Active protection system

Lore & Background

Soft-kill measures are designed to defeat guided weapons either by concealing the protected vehicle from them, for example with a smoke screen, or by disrupting their guidance with radiation, such as with a dazzler. Some systems use laser dazzlers to blind the operator or sensors of semi-automatic command to line of sight (SACLOS) anti-tank guided missiles (ATGMs), such as the JD-3 of the Type 99 tank. Others use powerful infrared emitters to mask the IR tracking flare present on many SACLOS ATGMs, such as the Shtora-1. Soft-kill measures can be divided into on-board countermeasures, such as dazzlers, which are fixed to the platform, and expendable countermeasures, such as smoke grenades, which are ejected upon use. Soft-kill measures may be used preemptively, but are more commonly employed in reaction to detected threats.

Hard-kill measures kinetically attack threatening missiles or other munitions, usually at very close range to the protected vehicle. Explosively formed penetrators (EFPs) or high explosive fragmentation countermeasures are typically used. The exact mechanisms of many APS systems have not been published. The action of these countermeasures may lead to disturbance of the stability of a kinetic energy penetrator, premature initiation of a shaped charge, or destruction of the airframe of an inbound missile or shell. Examples include the Russian Arena system, which utilizes a Doppler radar to detect incoming threats and fires a munition to eliminate the threat, and the Israeli Trophy system, which fires a multiple explosively formed penetrator (MEFP) to destroy the threat.

Reader's Guide

Active protection systems represent a significant evolution in vehicle survivability, shifting from passive armor to active interception of incoming threats. The distinction between soft-kill and hard-kill measures allows for layered defense: soft-kill systems can confuse or blind guided missiles without physical engagement, while hard-kill systems physically destroy or disrupt projectiles. These systems address a range of threats, from anti-tank guided missiles to kinetic energy penetrators, though performance can be affected by radar clutter from mountains or neighboring vehicles. Top attack munitions, such as the FGM-148 Javelin, pose a particular challenge because not all APS are designed to fire at the extreme elevations necessary. The development of systems like Arena, Trophy, Quick Kill, and Iron Curtain illustrates diverse technical approaches, including Doppler radar, active electronically scanned arrays, and multiple sensors to reduce false alarms. The legacy of APS is ongoing, with many systems' exact mechanisms unpublished, reflecting both military secrecy and the rapid pace of countermeasure development.

Did You Know?

• Soft-kill measures can include smoke screens or laser dazzlers to blind SACLOS ATGM operators.
• The Russian Arena system uses a Doppler radar to detect incoming threats and fires a munition to eliminate them.
• The Israeli Trophy system fires a multiple explosively formed penetrator (MEFP) to destroy threats.
• Top attack ATGMs like the FGM-148 Javelin are not all countered by active protection systems due to extreme elevation requirements.

The Two Philosophies of Active Defense

Active protection systems represent a departure from traditional passive armor by actively engaging threats before they reach a vehicle. The field divides into two fundamentally different philosophies. Soft-kill measures work by deception or disruption: they either hide the vehicle from incoming guided weapons using smoke screens, or they jam the guidance systems with radiation. Laser dazzlers can blind the operators or sensors of semi-automatic command to line-of-sight missiles, while powerful infrared emitters can mask the tracking flares that many such missiles rely on. These countermeasures split further into fixed on-board devices like dazzlers and expendable items like smoke grenades that are ejected upon use. Hard-kill measures take the opposite approach: they physically strike the incoming threat to damage or destroy it, thereby limiting its ability to penetrate armor. This binary framework—deceive versus destroy—underpins every APS design in the world.

The Physics of Hard-Kill Interception

Hard-kill active protection systems operate on a simple but violent principle: intercept the threat at very close range using kinetic force. The most common tools are explosively formed penetrators and high-explosive fragmentation countermeasures, though the precise internal mechanisms of many systems remain unpublished. When these countermeasures engage a threat, several destructive effects can occur. A kinetic energy penetrator may have its stability disturbed, reducing its penetration capability as the deflection angle grows. A shaped charge weapon may suffer premature or improper initiation, which impairs the development of the copper jet that provides most of its anti-armor power. In the most direct case, the airframe of an inbound missile or shell is simply destroyed. Systems like Russia's Arena use Doppler radar to detect and fire a munition, Israel's Trophy launches a multiple explosively formed penetrator, and the American Iron Curtain fires a kinetic countermeasure designed to minimize collateral damage while defeating threats mere inches from impact.

A Global Arms Race in APS Development

Active protection systems have become a marker of national defense ambition, with numerous countries pursuing both hard-kill and soft-kill programs. In the hard-kill category, China fields the GL5 and GL6, France has developed DIAMANT and SPATEM, and Germany offers StrikeShield. Israel's Iron Fist and Trophy systems are well known, while Russia contributes Arena, Drozd, and the Afganit system mounted on Armata armored fighting vehicles. South Africa and Sweden collaborate on LEDS-150, South Korea has KAPS, Turkey fields the Aselsan AKKOR and its PULAT variant, and Ukraine has developed Zaslin. The United States pursues both Quick Kill, which uses an Active Electronically Scanned Array to assess threats and deploy a smaller rocket countermeasure, and Iron Curtain, which employs two sensors to reduce false alarms. On the soft-kill side, nations including Germany, Poland, Russia, South Korea, Syria, Turkey, Ukraine, and the United States all maintain programs, ranging from Russia's Shtora-1 to the American AN/VLQ-6 MCD.

Operational Limitations and Vulnerabilities

Despite their sophistication, active protection systems face significant operational challenges that limit their effectiveness in real-world combat environments. One major issue is radar clutter: mountains and neighboring vehicles reflect radio waves, creating noise that degrades both radar detection and radar-lock performance. This is particularly problematic for systems like Russia's Arena, which relies on Doppler radar, or the Afganit system, which uses millimeter-wavelength radar to track incoming anti-tank munitions. A second critical vulnerability involves top-attack munitions. Weapons such as the American FGM-148 Javelin and Germany's Trigat plunge down onto targets from steep angles, and not all APS are designed to fire at the extreme elevations required to intercept them. Similarly, rocket-propelled grenades launched from elevated positions at steep downward angles can exploit the same blind spot. These limitations mean that even the most advanced APS cannot guarantee complete protection, and operators must still rely on situational awareness and tactical positioning.