Design and analysis of air launched fire-extinguishing devices

Wildfires are an enormous source of human and environmental loss. Unmanned aircraft systems and fire-extinguishing balls (FEB) might help combat wildfires in their early stages of development. This paper addresses the design of FEB-based fire-extinguishing devices. The viability of four configurations for the device is evaluated. Trajectory simulations were performed using a six-degrees-of-freedom model. The device configurations’ static aerodynamic coefficients were obtained through computational fluid dynamics (CFD) and dynamic coefficients obtained through analytical methods. CFD results indicate that a tube-like tail has a transient behaviour in the tested speeds, and a conical tail is a suitable way to streamline the FEB. The trajectory simulations were compared to flight tests using a replica of the device. Trajectory results highlight the importance of mean wind velocity and direction and correct estimation of launching height and speed to accurately predict the point of impact. The flight tests validated the used trajectory prediction model.