Multi-rotor drones are now employed to do many jobs, such as pesticide spraying and field inspection, but it remains challenging to increase their duration on the air and loading capacities that could extend their uses.
Most drones are unable to fly over 30 minutes in a single flight because of battery limitations. Carrying more batteries would not necessarily increase the flight time, as the weight of the extra batteries would cancel out the additional power.
Some multi-rotor drone makers have tried to hike loading capacities by enlarging the devices' dimensions, but they face difficulties: longer vanes of rotors, for example, may be break easily. The problem could be solved by adopting the mechanical structure of helicopters, but that would lose the original advantage of the drones' simple mechanical structure.
Some solutions are being tested, such as adding fixed wings to multi-rotor drones, using aerial power charging devices or fuel cell batteries. However, these options have yet to mature for commercialization.
