engineering

Reactive armour

Reactive armour is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Reactive armour rather than just read about it. In short: Reactive armour is a type of vehicle armour used for protecting vehicles, especially modern tanks, against anti-vehicle armour-piercing munitions. Reactive armour is most effective against shaped charges and hardened kinetic energy penetrators.

Key takeaways

Reactive armour belongs to engineering; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Reactive armour to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Reactive armour from memory before moving on to harder problems.

Reference excerpt

Reactive armour is a type of vehicle armour used for protecting vehicles, especially modern tanks, against anti-vehicle armour-piercing munitions. Reactive armour is most effective against shaped charges and hardened kinetic energy penetrators. When a shaped charge strikes the upper plate of the armour, it detonates the inner explosive, releasing blunt damage that the tank can absorb. 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. Reactive armour can be defeated with multiple hits in the same place, often achieved with tandem-charge weapons, which fire two or more shaped charges in rapid succession.

History

World War II Australia is the first recorded nation to have conceptualized and developed methods to disrupt and spread the jet of a hollow charge shell to reduce its penetrating power. In a June 1944 report from the Explosives Manufacturing Practices Laboratory of the Defence Explosive Factory Maribyrnong, an operational requirement was laid out for the defence against Japanese 75 mm hollow charge shells used against Allied tanks in the Pacific. The destructive effect of the shaped charge was identified as caused by a jet moving at high velocities, consisting of particles from the liner. The two methods developed were to destroy the jet by forcing it to act through a layer of explosives, disrupting the jet, and to make it act through a layer of oxidiser, destroying the jet by burning it with oxidising agents. The earliest trials were done with small charges able to defeat 2 inches of steel plate which were readily defeated by a layer of explosive (Baratol, R.D.X., Cordite, etc.) or a vigorous oxidising medium. Subsequent trials with British No.68 and American M9A1 grenades were carried out. Only a limited number of trials were conducted, causing varied results. A mixture of Sodium and Potassium Nitrates explosives was seen as the most practical option due to their casting properties. The mixture acted as an oxidiser which could explode when dispersed and heated. The Explosives Manufacturing Practices Laboratory settled on a combination of chemical armour and explosive reactive armour concepts to counter the hollow charge threat.

Cold War The idea of counterexplosion (kontrvzryv in Russian) in armour was proposed in the USSR by the Scientific Research Institute of Steel (NII Stali) in 1949 by academician Bogdan Vjacheslavovich Voitsekhovsky. The first pre-production models were produced during the 1960s. However, insufficient theoretical analysis during one of the tests resulted in all of the prototype elements being detonated. For a number of reasons, including the aforementioned accident and a belief that Soviet tanks had sufficient armour, the research was ended. No more research was conducted until 1974, when the Ministry of the Defensive Industry announced a contest to find the best tank protection. Picatinny Arsenal, an American military research facility, experimented with testing linear cutting charges against anti-tank ammunition in the 1950s. The researchers concluded that the charges may be effective with an adequate sensing and triggering mechanism but noted "tactical limitations"; the report was declassified in 1980. A West German researcher, Manfred Held, carried out similar work with the IDF in 1967–1969. Reactive armour created on the basis of the joint research was first installed on Israeli tanks during the 1982 Lebanon war and was judged very effective.

Explosive reactive armour

An element of explosive reactive armour (ERA) is made of either a sheet or slab of high explosive sandwiched between two metal plates, or multiple "banana shaped" rods filled with high explosive which are referred to as shaped charges. On attack by a penetrating weapon, the explosive detonates, forcibly driving the metal plates apart to damage the penetrator. The shaped charges, in contrast, each detonate individually, launching one spike-shaped plate each, meant to deflect, detonate or cut the incoming projectile. The disruption is attributed to two mechanisms. First, the moving plates change the effective velocity and angle of impact of the shaped charge jet, reducing the angle of incidence and increasing the effective jet velocity versus the plate element. Second, since the plates are angled compared to the usual impact direction of shaped charge warheads, as the plates move outwards the impact point on the plate moves over time, requiring the jet to cut through fresh plates of material. This second effect greatly increases the effective plate thickness during the impact.

To be effective against kinetic energy projectiles, ERA must use much thicker and heavier plates and a correspondingly thicker explosive layer. Such heavy ERA, such as the Soviet-developed Kontakt-5, can break apart a penetrating rod that is longer than the ERA is deep, again reducing penetration capability. Such ERA is ineffective against modern armour-piercing fin-stabilized discarding sabot (APFSDS) projectiles, however, due to their depleted uranium construction. An important aspect of ERA is the brisance, or detonation speed of its explosive element. A more brisant explosive and greater plate velocity will result in more plate material being fed into the path of the oncoming jet, greatly increasing the plate's effective thickness. This effect is especially pronounced in the rear plate receding away from the jet, which triples in effective thickness with double the velocity.

… excerpt ends here. Continue reading the full article.

Illustrations

The advanced Kontakt-5 explosive reactive armour on this T-90S is arranged in pairs of plates, giving the turret its prominent triangular profile.

Worked examples

Example 1 — a first encounter with Reactive armour

Start with the simplest possible case. Write down what Reactive armour claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Reactive armour before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Reactive armour ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Reactive armour

In research: Reactive armour appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Reactive armour in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Reactive armour is common in secondary-school and first-year university syllabi. It links to neighbouring topics Explosives engineering, Soviet inventions, Vehicle armour, so understanding it makes those chapters shorter.
In everyday life: Look for Reactive armour outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Reactive armour in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Reactive armour means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Reactive armour out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Reactive armour in simple terms?

Why does Reactive armour matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Reactive armour?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Reactive armour.