The torpedo belt was part of the armouring scheme in some

warship A warship or combatant ship is a naval ship that is built and primarily intended for naval warfare. Usually they belong to the armed forces of a state. As well as being armed, warships are designed to withstand damage and are usually faster a ...

s between the 1920s and 1940s. It consisted of a series of lightly armoured compartments, extending laterally along a narrow belt that intersected the ship's

waterline The waterline is the line where the hull of a ship meets the surface of the water. Specifically, it is also the name of a special marking, also known as an international load line, Plimsoll line and water line (positioned amidships), that indi ...

. In theory this belt would absorb the explosions from

torpedo A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, su ...

es, or any

naval artillery Naval artillery is artillery mounted on a warship, originally used only for naval warfare and then subsequently used for naval gunfire support, shore bombardment and anti-aircraft roles. The term generally refers to tube-launched projectile-firi ...

shells that struck below the waterline, and thus minimize internal damage to the ship itself. Torpedo belts are also known as Side Protection Systems or SPS, or Torpedo Defense System or TDS.

Background: insufficiency of belt armor

Armoured warships (

dreadnought battleship The dreadnought (alternatively spelled dreadnaught) was the predominant type of battleship in the early 20th century. The first of the kind, the Royal Navy's , had such an impact when launched in 1906 that similar battleships built after her ...

armoured cruiser The armored cruiser was a type of warship of the late 19th and early 20th centuries. It was designed like other types of cruisers to operate as a long-range, independent warship, capable of defeating any ship apart from a battleship and fast eno ...

s and later

light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...

and

heavy Heavy may refer to: Measures * Heavy (aeronautics), a term used by pilots and air traffic controllers to refer to aircraft capable of 300,000 lbs or more takeoff weight * Heavy, a characterization of objects with substantial weight * Heavy, ...

cruisers) of the early 20th century carried their main protective armour above the waterline – the "

main belt The asteroid belt is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies, of many sizes, but much smaller than planets, called ...

" – which was intended to stop flat-trajectory gunfire from piercing the hull. Below the belt, the armour generally tapered away, to reduce overall weight. This, however, makes a ship vulnerable to hits below the waterline from torpedoes and the occasional large-calibre shell. Extending the belt downwards is impractical, since this increases displacement and

draft Draft, The Draft, or Draught may refer to: Watercraft dimensions * Draft (hull), the distance from waterline to keel of a vessel * Draft (sail), degree of curvature in a sail * Air draft, distance from waterline to the highest point on a vessel ...

, reducing speed and seaworthiness.

Torpedo protection schemes

Another solution was needed. Originally,

torpedo net Torpedo nets were a passive ship defensive device against torpedoes. They were in common use from the 1890s until the World War II, Second World War. They were superseded by the anti-torpedo bulge and torpedo belts. Origins With the introduction ...

s were tried. These were heavy metal mesh nets hung out on booms at some distance from the sides of ships to catch or detonate torpedoes short of the ship. These proved largely ineffective since they could only be deployed when ships were stationary, were useless against shell hits below the waterline, and were ineffective against mines. Some ships were fitted with underwater armor in vulnerable areas below the waterline. This stopped torpedoes from penetrating the ship, but the shock from an

underwater explosion An underwater explosion (also known as an UNDEX) is a chemical or nuclear explosion that occurs under the surface of a body of water. While useful in anti-ship and submarine warfare, underwater bombs are not as effective against coastal facilities. ...

could cause damage to weapon mountings and sensitive machinery, along with violently stressing the ships' structure. The German Imperial

High Seas Fleet The High Seas Fleet (''Hochseeflotte'') was the battle fleet of the German Imperial Navy and saw action during the First World War. The formation was created in February 1907, when the Home Fleet (''Heimatflotte'') was renamed as the High Seas ...

introduced torpedo belts with the first modern armored cruiser

SMS Blücher SMS was the last armored cruiser built by the German Empire. She was designed to match what German intelligence incorrectly believed to be the specifications of the British s. was larger than preceding armored cruisers and carried more heav ...

and the simultaneous battleships of the Nassau-class since 1908. It was the only fleet during the duration of the First World War to do so.

Anti-torpedo bulges

The outbreak of

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

increased the urgency to devise an effective torpedo defense system (TDS), thus the

British British may refer to: Peoples, culture, and language * British people, nationals or natives of the United Kingdom, British Overseas Territories, and Crown Dependencies. ** Britishness, the British identity and common culture * British English, ...

Director of Naval Construction The Director of Naval Construction (DNC) also known as the Department of the Director of Naval Construction and Directorate of Naval Construction and originally known as the Chief Constructor of the Navy was a senior principal civil officer resp ...

introduced the

anti-torpedo bulge The anti-torpedo bulge (also known as an anti-torpedo blister) is a form of defence against naval torpedoes occasionally employed in warship construction in the period between the First and Second World Wars. It involved fitting (or retrofittin ...

. Originally retrofitted to older ships, this was soon added to ships already under construction. In 1915, the British s and in 1917

American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...

s introduced anti-torpedo bulges. Most later capital ships would have at least one

torpedo bulkhead A torpedo bulkhead is a type of naval armour common on the more heavily armored warships, especially battleships and battlecruisers of the early 20th century. It is designed to keep the ship afloat even if the hull is struck underneath the belt ar ...

inboard of the external hull plating along the area of the ship protected by the armour belt. Most battleships built after World War I had sophisticated and complex side-protection systems, as illustrated by the cross sectional drawing of and .

Torpedo belts

It was not until 1922, in the wake of the

Washington Naval Treaty The Washington Naval Treaty, also known as the Five-Power Treaty, was a treaty signed during 1922 among the major Allies of World War I, which agreed to prevent an arms race by limiting naval construction. It was negotiated at the Washington Nav ...

that curtailed ship weights and with the introduction of the British s, that a true layered torpedo belt was introduced. The two ''Nelson''s used a water-filled belt, which was written off in the tonnage limits, as water was not part of the calculations for allowed displacement. Over the next 20 years many innovative designs of TDS were tried by various nations. A warship can be seriously damaged underwater not only by torpedoes, but also by heavy

shells that plunge into the ocean very close to the targeted ship. Such shells which are usually

armor-piercing shell Armour-piercing ammunition (AP) is a type of projectile designed to penetrate either body armour or vehicle armour. From the 1860s to 1950s, a major application of armour-piercing projectiles was to defeat the thick armour carried on many wars ...

s (AP shells) can pass through a short stretch of water and strike the warship some distance below the waterline. In 1914 typical AP shells were expected to punch a hole in the exterior plate and detonate there with a destructive effect similar to a torpedo. However by the 1940s, advances in AP shell technology incorporated delayed fuses which give AP shells deep penetration capability before exploding; such AP shells will typically make a smaller hole than a torpedo in breaching a ship's hull, but detonating beyond the belt in the hull can cause splinter damage to machinery spaces and secondary magazines, which in turn compromises watertight integrity and encourages progressive flooding.http://www.navweaps.com/index_lundgren/Kirishima_Damage_Analysis.pdf To improve protection against both shells and torpedoes, an air space can be added between the torpedo belt and the hull to increase the

buoyancy Buoyancy (), or upthrust, is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the p ...

of the warship.

Today

After the end of

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

torpedo belts, much like many of the large warships they protected, were rendered obsolete by the widespread use of aircraft, and eventually—especially in the late 60s and into the 70s—by the use of

anti-ship missile An anti-ship missile (AShM) is a guided missile that is designed for use against ships and large boats. Most anti-ship missiles are of the sea skimming variety, and many use a combination of inertial guidance and active radar homing. A good ...

s, and a new generation of "smart", deep-diving torpedoes (such as the

Mark 48 The Mark 48 and its improved Advanced Capability (ADCAP) variant are American heavyweight submarine-launched torpedoes. They were designed to sink deep-diving nuclear-powered submarines and high-performance surface ships. History The Mark 48 w ...

) which are designed to detonate under a ship's

keel The keel is the bottom-most longitudinal structural element on a vessel. On some sailboats, it may have a hydrodynamic and counterbalancing purpose, as well. As the laying down of the keel is the initial step in the construction of a ship, in Br ...

and break its back.

Citations

Bibliography

*{{cite journal , last1=Okun , first1=Nathan, title=Question 27/45: ''Yamato'' Class Lower Belt Connection , journal=Warship International , date=2010 , volume=XLVII , issue=2 , pages=93–95 , issn=0043-0374

External links

A detailed discussion of the evolution of Torpedo defense systems
Naval armour Anti-submarine warfare