The drone challenge: attacking is easier than defending

The discovery of an explosive-laden drone at Leipzig airport has put counter-drone defence back at the centre of European attention. Roland Siegwart, professor of autonomous systems at ETH Zurich and a partner of armasuisse, sums up the problem in a single observation: «Effettuare attacchi con droni è molto più facile che difendersi dai droni, specialmente in ambiente civile» (carrying out drone attacks is much easier than defending against drones, especially in a civilian environment).

The reasons are technical before they are military. A small drone reflects very little radar signal and is easily confused with other objects in camera footage. Recognising it in time, and telling it apart from a bird or a light aircraft, is the hardest part of the whole chain.

Then comes the cost problem. Air defence systems were designed to shoot down aircraft and helicopters, and use munitions that can cost 500,000 francs each. Firing them at a device worth a few thousand makes no economic sense: the attacker can multiply attempts, the defender cannot. That imbalance is what keeps counter-drone defence an open problem even for well-equipped armed forces.

Over cities a third constraint applies. Firing upwards in an inhabited area carries risks for people on the ground, both from the projectiles and from fragments of the downed drone. The classic military solution, destroying the target, is often unusable in a civilian setting.

The countermeasures under study

Research is working on two fronts. On detection, several sensors are combined: radar, infrared cameras and optical cameras, because none of them works well alone in all conditions. On interception, work is under way on systems that capture the device with a net and on interceptor drones, that is, devices that stop others in flight. In both cases the aim is to neutralise the target without making it explode over someone's head.

On Switzerland's position, Siegwart is fairly optimistic. Relative to its size the country is well placed, thanks to cooperation between armasuisse and the universities and to a civilian drone research ecosystem that includes several specialised start-ups. It is the same technological fabric that feeds civilian applications, from infrastructure inspection to the transport of medical samples.

The open question is scale. The technologies described work over a defined perimeter, such as an airport or a sensitive site, whereas protecting a wide territory would require a number of sensors and operators that no European country currently has. The Leipzig episode involves a single device found on the ground: the question it raises is what would happen with ten of them in the air at once.