DJI Phantom 3 Professional consumer drone review
Three modified drones, similar in size to this DJI Phantom, were used to build the rope bridgeIBTimes UK

While we all wait for Amazon – and, perhaps more importantly, takeaway pizza companies – to start delivering by drone, a group of researchers in Switzerland has programmed three drones to construct a rope bridge without any human help. Once complete, the bridge spans a 7.4m gap between two towers of scaffolding, is made from 120m of rope and can support the weight of people climbing across it.

Made at the ETH Zurich Flying Machine Arena in Switzerland, the bridge is made from rope which is just 4mm in diameter and weighs only 7g per metre. The rope can sustain up to 1,300kg.

Although the drones look like they are building the bridge using their own initiative, they are in fact receiving commands from a complex algorithm which uses a motion capture system and a bespoke wireless network. The customised drones are simply following a pre-programmed route, calculated by knowing the distance between the two towers and where the rope anchor points are.

The rope deployment system on each drone uses a spool and plastic tube to feed the rope into place. A system on board each drone estimates the external forces and torque exerted on it; this is taken into account to adjust how the drone flies and behaves in the air.

Once the majority of the bridge is built, the width of its narrow openings are measured by humans. This is fed into the system, which then uses the drones to build stabilisers which make it easier to cross.

The researchers involved say this experiment "acts as a demonstrator", but is a step towards producing rope bridges to be used in real-world scenarios. They say: "Except for the required anchor points at both ends of the structure, the bridge consists exclusively of tensile elements and its connections and links are entirely realised by flying machines."