AN ATTACK on Russian forces in Syria on January 5th by 13 home-made drones is a good example of “asymmetric” warfare. On one side, exquisite high-tech weapons. On the other, cheap-as-chips disposable robot aircraft. Ten of the drones involved attacked a Russian airbase at Khmeimim. The other three went for a nearby naval base at Tartus. Rather than being quadcopters, the most popular design for commercial drones, the craft involved in these attacks (some of which are pictured above) resembled hobbyists’ model aircraft. They had three-metre wingspans, were built crudely of wood and plastic, and were powered by lawnmower engines. Each carried ten home-made shrapnel grenades under its wings.

According to the Russian Ministry of Defence, which has so far refused to say who it thinks was responsible for the attack, the drones were guided by GPS and had a range of 100km. The electronics involved were off-the-shelf components, and the total cost of each drone was perhaps a couple of thousand dollars. The airframes bore a resemblance to those of Russian Orlan-10 drones, several of which have been shot down by rebel forces in Syria. The craft may thus have been a cheap, garage-built copy of captured kit.

These particular drones, the Russians claim, were intercepted before they could cause any damage. However, several Russian aircraft were apparently damaged in an attack in Syria four days earlier, which was also, according to some accounts, carried out by drones. And there will certainly be other assaults of this sort. Guerrillas have been using commercial drones since 2015. Islamic State (IS), one of the groups active in Syria, makes extensive use of quadcopters to drop grenades. In 2017 alone the group posted videos of over 200 attacks. IS has also deployed fixed-wing aircraft based on the popular Skywalker X8 hobby drone. These have longer ranges than quadcopters and can carry bigger payloads. Other groups in Syria, and in Iraq as well, employ similar devices. Their use has spread, too, to non-politically-motivated criminals. In October, four Mexicans allegedly linked to a drug cartel were arrested with a bomb-carrying drone.

Cheap shots

Compared with military hardware, drone technology is both readily available and cheap. In 2014 a team at MITRE, a security think-tank based in Virginia, made a military-grade drone using commercial electronics, a 3D-printed airframe and open-source software. It cost $2,000. A whole squadron of such craft could thus be assembled for less than the cost of a single shoulder-fired missile, let alone a modern combat aircraft. America’s F-22 fighter, for example, costs over $300m. A B-2 bomber is even more expensive.

Even a lone drone can do plenty of damage. In Ukraine last year, drones operated by Russian separatists (or perhaps by Russian special forces) attacked several ammunition dumps with incendiary grenades. They destroyed a number of these dumps, in one case setting off explosions which blew up a staggering 70,000 tonnes of munitions.

A growing appreciation of the threat from small drones has led to a rush for protection. Lieutenant-General Stephen Townsend, a former commander of Operation Inherent Resolve, America’s anti-IS campaign, has called weaponised drones “the number one threat facing soldiers fighting IS”. An American navy budget document describes the navy as “scrambling to improve defences against the rapidly evolving capabilities of remote-controlled devices”. Existing defences are not geared up to cope with small drones, which are difficult to spot, identify and track, and which may be too numerous to stop. Jamming might be thought an obvious solution. Breaking the radio links between the operator and the drone, or confusing its GPS navigation, would make a drone crash or send it off course. Many jammers, with names like Dedrone, DroneDefender and DroneShield, have already been employed by various countries. Six of the drones in the Syrian attack were brought down by such jammers, the others by guns and missiles.

Drones are, however, becoming increasingly autonomous. This means there is no operator link to jam. The Syrian drones were vulnerable to jamming because they relied on GPS and so crashed when their link to it was blocked. But new technologies such as optical navigation (which permits a drone to compare its surroundings with an on-board electronic map, and thus to know where it is) will make even GPS jammers useless. Hence the need for “kinetic solutions”, to shoot drones down.

Small drones are surprisingly hard targets, however. Iraqi forces in Mosul used to joke that trying to deal with an IS drone attack was like being at a wedding celebration: everyone fired their Kalashnikovs into the air with no effect. A recent American army manual describes small drones as “very difficult to defeat using direct fire weapons”. A single rifle bullet is likely to miss. A shotgun would work, but only at close range, and would mean that squaddies had to carry around an extra weapon all the time on the off chance of a drone attack. Also, since drones are not of standard sizes, the range to one is hard to estimate. The manual therefore suggests that rather than aiming directly at a drone, the entire squad should fire their weapons at a fixed point ahead of it, hoping to bring the craft down with a curtain of fire. The manual also advises commanders that the best course of action may be “immediate relocation of the unit to a safer location”.

A numbers game

Among other projects, the American army is hurriedly upgrading its shoulder-launched Stinger missiles, which are used to attack low-flying aeroplanes and helicopters. Stingers were not designed to hit small drones, though, so the upgrade adds a proximity fuse which detonates when the missile is close enough to destroy a drone without actually having to make contact with it. Up to 600 “Manoeuvre Short Range Air Defence” teams equipped with these upgraded missiles will join American infantry units around the world. But the upgrades cost about $55,000 each (on top of the basic $120,000 cost of a Stinger), so only 1,147 are being purchased—about two per team, which is hardly enough to tackle a swarm of drones.

Another approach being tried out by the American army is a system called BLADE (Ballistic Low-Altitude Drone Engagement). This fits armoured vehicles’ existing machine-gun turrets with radar guidance and computer control. That should provide some protection, but may still be impotent against a mass attack.

A similar problem applies at sea, where billion-dollar ships might have their defences overwhelmed by squadrons of cheap, jerry-built drones. The mainstay of American naval air defence is Aegis, an orchestrated arrangement of radars, computers, missiles and cannons. The short-range element of Aegis is a Dalek-like, rapid-fire cannon called Phalanx, which spits out 75 rounds a second and can shoot down incoming cruise missiles. This will not cope well with lots of small drones, though. The navy is now upgrading Aegis’s software to handle multiple simultaneous incoming targets by scheduling bursts of fire to destroy as many members of a swarm as possible. It is doubtful, however, whether one gun could account for more than a handful of attackers coming in from all directions at once. An unclassified study suggests that it could be overwhelmed by as few as eight.

Developers of drone-countering measures hope to overcome that by using laser weapons. Lasers hit their targets at the speed of light, have an unlimited supply of ammunition and cost less than a dollar a shot. Though such weapons have yet to achieve their designers’ intentions of being able to shoot down crewed aircraft, they have been tested extensively and successfully against target drones. A variety of specifically anti-drone laser systems are now being developed, including Lockheed Martin’s Athena, Raytheon’s dune-buggy-mounted anti-drone laser, and LaWS, a creation of the American navy itself.

The crucial question is how rapidly such a laser system can spot, track and aim at its target, and how long the beam must play on the target in order to destroy it. The whole process is likely to take several seconds, and until it is complete, the laser cannot move on to repeat the procedure on another target. As with Phalanx, a simple calculation suggests individual anti-drone lasers would be able to deal with only a small number of attackers. If even one drone got through, the laser would probably be the priority target—for destroying it would leave the way open for a subsequent, unchallenged attack.

An American army document from 2016 thus emphasises the importance of stopping drones “left of launch”—that is, before they can take off. IS drone workshops and operators have been attacked to stop the drone threat. The Russians say they destroyed the unnamed group responsible for the mass drone attack in January, along with their drone-assembly and storage facility in Idlib, using laser-guided artillery. But when there are no runways or hangars, and drones can be operated from houses and garages, finding bases to attack is far from easy. Until adequate defences are in place, then, guerrilla drone swarms will be a real danger.