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INTRODUCTION

The skeletal remains of the Tule Lake Lift Bridge wobbled uncertainly against the gray Texas sky. For the small huddle of hard-hatted men watching tensely nearby, it was a very long 50 seconds. Weeks of painstaking work and hundreds of thousands of dollars were riding on a network of small explosives timed to strategically slice the supports of the bridge’s two remaining towers.

The intended outcome was for the 15-story structures to topple away from the busy waterway and crumple onto a target area of land. “Oh, c’mon,” groaned one of the “blasters” as the towers appeared to lurch toward the water. But then, just as planned, the towers collapsed into twisted steel ruins on both sides of the Corpus Christi Inner Harbor.

The demise of the Tule Lake Lift Bridge is just one of a number of demolition dramas played out every week on The Detonators, a Discovery Channel series that premiered on January 28 (Figure 1). Although every story ends with an explosive payoff, the bulk of the program explores the complicated science of reducing engineering marvels to rubble with surgical precision.

The opportunity to get viewers “beyond the boom” of explosives engineering was a primary reason that Braden Lusk, assistant professor in the Department of Mining Engineering at the University of Kentucky, signed on as co-host of the show (Figure 2). “A lot of people are interested in blowing things up, but a very small percentage understands the necessity for using explosives,” he said. “This gave us a chance to highlight that using explosives is often the safest and most economical way to get things done.”

The Detonators focuses exclusively on explosives demolition—the building implosions and structure destruction that tend to make the evening news. Although high in public recognition, explosives demolition accounts for less than one percent of the 6 billion pounds of explosives used in the United States every year.

According to the 2007 Minerals Yearbook published by the U.S. Geological Survey, coal mining consumes about 66 percent of U.S explosives, with quarry and nonmetal mining coming in a distant second at 12 percent, and metal mining taking up about eight percent. Explosives engineering also plays an important role in research related to the blast mitigation properties of materials used in construction and in the military.

For those intrigued by this wider world of explosives engineering, Paul Worsey, the second half of The Detonators hosting team and professor in the Department of Mining Engineering at Missouri University of Science and Technology (MST), has created a “smorgasbord” of explosive experiences at his wildly popular Summer Explosives Camps.

Geared to high school students who have an interest or aptitude in engineering, the camps offer six days of pyrotechnic learning that balance lectures with memorable handson activities, such as igniting a “wall of fire” (Figures 3–5). Students also take field trips to mining and blasting operations and treat their parents to a fireworks display of their own creation on the last night.

Worsey said that the first camp in 2004 hosted three high school students who had initially signed up for a summer mining engineering program. Because of scheduling confl icts, most of the faculty was unavailable for the session, so Worsey quickly put together an “explosives camp” covering the same basic principles that he taught in his university-level explosives classes. The impromptu camp was a hit, and the program now runs three times a summer with 20 students in each session.

While there is no denying the allure of a summer vacation spent blowing stuff up, Worsey said that the underlying purpose of the camp is to muster new recruits to mining engineering in general, and MST’s program in particular. Worsey said that the screening process for the camp is “rigorous”— students must submit a résumé, a letter of recommendation, and an essay on their explosives engineering aspirations— to ensure that those selected for the camp are equipped to succeed in MST’s engineering programs, should they ultimately choose to study there.

Giving these bright teenagers a real eyeful (and earful) of the fun of engineering seems to be working. Since the program’s inception, approximately 2/3 of the campers have enrolled at MST. More than 25 percent of the current freshman class in MST’s Mining Engineering program attended Explosives Camp, while the majority of campers enrolling in other departments have opted for explosives engineering minors, an opportunity unique to MST. “In fishing terms, it has been the ‘chartreuse lure’ for the mining engineering program,” Worsey said.

Lusk, who had Worsey as his Ph.D. advisor, said he’s not surprised at the success of the MST Explosives Camp. “I loved working with him when I was a student,” he said. “In engineering school, you have a lot of classes where all you do are calculations. His big thing is showing you how to apply what you learn. “Paul is very good at using the ‘bangs and booms’ as bait for students,” Lusk continued. “Even if they don’t end up in explosives, they see the possibilities for science and engineering as a career.”

GETTING THE SCIENCE RIGHT

While The Detonators doesn’t offer the Explosives Camp’s range of experiences, Worsey employs the same hands-on teaching approach to help viewers understand the science behind the big bangs. Each episode’s main demolition story is paired with a segment in the MST blasting research lab where Lusk and Worsey present the right and wrong way to address that particular project’s engineering problem.

An attempt to cut a car in half with explosives, for instance, prompts discussion on the preparation needed for linear-shaped charges. In demolitions, shaped charges are used to cut the steel supports of a structure to cause an inward collapse, or as in the case of the Tule Lake Bridge towers, to topple it to a specific target area.

A key component of the shaped charge is a Vshaped liner made of a dense, ductile metal, such as copper. The liner is surrounded with an explosive that, when detonated, squeezes the metal together to form a blade, while also forcing it through the steel at five times the speed of sound. Since the blade can generally only cut its own length, the steel has to be weakened with strategic cutting so it fails on cue. Collapsing too early or too late could mean the structure is left standing, or worse yet, could fall in the wrong place. “It’s like a big game of Jenga,” said Worsey. “You keep pulling pieces out without the structure falling down until you need it to.”

Helping viewers see beyond the mayhem of Hollywood’s vision of explosives is a point of one of Lusk’s favorite “blasting lab” experiments (Figure 6). Upon Worsey’s gleeful shout of “Fire in the hole!”, a column of concrete reinforced with steel rebar is detonated, its hurtling remains obliterating a Styrofoam ™ “witness panel” positioned six feet away.

A second column is then wrapped in a cocoon of chain link and geotechnical fabric, a synthetic fiber textile commonly used to construct roads and reinforce embankments. The fabric and metal together smother the debris of the subsequent blast, with just a few stones spewing out of the top of the mummified column. “I thought this really demonstrated what is done to protect the property near a blasting zone,” said Lusk.

Getting the science right, according to Lusk, can be a challenge at times to technical advisors on programs such as The Detonators. “It’s very difficult trying to explain something that you have studied your entire life in 45 minutes,” he said. “And, sometimes what you pick as the more important points doesn’t end up in the final product, because it doesn’t fit the story. You have to be prepared to not be in control.”

Although all the stories on The Detonators end basically the same way, there are moments when things don’t go exactly according to script. When a hotel in Florida is imploded, for instance, the steel structure falls away, but the concrete core stands stubbornly intact. Showing this side of science—and how the professionals involved deal with it—is a good thing, according to Lusk. “I think people get the impression that this type of work is easy, because you rarely see something go wrong,” he said. “What makes you effective at your job is how well you manage those unexpected issues.”

That ability to expect the unexpected is a significant contributor to the success of any explosives demolition operation, Lusk continued. “There are not really any quantitative tests that you can do ahead of time. You find out a lot when you start preparation on the building,” he said.

“That’s when you determine how strong the concrete is or if there are steel I-beams in the middle of a concrete column. You make decisions depending on the strength and, in the case of steel, the physical dimensions of the building materials.” The blasting plan can become quite problematic, Lusk said, when buildings have more than one kind of construction technique or when steel and concrete are combined.

“The ‘boom’ part is exciting,” said Worsey. “But the prep work can be painstaking and boring (Figures 7 and 8). Then, there’s always the chance that something will go down in a way you didn’t predict—Are you as good as you think you are?”

That’s why the tension on the faces of the blasters during every countdown on The Detonators is real, said Lusk. It’s also a factor in the appeal of explosives engineering. “There’s a lot of planning and work up to a specific time, and in a moment you know if what you did is correct or not,” he said. “In a lot of other jobs, you don’t know if you did well until a little later down the road, and then it might be the subject of debate. In blasting, you know right away.”

Lynne Robinson is the news writer for Materials Technology@TMS.