A widening range of methods are being fielded to take down UAS depending on their size.
Unmanned Aerial Systems (UAS) offer new threats as well as new capabilities to the military, law enforcement, security and commercial applications. At least 95 counties and groups have versions of UAS ranging from the sophisticated and expensive systems designed to fly at extreme altitudes for extended periods down to the simple and inexpensive hobby-type systems. The latter, referred to as Groups I and II (those under 55kg), range from those small enough to fit in the palm of the hand to larger ones weighing a few kilograms with limited payload range and endurance that are locally controlled.
These readily available UAS platforms are proliferating rapidly creating challenges both on the home front and over all areas where the military operate, from the battlefield to rear support and logistics areas. Colonel David E. Shank, Commandant of the US Army Air Defence Center and School explains: “The UAS adds a new dimension to the aerial battle. The Group I and II have proven to be particularly adaptable in responding to countermeasures. They have rapidly changed tactics and control mechanisms to reduce vulnerability while still achieving their mission capabilities. As a result developing equally adaptable defeat solutions has been a near term priority.”
Originally introduced as primarily an information gathering system, the UAS grew more capable through the introduction of more precise navigation using GPS, improved flight controls, and greater payloads. These allowed fitting of higher resolution cameras and laser rangefinders enhancing their surveillance and permitting them to provide targeting information for artillery. “The effectiveness of combining the UAS and indirect fires was well demonstrated by the Russian’s in the Ukraine.” Col Shank shared, “as a new and important element of combined arms warfare.”
Perhaps inevitably, UASs were ‘jury-rigged’ to carry and crudely drop improvised explosive devices. Typically, as used by ISIS fighters in Mosul, these were hand grenades with fins fastened by duct-tape. However, on 14 September 2019 a tactically coordinated attack entirely by unmanned systems occurred on Saudi Arabia’s state oil group Aramco’s sites at Abqaiq and Khurais. A mixed formation of cruise missiles and small drone UASs approached undetected by sophisticated, advanced air defences. Programmed to fly hundreds of kilometres along remote routes they were able to attack from unexpected directions simultaneously striking critical facilities. Douglas Barrie, an air power fellow at the International Institute for Strategies Studies (IISS) stated that “the level of complexity of this attack is above all that we have seen before. It raised a question mark as to the quality of the protection available against UAV / drone attacks. The fact is that complex networks of air defence radars linked to guided missiles and advanced fighter jet squadrons are not designed to counteract this relatively cheap and disposable technology.” If there ever was a question about potential tactical value and seriousness of the threat the UAS posed this attack resolved it.
Luke Layman CEO of MyDefence North America explains that “UAS operations create third-dimension awareness… with unmanned systems being used for tactical operations that range from deception and disruption to surveillance and kinetic response. Force protection and critical infrastructure managers must include these in their planning considerations… they now must be aware of what they can’t see- and more importantly, what can see them!” One of the unique challenges in countering the UAS is the wide number of ways it can be employed and the quite different conditions faced in each potential scenario. Addressing a UAS operating in an urban civilian environment needs to consider the possibility of unintended collateral damage that might occur when taking it down. Similarly, providing continuous all-around protection to a fixed site requires an entirely different platform and performance than offering the same coverage to a moving convoy or a tactical military unit. The appropriate countermeasure differ in a peacetime versus combat scenario even between that faced in a terrorist incident, insurgency and peer-on-peer warfare. As a result the litany of possible approaches to defeating the UAS has of necessity needed to be broad. However, the principles in defeating the UAS in every scenario remain the same: Detect & Track, Decide (Identify /Characterise), Target and Defeat.
The Group I, II and many III UASs are designed to operate at low altitudes. Often flying to blend with the terrain, trees and building of its surroundings or flying well above the ground where its small size and quiet operation make it inconspicuous. Lee Dingman, president and COO at Ascent Vision explains that the “initial detection of a UAS can be extremely difficult as they typically have very low visual and aural signatures“. A field assessment of multispectral technologies ability to find UAS’ in flight conducted by the Faculty of Military Technology, University of Defence in the Czech Republic found human eye detection was only reliable inside 100 metres. Even thermal cameras and acoustic devices were effective only to around 350m when required to observe a broad area. Despite their very low radar cross-section (RCS), radar still provides the best detection ranges. In trials, X-band radar provided detections at around 3000m. As an element of its Xpeller Counter UAS system, Germany’s Hensoldt utilises its SPEXER 360 X-band Doppler radar which is optimised for small target detection even in cluttered backgrounds. Company spokesperson, Carina Englehardt, stated that “the system at 44 pounds (22 kilograms) is lightweight yet able to offer maximum protection under a variety of conditions and ranges. “ It will detect a Micro UAS with a 0.03m² RCS at 1.6km but also other low and surface targets like a man (which has a 0.5m² RCS) at 4km or truck (10m² RCS) at 8.4km. Thus, the system is also able to offer full intrusion detection against both ground and aerial threats.
The Czech field tests further demonstrated the need for both rapid and accurate detection and confirmation at the greatest range. What became clear is that the UAS is a dynamic target always in motion presenting a nimble and often momentary target. Even with a moderate flight speed of about 10–15 meters per second (mps) a UAS can quickly close a distance of 300 meters in only 20–30 seconds. It can, thus, quickly evade, move beyond detection, or be on top of or beyond an observer virtually in seconds. The detect to decision chain must, therefore, be rapid and precise to have any relevance. The challenges posed by the small UAS are more analogous to those of detecting and tracking rockets and artillery and mortar projectiles in flight – referred to as C-RAM – than to systems targeting conventional airborne platforms. “Recognition of this influenced the selection of the KuRFS radar for our Howler CUAS system” relates Don Sullivan, chief technologist at Raytheon Missile Systems. He explains: “the UAS is particularly difficult to find and track. Not only are they often a small target but they are flown at low altitudes that present a clutter or false signal returns for radar. The Ku radar is already proven in detecting and tracking incoming projectiles in C-RAM, thus, has also been particularly effective against these small UASs as well.”
Ascent Vision’s X-MADIS and E-MADIS employ pulse Doppler S-Band radar with four fixed ‘staring’ antenna each with 90 degrees spatial coverage oriented to provide all-around surveillance. Dingman shared that the system can not only provide nano UAS detection at 3.5m but also larger UAS’, fighter aircraft and helicopters at up to 25-30km for the later. An additional advantage is that coupled with the company’s software it is able to track and correlate multiple threats including UAS swarms.
Determining that a possible threat is present it must then be confirmed, positively identified and classified prior to any counter action. Experience has demonstrated that presently radar must be complemented with electro-optics and electronic radio frequency monitoring to acquire and then confirm the detection is, in fact, a target of concern, accurately identify it and assess the nature of the threat. In the process target tracking and engagement options and targeting solutions will be determined. The complexity of the environments in which the UAS operates often requires the use of multiple sensors to accomplish this. In the University of Defence trials optical tracking and discrimination of the UAS proved highly efficient particularly for thermal IR heat sensing devices using narrow field of view (NFVO)/high magnification. However, use of the NFOV made initial capture of the target image problematic without outside azimuth designation.
Defeat – Soft Kill
With a positive threat confirmation and identification the UAS must be neutralised. This can be by physically engaging and destroying it in a ‘hard kill’ or by neutralising it in a ‘soft kill’. The later, referred to as non-kinetic most often is directed to disrupting the UAS’ operation by jamming or deceiving its controls, navigation signals or operator data link causing it to crash or be hijacked and captured. Raytheon’s MESMER even seeks to manipulate its radio frequencies to control a hostile drone. These techniques can be less effective where the UAS has autonomous navigation and is programmed to default to return to a safe landing point should positive control be lost. Most soft-kill utilise electronic warfare jammers intended to disrupt control of the UAS or, as Luke Layman points out, “even the pre-programmed course UAS likely has a data link to send video which can be interrupted”. A principle concern with signal jamming is the possibility that other radio frequencies not associated with the targeted UAS could also be affected. This is especially sensitive concern in security in public and dense populated areas.
In many potential situations a portable counter-measure is highly desired if not essential. Rifle style systems like DroneShield of Australia’s handheld DroneGun Tactical UAS disruptor carried by a single person can fill this requirement. Directed precisely at the target, they simultaneously disrupt RF control frequency bands, the GNSS capability (GPS, GLONASS), and can cut off the video link to the UAS controller. Oleg Vornik, chief executive office at the company shared that “the system forces drones into a fail-safe mode where they cannot be controlled by the operator.” Another handheld jammer with 1km range, the ORION-H, was recently presented by TRD Singapore. It is a man-portable model of a family of ORION systems including backpack, stationary and vehicle mounted solutions.
Another approach is to employ one’s own UAS to intercept and capture or down a hostile drone in these scenarios. Selex ES in the United Kingdom, a Leonardo company, offers its Falcon Shield designed to actually allow its operator to commandeer the UAS’s controls and make it land safely. The Dutch firm Delft Dynamics’ Drone Catcher is a quad-copter UAS with integrated camera with image recognition and tracking and a special pneumatic “net gun”. Manoeuvred to within 20m of the targeted UAS it locks-on and then launches a net that captures the opposing UAS.
Defeat – Kinetic
Kinetic kill seeks to destroy the UAS or physically disable it. More often the selection for this has been an automatic firing weapon in a remote weapon station. These range from a Dillon Aero 7.62mm six barrel electrically powered Gatling type gun capable of 3000 round per minute, to the venerable M2 .50cal machine gun, and the 30mm M230LF auto-cannon. The later has become increasingly viewed as the weapon of choice. This preference will likely grow with the introduction of proximity fusing which would be demonstrability more effective against the UAS. Jarrod Krull, a Northrop Grumman spokesperson, shared that the company has such proximity ammunition for the 30mm which is undergoing Army certification. The advantage of ballistic weapons in the combat area are their inherent ability to engage other targets as well. Raytheon’s Howler takes another approach using its expendable, tube launched high speed Coyote missile, itself a form of turbo-jet propelled UAS, to execute the kill. It is coupled with the KuRF radar proven in the C-RAM role. It is being fielded by the US Army initially in a truck mounted form for site defence.
Another possibility is the use of directed high power microwave energy which can incapacitate a UAS immediately by disrupting it’s electronics. It is directional and can have a narrow or wide beam with the later ideal for dealing with the multi-drone swarm attack. At the US Army 2018 Manoeuvre Fires Integrated Exercise (MFIX), a Raytheon High Energy Microwave (HEM) shot down 33 drones in groups of two or three. Michael Hofle, the company’s Product line director explains: “The high-power microwaves are really effective with a large swarm [of drones], because they have a large cone of effect”. Another Air Force demonstration in September 2019 lead to the deployment of its Phaser HPM from Raytheon for field experimentation in airfield defence. Using an ISO container it is less suited for tactical use, however, Liedos is developing its TIGER (Time Integrated Gigawatt Electromagnetic Response) man portable system.
Major investments are also being made in lasers. Given current power limits the smaller TUAS is a target that it is actually capable of addressing. In 2018 Boeing demonstrated a 5kW laser on the General Dynamics Stryker 8×8 armoured vehicle under the title of Mobile Expeditionary High Energy Laser (MEHEL). Its Compact Laser Weapon System (CLWS) was developed for a US Marine evaluation integrated onto the M-ATV. Raytheon’s HEL (High Energy Laser) has also been successfully demonstrated at the US Army Manoeuvre Fires Integrated Exercise (MFIX 2018), shooting down a dozen manoeuvring drones. At the 2019 MFIX, Kord Technologies of Huntsville, Alabama showed its 5kW Mobile Expeditionary High-Energy Laser (MEHEL) on a Stryker. More recently in October 2019 Raytheon provided the US Air Force with a 10kW-class HEL mounted on a Polaris all-terrain vehicle. It is a major step forward toward a workable tactical laser weapon system since it integrates a multispectral optical and infrared aiming system, laser cooling, and sufficient power for the laser (using 220-volt batteries originally built for electric race cars) on a compact mobile platform. Hofle suggests that “the laser and microwave systems are complementary. The former has longer range and better precision, so it can focus tightly to detonate an explosive payload or cripple targets that slip through defences.”
An advantage of the laser is it can engage targets with less concern over replenishing ready ammunition. On the other hand current lasers require a dwell time on target to inflict sufficient damage to down it, reducing the system’s ability to rapidly address multiple targets in succession. In addition these lasers are effective only in engaging these Group 1 and 2 UAS limiting their overall tactical utility.
UAS and CUAS Future
The UAS is both a useful asset and a significant threat for the foreseeable future. A February 2018 report from The Centre for the Study of the Drone at Bard College in Annandale-on-Hudson, New York, stated “drone technology itself is not standing still, Drones might be designed to reduce their radar signature. Counter-laser systems could protect drones from directed-energy attacks. Finally, forces might seek to deploy drone swarms, which present a range of vexing technical challenges”. That there is a distinct difference between solutions appropriate for countering civil security threat challenges and those of the battlefield must also be recognised. In the former the focus on simply addressing the UAS itself is acceptable. However, in the latter the UAS is assuredly becoming a new and integrated element of the larger combined arms. Therefore, the CUAS systems fielded must be similarly integrated and able to respond to all battlefield challenges if they are to be effective in combat.