Behind the Iron Curtain

A lot of attention has been paid to the threat IEDs and EFPs pose to Humvees in Iraq and Afghanistan. Heavier armor, jamming of cell phone signals, the CROWS weapons mount and “Rhino” countermeasures have all worked to make Humvees more survivable in an IED environment.  Also, moving from Humvees to MRAPs for some missions has increased troop survivability.

Still, IEDs aren’t the only threat Humvees and similar vehicles face. One of the most common weapons on the battlefield is the RPG, or Rocket Propelled Grenade.  An RPG is a pretty simple weapon. It’s basically a HEAT warhead with  a rocket motor to push it along, all fired from a simple tube. Our guys use a similar weapon,  the AT-4, which is a disposable, one shot weapon. The RPG is reloadable.


The RPG is a real threat to light vehicles like Humvees, MRAPs, and even Strykers and Bradleys. Its HEAT warhead can penetrate the armor of just about any armored vehicle short of a main battle tank like the M-1. An RPG hit on a Humvee will often result in death or injury to the entire crew and a catastrophic loss of the vehicle.

So how do you defend a vehicle like the Humvee from RPGs? They are too small to carry explosive reactive armor or an anti-RPG cage. You can’t keep adding additional armor. The chassis just won’t take that much weight.

Well, for a couple decades, the armies of the world have been exploring “active defense” against RPGs (and similar HEAT warheads). Using a radar sensor to detect an incoming round, the active defense would instantly and automatically react to fire a projectile to impact with the warhead.  Two big problems have always existed with this. One, the sensors and controls just haven’t been practical until the recent improvements in electronics. Secondly, having a vehicle that routinely has troops (and innocent bystanders) nearby suddenly start shooting off explosives is kinda unsafe.  Recently, Artis LLC, in conjunction with the Defense Advanced Research Projects Agency (DARPA) came up with a system called Iron Curtain that uses a combination of advanced sensors, downward firing countermeasures, and special explosives and projectiles to field a system that can defeat RPG rounds without posing a great risk to dismounted personnel.


The system probably won’t be ready for service for another year or so, but can potentially be a great aid in saving the lives of troops.

Here’s a mushroom cloud for your Friday enjoyment

EOD (Explosive Ordnance Disposal) found a whopping 4ooolb IED in Afghanistan. Here you get to see them destroying it with .50cal machine gun fire. We like to see things go boom. We just don’t want our guys to get hurt doing it.

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H/T: Right Wing Video

Tow Missiles and EFPs

We’ll get around to doing a fuller history of the TOW missile, but here’s a taste for now.

What you see is a TOW2B missile attacking a Soviet built tank on the test range. You will notice the missile never hits the tank, but rather flies over the tank. When it is directly overhead, two warheads detonate, both flinging an EFP towards the top of the tank, where historically the armor is thinnest.  You see the missile warheads go off, followed almost instantaneously by the ammo and fuel inside the tank detonating. That’s why the turret goes flying off.


Here’s what a regular HEAT warhead on a earlier TOW does to a Bunker.


More on EFPs

While our previous post on EFPs focused primarily on the improvised weapons provided by the Iranians to the insurgents in Iraq, that is hardly the only use of them worldwide right now. The BLU-108 is a submunition designed to fit inside various weapons. Currently the Senor Fused Weapon (SFW), a cluster bomb unit, and the Joint Stand Off Weapon (JSOW) carry the BLU-108. This marketing video shows how the weapon works.


In the video, you saw a good example of the curved plate that is used to forge the penetrator. The crimping around the edge of the plate is designed to fragment and provides  effects against softer targets like surface-to-air missile systems. There are a couple segments where you can see the penetrator forming and lancing through the armor.

During the 2003 invasion of Iraq, a B-1 bomber dropped a SFW against a column of 18 Iraqi tanks. Every tank was destroyed or disabled.


I found this video while looking for the first one. It shows the component used to make improvised EFPs. While not terribly high tech, the machining required to produce that many plates points pretty clearly to outside (Iranian) support to the terrorists.


What’s an EFP?

Update: Welcome, Conservative Grapevine readers. I hope you will look around. If you have a question, just ask. My goal here is to  help you understand how the Army works.

You’ve seen on the news how Iranian made EFPs are being used as roadside bombs to attack US vehicles in Iraq. But what is an EFP?

Early IEDs in the Iraq War were mostly artillery shells wired to explode. The first Humvees in Iraq had thin armor that would not protect very well against nearby explosions. As up-armored Humvees became available, these early IEDs lost some of their effectiveness. The insurgents reacted in two ways. First, they used bigger IEDs, wiring together several artillery shells at once. The larger blast was more effective, but took longer to emplace and were easier to spot. The second technique, using EFPs, is more difficult to counter.

EFP stands for Explosively Formed Penetrator. Using the concept behind a shaped charge, a disc of metal on one end of a charge can be blasted in the direction of the target. The charge is usually a steel pipe, 6-8″ in diameter. When detonated, the concave disc is deformed by the explosion, and reformed into a slug. The explosion pushes this slug at phenomenal speeds- up to Mach 6.

One of the biggest advantages of EFPs is standoff. The damage to the target isn’t caused by the explosion, but rather by the slug it fires. This means that the EFP doesn’t need to be right next to the roadside to be effective. This means that US soldiers have to scan a much larger area to detect IEDs.

An EFP can usually penetrate as much armor as the diameter of the charge. That is, a charge 6″ in diameter should be able to penetrate 6″ of armor, more than enough to defeat the armor of any Humvee, and indeed, all but the most heavily armored tanks.

Clearly, the threat posed by EFPs is one of the reasons that the US is putting so much pressure on Iran to stop equipping insurgents. Other countermeasures have included focusing on raiding bombmakers.

Update and Bump:

Because the EFP fires a single slug, timing the explosion is critical. Too soon, the slug goes in front of the vehicle. Too late and it misses behind. To get around this, the insurgents are using a cheap passive infrared sensor, sorta like an electric eye. When a Humvee passes in front of the sensor, off goes the EFP and destroys the vehicle. Ahh, but it didn’t take long for the US to come up with a countermeasure. You can see in the photo below a “Rino” device, designed to trigger the EFP before the Humvee reaches the kill-zone. Normally, it would be lowered so it is in front of the Humvee.

An unsuccessful EFP attack can be seen here.