Heat-Resistant Drones for Firefighting

Drones can assist in such scenarios: researchers at Empa and The Imperial College London are developing a heat-resistant drone that can deliver initial information about the danger situation. This enables the men and women of the brigade to adjust their strategy before they attack the inferno.

“The firefighters don’t know what they will encounter and what difficulties they will face before they enter the danger zone,” says Mirko Kovač, head of the ‘Sustainability Robotics Labʼ at Empa as well as the ʻAerial Robotics Labʼ at Imperial College London. Drones equipped with cameras and CO₂ detectors (carbon dioxide) can provide valuable information about the extent of the fire, unexpected dangers or trapped people.

Too Hot for Normal Drones

Drones are already being used for firefighting to take aerial pictures, to lift hoses onto high buildings or to drop extinguishant in remote areas, to stop the spread of forest fires for example – but always at a safe distance from the actual fire.

“The extreme heat of a fire is too much for normal drones to be able to fly closer,” says David Häusermann of the Sustainability Robotics Lab at Empa. The frame would melt and the electronics would fail close to the fire. Conventional drones can only provide aerial images of the fire from a safe distance.”

It was therefore the aim of the robotics researcher to develop a drone that could withstand the heat and quickly provide precise info about the center of the fire.

Ultralight and Tough

Together with firefighters, David Häusermann established the requirements for a drone that would be used close to fires and set about finding a material that could surround and protect the core of the drone – the motors, batteries, sensors and the electronics.

He found the answer with his colleagues from the Empa Building Energy Materials and Components Lab: the team of researchers working with Shanyu Zhao and Wim Malfait were able to create an isolating material that could withstand high temperatures and thereby make the drone more resistant to fire.

They were inspired in the design of the ‘fire drone’ from nature, or more exactly, from animals like penguins, the polar fox, and certain beetles that all live at extreme temperatures. All these animals have corresponding layers of fat, fur, or produce their own protective layers from a temperature-regulating material that allows them to survive under extreme conditions.

Suitable for Space Suits

This is an aerogel, an ultra-light material that consists almost completely of air-filled pores that are covered by a skin of a polymer substance. In this case, the material researchers used an aerogel on the basis of a polyamide plastic. Polyamide aerogels are also being researched by NASA, among other reasons for insulation in space suits.

Shanyu Zhao not only used polyamide for the creation of this aerogel: the composite material consists of polyamide and silica and is also strengthened with glass fibers.

“Laboratory analysis has shown that this comparatively fire resistant material is particularly well-suited for use in drones,” says aerogel researcher Shanyu Zhao.

Flight into the Inferno

The prototype of the ‘FireDrone’ already did well during the first tests in the flight arena at Empa in Dübendorf. The flying characteristics and control of the approximately 50 centimeter drone were excellent, even when fitted with the aerogel insulation jacket and an additional cooling system as well as aluminum wrapping to reflect heat.

The design that the researchers published in the “Advanced Intelligent Systems”“ newssheet was impressive during the ‘dry run’. Whether the drone would survive a real fire had to be tested under realistic conditions.

The Empa team were able to experience such a ‘real life’ scenario on the grounds of the training center in Andelfingen. Stefan Keller, training coordinator of the fire brigade for building safety in the canton of Zurich, together with the training center logistics crew, built a gas fire in an enormous metal dish, and the drone pilots flew their device into the middle of the inferno.

The result: the FireDrone prototype survived numerous test flights. A happy David Häusermann summarized: “Even after numerous flights, the electronics, the thermal camera and the CO₂ sensors of the FireDrone were undamaged and ready for further tests. The next step will be to test the FireDrone in a fire that in contrast to the relatively ‘clean’ gas flame contains a lot of smoke particles.”

The fire brigade expert Stefan Keller was impressed with the results: “If a drone can make a first assessment of the situation, we don’t have to send firefighters into the danger zone immediately. This is an enormously interesting step forward for us.”

The FireDrone could also be used in extremely cold environments, such as in polar regions and on glaciers. The team also tested the drone in a glacier tunnel in Switzerland to see how the system behaved in very cold temperatures. Discussions are already underway with potential commercial partners on developing the prototype further.

“The use of drones has so far been limited by environmental factors such as extreme temperatures,” says Mirko Kovač. “The FireDrone has demonstrated a way to considerably extend their application in the future under extreme conditions.”