Researchers have developed a striking new concept to tackle the biggest problem of small drones: their limited flight time. Instead of a drone having to land to swap batteries, a second drone can dock in the air and temporarily supply energy. The system works as a kind of “flying battery” and can extend the flight time of a multirotor drone considerably.
The idea sounds simple, but the technical execution is quite complex. Even so, initial test results show that the concept can be surprisingly effective.
Two drones that dock in the air
The system consists of two different drones. The main drone carries out the mission and has a docking platform on top. The second drone acts as a flying battery.
This smaller drone flies to the main drone and attaches itself mechanically using special landing legs. Once the connection is made, electrical contacts allow power to be transferred.
A specially designed switching system automatically determines when the energy from the extra battery is used. After the energy has been transferred, the battery drone can detach and fly away again.
Much longer flight time
During experiments, the system was tested several times with repeated docking and undocking in the air. Each time, a fresh battery was attached to the drone.
The results are striking. According to the researchers, the drone’s flight time could be extended by a factor of 4.7 compared with a flight on a single battery.
Even when performance is compared with the platform’s theoretical maximum flight time, the gain remains considerable. In the tests, about 2.2 times the theoretical limit that normally applies to the aircraft was reached.
Notably, this was achieved without the main drone having to become much bigger or heavier.
Important for military and civilian applications
Although the research is mainly technical, the concept could have major consequences for how drones are used.
One of the biggest limitations of small drones is their battery life. Many commercial and military quadcopters can often fly for only 20 to 40 minutes before they have to land.
For reconnaissance missions, surveillance or search and rescue operations, that can be a big problem. With a system in which drones supply each other with energy in the air, a drone could in theory stay airborne for hours.
In military applications, this could be used, for example, for long-term observation over an area.
A kind of aerial version of refuelling
The principle is a bit like air-to-air refuelling for aircraft. Only here it is not fuel, but electrical energy supplied through a docked battery.
The big difference is that both systems must be able to operate fully autonomously. The drones must therefore be able to find each other, stabilise and dock in the air on their own.
That requires very precise positioning and flight control.
Still at an experimental stage
The system is still at an experimental stage and is mainly a research project for now. Even so, it shows how quickly drone technology is developing.
New ideas such as autonomous docking, modular power supply and swarm-like cooperation between drones could greatly change how drones are used in the future.
If such systems are developed further, the “flying battery” concept could play an important role in long-duration drone operations. That could largely solve one of the biggest limitations of small drones: their limited energy supply.
