While drones have a number of constructive applications, such as planting fields, delivering packages and monitoring the safety of factory workers, their potential use in both the military and criminal realms have become a source of concern over the past few years. During the course of this blog, we’ll study a number of methods used to capture, disable and destroy hostile drones.
As drones wielding cameras are becoming progressively less expensive, developers of anti-drone technology have begun an industry of their own. Israeli engineers have recently developed a technique which not only detects a drone, but determines what it is viewing. They first create a recognizable pattern on the object to be viewed. Once the pattern is established, the drone’s radio signals are intercepted from a remote source to search for an identical pattern in the streaming video the drone sends back to its operator. If detected, they can determine they are being monitored by the drone. By use of this technique, the subject is able to see what the drone sees by pulling the pattern from the radio signal-even without cracking the drone’s encrypted video. This technique capitalizes on a video streaming feature known as delta frames. Instead of encoding the video as a series of raw images, it’s compressed into a series of changes from the previous image in the video, which means when a streaming video displays a still object, it transmits fewer bytes of data than when the subject is moving or changing colors. A number of tests at international sites have proven this compression feature can reveal key content of a video to the subject intercepting it. Though an effective technique, compression stream monitoring is too sophisticated for the average drone user.
Another method of drone detection is through the radio signal between the operator and the drone. The Aeroscope system, developed by the Chinese firm DJI, works by detecting the communication signal between the drone and its controller. It then decodes the signal and sends the drone’s telemetry data and registration to the Aeroscope box, much like that of a GPS display. If the owner of the offending drone is registered, an e-mail may be sent to the owner, advising them of local policies. While the Aeroscope system is currently only able to detect DJI drones, which represent about two-thirds of the drone market, enhancements are expected in the near future. Firmware updates will allow the Aeroscope to communicate with other drones based upon electronic signature. These communications will be in real time, as opposed to the current e-mails, which may not be read until days after the event. While the Aeroscope system has proven effective, it is too costly for the average drone enthusiast and primarily utilized by governmental agencies.
Another defense against drones is to capture them. This may be accomplished by using an interceptor drone or a land launched net. These drones use video cameras which are directed toward suspicious drones flying in unauthorized areas. Once the interceptor drone is within range of the suspect drone, it shoots a synthetic netting which wraps around the suspect’s propellers, forcing it down. The Tokyo Police have a fleet of interceptor drones, whose mission is to protect both public buildings and officials. The drones, which measure 3′ by 3′, deploy netting measuring 3′ by 6′ and have been largely successful, leading to the arrest of the drone operator in one case. Police in Britain use shoulder-mounted guns to intercept drones. The most sophisticated of these devices, developed by the British engineering firm Open Works, is a large bazooka, the SkyWall100, which fires a net and parachute at a target while using a high- power scope for aiming. The SkyWall system is a highly successful one, in global use by a number of security services and government agencies.
Several other methods of drone interception bear mention. During the last few years, both the United States and China have tested laser technology which can successfully shoot down a drone within seconds of interception. Boeing has recently developed a high energy beam that both locates and disables drones at a distance of several miles. This device utilizes infrared cameras, which are effective in conditions of low visibility. A novel approach was taken in the Netherlands, in which eagles were trained by Dutch police to bring down suspect drones by latching on to their propellers, rendering them ineffective. The eagles see the drones as prey and quickly lose interest in other pursuits. Drones may also be disabled by jamming their operating frequencies. Two such devices have come into use, the Anti-UAV Defense System (AUDS), scans the skies for hostile drones by use of a high-powered radio signal. A portable system, which utilizes targeted radio signals to disrupt drone controls is the DroneDefender. The Defender system is an electronic rifle which operates in the same manner as the AUDS device. These currently have a range of about 1,500 ft, with more capable units under development. The potential problem with using both the AUDS and Defender systems are their capability to jam local radar transmitters, a source of legal problems. Finally, several drone manufacturers have collaborated to establish no fly zones for their drones. If you add your address to their database, any drones made by these manufacturers will be unable to fly over your property due to built-in GPS restrictions. Though a viable concept, not all manufacturers are willing to allow access to their database, as well as no law to enforce its use.