A mobile, high-power microwave weapon can knock down a swarm of drones at once or pick a single drone out of a group with sniper-like precision.

Anti-drone weapons, such as radio-frequency jammers, already exist, but are only effective against consumer drones – they were used at London’s Gatwick airport in 2018 to defend against a suspected drone intrusion that left flights grounded.

More advanced military models are protected against these kinds of jammers – either being equipped with jam-resistant radios or having the ability to operate autonomously without a radio link to an operator – so the Leonidas system developed by Epirus, a Los Angeles start-up, takes a different approach. The device fires a high-power microwave beam that overloads a drone’s electronics, causing it to drop out of the sky.

While existing microwave weapons are about the size of a shipping container, Leonidas fits in the back of a pickup truck. It can be controlled with great precision. “Our systems allow us the capability to widen or narrow the beam and put a null in any direction to disable enemy targets and nothing else,” says Epirus CEO Leigh Madden. The company is also working on a smaller version of the weapon that could be carried by operators on foot.

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In a demonstration for a US government customer in February – the company wouldn’t disclose exactly which – Leonidas brought down all 66 of the drone targets. In some tests, it took out several drones at once. In others, it targeted one while leaving an adjacent drone untouched.

Leonidas is based on an array of solid-state gallium nitride emitters – like LED lights but for radio waves. Used initially for military radar and now in 5G communications, these emitters are more compact than traditional radar devices and can be individually controlled to steer the microwave beam with high precision.

Justin Bronk at defence think tank RUSI in London notes that while microwaves may be more acceptable than guns or missiles for defending populated areas, high accuracy is needed. “In urban areas, there’s a danger of damaging the electrical power infrastructure or frying people’s electronic devices,” he says.

The technology promises to provide protection for both military and civilian infrastructure, for example defending airports and sports stadiums. It could counter mass drone attacks like the one that disabled Saudi Arabia’s Abqaiq oil-processing facility in 2019.

Many countries, including China, Russia, the US and the UK, are working on swarming attack drones that could overwhelm existing defences through sheer numbers. High-power microwaves might offer the best protection against such swarms.