Military & Aerospace

Drone Swarms: The Emerging Air Threat
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Issue Vol. 33.4 Oct-Dec 2018 | Date : 01 Sep , 2019

The threat posed by drones has been acknowledged from the time the first drone took to the air. Efforts have been made ever since to counter the slow, low flying objects, if not to shoot them down. From a rudimentary defence provided by a shotgun used to shoot down a drone overhead to sophisticated Counter Unmanned Aerial Systems (C-UAS) technology has travelled a long way. Today, over 230 C-UAS are available worldwide, up from just ten systems three years back. These systems find use routinely, many a time in public life though seldom is their employment publicised.

On the night of January 05, 2018, and into the early hours of the next day, in an unusual attack, more than a dozen armed drones descended onto Russia’s Khmeimim air base in North-Western Latakia province, the headquarters of Russia’s military operations in Syria. The drone swarm also attacked the nearby Russian naval base at Tartus. The attack by a “massive application of Unmanned Aerial Vehicles (UAVs)” as the Russian Ministry of Defence called it in its press release, is the first announced use of a swarm of drones in military action, but it is unlikely to be the last.

The details made available suggest that, while the Khmeimim Airbase was attacked by ten Unmanned Combat Aerial Vehicles (UCAVs), three more attempted a strike against the maritime logistics base located in Tartus. The Russian Defence Ministry claims that its Air Defence Forces detected the drone swarm “at a considerable distance from the Russian military assets,” and seven of the thirteen drones were then successfully shot down using the Pantsir-S air-defence system.

The US was long considered as the leading nation when it came to swarming drones…

Pantsir-S1 (NATO reporting name ‘SA-22 Greyhound’) is a combined short-to-medium range surface-to-air missile and anti-aircraft artillery weapon system, a further development of 2K22 Tunguska. It is designed to provide point air defence against aircraft, helicopters, precision munitions, cruise missiles and UAVs. The system carries twelve 57E6 or 57E6-E missiles with a maximum range of 20km and two dual 2A38M 30 mm auto cannons which can fire 2,500 rounds per minute per gun, destroying targets up to a range of four kilometres. To counter the remaining drones, Russian radio electronic warfare specialists managed to override their operating systems and eventually gained control over the UCAVs. Three of them were destroyed when they hit the ground, while another three were landed intact outside the base controlled by Russian forces.

The drone swarm could attack the Khmeimim base, the heart of Russia’s military operations in Syria, deep inside Syrian-government-held territory and until now, considered immune to attack because the drones ‘of an aircraft type were launched from a distance of more than 50km, and operated using GPS satellite navigation coordinates’. Though the UCAVs were rather crude, homemade drones carrying small warheads, the coordinated attack by the swarm over long ranges, exposed the vulnerability of military and civilian bases to such attacks launched well outside safe perimeters. This is not the only incident of interest in recent times. Russian media reported two smaller drone attacks against military outposts in the provinces of Homs and Latakia during the last two weeks of 2017.

The incidents reveals that the drone threat, considered low till now, may well be a clear and present danger with the non-state actors possessing the capability to launch such attacks. Although most of the major militaries consider the large Predator and Reaper drones as the face of modern air threat, drone swarms – dozens of fixed-wing drones flying in coordinated formation – could well be the future of unmanned combat. The swarms can take on casualties as also partial failure and still keep going unlike a multi-million manned aircraft which can be shot down, as advanced as it may be. The swarm is difficult to be defeated as the sheer numbers in it can overwhelm the air defences. As Colonel Travis Burdine, the United States (US) Air Force’s Division Chief for unmanned aircraft says, “You have maybe 100 or 1,000 surface-to-air missiles, but we’re going to hit you with 10,000 small drones.”

Even as the swarm acts as a single unit, the drones are not centrally controlled and the individual drone uses software for coordination that mimics the behaviour of flocks of birds. The swarm is given a general instruction such as “search this area”, and coordination within the swarm is automatically done to complete the task. Due to the required software development issues, the US was long considered as the leading nation when it came to swarming drones. In 2015, the Advanced Robotic Systems Engineering Laboratory (ARSENL) claimed a new world record by launching a swarm of 50 drones at Monterey, California – all controlled by the same operator. In 2016, China claimed to have bettered the record by making a swarm of 67 drones fly together at the 11th China International Aviation and Aerospace Exhibition. This was done by the state-owned China Electronics Technology Group Corporation (See video on

As it is composed of basic individual units not capable of independent thought, the swarm cannot predict, it can only react…

Use of UAVs and UCAVs has long been considered as part of the ‘air threat’ as numerous attacks using UCAVs have demonstrated; it is the use of drone swarms that ushers in the paradigm shift in UCAV threat. It will be interesting to study how this threat develops, and the efforts to counter this threat.

Countering the Swarm

The threat posed by drones has been acknowledged from the time the first drone took to the air. Efforts have been made ever since to counter the slow, low flying objects, if not to shoot them down. From a rudimentary defence provided by a shotgun used to shoot down a drone overhead to sophisticated Counter Unmanned Aerial Systems (C-UAS), technology has travelled a long way. Today, over 230 C-UAS are available worldwide, up from just ten systems three years back. These systems find use routinely, many a time in public life though seldom are their employment publicised.

The reasons for proliferation of C-UAS systems are not hard to find. With UAS finding use in almost all walks of life, not only in conflict, there is a serious market out there for people keen to keep the UAS away. So common is the use of drones and C-UAS that seldom do they make news except for a rare occasion. What is generally tried to be covered up is the failure of C-UAS such as the sightings of several drones near and over events during the Rio Olympics even as at least eight C-UAS systems were reportedly used to keep the drones away. As the C-UAS were still at a nascent stage during Rio, such a failure can be understood more so when even the formidable air defence systems fail occasionally to shoot down drones. In July 2016, Israeli Patriot missiles and Air to Air Missiles (AAM) launched from a fighter aircraft failed to bring down a Russian drone which had been launched from Syria and was over Israeli airspace.

Deception may well be best countermeasure to combat drone swarms…

Before looking at the options of countering drone swarms, it will be necessary to first understand the basic characteristics of swarms. A swarm, put simply, is a large number of animate or inanimate things massed together and usually in motion. It is made up of a number of individual elements, grouped together to interact with each other; but they do not have any centralised command nor is there any requirement to control these individually. A group of drones flying together on a pre-programmed route to carry out a fixed task, like the drone attack on Iraqi forces in Mosul by ISSI drones or the attack by over a dozen drones on the Russian base in Syria, do not constitute a swarm.

It will do well to first understand the basic attributes of swarms – they are made up of homogenous elements, the individual elements communicate with each other using simple messages and have minimal contact with each other. The number of individual elements gives the swarm resilience and robustness as a loss of a unit (or a defined number of units) does not affect the overall efficiency of the swarm. As it is composed of basic individual units not capable of independent thought, the swarm cannot predict, it can only react. This greatly limits the efficiency of the swarm and is a key vulnerability.

Analysing further, it is important to look at the challenges that swarms face as they could offer the key to defeating them. A swarm is made up of a number of individual drones. How many constitute a swarm is a rather complex issue. It should be large enough to carry out the defined task with inbuilt redundancy and yet small enough to be survivable (avoid detection) and controllable. Getting the right number in the swarm may well define how to counter the swarm. Kill, or destroy a given number only and the swarm loses its ability to continue its operations as it descends into chaotic behaviour. Remember the units in the swarm communicate with each other and take their cue from the other’s behaviour. If the cues stop coming as there are not enough drones left to communicate, the swarm may well disintegrate. The first key may be that all the drones in the swarm do not need to be destroyed in order to defeat a swarm.

Swarms are designed and pre-programmed to carry out their missions. Reconnaissance may be all right but to carry out an attack, it will need to be given details of the intended target. This will have to be in great details – size, behaviour pattern of the target, the trigger that would initiate the attack. Attack as soon as the target moves? This may be the trigger for the swarm to swoop down and release the weapons of dive on to the target. The problem comes if the target does not move or is more widely dispersed than what the drone swarm was programmed to accept as a viable target. Will the swarm still be able to attack? With present levels in technological sophistication, that possibility is rather remote. On the other hand, this opens a window of opportunity for the defender to employ passive measures such as dispersion and deception to ‘hide’ the target from the swarm. It may be a basic defensive measure, but still effective.

In the absence of any ‘triggers’ and smoke, camouflage and false IR signals to confuse, the swarm may be neutralised without firing a single shot…

A related issue is the use of drone swarms in close proximity of own troops. With similar mass and dispersion patterns, own troops may well present similar target characteristics as the enemy troops. How does the swarm distinguish between the two? If IFF for drone swarms or a confirmatory signal sent to the swarm is used, it offers an opening to the defender to neutralise the attack and counter the swarm. In a similar manner, changing swarm behaviour real time is a challenge and in case Artificial Intelligence (AI) is used to give the ability to the swarm, the ability to predict and react to changing situations, the downside of this ability may restrict its exploitation. It cannot be given across the board to all swarms and yet with limited access also, there has to be an override control lest the swarm turns rogue and becomes a threat to own troops.

Limited access implies that all swarms will not be smart and that itself restricts the ability of the enemy to pose a threat. Also, having an override control means that it can be hacked into and taken control of. If that is done, the swarm can, in turn, be used against the party which has launched the swarm. A remote possibility but it exists nevertheless! Coming to the counter systems, the prime reason for failure of traditional air defence systems is that they are generally designed for use against large, fast moving targets and not drones. Impracticality of using AD systems in C-UAS role is another factor which inhibits their use against drones. After all, using a missile which may cost thousands of dollars against a drone bought off-the-shelf for less than $100 is not the best way to use AD systems.

In addition to the high cost involved in using traditional AD systems, in-built resilience of the UAS is a factor that cannot be ignored while planning counter UAS measures. When C-UAVs were tested in 2017 on drones flying as near as 200 metres, it was noted that the drones were “very resilient against damage”. The continuous advancements in drone technology also make it difficult for the C-UAS systems to be able to detect and neutralise the unmanned systems. The use of counter-laser systems by drones, adapting radar absorbent techniques and programming them to fly in a pattern so as to avoid detection are just some of the challenges C-UAS will have to cater for.

Even in the face of such challenges, a number of existing weapons are quite effective against the UAS. A recent example is the shooting down of UAS by Russian AD systems in Syria discussed earlier. The advantages of using existing systems are understandable – they have proven technologies that may need only tweaking to detect and destroy drones. That is the reason that a number of C-UAS are based on such AD systems. On the other hand, there are systems such as Laser Weapon System (LaWS) which are already operational abroad US Navy ships. Laser weapons are planned to be fitted on US Air Force aircraft by 2020 to shoot down drones. Being a much cheaper option of just about $1 per ‘shot’, lasers are not only economical, but also accurate. Their vulnerability to weather and the time (about 15 seconds) they take to destroy one drone, however, do not favour them as the prime means to counter a swarm of drones. Plus, the range at which the swarm is detected, also limits the effectiveness of the LaWS.

The dependence on detecting the swarm to be effective is self explanatory. The primary means of detection are the use of audio signals, electronic emission, optical, radar, Light Detection and Ranging (LIDAR) and infrared. As most such systems are designed to detect larger targets, they are only marginally effective in detecting drones. Of these, acoustic detectors are of limited efficacy due to environmental noise and range limitations though they do add value to a multi-source drone detection system. Electro-optical (EO) is used today as detect-and-track enablers in many weapons systems though many systems have an IR track capability that augments the EO sensor. The IR system can also be used to detect drones as used in Boeing’s CLWS.

Passive sensing-detecting systems which detect the drones by their emissions have a shortcoming that they are ineffective against non-emitting drones. The best option in any case is to have a multi-sensory detection system using two or more technologies for detection. On clear days, all systems could work together while in adverse weather conditions, radar could still provide inputs. Having detected the drone, there will still be a requirement of destroying the target. The main systems available today are based on traditional AD systems, their designs changed to cater for taking on drones. LaWS, mentioned above, is also an offshoot of the Laser Weapon system originally developed as an AD system. Variants of lasers such as dazzlers are also available as C-UAS systems. Handheld guns, as developed by the Chinese, can be used to shoot down drones; but are ineffective against swarms.

As the key to destroy the swarm is to disable the control system, a more effective weapon against the swarm would be one that uses EM emissions to do so. One example is the US Army’s “Phaser” that identifies enemy drone swarms and beams high-power microwaves at the swarm, destroying the swarms’ control systems. Another system being developed uses smart-bullets that are capable of altering their path mid-flight to engage multiple targets, including UAV and USV drone swarms. Similar to microwave weapons, smart bullets do not require aiming directly at the target, only in the general direction of the swarm. A system that uses kinetic weapons is like a rail gun capable of firing up to 200 rounds a minute to counter enemy drone swarms.

In an entirely different approach to C-UAS, Dutch firm ‘Guard From Above’ trains large birds of prey to intercept rogue drones in mid-flight and claims to have a 95 per cent intercept rate, which is higher than many mechanical kinetic alternatives. The disadvantage is, of course, the numbers that the birds can intercept.

The most effective weapon against swarms is EW systems, a field that Russians lead in. During the raid in January 2018, the Russian Army had used EW systems to neutralise the drones. Though the details of the EW system used are not known, Russia has been testing a number of EW systems in Syria making it the ‘most aggressive EW environment on the planet’. The Russian systems include Krasukha-4 that is designed primarily to counter the radars of attack, reconnaissance and unmanned aircraft. With a range of 300 kilometres, it is capable of jamming not only radar signals, but also control channels for drones.

Susceptibility to cyber attacks and hacking are another vulnerability of drones, more so in the case of swarms due to the volume of electronic links and access points. In 2009, Iraqi insurgents were able to intercept a Predator feed using a $30 software package. Jamming the network used by drones to blind them is very much in the realm of possibility and can and will be exploited by the adversaries.

Oct-Dec 2018: Buy Now

Additionally, drone swarms are vulnerable to static dispersion and deception, as discussed above. An interesting means of drone swarms is to use a defensive swarm to counter it. Faced with an adversary which is as numerous, fast and effective, a drone swarm may simply be overwhelmed. In January 2017, the US Naval Postgraduate School conducted a fifty on fifty drone swarm dogfight to advance effectiveness of drone swarm self-organisation, the result was a tie. Besides US, China is reportedly developing counter swarm swarms as a defensive mechanism.

The last, but in no way the final option, is to simply adapt to the new adversary and shift to “tactically dominant defence” where no individual or unit moves, as in trench warfare. Deception may well be best countermeasure to combat drone swarms. Drones are programmed to recognise patterns (e.g. terrain, movement) and behave according to these patterns. In the absence of any ‘triggers’ and smoke, camouflage and false IR signals to confuse, the swarm may be neutralised without firing a single shot.

As a study of warfare has time and again shown, any advancement has been met with counter measures. No system has remained unchallenged. Maybe the time taken to develop a counter has varied but a counter has always been developed. It is the very nature of humans to adapt and overcome the challenges. So will be the case in the evolution of drone swarms.


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The views expressed are of the author and do not necessarily represent the opinions or policies of the Indian Defence Review.

About the Author

Col Mandeep Singh

An Air Defence Gunner, commanded the Regiment during Operation Parakaram and later along the LAC.

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