by David Crane
defrev at gmail.com
It’s been reported that IEDs (Improvised Explosive Devices) account for approx. 70% of all combat casualties in Iraq. Well, there’s a specific type of IED coming out of Iran that’s been wreaking havoc on Coalition troops recently, and against which MRAP (Mine Resistant Ambush Protected) vehicles like the Cougar, RG33, and Golan armored vehicles can’t defend. It goes by a bunch of names, including Explosively Formed Penetrator or Explosively Formed Projectile (or “EFP” for short), Explosively-Forged Projectile, Explosively-Forged Penetrator, Self-Forging Warhead (SFW), and Self-Forging Fragment (SFF). Military defense tech blogs like Defense Tech (DefenseTech.org) and Noah Shachtman’s new site, NoahShachtman.com, have done some good reporting on EFPs.
EFPs are actually quite simple construction-wise, and nothing new. They’re usually comprised of a cylindrical housing that contains an explosive charge behind a concave metallic liner, which is usually made of copper. When the EFP is detonated, the concave copper/metallic disk is transformed into an extremely high velocity copper slug/penetrator (basically a giant copper bullet) that penetrates via said high kinetic energy, utilizing its bullet-like shape to penetrate right through vehicle armor like a hot knife through butter. Needless to say, this physical penetration mechanism makes Explosively Formed Penetrators/Projectiles very hard to combat.
the potential ability of glass laminate armor (a.k.a. glass ballistic laminate armor a.k.a. armored glass a.k.a. bullet-resistant glass a.k.a. ballistic glass a.k.a. transparent armor) to stop EFPs, something metallic vehicular armor can’t do. The glass laminate armor may be able to destabilize the EFP and redirect its kinetic energy laterally along the glass armor laminations via a “spiderwebbing” effect (shattering laterally and vertically). StrategyPage.com compares the glass laminate armor’s stopping mechanism to Chobham armor a.k.a. Chobham Armour, per the following:
“Apparently the glass laminate armor is destabilizing the explosively forged projectile penetrator and redirecting its kinetic energy laterally along the glass armor laminations. This is the principle behind the M-1 tanks chobham armor (a sandwich of metal and ceramic laminates). The ceramic armor is held in a metal armor matrix. As heavy metal "long rod" penetrator or high explosive shaped charge debris streams enter these armor matrixes, they are destabilized. The kinetic energy is diverted laterally from the initial penatrator direction of attack as the ceramics shatter. A plus here is that the chobham ceramics are jostled by the penetrator’s or shaped charge stream’s passage and keep abrading until the attack runs out of energy. Apparently no one has, officially, tested EFP versus glass laminate ballistic armor, so no one knows, officially, if it can do the same thing.”
While a pristine piece of glass laminate ballistic armor will only stop one EFP round (assuming it works “as advertised”, which we hope it does), it probably only needs to stop one, at least until the insurgents adapt to this new ballistic glass defense.
One potential problem that DefenseReview sees with glass laminate armor is weight. This type of armor is not exactly light, especially if you have to surround a whole vehicle with it. Interestingly, I watched an interesting program a few nights ago called The Science of Star Wars that discussed a technology that may provide a superior anti-EFP defense capability in the future, if it’s ever successfully developed in a powerful-enough format. It’s called a “plasma window”, or “plasma shield” which utilizes the fourth state/phase of matter (plasma) to keep out one of the first three states of matter (in this case, solids). A plasma window/shield works by filling a space with plasma (electrically charged, or “ionized”, gas), and then confining it with a magnetic field. Currently, the technology is in its infancy, so scientists can only create a very small circular plasma window. But, who knows what the future holds?