From Michigan Tech Today March 24, 2006

Warren Perger is trying to find out why bombs blow up. It's more than an interesting theoretical question. If we understood the fundamental nature of explosive materials, life might be a lot safer for those who handle or are exposed to explosives, such as America's soldiers.

For instance, it's conceivable that one could work out a way to find an improvised explosive device and detonate it from a safe distance. "Sometime, we'd really like to be able to say, 'Ahah! There's an IED behind that door,'" said Perger, a professor of physics and electrical and computer engineering.

With researchers at MIT and at Washington State University, where he is on sabbatical, Perger hopes to figure out what happens in the trillionth of a second after an energetic material is subjected to impact and subsequently detonated. The team is also trying to uncover ways to detect explosives remotely.

Their work is being funded by a $3 million grant from the Department of Defense Multidisciplinary University Research Initiative, part of a massive effort by the military to better understand energetic materials and use that knowledge to better defend against the type of warfare now being waged in Iraq.

Over the last five years, the scientists have been investigating how some very energetic materials respond to pressure. "That's what happens when you hit it with a hammer or detonate it with a blasting cap," Perger explains. "We are interested in what happens during the initiation phase," the material's first response before detonation.

Explosives are metastable materials, meaning they aren't perfectly stable. They are made up of stack upon stack of molecular crystals, like those in a chunk of rock salt but more complex. When you send a shock through a material in a metastable state, the crystals are squeezed together and the bonds between them break down and release energy--sometimes lots of energy.

What sets off any given explosive can be quirky. Some need to be compressed from all directions. Some can be detonated with lasers. One particularly dangerous material, PETN, is made up of a very complicated crystalline lattice. "It has a weird property--you can hit it in one direction and it's stable, but will easily detonate if you hit it from another," Perger said.

He has been studying the infrared absorption profiles of certain explosives, which change as they are compressed. Theoretically, this could yield technology that would allow ground troops to tell the difference between a rock on the side of the road and an IED before it's too late.

His mathematical models have made some remarkably accurate predictions, but at the moment, Perger isn't making any promises.

"We've had some good successes in the last few years, but this is pretty high-risk research," he says. "Will we ever have a complete picture? That's like asking someone in 1958 if you can go to the moon. At this point, we just can't say. But you never know if you don't try."