The Blog

Sucking the Oxygen Out of a Cave

During Operation Anaconda, the United States rolled out a new weapon--the thermobaric bomb. It's worse than a Daisy Cutter, and it may have Saddam's name on it.

11:01 PM, Mar 11, 2002 • By VICTORINO MATUS
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LAST NOVEMBER, during the heady days of Operation Enduring Freedom, the U.S. military dropped a 15,000-pound bomb known as a Daisy Cutter on Taliban positions in Afghanistan. The bomb flattened everything in sight for roughly 600 yards. But while the Daisy Cutter's blast occurred above ground, generating an overpressure that caused most of the damage, many reporters described the bomb as a fuel-air explosive.

"That's absolutely incorrect," Robert Hewson of Jane's Air Launched Weapons told me in an article I wrote then on the Daisy Cutter. "This bomb does not ignite oxygen, turning the air into fire."

But two weeks ago in the Shahi-Kot Valley, 90 miles south of Kabul, the United States dropped a bomb on a cave that, in effect, turned the air into fire. The bomb is the BLU-118/B, better known as a thermobaric bomb. It was the first of its kind used in the war, although variations of the bomb have been used since Vietnam (namely, the 500-pound BLU-118 containing napalm).

Here's how your average fuel-air bomb works: A warhead containing a canister of aerosol liquid such as ethylene oxide or an explosive powder is dropped on a target. "A small initial explosive charge bursts this canister at a predetermined height, allowing the contents to form a concentrated explosive vapor cloud. This cloud is then ignited by a second, larger charge, to generate an intense fireball and blast overpressure. . . . Even if the FAE (fuel-air explosive) fails to detonate completely, it will generate a widespread burning effect," says Jane's. "The temperature can be as high as 3,000 degrees Celsius--more than twice that generated by a conventional explosive. The blast wave can travel at approximately 10,000 feet per second."

The Russians used thermobaric weapons during the 1994-1996 war in Chechnya and in Dagestan in 1999. According to GlobalSecurity.org, "conventional weapons could not force out the Chechens and the Russian Army looked for other ways to move them." The Russians ruled out chemical weapons and resorted to "ground-delivered thermobaric weapons." (It is believed that only the United States, Russia, and the United Kingdom possess versions of the thermobaric bomb.)

But the BLU-118/B (which Jane's believes to be the product of the Defense Threat Reduction Agency's Hard Target Defeat Program Office) takes the fuel-air bomb to the next level. First, the warhead is encased in a 2,000-pound bunker-busting bombshell. Rather than exploding over a widespread area above ground, the BLU-118/B penetrates deep into the ground, through concrete barriers, and then ignites everything inside. Says editor Robert Hewson, "The bomb can be delivered by an F-15 or a B-52 or even a B-2. It's a free-falling smart bomb, guided by a laser either from another plane or from the ground and either dropped on top of a cave or in its mouth, depending on the surrounding territory--ideally you want to drop it at the mouth of the cave."

Which makes this an ideal weapon in the current stage of the war. As Major A.C. Roper, spokesman for U.S. forces, put it, "The exact size of the enemy forces occupying a series of cave complexes is not known." And sending the Marines or the Army's 10th Mountain Division into every crawling space in the region could prove costly. So on March 2, as part of the ongoing Operation Anaconda, a thermobaric bomb was dropped on an area where suspected al Qaeda and Taliban forces were thought to be regrouping. But after the bomb was dropped, it was unclear whether the target was successfully hit or not (many suspect the latter).

Not that this would reflect badly on the bomb itself. If a thermobaric bomb successfully hit the mouth of a cave, "it's goodbye to whoever's in that cave," says Hewson. "Even if you aren't hit by the blast, you'd be hit by the falling rubble." In other words, if you aren't incinerated, you'd probably be buried alive. "It doesn't matter. The end result is the same."