A research project by Georgian and American scientists and sponsored by NATO has led to a device that can reduce the awesome, destructive power of tunnel explosions.
Explosions inside confined spaces are central to modern warfare—that is basically the entire theory behind bombs and missiles, after all. But underground explosions can make for some of the deadliest industrial accidents out there. Militaries around the world must also watch munitions stockpiles closely, some of which are buried inside tunnels.
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Storing bombs inside a tunnel is typically far safer than doing so above ground. But an explosion in a confined space is far more destructive than in the open air, as shock waves violently reverberate off the hard walls, floors, and ceiling instead of dissipating quickly into the atmosphere. There is simply less space for the pressure to go.
Georgia has direct experience. During the Russian invasion in 2008, a massive explosion near the village of Skra—inside a tunnel complex used to store munitions—violently ejected thousands of shells, ammunition, and bombs into the countryside. The blast created an enormous hazard to civilians and wildlife.
The NATO-financed device works by combining sensors with a pressurized tank filled with dozens of liters of water. Mounted to the roof of a tunnel, the sensors can detect shock waves from an explosion, and automatically triggers a pyrotechnic device and the release of the water within milliseconds.
The above NATO video shows the device in action at an underground testing base in Georgia. The researchers even included a dummy rigged with sensors to study the effects of a blast on the human body.
In other words, think of it like a really intense yet calming shower for an explosion.
The effect is not to stop, but reduce the overpressure of the incoming shock wave—roughly by half—once it makes contact with the water, according to a 2015 research paper by the scientists. (Caveat: The exact numbers depend on the amount of water released and the size of the blast.)
In other words, think of it like a really intense yet calming shower for an explosion.
“We develop all sorts of different technologies in the hope that they will be used both for military and for civilian purposes,” NATO science adviser Michael Switkes said. “Fuel trucks, for example, have exploded inside tunnels causing catastrophic accidents and if those civilian road tunnels were protected by systems like this one, those catastrophic failures could be contained and lives could be saved.”
To be sure, blast suppression systems exist in tunnel networks today. These machines are more common in Europe, Russia and the United States.
But according to the scientists, these existing devices are slower to react—again, it comes down to a matter of milliseconds—requiring them to be placed farther away from a potential source of an explosion. Not every tunnel will have enough room, either, and existing systems often produce less water, which means less dampening of overpressure.
You could also use more than one dampening system in a tunnel. With a long enough tunnel, multiple devices could further degrade the shock wave as it travels down the length of the corridor.
“The presented mist generator can be applied in motorway and railway tunnels, coal mines exposed to the threat of methane explosion, land- or sea-based oil platforms, other petrochemical plants and long superstructures with limited cross-sections that could be [vulnerable to] gas or dust explosions,” the scientists wrote.
Let’s not forget ammunition dumps.
