Mixing drones with fire sure sounds like a dangerous idea, but under close control this unlikely pairing could have a beneficial environmental impact. Researchers at the University of Nebraska-Lincoln (UNL) have been developing a drone that ignites controlled burns from the air, and the team has now carried out real-world testing of the technology with a view to minimizing risks to conservation crews and avoiding out of control wildfires.

The university's fire-starting drone has been under development for almost two years. The aircraft is fitted with a chute and loaded up with balls containing potassium permanganate powder. As each ball is prepared to be launched toward a target area on the ground, it is injected with liquid glycerol which kicks off a fire-starting chemical reaction within 60 seconds of it hitting the deck.

Controlled burning is an essential part of land management in fire-prone areas, where flammable trees and grasslands can grow out of control. They can also help to apply the brakes to invasive species. Helicopters and handheld launchers are a couple of methods currently used to reduce the risk for firefighters, but the researchers believe drones can offer a cheaper and more efficient alternative.

The researchers deployed their drones over Homestead National Monument of America to burn 26 acres (10.52 ha) of restored tallgrass prairie. Prescribed burns are frequently used in these grasslands to fend off cedars and shrubs, but this time around the crew had a little help from above.

Trained firefighters started by burning the perimeter of the designated area. The drone then flew about 200 yards (180 m) into the area, before turning around and deploying the ignition balls at eight second intervals on the return leg. The drone then floated over the area gathering data on fire conditions that the researchers will study to continue improving the technology.

The drone used was the fourth prototype the team has developed and a couple more iterations are likely in the next two years. The team is currently in discussions with the Midwest Regional Fire Management Office about carrying out tests later in the year at Badlands National Park in South Dakota. With woody growth and rugged terrain, this landscape is even trickier for firefighters to navigate and therefore may see the drones prove even more valuable.

"A tool like this might be one of the answers to making these fires safer," says Mark Engler, superintendent at Homestead National Monument. "This is an important test. It is important to us to help UNL develop this technology."

You can hear from the researchers and see the drones in action in the video below.

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