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Armour with two or more plates spaced a distance apart falls under the category of spaced armour. Spaced armour can be sloped or unsloped. When sloped, it reduces the penetrating power of bullets and solid shot, as after penetrating each plate projectiles tend to tumble, deflect, deform, or disintegrate; spaced armour that is not sloped is generally designed to provide protection from explosive projectiles, which detonate before reaching the primary armour. Spaced armour is used on military vehicles such as tanks and combat bulldozers. In a less common application, it is used in some spacecraft that use Whipple shields.
Tank spaced armour has been fielded since the First World War, when it was fitted to the French Schneider CA1 and Saint-Chamond tanks. The late variants of Panzer III had frontal spaced armour: a 20 mm thick face-hardened steel layer in front of the 50 mm thick main armour. Impacted projectiles were physically damaged by the 20mm plate, so the main armour could withstand much greater hits.[ citation needed ] Due to lack of materials, German industry eventually switched to Rolled Homogeneous Armour (RHA), which is less effective and due to the slower production process, the technique was not widespread on German tanks.
Many World War II-era German tanks used armoured skirts (Schürzen) to make their thinner side-armour more resistant to anti-tank rifles, contrary to popular belief that the German Schürzen were designed against shaped charge projectiles. [1] [2] The common Russian PTRS rifles could penetrate 35-40mm of armor at common combat ranges, whereas many German tanks only had 30mm of armor on their sides. The skirts thus added 8mm of additional thickness to make up the difference, and could theoretically cause the round to tumble, improving protection against those weapons. Nevertheless these rifles continued to be useful throughout the war. [3]
Postwar analysis of spaced armour at the US Aberdeen Proving Grounds found spaced armour to be ineffective if the layers are of roughly equal thickness. Numerous trials invariably showed that combinations of multiple plates provided "considerably less protection than a single solid plate of the same total thickness". This is because the midsection of plates provides more resistance to penetration than the front and rear surfaces, and thus having a thicker plate offers better performance. Instead additional layers of armour should be the thinnest required to obtain the possibility of fracturing the projectile, which has the best results in improving protection, though this effect was not consistent and could be mitigated by improved projectile design. Projectiles impacting against sloped spaced armour at greater standoff ranges could also result in the projectile turning to impact the second plate at a more perpendicular angle, making the added armour worse than nothing. [4] This is because a projectile penetrating a plate is deflected towards the normal, an effect that could ruin an armour scheme. [5]
Though spaced armour appeared in some tanks like the Leopard 1 and the Merkava, the armour scheme was not considered to offer sufficiently better protection against armour-piercing projectiles to justify the increased complication they posed, and thus their use on post-war tanks was limited and eventually superseded by more effective composite armour. [6]
Most of the Cold War spaced armour was designed against medium-to-low caliber kinetic munitions, (e.g. 30mm autocannon and 76mm HESH rounds), especially vehicle side skirts. Most of them were made of RHA plates (Centurion), or thick reinforced rubbers (T-72), and worked in the same way as did WW2-era ones. Some WWII armoured vehicles used nets of wooden logs at a certain distance from the hull as makeshift spaced armour to protect the vehicle from magnetic mines, thrown shaped charges and grenades, and occasionally suicidal methods (e.g. the Japanese lunge mine). This method occurred on US M4 Sherman and Soviet T-34 medium tanks among others.
The idea is that this thin layer of armour detonates explosive warheads prematurely. Such techniques were effective in warships against armour piercing shells with short fuzes. [5] High-explosive anti-tank-type warheads (HEAT) however use a focused hypervelocity jet of copper or steel to penetrate armour. To be effective, HEAT warheads must detonate at a specific distance from the target's primary armour to ensure maximum penetration. Early detonation may reduce the penetration of HEAT ammunition, but it may in fact improve penetration if the round was originally detonating too close to the armour. Due to constraints in the length of projectiles, many designs intentionally detonate closer than the optimum distance, with optimal penetration requiring a standoff distance of over a meter for many early projectiles. Thus conventional skirts are ineffective against HEAT. [7] [8] [4]
To increase effectiveness of skirts against HEAT weapons early T-64s had "gill" skirts. It contained a few short skirts on the side of the vehicle which are opened in open terrain at an angle of between 30–45°, increasing the space between the armour and the plate. It was effective (mass-to-efficiency ratio), but easily detached from the vehicle so it did not spread widely.[ citation needed ]
Military researchers tried to increase the efficiency of armour by changing the used materials and varying the armour layout, leading to more complex composite armour, which can incorporate empty spaces.
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.
A rocket-propelled grenade (RPG) is a shoulder-fired rocket weapon that launches rockets equipped with an explosive warhead. Most RPGs can be carried by an individual soldier, and are frequently used as anti-tank weapons. These warheads are affixed to a rocket motor which propels the RPG towards the target and they are stabilized in flight with fins. Some types of RPG are reloadable with new rocket-propelled grenades, while others are single-use. RPGs are generally loaded from the front.
A shaped charge is an explosive charge shaped to focus the effect of the explosive's energy. Different types of shaped charges are used for various purposes such as cutting and forming metal, initiating nuclear weapons, penetrating armor, or perforating wells in the oil and gas industry.
Reactive armour is a type of vehicle armour used in protecting vehicles, especially modern tanks, against shaped charges and hardened kinetic energy penetrators. The most common type is explosive reactive armour (ERA), but variants include self-limiting explosive reactive armour (SLERA), non-energetic reactive armour (NERA), non-explosive reactive armour (NxRA), and electric armour. NERA and NxRA modules can withstand multiple hits, unlike ERA and SLERA.
Armour-piercing ammunition (AP) is a type of projectile designed to penetrate armour protection, most often including naval armour, body armour, and vehicle armour.
Composite armour is a type of vehicle armour consisting of layers of different materials such as metals, plastics, ceramics or air. Most composite armours are lighter than their all-metal equivalent, but instead occupy a larger volume for the same resistance to penetration. It is possible to design composite armour stronger, lighter and less voluminous than traditional armour, but the cost is often prohibitively high, restricting its use to especially vulnerable parts of a vehicle. Its primary purpose is to help defeat high-explosive anti-tank (HEAT) projectiles.
Terminal ballistics is a sub-field of ballistics concerned with the behavior and effects of a projectile when it hits and transfers its energy to a target.
Chobham armour is the informal name of a composite armour developed in the 1960s at the Military Vehicles and Engineering Establishment, a British tank research centre on Chobham Lane in Chertsey. The name has since become the common generic term for composite ceramic vehicle armour. Other names informally given to Chobham armour include Burlington and Dorchester. Special armour is a broader informal term referring to any armour arrangement comprising sandwich reactive plates, including Chobham armour.
A high-explosive squash head (HESH), in British terminology, or a high-explosive plastic/plasticized (HEP), in American terminology, is a type of explosive projectile with plastic explosive that conforms to the surface of a target before detonating, which improves the transfer of explosive energy to the target. Squash head projectiles are similar to high-explosive projectiles and are well suited to many of the same targets. However, while HESH projectiles are not armour-piercing, they can defeat armored targets by causing spall, which can injure or kill a vehicle's occupants or detonate some types of ammunition.
High-explosive anti-tank (HEAT) is the effect of a shaped charge explosive that uses the Munroe effect to penetrate heavy armor. The warhead functions by having an explosive charge collapse a metal liner inside the warhead into a high-velocity shaped charge jet; this is capable of penetrating armor steel to a depth of seven or more times the diameter of the charge. The shaped charge jet armor penetration effect is purely kinetic in nature; the round has no explosive or incendiary effect on the armor.
Kontakt-5 is a type of second-generation explosive reactive armour (ERA) originating in the Soviet Union. Due to the shortcomings of Kontakt-1, NII Stali further developed the reactive armor to Kontakt-5, so that it also repels APFSDS projectiles, which is not as effective in combat as stated. In addition, Kontakt-5 is not just additional armor, but is clearly integrated into the vehicle hull. The Kontakt-5 modules have a significantly thicker steel upper side. Depending on the module, they contain one or two 4S22 reactive elements. The explosive of a 4S22 element has the TNT equivalent of 330 g. It is so sensitive that even armor-piercing projectiles cause it to explode. Kontakt-5 produces a stronger defensive detonation than Kontakt-1 and the thicker layer of steel thrown at the arrow projectile breaks or bends it. The increase in defensive capability led to the development of reinforced arrow projectiles.
Rolled homogeneous armour (RHA) is a type of vehicle armour made of a single steel composition hot-rolled to improve its material characteristics, as opposed to layered or cemented armour. Its first common application was in tanks. After World War II, it began to fall out of use on main battle tanks and other armoured fighting vehicles intended to see front-line combat as new anti-tank weapon technologies were developed which were capable of relatively easily penetrating rolled homogeneous armour plating even of significant thickness.
Sloped armour is armour that is oriented neither vertically nor horizontally. Such angled armour is typically mounted on tanks and other armoured fighting vehicles (AFVs), as well as naval vessels such as battleships and cruisers. Sloping an armour plate makes it more difficult to penetrate by anti-tank weapons, such as armour-piercing shells, kinetic energy penetrators and rockets, if they follow a more or less horizontal trajectory to their target, as is often the case. The improved protection is caused by three main effects.
A tandem-charge or dual-charge weapon is an explosive device or projectile that has two or more stages of detonation, assisting it to penetrate either reactive armour on an armoured vehicle or strong structures.
Military vehicles are commonly armoured to withstand the impact of shrapnel, bullets, shells, rockets, and missiles, protecting the personnel inside from enemy fire. Such vehicles include armoured fighting vehicles like tanks, aircraft, and ships.
Belt armor is a layer of heavy metal armor plated onto or within the outer hulls of warships, typically on battleships, battlecruisers and cruisers, and aircraft carriers.
Slat armor, also known as bar armor, cage armor, and standoff armor, is a type of vehicle armor designed to protect against high-explosive anti-tank (HEAT) attacks, as used by anti-tank guided missiles (ATGMs) and rocket-propelled grenades (RPGs).
Beyond-armour effect is a term coined by Försvarets Fabriksverk (FFV), a semi-governmental Swedish defense firm, while developing the AT4 anti-tank weapon. From the 1980s, this phrase was used in its brochures, press releases, weapon instruction manuals and other documentation to denote the post-penetration effect of the AT4's HEAT anti-armour warhead against the interior and occupants of armoured vehicles.
The Kanchan Armour is the name informally given to a modular composite armour developed by India. The armour got its name from Kanchan Bagh, Hyderabad, Telangana, where the Defence Metallurgical Research Laboratory (DMRL) is located.
The Modular Expandable Armor System (MEXAS) is a composite armour system developed by the German company IBD Deisenroth Engineering. MEXAS was introduced in 1994 and has been applied on over 20,000 combat vehicles worldwide. The successor of MEXAS is the Advanced Modular Armor Protection (AMAP).
Stillbrew armour, or more correctly, the Stillbrew Crew Protection Package (SCPP) was an add-on passive composite armour applied to the FV4201 Chieftain main battle tank used by the British Army's Royal Armoured Corps in the mid-1980s and early-1990s so as to provide increased protection from anti-tank warfare weapons. It was named after the two men that invented it, Colonel Still and John Brewer, from the Military Vehicles and Engineering Establishment in Surrey. The tanks to which it was fitted were colloquially referred to as Stillbrew Chieftains.