the torpedo's hydrophones, guiding the weapon past decoys and countermeasures.

[66] During the trials phase of the Mark 23, in 1965, Captain John Moore of the Royal Navy experimented with a sample of the torpedo body.

[citation needed] After months of investigation it was discovered that the fault lay in the Guidance Unit made by GEC.

Despite the highly problematic development program of the Tigerfish, Britain would repeatedly decline American offers of the Mark 48.