Spaced armour Armour with two or more plates spaced a distance apart is called spaced armour . When sloped it reduces the penetrating power of bullets and solid shot as after penetrating each plate they tend to tumble , deflect , deform , or disintegrate ; when not sloped it increases the protection offered by the armour because explosive projectiles detonate on it before they reach the inner plates . It has been in use since the First World War , where it was used on the Schneider CA1 and St Chamond tanks . Many WWII German tanks had spaced armour in the form of armoured skirts , Schürzen , to make their thinner side armour more effective against anti - tank fire . Its introduction was to counter Soviet anti - tank units using conventional kinetic penetrator type rounds ( AT rifles ) , not the Bazooka , Panzerfaust , and other HEAT weapons as commonly thought . The principle of spaced armour protects against high explosive anti - tank ( HEAT ) projectiles which create a focus ed jet of plasticised metal , very effective at the focus point , but much less so beyond there . Relatively thin armour plates or even metal mesh , much lighter than fully protective armour , can be attached as side skirts or turret skirts on tanks and other armoured vehicles . This light armour detonates the warhead prematurely so that the jet of metal is focused well before the main armour , becoming relatively ineffective . In response to increasingly effective HEAT warheads , integral spaced armour was reintroduced in the 1960s on the German Leopard 1 . There are hollow spaces inside this type of armour , increasing the length of travel from the exterior of the vehicle to the interior for a given weight of armour , to reduce the shaped charge ' s penetrating power . Sometimes the interior surfaces of these hollow cavities are sloped , presenting angles to the anticipated path of the shaped charge ' s jet in order to further dissipate its power . For example , a given weight of armour can be distributed in 2 layers 15 cm ( 6 in ) thick instead of a single 30 cm ( 12 in ) layer , giving much better protection against shaped charges . Today some main battle tanks carry rubber skirts to protect their relatively fragile suspension and front belly armour . Whereas the material of normal armour is always a compromise between hardness and ductility , spaced armour can also comprise plates with different material properties to increase its effectiveness against kinetic energy penetrators . An example for this construction is the armour of the Leopard 2 tank , which provides a slanted first armour stage ( disturber ) , a specially hardened second stage ( disrupter ) and a softer third stage with high ductility ( absorber ) . The disturber is to ideally deflect or at least manipulate the direction of incoming kinetic energy penetrators , which are then shattered and fragmented when hitting the disrupter . The absorber stage finally erodes and contains spalls and fragments . The Whipple shield uses the principle of spaced armour to protect spacecraft from the impacts of very fast micrometeoroid s . The impact with the first wall melts or breaks up the incoming particle , causing fragments to be spread over a wider area when striking the subsequent walls .