Rheinmetall tests new Active Defense System under live fire

Defense supplier Rheinmetall AG's newly developed Active Defense System (AMAP-ADS) is designed to provide an unmatched level of protection to land vehicles through the use of sophisticated threat detection, identification and nullification technology that takes just milliseconds to react. The system, which also minimizes collateral damage around the vehicle, was recently demonstrated under live fire for a group of potential customers who watched unprotected from a distance of 150m.

During the test late last year, an RPG7 rocket propelled grenade was fired from a distance of 18m at an ADS-equipped Fuchs/Fox 1A8 armored personnel carrier (APC) being towed at 20 km/h. The RPG7 warhead is a shaped charge with 0.73 kg of the explosive HMX which will penetrate over half a meter of rolled homogeneous armor.

The RPG7 travels at 110 m/s before its rocket motor fires. The ADS thus had only a tenth of a second from launch to recognize the threat, confirm it as a real threat, decide on a response, and activate the appropriate countermeasure.

As the image shows, the AMAP-ADS successfully destroyed the RPG7 in close proximity to the APC. As the ADS operation does not generate fragments or other debris, the observers were unscathed, and an Asian representative has now ordered the system for his country.

The above sequence of three high-speed video frames shows the destruction taking place. The first frame shows the RPG7 projectile approaching the Fuchs/Fox APC. The second frame is taken just after activation of the ADS, showing the explosive operation and destroying the RPG7 in mid-air adjacent to the surface of the vehicle. The final frame shows the post-test largely undamaged APC.

The AMAP-ADS protects a complete hemisphere with a reaction time of roughly 500 microseconds, allowing it to react not only to RPGs, but to virtually any close-in threat (anti-tank guided missiles, kinetic energy projectiles, explosively formed penetrators, IEDs, etc.).

This level of performance cannot currently be matched by projectile-based active protection systems, such as Quick Kill, Iron Fist, and Trophy.

Multiple threats

An AMAP-ADS system can also counter multiple threats, as demonstrated in an earlier Swedish test against a pair of RPG7 rounds fired simultaneously at the same point on the target. The RPG7 projectiles were destroyed by adjacent sensor-countermeasure modules. The same system detected but rejected a 7.62 mm round as a threat. The sensor-countermeasure modules are fast and accurate enough to intercept 120 mm kinetic energy penetrators (such as the M829 APFSDS sabot rounds, moving at ~1700 m/s), but the protected vehicle must still carry substantial armor, as the countermeasures only break up such rounds.

To top it off, the ADS is light (well, for a close-in missile defense system). A light military vehicle the size of a HUMVEE can be protected using a system weighing less than 150 kg.

Fuchs/Fox 1A8 APC equipped with ADS

The key components of AMAP-ADS are sensor-countermeasure modules arranged about the vehicle.

Each sensor-countermeasure module includes a pair of infrared sensor systems. Pre-warning of a potential threat is provided by a passive IR search and tracking sensor (IRST). When a potential threat is noted, an eyesafe laser-based rangefinder merges data with that of the IRST to acquire, identify, extrapolate the threat's trajectory, and, if a threat is confirmed, command a counterattack. A given ADS system will have 15-30 IR sensor systems (19 appear on the Fuchs 1A8). The IR sensors have overlapping fields of view, as do their associated countermeasures. When the threat is less than a meter from the vehicle, directed energy countermeasures destroy the threat, targeting the most vulnerable part of the threat projectile.

Countermeasures

So what are directed energy countermeasures? Rheinmetall AG and ADS GmbH are rather secretive about the principle and function of the countermeasures, but I have been able to piece together a likely countermeasure system. The following photo shows the ADS-equipped Fuchs/Fox 1A8 after the ADS has defeated an RPG7 attack.

Circled in red, the rearmost sensor-countermeasure module is clearly altered from those of its cohort. The tube containing a slot located between each pair of sensor units has disappeared. (The lower cover is the correct height to be knocked off by the residual momentum of the RPG.)

The major clues about the operating principle of the ADS explosively-driven countermeasures include the following:

• The AMAP-ADS has no moving parts;
• The AMAP-ADS can be directed to attack a specific part of a threat projectile;
• The AMAP-ADS countermeasures can cover a portion of adjacent sectors;
• The AMAP-ADS produces no shrapnel or fragments.

Countermeasures consistent with these clues could be provided by a slightly curved linear shaped charge housed within each of the tubes connecting adjacent sensor housings. The actual form of the countermeasure would be a thin, flat fan of rapidly moving particulate material driven outward and downward by the explosion of the shaped charge.
The shaped charge mounting must hold the charge at a known position and angle, so that the plane of the flat fan is known. The fan must be wide enough to cover roughly half of the adjacent sectors as well as its own. Thus, when you know the trajectory of the threat and the position of the fan as a function of time, the countermeasure can intercept the threat by correctly timing the initiation of the shaped charge. The countermeasure can even be directed against a specific part of the threat projectile by making small adjustments to the initiation timing.

Finally, the fact that the countermeasures can kill a threat without production of shrapnel and debris begs the question - what material is the shaped charge liner made of ? The distance over which the flat fan must remain reasonably well focused is about 2 meters, which given the size of the countermeasure tubes is around 20 widths of the linear shaped charge.

There has to be a liner, as the distance of the shaped charge to the threat projectile is too great to use the Monroe effect itself - the high-speed detonation products would lose focus. But the liner can't produce shrapnel, so it can't be the usual copper or tungsten liner.

The likely solution is that the liner is made of a sintered or otherwise frangible metal. Such a liner will turn into a highly focused beam of sand, capable of the level of destruction required, but not representing a danger to anyone outside the immediate vicinity. No danger, that is, save for hearing loss. There is a reason that the official Israeli Defense Force designation for Trophy is Windbreaker!

State of the art of active close-in protection of armored vehicles has advanced with amazing speed in the past decade. Although Rheinmetall AG's AMAP-ADS may be top dog at the moment, improvements to Advanced Protection Systems are coming fast and furious. It will be fascinating to discover what such systems will look like in another decade!