Endurance Estimate for Solar-Powered Unmanned Aerial Vehicles

Calculating endurance is very important for solarpowered airplane, both with respect to aircraft designs and mission planning. This paper presents a graphical method to evaluate the approximate endurance of solar-powered unmanned aerial vehicles (SUAV). The method, which is based on the principle of energy balance, is established in this study. According to the principle, cruise endurance is considered as a steady-state flight where the effects of date and location are taken into account, but other effects (acceleration or flight path inclination) are neglected. Firstly, to predict the total energy of SUAV, an energy harvesting model, based on clear sky solar irradiance, is introduced. Subsequently, the expression used to calculate the energy consumption for SUAV in level flight is shown. After that, the process of endurance estimation is described. And then, to describe the endurance of SUAV, the perpetual endurance window is introduced. Finally, some numerical simulations are presented, and simulation results demonstrate the graphical method is a feasible and flexible tool to estimate endurance of SUAV.