Destruction of the cave's mouth was frighteningly complete. The bomb had skipped through the entrance and erupted in a violent spray of jagged steel, blasting the walls and floor into dust. Where there was wood, suddenly just ash and vapor.
Anh Duong was not impressed. Two months earlier, as American soldiers began the perilous mission of flushing terrorists from the caves of Afghanistan, she and her colleagues had promised to build a powerful new weapon to aid in the fight. Unlike typical bombs, which only blow open a cave's entrance, theirs would create a "thermobaric" blast that could billow through underground passageways, around corners, destroying and killing things deep inside.
Success was imperative. American troops, lacking such a weapon, had already begun the dangerous task of attacking the caves on foot. But the pursuit was also personal for Duong in ways that few people knew or understood. She owed this bomb to the United States, by her measure. Yet as she wandered through the wreckage after its first full-scale test, Duong saw nothing to prove that her deadly device could do its job.
"I'm normally a fairly calm and level-headed scientist, sure of my technical experience, but I was nervous. The country needed this weapon so badly," Duong said. "A big blast at the opening of the tunnel didn't tell us anything. I was anxious. I needed to see more."
No one at the Nevada Test Site that day in December understood the ferocity of what they had just done, however, because the evidence wasn't in the test cave. The first hint was on the opposite side of the mountain, where the blast had ripped a steel grate off a ventilation shaft and flung it aside like paper.
The definitive proof, in fact, existed only as computer data, collected by an array of sensors and gauges lining the tunnel from front to back. The blast had thundered deep into the belly, the data showed, and heat and pressure intensified long after an explosion should have died. Most bomb blasts are absorbed by mountains; yet this one had snaked around a horseshoe-shaped curve and launched out the back with enough force to tear a man apart, 1,100 feet from where it began.
The final results took days to calculate, but the conclusion was remarkable and unambiguous: The BLU-118/B was a horrifying success.
As war raged in Afghanistan, and U.S. troops scoured the eastern mountains in search of Osama bin Laden and his followers, Duong and a team of scientists and engineers in Southern Maryland had built the proverbial secret weapon. By jiggering the chemistry in a standard military explosive, they had conjured up a new bomb whose blast could crush bones and rupture organs nearly a quarter-mile away.
Much of the world would gasp. Greenpeace called it inhumane; a Russian geologist blamed it for deadly earthquakes; critics would dub the weapon "thermo-barbaric" - so unfathomably lethal that it should never have been created.
Fulfilling an obligation
But, for Duong, a former refugee from Vietnam who came to the United States in 1975 and studied science in Maryland's public schools and universities, it would fulfill an obligation that she had pledged to repay her whole adult life.
When she settled in Maryland 27 years ago, Duong promised herself she would fight for the principles of her adopted homeland. And now, if all went as planned, the BLU-118/B would slice into a tunnel in the Afghan mountains, unleash the chemically engineered hell that she and the rest of the country's top explosives experts had wrought, and America's enemies would die.
"It was different than anything we had done before," said Duong. "Not making a new explosive; we've done that. But having a purpose - knowing where it was going and what it was going to be used for. This was one of the proudest achievements of my life. Not just professionally, but personally. We were fighting a war. And it was the chance for me to give something back to the country that had adopted me so generously."
The fight didn't begin in a cave, but rather in a leafy residential neighborhood in suburban Alexandria, Va., inside a building that could pass as the local elementary school. There, hidden among the cracked driveways and bikes on the lawns, with no sign outside to indicate what is within, are offices of the Pentagon's Defense Threat Reduction Agency.
'Tunnel defeat weapon'
Lt. Col. Tom Ward arrived there in July last year. The Department of Defense was worried about subterranean nuclear stockpiles in North Korea and had enlisted Ward to develop a "tunnel defeat weapon" that could punch inside caves and clean them out.
Ward had never built a bomb, but he was a veteran project manager and knew the routine. He met with the scientists and the contractors, ran the numbers, prepared a schedule and wrote a proposal to make 10 to 20 warheads that would use an untested thermobaric explosive. The project would take three years, he figured, and cost about $67 million.
All of that happened before Sept. 11 - before the parking lots outside Ward's office were sealed off, and the campus was ringed with jersey walls, and the obscure Defense Threat Reduction Agency was thrust into a leading role in the new and uncertain war on terrorism.
Suddenly, the generals and admirals were demanding Ward's thermobaric weapon - not for blasting nuclear missiles in Korea but to attack al-Qaida and Taliban cave complexes in the mountains of Afghanistan. And they couldn't wait three years, or even three months. They needed it immediately.
A modern bomb consists of four basic elements: the outer casing, the guidance system, the fuse and the explosive "payload." The three-year plan called for detailed studies and testing for each component - impossible now.
Ward scrambled to see what kind of bomb he could make from available parts. For a casing, he chose the BLU-109, an inch-thick "penetrator" made by Lockheed Martin Corp. that can chew through six feet of concrete before detonating - perfect for delivering a thermobaric bomb into a cave. A common laser guidance system from Raytheon Co. could aim it, he figured; a standard fuse would set it off.
He checked again with the scientists and suppliers, tore apart his three-year plan, and on Oct. 11 - four days after the nation went to war in Afghanistan - Ward made a promise to the Pentagon that he wasn't sure he could keep: "You'll have your bomb in 60 days."
"This was completely unlike anything else, changing all the rules," said Ward. "The [original plan] wasn't three years long just to waste time; there are procedures you follow for these things - sub-scale testing, safety qualifications - important steps. Here we had a concept, and we were taking it straight to full-scale production. It was amazing."
But it wasn't a bomb. Ward had a plan for assembling the steel and the electronics, but he still needed a payload - the deadly wallop. There was no explosive in the world that could do what this bomb was supposed to do, and no time to mix and test all the concoctions he had hoped to experiment with. Ward needed an idea, quickly, and he needed it to be a sure thing. He needed the best explosives scientists he could find.
And so he called Anh Duong.
If historians could trace an inspiration, they would find seeds to the Pentagon's modern weapons arsenal bobbing in a small boat off the coast of Vietnam on April 30, 1975, waiting anxiously to jump.
Duong had left Saigon hours earlier. Her parents, who once made a home in North Vietnam, had vowed never again to live in a Communist state, and so they fled just as the North Vietnamese army seized the city. About 50 relatives and acquaintances piled into two helicopters, one flown by her brother, a South Vietnamese pilot, and they were soon on that tiny boat, sidled up to a large South Vietnamese navy ship offering refuge.
The memory still haunts her - standing in line to jump across the gunwales, watching her cousin misjudge the leap and nearly crush his leg between the hulls. Years later, when her children joked about her lack of athleticism, Duong would laugh and say, "Yes, but let's see if you can jump from that boat to that ship!"
"It's just a funny story now, but I replay it over and over sometimes," said Duong. "I've always tried to teach my kids that you don't take what you have for granted, that a lot of sacrifices were made to give us the freedom we have, and the lives we have. It's a miracle that I'm here at all."
Duong was 15 years old. She knew about 50 words of English when her six-month journey around the world began, first to Subic Bay in the Philippines, ultimately to a refugee camp at Fort Indiantown Gap, Pa. She and her parents moved to Montgomery County in late 1975 when the First Baptist Church in Washington offered to sponsor them, even though they weren't Christians.
'I had this ideal'
She learned quickly and soon graduated from Montgomery Blair High School with honors. She enrolled at the University of Maryland and earned a degree in chemical engineering in 1982, also with honors. Newly trained as a scientist, fiercely anti-Communist and determined not to leave her family, she took a job an hour from home at the U.S. Navy base in Indian Head, Md., developing rocket motors at first, then gun propellants.
A slight woman with a broad smile, Duong becomes fiery when she talks about America and opportunity, and the history that has made her appreciate her home with such passion.
"I had this ideal of mine, and I wanted, in some way, to get involved in the fight for freedom, to preserve this great country that had taken me in," Duong said. "Working for the U.S. Defense Department seemed like the right thing. I felt like I could do something good there."
Today, Duong, 42, is the program manager for explosives at the Naval Surface Warfare Center in Indian Head. She is an internationally recognized expert and the focal point for virtually all explosives research in the Navy. She has helped develop nearly a dozen high-performance compounds that are packed into Navy, Air Force, Army and Marine Corps warheads.
And she had what Ward was looking for.
They called it PBXIH-135. It was the formula for an experimental explosive, developed in the early 1990s, that had shown great promise in initial tests but had never made the transition into a full-scale weapon.
The mixture consists of a common military explosive called HMX, blended with a polyurethane rubber. When detonated by a smaller explosion, the HMX molecules convert to gas and create a huge shock wave. Explosives 101.
But a shock wave isn't enough for clearing out underground tunnels. The secret to PBXIH-135 is the addition of a precise mixture of aluminum powder, which burns in the hot gases. Long after the initial shock wave, the burning aluminum sends heat and pressure bounding through corridors and around corners in search of oxygen - thus the term thermobaric, from the Greek words for heat and pressure.
A typical explosion might last a few microseconds and course a few hundred feet down a tunnel. But a thermobaric blast, fueled with aluminum and detonated in a confined space, can last several seconds, release seven times more energy and effect a "functional kill" thousands of feet away.
"The hot pressure gases will squirt into every nook and cranny - up, down, around corners and staircases," said Erwin Anderson, a retired Indian Head scientist who developed the formula. "It is particularly lethal."
All bombs go "boom."
But a bomb loaded with PBXIH-135 will go "BOOOOO- OOOOOOOOOOM."
That was the theory, anyway. No one really knew, because no one had ever detonated one before.
"All the data we had was from tests inside a closed, square chamber here at Indian Head, not inside a tunnel," said Duong. "The risk wasn't that it wouldn't explode. We know how to make blast explosives. The risk was that it would under-perform the current baseline - that after all the work, it would be no better, or maybe worse, than the weapons that are already available. We couldn't be sure."
People who make explosives like to be sure. Sample batches are mixed and discarded; tests are re-tested. It takes years - maybe 10, if you're not in a hurry - to take an explosive from a scientist's brain to the pointy end of a bomb.
Duong had 60 days. The experts at Indian Head would have to do something unimaginable: forgo further tests, disregard standard safety checks, whip up more than 600 gallons of PBXIH-135 and cast it into bombs.
"You don't jump right in and make 500 pounds of a bright idea," said Anderson. "Unless you're crazy."
Arguably the best
Duong supervises what is arguably the most successful and experienced team of explosives experts in the world. Of the 15 explosives commonly used in American weapons today, 13 were developed by the scientists and engineers at Indian Head. Bombs, warheads, flares, rockets - routine stuff in a place where workers don't wear watches because of the risk of a spark.
And an important hurdle had already been cleared. PBXIH-135 was "qualified" by the Navy, and thus deemed safe enough to make into a real bomb. The qualification process also provided data from small tests, some with as much as 20 pounds of material.
Still, the abbreviated schedule called for scrapping years worth of tests, and dismantling dozens of successive steps and performing them simultaneously. Simply collecting the necessary materials in 60 days seemed all but ridiculous.
The team immediately ordered 20,000 pounds of HMX from the Holston Army Ammunition Plant in Kingsport, Tenn. - a staggering one-time order. The plant had to halt production on every other project.
They found two empty bomb bodies at a Navy center in Yorktown, Va., and ordered 11 more from a weapons depot in McAlester, Okla. A lining for the bombs was tested and applied. The polyurethane and aluminum were ordered from commercial suppliers.
"You're talking about filling 2,000-pound bombs with an explosive that had never been used before. Not a simple thing," said Pam Carpenter, a 42-year-old chemist in charge of all of Indian Head's scientists. "You normally would spend six months just developing the protocol - the procedures for loading and transporting. We had a week or two."
The fuse posed another challenge. One beauty of PBXIH-135 is that it is very difficult to detonate - it has to be if it's going to ride through concrete before exploding. But the mixture is so "insensitive" that scientists feared a standard booster explosive wouldn't set it off. Fuse specialist Karen Burrows was dispatched to Fort A.P. Hill in Virginia to start modifying and testing alternatives.
One irony was obvious. As the evening news showed images of veiled Afghan women studying secretly in illegal schoolrooms, a mighty new bomb was taking shape in the United States built largely by American women with degrees in chemistry and engineering.
"Just think of all those women in Afghanistan who were shut off from their society and not even allowed to learn," said Burrows. "It's another example of what makes this country so great. Here, we've been given an education and the opportunity to learn whatever we choose. We were ready and prepared to do this. And so we win."
Nearly 100 employees at Indian Head got involved, driving through the new zigzag of security barriers each morning. After years working in obscurity, many said it was the first time they felt like part of the fight. Every bomb has a mission, but this one had an enemy, even an address.
Motivation a click away
For motivation during their blistering work schedule, they needed only to click on the radio. Two weeks after work began, the United States shifted its strategy in Afghanistan - fewer airstrikes, more raids on the ground. Only foot soldiers could make certain that a cave's innards were swept clean. No other weapon available could do the job.
"I don't think anyone even hesitated," said Duong. Then her voice tightened as she leaned forward with a wrinkled look of disgust on her face. "Thousands and thousands of people were killed," she said, referring to the Sept. 11 attacks. "We all thought, 'By God, we've got to do something.'"
Mixing began in mid-November. Inside giant steel bowls, the ingredients were slowly and carefully blended to the proper consistency, then measured into the tips of empty bombs. The bombs were baked for a week, then X-rayed to check for trouble. The process is not unlike making a giant cake - in a spark-proof bunker behind a 4-foot-thick blast barrier.
Mo Ibrahim, the manager of cast engineering at Indian Head, likens the process to open heart surgery. The mixture starts to harden as soon as the polyurethane is added, so loading the bombs must be done delicately yet expeditiously.
"Once the patient is opened up, you've got a very limited time to operate," Ibrahim said. "You better have everything ready."
The first two patients died. The empties from Yorktown were missing gaskets to isolate the fuse, and the technicians at Indian Head were too rushed to notice. The PBXIH-135 oozed into the fuse housing and cured solid, making the bombs impossible to arm. The remaining bombs were loaded correctly, but the first two could be used only for tests on the ground.
The Air Force waived the tests it normally demands before hanging a new bomb on a $40 million airplane - except one. Technicians weighed and measured the bombs to make certain that they were balanced, and that the guidance systems would work. Permission granted, a batch of BLU-118/Bs was soon off to the Nevada Test Site, even before the new fuses were ready.
By Dec. 14, the day of the first full-scale test, urgency had turned to desperation. Intelligence sources monitoring radio transmissions in Afghanistan a few days earlier thought that they heard the voice of Osama bin Laden offering encouragement to al-Qaida fighters in a region called Tora Bora. The battle there was intense, and press reports suggested that bin Laden was probably in the area. He might even be cornered.
But if he was there, the Americans couldn't get him because all the enemy fighters were deep underground.
Still some uncertainty
Duong and Carpenter were sure their new creation would explode, but unsure of much else.
"One side of my brain told me not to worry, that it will detonate," Duong said. "But the other side wasn't sure. The country needed this weapon so badly, and I kept thinking, 'It better work.' There wasn't time to try again."
The bomb fell from 9,000 feet. Duong and Carpenter watched from a control room littered with television screens and could see the target cave, both inside and out. On one screen, the dart-shaped bomb fell, on another a wooden target waited at the cave's entrance. Eventually, the two images merged, and the BLU-118/B plowed in, dead-center.
When the grate blew off the back of the cave, Carpenter was excited. It was immediate evidence of destructive force, around a bend 1,100 feet away. "I was expecting some smoke and debris, but I didn't think that grate was going to blow off," she said.
But that wasn't enough. Both women walked into the cave soon after the blast, carrying oxygen masks and tromping through the heavy snow that started falling soon after the test. The air was thick and cold and reeked of destruction, and the bomb had blasted a wide new diameter to the entranceway.
But that wasn't enough. The cave was wired with seismographs, pressure gauges, heat-flux gauges, accelerometers - a web of electronics designed to calculate the blast's likely effect on human bodies.
And that was enough. The results are classified, but the official assessment from Ward's office says the BLU-118/B offers "improved lethality."
Duong would characterize it only as "quite effective."
Carpenter said simply: "We're very proud."
A week later, the world found out what the scientists at Indian Head had been up to. A videotape of the test was released by the Pentagon and quickly aired on most national networks. The scientists were hailed as the nation's high-tech warriors - the deadly might of American science.
"I couldn't believe it," Carpenter said about seeing the report on television. "That just doesn't happen much in this business.
But there was an unexpected consequence: Outrage. Almost immediately, critics in Europe and Asia began ascribing characteristics to the bomb that seemed straight out of a horror story - a fictional one at that.
It was a weapon of mass destruction. A nuclear blast without radiation. A "vacuum bomb" that sucked oxygen out of caves. It would, alternatively, asphyxiate people, suck out their eyes or burn them alive.
A Greenpeace official likened the bombs to nuclear weapons and called for their ban. A Russian geologist blamed them for earthquakes that killed hundreds of villagers in the Hindu Kush mountains, a claim American geologists called preposterous.
The bomb's name - BLU-118 - caused some of the confusion. It is a standard military designation, short for "bomb live unit" with a number to distinguish it from others. But the same designation was used during the Vietnam War for a very different weapon: napalm.
The term thermobaric compounded the problem. The Russian military uses it to refer to "fuel-air bombs," a much-derided killer that disperses a cloud of liquid fuel with one explosion and ignites it with a second.
PBXIH-135 is neither napalm nor a fuel-air bomb, but a traditional "single event" explosive, with common ingredients. Even its aluminum fuel is nothing unusual - many standard munitions contain aluminum, albeit not the precise mixture needed to send a blast creeping through tunnels and around corners.
Scientists often joke that no one cared about PBXIH-135 when it was simply called an "internal blast" explosive. But since last fall, when the Pentagon started calling it "thermobaric" and packing it inside something called a BLU-118, it seems the devil himself isn't nearly as frightening.
Doug Elstrodt, a 44-year-old Indian Head engineer responsible for assembling the BLU-118/B, took the phone calls from military lawyers two days before Christmas. They wanted to know just how deadly their new secret weapon was - the ingredients, the physics behind it, how long and hot it exploded.
"It's not a weapon of mass destruction or a vacuum bomb or anything like that, it's just a bomb - a big one that has been engineered to enhance the internal blast effects," Elstrodt said.
The criticism caught the Pentagon off guard. Ward and the Defense Threat Reduction Agency would issue a news release declaring that the BLU-118/B was not nearly as deadly as everyone seemed to think, and assuring that it did not violate international treaties.
Duong and the others were mostly amused. "If they believe the worst, why not let them?" Duong said.
But the role of the scientists and engineers was over by then, the bleary-eyed dash long finished. Ward was back in Virginia, trying to make an even better thermobaric bomb, and the Indian Head scientists were working on new projects - a shoulder-launched thermobaric, for instance.
The rush took months to fade - the urgency of war that these scientists had never known before.
"This was one of the highlights of my career, to be there and know why we were doing this, and then to be able to deliver what the country needed," said Carpenter. "I'll never forget it."
And for Duong, home in Laurel with her husband and four children, the family members who fled Vietnam with her all settled nearby, the satisfaction was even sweeter. She had made a hefty installment on a private debt that she never truly expects to repay.
"The BLU-118/B, to me, is another example of what is wonderful about this country," she said. "At a time that was supposed to be a moment of weakness, the American people worked together - people of all religions and colors and backgrounds.
"We didn't panic, we stayed focused, and in a very disciplined manner, with a specific goal, we built a weapon targeted at a very specific military threat.
"I think it's a prime example of united we stand, united we fall, united we win," she said. "It makes me very proud."
As for the bombs, no one at Indian Head knows where they are. They left on a flatbed truck headed for Texas.
"Our role was finished at that point," said Elstrodt. "They just sort of dropped out of sight."
'We did our job'
On March 2, somewhere in or near Afghanistan, an American F-15E Strike Eagle took off toward the Shah-i-Kot mountains on the country's eastern border, with the United States' newest anti-terrorist bomb hanging from its racks.
American troops were in those mountains waging the war's hottest fight yet, a battle called Operation Anaconda, and the soldiers had found a "tactically significant cave complex" near the city of Gardez.
Gen. Richard Myers, chairman of the Joint Chiefs of Staff, would later say the cave complex was "active."
"Active, meaning ... ?" he was asked at a news conference.
"People," Myers responded.
The cave was tagged with a targeting laser. Then the F-15's computer calculated the height, speed and range and released the BLU-118/B on a trajectory for the entrance. The bomb's fins and airfoils twisted and tweaked a free-falling course to the ground - right to the end of the laser beam.
It missed. The precise details are classified, but the Pentagon confirmed that the bomb missed the cave and detonated early, wasting all of its concussive, earth-shuddering energy above ground. No tremors, no earthquakes, no booooo- ooooooom snaking through underground tunnels and passageways. No dead terrorists.
Duong, Ward and the others won't talk about the drop, and don't know much anyway.
"We did our job, and we feel good about it," Duong said. "The rest is up to the Air Force."
A spokesman for the U.S. Central Command attributed the failure to "the method of delivery." Pilots are still learning how to drop the things.
But the BLU-118/B worked, he said. On that day, the Air Force had nine left.
To view video footage of a test of the thermobaric bomb, visit http://www.sunspot.net/video.