Imagine a disaster-relief scenario where people need to be transported from one side of a ravine to the other, in an area not easily accessed by ground vehicles. What could a series of lightweight quadrotor drones do to help, besides record overhead video or drop off a few candy bars at a time? Amazingly, they could build a rope bridge to span the chasm.

Researchers at ETH Zürich (the Swiss Federal Institute of Technology) have rigged up a series of drones with spools loaded up with rope. Because the spools are motorized, the drones can control the tension on the rope they deploy as they fly. The researchers then programmed the things to build a rope bridge between two scaffolds—freaking autonomously:

The project came about after the researchers factored in the key positive and negative aspects of a quadrotor. The positive: Can travel anywhere. The negative: Small payload capacity. Thus they struck upon the construction of lightweight tensile structures as being an ideal fit for drone duty.

The rope bridge acts as a demonstrator, showing for the first time that small flying machines are capable of autonomously realizing load-bearing structures at full-scale and proceeding a step further towards real-world scenarios.

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 realized by flying machines. Spanning 7.4 m between two scaffolding structures, the bridge consists of nine rope segments for a total rope length of about 120 m and is composed of different elements, such as knots, links, and braid.

You can read more about the project here.