Explosive mines are not only a fact of war-torn countrysides, but also of countries that harbor terrorists or guerilla groups. Some of the most notorious bombs are IED's, or improvised explosive devices, which are homemade explosives often buried near roadsides. These can be hard to detect since they're usually built with rag-tag materials like plastic, glass or plaster of paris, and contain little metal that can be picked up by metal detectors. While they're sometimes thrown off bridges or tossed into buildings, IED's are often left as mines that are detonated by remote control or with built-in sensors.
The threat of IEDs presses close to home for Félix Vega and Nicolas Mora, two doctoral students at the Ecole Polytechnique Federale de Lausanne in Switzerland who are from Colombia, a site of ongoing guerilla conflict. In response, the two have figured out how to detonate IED's remotely using pulsed electromagnetic energy. In laboratory tests, their device set off bombs 65 feet away on average.
Remotely detonating an IED has several challenges that Vega and Mora addressed. First, the pulse of current needs to be strong enough to have an effect not only from a great distance, but on bombs that might buried deeply underground. The device also needed to affect as many different bombs as possible, because improvised explosive devices are just that: improvised. So the electromagnetic currents need to cover a range of frequencies. But sending energy pulses successively in many different frequencies weakens each current that reaches the IED. Too weak, and it won't detonate. Fortunately, the researchers found that most IED's were triggered by similar frequencies and so they were able to make a short list of which ones to use. This saved energy over many feet and made the device effective.
Vega and Mora developed the bomb detonator in collaboration with two Colombian Universities and tested the device at Colombia's Electromagnetic Compatibility Laboratory, where professional bomb disposal experts constructed real IED's for detonation. The pulses shot by the researchers easily penetrated the bombs, which are usually designed with inexpert circuitry barely shielded from electromagnetic radiation — a plight of being plastic rather than metal-based. And since the detonator can set off unprotected devices in the correct frequency range, it neatly gets around the problem of having to physically pinpoint a bomb before taking care of it. Instead the device can just send impulses out into an area with suspected IED's and clear up any lurking threats.
Now the team is working on a longer study to make the detonators smaller and more durable so that they are suited to bring on back country roads. The National University of Colombia and the University of Los Andes have committed to four years of tackling this project together.
Caption: This Humvee was destroyed near Nangalam Village on the Pech River Road in eastern Kunar Province, Afghanistan, along what U.S. Marines knew as IED Alley. Credit: Ed Darack/Corbis