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Don't touch me!

Traditional armour--and one can now consider that explosive reactive armour has become a traditional type--has reached its limits against the current performance of anti-armour warheads. The Russians, more particularly, have been very active in finding solutions following some pretty dramatic experiences in Chechnya. One has to admit that they have pioneered the development of active defences.

Active protection systems are intended to detect incoming anti-tank rounds or missiles, then engage these in their final moments of flight by firing some form of counter-munition. They are intended to provide protection to armoured vehicles that equals or exceeds that of traditional armour, but at a fraction of the weight.

The first active-armour system to enter service was the Russian Drozd, which was fielded in the late 1980's. As originally fielded, The Drozd provided only a 60-degree frontal protection, but the follow-on Arena E system from Konstruktorskoye Byuro Mashinostroyenia, better know as KBM, provides all-round protection against both direct-fire and top-attack guided or unguided missiles.

In the Arena E system, a multi-function millimetre-wave radar detects the incoming threat and triggers one of an array of protective ammunitions housed in silos arranged around the turret. This counter-munition detonates a few meters ahead of the target, generating a directed field of fragments. The Arena E covers an arc of 135 degrees left and right of the turret from the centreline, in other words, a total arc of 270 degrees. Having the silo crown on the turret rather than around the vehicle offers the advantage of redundancy in the (improbable) event of a double attack against the very same spot on the vehicle. Indeed should protection in a given arc been used, the turret can be trained a few degrees to bring a fresh counter-warhead in line with the incoming threat. Needless to say given the extremely short reactions required (0.07 second), the system is fully automated. While the Arena E is able to deal a death blow to all manner of unguided rockets and missiles--including top attack types like the Bill 2 and oblique attack types like the Javelin or the Gill--it cannot cut the way to almost vertically-fired explosively forged projectile warheads such as the Franco-Swedish Bonus or the German Smart. However, the system could usefully and relatively easily be redesigned to protect air-defence aerials against anti-radiation missiles.

A typical Arena E weighs approximately 1000 kilograms and can thus be mounted on the larger light armoured vehicle types.

The Arena E counter-munition is launched on a rising trajectory and detonates above its target; its destructive fragments thus strike the shaped-charge warhead at a high angle, so impact mostly on the outer part of the charge. Other systems under development fire their splinters ahead of the incoming threat, so will damage both the cavity and the liner of the shaped charge.

Tests conducted by the French German Research Institute of Saint-Louis have assessed the effects of fragmentation attacks on shaped charges. Impacts close to the liner region caused test warheads to lose more than 70 per cent of their penetration power. Fragment trajectories which do not cross the liner or which just touch the basis of the liner reduce performance by less than 60 per cent.

Shaped charges are sensitive to perturbation during the jet formation phase. Small objects placed in the liner cavity often have little effect on the jet tip velocity, but have dramatic effects on the jet quality. Tests conducted by the Swiss Defence Procurement Agency have shown that the most efficient way to destroy the shaped charge effect is to introduce some low-density material with embedded metallic spheres into the cavity of the shaped charge. The jet-formation process is completely perturbed; the charge only produces a cloud of liner material fragments having no penetration capability against a steel target.

As a matter of fact, the problem of the deterioration of the shaped charge effect is now being seriously investigated by some manufacturers as it has been clearly established that there is an interaction between the front and rear charges in tandem-charge warheads, the shock wave of the first disturbing the effect of the second.

The Ukrainian Ukrinmash organisation is now marketing the new Zaslon active defence system, which is intended to protect stationary and mobile vehicles from all types of anti-tank weapons, including those using diving trajectories.

It consists of a threat-detection radar, control panel, and a number of defensive modules which detonate to destroy an incoming threat.

The radar sensor offers coverage of plus or minus 150 to 180 degrees in azimuth and from -6 to +20 degrees in elevation. The counter-munition modules can deal with threats flying at speeds from 70 to more than 1200 m/sec.

Total system weight depends on protection level required and is typically between 50 and 130 kg. Power consumption is a maximum of 200 Watts.

The US Army Tank-Automotive Research, Development, and Engineering Center (Tardec) leads the Army Active Protection Program, with technology development efforts provided by the US Army Research Laboratory (ARL), the US Army Armament Research, Development, and Engineering Center (Ardec) and industry.

The problems to defeating chemical energy threats (also referred to as CE), such as anti-tank missiles and RPG projectiles, are eclipsed by the challenges of detecting kinetic energy threats. These are high-speed threats, so must be detected at longer ranges than chemical energy weapons, and tracked at higher data rates. They may have to be intercepted closer to the vehicle, and any impact of their remains must be handled by the vehicle's conventional armour. Advanced concepts featuring lightweight high-strength materials are being investigated to deal with this debris-defeat problem.

A passive infrared tracking sensor has already demonstrated the ability to accurately track kinetic projectiles at range rates and data rates at or near the programme requirements, says the Army Research Laboratory. Subscale experiments with momentum transfer armour, radial shaped-charge warhead and multiple EFP warhead counter-munitions have demonstrated the technology needed to intercept kinetic threats. In addition to counter-munitions, active-protection systems will also use jammers, decoys, and traditional obscurants.

In August 2003, United Defense announced that a combat vehicle fitted with an Integrated Army Active Protection System (Iaaps) had defeated live threats while travelling at 20 miles per hour. During the test, the Iaaps successfully defended the moving vehicle against live anti-tank guided missiles by using a combination of a Northrop Grumman 'hard kill' active-protection system and a BAE Systems 'soft kill' electronic jammer able to handle more than one threat concurrently.

The trial followed twelve months of successful stationary Iaaps testing in which the system had repeatedly defeated a wide range of threats. It successfully stopped the threats, and sustained no damage, while demonstrating both a self-defence capability and the ability to provide a limited degree of area protection that could be used to defend nearby vehicles. In the spring of 2003, it demonstrated the first simultaneous defeat of two live threats.

The Iaaps shows the technological feasibility of equipping Future Combat System vehicles with an integrated self-defence suite of sensors, processors and countermeasures. <<The survivability of 20-tonne Future Combat System vehicle platforms will be highly reliant on active protection, combined with advanced lightweight armour, to defeat the most lethal anti-armour threats,>> says Mark Middione, the Iaaps programme manager at United Defense. <<Our successful stationary and on-the-move Iaaps test results continue to place the system on track for FCS increment 1.>>

The Iaaps programme is being conducted as a US Army Tacom Integrated Army Active Protection Science and Technology Objective. It will continue through fiscal year 2005 and will demonstrate the defeat of incoming threats while the vehicle is moving cross-country at tactical speeds. Future developments will include the incorporation of an active-protection counter-munition able to deal with hardened threats and large-calibre, long-rod penetrators.

Similar projects are also underway in Europe. The Diehl Awiss is an active protection system that is light enough to be used on all light and heavily armoured air deployable vehicles. Its use would allow the weight of armour carried by future vehicles to be reduced, minimising vehicle all-up weight and allowing air transportation. The Awiss uses a Ka-band radar sensor to detect incoming threats. These would be handed off to one of the system's launch units, each of which carries an Integrated Cueing Sensor and three counter-munitions. The total weight of a complete system with two launchers, which would be able to provide all-round coverage would be 400 kg.

System reaction time would be less than 400 ms, and the launchers would be able to slew through 90 degrees in less than 140 ms. A trailing wire between the launcher and the counter-munition serves as a command link to initiate detonation at the optimum moment.

Software development is still under way, says the company, but hardware tests have already been carried out, including the engagement of a Milan missile.

Grenades

An alternative way of protecting oneself against shoulder-fired weapons is perhaps to ensure that they never leave their tube. Ruag has recently developed a grenade the warhead of which is based on that of the Mapam mortar round (see the "What's Up" article in the Armada magazine to which this supplement belongs). Basically, the Mapam is a bomb designed to radially scatter a high density of steel balls over a very precise range. The same technique has been adopted for the Crad (Close Range Active Defence), a grenade launched from existing (or additional) smoke grenade launchers, only these grenades throw a conical shower of steel balls down onto anyone displaying hostile intentions--like, say, aiming an RPG7 at one's vehicle.
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Title Annotation:Complete Guide
Author:Richardson, Doug
Publication:Armada International
Date:Dec 1, 2003
Words:1587
Previous Article:Further down the road.
Next Article:Stealth.


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