Blasting bushfires with explosives

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.