December
31, 2008: The U.S. Marine Corps is buying additional armor kits for 196 of its
Cougar MRAPs (Mine Resistant Ambush Protected) vehicles. This will protect the
vehicles from explosively formed
penetrator (EFP) weapons. Last year, about five percent of the Coalition combat
deaths in Iraq, and about eleven percent of those killed by roadside bombs,
were because of EFPs. This year, EFPs have become much less of a problem,
partly because fewer have been used, and partly because there are more vehicles
out there with the additional armor..
The
EFP is nasty because it can penetrate the armor on just about anything but an
M-1 tank. An EFP is a precision weapon,
a cylindrical device, that is often described as similar to a coffee can. But
the cylinder metal must be thicker. You fill about 60 percent of the
"coffee can" with explosives (C4, also known as plastique, will do).
Then you insert a detonator on the closed end of the "coffee can" and
a concave copper plug that is pushed into the plastic explosive. The tricky
part here is that the depth of the concave copper part, and the thickness of
the copper, have to be just right. It requires someone expert at math and the
chemistry of explosives to make those calculations. When you make a mould for casting the copper plug, you must make sure you get the thickness just
right. The more precisely the copper plug is made, and the EFP assembled, the
more armor the device will penetrate, and the more damage it will do inside the
target vehicle.
The additional side armor for defeating EFPs
consists of 18mm plates constructed of several layers of different materials.
This material, which costs about $2,000 per square foot, breaks up the EFP
molten copper "warhead" that an EFP produces to slice through
conventional armor. For the six wheel Cougar, the EFP armor kit weighs 2.5
tons, and costs $152,000. By adding this
side armor to an MRAP, most EFPs can be defeated, usually with fatal
consequences to the attacker, who is quickly fired on by the troops in the
MRAP, and other vehicles in the convoy. Last year, about 300 MRAPs were
equipped with this side armor. These up-armored models are used in areas most
likely to encounter EFP attacks.
Cougar
is a 12-19 ton truck that is hardened to survive bombs and mines. The Cougar
comes in two versions. The four wheel one can carry ten passengers, the six
wheel one can carry 16. All but four of the 196 EFP armor kits are for the six
wheel version. The Cougar uses a capsule design to protect the passengers and
key vehicle components mines and roadside bombs. The trucks cost about $730,000
each, fully equipped. The Cougars have proved very popular with the troops, but
the additional weight makes the vehicle difficult to handle on many dirt roads
in Afghanistan and Iraq. The road shoulders collapse under weight, and the high
center of gravity typical of MRAPs can lead to a roll over.
