The Macabees
10-04-2009, 20:45
[b]Improvised Explosive Devices & Mine Resistant Vehicles
The occupation of Iraq will be known as the war of improvised explosive devices, now that these have caused at least 50% of the combat casualties in Iraq by 2006 and perhaps 70% of all combat casualties up until December 2007. In Afghanistan, improvised explosive devices have claimed up to 30% of all combat casualties of United States forces, and in Lebanon an improvised explosive device claimed three Spanish soldiers in a BMR six-wheeled armored fighting vehicle. Iraq is claimed to be one of the ‘most heavily mined nations in the world’, with over ‘ten million mines in the ground’. Booby trap improvised mines, in Iraq, have been used since Saddam Hussein’s regime and has increased since the beginning of the Coalition’s occupation in 2003 – 40 to 60% of all attacks begin with an improvised explosive device going off. During Israel’s 2006 summer war in Lebanon, five Merkava main battle tanks were knocked-out as a result of the explosion of huge improvised explosive devices under the tank’s belly and it seems as if the Palestinians have begun to employ similar tactics in the Gaza Strip and the West Bank. The threat of improvised explosive devices is not unique to United States forces, as the drive to acquire mine protected vehicles has been shown by many of the nations currently operating in Afghanistan, Lebanon, Bosnia or Iraq. According to Al Qaeda, ‘Explosives are the safest weapon for the Mujahidin. Explosives allow us to escape from enemy personnel and avoid arrest. In addition, explosives hit the enemy with absolute terror and shock.’
http://i75.photobucket.com/albums/i291/Macabees/Mine%20Resistance%20Informative/M1114IED.jpg
[U.S. M1114 up-armored HMMMWV knocked-out by an IED.]
Improvised explosive devices have taken many forms, but one of the most well-known is the explosively formed penetrator (EFP). Regarding shaped charges, the explosively formed penetrator is the part of the liner mass which flows in the opposite direction of the cone at a much lesser velocity. The remnants of shaped charge penetrations into armor are normally the explosively formed penetrator, given that these are made up of the majority of the liner’s mass. However, in the case of explosive formed penetrators used in improvised explosive devices in Iraq and in submunitions around the world the penetrator is purposely forged. Explosively formed penetrators normally have wide diameters, a low length to diameter ratio and have velocities of around 1.3 kilometers per second. The formation process of the explosively formed penetrator is complex and difficult to explain, and it requires high pressure and high temperature, and is influenced by a large number of factors – there are few papers which describe this process. Although explosively formed penetrators do not offer as high penetration as their shaped charge counterparts, or kinetic energy long-rod penetrators, they can perforate the thin roof and belly armor of armored fighting vehicles. It can be expected that the penetration of an improvised explosive device will depend on the quality of construction of the bomb, but they have proved to be lethal enough in Iraq given the previously noted percentage of U.S. casualties in Iraq and Afghanistan. To give an idea, about 5% of all explosive devices used against U.S. personnel in Iraq are explosively formed penetrators, yet they have provided for a third of the fatalities and over 10% of the injuries. A vehicle’s crew can be killed or wounded indirectly, as well, as the blast of an improvised explosive device can launch components of the vehicle into the crew cabin and the bomb’s pressure waves can kill a man.
Most improvised explosive devices are probably crudely manufactured and do not dispose of the quality to guarantee a kill. For example, some improvised explosive devices include roadside vehicle-borne bombs and others may not be powerful enough. Between January and September 2007 there were twenty-five thousand recorded IED attacks in Iraq, of a total of eighty-one thousand. Many of these target Iraqi civilian targets and other attack Coalition personnel, but those relevant to this paper are specifically those designed to defeat Coalition armored fighting vehicles. This threat has led to the recent decision, of the Pentagon, to procure up to 22,000 mine-resistance ambush-protected (MRAP) vehicles, belonging to three different categories. To give an idea of the industrial mobilization effort, Force Protection increased production to thirty vehicles per month in mid-2006 and by July 2007 ramped up production up to two hundred per month to fulfill large orders from various clients, including the US Armed Forces and the Iraqi Army. The company’s work force has expanded from 200 people to almost 1,000! The MRAP market has gone from being worth a few hundred million dollars annually to as much as $10 billion a year. One of Force Protection’s 16-ton Cougar transport truck was struck by a ninety kilogram bomb, which threw the vehicle’s engine over thirty meters away from the chassis and almost destroy the vehicle in its entirety. Even though MRAP equipment is tested against twelve to twenty kilogram charges, the Cougar’s crew survived the ninety kilogram mammoth improvised explosive device! In mid-January, 2008, one of Navistar’s MaxxPro trucks, crewed by four soldiers, was hit by a ‘very large’ improvised explosive device which sent the vehicle airborne – three of the four passengers survived the attack. Navistar is currently supplying the U.S. Armed Forces with 1,900 of its MaxxPro trucks – a deal in May 2007 for 1,200 and a follow-up order in July for another 700 – for a total of $1 billion. Arguably, Navistar’s success is due to the limits of Force Protection’s production capabilities.
The United States is not the only country beginning to acquire MRAP vehicles. Spain is looking to replace its existing armored fighting vehicle fleet deployed in Afghanistan and Lebanon, with urgency. In late 2007, the Spanish Ministry of Defense decided to acquire forty Light Multirole Vehicles (LMVs) from Iveco, an Italian automotive company, for a total of €14.4 million. In January 2008 a decision was made to procure a further forty LMVs, at the risk of slowing down the acquisition of larger MRAP vehicles, for €12.4 million. Furthermore, a third order will be put in soon for another forty vehicles, for the same price tag. These vehicles will replace Spain’s indigenous URO VAMTAC, and Spain is looking to acquire a number of Category II MPRA vehicles, as well – either South Africa’s BAE Land Systems OMC’s RG-31 Mk 5, Force Protection’s 16-ton Cougar or Rafael’s Golan. Due to the loss of a BMR in Lebanon, and the deaths of three of its passengers, the Spanish Army will also purchase a number of brand-new 8x8 vehicles – to be produced in Spain – and the Ministry of Defense is currently choosing between the Swiss MOWAG Piranha V and the French VBIC. Although hardly comparable to the money invested by the United States, Spain is looking at spending between 100 and 140 million euros for 150 urgently required mine protected vehicles, and ultimately procuring around €1 billion worth up to the year 2012. However, to better understand the scope and the ambition of the program it should be taken into consideration that the Spanish government has not yet ended production of Spain’s 219 Leopard 2E main battle tanks, considered the most expensive Leopard to be produced to date. The program originally cost the Ministry of Defense €1.950 billion for 219 Leopard 2Es and 16 Buffalo armored recovery vehicles (ARVs), but costs have spiraled with recent program delays due to the mismanagement of Santa Bárbara Sistemas. The Spanish Army is also beginning to accept new Tiger attack helicopters and Pizarro infantry combat vehicles, while the Spanish Air Force is still being issued new Eurofighter Typhoon air superiority fighters. Therefore, the €1 billion should be seen within the context of Spain’s recent military spending in order to understand the urgency of the issue.
http://i75.photobucket.com/albums/i291/Macabees/Mine%20Resistance%20Informative/ied-cutout01-s.jpg
[Cut-out image of an IED.]
Other countries are also spending money to acquire state-of-the-art mine-resistant vehicles. Perhaps one of the most interesting is Canada’s recent acquisition of twenty Leopard 2A6M mine-protected main battle tanks from the German Bundeswher, while they await the arrival of forty Dutch Leopard 2A6 and forty Leopard 2A4 – the 2A6Ms will replace Canadian Leopard 1C2s in Afghanistan, and at least nineteen will be returned to Germany after their tour is complete. In Afghanistan, the Canadians have experienced around 100 casualties in their light wheeled armored fighting vehicles and twenty-four in new MRAP vehicles. Despite the addition of MEXAS non-explosive reactive armor to the hull of the Leopard 1C2, they were found to be antiquated and insufficient in front of the threat posed by mines in Afghanistan. The Leopard 2A6Ms introduces a new auxiliary power unit (APU), an air conditioning system and a number of increases in armor protection, especially against mines. The United Kingdom’s FRES program may be affected by the new drive to purchase MRAP vehicles, given rumors that the Ministry of Defense may tap into the FRES budget in order to acquire a larger number of armored trucks. In August 2006 the British Army placed an order for 108 of Force Protection’s Cougar transport trucks, and the Ministry of Defense is looking to spend between $40 and $400 million for up to 180 Medium Protected Patrol Vehicles (MPPV). Furthermore, despite the lightweight requirements for Britain’s FRES program, some fear that the IED threat will force vehicles to increase weight in order to counter the threat. Australia, which has deployed troops to Afghanistan, has also invested in the purchase of a number of Bushmaster mine-protected trucks. The improvised explosive device threat is certainly big enough to force nations to put aside existing procurement efforts in order to acquire the best mine-protected light wheeled armored trucks on the market.
Aside from the Leopard 2A6M, most tank producing nations have introduced new urban fighting kits with increased protection versus anti-tank mines and improvised explosive devices. Krauss-Maffei Wegmann (KMW) showcased the new Leopard 2 PSO (Peace Support Operation), with add-on turret and hull armor, a secondary remote weapon station near the loader’s hatch, an auxiliary power unit, panoramic 360º coverage by cameras embedded in the vehicle’s hull, an external radio, a searchlight and a dozer blade. Also shown at the Eurosatory 2006 exhibition was France’s AZUR (Action en Zone Urbaine), for Nexter’s Leclerc main battle tank. In the kit, a remote weapon station replaces the commander’s pintle-mounted machine gun, new appliqué composite panels for the side skirts, and added armor to the engine bay, as well as the application of slat armor to protect the entire rear of the vehicle. Perhaps one of the better urban warfare kits is Israel’s new Merkava LIC, which boasts of added all-around protection and increased hull bottom armor thickness. Furthermore, to protect sensitive items against debris, shrapnel and rocks all air intakes, exhausts and electronics are protected by steel mesh, similar to the Leopard 2 PSO. The commander’s cupola is replaced by a new cupola, which allows the commander greater visibility from a higher position and the remote controlled 12.7mm gun is repositioned above the main gun. Interestingly, a new hatch has been introduced in the rear door, to allow snipers to protect the vehicle’s rear. These may equip Israeli Merkava Mk 3s, while the Mk 4 may receive a separate upgrade. This includes two-axis stabilization of the commander’s panoramic sights, with new-generation FLIR and TV channels. The Merkava was designed, originally, with a v-shaped hull which was hollow between the bottom of the ‘crest’ and the thinner floor plates above – in the first two models this space was filled with fuel, but in the Mk 3 and Mk4 the fuel tank has been eliminated and instead it’s spaced simply with air. On the other hand, some sources indicate that fuel will actually suppress a shaped charge jet (or an explosively formed penetrator) if the fuel tank is self-sealing. Perhaps the most well-known urban kit for a main battle tank is the Abram’s TUSK modification package (tank urban survivability kit), which includes a new thermal sight for the loader, a remote weapon station for the tank commander, explosive reactive armor on the side skirts, a rear protecting unit composed of slat armor, a gun shield for the loader and an infantry phone in the rear. It’s possible that these new reactive armor tiles are similar to the Blazer reactive armor tiles applied to the Bradley infantry fighting vehicles and M60A1 main battle tanks in the early 90s.
http://i75.photobucket.com/albums/i291/Macabees/Mine%20Resistance%20Informative/MerkavaMk3LIC.jpg
[Merkava Mk. 3 LIC; note the sniper hatch in the rear door.]
However, apart from the Merkava, these modifications are only of limited use against improvised explosive devices. As noticed, most increase protection of the tank on the side armor and the rear, prioritizing protection against rocket propelled grenades. However, only the Merkava has effective armor protection on the tank’s belly, with the v-shaped hull, and even this has failed the tank in Lebanon, where it experienced charges of up to 100kg. Furthermore, although the additional floor armor on the Leopard 2A6M might be able to stop the penetration of an explosively formed penetrator, it does not protect the crew from the blast and shock effects – the same is true for Nexter’s anti-TMRP-6 Kpam protection kit for armored fighting vehicles. This is more evident in the recent up-armor attempts on the M1114 HMMWV, which began in 1997. The M1114 features add-on blast deflectors and armor designed to absorb the energy of an explosion, and therefore is tested to survive threats of up to 8kg in size. However, the appearance of larger threats, such as the ninety kilogram charge that destroyed a Cougar in Iraq, makes even the M1114 obsolete and has driven the Congress to approve a massive replacement program for all front-line HMMWV vehicles. Perhaps the most important arguments in the sale of new MRAP vehicles is Doug Coffey’s – vice president of communicates at BAE – comment, ‘These are new designs, not spin-offs.’ New vehicles hitting the market designed specifically for anti-mine and asymmetrical warfare are introducing new armor technologies and other indirect protection methods for the vehicle’s crew and passengers. Due to design limitations of already existent vehicles, these new technologies and methods are best applied to brand-new vehicles, and it isn’t a surprise that these are proving to be the most effective in combat.
Hull Bottom Shape & Protection
All new mine resistant ambush protected vehicles have at least one thing in common – a v-shaped hull.42 The v-shaped hull found its first widespread use by South African and Namibian vehicles operating in Rhodesia, or what is now Zimbabwe. A v-shaped hull refers specifically to the inclination of the floor plates to bulge towards the floor, creating what can be called a wedge (and, is in fact, similar to the ‘wedge armor’ used on the Leopard 2A5, in regards to the inclination of the armored plates). The inclined plates don’t give an anti-tank mine or an improvised explosive device a target with a flat surface area, and so the explosion will follow the path of least resistance and will be deflected away from the vehicle. Naturally, the more inclined the plates the more the blast and the subsequent shockwaves will be deflected and the lesser the impact on the crew of the armored vehicle. The volume between the two inclined plates and the floor plates of the vehicle is normally hollow, or used as a gas tank – such on the Merkava tank (as read above). Generally, due to safety concerns MRAP vehicles leave the volume empty, as the potential protection capability of diesel fuel is arguable. It’s important to note that the inclination of the hull bottom will also result in taller vehicles, and therefore the angle at which the plates are inclined should be juxtaposed against the tactical necessities of the specific vehicle being built. Furthermore, v-shaped hulls will increase the weight of the vehicle and therefore highly inclined plates are difficult to adopt on main battle tanks, or other vehicles with specific weight limits, due to the fact that these are normally already built to the edge of said imposed weight limit and height limit. Normally, this will result in a larger RADAR signature. Finally, another important consideration is that vehicles designed from scratch, with v-shaped hulls, will normally also limit the amount of usable internal volume for passengers and cargo, given the already mentioned limits on weight and height.
http://i75.photobucket.com/albums/i291/Macabees/Mine%20Resistance%20Informative/v-shapedhullbushmaster.png
[A line-drawing of the Bushmaster's V-shaped hull.]
The hull bottom’s armor protection can also be designed to maximize the vehicle’s survivability against explosively formed penetrators and shaped charges. Perhaps one of the most important is the elimination of all hatches in the vehicle’s belly. A similar decision was made to eliminate the loader’s hatch on the Merkava Mk 4, to increase protection against top-attack threats – the Merkava Mk 4 is the first modern tank to eliminate the loader’s hatch (with a four-man crew). Although these are two different areas of the tank, the reason behind the elimination of the hatch on the turret roof is the same as that to eliminate the hatches on the hull floor – hatches represent weak points in the armor. Furthermore, the elimination of ammunition stored near the hull bottom also increases a vehicle’s survivability – even if the ammunition is stored in fireproof cases (this comment assumes that the ammunition stored on the floor is single-piece and uses a solid propellant). Apart from these indirect forms of protecting the crew, increasing armor thickness by adding floor plates will help in either stopping the explosively formed penetrator or slowing it down, as to reduce damage inside the tank. Furthermore, in regards to the armoring of the steel pieces that form the v-shaped wedge under the hull, the welding point should be hardened – in fact, the Merkava’s v-shaped bottom plate is a single, bent, layer of steel, instead of two pieces being welded. This is possible for more shallow wedges, but in regards to highly inclined plates the best solution is to simply harden the welding points.
Due to the importance of the integrity of the steel plating, low-carbon steels are preferred over harder steels. Therefore, generally, unhardened steel plates are typically superior for these roles, over armored steels with a hardness value of around 40 HRc (Rockwell Hardness Level). Usually, hardened steels don’t retain structural integrity during penetration or when undergoing impact loads.49 The secondary floor plates, or the plating which provides the floor for the passengers above, is now normally being designed as a multi-layer composite armor – using both steel and an energy absorption layer, such as rubber or even ceramic. Much of the technology being developed for lightweight vehicle armors to defeat armor piercing hard-core small-arms ammunition can be applied to anti-mine protection. Due to the importance of transfer of energy, in regards to the transfer of energy of the mine to the crew, energy absorption layers are extremely important. For example, a simple floor armor could be composed of two spaced steel plates, with a layer of another material to absorb impulsive loads. Since impulsive loads normally occur over short periods of time and are characterized as single events when regarding an anti-tank mine (the mine will explode once; secondary waves put aside), the filler layer can stop or slow pressure waves which have transferred through the bottom steel plate. Recently, aluminum foam has been suggested for use as the inter-layer material. Closed-cell aluminum foam has been found to be superior to rubber since it doesn’t degrade the structural stiffness of the armor and this material also stops or attenuates stress waves moving through the armor. Since the performance of ceramics backed by aluminum foam has been found to degrade, as compared to steel, closed-cell aluminum foam refers to the confinement of aluminum foam behind a steel backing-plate for the ceramic. In regards to floor armor for an armored fighting vehicle, this might not be relevant given that the chances are that the two confining plates will be composed of steel.
http://i75.photobucket.com/albums/i291/Macabees/Mine%20Resistance%20Informative/Cougarwreck.jpg
[Knocked-out Cougar - all the occupants survived.]
Given weight considerations on some vehicles, especially tanks,54 the thickness of the armor arrayed to defeat an explosively formed penetrator is limited. Therefore, lightweight composites are preferred over thicker steel plates. For what it’s worth, two spaced steel plates with an inner layer of aluminum foam will have a superior performance of a homogenous steel plate of equal thickness, especially in regards to wave propagation. Ceramics may be used, but ceramic-metal armors will require higher thicknesses, given that the layer of rubber or aluminum foam will still be needed to attenuate impulse loadings and shock waves. Although certain ceramics perform better when impacted at lower velocities, the perforation of ceramics concerning anti-tank mines is complicated. Although explosively formed penetrators will impact at relatively low velocities (between 1,100 and 1,500m/sec, usually), high speed shockwaves will collapse more brittle ceramics. Therefore, due to its ductility and ability to perform better at higher velocities, aluminum nitride may be a superior ceramic to others as floor armor. The density of aluminum nitride (AIN) is around 3.25 g/cm3,56 as compared to a density of 7.85 g/cm3 for armored steel and 4.5 g /cm3 for titanium di-boride. As a result, aluminum nitride is also relatively light, although not as light as boron carbide. But the use of ceramics should be limited, given weight limitations and the fact that although ceramics absorb the energy of the impact, they do not react well to pressure waves. From these conclusions, perhaps titanium-diboride, boron carbide or silicon carbide may be superior to aluminum nitride in regards to stopping explosively formed penetrators. This should be weighed against the possibility of being targeted by an anti-tank mine with a high-velocity shaped charge and the material’s response to impulse loading induced shock.
These materials are just some out of many, and therefore this paper shouldn’t be approached as an exact guide to decide on armor materials. Nonetheless, the information offers a basic picture at what armor designers attempt to achieve when designing lightweight armor which can serve as protection against explosively formed penetrators or shaped charges originating from anti-tank mines or improvised explosive devices. Finally, armor for ballistic protection is likely to spall, which means that the requirement for spall liners along the vehicle’s floor is augmented.
Other Forms of Survivability & Conclusions
A major threat to the crew itself is the shock of the explosive, which may move body parts – such as the neck – in non-ideal ways, which can result in the neck snapping or broken body parts. Therefore, new armored fighting vehicles are introducing new seats, suspending from the hull floor, which better serve to keep a crew member or a passenger fixed in his position in case of an explosion. These seats should have safety belts with at least four to five harness points and the use of suspended foot-rests is advisable to avoid broken ankles. Vehicles such as IVECO’s Light Multirole Vehicle (LMV), currently in service with the British Army (as the Panther), Spanish and Italian Armies (as the Lince) and Norwegian army, offer enhanced survivability by separating the crew from the chassis through an armored ‘crew cell’. Wheels, suspension components and the engines are arrayed in such a way that during the blast these fragments will fly in other directions, while the large wheels themselves absorb the energy of the blast, and deflectors installed along the wheel’s arc deflect the blast away from the vehicle. These components may increase weight, but the increase in weight is seen as a justified expense given the drastic improvement in survivability. In terms of economic cost, a HMMWV-replacement can cost anywhere between $300,000 and $450,000, while replacements for soldiers will cost anywhere between $200,000 and $1,000,000 (this includes soldiers wounded to the point where they are no longer eligible for combat). The increased price per vehicle is well justified, in other words.
In the future, new technologies will be implemented to increase survivability further, and will help to reduce weight. Such a technology, still in the beginning stages of development, is electric armor. Passive electromagnetic armor – electric armor – is simply two steel plates (or electrodes) spaced apart and attached to an electric battery or generator. When the threat perforates the first plate and touches the second plate a circuit will be completed and the electricity will deform the projectile. This novel armor’s greatest advantage is against long and thin shaped charge jets, as opposed to the thicker improvised explosive devices. This armor is bulky and heavy compared to the thinner armor layer composite armors suggested above and requires substantial electric power, to the point where such armor may not be adequate until the advent of a fully electric ground vehicle. Nevertheless, it’s an idea of what there is to come in the future.
http://i75.photobucket.com/albums/i291/Macabees/Mine%20Resistance%20Informative/suspendedseatsmarder1A5.jpg
[New suspended seats introduced in the German Marder 1A5.]
Fortunately, the rather unfortunate fact that improvised explosive devices are one of the most lethal weapons for an insurgent on the modern asymmetrical battlefield will speed up the development of armors to defend against explosively formed penetrators and shaped charges from the ground. Methods of indirect survivability will also evolve and be introduced into new vehicles, given that the development of these technologies is economical due to the spur in national interests to spend multiple billions of dollars on the emergency procurement of mine-resistant armored fighting vehicles. The vehicles will save lives overseas and will reduce the efficiency of insurgencies in countries currently occupied and in future peacekeeping operations. The natural response will be to increase the size of the threat, but even then today’s vehicles have proven themselves adept to still remain superior to the threat. MRAP-related developments will take precedence over future heavy armored fighting vehicle programs since today’s heavy vehicles will remain tactically viable for at least the next two decades, if warfare continues along contemporaneous trends.
The occupation of Iraq will be known as the war of improvised explosive devices, now that these have caused at least 50% of the combat casualties in Iraq by 2006 and perhaps 70% of all combat casualties up until December 2007. In Afghanistan, improvised explosive devices have claimed up to 30% of all combat casualties of United States forces, and in Lebanon an improvised explosive device claimed three Spanish soldiers in a BMR six-wheeled armored fighting vehicle. Iraq is claimed to be one of the ‘most heavily mined nations in the world’, with over ‘ten million mines in the ground’. Booby trap improvised mines, in Iraq, have been used since Saddam Hussein’s regime and has increased since the beginning of the Coalition’s occupation in 2003 – 40 to 60% of all attacks begin with an improvised explosive device going off. During Israel’s 2006 summer war in Lebanon, five Merkava main battle tanks were knocked-out as a result of the explosion of huge improvised explosive devices under the tank’s belly and it seems as if the Palestinians have begun to employ similar tactics in the Gaza Strip and the West Bank. The threat of improvised explosive devices is not unique to United States forces, as the drive to acquire mine protected vehicles has been shown by many of the nations currently operating in Afghanistan, Lebanon, Bosnia or Iraq. According to Al Qaeda, ‘Explosives are the safest weapon for the Mujahidin. Explosives allow us to escape from enemy personnel and avoid arrest. In addition, explosives hit the enemy with absolute terror and shock.’
http://i75.photobucket.com/albums/i291/Macabees/Mine%20Resistance%20Informative/M1114IED.jpg
[U.S. M1114 up-armored HMMMWV knocked-out by an IED.]
Improvised explosive devices have taken many forms, but one of the most well-known is the explosively formed penetrator (EFP). Regarding shaped charges, the explosively formed penetrator is the part of the liner mass which flows in the opposite direction of the cone at a much lesser velocity. The remnants of shaped charge penetrations into armor are normally the explosively formed penetrator, given that these are made up of the majority of the liner’s mass. However, in the case of explosive formed penetrators used in improvised explosive devices in Iraq and in submunitions around the world the penetrator is purposely forged. Explosively formed penetrators normally have wide diameters, a low length to diameter ratio and have velocities of around 1.3 kilometers per second. The formation process of the explosively formed penetrator is complex and difficult to explain, and it requires high pressure and high temperature, and is influenced by a large number of factors – there are few papers which describe this process. Although explosively formed penetrators do not offer as high penetration as their shaped charge counterparts, or kinetic energy long-rod penetrators, they can perforate the thin roof and belly armor of armored fighting vehicles. It can be expected that the penetration of an improvised explosive device will depend on the quality of construction of the bomb, but they have proved to be lethal enough in Iraq given the previously noted percentage of U.S. casualties in Iraq and Afghanistan. To give an idea, about 5% of all explosive devices used against U.S. personnel in Iraq are explosively formed penetrators, yet they have provided for a third of the fatalities and over 10% of the injuries. A vehicle’s crew can be killed or wounded indirectly, as well, as the blast of an improvised explosive device can launch components of the vehicle into the crew cabin and the bomb’s pressure waves can kill a man.
Most improvised explosive devices are probably crudely manufactured and do not dispose of the quality to guarantee a kill. For example, some improvised explosive devices include roadside vehicle-borne bombs and others may not be powerful enough. Between January and September 2007 there were twenty-five thousand recorded IED attacks in Iraq, of a total of eighty-one thousand. Many of these target Iraqi civilian targets and other attack Coalition personnel, but those relevant to this paper are specifically those designed to defeat Coalition armored fighting vehicles. This threat has led to the recent decision, of the Pentagon, to procure up to 22,000 mine-resistance ambush-protected (MRAP) vehicles, belonging to three different categories. To give an idea of the industrial mobilization effort, Force Protection increased production to thirty vehicles per month in mid-2006 and by July 2007 ramped up production up to two hundred per month to fulfill large orders from various clients, including the US Armed Forces and the Iraqi Army. The company’s work force has expanded from 200 people to almost 1,000! The MRAP market has gone from being worth a few hundred million dollars annually to as much as $10 billion a year. One of Force Protection’s 16-ton Cougar transport truck was struck by a ninety kilogram bomb, which threw the vehicle’s engine over thirty meters away from the chassis and almost destroy the vehicle in its entirety. Even though MRAP equipment is tested against twelve to twenty kilogram charges, the Cougar’s crew survived the ninety kilogram mammoth improvised explosive device! In mid-January, 2008, one of Navistar’s MaxxPro trucks, crewed by four soldiers, was hit by a ‘very large’ improvised explosive device which sent the vehicle airborne – three of the four passengers survived the attack. Navistar is currently supplying the U.S. Armed Forces with 1,900 of its MaxxPro trucks – a deal in May 2007 for 1,200 and a follow-up order in July for another 700 – for a total of $1 billion. Arguably, Navistar’s success is due to the limits of Force Protection’s production capabilities.
The United States is not the only country beginning to acquire MRAP vehicles. Spain is looking to replace its existing armored fighting vehicle fleet deployed in Afghanistan and Lebanon, with urgency. In late 2007, the Spanish Ministry of Defense decided to acquire forty Light Multirole Vehicles (LMVs) from Iveco, an Italian automotive company, for a total of €14.4 million. In January 2008 a decision was made to procure a further forty LMVs, at the risk of slowing down the acquisition of larger MRAP vehicles, for €12.4 million. Furthermore, a third order will be put in soon for another forty vehicles, for the same price tag. These vehicles will replace Spain’s indigenous URO VAMTAC, and Spain is looking to acquire a number of Category II MPRA vehicles, as well – either South Africa’s BAE Land Systems OMC’s RG-31 Mk 5, Force Protection’s 16-ton Cougar or Rafael’s Golan. Due to the loss of a BMR in Lebanon, and the deaths of three of its passengers, the Spanish Army will also purchase a number of brand-new 8x8 vehicles – to be produced in Spain – and the Ministry of Defense is currently choosing between the Swiss MOWAG Piranha V and the French VBIC. Although hardly comparable to the money invested by the United States, Spain is looking at spending between 100 and 140 million euros for 150 urgently required mine protected vehicles, and ultimately procuring around €1 billion worth up to the year 2012. However, to better understand the scope and the ambition of the program it should be taken into consideration that the Spanish government has not yet ended production of Spain’s 219 Leopard 2E main battle tanks, considered the most expensive Leopard to be produced to date. The program originally cost the Ministry of Defense €1.950 billion for 219 Leopard 2Es and 16 Buffalo armored recovery vehicles (ARVs), but costs have spiraled with recent program delays due to the mismanagement of Santa Bárbara Sistemas. The Spanish Army is also beginning to accept new Tiger attack helicopters and Pizarro infantry combat vehicles, while the Spanish Air Force is still being issued new Eurofighter Typhoon air superiority fighters. Therefore, the €1 billion should be seen within the context of Spain’s recent military spending in order to understand the urgency of the issue.
http://i75.photobucket.com/albums/i291/Macabees/Mine%20Resistance%20Informative/ied-cutout01-s.jpg
[Cut-out image of an IED.]
Other countries are also spending money to acquire state-of-the-art mine-resistant vehicles. Perhaps one of the most interesting is Canada’s recent acquisition of twenty Leopard 2A6M mine-protected main battle tanks from the German Bundeswher, while they await the arrival of forty Dutch Leopard 2A6 and forty Leopard 2A4 – the 2A6Ms will replace Canadian Leopard 1C2s in Afghanistan, and at least nineteen will be returned to Germany after their tour is complete. In Afghanistan, the Canadians have experienced around 100 casualties in their light wheeled armored fighting vehicles and twenty-four in new MRAP vehicles. Despite the addition of MEXAS non-explosive reactive armor to the hull of the Leopard 1C2, they were found to be antiquated and insufficient in front of the threat posed by mines in Afghanistan. The Leopard 2A6Ms introduces a new auxiliary power unit (APU), an air conditioning system and a number of increases in armor protection, especially against mines. The United Kingdom’s FRES program may be affected by the new drive to purchase MRAP vehicles, given rumors that the Ministry of Defense may tap into the FRES budget in order to acquire a larger number of armored trucks. In August 2006 the British Army placed an order for 108 of Force Protection’s Cougar transport trucks, and the Ministry of Defense is looking to spend between $40 and $400 million for up to 180 Medium Protected Patrol Vehicles (MPPV). Furthermore, despite the lightweight requirements for Britain’s FRES program, some fear that the IED threat will force vehicles to increase weight in order to counter the threat. Australia, which has deployed troops to Afghanistan, has also invested in the purchase of a number of Bushmaster mine-protected trucks. The improvised explosive device threat is certainly big enough to force nations to put aside existing procurement efforts in order to acquire the best mine-protected light wheeled armored trucks on the market.
Aside from the Leopard 2A6M, most tank producing nations have introduced new urban fighting kits with increased protection versus anti-tank mines and improvised explosive devices. Krauss-Maffei Wegmann (KMW) showcased the new Leopard 2 PSO (Peace Support Operation), with add-on turret and hull armor, a secondary remote weapon station near the loader’s hatch, an auxiliary power unit, panoramic 360º coverage by cameras embedded in the vehicle’s hull, an external radio, a searchlight and a dozer blade. Also shown at the Eurosatory 2006 exhibition was France’s AZUR (Action en Zone Urbaine), for Nexter’s Leclerc main battle tank. In the kit, a remote weapon station replaces the commander’s pintle-mounted machine gun, new appliqué composite panels for the side skirts, and added armor to the engine bay, as well as the application of slat armor to protect the entire rear of the vehicle. Perhaps one of the better urban warfare kits is Israel’s new Merkava LIC, which boasts of added all-around protection and increased hull bottom armor thickness. Furthermore, to protect sensitive items against debris, shrapnel and rocks all air intakes, exhausts and electronics are protected by steel mesh, similar to the Leopard 2 PSO. The commander’s cupola is replaced by a new cupola, which allows the commander greater visibility from a higher position and the remote controlled 12.7mm gun is repositioned above the main gun. Interestingly, a new hatch has been introduced in the rear door, to allow snipers to protect the vehicle’s rear. These may equip Israeli Merkava Mk 3s, while the Mk 4 may receive a separate upgrade. This includes two-axis stabilization of the commander’s panoramic sights, with new-generation FLIR and TV channels. The Merkava was designed, originally, with a v-shaped hull which was hollow between the bottom of the ‘crest’ and the thinner floor plates above – in the first two models this space was filled with fuel, but in the Mk 3 and Mk4 the fuel tank has been eliminated and instead it’s spaced simply with air. On the other hand, some sources indicate that fuel will actually suppress a shaped charge jet (or an explosively formed penetrator) if the fuel tank is self-sealing. Perhaps the most well-known urban kit for a main battle tank is the Abram’s TUSK modification package (tank urban survivability kit), which includes a new thermal sight for the loader, a remote weapon station for the tank commander, explosive reactive armor on the side skirts, a rear protecting unit composed of slat armor, a gun shield for the loader and an infantry phone in the rear. It’s possible that these new reactive armor tiles are similar to the Blazer reactive armor tiles applied to the Bradley infantry fighting vehicles and M60A1 main battle tanks in the early 90s.
http://i75.photobucket.com/albums/i291/Macabees/Mine%20Resistance%20Informative/MerkavaMk3LIC.jpg
[Merkava Mk. 3 LIC; note the sniper hatch in the rear door.]
However, apart from the Merkava, these modifications are only of limited use against improvised explosive devices. As noticed, most increase protection of the tank on the side armor and the rear, prioritizing protection against rocket propelled grenades. However, only the Merkava has effective armor protection on the tank’s belly, with the v-shaped hull, and even this has failed the tank in Lebanon, where it experienced charges of up to 100kg. Furthermore, although the additional floor armor on the Leopard 2A6M might be able to stop the penetration of an explosively formed penetrator, it does not protect the crew from the blast and shock effects – the same is true for Nexter’s anti-TMRP-6 Kpam protection kit for armored fighting vehicles. This is more evident in the recent up-armor attempts on the M1114 HMMWV, which began in 1997. The M1114 features add-on blast deflectors and armor designed to absorb the energy of an explosion, and therefore is tested to survive threats of up to 8kg in size. However, the appearance of larger threats, such as the ninety kilogram charge that destroyed a Cougar in Iraq, makes even the M1114 obsolete and has driven the Congress to approve a massive replacement program for all front-line HMMWV vehicles. Perhaps the most important arguments in the sale of new MRAP vehicles is Doug Coffey’s – vice president of communicates at BAE – comment, ‘These are new designs, not spin-offs.’ New vehicles hitting the market designed specifically for anti-mine and asymmetrical warfare are introducing new armor technologies and other indirect protection methods for the vehicle’s crew and passengers. Due to design limitations of already existent vehicles, these new technologies and methods are best applied to brand-new vehicles, and it isn’t a surprise that these are proving to be the most effective in combat.
Hull Bottom Shape & Protection
All new mine resistant ambush protected vehicles have at least one thing in common – a v-shaped hull.42 The v-shaped hull found its first widespread use by South African and Namibian vehicles operating in Rhodesia, or what is now Zimbabwe. A v-shaped hull refers specifically to the inclination of the floor plates to bulge towards the floor, creating what can be called a wedge (and, is in fact, similar to the ‘wedge armor’ used on the Leopard 2A5, in regards to the inclination of the armored plates). The inclined plates don’t give an anti-tank mine or an improvised explosive device a target with a flat surface area, and so the explosion will follow the path of least resistance and will be deflected away from the vehicle. Naturally, the more inclined the plates the more the blast and the subsequent shockwaves will be deflected and the lesser the impact on the crew of the armored vehicle. The volume between the two inclined plates and the floor plates of the vehicle is normally hollow, or used as a gas tank – such on the Merkava tank (as read above). Generally, due to safety concerns MRAP vehicles leave the volume empty, as the potential protection capability of diesel fuel is arguable. It’s important to note that the inclination of the hull bottom will also result in taller vehicles, and therefore the angle at which the plates are inclined should be juxtaposed against the tactical necessities of the specific vehicle being built. Furthermore, v-shaped hulls will increase the weight of the vehicle and therefore highly inclined plates are difficult to adopt on main battle tanks, or other vehicles with specific weight limits, due to the fact that these are normally already built to the edge of said imposed weight limit and height limit. Normally, this will result in a larger RADAR signature. Finally, another important consideration is that vehicles designed from scratch, with v-shaped hulls, will normally also limit the amount of usable internal volume for passengers and cargo, given the already mentioned limits on weight and height.
http://i75.photobucket.com/albums/i291/Macabees/Mine%20Resistance%20Informative/v-shapedhullbushmaster.png
[A line-drawing of the Bushmaster's V-shaped hull.]
The hull bottom’s armor protection can also be designed to maximize the vehicle’s survivability against explosively formed penetrators and shaped charges. Perhaps one of the most important is the elimination of all hatches in the vehicle’s belly. A similar decision was made to eliminate the loader’s hatch on the Merkava Mk 4, to increase protection against top-attack threats – the Merkava Mk 4 is the first modern tank to eliminate the loader’s hatch (with a four-man crew). Although these are two different areas of the tank, the reason behind the elimination of the hatch on the turret roof is the same as that to eliminate the hatches on the hull floor – hatches represent weak points in the armor. Furthermore, the elimination of ammunition stored near the hull bottom also increases a vehicle’s survivability – even if the ammunition is stored in fireproof cases (this comment assumes that the ammunition stored on the floor is single-piece and uses a solid propellant). Apart from these indirect forms of protecting the crew, increasing armor thickness by adding floor plates will help in either stopping the explosively formed penetrator or slowing it down, as to reduce damage inside the tank. Furthermore, in regards to the armoring of the steel pieces that form the v-shaped wedge under the hull, the welding point should be hardened – in fact, the Merkava’s v-shaped bottom plate is a single, bent, layer of steel, instead of two pieces being welded. This is possible for more shallow wedges, but in regards to highly inclined plates the best solution is to simply harden the welding points.
Due to the importance of the integrity of the steel plating, low-carbon steels are preferred over harder steels. Therefore, generally, unhardened steel plates are typically superior for these roles, over armored steels with a hardness value of around 40 HRc (Rockwell Hardness Level). Usually, hardened steels don’t retain structural integrity during penetration or when undergoing impact loads.49 The secondary floor plates, or the plating which provides the floor for the passengers above, is now normally being designed as a multi-layer composite armor – using both steel and an energy absorption layer, such as rubber or even ceramic. Much of the technology being developed for lightweight vehicle armors to defeat armor piercing hard-core small-arms ammunition can be applied to anti-mine protection. Due to the importance of transfer of energy, in regards to the transfer of energy of the mine to the crew, energy absorption layers are extremely important. For example, a simple floor armor could be composed of two spaced steel plates, with a layer of another material to absorb impulsive loads. Since impulsive loads normally occur over short periods of time and are characterized as single events when regarding an anti-tank mine (the mine will explode once; secondary waves put aside), the filler layer can stop or slow pressure waves which have transferred through the bottom steel plate. Recently, aluminum foam has been suggested for use as the inter-layer material. Closed-cell aluminum foam has been found to be superior to rubber since it doesn’t degrade the structural stiffness of the armor and this material also stops or attenuates stress waves moving through the armor. Since the performance of ceramics backed by aluminum foam has been found to degrade, as compared to steel, closed-cell aluminum foam refers to the confinement of aluminum foam behind a steel backing-plate for the ceramic. In regards to floor armor for an armored fighting vehicle, this might not be relevant given that the chances are that the two confining plates will be composed of steel.
http://i75.photobucket.com/albums/i291/Macabees/Mine%20Resistance%20Informative/Cougarwreck.jpg
[Knocked-out Cougar - all the occupants survived.]
Given weight considerations on some vehicles, especially tanks,54 the thickness of the armor arrayed to defeat an explosively formed penetrator is limited. Therefore, lightweight composites are preferred over thicker steel plates. For what it’s worth, two spaced steel plates with an inner layer of aluminum foam will have a superior performance of a homogenous steel plate of equal thickness, especially in regards to wave propagation. Ceramics may be used, but ceramic-metal armors will require higher thicknesses, given that the layer of rubber or aluminum foam will still be needed to attenuate impulse loadings and shock waves. Although certain ceramics perform better when impacted at lower velocities, the perforation of ceramics concerning anti-tank mines is complicated. Although explosively formed penetrators will impact at relatively low velocities (between 1,100 and 1,500m/sec, usually), high speed shockwaves will collapse more brittle ceramics. Therefore, due to its ductility and ability to perform better at higher velocities, aluminum nitride may be a superior ceramic to others as floor armor. The density of aluminum nitride (AIN) is around 3.25 g/cm3,56 as compared to a density of 7.85 g/cm3 for armored steel and 4.5 g /cm3 for titanium di-boride. As a result, aluminum nitride is also relatively light, although not as light as boron carbide. But the use of ceramics should be limited, given weight limitations and the fact that although ceramics absorb the energy of the impact, they do not react well to pressure waves. From these conclusions, perhaps titanium-diboride, boron carbide or silicon carbide may be superior to aluminum nitride in regards to stopping explosively formed penetrators. This should be weighed against the possibility of being targeted by an anti-tank mine with a high-velocity shaped charge and the material’s response to impulse loading induced shock.
These materials are just some out of many, and therefore this paper shouldn’t be approached as an exact guide to decide on armor materials. Nonetheless, the information offers a basic picture at what armor designers attempt to achieve when designing lightweight armor which can serve as protection against explosively formed penetrators or shaped charges originating from anti-tank mines or improvised explosive devices. Finally, armor for ballistic protection is likely to spall, which means that the requirement for spall liners along the vehicle’s floor is augmented.
Other Forms of Survivability & Conclusions
A major threat to the crew itself is the shock of the explosive, which may move body parts – such as the neck – in non-ideal ways, which can result in the neck snapping or broken body parts. Therefore, new armored fighting vehicles are introducing new seats, suspending from the hull floor, which better serve to keep a crew member or a passenger fixed in his position in case of an explosion. These seats should have safety belts with at least four to five harness points and the use of suspended foot-rests is advisable to avoid broken ankles. Vehicles such as IVECO’s Light Multirole Vehicle (LMV), currently in service with the British Army (as the Panther), Spanish and Italian Armies (as the Lince) and Norwegian army, offer enhanced survivability by separating the crew from the chassis through an armored ‘crew cell’. Wheels, suspension components and the engines are arrayed in such a way that during the blast these fragments will fly in other directions, while the large wheels themselves absorb the energy of the blast, and deflectors installed along the wheel’s arc deflect the blast away from the vehicle. These components may increase weight, but the increase in weight is seen as a justified expense given the drastic improvement in survivability. In terms of economic cost, a HMMWV-replacement can cost anywhere between $300,000 and $450,000, while replacements for soldiers will cost anywhere between $200,000 and $1,000,000 (this includes soldiers wounded to the point where they are no longer eligible for combat). The increased price per vehicle is well justified, in other words.
In the future, new technologies will be implemented to increase survivability further, and will help to reduce weight. Such a technology, still in the beginning stages of development, is electric armor. Passive electromagnetic armor – electric armor – is simply two steel plates (or electrodes) spaced apart and attached to an electric battery or generator. When the threat perforates the first plate and touches the second plate a circuit will be completed and the electricity will deform the projectile. This novel armor’s greatest advantage is against long and thin shaped charge jets, as opposed to the thicker improvised explosive devices. This armor is bulky and heavy compared to the thinner armor layer composite armors suggested above and requires substantial electric power, to the point where such armor may not be adequate until the advent of a fully electric ground vehicle. Nevertheless, it’s an idea of what there is to come in the future.
http://i75.photobucket.com/albums/i291/Macabees/Mine%20Resistance%20Informative/suspendedseatsmarder1A5.jpg
[New suspended seats introduced in the German Marder 1A5.]
Fortunately, the rather unfortunate fact that improvised explosive devices are one of the most lethal weapons for an insurgent on the modern asymmetrical battlefield will speed up the development of armors to defend against explosively formed penetrators and shaped charges from the ground. Methods of indirect survivability will also evolve and be introduced into new vehicles, given that the development of these technologies is economical due to the spur in national interests to spend multiple billions of dollars on the emergency procurement of mine-resistant armored fighting vehicles. The vehicles will save lives overseas and will reduce the efficiency of insurgencies in countries currently occupied and in future peacekeeping operations. The natural response will be to increase the size of the threat, but even then today’s vehicles have proven themselves adept to still remain superior to the threat. MRAP-related developments will take precedence over future heavy armored fighting vehicle programs since today’s heavy vehicles will remain tactically viable for at least the next two decades, if warfare continues along contemporaneous trends.