Mideast edition, Sunday, July 8, 2007
ARLINGTON, Va. — Attacks using explosively formed penetrators remained about the same from May to June, a spokesman for Multi-National Force–Iraq said Friday.
Military officials typically do not discuss the number of EFP attacks, but in May, Marine Gen. Peter Pace, chairman of the Joint Chiefs of Staff, told USA Today that there were 69 EFP attacks in April, and confirmed that was the highest monthly total yet.
Known as EFPs, the devices are high-velocity, sophisticated, powerful roadside bombs.
EFP attacks for May and June “remained higher than the historical average,” said Navy Cmdr. David Werner in a Friday e-mail to Stars and Stripes.
Werner did not give specific figures on the number of EFP attacks for both months, but he said there was one fewer EFP attack in June than in May.
Between January and June, EFP attacks represented 2 percent of all roadside bomb attacks, he said.
Recently, Stars and Stripes talked with a panel of experts on how EFPs work.
The experts said EFPs represent a relatively small number of all roadside bomb attacks because they have to be machined with great precision, but have become notorious as a particularly deadly type of roadside bomb.
Contrary to many media reports, the projectile fired by an EFP is not molten, or melted. The projectile is a solid that behaves like a liquid; it has what physicists call “plastic” properties, because of the enormous pressure of the blast.
Glaciers flow much in the same way, with the pressure from all the ice above turning the ice below into a plastic substance.
U.S. government officials have said EFPs are made in Iran but the Iranian government has not been directly tied to EFP attacks in Iraq.
When they hit something, EFPs are up to nine times as powerful as roadside bombs of a similar size made from artillery shells that are rigged to explode, the experts said.
EFPs focus the power of a blast to fire a slug of high density metal about three times as fast an artillery shell fragment.
The laws of physics dictate that the faster something travels, the more energy it has, so if you triple the speed you end up with nine times the energy.
EFPs can fire a slug at such a high velocity because they focus the power of the explosion that launches the projectile.
When an artillery shell explodes, the blast goes out in all directions, but EFPs fire a projectile that is curved to catch the shock wave from the blast exactly the right way.
The shock wave turns the EFP projectile into a flying dart that travels at about 2 to 3 kilometers per second, or as one expert put it, a hammer traveling at Mach 3.
By comparison, a bullet from an M-16 flies at just over 0.1 kilometers per second.
Once the slug hits a vehicle, it punches a relatively small hole in the armor, but it turns everything in its path into metal fragments, creating a spray of shrapnel that often causes multiple casualties, experts said.
