Sky nets: the new anti-drone defence system

C69 technophile 1
anthony Calvert

In the wee hours of January 2015, a drone crashed on the lawn of the White House causing a major panic. In July, a drone dropped a package of marijuana and heroin into the yard of a prison in Ohio. In January 2016, UK airline pilots called for action after four near misses between drones and airplanes at Heathrow and other airports.

Drones are no longer just pesky toys. They’re a serious hazard and a tool for criminals and terrorists.

So expect to see anti-drone defences coming your way soon. Paul Pounds, an engineer at the University of Queensland, says they will likely become standard for use by police and other authorities in the next few years.

As always, surveillance is the first layer of defence. The DroneShield sensor system, used to patrol the 2015 Boston marathon, listens for a drone’s tell-tale buzz, alerting authorities to its location and even its make.

But once you detect a drone, how do you take it down?

Blasting it out of the sky is not a good idea if it’s above a crowded city street or sports stadium. UK company Enterprise Control Systems is working on technology to jam the radio-frequencies used to control the drones. The idea is to set up a drone-free perimeter around public events or sensitive zones.

Another option is to use an anti-drone drone. Enter the “robotic falcon” developed at Michigan Technological University. This predatory unmanned aerial vehicle (UAV) captures its prey in air-to-air combat by firing a net. With a casting range of 12 metres, the challenge is to swoop in close enough to the target.

Of the anti-drone systems that are close to being ready for market, the most polished is SkyWall, says Pounds. Developed by UK-based OpenWorks Engineering, this net-gun bazooka uses a gas-powered launcher fired from the shoulder to blast a net at a drone up to 100 metres away. It delivers it safely to earth via parachute.

Net-guns have been used to take down drones before but what distinguishes SkyWall is the smart technology embedded within the launcher and the projectile.

First off, the operator sights the target down a digitally augmented scope. A laser system keeps tabs on the target’s range, while an onboard movement detector, like the one that tells your smartphone to reorient its display when you flip it, monitors the orientation of the launcher, feeding these data into the SkyWall’s on-board computer. The computer calculates the ideal trajectory of the net-loaded projectile, including corrections such as firing a little ahead of a moving target.

Once a drone is spotted, auto-aim kicks in. Levers within the launcher activate to adjust its bearing, helping the operator achieve a perfect shot.

Range information is also fed into the projectile’s control circuits so it knows how far to fly before deploying its net.

Compared with net-guns that open immediately on firing, this smart opening system extends the range by about tenfold. When the target is locked on, the SkyWall emits a beep – the signal to pull the trigger. The projectile is gas-powered so it fires without a frightening bang that might scare a crowd.

Besides the mobile, shoulder-mounted version, SkyWall offers a semi-permanent installation that has an increased range. It can be set up at key locations to protect the entire area of a major event.

SkyWall’s most powerful offering is a permanent anti-drone defence unit for the most sensitive locations – airports, prison walls or the White House. It can be remotely operated from a control room and its semi-automatic design means it can reload itself with projectiles.

The quicker it reloads, the better. Pounds predicts that with drones getting cheaper, criminals will likely try to overwhelm defence systems by flying groups of drones. “They can’t catch them all.”

The anti-drone arms race is on.


The SmartScope scans the field of view for drones, then displays the distance to the target as measured by lasers.


On-board levers adjust the way the launcher is pointing, to make sure of a direct hit. This auto-aim also takes account of gravity drop and how far to aim in front of a moving target.

Intelligent projectile

As the trigger is pulled, distance data is loaded into the projectile, telling it how far to fly before opening its net.

Net and parachute

After the net envelops the target, the projectile fires its parachute to bring it safely to earth. The target drone can now be recovered and examined for forensic evidence.

The video of SkyWall in action can be viewed here.

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