Given that the battery life of most multicopter drones typically doesn't exceed 30 minutes of flight time per charge, there are many tasks that they simply can't perform. Feeding them power through a hard-wired tether is one option, although that only works for applications where they're hovering in place. Scientists at Imperial College London, however, are developing an alternative – they're wirelessly transferring power to a drone as it's flying.

For their study, the scientists started with an off-the-shelf mini quadcopter. They proceeded to remove its battery, add a copper coil to its body, and alter its electronics.

The researchers also built a separate transmitting platform that uses a circuit board, power source and copper coil of its own to produce a magnetic field. When placed near that platform, the drone's coil acts as a receiving antenna for that magnetic field, inducing an alternating electrical current. The quadcopter's rejigged electronics then convert that alternating current to direct current, which is used to power its flight.

Known as inductive coupling, the technique has been around since the time of Nicola Tesla. According to Imperial College, however, this is the first time that it has been used to power a flying vehicle. While it currently only works if the drone is within 10 cm (3.9 in) of the transmitter, it is hoped that the range can be greatly increased.

Additionally, instead of continuously powering battery-less copters, it is envisioned that the technology could be used to recharge drones' onboard batteries as they hover over ground support vehicles equipped with the transmitters – this would allow them to remain airborne while recharging, instead of having to land.

It's also possible that the drones could be wired to serve as flying transmitters themselves, "beaming" power from their battery to recipient devices such as hard-to-reach environmental or structural stress sensors, or even to other drones that need a mid-air recharge. A team at the University of Nebraska-Lincoln, in fact, has already used a quadcopter as a flying wireless charger.