From the birth of the gunpowder-warfare era, soldiers have been incrementally striving for bigger, more powerful and more accurate guns. Their quest has resulted in the present-day big guns, such as tanks and artillery guns. These big guns—the ‘noisy giant cousins’ of rifles—have the capability to win battles by shattering and scaring the enemy.

Fig. 1: German Panzer Haubitz 2000 self-propelled gun with its long barrel (Photograph credit: Quistnix, through Wikimedia commons)
Fig. 1: German Panzer Haubitz 2000 self-propelled gun with its long barrel (Photograph credit: Quistnix, through Wikimedia commons)
Fig. 2: Typical firing of SPG
Fig. 2: Typical firing of SPG
Fig. 3: American M1A1 Abrams tank with its shorter barrel (Photograph credit: US Navy, through Wikipedia)
Fig. 3: American M1A1 Abrams tank with its shorter barrel
(Photograph credit: US Navy, through Wikipedia)

The big guns entered the battlefield as state-of-the-art machines during the First World War and played havoc during the Second World War. But they were just like the shaky grandfathers of today’s big guns. This is because electronics has virtually penetrated all the subsystems of today’s big guns. This penetration has made these guns enormously more capable than their shaky ancestors.

What these guns actually do and how
Though tanks and artillery guns are big and possess long barrels, these are not the same. These are brothers with different purposes. Artillery guns, epitomised by stationary field guns, have longer barrels than the tanks. But here, just for the sake of fair comparison, let us see the electronics present in their track-wheeled brothers—the self-propelled guns (SPGs), which are chiefly area-strike weapons.

Explore Circuits and Projects Explore Videos and Tutorials

A group of such guns, called battery, is used to bombard an area rather than a single target. With their huge explosive shells, they can bombard a target area situated as far as 30 km away. This is called artillery barrage. An artillery barrage is the most scary and devastating aspect in the battlefield and can flatten structures, vehicles and men. Artillery barrage is the most lethal form of firepower next only to bombing from aircraft. Skilled gunners can engage a single target even as small as a car from as far as 20 km. But the intriguing aspect is that the gunners do not ‘see’ their target.

Fig. 4: Typical tank firing
Fig. 4: Typical tank firing
Fig. 5: American AGM-114 Hellfire laser-guided missile on predator drone. Missile’s front tip is the eye (Photograph credit: US Department of Defense, through Wikipedia)
Fig. 5: American AGM-114 Hellfire laser-guided missile on predator drone. Missile’s front tip is the eye (Photograph credit: US Department of Defense, through Wikipedia)
Fig. 6: American BGM-71 tube-launched optically-tracked wire commanded data link guided missile with the wire trailing behind the missile (Photograph credit: US Army, through Wikipedia)
Fig. 6: American BGM-71 tube-launched optically-tracked wire commanded data link guided missile with the wire trailing behind the missile (Photograph credit: US Army, through Wikipedia)

In military parlance, the common saying is that “you can’t fire at what you don’t see!” But perhaps these guns are one of the very few exceptions as they don’t see their targets. They simply look at the sky and shoot the shells and shatter the targets into smithereens. When these guns face the sky and fire the shells, the shells obey gravity and ballistics, like a stone thrown upwards. The shells fly in a parabolic trajectory and land on the target area.

These guns are deployed 30 to 40 km behind the frontlines and fired. A trooper employed as forward observer, operating along with the frontline troops, is the key. When enemy forces try to overwhelm the frontline troops, commander calls for artillery support in the form of barrage. The observer sees and selects the target, directs the firing of these guns and reports the impact. The guns can fire even over a hill to neutralise the enemy in support of frontline troops, in what is called ‘indirect fire support.’

For the shells to land accurately on the target area, the gun’s elevation and azimuth to be maintained are calculated through trigonometry. The accuracy of the calculation determines the accuracy of a shot! Firing these guns requires a complex alignment process and use of instruments like sextants and clinometers. Simply put, it is more of an engineering process than a firing process.

During the First World War, in the Battle of the Somme, a strange-looking beastly armoured metallic vehicle making ‘clang clink clang’ noises crawled into the battlefield like a caterpillar. It was a British invention that was conspicuously named as ‘tank’ to conceal its real purpose of crossing trenches. As the trench warfare of the WW-I went out of favour of the militaries, tanks got a new job. That job was to be the spearhead of an advancing force. Germans exploited this aspect through their blitzkrieg campaigns in WW-II and tanks came to prominence.

Unlike the artillery guns, tanks see their targets and shatter them. During an advance, typically, the tank will put its crosshairs on anything that annoys the advance and blow it into smithereens. If a bunker is annoying the infantry the tank will put it in its crosshairs and shatter it, in what is called ‘direct fire support.’ The shells fired by tanks exit the gun in a flat trajectory at a speed of around 1525 m/s (5000 ft/s) whereas the shells fired from SPGs exit the gun in a parabolic trajectory at a speed of around 305 m/s (1000 ft/s).

READ
Robot that can walk and jump on water

The basic differences between a tank and an SPG make them to complement each other. In an armoured thrust deep inside the enemy territory, the tanks form frontline and proceed shattering what they see. The SPGs follow the frontline at a distance of 20 km, giving indirect fire support as and when required. With this background let us embark on a virtual tour to see the electronic systems present in these big guns—the defensive, offensive and command & control systems.

Crew protection systems
Losing a well-trained crew is more unacceptable for an army than losing a tank or self-propelled gun. So these big guns have armour around them. As the self-propelled guns are not operated on the frontlines, these have minimum armour. This armour can protect the crew only from bullets and splinters, but not from an enemy tank’s shell. On the other hand, as the tanks form the spearhead of an invasion force, they require enormous protection that is usually provided by its mightily heavy armour.

The tank’s heavy armour, through its bulk and tensile strength, protects the crew to a greater extent even from the enemy shells. This armour itself became an iconic representation of tanks within a few years of tanks’ introduction into battlefield. Army units centred on tanks got named as armoured divisions, armoured corps, etc, and now form the core of the offensive formations all over the world.

Introduction of active protection systems (APS) for crew has made the armour just the last line of defence. The APS protect the tank from anti-tank missiles and rockets. Hard-kill APS (HK-APS) destroy the projectiles while soft-kill APS (SK-APS) spoofs and diverts them.

Soft-kill active protection systems
SK-APS are used against laser-homing and wire-guided anti-tank missiles. Laser-homing missiles look for laser reflections from the targeted tank to home in and attack. For this, a laser designator is focussed on the targeted tank by another entity. The designator continuously emits pulse-coded IR laser beam which gets meagrely reflected by the tank. After the missile is launched, while it is flying, it looks for these meagre reflections from the targeted tank, spots them, and flies towards the reflection (tank) to destroy it.

A wire-guided anti-tank missile is launched from a command-launcher console. The missile uncoils a thin wire while flying, throughout its range. The command-launcher console sends guidance signal to the missile through this wire. The operator just keeps the target on the crosshairs of the command-launcher console. A computer inside the console understands the orientation of the command-launcher console. The missile has a small IR beacon on its rear whose emissions the command-launcher console continuously tracks. From these two parameters, the command-launcher console understands the missile’s trajectory and the target’s position. It then calculates the trajectory that the missile should follow. Accordingly, it sends the guidance signals through the uncoiled wire.

Fig. 7: Block diagram of a typical active protection system showing both hard and soft kill components
Fig. 7: Block diagram of a typical active protection system showing both hard and soft kill components
Fig. 8: Shtora with jammers active; note the lit red flashlights (Internet photo)
Fig. 8: Shtora with jammers active; note the lit red flashlights
(Internet photo)

The probability of a tank being engaged by any of these two types of missiles is very high. So the SK-APS must be capable of tackling both these types. A typical SK-APS is based on a control computer taking input from laser sensors (situated at strategic locations on the tank’s body) and controlling an electro-optical jammer and grenade launchers, which are situated on the sides of the tank.

To tackle laser-guided missiles, the SK-APS computer continuously looks for any laser emissions in the tank’s vicinity through its laser sensors. Once the control computer detects a pattern of laser emissions, it activates the grenade launchers present in the direction from where the missile is arriving. Grenade launchers fire smoke grenades that dispense a thick aerosol cloud at a distance from the tank and effectively erect a smoke screen. This cloud is opaque for the lasers from the designators to penetrate. So the laser gets reflected and the missile mistakes the cloud as a target. But unknown to the missile, the tank moves to a different position and escapes from the killer missile.

READ
Real Electronics, Learnt Virtually

To defeat wire-guided missiles, the SK-APS, uses a jammer. The jammer is a powerful IR flashlight that can also pulsate. The command-launcher console tracks the IR beacon of the missile to find the position of the missile. When the missile starts approaching the tank, the SK-APS computer activates the electro-optical jammers that start emitting IR pulses. The command-launcher console mistakes the jammer for missile’s IR beacon. Since jammer is an integral part of the tank, the command-launcher thinks that the missile is exactly on course, but in fact the missile is now off course. The missile therefore crashes somewhere other than the tank.

American AN/VLQ-6 missile countermeasures device, German muti-functional self-protection system and Russian Shtora are some of the predominant SK-APS systems in use.

Hard-kill active protection systems
A major handicap of an SK-APS is its inability to defeat anti-tank rockets. An anti-tank rocket, called rocket propelled grenade (RPG), is a dumb weapon without any electronic guidance system. So it cannot be confused. It just travels in a straight line like a bullet. Though dumb and cheap, it can effectively destroy millions of dollars worth tank. Hence it has become the favourite weapon of terrorists.

The changing geopolitics has led the battles to be fought in cities against terrorists and insurgents rather than in open terrains. This requires the tanks to prowl the streets, an unfavourable ground for tanks. Even a minimally trained person can take out a tank with an RPG from a roof-top. So narrow streets and gullies have now become tank-killing grounds. This has necessitated hard-kill systems to destroy these rockets. So far only Russia and Israel have had to fight intensely inside cities and faced the wrath of the RPGs. Forced by these conditions, only they have successfully deployed such systems to defeat the RPG menace. Developmental efforts are going on all over the world to develop such systems.

Fig. 9: An Iraqi soldier with Russian rocket-propelled grenade-7 (RPG-7) (Photograph credit: US Marines, through Wikipedia)
Fig. 9: An Iraqi soldier with Russian rocket-propelled grenade-7 (RPG-7) (Photograph credit: US Marines, through Wikipedia)
Fig. 10: Interceptor launcher of Israeli ‘Iron Fist’ APS (Photograph credit: Ereshkigal1 through Wikipedia)
Fig. 10: Interceptor launcher of Israeli ‘Iron Fist’ APS
(Photograph credit: Ereshkigal1 through Wikipedia)

The HK-APS is a fully-automatic system providing a very high degree of protection for the tank in all climatic and terrain conditions. It can protect the tank from anti-tank rockets and missiles, and treats them the same way. It uses radar for detecting the incoming projectile missile or rocket. Then it uses interceptor rocket launchers instead of grenade launchers and jammers.

Multi-directional radar mounted on roof of the tank acts as eyes of the HK-APS and constantly scans for an approaching rocket. Depending on the type and design of the HK-APS, separate radars scanning different sectors may replace this multi-directional radar. The HK-APS computer filters the resultant radar echoes and culls out the echoes matching that of these RPGs.

Once the echo of an RPG is filtered and identified, the radar switches to the target-tracking mode. In this mode, it stops looking elsewhere and continuously looks at the projectile to derive the direction and bearing (trajectory) of the incoming RPG. This trajectory data is fed into the APS computer of the HK-APS.

If the computer finds that the trajectory of the projectile is towards the tank, it calculates the right time and angle to destroy the RPG. Once the RPG has reached the right area, the control computer activates the rocket launcher to fire a short-range interceptor rocket. This rocket, after reaching the proximity of the RPG, explodes and releases many fragments that in turn destroy the RPG. The same methodology applies for anti-tank missiles also.

The reaction time of these hard-kill active protection systems is generally in milliseconds after an RPG is detected. The RPG is intercepted within a blink of an eye. After destroying an RPG, the system gets ready to destroy the next projectile within half a second. In a separate interactive display, the tank commander sets the modes of operation and monitors status of the system. Even if a projectile passes without harming the tank, through this display the HK-APS indicates to the tank commander the direction from where it was fired. The tank commander may, in turn, attack that source of attack.

READ
India Launches Final Satellite For IRNSS Navigation System

The design of these APS is such that they do not respond to decoys. The modern Russian HK-APS systems are rumoured to be even capable of working in a group with the APS of the adjacent tanks. But further details are kept as highly classified information. In general, how the APS distinguishes between different types of missiles and accordingly fixes its modus operandi are not revealed in the open domains.

German AMAP-ADS, Swedish LEDS-150 and American Quick Kill are some of the HK-APS systems in pre-induction phases, while Israeli Iron Fist and Trophy and Russian Arena are fully operational. The only disadvantage of HK-APS is that it is dangerous for the infantry to be within 20-30 metres of the tank during joint infantry-armour operations. A tank can either have SK-APS or HK-APS, not both.

But APS cannot offer protection against the high-speed anti-tank shells fired by other tanks. Because of the speed (1.5 km/s) at which these shells travel, it is impossible for any system to intercept them. The best way to avoid these shells is through better tactics so as to avoid getting shot at. But in spite of the tactics if a tank is shot, the armour is the last line of defence. Notwithstanding the armour’s strength, electronics has penetrated these armours. So, now smart armours are being developed to replace the traditional armours.

Smart armour
The armour explained below, though still in research phase in the UK, is likely to enter the battlefield in the next decade. This explosive reactive armour (ERA) uses layers of highly explosive material sandwiched between armour plates. When a projectile hits the ERA, the hit detonates the explosive layers. The resulting explosion pushes the outer steel plates on to the warhead and disrupts its flow. All this happens in milliseconds. This counter explosion reduces the force of impact greatly and saves the tank crew. This armour is presently used in the form of ERA tiles fitted over the existing tank’s armour. The ERA tiles have to be replaced after a hit.

The ‘smart’ concept has been extended to the ERA. In future, the ERA will be formed as small ERA blocks instead of ERA tiles and their detonation will be controlled by a computer. Pressure sensors will be embedded into the ERA blocks. On a shell’s hitting the armour, the computer through the pressure sensors would sense the location, velocity and diameter of the shell from the impact. Accordingly, the computer would detonate only the relevant explosive elements.

Through this ‘Smart ERA’ concept, minimum force will be used to destroy the shell. Further, the need to change an entire ERA tile would be eliminated. The smaller damaged explosive blocks would be easily replaced at a later time. Since there is only one-in-a-million chance of two shells hitting at the same point, the tank will be safe even without an immediate ERA replacement.

To sum up, electronic tank protection systems have become the tank’s first line of defence, pushing the armour to be the last resort. Army strategists, due to these APS, foresee the reduction of armour weight. Such reduction will make the tanks light, fuel-efficient and agile.

Electronic systems to defend tanks are fine but what about the electronic systems for offensive capabilities? For that the electronic fire control system comes into the play, which will be described in the next part.
To be continued next month


The author has contributed several articles in the past as well

LEAVE A REPLY