Pentane torpedo
| 21 inch Mark II | |
|---|---|
| Type | heavy torpedo |
| Place of origin | United Kingdom |
| Service history | |
| In service | c. 1914- Second World War |
| Used by | RN |
| Wars | First World War, Second World War |
| Production history | |
| Designed | c. 1910 |
| Specifications | |
| Diameter | 21 inch |
|
|
|
| Warhead | TNT |
| Warhead weight | 400-515 lb |
|
|
|
| Engine | wet heater |
|
Operational
range |
8,000 yards max depending on model |
| Speed | 29 to 35 knots |
| 21 inch Mark IV | |
|---|---|
| Type | torpedo |
| Place of origin | United Kingdom |
| Service history | |
| In service | c. 1916- |
| Production history | |
| Designed | c. 1912 |
| Specifications | |
| Weight | 3,206 lb (1,454 kg) |
| Length | 22 ft 7.5 in (6.896 m) |
| Diameter | 21 inch (533 mm) |
|
|
|
| Warhead | TNT |
| Warhead weight | 515 lb (234 kg) |
|
|
|
| Engine | Burner cycle |
|
Operational
range |
8,000 - 13,500 yards |
| Speed | 25 - 35 knots |
| 21 inch Mark V | |
|---|---|
| Type | torpedo |
| Place of origin | United Kingdom |
| Production history | |
| Designed | 1917 |
| Specifications | |
| Length | 7.1 m (23 ft 4 in) |
| Diameter | 21 inch |
|
|
|
| Engine | wet heater |
|
Operational
range |
4.6 km (5,000 yd) to 12.4 km (13,600 yd) |
| Speed | 40 knots (74 km/h) to 25 knots (46 km/h) |
| 21 inch Mark VII | |
|---|---|
| Type | heavy torpedo |
| Place of origin | United Kingdom |
| Service history | |
| In service | Second World War |
| Used by | RN |
| Production history | |
| Designed | 1920s |
| Specifications | |
| Length | 25 ft 6 in (7.77 m) |
| Diameter | 21 inch |
|
|
|
| Warhead | TNT |
| Warhead weight | 740 lb (336 kg) |
|
|
|
| Engine | oxygen enriched air |
|
Operational
range |
5,700 yards (5,200 m) |
| Speed | 35 knots |
| 21 inch Mark 20 | |
|---|---|
| Type | torpedo |
| Place of origin | United Kingdom |
| Service history | |
| In service | 1955-1980s |
| Production history | |
| Designed | c. 1950 |
| Specifications | |
| Weight | 1,810 lb (821 kg) |
| Length | 6.46 m |
| Diameter | 21 inches |
|
|
|
| Warhead weight | 196 lb (89 kg) |
|
|
|
| Engine | electric |
| Propellant | battery |
|
Operational
range |
12,000 yards (11,000 m) |
| Speed | 20 knots |
|
Guidance
system |
passive sonar |
There have been several British 21-inch (533 mm) diameter torpedoes used by the Royal Navy since their first development just before the First World War.
The 21-inch was the largest size of torpedo in common use in the RN. They were used by surface ships and submarines rather than aircraft which used smaller 18 inch torpedoes.
The first British 21 inch torpedo came in two lengths "Short" at 17 ft 10.5 in (5.45 m), and "Long" at 23 ft 1.25 in (7.04 m). The explosive charge was 200 lb of gun cotton increased later to 225 lb.
The Mark II, chiefly used by destroyers, entered service in 1914. Apart from some older British ships, it was used with the old US (destroyers for bases agreement) Town-class destroyers provided to the UK during the early part of the Second World War. The running speed was reduced from 45 knots (over 3,000 yards) for better reliability.
The Mark II*, an improved Mark II was used by battleships and battlecruisers. A wet heater design, it could run for 4.1 km (4,500 yd) at 45 knots (83 km/h)
From 1912, used by destroyers and other surface ships and was an important weapon in the first World War. In the Second World War they were carried on HMS Hood.
The Mark V was used by the A and B-class destroyers and, with modification, by the Kent-class heavy cruisers.
The Mark VII was issued for use on the British heavy cruisers; i.e. cruisers with 8-inch guns. Designed in the mid-1920s the County-class cruisers were built at the same time in the post Washington Naval Treaty period.
The power came from the use of oxygen enriched air, though torpedo stocks were converted to run on normal air at the start of the Second World War.
Specifications:
Mark VIII
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