Skip to comments.Even Nuclear Arms Might Not Bust Enemy Bunkers, Scientists Say
Posted on 03/28/2002 12:14:54 PM PST by Stand Watch Listen
Kansas City Star Even Nuclear Arms Might Not Bust Enemy Bunkers, Scientists Say
March 26, 2002
Even Nuclear Arms Might Not Bust Enemy Bunkers, Scientists Say
By Scott Canon, The Kansas City Star
There is good reason the United States put its doomsday command center inside a mountain and its shadow government in subterranean bunkers.
It is the same reason al-Qaida fighters take to caves and that, the world suspects, Iraqi President Saddam Hussein stashes his deadliest weapons underground.
Because even when chased by a military with the most amazing bombs, an enemy on the run or trying to cache supplies can expect that a bunker dug deep enough rarely buckles.
"There's a race on between people who want to hide their stuff or themselves underground and the people they're hiding from," said Robert Hewson, the London-based editor of Jane's Air-Launched Weapons. "Right now, the people who are hiding have the edge."
Simply put, experts in areas ranging from geology to engineering to warfare concur that a low-tech refuge carved sufficiently deep into rock can withstand assault from even the most sophisticated of 21st-century bombs. The government estimates 1,100 such bunkers exist from North Korea to Iraq to hide the nastiest of weapons or the highest ranking of enemy leaders.
In fact, leaks this month suggest that American frustration with cat-and-mouse has the Bush administration contemplating a taboo -- unleashing nuclear firepower on targets previously reserved for conventional weapons.
A draft of the Nuclear Posture Review -- echoing the thoughts of Bill Clinton's nuclear war planners -- calls for the military to study using nuclear weapons against hardened targets in a handful of nations.
"But a nuclear weapon is not a magic bullet," said Steve Fetter, a physicist and public policy professor at the University of Maryland who worked in the Defense Department under Clinton.
Theory and practice
While nuclear weapons represent the most extreme approach, they also show how hard it is to crumple an underground compound.
Experts expect an attack on, for instance, an Iraqi bunker probably would be an earth-penetrating B61-11 -- partly assembled at the Honeywell plant in Kansas City. It would be carried by the B-2 stealth bomber, which flies nonstop to anywhere in the world from Whiteman Air Force Base, Mo.
In theory, that relatively small nuclear warhead's shape and super-hardened steel nose would knife deep into the earth's surface before exploding.
Instead of Hiroshima-style blinding light and mushroom cloud, the energy of this atom-splitting would run out in shock waves through the earth to collapse caves or bunkers.
Or perhaps not.
Princeton University physicist and arms-control specialist Robert Nelson studied how the B61-11 might work in practice. In test drops from a B-2 cruising at 40,000 feet, the bomb usually burrowed 20 to 30 feet in the Alaska permafrost. (It does, however, have a tendency to skip off the ground if it strikes at too shallow an angle.)
But a nuclear explosion at 20 feet underground actually maximizes radioactive fallout.
"The fireball breaks through the surface of the earth, carrying into the air large amounts of dirt and debris," Nelson wrote last year. "This material has been exposed to the intense neutron flux from the nuclear detonation, which adds to the radioactivity from the fission products."
To contain the radiation from a 5-kiloton explosion -- relatively small by today's standards -- such bombs at the Nevada Test Site were buried 650 feet.
"We're back where we started with nuclear weapons," said Stephen Schwartz, publisher of The Bulletin of Atomic Scientists. "The fallout, both radioactive and political, is just too great."
Checking the science
Another physicist looked at what destructive power a buried nuclear bomb could wreak.
"I figured if you buried a nuke, it was going to destroy a lot of stuff underground," said Geoffrey Forden, a senior research fellow at the Massachusetts Institute of Technology's security studies program.
But in preparing an article for Jane's Intelligence Review, Forden needed to check the science first. He combed through decades-old research that explored the use of nuclear explosions to build reservoirs or to clear a channel for a canal across Panama.
Forden used that data to analyze the likely damage to underground bunkers from a bomb penetrating about 100 feet -- five times deeper than B61-11s burrow and well beyond what physicists believe is possible.
"Even a (10 kiloton) nuclear weapon cannot destroy or even damage the equipment in an underground facility buried 300 meters in granite," Forden wrote.
The Pentagon acknowledges the 700-pound B61-11 does not penetrate deep enough to reach some bunkers. It recommends studying whether a 5,000-pound version could do better, although physicists say the existing bomb is already at the limits of how far a projectile could sink into the earth without breaking apart.
Even a bunker less than a quarter-mile underground might survive a nuclear bomb that misses by fewer than 200 yards -- which is quite possible considering the B61-11 comes without a guidance system.
Forden studied the problem posed by the suspected underground chemical weapons near Tarhunah, Libya. The plant is believed to have a pair of tunnel entrances. Which direction those tunnels lead, however, is a mystery.
That means a nuclear bomb might strike the area and still spare the bunker, Forden concluded.
All this strategy is based on the assumption that the bomb would even go off. That is no sure bet.
An earth-penetrating bomb would meet a shock equal to 10,000 times the force of gravity. Consequently, it uses a warhead adapted from the technology used for atomic artillery shells -- they were subject to similar forces when shot from a cannon -- that are no longer in use.
But the package of earth-penetrating shell and atomic warhead never has been tested as a whole. The U.S. has operated under a self-imposed nuclear testing ban for more than 10 years.
A new role
The Bush administration has dismissed suggestions that it is considering anything very new for American nuclear policy. Yet high-ranking officials also have stressed that the United States stands willing to use a range of options to deter chemical or biological attacks.
Stephen Younger, a nuclear-weapons specialist who recently went from a top spot at the Los Alamos National Laboratory to a key policy-making post in the Pentagon, wrote two years ago in favor of a new role for nuclear strikes.
"Some very hard targets require high yield to destroy them," Younger wrote when he was at Los Alamos. "It might be desirable to retain a small number of higher-yield nuclear weapons in the arsenal as deterrents against enemy confidence in the survival of such targets."
Still, many experts said conventional bombs currently may hold at least as good an answer to attacking buried shelters. While ordinary bombs could not be expected to cave in the buried Libyan depot, perhaps if guided by lasers or satellites they could reliably slam shut the entrances.
"Then you just keep watching it to see if they dig it open," said Hewson, the British air weapons expert. "When they do, you just hit it again. Maybe you haven't destroyed their anthrax supplies, but you've put them out of reach."
In Afghanistan, the U.S. military has tried new 2,000-pound "thermobaric" bombs. Instead of packing explosive power, they come as super-charged fire breathers that, when they hit the entrance of a cave or tunnel, can suck out the air from inside and reduce any occupants to ash. A barrier in a tunnel, however, can protect against that sort of attack.
Among those answering the military's call for bunker-busting ideas was Paul Worsey, a University of Missouri-Rolla professor who deals with explosives and engineering as a mining specialist.
Worsey's proposal assumes ground troops can grab the territory over a bunker for at least a few hours. Then, he said, a crew simply could drill a narrow hole from ground level into a bunker, pour in liquid explosives and stand back.
"If they plug your hole, you just blast away the plug," Worsey said. "I suppose the Air Force would prefer to drop something off a stealth bomber, but that approach doesn't seem to solve the problem."
Well, firstly, the GBU-28 can penetrate to 100 feet of earth or more (granted, it's heaver by a few thousand pounds), so there's no reason a nuke couldn't be built to the same specs. Secondly, the author was talking about a miss with a 10 kiloton device, but the the B61 family of weapons can be configured with a wide variety of yields, including 0.3, 1.5, 5, 10, 45, 60, 60, 80, 170, and 340 kilotons. What you lack in accuracy could be made up for in tonnage.
Precisely. This article speaks about a specific (an rather small and lightweight) nuke. He also complains about accuracy, and doesn't mention that the laser guided weapons are nothing more than iron bombs with a laser seeker on front and control surfaces in the back that come as a kit and are "strapped on" during bomb prep. These could be used on nukes as well.
They dropped a couple of these up here. Minus nukes. Permafrost is tough. The way they get through it for mining buried mineral deposits is to drill down using steam points or wash it away with water giants, both involving melting the ice. A bunker under permafrost might be a bad idea for other reasons, but it would be excellent against nuke warheads.
The Guided Bomb Unit-28 (GBU-28) is a special weapon developed for penetrating hardened Iraqi command centers located deep underground. The GBU-28 is a 5,000-pound laser-guided conventional munition that uses a 4,400-pound penetrating warhead. The bombs are modified Army artillery tubes, weigh 4,637 pounds, and contain 630 pounds of high explosives. They are fitted with GBU-27 LGB kits, 14.5 inches in diameter and almost 19 feet long. The operator illuminates a target with a laser designator and then the munition guides to a spot of laser energy reflected from the target.
The GBU 28 "Bunker Buster" was put together in record time to support targeting of the Iraqi hardened command bunker by adapting existing materiel. The GBU-28 was not even in the early stages of research when Kuwait was invaded. The USAF asked industry for ideas in the week after combat operations started. Work on the bomb was conducted in research laboratories including the the Air Force Research Laboratory Munitions Directorate located at Eglin AFB, Florida and the Watervliet Armory in New York. The bomb was fabricated starting on 1 February, using surplus 8-inch artillery tubes as bomb casings because of their strength and weight. The official go-ahead for the project was issued on 14 February, and explosives for the initial units were hand-loaded by laboratory personnel into a bomb body that was partially buried upright in the ground. The first two units were delivered to the USAF on 16 and 17 February, and the first flight to test the guidance software and fin configuration was conducted on 20 February. These tests were successful and the program proceeded with a contract let on 22 February. A sled test on 26 February proved that the bomb could penetrate over 20 feet of concrete, while an earlier flight test had demonstrated the bomb's ability to penetrate more than 100 feet of earth. The first two operational bombs were delivered to the theater on 27 February.
The Air Force produced a limited quantity of the GBU-28 during Operation Desert Storm to attack multi-layered, hardened underground targets. Only two of these weapons were dropped in Desert Storm, both by F-111Fs. One weapon hit its precise aimpoint, and the onboard aircraft video recorder displayed an outpouring of smoke from an entrance way approximately 6 seconds after impact. After Operation Desert Storm, the Air Force incorporated some modifications, and further tested the munition. The Fy1997 budget request contained $18.4 million to procure 161 GBU-28 hard target penetrator bombs.
For a visual depiction of how the GBU-28 works view the grapic produced by Bob Sherman and USA Today on-line.
They have built their own Roach Motel, they check in,but can not check out.
Makes you wonder who's running the asylum.
If that's true then why did most missile commanders in the hardened missile soli control rooms expect to die at their posts ? This author is full of crap.
Secondly, the author was talking about a miss with a 10 kiloton device, but the the B61 family of weapons can be configured with a wide variety of yields, including 0.3, 1.5, 5, 10, 45, 60, 60, 80, 170, and 340 kilotons.
That's correct -- "Dial a Yield" -- and a strange omission.