First, the threat: KE vs CE

Tank armor is designed against two threat categories:

  • Kinetic Energy (KE) penetrators — APFSDS (Armor-Piercing Fin-Stabilized Discarding Sabot) rounds. A dense tungsten or depleted-uranium rod fired at 1,700+ m/s. One principle: velocity × mass ÷ surface area = penetration.
  • Chemical Energy (CE) warheads — HEAT (High Explosive Anti-Tank) and HESH. HEAT uses the Munroe effect: a copper liner cone explodes inward and produces a hypervelocity metal jet. It relies on geometry, not on velocity.

The two threats need very different countermeasures. Armor that's good against KE can be bad against HEAT. Modern armor's job is to be good enough against both.

1st generation — RHA (Rolled Homogeneous Armor)

Standard for tanks from 1916-1960: rolled homogeneous steel plate. Measured in millimeters and used as the reference for every other armor type (e.g. "this composite gives 300 mm RHA equivalent protection").

RHA has two numbers:

  • Physical thickness — actual mm.
  • Slope multiplier — at 60°, a 100 mm plate gives close to the protection of a vertical 200 mm plate. This is exactly the T-34's revolution (see the T-34 article).
Chobham composite armor — layered cutaway
  1. 1Outer RHA steel shell
  2. 2Ceramic tiles (alumina / B₄C)
  3. 3Composite matrix layer
  4. 4Resin bond + spall liner
  5. 5Inner RHA steel plate

2nd generation — Composite (Chobham)

Developed in the early 1970s by the British RARDE (Royal Armament Research and Development Establishment), Chobham armor is a three-layer sandwich:

  • Outer steel shell — deforms the tip of a KE penetrator.
  • Ceramic middle layer (alumina, boron carbide) — breaks up HEAT jets and erodes KE penetrators.
  • Resin + inner steel plate — catches the debris.

Result: at the same weight, 3-5x the KE protection and 5-10x the HEAT protection of RHA. Chobham is the real weapon of the M1 Abrams, Leopard 2 and Challenger 1/2.

Kontakt-5 ERA — exploded diagram
  1. 1Outer steel plate (flies out)
  2. 2Explosive layer
  3. 3Inner steel plate
  4. 4HEAT jet trigger point
  5. 5Plate launched at 100+ m/s
  6. 6Mounting bracket (to hull)

3rd generation — ERA and NERA (reactive armor)

The Soviet answer: ERA (Explosive Reactive Armor). A flat explosive layer sandwiched between two thin steel plates. An incoming HEAT jet triggers the outer plate, which is launched outward at 100+ m/s; that motion disrupts the jet.

  • Kontakt-1 (1985, T-80U) — effective against HEAT only.
  • Kontakt-5 (1988) — also effective against KE (bends the penetrator).
  • Relikt (2006, T-90M) — resists even tandem HEAT.

NERA (Non-Explosive Reactive Armor) applies the same principle with rubber or inert material instead of explosives — less protection, but re-triggerable and safe for nearby infantry. Often found on the side packages of modern Western MBTs.

Trophy APS — radar + intercept
  1. 1AESA radar panel (4 quadrants)
  2. 2MEFP interceptor launchers
  3. 3Detection cone (360°)
  4. 4Incoming RPG / ATGM
  5. 5Intercept point (~5 m out)
  6. 6Host MBT (Merkava / Abrams)

4th generation — Active Protection Systems (APS)

No matter how good passive armor gets, weight is a hard ceiling. The solution: destroy the round before it hits the tank.

  • Soft-kill APS — deceives a guided missile (especially laser-guided). Smoke grenades, laser dazzlers, IR jammers. Russia's Shtora-1 (1989) was the pioneer.
  • Hard-kill APS — physically destroys the incoming round. Radar detection, ballistic calculation, counter-projectile launched within milliseconds. Trophy(Israel, Rafael) is the category standard. Iron Fist (IMI) and AFGANIT (Russia, T-14) are alternatives.

Trophy has been operational on Merkava IVs since 2011 and on M1A2 SEPv3 Abrams since 2018. Dozens of RPG and ATGM intercepts have been documented in Gaza and Lebanon.

Top-attack threats

A tank's thinnest armor is always on top. Modern top-attack ATGMs (Javelin, NLAW, Spike) use pop-up trajectories to hit there. The 2022-2024 Ukraine war showed FPV drones with $500 explosives can disable $5M T-90Ms.

Designers are answering in three directions:

  • Cope cage — improvised cage structure over the turret.
  • Top-attack APS — upward-pointed radar variants like Trophy MV and Iron Fist Light Decoupled.
  • AI-assisted target priority — the FCS auto-prioritizing incoming top-down drones.

The future: electromagnetic and self-healing

  • Electric armor — high-voltage capacitor converts the penetrator to plasma. ARL and BAE Systems have built prototypes; weight + power are unsolved.
  • Self-healing composite — DARPA-backed projects use microencapsulated resins to auto-repair small damage.
  • Electromagnetic coil armor — magnetic deflection of a KE penetrator. Still lab stage.

Summary — the four layers of tank protection

  1. See — early threat detection (radar, IR, ML target ID).
  2. Deflect — soft-kill APS, smoke, jammers.
  3. Destroy — hard-kill APS counter-projectiles.
  4. Absorb — layered passive armor: composite + ERA + RHA.

A modern MBT runs all four at once. It doesn't make the tank invincible — it makes killing it much harder and much more expensive.

If you want to feel this layered defense in a game, in TANK//LOCK you have to manage sonar + decoy + armor + lock-on simultaneously.