Flight paths for a regenerative fuel cell based high altitude long endurance unmanned aerial vehicle

Unmanned aerial vehicles (UAVs) are being developed worldwide for the purpose of communications or military activities. We considered a Regenerative fuel cell (RFC)-based High altitude long endurance (HALE) UAVs because it can regenerate hydrogen and oxygen by using power of photovoltaic arrays during the day. To make an RFC-based HALE UAVs fly continuously, the study of flight paths is essential and an easy approach using the current technologies. We introduced the four cases of flight paths and determined their required energies. It is concluded that climb-after-glide flight is best feasible flight path among four flight paths for RFC system-based HALE UAVs due to air density and time of operating motor. In addition to climb-after-glide flight other flight strategies enable the aircraft to continuously conduct missions in limited range of an altitude, which validated that the RFC system is suitable for use in a HALE UAVs.