An Australian researcher is experimenting with explosives in New Mexico, hoping the result will be a directional blast that will put out a forest fire, or at least a portion of one.
So far they have wrapped a cardboard tube with detonation cord (det cord) which shoots out a blast, easily blowing the flame off a propane burner. This is similar to blowing out a candle, or placing explosives next to a burning oil well which is being deluged with several master streams of water. As long as there is not enough heat retained, combustion will cease. It remains to be seen if blowing the flames off burning heavy or deep-seated fuels in a forest will end the combustion process. Maybe it will work on grass fires. But how far away from the blast will firefighters have to be? And will the explosion itself start more fires?
Below is the description of the video:
UNSW researchers are a step closer to proving whether explosives — rather than water — can be used to extinguish an out-of-control bushfire.
Dr Graham Doig, of the School of Mechanical and Manufacturing Engineering, is conducting the research, which extends a long-standing technique used to put out oil well fires.
The process is not dissimilar to blowing out a candle: it relies on a blast of air to knock a flame off its fuel source.
Doig travelled to the Energetic Materials Research Testing Center — a high-explosives and bomb test site in a remote part of New Mexico — in January this year to scale up tests he originally conducted at UNSW’s heat transfer and aerodynamics laboratory.
The New Mexico tests used a four-metre steel blast tube — which contained a cardboard cylinder wrapped in detonation cord — to produce a concentrated shockwave and rush of air. This was directed at a metre-high flame fuelled by a propane burner.
The sudden change in pressure across the shockwave, and then the impulse of the airflow behind it pushed the flame straight off the fuel source. As soon as the flame doesn’t have access to fuel anymore, it stops burning.
Doig hopes the concept can now be scaled up to fight out-of-control forest and bushfires burning in remote parts of the world.
For decades specially-trained wildland firefighters have used det cord wrapped in water to create fireline out ahead of a fire. The purpose of the water is to reduce the chance that the explosion will start new fires. If you wrap the det cord around a tree or a log several times it can fell the tree or make a fireline through a log.
This reminds us of a device we labeled a “lame-ass idea” in 2010– a fire extinguisher bomb. This is an actual bomb dropped from an aircraft that when detonated disperses water, theoretically putting out a vegetation fire. Hard hats will probably be required when firefighters are in the area. 😉
In an attempt to remain open minded about the effectiveness of using a directional blast to suppress a forest fire, we will hold off, for now, in describing it as a lame-ass idea.
Thanks and a hat tip go out to Jim.
I see no reason they shouldn’t be able to make this work. I’m horrified at the ecological implications, so would hope that such a tool would be used sparingly, but it could be quite valuable in spots as well. And, probably not much worse than salvage logging ecologically-speaking, at that, maybe even better than salvage logging from a soil perspective.
It would be an interesting experiment to shoot a Russian “Buratino” TOS-1 ( тяжёлая огнемётная система ) thermobaric weapons system in front of a flame front (multi-rocket-deployed fuel-air explosive which creates a large area of fire, then a powerful pressure vacuum; that I think is said to extinguish the fire — rather violently). And the beastie seems to have a range of several kilometers and the ability to climb 60% slopes, 30% side slopes, ford three-foot-deep creeks, etc. Probably also makes a decent fire shelter. Push a button, and in 8 seconds your backfire or forest clearing is on its way. Just how well it would work and how expensive it would be are perhaps unknown.
I would label this the “Big Bang Theory”…
Hmmm, how much explosive do you need to push the flame off of even an acre of burning fuel?
Not that I would mind getting to try it out. “Didn’t work? Maybe we need MORE Explosives!” Didn’t sound like the experiments were fueled by beer, either. Do they have fraternities at UNSW?