Naval armour
Naval armor refers to the various protections schemes employed by warships. The first ironclad warship was created in 1859, and the pace of armour advancement accelerated quickly thereafter. The emergence of battleships around the turn of the 20th century saw ships become increasingly large and well armoured. Vast quantities of heavily armoured ships were used during the World Wars, and were crucial in the outcome. The emergence of guided missiles in the last part of the 20th century has greatly reduced the utility of armor, and most modern warships are now only lightly armored.
Naval armour consists of many different designs, depending on what the armour is meant to protect against. Sloped armour and belt armour are designed to protect against shellfire; torpedo belts, bulges, and bulkheads protect against underwater torpedoes or naval mines; and armoured decks protect against air dropped bombs and long-range shellfire.
The materials that make up naval armour have evolved over time, beginning with simply wood, then softer metals like lead or bronze, to harder metals such as iron, and finally steel and composites. Iron armour saw wide use in the 1860s and 1870s, but steel armor began to take over because it was stronger, and thus less could be used. The technology behind steel armour went from simple carbon steel plates, to increasingly complex arrangements with variable alloys. Case-hardened Harvey armor was the first major development, followed by chromium alloyed and specially hardened Krupp armour. Ducol steel came into use in the 1920s, and was widely used on World War II era ships. Futuristic armor designs include electric armour, which would use electric shielding to stop projectiles.
History
Pre-industrial examples
Early ship armour probably had its origins in applying thin sheets of metal to ship undersides for preservative reasons. There are only a few exceptional examples of ships equipped with metal armor before Industrial Revolution. The Syracusia, built by Archimedes for Hiero II around 250 BC, featured an iron fortification against enemy boardings. Spanish admiral Juan de Lezcano also built a primitive ironclad vessel in 1505. The Santa Anna built by the Knights Hospitaller in 1522 was also reported to be an ironclad carrack. Also, the Galeone di Venezia from the Battle of Preveza might have been covered with iron plates. The Finis Belli was described as a possible candidate for "the first ironclad" by authors in the late 19th and early 20th century. The Finis Belli was a stationary floating fighting platform that was built by the Dutch during the Siege of Antwerp in 1585. It was supposedly equipped with iron plates but never actually saw action.According to science historian Joseph Needham, thin metal sheets were used as protection on the superstructure on war junks during the Song dynasty and that this tradition was carried on in the Korean turtle ships that fought against Toyotomi Hideyoshi's invasion of the Korean peninsula in the 1590s. The use of iron plate armor on the turtle ships has been suggested in various sources from the 19th century onwards but is not attested in contemporary sources. Kuki Yoshitaka, a Japanese admiral of the same period, ordered the construction of ships armored with iron pavises called. Medieval Japanese vessels also used bundled bamboo taketaba to defend against bullets and small cannon shot.
First ironclads
The first ironclad battleship, with iron armour over a wooden hull, La Gloire, was launched by the French Navy in 1859 prompting the British Royal Navy to build a counter. The following year they launched HMS Warrior, which was twice the size and had 4.5 inches of wrought iron armour over an iron hull. After the first battle between two ironclads took place in 1862 during the American Civil War, it became clear that the ironclad had replaced the unarmoured line-of-battle ship as the most powerful warship afloat.Ironclads were designed for several roles, including as high seas battleships, coastal defence ships, and long-range cruisers. The rapid evolution of warship design in the late 19th century transformed the ironclad from a wooden-hulled vessel which carried sails to supplement its steam engines into the steel-built, turreted battleships and cruisers familiar in the 20th century. This change was pushed forward by the development of heavier naval guns, more sophisticated steam engines, and advances in metallurgy which made steel shipbuilding possible.
The rapid pace of change in the ironclad period meant that many ships were obsolete as soon as they were complete, and that naval tactics were in a state of flux. Many ironclads were built to make use of the ram or the torpedo, which a number of naval designers considered the crucial weapons of naval combat. There is no clear end to the ironclad period, but towards the end of the 1890s the term ironclad dropped out of use. New ships were increasingly constructed to a standard pattern and known as battleships, protected cruisers or armoured cruisers.
In turn the modern Dreadnought battleship appeared and alongside it the battlecruiser; the former protected by large amounts of armour which could protect it against all but guns of the largest calibre as found on other battleships, the latter carrying same size guns as a battleship but less armour in order to reach higher speeds.
Modern
The turn of the 20th century saw a development towards battleships, with large guns and copious armour. In previous eras, large caliber guns had been able to fire on the order of minutes, and were unwieldy to aim. But the development of powered aiming systems and ammunition hoists increased the rate of fire up to twice a minute, which combined with other developments, made battleships a finally useful force. The increasing calibers and muzzle velocity of guns required increasingly protective armor to stop projectiles. The development of new, more effective gunpowders also increased the length of guns, and the effective range of engagement. This meant that plunging fire became a serious concern, and lead to the strengthening of deck armor. Belt armor also became much thicker, surpassing on the largest battleships. One of the most heavily armored ships of all time, the Yamato-class battleship, had main belt of armour up to thick.The development of the torpedo and effective naval mines required further considerations for underwater armor, which had not been given much thought in prior eras. The World War era also saw the emergence of the armoured cruiser, which traded some armor in exchange for speed as compared to a battleship.
Since World War II, naval armour has been less important, due to the development of anti-ship guided missiles. Missiles can be highly accurate and penetrate even the thickest of armor. As a result, modern warships now focus more on anti-missile technology, damage control, and survivability instead of armor. However, most modern warships retain of partial armor to protect missiles and aircraft from splinters and light weapons fire.
Design
Belt armour
Belt armour is the main side armor on a warship.Armoured citadel
An armoured citadel is an armoured box enclosing the machinery and magazine spaces, formed by the armoured deck, the waterline belt, and the transverse bulkheads.Sloped armour
Simply sloping a piece of armour inherently increases its effectiveness by increasing the distance a projectile must travel to penetrate it. It also increases the odds that a projectile will ricochet off the target without causing damage.Torpedo bulkhead
A torpedo bulkhead is common on the more heavily armoured warships, especially battleships and battlecruisers of the early 20th century. It is designed to keep the ship afloat even if the hull was struck underneath the belt armour by a shell or by a torpedo.After the lessons learned during World War I, many capital ships were refitted with double, triple, or even quadruple torpedo bulkheads, as well as anti-torpedo bulges to the exterior of the hull. For example, the last US battleship designs during World War II had up to four torpedo bulkheads and a triple-bottom. The innermost bulkhead is commonly referred to as the holding bulkhead, and often this bulkhead would be manufactured from high tensile steel that could deform and absorb the pressure pulse from a torpedo hit without breaking. If the final bulkhead was at least 37 mm thick, it may also be referred to as an armoured bulkhead, as it would be capable of stopping splinters and shells with low striking velocities.
Torpedo belt
The torpedo belt was part of the armouring scheme in some warships 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. In theory this belt would absorb the explosions from torpedoes, or any naval artillery 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.
Torpedo bulge
Developed for use during the World Wars, an anti-torpedo bulge involves fitting partially water-filled compartmentalized sponsons on either side of a ship's hull, intended to detonate torpedoes, absorb their explosions, and contain flooding to damaged areas within the bulges.File:HMS_Glatton_in_drydock_IWM_SP_2083.jpg|alt=|thumb|HMS Glatton in drydock, circa 1914–1918, showing its anti-torpedo bulge
All or nothing
is a design choice in armouring warships, best known for its employment on Dreadnought battleships. The concept involves concentrating armour on areas most important to a ship while the rest of the ship receives significantly less armour. The "all or nothing" concept avoided light or moderate thicknesses of armour: armour was used in the greatest practicable thickness or not at all, thereby providing "either total or negligible protection". Compared to previous armouring systems, "all or nothing" ships had thicker armour covering a smaller proportion of the hull. The ironclad battleship launched in 1876 had featured a heavily armoured central citadel, with relatively unarmoured ends; however, by the era of, battleships were armoured over the length of the ship with varying zones of heavy, moderate or light armour. The U.S. Navy adopted what was formally called "all or nothing" armour in the Standard-type battleships, starting with the laid down in 1912. "All or nothing" armour was later adopted by other navies after the First World War, beginning with the Royal Navy in itsin combination with reducing the amount of ship that needed armouring by mounting all the main armament forward.