Explosively formed penetrator = shaped explosives?

I've been trying to figure out from media reports whether the recently announced "explosively formed penetrators" (EFPs) are different from the "shaped charges" that have been used by insurgents in Afghanistan for several years (see this story from Scott Baldauf and Ashraf Khan in September 2005, which talks about the adaptation of shaped charges from Iraq.)

So far it sounds like EFPs are a specific type of shaped projectile, and are based on technology which is neither new nor technically demanding. A recent story in Jane's Defense observes that "the knowledge required to manufacture and use EFPs may have become so widespread that Iranian assistance is no longer required" and Wired's David Hambling notes that typically "designs and 'recipes' are likely passed between groups online...giving terrorists a major boost in their arms race against countermeasures." 

Some sources claim that the discovery of EFPs in Afghanistan is proof that Iran is supporting the Taliban against coalition forces. This prompts the question: if EFPs used today in Afghanistan were produced by Iran, does that suggest that the ones used there in years past were of Iranian origin as well? (If they were, that does not mean, of course, that Iranians were supporting the Taliban at that time, since it is possible that arms they sent to Iraq made their way over to Afghanistan or that the weapons were sold by smugglers...the same is true today.)

If you have thoughts on this, let us know in the comments section...

Comments

[Joshua Foust]

I know that Iranian markings on some munitions are being pushed as evidence of involvement (though I have my doubts as to what that actually proves, aside from people buying Iranian arms).

As for EFPs, they are basically just a type of shaped charge - and have been around since at least the assassination of Alfred Herrhausen in 1989.

A normal shaped charge is conical and gets much of its energy from the kinetic force of impacting on an armored surface, while the EFP gets all its energy from the physics of directing and focusing the explosive energy of the device itself.

The strange thing is, EFPs are actually less "dangerous" than a normal shaped charge because they can only penetrate steel as thick as their diameter (larger shaped charges, like those found on anti-tank missiles, can penetrate 6-10x their diameter of armor).

Hope that helps!

[Noah Shachtman]

Carl:

EFPs are a kind of shaped charge, yes.

[John Anderson]

EFPs are not shaped charges in the same sense that a bullet (projectile) is not an entire rifle cartridge.

The EFP is more like the bullet component of a rifle cartridge, whereas the shaped charge acts more like the gunpowder.

Basically, the EFP starts life as a convex sheet of malleable metal (like copper) who lives on top of a cylinder of explosive. When the explosive goes off, the shockwave bends the copper into something that looks like the top of a blowpop. Only this blowpop is moving really, really fast, like 1-2 km/s. At these velocities, solids act like liquids when they are struck, thus the armor penetrating power.