The threat posed by drones has been acknowledged from the time the first drone took to flight and 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), the technology has travelled a long way. Today over 230 C-UAS are available worldwide, up from just 10 systems available three years back. These systems find use routinely, many a time in public life though seldom are these uses publicised.
The reasons for proliferation of C-UAS systems is 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 like 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 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 Missile(AAM) launched from a fighter aircraft failed to bring down a Russian drone over Israeli airspace which had been launched from Syria.
Before looking at options of countering drone swarms, it may well be to first understand the basic characteristics of swarms.
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 that interact with each other but do not have any centralized command nor is there any requirement to control the individuals. 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 basis attributes of swarms, that they are made op of homogenous elements, the individual elements communicate with each other using simple messages and have minimal contact with each other. The numbers ( of individual elements) give the swarm resilience and robustness as a loss of a unit(or a defined number of units) does not effect the overall efficiency of the swarm. As it is composed of basic individual units not capable of independent thought, the swarm cannot predict but 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 problem. 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 the cue from its behaviour from 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 not all drones need to be destroyed to defeat a swarm.
Swarms are designed and pre-programmed to carry out their missions. Reconnaisance 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 suppose 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 is technological sophistication, that possibility is rather remote. On the other hand, this opens a window of opportunity for the defender to employ passive measures like dispersion and deception to ‘hide’ the target from the swarm. It may be a basic defensive measure but still effective.
A related issue is use of drone swarms in close proximity of own troops. With similar mass and dispersion patterns, own troops(friendlies) 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 give across the board to all swarms and yet with limited access also, there has to be an override control lest the swarm goes 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 costs thousands of dollars against a drone bought off the shelf for less than 100 dollars 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 UAS is a factor that cannot be ignored while planning counter UAS measures. When C-UAV 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 absorbant 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 with such challenges facing them, a number of existing weapons are quite effective against UAS. A recent example is the shooting down of UAS by Russian AD systems in Syria (discussed in Drone Swarms Part I). the advantages of using existing systems is understandable- they have proven technologies that may need only a 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 like Laser Weapon System(LaWS) which is already operational abroad US Navy ships. Laser weapons are planned to be fitted on US Air Force aircraft by as early as 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 that use 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 multisource 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 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 input.
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 like 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 warms.
As the key to destroy the swarm is to disable the control system, a more effective weapon against the swarm would be 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 railgun capable of firing up to 200 rounds a minute to counter enemy drone swarms.145
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 claim to have a 95 percent 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 the Russians lead in. During the raid in January 2018, 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 kilometers, 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 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.
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, fats 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- organization, 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 last option, is to simply adapt to the new adversary and shift to “tactically dominant defense” where no individual or unit moves, as in trench warfare.Deception may well be best countermeasure to drone swarms. Drones, are programmed to recognize patterns (e.g. terrain, movement) and behave according to these patterns. In 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 remain 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 in case of drone swarms.
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