Vehicle armour
From Freepedia
Military vehicles are commonly armoured to withstand the impact of shrapnel, bullets or shells, protecting the soldiers inside from enemy fire. 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.
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 function as additional back-up armour to protect the crew. Outer armor is modular and enables quick replacement of damaged armour.
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Technologies
Sloping and curving armour both increase the effective thickness, as a projectile striking at an angle must cut through more armour than one impacting perpendicularly. They also increase the chance of deflecting projectiles. The sloping front armour of a tank is often called the glacis, and provides the best protection as it is assumed to be the easiest part of the tank to hit. It is also made the thickest because the tank is usually considered an inherently offensive weapon, and it has been assumed by designers since before the Second World War that a tank will be moving directly towards the enemy almost all the time; even on the defensive, a tank will be deployed in such a way as to have the glacis oriented in the direction from which the enemy is expected to attack.
Appliqué armour screens have sometimes been bolted on to armoured vehicles to increase protection.
Recently, many manufacturers have added a spall liner to the inside of the armour, which is designed to absorb fragmentation (spallation) released from the impact of an enemy shell, protecting soldiers and equipment inside. They tend to be made from kevlar or similar materials.
Spaced armour
Spaced armour, already used in WWI on the Schneider CA1 and St Chamond to defeat bullets, but reintroduced in the 1960s on the German Leopard 1, uses the fact that a shaped charge makes a jet of plasticised metal that dissipates after it travels a metre or two. There are hollow spaces inside the armour, increasing the length of travel from the exterior of the vehicle to the interior, in hopes of reducing the shaped charge's penetrating power; in some cases 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. Thus instead of having a single 30cm layer of steel armour, it is possible to have two 15 cm layers half a metre or more apart, giving far greater protection against shaped charges at no penalty in weight.
The Whipple shield uses the principle of spaced armour to protect spacecraft from the impacts of micrometeoroids.
Composite armour
- Main article: Composite armour
Composite armour (including Chobham armour) was developed in the 1960s by the British and first used on the American M1 Abrams but not, as is often presumed, on the German Leopard 2. It consists of layers of steel, ceramic, and plastic honeycomb, sometimes with layers of depleted uranium added. Composite is effective against both kinetic and shaped charge munitions. Against kinetic penetrators, the brittle ceramic blunts the projectile while the softer steel layers absorb its kinetic energy. Still, it is significantly less effective against KE-munitions, so sometimes depleted uranium layers are added to provide extra protection against these warheads.
An alternate description of Chobham armour is that it combines spaced armour with composites. Supposedly the deeper interior heavy metal layer is a cast aluminium slab with rods of tungsten (encased in titanium) or depleted uranium running perpendicularly through it, intended to cause the points of high-velocity long-rod penetrator armour-piercing projectiles to deform, which sometimes causes the projectile to tip and strike the armour at an angle, presenting far greater surface area to the armour and therefore greatly increasing the resistance.
Another type is perforated steel—armour with hollow perpendicular spaces serving the same function that they do in spaced armour, often filled with ceramic foam and backed by layers of Kevlar or similar material to trap and reduce fragmentation. This is the type used in the original version of the Leopard 2.
Reactive armour
- Main article: Reactive armour
Explosive reactive armour, initially developed by 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 charge's plasma flow. It is less effective against kinetic penetrators. Reactive armour poses a threat to friendly troops in the area of the vehicle.
Electrically charged armour
A recent development in the UK is that of electrically charged armour. A vehicle is fitted with two thin shells. The outer shell of the vehicle contains an enormous electric charge, the inner shell is a ground. The shells are separate. When an incoming HEAT plasma-jet arrives, it penetrates the outer shell and in doing so forms a bridge between the outer shell and the inner shell. The enormous electric charge in the outer shell discharges through the jet and disrupts it. Trials have so far been extremely promising. Currently the developers of the Future Combat Systems series of armoured vehicles are looking at this technology.
