Saturday, January 21, 2017

Leopard 2 in Syria - part 2

Yesterday a new video was released by ISIS terrorists showing a bunch of destroyed main battle tanks (MBTs) and armored personnel carriers (APCs) near the Syrian city of Al-Bab. This video however has proven something, that I understimated a certain weapon. Not anti-tank guided missiles (ATGMs), not improvised explosive devices (IEDs). A much older weapon: propaganda. The same weapon that turned the Tiger heavy tank - a rather mediocre design of it's time - to a supposed super tank, that still is being worshipped by some individuals today. However the propaganda worked, invoking a Tiger-phobia on the side of the allies.

Now, what exaclty has happened? A new video showing the exact same area that the first few videos were showing. The destroyed or damaged tanks are probably all identical to the tanks already shown in earlier videos, that have been covered by numerous news articles and blogs. Still some people start writing articles in a sort of kneejerk reaction, claiming that these are newly defeated tanks and that the Turkish Army is just poorly trained or the Leopard 2 is a poorly designed tank, incapable of competing on the same level as the tanks of other countries (even though this is not tank-vs-tank warfare...). This again leads to people to come and reply or spread the articles, which are pushing for their own agenda. "The T-90 is so much better, only one was penetrated!", "All people who think the Leopard 2 is a good are Nazi-tank fanboys" and "The Abrams/Challenger 2/T-84 is an inpenetratable super tank". People love to ignore the fact that the Turkish Leopard 2A4 is fitted with out-dated armor, possibly still the first generation of armor technology introduced with the original Leopard 2 in 1979. The fact that the Turkish Army was purged after the failed coup attempt - in which most tank units were equipped with Leopard 2A4 tanks - is intentionally ignored.

So what exactly has happened to the Leopard 2 in the past month in Syria? Well, apparently not much in that area. ISIS was only interested in spreading images from already destroyed tanks - this might mean that there are no newer encounters that were video-taped.

Leopard 2 tank wrecks in Syria
The first Leopard 2A4 tanks of the Turkish Army were destroyed or at least disabled in combat already in December. Above are screenshots from one of the very first combat encounters, below are captures from two different propaganda videos - all showing the same two destroyed tanks. Well that's propaganda, pretending (by using different camera positions and filming on different days) to have destroyed six tanks, while in reality only two were destroyed (or rather one was destroyed, while one was apparently rendered immobile and abandoned).

An ATGM penetrated the roof of this tank
The image above shows a tank was hit by an ATGM at the roof. There are at least three different scenes from different videos showing this tank. It actually might be four, but the image quality of one is so bad, that it couldn't be clarified without doubt. This shows again how the terrorists' propaganda tries to inflate kill numbers in an attempt to demoralize the enemy. They supposedly even filmed the tank at different times of the day, so that the mood of light changed.

Blowing up captured tanks
The terrorists are known to have captured up to three tanks, of which one had a track issue. So what to do with a tank that cannot be utilized by the own forces? Blow it up in a propaganda video, pretending that it was an enemy tank destroyed in combat.

Victims of a large explosion: airstrike or blown up after being abandoned
Supposedly at least one captured tank was destroyed by an airstrike from a Turkish F-16. A photo showing a Leopard 2A4 with turret popped of the hull was shared on Twitter in December 2016. While it is not exactly confirmed that this tank is one of the two destroyed tanks above, all vehicles in above photo show damaga typical for airstirkes or large explosive charges being placed inside the vehicle. This can be seen by locking at the front of the Otokar APV (engine compartment blown off) and the excessive damage caused to the frontal Leopard 2.
One can only speculate about the exact fate of this tanks. Were they abandoned and then destroyed by an airstrike? Were they captured by ISIS and then destroyed by Turkish forces? Did the terrorist blow them up for a propaganda video?

Overview with text by militaysta
That's why speculating about how awful or how good some military unit perform just based on photos of wrecks doesn't make sense. Who knows how many hits the tank took before ending there? Or maybe the tanks didn't even take any damage but broke down before combat. Who would know based on a wreck of a tank?
Snafu Solomon reblogged an interesting article from DieselPunkIsDad on survivability bias. While this term doesn't exactly apply to the topic, it clearly shows the same problem: people are judging the peformance of a combat vehicle, a military unit or even a whole nation based on a biased subset of encounters. The Battle of Crete was a horrible failure from the perspective of the Nazi-German Army, which abandoned the tactics of airborne invasion via paratroopers after it. From the perspective of the Allies, who were unaware of the German losses, the airborne invasion was suddenly a highly effective tool of warfare - that happens when only a subset of data is considered. How many videos out there are showing an Iraqi or a Saudi Abrams tank getting hit by an ATGM, while sitting in the open without (mechanized/motorized) infantry support? Everytime such a video appears, someone comments on how bad said vehicle/persons are doing and how they are essentially getting slaughtered. What is ignored in this context is that the terrorists will only show your successful attacks - that's how propaganda works. But how many times do their attacks fail by missing the target, failing to penetrate the armor or being discovered and killed?

Older informations on Turkish losses via Reddit

So what is the conclusion of this post? Well, probably that one should keep calm and take some time to think about what is shown by a source and what the motivation for showing this is. Based on the videos and earlier reports of Turkish losses, there seem to be no recently destroyed tanks at this specific area near Al-Bab. This could have several different reasons, but speculations without sources won't lead to much.
According to older Turkish sources, a total of ten Leopard 2A4 tanks, one M60T Sabra and four other vehicles were disabled or destroyed in the area around Al-Bab. One Leopard 2 had an issue with the tracks and the situation of one tank is unknown (supposedly this tank is among the ones captured by ISIS). Two tanks were damaged by IEDs, one of them heavily. A further tank was damaged by a mortar attack, while the other five Leopard 2A4 tanks were damaged by ATGMs - back then not a single tank was listed as destroyed by ATGMs. Earlier sources from about a week before the losses were leaked/published via Twitter claim that fifteen M60T Sabra tanks, three M60 tanks and three Leopard 2A4 were hit by ATGMs. One of the M60 tanks and three Sabras were total losses. Supposedly ten soldiers died in Turkish tanks at this time. The fact that no new tank wrecks appeared in the area from Al-Bab doesn't mean that Turkey hasn't lost more tanks since then - but it also doesn't directly confirm any losses at other places.

Turkish sources claim that between the 8th and 18th January 192 air raids and firing 2,196 rounds of artillery, tank and mortar ammunition resulted in the death of 1,362 enemies, a further 168 were wounded. As always these claims haver to be taken with a grain of salt, as there is no proof for any of these claims and kill figures of airstrikes and artillery are known to be exaggerated quite often. Still if true, one shouldn't pretend that the Turkish Army is so bad and the "Arabs are horrible at war" meme applies (not to mention that technically Turks aren't Arabs). Yes, the first Leopard 2 tanks were employed in a horrible way and thus destroyed. But maybe at least some common NATO training standards are met and result in some better performance after the initial shock.

Wednesday, January 18, 2017

Early M1 Abrams composite armor

On the TankNet forums, a user with the nickname "whelm" has posted drawings from a formerly classified document on the earliest iteration of the US M1 Abrams main battle tank (MBT). He got this document from Vollketten, a user with accounts at the Sturgeon's House forum, the WoT forum and other places. It details the armor layout of the tank, showing were the Burlington composite armor is located and how it is specifically implemented on different areas.

The name of the document

Burlington special armor, also known as Chobham armor, is a type of composite armor developed in the United Kingdom by the FVRDE from the late 1960s onwards. It consists of a number of sandwich plates - also called biscuits - which are mounted in a spaced configuration. It is understood that these sandwich plates work as a type of non-explosive reactive armor (NERA), by using an elastic interlayer located between two metal plates (usually steel or alumininum). On impact the rubber will compress to the point of maximum compression, until expanding again and bouncing back. This will move more material into the path of penetration and also shatter thin and fragile projectiles, such as the shaped charge jets created by high-explosive anti-tank (HEAT) warheads commonly used on anti-tank guided missiles (ATGMs) and rocket-propelled grenades (RPGs). Essentially NERA works like explosive reactive armor, but with a lot less plate movment, as it only reuses the energy from the impacting projectile, instead of using an external energy source (such as the detonation of an explosive layer) to move the metal plates.

The location of the special armor on the M1 Abrams MBT

The special armor covers the frontal arc of the tank only, with an exception being the sides of the turret bustle. The lower front plate (LFP) of the hull is fitted with composite armor, the upper front plate, also known as glacis plate, however relies on conventional steel armor with high sloping. The gun shield and turret front, as well as complete turret side armor and the frontal two/four side skirt segments are protected by Burlington special armor aswell.

The frontal hull armor
The lower fornt plate of the M1 Abrams' hull consists of an array of NERA sandwich plates, which however only cover about half of the complete armor volume. The other half of the armor thickness is occupied by a mounting bracket for the NERA sandwich array and conventional steel armor. When hitting the hull straight on, the projectile has to pass through the exterior steel layer, four sandwich plates and then the thick inner steel plate.

The armor layout of the gun shield
The special armor of the gun shield of the Abrams follows a similar design as the hull armor, however there is no mounting bracket. The gun shield itself also does only include a rather thin backplate, however there is a thick steel plate located behind the gun shield, which might be connected to the trunnion plate. When hitting the tank straight without any oblique angle, the penetrating projectile again has to pass through four sandwich plates.

The side armor of the turret bustle
 The side armor at the turret bustle seems to be the most interesting aspect of the tank, as it not only features a sloped NERA sandwich array and a mounting bracket as seen on the lower front plate armor array, but it also features a multi-layered backplate consisting of two steel plates with another material located between them. The exact naturre of this material is unkwnon, but it could be an application of ceramic as armor material. Using ceramic armor as part of the backplate in order to absorb the leftover penetration power of a projectile, that was damaged by (N)ERA sandwiches, has been suggested and patented by the Franco-German institute in Saint-Louis; it is believed that the armor used on the Leopard 2 and Leclerc might follow the same concept.
However there is no exact proof that said material is ceramic; other possibilities include glass and silicia, which have been tested by the US Army's Ballistic Research Laboratory in the 1950s and 1960s as part of the siliceous cored armor for the T95 medium tank and the XM60 MBT. In theory the material also might be a type of glass-reinforced plastic or aluminium, as used on the early models of the Soviet T-64 and T-72 tanks.

Side skirt armor
The sides skirts of the M1 Abrams consists of a four or five layer sandwich, which is spaced from the homogenous steel base hull armor. The outermost plate is apparently a steel plate, followed by what is believed to be alternating layers of elastic material and metal. On the left hull side only the frontal two skirt elements are fitted with special armor, which is required for protecting the crew and fuel tanks along the 60° arc (±30° from the tank's center line). On the right hull side, the first four side skirt elements are made of special armor, which is required to also protect the hull ammunition storage that is located behind the turret ring at the right hull side.

Burlington armor array for the British Chieftain Mk. 5/2 MBT
Unfortunately there is no image showing the frontal turret armor, but given that we know the layouts of the frontal hull armor, the gun shield armor array and the turret side armor, there is not much reason to doubt that the frontal turret armor will look a lot differently. In general the Burlington composite armor used on the M1 Abrams is a further evolution of the British designs from the 1960s and 1970s. Thanks to nowadays declassified documents, it is a secured fact that the UK shared it's armor research with the United States and the Federal Rebuplic of Germany during the Cold War. Thus we can expect the early armor arrays used on Leopard 2 and Challenger 1 to look very similar.

Merkava armor

Other countries have developed their own versions of NERA sandwich arrays in the past. The Soviet Union adopted a very similar armor layout in 1985. Leaked Chinese armor arrays from research papers and CAD models show a very similar conception, using NERA sandwich arrays held by mounting brackets in front of thicker and multi-layered backplates. Photographs of damaged Merkava tanks reveal a similar armor concept/technology.

Chinese composite armor arrays
More modern versions of the M1 Abrams and other tanks are still following this general armor design concept, however sometimes more complex arrays with additional layers and elements are used. A common design principle according to Dipl.-Ing. Rolf Hilmes, who formerly worked at the German BWB, and according to a presentation from the British Defence Science Technology Laboratory (DSTL), is to incorporate a further heavy layer in front of the armor array, which servers to disrupt (shatter/break) the projectile, before the fragments enter the NERA array. There are different options to implement this armor, however a common way is to use heavy ERA (such as the Kontakt-5 ERA and Relikt ERA used on Soviet/Russian MBTs) or thick NERA plates (as featured on the Leopard 2A5 and subsequent versions).

Turret armor of a Soviet T-72B MBT
Photographs from US Abrams tanks damaged in the Gulf War and in the Invasion of Iraq, show that in general the armor layout of the Abrams has not been altered drastically. Most likely the materials have been improved and the thicker back plates have been replaced by mutli-layered arrays including ceramics and other materials.

M1 Abrams' side skirt penetrated during the Invasion of Iraq
A known addition to the side armor of the M1 Abrams' turret is at least a new spaced armor array, which is mounted on coil springs. The spaced armor is made up of three rather thin, multi-layered sandwhich plates. Most likely the coil springs are compressed, which would enable greater force being used against a penetrating projectile.

Destroyed M1A1 HA with exposed armor elements
A more detailed coverage of modern armor technology on this blog is planned for the future.

Saturday, January 7, 2017

Hardkill APS overview

Active protection systems (APS) have been an important topic when it comes to enhancing the protection of modern combat vehicles since a number of years. Combat in Iraq, Yemen and in Syria has proven the vulnerability of main battle tanks (MBTs) to handheld and/or guided anti-tank weaponry. While many people pretend that active protection systems are a rather new development, many can be traced back to the 1980s and 1990s. One of the earliest APS was tested in 1969 in Germany - that's 48 years ago! The first APS adopted in military service was the Soviet Drozd system from 1977/1978, that was fitted to a number of T-55 and T-62 tanks. According to unconfirmed rumors Drozd was used in Afghanistan.
A more commonly known APS is Trophy, which has received huge orders by the Israeli Defence Force (IDF) and was adopted on the Merkava 4M MBT and the Namer armored personnel carrier (APC). Aside of the hardkill active protection systems, which actually destroy incoming threats using countermeasures, there is also the less popular category of softkill systems such as the MUSS, which has been adopted on the Puma and is being tested by the British Army.

But what types of active hardkill protection systems exist? What makes an APS good? What are the drawbacks of each specific system? This blog post tries to dive a bit deeper in the topic of APS, but due to the secret nature of many details and characteristics it ends up being not more than a somewhat superficial overview of some types of active protection systems that have been developed in the past decades.

In general the following characteristics are essential to evaluate the performance of an active protection system:
  • detection range
  • minimum defeat distance (MDD)
  • system reaction time (SRT)
  • the distance to the interception point (IP)
  • multi-hit capability
  • short-time multi-hit capability
  • simultaneous threat defeat
The system reaction time is the time required for the system to detect, engage and defeat an incoming threat. In includes the time to detect, track and defeat the threat. The smaller the system reaction time, the greater are the systems capabilities.
The minimum defeat distance is closely related to the SRT; it is the shortest distance from where a threat can be fired, so that the APS has still enough time to react and defeat it. If the time of flight of a RPG is smaller than the SRT, the APS will fail to protect.

The distance to the interception point is not identical with the MDD. The MDD defines how far away a threat has to be in order to be defeated, while the interception point defines the possible collateral damage. The smaller the distance to the IP, the lower is the increase in possible collateral damage caused by the APS. The minimum defeat distance equals to the interception point plus the system reaction time multiplied by the threat velocity.

Multi-hit capability, short-time multi-hit capability and simultaneous threat defeat are important for the APS in order to not become depleted or overpowered by RPGs. If a system has two rotatable launchers, it can engage at most two threats at a time, limiting the simultaneous threat defeat compared to a system with four launchers. If each launcher holds only two countermeasures, the multi-hit capability is limited to four threats on a two launcher system (firing five RPGs or ATGMs without the system being restocked will mean that one has to hit without being defeated by the APS), while a four launcher system has a multi-hit capability of eight threats (when each launcher has two countermeasures). The short-time multi-hit capability is important for certain systems, which require some time after engaging a threat to reload themselves - in such a case firing two RPGs within a short frame of time might result in a penetration of the vehicle.

The hardkill systems are categorized into three categories: APS with rotatable launchers, APS with fixed launchers, and box-based APS.

Launcher-based hardkill active protection systems

Laucher-based active protection systems suffer however from certain specific disadvantages:
  • the amount of launchers is limited to 1 - 4 (depending on APS and vehicle)
  • the amount of countermeasures is limited to 2 - 6 (depending on APS)
  • reaction time is larger, as the launcher needs time to rotate
  • due to the larger reaction time, the systems have to rely on mid/long-range radar detection (can be used to find/track the vehicle)
  • system redundancy is limited (if a vehicle has just one or two launchers, destroying one will have a big impact on the performance)

The Trophy active protection system (also known as ASPRO-A and "Windbreaker" in IDF service) is made by the Israeli company Rafael. It is actively being used by the Israeli Defence Force (IDF) on the Merkava 4M main battle tank and the Namer heavily armored personnel carrier. There are three versions of Trophy currently being offered by Rafael: Trophy-HV, Trophy-MV and Trophy-LV. The latter system is using a box-based approach and will be described at a later point in this article. Trophy-HV (heavy) has a weight of 850 kilograms and requires about 0.69 cubic metres of volume. It consists of four flat radar panels, two launchers and two autoloaders. Each autoloader holds only three rounds, so that a maximum of six threats can be engaged in the ideal case. After that, the autoloaders have to be restocked, which is only possible from the exterior and takes up some time. It cannot be reloaded in combat.
Trophy-MV (medium) is a lower weight version of Trophy, weighing only 520 kg and requiring only 0.42 cubic metres of volume. Trophy-MV is intended for medium weight vehicles like wheeled 8x8 APCs and IFVs such as the US Army's Stryker. It follows the same working mechanism and design as the Trophy-HV version, but is extended with parts of a soft-kill system. The weight savings are achieved by using a smaller, miniaturized version of Trophy-HV. It is unkown if the autoloaders hold the same amount of countermeasures.

Trophy radar panel (left) and autoloader with mock-up countermeasure (blue)
Trophy is an unique system, relying on directed multi-EFPs (MEFPs), which are bundled in one countermeasure. Each MEFP consists of 35 radially bundled EFPs located on a single warhead. Currently all configurations of Trophy use two launchers, one located per side of the vehicle. Due to the MEFP being essentially a metal container that explodes, each launcher can only hold a single countermeasure and placing two launchers directly side-by-side is not possible, because the fragments of the metal containers could damage them. In order to prevent damage to the vehicle's turret-mounted systems (such as optics) and to prevent injuries of crew members operating above the hatch, behind each Trophy launcher a blast shield made out of steel is located. This however affects the coverage of the system: it is not possible to traverse a launcher by 360°, because then the countermeasure would hit the blast shield when firing at many angles; realistically the Trophy launcher is limited to a maximum traverse arc of 200° to 220°.

The blast shield limits the traverse of the launcher
Trophy's working mechanism is not capable of defeating all types of projectiles, because the explosively formed penetrators are to small and not accurate enough, to guarantee damage to kinetic energy penetrators (KEPs) such as longrod APFSDS ammunition, which is required in order to affect their penetration capabilities. Trophy is also not fast enough to intercept EFP mines and EFP-IEDs. It is designed to defeat RPGs and ATGMs mainly, but it is also capable of defeating HE and HEAT tank rounds. The interception point is - dependening on the threat velocity - about 10 to 30 metres away from the target (e.g. the Merkava tank or Namer APC) and the system reaction time is estimated by experts of the German Army to be 300 to 350 miliseconds.

A RPG is defeated by Trophy. Note the fragments from the RPG and EFPs!
A major issue with using MEFP warheads against missiles is the fragmentation and the large lethal zone. The EFPs and fragments from the warhead casing/EFP will be shot into the direction of the incoming threat, spreading over a larger area (a desired effect, because hitting the threat wouldn't be possible otherwise) and forming a cone of fragments. This however endangers infantry aswell as soft-skinned and lightly armored vehicles located in the flight path of the fragments and EFPs. The US Army rejected Trophy because of this high danger for dismounted soldiers. While Rafael and the IDF claim that the propability of injuring a dismount is less than 1%, the IDF did indirectly admit the issue by changing the doctrine of how infantry operates alongside Trophy-equipped tanks and vehicles, making sure the infantry avoids the danger zone created by Trophy.

A further problem of this system is the low amount of ready-to-fire countermeasures (one per launcher) and the relatively long reload time; in the marketing video from Rafael at least, the automatic reloading of the launcher took more than 1.5 seconds (closer to 1.75 seconds). This means that the minimum defeat distance against multiple threats being shot at the same time is not given. An average RPG-7 round has a top speed of 294 metres per second - this means that after engaging a threat, Trophy is incapable of protecting against any RPG fired at the same side from more than 450 metres distance! Against faster flying RPGs, ATGMs and tank ammunition (a 120 mm HEAT round has a muzzle velocity of 1,140 mps!), the deadzone after reloading is considerable larger. 

It's main advantage of Trophy is probably the lower complexity and price. While other launcher-based systems use projectiles that detonate mid-air, Trophy simply tracks the threat, turns the MEFP countermeasure into the direction and fires it. It doesn't require bulky rounds with fin-stabilization, that have an expensive fuze system that is set on the launcher before firing by the APS' computer system with pre-calculated data.
Trophy seems to be offering less performance in order to reach a lower price point, making the system more attractive for militaries that can accept it's shortcomings or are on a budget.

The German AWiSS active protection system dates back to initial requirements for the German NGP next generation tank from 1993. Diehl was awarded a contract to investigate the development of two different active protection systems in 1997, one designated "AFSS" to defeat anti-tank guided missiles and RPGs and one designed to defeat kinetic energy penetrators called "AKESS". These developments lead in 1999 to AWiSS, a combined system against KEPs and missiles developed by Diehl BGT Defence. The system was used as base to create the AVePS active protection and to some extend the Iron Fist APS as part of the mutual active protection system (MAPS) cooperation between Diehl and Israeli Military Industries.

Four-barreled AWiSS launcher
AWiSS consists of a central computing unit, four Ka-band militmeter-wave radar units located around the vehicle and up to two launchers with integrated IR sensors. When one launcher is utilized, only a 240° arc can be protected against fast-flying threats fired from a close proximity; two launchers provide a full 360° protection. The launchers have either three or four barrels for countermeasures, depending on the prototype version. In order to keep the overall exterior size of the launcher small, the motor units of the AWiSS launcher are located at the interior. This means that the vehicle requires the roof of the vehicle to be pentrated, if installing it to an existing plattform. As a result retrofitting an existing vehicle with AWiSS is more complicated. The launcher adds about 400 mm to the vehicle height, while the motors requires about 400 mm internal clearance. The weight of the system is below 500 kilograms.

Three-barreled AWiSS launcher with countermeasure
The AWiSS countermeasures intercept the threats at a distance of 10 to 25 metres. Against large calibre ATGMs and KE ammunition, an interception distance of 25 metres or more is ideal, because the greater distance reduces the leftover armor penetration after intercepting the threat. Against RPGs the interception at only 10 metres is possible, a result of the German requirement of being able to defeat hand-held anti-tank weapons fired from a range of 75 metres away. The system reaction time of AWiSS is supposedly 355 miliseconds (or less than 400 ms according to older sources) and the launchers have a traverse speed of more than 600 degrees per second.

Live firing test of AWiSS (single barrel early prototype) on a Leopard 2 AV
It uses a 3 kilograms heavy HE-fragmentation or HE-blast warhead, although the latter was developed at a later point of time. This enables AWiSS to be utilized against RPGs, ATGMs (including top-attack types), HE(AT) tank ammunition aswell as large-calibre APFSDS ammunition. After first tests in 2001 with HE fragmentation grenades and in 2002 with a HE-blast grenade, a Leopard 2 AV tank equipped with AWiSS defeated a MILAN ATGM in 2006 uisng an interceptor with HE-fragmentation warhead. The fragementation warhead proved to be more effective in defeating rockets and missiles with shaped charge warheads, while the blast grenade performed superior against kinetic energy penetrators. The development of AWiSS was discontinued in favour of AVePS, which utilizes only HE blast grenades.

IAAPS launcher
The integrated army active protection system, IAAPS, is an US-American APS developed by United Defense (today part of BAE Systems) together with BAE Systems and Northrop Grumman for the US Army's Future Combat Systems (FCS) program and other vehicles. The start of it's development dates back to a TARDEC contract awarded to United Defense in 1997. The IAAPS combines a number of softkill and hardkill measures to defeat incoming missiles and RPGS. The active protection system utilizes two types of passive sensors (apparently laser warners and electro-optronical IR sensors for detecting the muzzle flash/rocket engine) and a radar system to detect incoming threats. At first the system will try to use the directable infrared countermeasure (DIRCM, essentially an IR jammer) and the laser target decoy device (LATADS) to interrupt or confuse the missiles guidance systems. If this is not successful, the IAAPS utilizes up to two launchers with four barrels to defeat the detected threats. These is achieved with HE fragmentation grenades or HE blast grenades detonating about 30 metres from the protected vehicle.

An option for extending the system was defeating kinetic energy penetrators using HE blast grenades in the same manner as AWiSS, AVePS and Iron Fist. It was successfully demonstrated in a live firing test in 2006, that the IAAPS firing new interim countermeasure (with blast warhead) was capable of getting close enough to the kinetic energy penetrators, that fuzing the warhead would have resulted in a significant reduction in penetration power. The successful tests with the original countermeasure occured in 2003. During US Army testing in 2006, the IAAPS managed to defeat several RPGs and ATGMs, even while the vehicles were moving at 40 kph.
At first the IAAPS was renamed to active defense system (ADS, not to be confused with Rheinmetall's ADS), but apparently the development of the IAAPS was stalled or canceled, after the US Army awarded a contract for the development of the Quick Kill APS to Raytheon. The current US Army program for a protection system is the modular active protection system project.

CICM launcher
A version of IAAPS known as close-in counter-measure (CICM) system was developed in 2004 for lighter vehicles. CICM is using a muzzle flash detector and a radar unit to detect incoming threats. The system requires two dual-barreled launchers for a full 360° coverage. Each launcher barrel contains 55 metal pellets (made from steel or a higher density material such as tungsten), which are fired as a shot-gun blast at incoming RPGs. The low weight of only about 200 kilograms make the CICM system suited for lightweight vehicles such as Humvees, however the short interception distance (only about 10 metres from the vehicle) make it incapable of defeating ATGMs without leaving enough left-over penetration to defeat the armor of light and medium armored vehicles.

Both AVePS and Iron Fist are result of a cooperation between Diehl of Germany and Israeli Military Industries (IMI). The cooperation was known as mutual active protection system (MAPS - not to be confused with the American modular active protection system program). These systems are to some extend based on the older AWiSS APS, but are incorporating newer technologies from Diehl and IMI. In contrast to the previous system, AVePS and Iron Fist rely only on high explosive (HE) blast grenades as countermeasures to intercept incoming threats. This reduces the probability of collateral damage. Both systems were revealed in 2006 and might utilize slightly different sub-components, delivered from local or international suppliers. For detecting incoming threats, both systems rely on radars (in case of AVePS, it is a Ka-band milimeter-wave radar similar to the one used for AWiSS) in combination with IR sensors for fine tracking. The power consumption in case of AVePS is limited to only 1.5 kW.

AVePS with two launchers on a modified Marder 1A5

AVePS (Active Vehicle Protection System) consists of the sensor units, a central computer and up to two launchers. One lighter vehicles just one launcher is used in order to reduce the weight of the system. Each launcher contains four tubes for interceptors, two mounted on each side of the launcher. The weight of the heavy version with two launchers is less than 500 kilograms, while the single launcher configuration weighs only 350 kg. The traverse speed of the launchers is more than 600° per second. No penetration of the roof is required for the launchers, however the computer control system requires 80 litres (0.08 cubic metres) of volume. The system reaction time is 300 to 350 miliseconds or 355 ms according to different German sources. It is possible to reload AVePS through open hatches without completely exiting the vehicle, because of the easy to use catridge and launcher design.

Reloading of AVePS
The mutual active protection system has been successfully tested in 2011 on the M113 (not stated by Diehl wether this was AVePS or Iron Fist) and later in the same year, AVePS was tested on the Fuchs APC. In the tests MAPS/AVePS defeated RPG-7 and Panzerfaust 3 hand-held anti-tank weapons.

A lighter version known as AWiSS/AVePS light was proposed in 2006 for assymetrical warfare, however it is not known if the development of this version has been continued, finalized or if the developments have been integrated into the normal AVePS. The main feature was a reduction in system reaction time to 300 ms or less, so that the engagement distance could be reduced.

Iron Fist system

IMI's Iron Fist uses two launchers with only two countermeasure tubes each. Unlike AVePS, it  seems to utilize the same type of flat radar panels as used on the Trophy APS. In contrast to AVePS, it integrates further soft-kill measures like Trophy-MV. These soft-kill measures are E/O jammers to defeat second-generation anti-tank guided missiles, i.e. missiles with semi-automatic line-of-sight guidance based on IR beams such as TOW or MILAN. The system reaction time is estimated to be 300 to 350 miliseconds. Iron Fist was rejected by the IDF in favour of Trophy and funding for the system was stopped, but IMI managed to gain other investors such as the US Army, which is interested in Iron Fist as part of the modular active protection system competition. The Netherlands are going to trial Iron Fist on the CV9035 IFV.

Iron Fist LC

Iron Fist Light Configuration (Iron Fist LC) aka Iron Fist Lite is a version of Iron Fist first unveiled in 2016 on the Sentinel II, a candidate for the Australian LAND 400 program Phase 2. The system appears to be a down-scaled version of Iron Fist, still utilizing two launchers with two smaller blast grenades, but apparently the soft-kill features are left out. Due to the smaller size, this system is not capable of dealing with APFSDS rods. The weight of a two launcher variant is only 551 pounds (250 kg).

AVePS defeating a Panzerfaust 3

Both systems can defeat ATGMs, RPGs and HEAT rounds from tank guns. Furthermore it is possible with these active protection systems to engage high-velocity longrod APFSDS projectiles - in ideal case tilting them to reduce the penetration capabilities dramatically. For this to be successfull, the HE blast grenade has to detonate in very close proximity to the APFSDS rod - according to IMI the distance is 50 to 80 centimetres. While this might be easy to achieve against slower flying rods under ideal conditions, there are a few technical challenges that make the anti-APFSDS mechanism of AVePS and Iron Fist appear less desirable and unreliable. For one, there is a huge difference in muzzle velocity for available APFSDS ammunition. While 105 mm APFSDS ammuntion is rather slow (with a muzzle velocity of 1,300 to 1,400 metres per second), modern 120 mm APFSDS rounds fired from longer barreled smoothbore guns can reach or even exceed 1,800 mps depending on ambient temperature. The countermeasures being rather bulky and not very fast, will be more affected by exterior influences such as (cross-)winds, temperature and pressure. Given the extremely short amount of time given to an AVePS/Iron Fist countermeasure to detonate within the 50 to 80 cm distance to a longrod APFSDS, it seems impossible to achieve a proper tilting effect under all circumstance. In an interview about Iron Fist, IMI stated that APFSDS rounds leave the muzzle with a velocity of about 1,600 mps - this might be indirectly implying that the MAPS cannot defeat faster-flying APFSDS rounds. However when tilting the rod is successful, penetration can be greatly reduce; tilting the rod by some 10° reduces armor penetration by about 50%.
By using HE blast grenades, the probability of collateral damage is greatly reduced. The HE grenade detonates close to the incoming threat, defeating it with the shockwave of the detonation. There are no sub-projectiles/fragments used to defeat the threat. 
AVePS has an advantage in terms of multi-hit capability, allowing to engage and defeat twice as much threats before having to be reloaded. IMI's Iron Fist on the other hand offers softkill features and a lower weight for a dual launcher configuration (though a configuration with a single AVePS launcher should weigh less than one with two Iron Fist launchers).
Based on German data, the minimum defeat distance of AVePS and Iron Fist should be 50 to 150 metres for RPGs and most ATGMs (depending on muzzle velocity) and more than 600 metres for kinetic energy penetrators.

LEDS-150 on the CV90 Armadillo

LEDS, which stands for stands for "land electronic defence system", is an APS made by Swedish SAAB. It is a wider family of products including the LEDS-50 laser warning system (installed on Dutch CV9035 IFVs), the LED-100 softkill protection systems, aswell as three versions of hardkill active protection systems designated LEDS-150, LEDS-200 and LEDS-300, as part of a common modular family. LEDS stands for "land electronic defence system".

Mongoose-1 missile
LEDS-150 consists of a radar and IR tracking sensors, a computer unit and up to two hardkill launchers, which SAAB describes as "high speed directed launchers" (HSDL). On smaller vehicles just one launcher is installed, while larger vehicles are fitted with two. Each HDSL holds six Mongoose-1 missiles, which are made by the South Aftrican company Denel Dynamics. The Mongoose-1 missiles appear to be substanially smaller than the blast grenades from AWiSS, AVePS and Iron Fist; in fact they seem to be more comparable to the Iron Fist Light Configuration countermeasures. SAAB claims that LEDS-150 can defeat RPGs, ATGMs and HE(AT) rounds fired from tanks, but not that it is useful against kinetic energy  penetrators. LEDS doesn't use fragmenting warheads and thus poses only limited danger to nearby infantry.

LEDS-150 intercepting a RPG
The engagement of the threats with the Mongoose-1 missile happens in a distance of 5 to 15 metres from the vehicle. LEDS-200 adds a softkill protection system against top-attack missiles, which consists of an automatically triggered foam generation system. The foam alters the vehicles physical shape and thermal signature; fire-and-forget type missiles will then most likely be unable to identify the vehicle. The foam can also be used to extinguish fires on the top of the vehicle created by molotov cocktails and other sources. LEDS-300 adds a long-range capability to the HSDLs, allowing to engage ATGMs and RPGs to a distance of 150 metres. 

Two-barreled KAPS lauuncher
The Korean Active Protection System (KAPS) is a system developed on order of the South Korean Defense Acquisition Program Administration (DAPA, 방위사업청). The development started somewhere around 2006, when South Korean officials investigated the adoption of the Russian Arena APS, but rejected it shortly after. It was developed by South Korean Agency for Defense Development (ADD) with a development budget of about $36 million until early 2011. The development was expected to be finished by 2013. KAPS consists of two search and tracking radar units, a control computer unit, IR trackers and countermeasure launchers.

KAPS radar and IR tracker

The threats are detected by two multi-panel radar units located at the frontal turret sides and IR trackers. To defeat the detected threats, the APS uses dual-barreled interceptor launchers. The KAPS is meant for the K2 Black Panther tank. Some graphics show the tank fitted with two launchers, but other graphics show the tank only equipped with a single countermeasure launcher. The prototype tested in South Korea apparently had just one launcher. 
The small physical size of the launcher units and the presented prototype model including it's own base plate imply that the KAPS launcher's traverse motors are located below the turret roof when installed on a tank, just like it was done with the original AWiSS system. This means that the adoption of KAPS requires a roof penetration, making it harder to retrofit existing vehicles with this active protection system.

KAPS defeat mechanism
According to South Korean claims, the system reaction time is about 0.2 to 0.3 seconds (200 to 300 miliseconds) from target detection to interception. It is not clear if this is including the time required to detect and track the target or not. For defeating the threats, the system uses HE fragmentation grenades with tungsten fragements. These grenades detonate in front of the incoming threat, sending a cloud of fragments towards it. This means that the system can only defeat ATGMs, RPGs and HE(AT) rounds, but is incapable of defeating kinetic energy ammunition and EFPs. Due to the nature of the countermeasure, KAPS endangers nearby infantry and soft-skinned vehicles in the path of the interceptor. Having only two barrels per launcher is a clear drawback compared to some previously mentioned systems.

The Turkish defense industry is working on the Akkor APS as an option for the new Altay tank and other vehicle programs. Main contractor for the development of the Akkor active protection system is the defense electronics company Aselsan, which also developed the fire control system for the Altay aswell as Leopard 1 and Leopard 2 upgrades. It was first reveiled at the IDEF 2015 exhibition mounted on a 6x6 Arma infantry fighting vehicle. According to Aselsan, the development of the Akkor sensor units started in 2008, the development of the countermeasure was intiated in 2010. The APS is to be ready for series production by 2017. Supposedly Turkey wants to equip the Altay tank with this APS.

The Akkor APS
The Akkor active protection system consists of soft and hardkill measures. The softkill part of the system uses laser warning sensors to trigger the vehicle's smoke grenade dischargers. It apparently doesn't feature an IR jammer. The hardkill system is composed of a central computing unit, four flat radar panels and two twin launchers for the countermeasures. The interceptors appear to be HE blast grenades based on the available photographs of the system. It is not known if the system is designed with a capability to defeat APFSDS (like AVePS, AWiSS and Iron Fist) or is designed to defeat ATGMs and RPGs only (like LEDS-150 and Iron Fist LC).

Scudo (Italian for "shield") is an active protection system developed by the Italian industry on behalf of the Italian Army. The development of Scudo was initiated in 2002 with Oto Melara apparently acting as main contractor. While most APS are utilizing either box-based or launcher-based countermeasures, Scudo makes use of both systems: the launcher-based countermeasures are described as APS, while the box-based contermeasures are called "active armor".
The contract for the development of the sensor suite for the APS and active armor was awarded in 2002, while the contract to develop the countermeasures was awarded in 2003. At this time it was expected that the development could be finished by 2006 to such an degree, so that live firing tests should be possible. The original plans saw the system ready for series production by 2009.

Graphic representing Scudo on the Ariete

For detecting the theats, Oto Melara or a sub-contractor would develop an X-band dual frequency CW radar with a range of at least 500 metres, if possible even a range of 1,000 metres. This radar would detect incoming projectiles and transfer the data to the computer unit, which then lets the hardkill launchers engage the threat when necessary. The six-barreled launchers are meant to engage the threat within a range of 30 to 100 metres from the vehicle. For a 180° rotation they should have a reaction time of only 250 ms (the total system reaction time would be slightly more, due to the tracking, etc. being part of this). For larger vehicles at least two launchers would be employed. The weight of a launcher should be less than 90 kilograms. Each launcher was required to be capable of 360° traverse and up to 30° (45° desired) elevation.
Each launcher holds up to six countermeasures, which have a 70 mm diameter and a total length of 300 mm (200 mm without fins). The countermeasure has a payload of 3.5 kilograms and is fitted with a pre-fragmented warhead, which detonates to the sides of the interceptor. In case that the grenade-countermeasures miss or that a threat is launched from a closer proximity (but still detected by the radar in time), the active armor takes over. It is designed to defeat threats within a distance of 6 to 15 metres from the vehicle. The active armor consists of 200 x 200 mm modules with a thickness of 100 mm. Each active armor tile includes a sensor, a layer of metal fragments/pellets, a layer of explosives, a microwave fuze and it's own electronics. The total weight is less than 15 kilograms, the reaction time is less than 150 miliseconds. For one firing action to defeat a threat, between two and four active armor modules are detonated. Due to the large amount of fragments used in both the grenade interceptors aswell as in the active armor, Scudo proves to be extremely dangerous to nearby infantry.

Four active armor tiles of Scudo and two sensor units on the Draco
It is not known if the development of Scudo has been discontinued or is still undergoing, but at Eurosatory 2010 the Draco air-defense vehicle presented by Oto-Melara was fitted with parts of the active armor concept of Scudo, consisting of four active armor tiles mounted at the side between two sensor units.

An issue of all launcher-based systems similar to AVePS, IAAPS, Iron Fist and LEDS-150 is the location of the launcher; in order to allow a full 360° traverse of one or multiple launchers, they have to be located atop of the turret. The problem here is that the there are other components mounted at the turret aswell, which also need an unobstructed 360° traverse such as the commander's primary optic, a remote weapon station and possible a gunner's shield for the loader's or commander's machine gun.
Diehl, the developer of AWiSS and AVePS has patented different concepts on how to solve this issue. One suggestion is using fixed launchers for the APS' countermeasure at the dead zones of the normal launchers. This would however increase the weight of the system and lead to zones without the same degree of multi-hit capability. Another, more complicated, suggestion is using a more complex countermeasure design, which uses a warhead, that is steerable in order to detonate at an angle towards the threat, so that the countermeasures can intercept at a wider arc. This however would require about three times greater defeat distance.

Bright Arrow APS
Another solution for this problem could be combining two existing design concepts: IMI's Bright Arrow APS and Rheinmetall's MSSA (main sensor slaved armament). Bright Arrow is a cut-down version of Iron Fist, which is directly integrated into a remote weapon station. The MSSA concept slaves a RWS without optronics to the commander's independent main sight. By combining these two systems, one could use a single unit containing APS countermeasures, the commander's optronics and a RWS. This would greatly reduce the dead zones of the APS and RWS, while granting the commander a less obstructed field of view. The only drawback would be, that the APS has to override the movement of RWS/commander's sight once a threat is detected.

Fixed launchers vs rotatable launchers

Aside of using rotatable launchers, a number of hardkill systems relies on fixed launchers. The main advantage of having fixed launchers is improved coverage (no dead-zones caused by RWS or optronic systems mounted on the turret) and the ability to have a much larger amount of countermeasures ready-to-fire. The system reaction time with fixed launchers is also faster, as no launcher has to be rotated towards the incoming threat. On the downside however these systems tend to be heavier and have only a limited multi-hit capability, because fixed launchers cannot be directed and not aimed at different points.

Fixed launchers

The Soviet Drozd APS was the first hardkill system to ever enter service. The development of Drozd started in the 1977 by the Soviet Tula Machine Design Bureau (KBP Tula). It is desgined to protect the frontal 80° arc of the tank against ATGMs and RPGs. A small batch of up to 250 T-55AD tanks were fitted with Drozd in 1983 for the Soviet naval infantry, which couldn't use heavier T-64 or T-72 tanks with composite armor. Drozd was also tested on a different versions of the T-62 tanks, which are rumored to have seen combat in Afghanistan.

T-55 with Drozd
Drozd uses two doppler radars (operating at 24.5 GHz) to detect incoming projectiles moving a velocity between 70 and 700 metres per second beginning at a distance of about 250 metres from the vehicle. For intercepting incoming ATGMs, Drozd uses unguided 3UOF14 rockets with a 107 mm diameter and a HE fragmentation warhead. Two interceptors can be shot from a fixed launcher covering a 20° segment of the vehicle's frontal arc; the T-55AD is fitted with four dual-barreled launchers to provide protection along an 80° frontal arc. Such a configuration was also presented on the T-80U-M2 prototype in Omsk in 1997. All calculations are done by an analog computer instead of a more advanced digital system. Drozd's 9 kilograms heavy 107 mm rockets have a velocity of about 190 metres and detonate in 7 metres distance from the vehicle (this is hard-coded within the rocket). The pre-fragmented warhead will propell about 1,000 fragments to a velocity of about 1,600 metres per second.

Drozd(-2) on a T-80U
A major issue with Drozd is that it only protect the frontal arc of the vehicle and a single 20° segment of the arc can only be hit twice before the system needs to be reloaded. Despite using fixed launchers, the system has a system reaction time of about 350 miliseconds due to relying on old 1980s technology. With the fragmentation warhead the countermeasure rockets are dangerous for nearby infantry and softskin vehicles (supposedly up to a distance of 1,000 metres from the point of detonation).

Drozd-2 model from KBP Tula
Upgraded versions of Drozd have been presented on multiple occasions, some of which have been labeled Drozd-2. A system designed with 200° coverage was tested on the Object 476M tank (an upgraded T-80 variant), which used ten dual-barreled launchers instead of only four. A system presented in 1997 (called Drozd-2 back at this time) with 18 dual-barreled launchers and modernized (and much smaller) radars and electronic was designed with 360° coverage. The Drozd-2 prototype used longer and heavier rockets (up to 19 kg). The total weight of this system was about 800 kilograms. However KBP Tula's website includes a third version designated Drozd-2, which has a total weight of 850 kilograms and uses smaller 95 mm rockets with HE-fragmentation warhead. It provides coverage of 360° in traverse and from -6° to 20° in azimuth. It destroys ATGMs and RPGs with a velocity of up to 1,200 metres within a distance of 7 to 10 metres from the vehicle. Power consumption is 0.75 kW.

Arena APS
Another APS developed in Russia is the Arena active protection system. The development of the Arena APS was started in the late 1980s, it was subsequently first tested in 1992. The existence of the Arena system was first officially revealed in 1997 to the public. In 2001 an upgraded version of Arena was demonstrated on an upgraded T-72 tank. There also is the export version known as Arena-E. The system uses a six-panel milimetric wave radar unit mounted on a mast to detect the incoming threats, a central processing unit and an array of about 32 countermeasures mounted in a collar round the turret. The radars detect threats along an arc of 220 to 270° depending on application; the rear section of the turret/vehicle is not covered. For tanks the weight of the system is about 1100 kilograms and the power consumption is about 1 kW. The radar units start to track projectiles with a velocity of 70 to 700 metres per second beginning at a distance of 50 metres. The countermeasure is used to engage the tracked projectile at about 4 to 10 metres from the vehicle.

Arena uses 5 kilograms heavy casettes (about 150 x 250 mm) filled with a number of metal fragments/pellets, a fuze and explosives, which are launched into the air at an anlge. The casette detonates mid-ar at a distance of about 5 to 7 metres from the vehicle, launching depending on source 120 or up to 400 splinters at a velocity somewhere between 1,500 and 2,000 metres at the incoming threat. The probability of destruction is about 55% according to Russian sources. The defeat mechanism (metal pellets penetrating the rocket/missile) and the short minimum defeat mechanism however result in relatively high leftover penetration power of the damage shaped charge jet fragments - it is claimed to be about 50% in extreme cases. Thus the Arena APS can only protect well armored vehicles against larger RPGs and ATGMs. The BMP-3 testbed with the Arena system has been fitted with applique armor.

Arena-3 on a T-72
At the RAE 2013 exposition, Arena-3 was presented for the first time. This system is designed to be a simple add-on system for existing vehicles and consists of three modules one located behind the turret, and two at the rear turret corner (in case of fitting the system to the T-72 tank). The rear module seems to contain some of the electronics, based on the amount of cables connected to it. The side corner modules each have two bays angled at 90° from each other. Each bay contains two countermeasures. One bay is responsible for protecting about 90° of the vehicles azimuth against up to two ATGMs/RPGs. This means the system is capable to intercept at most eights threats before being reloaden, two per 90° quadrant of the azimuth. The system provides protection along an elevation of +20 degrees to -6 degrees. The system reaction time is about 300 miliseconds.

Afghanit hardkill (red) and softkill (green) launchers
The current Russian Afghanit APS is installed on the T-14 Armata MBT, the T-15 IFV, the Kurganets-25 IFV and the Bumerang wheeled IFV/APC. It appears to be a development of Drozd, at least in terms of basic conception and layout.
The system combines softkill and hardkill features. It consists of a number of sensors, mainly doppler radars, to detect incoming missiles and rocket-propelled grenades with velocities of somewhere up to 1,500-2,000 ms. A variant utilizing UV sensors for the electro-optical tracking of ATGMs and RPGs has been proposed and supposedly was developed. It might have been ordered for the Russian Army vehicles. For defeating the detected threats, Afghanit employs fixed hardkill-launchers mounted on the hull, aswell as rotatable launchers for multi-spectral smoke-grenades. Apparently the softkill component of Afghanit does not include any sort of UV and IR jammers as found on the MUSS and Shtora softkill systems. The fixed launchers provide coverage only for a certain arc of the vehicle. There appear to be two different versions of Afghanit based on the different size of the countermeasure tubes.

According to Russian claims, the APS provides protection against ATGMs, RPGs, longrod KE penetrators and top-attack missiles. However these claims should be taken with a grain of salt. It is understood only the softkill components of Afghanit are capable of dealing with top-attack missiles. Claims about the ability to defeat KE penetrators is questionable, but it must be noted that most of the informations about this are speculations or from rather biased and "patriotic" websites. The defeat  mechanism of Afghanit seems to be based on MEFP or HE-fragementation warheads, which can affect APFSDS penetration only by a limited amount.

The light version of Afghanit on a Kurganets-25 IFV
In case of the T-14 and T-15 Armata vehicles, Afghanit utilizes ten launcher tubes covering only the frontal ~120° arc. On the Kurganets-25 and on the latest prototypes of the Bumerang, the Afghanit APS uses smaller tubes; depending on prototype five or six for each side (so 10 to 12 per vehicle), covering approximately a 200° arc at the left and right side of the vehicle, leaving the rear and front exposed.

Raytheon's Quick Kill APS uses vertically launched interceptors to defeat ATGMs and RPGs. The incoming threats are dectected by the Multi-Function Radio Frequency System radar. This radar was also mean to be integrated into the Future Combat Systems manned ground vehicles. Quick Kill uses missiles as countermeasure, of which multiple are stored in large box-shaped containers in a VLS-like manner. For each threat, a 480 mm long missile is launched vertically by small propellant or gas charge. The missile then rotates via it's rocket engine to fact the threat before it's main engine is engaged. This allows Quick Kill to provide an unobstructed 360° coverage in azimuth, while not having launchers proturding over the turret roof.

Quick Kill APS launcher
The two different types of countermeasures - guided and unguided  - have been proposed for the system. At least the unguided countermeasures have already been successfully tested. The guided countermeasures are meant to engage ATGMs and (HEAT) tank rounds, which due to their greater penetration power have to be engaged at a further distance from the vehicle to minimize the leftover penetration. The guided countermeasures are larger and more complicated. The unguided countermeasures are utilized to defeat RPGs at a closer proximity of the vehicle. On the earlier designs, each VLS unit for the Quick Kill APS stored either 18 unguided or eight of the larger guided countermeasures. Quick Kill was successfully tested in  December 2012 against an unnamed type of RPG round.

The Quick Kill APS has been highly controversial in the past decade. Originally the US Army intended to field Quick Kill as active protection system for it's vehicles, prefering the system over foreign alternatives following it's trials in 2006 and 2007. However the Army has recently chosen to evaluate foreign active protection systems and the US-made Iron Curtain system instead, suggesting that there are either delays in the development of Quick Kill or it fails to reach the desired performance metrics.

Quick Kill countermeasure launching. Note how a single countermeasure blocks most of the space over the launcher.
A major issue of Quick Kill limited space above each VLS, which might result in complications when multiple threats have to be engaged within a short amount of time. Due to the missile rotating and engaging it's rocket engine directly above the launcher, firing two Quick Kill missiles at the same time is not possible. This can in theory be fixed by using two or more VLS units located at different parts of the vehicle, but this is still very dependent on the exact location and engaging two threats simultaneously might still not be possible in all cases.

Quick Kill defeating a RPG (3D graphic from Raytheon)
Another problem of the system reporterd by some defense news websites is that Quick Kill might be not suited for lightly armored vehicles, as the HE blast of the countermeasures might deform the steel structure of the vehicle, when being detonated too close. This sounds like a rather odd problem, and it is is not confirmed by any official sources. In general Quick Kill seems to be a rather complicated design, which might lead to a much higher cost and susceptance to failure. The ammunition should be more expensive, requiring not only a warhead and a fuze, but also a propulsion system with thrust vectoring. The larger countermeasure with guidance system required to defeat ATGMs should be a lot more expensive than a simple blast grenade as used by AVePS and Iron Fist. The estimated system reaction time according to German sources is 350 to 400 ms, the weight of a single countermeasure-VLS system, the sensors and computer system is claimed to be only 140 kilograms.

The Ukranian company Microtek has developed the Zaslon active protection system. The APS provides protection against ATGMs, RPGs and HEAT ammunition fired from MBTs. Zaslon consists of a control panel and a number of apparently identical modules, which are spread along the vehicle's surface. Each module contains a radar unit and either one or two countermeasures.

Zaslon APS implementation on MBTs
Depending on application Zaslon protects a 150° frontal arc or a 360° arc of the vehicle in azimuth. For protecting a main battle tank such as the T-64 against threats from all-around, seven modules are required: one at the front, two modules on the left and right sides each, one module protecting the rear and a further module mounted at the turret roof to protect against top-attack weapons. Smaller vehicles are often pictured with only four modules: one at the fornt, one at the rear and one each at the left and right sides. A special lightweight version of the Zaslon APS known as Zaslon-L has been offered for the Polish Rosomak infantry fighting vehicle.

Zaslon APS module
The countermeasures are long tubes, filled with high explosives. Essentially the system uses HE-fragmentation grenades, which are designed to spread the fragments only into one direction. The tube is rotated into the direction where the threat would hit, then the countermeasure is detonated when the threat reaches the engagement distance. According to the manufacturer Zaslon can defeat anti-tank guided missiles, rocket-propelled grenades and HEAT ammunition fired from tank guns. While the website mentions a mechanism to weaken KE penetrators, the official specifications from the manufacturer claim that the system can only engage threats with a velocity between 70 and 1,200 metres per second; defeating APFSDS ammunition at normal combat ranges is hence not possible.

Due to the design of Zaslon, at most four threats can be engaged per vehicle side - after this the modules have to be reloaded with new HE fragmentation grenades. On smaller vehicles and on the front and rear only two threats can be engaged per side. According to Microtek, the Zaslon system has an "efficiency of operation" between 1 and 6 miliseconds. It is not exactly sure if this is meant to be the system reaction time or only part of the defeat mechanism, not including other factors such as tracking or extruding the countermeasures. Zaslon takes up one litre of internal space, if all modules are mounted externally. The system consumes between 0.4 and 0.5 kW of electrical energy


Box-based active protection systems

Explosvily formed axe (EFA) is an active protection system developed by the Czech VOP-026 Sternberk, s.p., a state-owned repair and upgrade facility for armored vehicles. The development was then taken over by the state-owned military institute Vojenský Výzkumný Ùstav s. p. (VVU). The active protection system was first presented in an article in Jane's Defence Weekly (JDW) published in 2010, after a series of successful test in 2009. The research and development of EFA has lead to improved versions known as EFA Mk. II (developed in 2011 to 2013) and the even more recent EFA Mk. III. The Czech government is planning to adopt the EFA APS after a trial and testing program running from 2014 to 2017, the main application would be the Pandur II IFV, but it might be adopted also on other combat vehicles such as the T-72M4Cz and the OT-64 Skot.

EFA-L active protection system
There appears to be a light and heavy version of the system, depending on application. The light version of EFA is also known as EFA-L and has been tested on the OT-64 Skot APC and was at least demonstrated on the Pandur II wheeled infantry fighting vehicle. EFA-L might be identical with the Mk. II version of the system, but this is only unconfirmed speculation. The heavier version of EFA was tested on the T-72M1 main battle tank and an uparmored OT-64 Skot.

Steel plate after RPG was stopped by EFA-L
EFA uses radar systems to detect incoming ammunition with a velocity of up to 1,900 metres per second. The EFA-L system uses a doppler-radar in combination with a further set of sensors - either optical sensors or microwave detectors were proposed in the JDW article.
The system uses linear shaped charges with a velocity of 7,000 m/s or more as countermeasures to defeat ATGMs, RPGs and KE projectiles. It is not known to defeat explosively formed penetrators (EFPs). ATGMs and RPGs are cut into pieces, in ideal case cutting cables or the fuze, so that the warhead does not detonate as intended. APFSDS projectiles are damaged by the linear shaped charges and fragments of the penetrator are cut away. This is leading to a considerable reduction in penetration power.

EFA defeating an APFSDS projectile
In 2009 the system was suuccessfully tested against the PG-7V ammunition fired from a RPG-7. In tests with the Soviet-era BM-15, BM-42 and the local EPpSv-97 APFSDS ammunition, the shaped charge countermeasure of the heavy version reduces penetration of APFSDS longrod penetrators by up to 30% depending on the specific type of ammunition.

An issue of the known prototypes of the EFA APS is that the shaped charge countermeasures are only upwards or downward firing, leaving either the upper vehicle (including the roof) or the lower vehicle sections unprotected. The shaped charges utilize metal liners, which will result in a higher amount of potentially lethal fragments flying around.
Like most box-based active protection systems, EFA has a limited multi-hit capability. If a round hits the exact same place were a countermeasure box was previously initated, it cannot be engaged by the APS.  

HMMWV fitted with Textron's TRAPS
The US company Textron Sytstems has developed the TRAPS to defeat RPGs. TRAPS is an acronym for Tactical RPG Airbag Protection System. TRAPS relies on commercial off-the-shelf airbags to defeat incoming RPGs. The RPGs are detected by a radar unit and the RPGs are defeated by the downwards firing airbags without any leftover penetration (apparently the fuze does not properly work when hit by an airbag.) The weight to protect the sides of a smaller four-door vehicle - such as a HMMWV - is only 125 lbs (56.7 kilograms). TRAPS has no multi-hit capability, because the airbags are fixed over the protected area, always facing down. TRAPS cannot defeat ATGMs, longrod KEPs or EFPs.

TRAPS working mechanism
The Iron Curtain APS has been developed by the US company Artemis LLC following being awarded a contract for APS development by DARPA in 2004. In it's original configuration, Iron Curtain relied on a C-band radar from the US-American Mustang Technology Group for detecting incoming RPGs, but was supposedly not capable of defeating ATGMs (which might be affiliated to the type of countermeasure aswell). In 2016 however a contract was made to integrate the RPS-10 radar system from the Israeli company Rada Electronic Industries into the system. The RPS-10 radar system is also used on the Iron Fist active protection systems. It is a S-band radar and requires between three or four flat panels to provide a 360° coverage.

Iron Curtain APS on a M-ATV
The Iron Curtain system utilizes multiple countermeasures located along the roof, which are aimed downwards. The exact type of countermeasure is not known to the public, but based on photographs and drawing it seems to be an array of small shaped charges. Multiple shaped charges seem to be located in a single counter measure array, they might be detonated at the same time to increase the likelyhood of hitting the incoming RPGs.

Iron Curtain destorying a RPG
Trophy-LV is the lightest version of Trophy, intendend for lightly armored vehicles such as uparmored HMMWVs, wheeled APC and IFVs. It was first revealed at Eurosatory 2014. It has a weight of about 200 kilograms for protecting the cabin of a HMMWV and takes up about 0.26 m³ of volume. Trophy-LV utilizes a radar system (apparently consisting of four smaller panels on the Iveco LMV) to detect incoming projectiles. When the projectiles get closer to the vehicle, electro-optical sensors mount at the corners of the system are activated. These optical sensors are used to detected the threat more accurately and send the information to the corresponding countermeasure.

Trophy-LV sensor and countermeasures
The countermeasures of Trophy-LV are mounted on along a collar at the top of the vehicle; they cover the front, rear and sides of the crew cabin of a 4x4 military vehicle. The amount of countermeasures differs depending on the application: on the M-ATV a total of 18 countermeasures (3 at the front, 6 at each side and 3 at the rear). Rafael calls the countermeasure "energetic blades", but apparently they are either metal plates or (extremely thin) linear shaped charges, which are fired downwards. Trophy-LV can only protect against RPGs, anti-tank guided missiles will have too much penetration power leftover after being intercepted by Trophy-LV, so that the base armor of the vehicle still will be penetrated. Trophy-LV cannot defeat EFPs or longrod KEPs. Due to the way how Trophy-LV is mounted on vehicles and the fact that the countermeasures cannot be directed, the system offers no multi-hit capability and leaves the roof area exposed to top-attack munitions or ATGMS and RPGs fired from roof-tops.

Graphical representation of ADS

The German AMAP-ADS has been developed by IBD Deisenroth in cooperation with Rheinmetall. After Rheinmetall increased it's amount of shares in the joint venture in 2007, the AMAP branding was dropped from the system, leaving only the name Active Defense System (ADS). The development of ADS started in the 1990s, but has lasted since at least 2011. First successful

ADS components

The ADS consists of counteremasure boxes, pre-warner sensors, electro-optical sensors and a central computing unit. The pre-warner sensors seem to be flat radar panels, but they might be designed for a much shorter range, as the ADS system is designed for close range interception. This would make it harder to target the radar systems and to detect the vehicle. The pre-warner sensors are used to determine wether a threat is coming at the vehicle. Once the vector of the threat is confirmed and the threat is classified, the electro-optical sensors are woken up for the fine-tracking of the threat. According to the ADS - Gesellschaft für aktive Schutzsysteme mbH, the joint venture between IBD and Rheinmetall - the radar detection is working in a distance from 10 to 35 metres from the vehicle The optical sensors work in a distance of only two metres (up to four metres according to other sources), while the countermeasure is engaging the threat at an interception point only one metre away from the vehicle. Supposedly the electro-optical sensors are ladar (laser detection and ranging) sensors.

ADS CAB on an Iveco LMV
There have been multiple versions of the Active Defense System, some of them prototypes that probably have been discontinued. However there are at least two different versions known as ADS CAB and ADS HAT. ADS CAB protects only the cabin of the vehicle and is meant for smaller 4x4 vehicles such as the Iveco LVM and MAN military trucks. ADS HAT (hull and turret) is meant for larger vehicles such as infantry fighting vehicles and main battle tanks. ADS CAB has a weight of 70 to 250 kilograms, while the HAT version weighs 300 to 600 kg. The peak power consumption of the CAB system is about 200 Watts, while the larger system can consume up to 1,000 Watts. An optional feature of the system is the ADS APP, which allows to share sensor informations from ADS with other component in the vehicle such as softkill systems.

ADS on the MBT Advanced Technology Demonstrator. Countermeasure in read, sensors in blue and prewarner in green.
While ADS CAB and the original version of ADS HAT seem to rely on mounting the countermeasures in a collar along the vehicle roof or the upper edge of the vehicle's hull, a new design of the Active Defence System appeared in 2015. This version uses countermeasures mounted to the turret and hull walls of the vehicle in combination with dedicated roof-mounted countermeasures to defeat top-attack ammunitions. Due to the different design, it seems reasonable to assume that this version is capable of protecting a wide vertical angle of the vehicle. While the electro-optical sensors on ADS CAB are always facing downwards at a certain angle, the sensors of the new system are mounted facing sidewards, potentionally covering a larger arc of the azimuth.
An even further enhanced version of the ADS was fitted to the Boxer CRV, which uses vertically mounted sensors and countermeasures. In this version however the amount of sensor units is reduced to half (reducing costs) and the countermeasures are set at angle, which might increase the systems coverage in the elevation.
ADS destroying a PG-7 round and a MILAN ATGM
Unlike Trophy-LV, EFA and Iron Curtain, ADS uses a directable countermeasure, which can be fired within a certain arc to each direction. This allows ADS to defeat top-attack and, thanks to the to the overlapping countermeasures, to defeat multiple threats fired at exactly the same spot. Supposedly current versions are limited to "only" three threats hitting exactly the same spot.
The true nature of this countermeasure has not been revealed by either Rheinmetall or IBD. Most times it is cryptically described as "directed energy". It has been mentioned that the countermeasure is free of fragmentation and thus it cannot utilize any sort of shaped charge warhead or metal plates as part of the defeat mechanism. According to Rheinmetall, the system is also no pure HE-blast either, which means that there has to be anything else. The Armada magazine described the countermeasure of ADS as "focused blades ofconcentrated energy".

ADS promotion video implying a DIME principle?
There are different options of how the ADS active protection system defeats threats. An option would be a DIME (dense inert metal explosive) approach: instead of using metal plates or pellets in order to defeat the threat, the system might utilize (heavy) metal powder, i.e. tungsten powder or tantalum powder. When fired by a directed blast against a threat, the powder will behave similar to a solid metal body, in areas where powder denisty and velocity is high (so in the area near the launcher). However the powder will spread fast and the decelerate, this means it won't pose any danger after a distance of a few metres.

Another option of how ADS can be fragment free, a box-based system, directable and still be effective against a wide array of threats (including APFSDS ammunition and EFPs) could be the usage of composite flyer plates. In different tests by official institutions such as the ISL, launching metal plates against an incoming projectile proved to be highly effective. Modern plates manufactured out of composite materials such as ceramics and fibreglass could perform equally well without creating lethal metal fragments. However there is no direct proof that ADS actually uses any sort of flyer plates, this is just one of many theories about the system that can be found on the internet.

Regardless of how the system works, it has proven to be able of defeating not only ATGMs and RPGs, but also EFPs and APFSDS rounds. Supposedly it is capable of "cut" through the engaged threats, shattering or bending EFPs and APFSDS penetrators in the process.

ADS defeating a RPG fired at a Fuchs 1A8 APC
The system reaction time of ADS is only 560 micro-seconds (µs) or about 0.56 miliseconds. This enables the system to defeat incoming threats even when fired from extremely short ranges. In 2011 a 477 kg heavy version of the ADS was fitted to a Fuchs 1A8, which survived being shot at by two RPGs fired at the same spot from a distance of only 18 metres. Most other APS such as AVePS, Iron Fist and Trophy would be incapable of defeating the RPGs due to their slower reaction time (in 300 miliseconds the standard RPG-7 ammunition travels more than 30 metres). Other box-based active protection systems such as EFA and Trophy-LV would have failed to protect against both RPGs, due to their limited multi-hit capability.

Swedish SEP prototype with ADS
The system is also known as AAC (Active Armor Concept) in Sweden, were it is being marketed by  Åkers Krutbruk (a company owned by IBD Deisenroth). Supposedly more than hundred firing tests were done in Sweden, because of Swedish regulations for those being less strict than the German. According to the Swedish FMV, the collateral damage caused by an RPG intercepted by the ADS is smaller than the collateral damaged caused by the RPG without interception - a strong contrast to systems such as Drozd and Trophy, which increase the collateral damage with their fragmentation-based countermeasures. ADS is also being tested in France, where a version known as SHARK (system hard kill) is being funded by the French ministry of defence.
An international costumer has decided to adopt the ADS for some of it's combat vehicle. In 2011 a contract was signed to deliver an unknown quantity of Active Defence Systems to an unnamed Asian nation. In 2013 the Armada magazine stated that deliveries of the system are under way.

German ASS active protection system
An early box-based active protection system was developed in Germany by Messerschmitt-Bölkow Bremen (MBB), Krauss-Maffei and Porsche in the late 1960s. It seems that Dr. Manfred Held, the inventor of ERA, was involved in the development of this system, which has been called ASS (probably meant to be the German acronym for "active protection system"). Two versions of this APS were designed with different layout.
Much like Iron Curtain, the system utilized multiple shaped charge warheads in order to defeat RPGs or ATGMs. The shaped charges were placed in large boxes along the vehicle's edges. When a threat flies over one of the countermeasure boxes, a number of small shaped charges is fired at it, detonating it mid-air. The system was successfully tested in 1969 against a Panzerfaust 44 "Lanze". It was meant for adoption on the Marder IFV and on tanks.

Polish APS prototype
There are a number of other box-based systems on which information is rather scarce. Poland is actively developing an APS, which utilizes boxes filled with metal pellets in order to defeat RPGs. If an RPG is detected, the explosive charge of a box is detonated, sending a cloud of metal pellets at the RPG. This system seems to be similar to the active armor of the Scudo APS and shares the high danger for nearby infantry.

APFSDS destroyed by Dr. Held's APS
The Franco-German institute at Saint-Louis (ISL) has developed an APS using metal plates (size 200 x 200 mm) propelled by either an electromagnetic charge or the detonation of explosives. The plates reach a velocity of about 400 m/s and are highly effective against ATGMs and APFSDS ammunition. Another version of this APS was proposed by Dr. Manfred Held, but this time using a combination of ERA and metal plates as reactive element. In one test, the penetration of an APFSDS was reduced by a staggering 91.5%!

Krauss-Maffei Wegmann (KMW) presented a new APS at the AUSA 2012, which they simply called "Aktives Schutzsystem" (German for active protection system). Unfortunately there is no photograph of said system. It uses radars operating in the 25 to 35 GHz band to detect and track incoming threats. The radars can track the position with an accuracy of ±10 centimetres. A typical configuration would include four radar elements, one on each corner of the vehicle. The 300 mm wide countermeasures are located at the edge of the roof, just like on older versions of the (AMAP-)ADS. The defeat of the threat happens in a distance of 2.5 to 4 metres from the vehicle, leading to only limited collateral damage. The reaction time and type of the countermeasures are unknown. The devlopment of the Aktives Schutzsystem started about 7 to 8 years before AUSA 2012.