Drones can be purchased for as little as a few hundred dollars providing huge bang for the buck in terrorist terms. Photo: Arnold Reinhold / Wikipedia CC

The Saudi oil attacks employed not only missiles but also drones and the latter may have aroused the most concern. How can drones be defended against?

In fact the Pentagon is now investing in a prototype anti-drone “killer” system, and meanwhile other governments – notably Israel – are supporting companies that offer anti-drone systems.

The big bundle of questions is: Which of these, if any, work and, equally importantly, provide broad enough coverage – and are considered cost-effective and thus affordable and deployable?

Cost is a key issue because drones are proliferating far faster than are any countermeasures while available countermeasures are vastly more expensive than drones – which can be bought for $100 or even less.

Drone threats

There are essentially three general types of drone threats.  The first threat type comes from commercial drones, mainly Chinese units that can be easily modified by adding explosives as the payload.  China has more than 80% of the commercial drone market (one Chinese company, DJI, has 70% of the global market in drones) and these drones are being snapped up by military agencies around the world, including the US Defense Department (which supposedly is prohibited from buying drones from China, but gets ‘waivers’ and buys them anyway).  Every Middle Eastern bazaar (even toy store) is selling Chinese-made drones; it is likely the same is true in other parts of the world.

The second type of drone is a home built, with supplies coming from China and elsewhere.  Home built drones with internal combustion engines can be larger than the Chinese electric commercial drones and can fly farther.  Motors for these drones are bought in Europe and China, and most of the electronics come from China.

The Russians encountered very serious problems with swarms of home-built drones, likely made by ISIS, that were used to attack Russia’s Syrian airbase (Khmeimim ) and naval base (Tartus).  Despite having modern air defenses, the drones flew into the Russian bases without being detected, mostly because those drones were made of balsa wood, fabric and duct tape.

There were two subsequent attacks on Khmeimin, but the Russians say they were able to shoot down the drones.

The engine, fuel tank and fuel lines of a captured ISIS-made drone. Photo: TASS

The third type of drones are strictly military items.  Some of them have far longer range and far better sensors than their commercial counterparts – and can carry bombs and missiles such as  Lockheed-Martin’s Hellfire air-to-surface missile.  The US has used its killer drones, including the MQ-9 Reaper, to wipe out terrorists even in moving vehicles.  Such drones can travel thousands of miles.

The latest Pentagon concoction is the Raytheon “Phaser” system, a microwave electronic circuit “french-fryer.” The idea is to direct an extreme amount of microwave energy at a drone, killing its electronics. Ostensibly the result is a drone that will go out of control and crash.

Very little information is available about the parameters of the system although the claim is made that it works with drones that weigh less than 55 pounds, flying at 1,200 to 3,500 feet and traveling at speeds between 100 and 200 knots.

What is not explained is whether simple cheap shielding of a drone’s electronics wouldn’t render the microwave “french fryer” ineffective. Commercial drones generally do not have shielded electronics.

Some years ago similar technology was offered by police to jam cars and trucks and render them inoperative. Of course on a crowded highway, the results could be catastrophic for other vehicles. But for preventing attacks by vehicles trying to blow up a military base the US Defense Department is working along such lines on what it calls a Radio Frequency Vessel Stopper with a range of 50 meters (small model) to “a few hundred meters” (larger model).

A key problem for defenders is how to detect a drone or drones.  Essentially there are three ways: radar, electronic signature and enhanced optical sensors.


Technically radar would seem to offer the best prospects for success, but radar has trouble picking up small, slow-moving drones, which are “naturally” stealthy. The villain of this piece is ground clutter and separating out the clutter from the radar return of the drone itself. With all radar solutions, there are high false detection rates of radar-based systems, meaning that operators will think they “see” drones when they “see” ground clutter or birds.

Special radars can be mounted on vehicles or on towers. More exotic solutions such as using tethered aerostat systems (moored balloons) do work, but are very costly. Lockheed Martin produces what it calls a Persistent Infrastructure Protection Tailored Aerostat system and other aerostat models that are deployed along the US borders, such as the LM 420K Aerostat system.

Electronic signature

Detecting the electronic signature of a drone is a solution if the drone is commercial or uses commercial electronics. Commands sent to the drone or drones can be intercepted, jammed or spoofed.

A variant on this is GPS jamming, which can force the drone to entirely miss its target. The jamming-spoofing approach gets around the problem of using radar, but it is a solution that is limited in range and essentially is a point defense solution. It is, however relatively cheap to deploy compared with radar, and the better systems can locate the drone or drones by triangulation.

Even so, if the drone is mostly passive in its terminal flight phase, or where “local” controllers take command of the drone in the last minutes, as appears to have happened in Saudi Arabia, it might be challenging to actually defeat a drone that is very close to its end-target.

Electro-optical sensors

A third way is electro-optical sensors that can scan an area looking for threats.  FLIR Systems has introduced two systems, the R8SS and R8SS-3D.

According to FLIR “The R8SS-3D detects land and air objects, such as micro-drones, and differentiates birds from drones.

The Ranger R8SS-3D reports the altitude and location of small drones at ranges of two miles and can also detect vehicles and people walking or crawling. The R8SS-3D can detect more than 500 threats and their exact locations simultaneously, and work within an existing data network.

A FLIR is a forward looking infrared system that uses thermal detection (essentially the heat signature of a threat).  Because some drones use battery-powered motors it isn’t clear that thermal imaging systems can reliably pick them up.

Bottom line

All these systems, radar, electronic signature and electro-optical can be linked to active anti-drone destruction systems including lasers, specialized rapid-fire weapons or other active destruction systems including small missiles.

But the bottom line is that while any or all of these systems can play a role in detecting drones and linking detection to destruction, they suffer from relatively limited range and uncertainty about their effectiveness.

Drone defenses are best for fixed targets such as infrastructure targets including oil facilities, power plants (including nuclear), airfields and military bases.

Where a drone is used against a moving target, good drone defense is more difficult.  And, where the targets are relatively dense urbanized settlements, towns and cities, point defense may not be good enough to prevent the destruction of homes and buildings.

In addition, because small drones are easy to smuggle and deploy very close to their target, there may be insufficient time to detect and destroy them.

Clearly the search for technical solutions will continue but it is hard to predict if these efforts will narrow the gap sufficiently to provide reliable security.

Any deterrence approach to the drone threat has to include either trying to destroy the drones before they are launched, a distinct challenge requiring excellent intelligence, or taking action to punish the perpetrators severely so they don’t try it again.

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