In the previous post on this theme I looked at mobility factors but if a military vehicle is to have any utility on the battlefield it must be protected from enemy.
- Defence Science and Technology Laboratory
- Trade Offs and Trends
Threats to a vehicle, and by definition, its occupants come from many sources.
MINES and IED’s
The need to protect vehicles against mines is hardly new but in numerous conflicts the improvised mine, or IED, has been effective and deployed in increasing quantities. Sophisticated off route mines that employ explosively formed projectiles are a dangerous threat and difficult to defeat.
IED’s are complex because of the many variations, some may use commercial explosives or surplus munitions and others may use home-made explosives. They may be linked, have anti tamper devices, command or victim initiated with the trigger being some distance from the charge. The charge may even not be buried but in a vehicle on the side of the road.
This complexity makes them difficult to defeat.
Vehicles may need protection from small arms up to large calibre anti-tank rounds, RPG’s, anti tank missiles and air delivered weapons.
Although showing small arms ammunition only the 1 million frames per second video below is fascinating
The video below shows the effect of a typical man portable anti-tank guided weapon, the Javelin.
and, a 120mm tank round
Direct fire can produce significant spalling on the inside of the vehicle
Typically blast and shell fragments from artillery
Molotov cocktails are still surprisingly effective and with the increasing proliferation of knowledge about how to create high burn temperature mixtures coupled with a greater likelihood of operating in hybrid conflicts in urbanised areas fire should be seen as a key future threat.
Although seen as a lower likelihood it is still critical for armoured vehicles to be protected against the impacts of nuclear, chemical and biological weapon systems.
Electronic attack may be increasingly important and future vehicles begin to rely more and more on electronic systems for sensors, weapons and even propulsion.
To mitigate the effects of the threats highlighted above is a complex business. Ignoring the active means of defence, shoot them before they shoot you, vehicle protection is essentially passive in nature and even if we take the so called active protection systems in account they are still passive in so much that they are initiated in response to an attack.
Steel, aluminium and advanced ceramic composite armours continue to develop, greater protection and decreased weight being the goal. Fabric armours are also an interesting recent innovation and highly advanced materials like graphene show great potential.
For lightweight vehicles composite materials offer an excellent blend of protection and low weight. DSTL and NP Aerospace have developed CAMAC EFP system that instead of using conventional ceramic tiles, packages small hexagonal ceramic segments into a resin matrix that is said to offer much better performance.
An earlier development that looked at composite armour was the DERA/QinetiQ and Vickers Defence Advanced Composite Armoured Vehicle Platform (ACAVP) that used a Fox turret and Warrior running gear mounted on a complete composite hull.
The so called plastic tank was the world’s first monocoque armoured vehicle chassis that used composites instead of metals for load bearing and protection. Advantages included a 15% reduction in weight, reduced thermal and radar signature, improved protection and resistance to corrosion (especially in salt water)
At 24 tonnes it had frontal protection against 30mm AP and 14.5mm protection elsewhere. It is now in the Tank Museum which is somewhat ironic given that it was designed to meet a future 18-25 tonne reconnaissance vehicle, the £6 million ACAVP being a precursor to TRACER.
The demonstrator was designed around a central mission module with driver and commander sitting side by side.
Developed by Corus, Bodycote, DSTL, QinetiQ and the University of Cambridge, perforated Super Bainite steel armour not only improves ballistic performance it reduces weight, comes in at a fraction of the price of conventional armour steel and provides a sovereign production capability.
Flash Bainite makes some very bold claims, stating that it is cheaper, lighter, higher performing and easier to work with than conventional aluminium armour.
To disrupt the molten jet produces by shaped charge warheads DSTL has been investigating electric armour
Upon impact, an explosive warhead shoots a jet of hot copper into the target at several miles per second. Capable of penetrating over 1 foot of solid steel armour, this simple weapon can destroy a modern armoured infantry combat vehicle or tank. Few vehicles could practicably carry the weight of armour needed to resist such impacts, so the MOD’s scientific arm, the DSTL (Defence Science & Technology Laboratory) has been charged with developing a lighter solution.
The result is an Electric Armour system that DSTL claims will reduce the effect of impacts by such projectiles to almost zero.
Developed at DSTL’s R&D facility in Fort Halstead, Kent, the system consists of an outer skin – made from an unspecified high-strength alloy – that can be rapidly electrified to several thousand volts.
When hit by an RPG, the incoming copper jet has to pass through the electrified layers.
DSTL’s Professor John Brown explains how it works: ‘the high speed copper jet is virtually instantaneously dispersed by the powerful fields generated by the so-called ‘Pulsed Power’ System carried by the vehicle. Any residual debris is absorbed by the vehicle’s ordinary armoured hull.’
In a recent demonstration to high level British Army and MOD Customers, an armoured personnel carrier equipped with the system was subjected to repeated attacks, some from point blank range, and suffered only cosmetic damage.
Professor Brown says that the system, which weighs only a couple of tonnes, has a protective effect equal to carrying an extra 10 – 20 tonnes of steel armour
There would seem to be a considerable number of obstacles to overcome to make this militarily practical and resistant to simple countermeasures.
The fundamental problem with exotic composite armour is that they become prohibitively expensive.
Applique armour is simply armour that is ‘added’, or up armouring.
If one looks at pictures of almost any modern military vehicle it will be obvious that up armouring is extremely common.
Modern developments in this area include not only the materials but also how they are applied, modular or tuneable protection kits can be used to tailor protection to suit the threat environment, assist with transport and allow easier replacement in the field.
Used since the emergence of shaped charge warheads spaced armour is a typical add-on for older vehicles vehicles.
The newer rod and bar configurations of the familiar cage armour seeks to physically disrupt the warhead.
The British company Amsafe Bridport produce a lightweight version of spaced or offset armour called Tarian. Amsafe are a traditional manufacturer of aircraft cargo nets, they make the largest cargo net in the world for the A400 for example and in conjunction with DSTL, created Tarian.
Tarian was developed as a UOR for the princely sum of £500k and is a blend of different materials encapsulated in a fabric skin. It is fire proof and offers some ballistic protection in addition to high levels of RPG protection. Tarian is currently used on the Oshkosh Heavy Equipment Transporters and has been tested on a number of other vehicles.
Tarian QuickShield is a rapid replacement kit for damaged or missing bar armour, because it is so lightweight it can be carried as part of a vehicle’s standard equipment and is no in service with the MoD.
The latest version is called Tarian Extreme that has been extensively tested and is said to be 90% lighter than traditional steel bar armour, just as effective capable of being easily repaired in the field and much cheaper.
Amsafe have an agreement with ST Kinetics to use Tarian on its vehicles, the Bronco or Warthog as shown below
Tarian has huge potential, not just for vehicles and forms part of the Textron TRAPSnet system.
With possibly the exception of fabric armour, applique armour adds weight, sometimes a lot of weight. If a vehicle is not designed to accommodate this weight mobility and reliability will adversely suffer.
FRES Scout, is designed to deal with this potential weight growth, a clever move.
Shaping or sloping can increase protection against direct fire and blast effects.
The familiar sloped front and sides of armoured fighting vehicle is designed to increase the effective thickness of armour and present a glancing surface to projectiles.
To protect against mines and buried IED’s V shaped hulls deflect the blast up and around the vehicle rather than providing a flat surface for the blast to act upon.
Deep V shaped hulls has many disadvantages and one technique that is being investigated is to use a chimney to channel the blast wave, no I have not been on the sherry.
A recent Marine Corps Times article said the following;
While the tests’ results remain classified, DARPA officials say the blasts indicate a Humvee equipped with the structural blast chimney provides the mandatory survivability level required of an M-ATV, the lightest version of the military’s mine-resistant ambush-protected (MRAP) vehicles. And it does so at almost half the weight.
Not a universal panacea the Hardwire LLC blast chimney is at least a promising alternative.
SACRIFICIAL COMPONENTS and ABSORBTION
Designing components so that they come away in response to blast, for example, reduces resistance to blast and reduces the likelihood of a large under body explosion flipping the vehicle over. Although the vehicle may be rendered unusable its occupants survive.
Blast absorption matting is commonly used on the floors of armoured vehicles.
Spall linings are designed to protect the vehicles occupants from high speed fragmentation caused by direct fire.
Because they are generally made from aramid, spun glass and other spun or woven fibre materials they provide a great deal of additional protection for only a modest increase in weight and cost. Spall linings are also mostly fire resistant.
DSTL are active in the field of armour research and last year, in conjunction with Ricardo, developed a new lining material;
Spall liners are an arrangement of molecularly manipulated polyethylene, the same material used to produce supermarket carrier bags. The polyethylene is spun into a fibre and compressed tightly; the units feel similar to dense wood, albeit lighter with far higher resilience to ballistic stress.
These were subsequently tested on the Foxhound light protected patrol vehicle.
The materials used in spall liners are also combined with other material to form integrated protection panels.
SEATING and INTERNAL FITTINGS
The careful arrangement of pedals, controls and various internal fittings does not have a great deal of bearing on vehicle survivability but has a significant impact on the survival of its occupants. Blast protected seating that insulates the seat from the vehicles floor, suspending the seat from the roof, has also seen a much greater use.
Filtering chemical, biological and radioactive particles is a simple method of protecting a vehicles occupant’s. Operating inside an enclosed vehicle in high or low ambient temperatures can be debilitating and rapidly inhibit effectiveness so heating and air conditioning are essential.
Active electronic countermeasures are used to prematurely detonate or defeat the trigger mechanisms of mines and IED’s, it is an area that the UK is seen as a leader in although by going low-tech and employing simple pressure plate systems enemy forces can simply negate the many millions spent on these systems.
ACTIVE PROTECTION SYSTEMS
Active systems have tried to create a step change in protection against direct attacks by reducing the need for heavy armour.
A number of systems exist or are in development
Of course, every countermeasure has a counter countermeasure!
Specifically for direct attack, if the vehicle cannot be seen it cannot be shot at, so visual, thermal, electronic and sound signature testing and reduction is an essential part of a vehicles protection matrix.
The BAE Systems Adaptiv IR Camouflage system has recently been demonstrated
Although less exotic the Saab Barracuda signature management system is relatively cheap and in widespread use.
Even RF signature reduction on electrical and electronic connectors and enclosures plays a part.
DEF STAN 59-411 covers electromagnetic compatibility.
Moving to diesel and away from petrol was an obvious means of fire protection but active fire suppression systems are still widely used in engine compartments to protect against oil mist fires and explosions.
Testing is a hideously complex subject to many international and national standards.
The most commonly known is STANAG 4569, this describes Protection Levels for Occupants of Logistics and Light Armoured Vehicles.
The version was released in 1999 and the second revision in 2004 which included fragmentation, grenade and mine blasts.
The levels are described as;
7.62 x 51 NATO Ball (Ball M80) at 30 meters with velocity 833 m/s
Grenade and Mine Blast
Hand grenades, unexploded artillery fragmenting sub munitions, and other small anti-personnel explosive devices detonated under the vehicle.
7.62 x 39 API BZ at 30 meters with 695 m/s
Grenade and Mine Blast Threat
6 kg (explosive mass) Blast AT Mine:
2a – Mine Explosion pressure activated under any wheel or track location
2b – Mine Explosion under centre
7.62 x 51 AP (WC core) at 30 meters with 930 m/s
Grenade and Mine Blast Threat
8 kg (explosive mass) Blast AT Mine:
3a – Mine Explosion pressure activated under any wheel or track location
3b – Mine Explosion under centre
14.5x114AP / B32 at 200 meters with 911 m/s
155 mm High Explosive at 30 m
Grenade and Mine Blast Threat
10 kg (explosive mass) Blast AT Mine:
4a – Mine Explosion pressure activated under any wheel or track location
4b – Mine Explosion under centre
25 mm APDS-T (M791) or TLB 073 at 500 meters with 1258 m/s
155m High Explosive at 25m
Other related standards include STANAG 2920, EN 1523 and EN 1063.
Complimenting STANAG 4569 is the NATO RTO-TR-HFM-090 test methodology for determining Protection of Vehicle Occupants against Anti-Vehicular Landmine Effects. This seeks to look at the occupants not the vehicle.
View the full (and very complex) document here
These should be seen as starting points, not the end of the conversation.
For example, the Foxhound is reported as only having Level 2 protection but given the complimentary design of all the features I think it would be arguably a better place to be than for example, an older design at a similar level.
It should also be noted that availability plays a key role in survivability, if a vehicle is not serviceable because it takes too long to repair or maintain then it doesn’t matter what its protection level is.
Defence Science and Technology Laboratory
The MoD’s DSTL has an active materials research programme run by the Materials and Structures Technology Science and technology Centre (MAST STC) whose objectives are to support in the long term;
- Maximising impact
- Maintaining the UK Defence materials capability
It is an area in which the UK has a strong reputation; Chobham and Dorchester armour were of course developed in the UK.
Its current targets are as expressed as;
Critical materials capabilities: Maintain a UK defence materials capability, including the sovereign Low Observable materials capability, areas where UK industry is not committed to continue supporting but are required for sovereign reasons and ensuring UK sources of strategic materials for defence.
Value for money: with reduced funding, materials are needed which are cheaper, last longer, are more reliable whilst maintaining or improving performance.
Support to current platforms: Providing improved materials, knowledge and materials advice to help sustain current defence capability
Future threats and opportunities: Develop novel materials with performance beyond current requirements to meet future requirements. Reduce technical risk in current and future platforms
Work Package 3.1 is for metallic and ceramic structural and protection materials.
Work package 3.2 is for polymers and composites structural and protection materials.
Trade Offs and Trends
It is obvious but worth saying anyway, in order to mitigate threats one has to implement a range of solutions. Those solutions invariably lead to the need to trade increased protection with other capability areas.
Implementing a V shaped hull to protect against mines and IED’s will generally increase the height and centre of gravity of a vehicle, thus making it less mobile and more likely to have to be driven through vulnerable areas, increasing the chance of it being attacked.
Increasing armour thickness to protect against direct fire will increase weight and thus require a more substantial engine with its increase in fuel consumption, this increase in fuel consumption means putting people who provide that extra fuel into harms way.
There are areas on the margin where improvements can be had for minimal cost but in general every action has a reaction.
A market survey carried out by Defence IQ last year showed that the vast majority (90%) of responders believe IED’s will be a significant future threat with Heavy Machine Guns and RPG’s following closely.
One day, vehicle designers may well have to deal with laser beams and plasma rifles but that will be no more complex than it is today!