The person who was awarded a patent in 2017 for describing a system of drones that could be used to drop liquids on wildfires wrote a paper earlier this year with two other authors that claims to have determined how many drones would be needed for suppressing a small section of a fire.
The patent, awarded to Marco Ghio, is quite vague and does not supply any technical details. It says that instead of applying fire retardant or water in a conventional manner, a “rain” concept would be used.
In the United States fire retardant dropped from an approved air tanker is applied at coverage levels ranging from 1 to 9 gallons per 100 square feet, depending on the situation. It is not clear what coverage level “rain” would produce.
The patent specifies that drones would transport the liquid in removable containers. Upon returning empty to the mobile base the containers would be autonomously replaced with full containers, along with a charged battery if needed.