Vehicle armour

For body armour see armour, for armoured forces see armoured, for other uses see armour (disambiguation).

Military vehicles are commonly armoured to withstand the impact of shrapnel, bullets, missiles, or shells, protecting the personnel inside from enemy fire. Such vehicles include tanks, aircraft, and ships.

Civilian vehicles may also be armoured. These vehicles include cars used by reporters, officials and others in conflict zones or where violent crime is common, and presidential limousines. Armoured cars are also routinely used by security firms to carry money or valuables to reduce the risk of highway robbery or the hijacking of the cargo.

Armour may also be used in vehicles from threats other than deliberate attack. Some spacecraft are equipped with specialised armour to protect them against impacts from tiny meteors or fragments of space junk. Even normal civilian aircraft may carry armour in the form of debris containment walls built into the casing of their gas turbines to prevent injuries or airframe damage should the compressor/turbine wheel disintegrate.

The design and purpose of the vehicle determines the amount of armour plating carried, as the plating is often very heavy and excessive amounts of armour restrict mobility.

Vehicle armour is sometimes improvised in the midst of an armed conflict. In World War II, U.S. tank crews welded spare strips of tank track to the hulls of their Sherman, Grant, and Stuart tanks. In the Vietnam War, U.S. "gun trucks" were armoured with sandbags and locally fabricated steel armour plate. More recently, U.S. troops in Iraq armoured Humvees and various military transport vehicles with scrap materials: this came to be known as "haji" armour by Iraqis and "hillbilly" armor by the Americans.

Armoured Fighting Vehicles

The most heavily armoured vehicles today are the main battle tanks, which are the spearhead of the ground forces, and are designed to withstand anti-tank missiles, kinetic energy penetrators, NBC threats and in some tanks even steep-trajectory shells. The Israeli Merkava tanks were designed in a way that each tank component functions as additional back-up armour to protect the crew. Outer armour is modular and enables quick replacement of damaged armour.

Technologies

For efficiency, the heaviest armour on an AFV (armoured fighting vehicle) is placed on its front. Tank tactics require the vehicle to always face the likely direction of enemy fire as much as possible, even in defence or withdrawal operations.

Sloping and curving armour can both increase its protection. Given a fixed thickness of armour plate, a projectile striking at an angle must penetrate more armour than one impacting perpendicularly. An angled surface also increases the chance of deflecting a projectile. This can be seen on v-hull designs, which direct the force of an IED or landmine away from the crew compartment, increasing crew survivability.

Appliqué armour screens have sometimes been bolted or welded onto armoured vehicles to increase protection.

Beginning during the Cold War, many AFVs have spall liners inside of the armour, designed to protect crew and equipment inside from fragmentation (spalling) released from the impact of enemy shells, especially high explosive squash head warheads. Spall liners are made of Kevlar, Dyneema or similar materials.

Spaced armour

Armour with two or more plates spaced a distance apart, called spaced armour, when sloped reduces the penetrating power of bullets and solid shot as after penetrating each plate they tend to tumble, deflect, deform, or disintegrate, when not sloped reduces the protection offered by the armour, and detonates explosive projectiles before they reach the inner plates. It has been in use since the First World War, where it was used on the Schneider CA1 and St Chamond tanks. Many early-WWII German tanks had spaced armour in the form of armoured skirts, to make their thinner side armour more effective against anti-tank fire.

File:T34 85 4.jpg

Soviet T-34-85 with anti-Panzerfaust screens of wire mesh, protecting side and top armour during street fighting, Berlin, May 1945.

The principle of spaced armour protects against high explosive anti-tank (HEAT) projectiles which create a focussed jet of plasticised metal, very effective at the focus point, but much less so beyond there. Relatively thin armour plates or even metal mesh, much lighter than fully protective armour, can be attached as side skirts or turret skirts on tanks and other armoured vehicles. This light armour detonates the warhead prematurely so that the jet of molten metal is focussed well before the main armour, becoming relatively ineffective. Factory-made and improvised stand-off armour was introduced in the Second World War to defend against the new Bazooka, Panzerfaust, and other HEAT weapons.

In response to increasingly effective HEAT warheads, integral spaced armour was reintroduced in the 1960s on the German Leopard 1. There are hollow spaces inside this type of armour, increasing the length of travel from the exterior of the vehicle to the interior for a given weight of armour, to reduce the shaped charge's penetrating power. Sometimes the interior surfaces of these hollow cavities are sloped, presenting angles to the anticipated path of the shaped charge's jet in order to further dissipate its power. For example, a given weight of armour can be distributed in 2 layers 15cm (6in) thick instead of a single 30cm (12in) layer, giving much better protection against shaped charges.

Today light armoured vehicles mount panels of metal rods, known as slat armour or cage armor, and some main battle tanks carry rubber skirts to protect their relatively fragile suspension and front belly armour.

The Whipple shield uses the principle of spaced armour to protect spacecraft from the impacts of very fast micrometeoroids. The impact with the first wall melts or breaks up the incoming particle, causing fragments to be spread over a wider area when striking the subsequent walls.

Composite armour

Main article: Composite armour

Composite armour is armour consisting of layers of two or more materials with significantly different chemical properties; steel and ceramics are the most common types of material in composite armour. Composite armour was initially developed in the 1940s, although it did not enter service until much later and the early examples are often ignored in the face of newer armour such as Chobham armour. Composite armour's effectiveness depends on its composition and may be effective against kinetic energy penetrators as well as shaped charge munitions; heavy metals are sometimes included specifically for protection from kinetic energy penetrators.

Reactive armour

Main article: Reactive armour

Explosive reactive armour, initially developed by German researcher, Manfred Held working in Israel, uses layers of high explosive sandwiched between steel plates. When a shaped-charge warhead hits, the explosive detonates and pushes the steel plates into the warhead, disrupting the flow of the charge's liquid metal penetrator (usually copper at around 500 degrees; it can be made to flow like water by sufficient pressure). It is less effective against kinetic penetrators. Reactive armour poses a threat to friendly troops near the vehicle.

Non-explosive reactive armour is an advanced spaced armour which uses materials which change their geometry so as to increase protection under the stress of impact.

Active protection systems use a sensor to detect an incoming projectile and explosively launch a counter-projectile into its path.

Electrically charged armour

Electrically charged armour is a recent development in the UK by the Defence Science and Technology Laboratory. A vehicle is fitted with two thin shells, separated by insulating material. The outer shell holds an enormous electrical charge, while the inner shell is a ground. If an incoming HEAT jet penetrates the outer shell and forms a bridge between the shells, the electrical energy discharges through the jet, disrupting it. Trials have so far been extremely promising, and it is hoped that improved systems could protect against KE penetrators. Developers of the Future Rapid Effect System (FRES) series of armoured vehicles are considering this technology.

See also

• Active protection system
• Armoured fighting vehicle
• Armoured forces
• Body armour
• Plastic armour
• Tank classification

External links

• Electrically charged armour