The Washington Post December 13, 2001
Concrete-Piercing Bombs Hammer Caves
By Vernon Loeb
The Air Force is using a new generation of bunker-busting bomb technology to attack al Qaeda's cave and tunnel complexes in eastern Afghanistan, combining advances in penetrator warheads, fuses and precision guidance systems.
The fusion of these technologies enables U.S. air crews to target caves and tunnels in all weather conditions and guide bombs capable of penetrating reinforced concrete walls on either horizontal or vertical trajectories, depending on the target.
"I'm not on the ground and the war is not over," said John Pike, director of GlobalSecurity.org, a defense and intelligence think tank in Alexandria. "But all of this talk about tunnels and dugouts has been a lot more daunting to the television graphics people than it has been to the targeteers and weaponeers." The bottom line, Pike said: "Tunnels are not a good place to hide."
The latest weapon just made available to air commanders in Afghanistan, according to Frank Robbins, director of the Air Force's precision strike systems program office at Eglin Air Force Base in Florida, is a new version of the air-launched cruise missile that incorporates improvements in four key areas: fuse, warhead, guidance system and software that determines trajectory.
The Pentagon is also dropping conventional blast-fragmentation bombs, which kill troops and destroy above-ground facilities, as well as the massive "daisy cutter," a 15,000-pound bomb originally designed during the Vietnam War to clear helicopter landing zones. The weapon detonates three feet above the ground.
The new penetrating cruise missile, called the AGM-86D, carries a warhead that doubles the penetrating capability of earlier munitions. It is also equipped with a new fuse capable of counting the number of concrete floors it has penetrated before detonating at a programmed depth.
The smart fuse is also being used on other bunker-penetrating weapons that have been dropped on al Qaeda caves and tunnels, according to an Air Force weapons expert.
One of them, the GBU-28 "Bunker Buster," is a 5,000-pound bomb that uses a laser-guidance system for precision targeting. The Air Force's largest penetrating weapon, the GBU-28 was developed during the Persian Gulf War a decade ago because of concerns about underground Iraqi complexes and was first dropped with devastating effect during the final hours of that conflict.
An additional guidance system using signals from Global Positioning System (GPS) satellites has been added over the past two years, giving the bomb the ability to operate effectively even when there is heavy cloud cover.
"We have combined these penetrating munitions with precision in a way that we hadn't done before," said retired Gen. Merrill McPeak, Air Force chief of staff from 1990 to 1994. "We are much better positioned now to attack these targets from a munitions point of view."
Another bunker-penetrating munition dropped on caves and tunnels in Afghanistan that can be equipped with both the new penetrating warhead and smart fuse, the AGM-130, is a 2,900-pound, rocket-propelled bomb fired by F-15E strike fighters up to 40 miles from its target.
While the bomb has its own video camera, a GPS system has been added for all-weather capability, which is critical as winter approaches in Afghanistan.
In cloudy weather, Robbins said, GPS signals would guide the bomb through the clouds. Then a crew member in the back seat of the F-15E can use the bomb's camera to "steer it into the window of the target."
The ability to guide these weapons horizontally, Robbins said, can be particularly useful when targeting hardened facilities with entrances and exits. But the latest in "shaping trajectories," Robbins said, is new software that can send penetrating munitions into steep, vertical dives directly onto the tops of their targets in a way that "significantly increases" penetrating capability.
All of the bunker-penetrating bombs -- the AGM-130, the GBU-15, the GBU-24 and the GBU-27 -- can be equipped with a new cap, an elongated spike made of nickel-cobalt steel alloy that doubles the puncturing capability of the warhead.
How deep the new warhead can penetrate is classified. But during a 1996 test by the Air Force, a prototype pierced 11 feet of reinforced concrete, the equivalent of more than 100 feet of soil.
The warhead could conceivably penetrate even farther than that, when launched with new software on a vertical trajectory and equipped with a smart fuse that uses a device to sense whether it is traveling through dirt, concrete or the air between floors of a structure. It can be programmed to detonate at specific levels of an underground structure.
The Air Force has also just begun production of a fuse that can be programmed at various detonation delays by an air crew in flight depending upon the type of target. The standard electronic fuse used on most penetrating weapons can only be set with a preselected detonation delay.
"We've always before sort of contented ourselves with thinking we could seal up the cave -- bomb the rock just above the opening and hope it would fall in," McPeak said. "Now we have munitions that can detonate deep inside the cave -- they'll seal it up, but they'll end [up] doing a lot of damage that they never did before. That's a big jump in capability."
Copyright 2001 The Washington Post
