Isegoria

The future of armour — that is, tanks and other armored fighting vehicles — has been bleak for decades, ever since Soviet-made anti-tank missiles wiped out Israeli forces in the Yom Kippur war of 1973, but The Economist looks on the bright side:

Anti-tank missiles and rocket-propelled grenades (RPGs) penetrate armour with a shaped charge. This explodes after the tip of the warhead has sunk into the target. The brunt of the blast is projected straight ahead, forcing a powerful spike of metal, usually copper, into and through the armour. Using steel alone, few vehicles today could carry enough armour to stop even an inexpensive RPG reliably.

To provide added protection, engineers have developed explosive-reactive armour. This involves covering parts of a vehicle with bricks of plastic explosives sandwiched between metal plates. When a warhead hits the outer metal plate, the explosives underneath (also specially shaped) detonate and force the sandwich to rapidly bulge as the plates move apart. This can shear the armour-piercing spike into bits, which are then less likely to pierce the underlying armour.

The Israel Defence Forces, shaken by their losses during the Yom Kippur war, developed an early but effective explosive-reactive armour that kept tank losses exceptionally light during the 1982 Lebanon war. The innovation, however, created a new problem: the explosive bricks generate shrapnel which can kill nearby infantry or civilians. As a result, when America’s Bradley and Stryker fighting vehicles are clad in explosive-reactive armour they are not used in civilian areas.
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Another approach is to use new materials. Steel armour performs well against a powerful, broad blast, but if the energy is focused on a small spot the metal can “melt like butter”, says an engineer with an American manufacturer of armoured vehicles. To cope with that, scientists have developed hard ceramic composites made from rubber and epoxy resins. Unlike steel, they respond to tremendous pressure by snapping. This action can break up a projectile or a shaped charge. A ceramic armour called Dorchester Level 2, used on British Challenger 2 tanks, is reportedly at least three times as resistant to some strikes as the same weight of steel.

The shockwave from a buried “improvised explosive device” (IED) can tear into a vehicle or toss it over. SJH Projects, a small British company, has developed a so-called “stone sponge” material that, fixed to a vehicle’s undercarriage, partially absorbs the blast. XPT, as it is called, is a roughly 2cm-thick sheet of silica particles glued together with a strong, heat-resistant resin. Small pores, visible with a magnifying glass, channel the blast into mazes of micro-chambers. As they are destroyed, the blast-energy is absorbed. It costs about $17,000 to protect a jeep-sized vehicle using XPT, and it only works once. Steve Holland, the owner of SJH Projects, says NATO trials with crash-test dummies show that the material dramatically reduces spine and skeletal injuries.

The other option is to fight fire with fire, something large naval vessels have been hoping to do for decades:

On March 1st an RPG was fired at an Israeli tank patrolling near the Gaza Strip security barrier. A radar system on the tank tracked the incoming warhead, feeding data to a computerised gun that shot it down with a small burst of projectiles. Israel plans to deploy the system, called Trophy, more widely. Daniel Klein, an armaments official at the EDA, reckons that the foiled attack, probably the first of its kind, bodes well for defending military vehicles. An additional benefit, he believes, is that Trophy and other so-called “active protection” systems are lightweight.

I can see terrorists using reactive armor and active protection to cause civilian casualties.

(Hat tip à mon père.)

US Marines have learned lessons from the Japanese nuclear-plant disaster:

The first Marines deployed for ground operations in northern Japan were equipped with lightweight radiation suits and hoods, potassium-iodide pills and handheld radiation detectors. Briefers said that all crew members wore so-called dosimeters to track potential exposure to radiation, and dosimeters were also installed aboard Marine aircraft. At the end of each flight, personnel, aircraft and equipment were scanned for possible exposure. A specialized team prepared daily reports with updated radiological readings around Japan to give military commanders and officials a snapshot of the situation.

According to briefing slides prepared by the III Marine Expeditionary Force’s nuclear-incident response team, Marine teams surveyed a total of 73 aircraft, more than 300 vehicles and major pieces of equipment, and hundreds of personnel.

The exposure of personnel was, for the most part, negligible. But Marine teams identified a total of 25 aircraft requiring decontamination. Stripping down and cleaning aircraft of radiological contamination became a manpower-intensive task.

According to Marines, it took 1,200 man hours to decontaminate one “hot” CH-46 helicopter that had contact with radioactive debris. Certain parts on the aircraft were particularly hard to clean. In some cases, washing down contaminated parts was not enough; some had to be hand-cleaned with industrial wipes.

Chief Warrant Officer 3 John Russell, the squadron’s maintenance chief, said that “hot spots” tended to develop around parts of the aircraft that force compressed air into the engine. He also said that some surfaces, such as paint on helicopter rotor heads, “soaked up the contamination.”

All told, it took a month to decontaminate all the Okinawa-based aircraft. While that meant aviators fell behind in scheduled flying hours, the squadron commander said the lessons drawn from the operation were worthwhile.