Charge of the light brigade
Charge of the light brigade
Huge magnetic pulses could replace tonnes of armour plating in tanks
TANK armour that destroys enemy missiles with massive electromagnetic fields is being developed by government scientists in the US and Britain. Tanks fitted with this "smart armour" would be much lighter, making them easier to transport rapidly to far-flung war zones.
The biggest threats to tanks in battle are rocket-propelled grenades and anti-tank guided missiles, says Mike Zoltowski of the US Army Research Laboratory in Aberdeen, Maryland. Both use explosive devices called shape charges - hollow copper cones built into the missile's warhead. Explosives packed around the outside of the cone detonate on impact, squashing the cone and forcing a fine jet of copper out of the front of the shell at more than 9 kilometres a second. "When it impacts the armour, the forces generated are enough to push it out of the way and penetrate through it," says Zoltowski. "If it gets through the armour and into the vehicle . . . it causes big problems."
Chris Foss, editor of Jane's Armour and Artillery, says a shape-charge jet can punch a hole through tens of centimetres of steel. So to withstand an attack, key areas on tanks are cladded with around 80 centimetres of steel plating. "This is a significant percentage of the weight of the vehicle," says Zoltowski. "What we want to do is make this lighter, so we can go from a 70-tonne vehicle to a 20-tonne vehicle."
Tanks are often moved to war zones by heavy transport aircraft, so the planes will be able to carry more tanks. The quest for lighter tanks prompted Zoltowski to look at alternatives to traditional heavy armour. His smart armour consists of tiles built of a sandwich of various materials. On the outside of the smart armour is a thin fabric coating to protect against accidental damage that could be caused by flying debris or even tree branches. Beneath this protective layer is a mat woven from optical fibres. This mat sits on a thin outer sheet of standard armour plating.
When a missile strikes the tile, it breaks the fibre-optic mat and then detonates as it hits the armour plating behind. Sensors that monitor light passing through the fibre-optic mat detect the breakage and immediately release a huge electric current stored in capacitors aboard the tank.
Current from the capacitors is channelled to a wire coil that sits directly behind the outer armour plate. This rapidly generates a huge magnetic field just as the high-velocity shape-charge jet is forming (see Diagram). Zoltowski says that if the field created is powerful enough, it will induce electrical currents in the copper jet.
"If you get enough current into it, you can heat it up and start pinching it in certain regions, making it unstable," he says. Ultimately, Zoltowski says the magnetic field will be able to break up and scatter fragments of the jet, robbing it of the power to puncture a hole in the final layer of base armour.
The researchers will not talk about specific design details, such as the thickness of the armour, but Zoltowski believes that the circuitry can react quickly enough to stop a missile. If the armour works, it'll make a big difference on the battlefield.
"At the moment, if you want to try and take out a tank, you use a shape charge," says Foss. In steel, these charges will penetrate up to nine times their diameter. "If you can disrupt it so it's not concentrated on one point, it's a plausible approach," he says. "The benefit is that you wouldn't need 800 millimetres equivalent of steel armour."
