In recent times, drone and ballistic missile attacks have increasingly been in the news with one of the most targeted countries being Saudi Arabia which has had to defend itself against weekly drone and missile attacks by the Houthis. The 2019 drone attack by the Houthis using ten drones struck two key oil installations deep inside Saudi Arabia almost 800km from Yemen, was one of the most audacious and devastating drone attack of all times.1 The multi-billion Air Defence (AD) systems operated by Saudi Arabia that included the much-vaunted Patriot missile system failed to protect the Aramco oil installations and brought to fore the challenges of providing AD against emergent air threats.
The repeated and almost weekly drone and missile attacks have exposed ‘a gap’ in the Saudi air defences2 that will only worsen with the withdrawal by United States (US) of its most advanced missile defence system and Patriot batteries from Saudi Arabia.3 The removal of Patriot missile systems is especially significant as it has been used by the Saudis as the mainstay of its AD systems and has come under great stress due to repeated drone attacks. According to a recent report by Wall Street Journal, the situation is so serious that Saudi Arabia is running out of its missile stocks and has urgently appealed to the United States and its Gulf and European allies for a resupply of Patriot missiles.4
The excessive use of missiles that cost $1 million apiece to counter low-tech drones that would not be costing more than $10,000, is another related area of concern for Air Defence as the high ‘cost-per-kill’ cannot be wished away in such an imbalanced state with reliance on high-tech defence that is economically unsustainable in the long run. This begs the question – are there other methods and means for ensuring AD against the new generation threats?
AD is defined as “all measures designed to nullify or reduce the effectiveness of hostile air action” and includes surface-based, sub-surface and air-based weapon systems, associated sensor systems, command and control arrangements and passive measures. Hostile air action is today represented by an increasingly wider spectrum of threats that includes ballistic missiles, subsonic and supersonic land attack and anti-ship cruise missiles. In the future, these will include hypersonic munitions. The emergent air threats pose a greater challenge due to their significant speed, manoeuverability, survivability, accuracy and range. Their capabilities and effectiveness make them “smart” or “complex” weapons, especially from the point of view of a defensive system. Some smart weapons hide amongst terrain features and below the radar, remaining undetected for much of their flight. Others fly through thin atmosphere at higher altitudes where they can reach higher speeds, but aerodynamic steering is still practical. The fastest threats are ballistic missiles that make use of trajectories which arc into space, maximising their range and speed at the expense of stealth.
Due to the similarity of their operations, AD systems that defend against these threats will typically be able to engage a number of such threats, but a related issue of concern is that no one system can cost-effectively defend against all types of threats as a result of which different systems need to be deployed to achieve a semblance of a ‘complete defence’. The Surface-to-Air Missiles (SAM) and AD guns that are the hard kill systems may be better known type of AD weapons systems and the ‘face’ of AD, but they are not the only weapons option for achieving AD. These are the soft- kill systems that are increasingly being fielded by a number of countries to provide AD to their strategic and tactical assets. One of the latest is the Israeli “Scorpius” suite of Electronic Warfare (EW) system which claims to be the first EW system “capable of simultaneously targeting multiple threats, across frequencies and in different directions.”5
What are Soft Kill Weapons?
Soft kill is defined by the US military as “the action or an act of disabling an enemy target without the use of destructive force, especially by disrupting or impairing communication or radar equipment and missile guidance systems, frequently attributive, designating action of this kind or weapons systems used for it.”6
‘Soft Kill’ active defence involves attacking the threat weapon’s sensors, for example, by providing it with a convincing decoy, jamming it or blinding it. Current systems that provide soft kill defence usually take the form of acoustic, radio frequency, microwave, infrared or optical jammers, decoys, obscurants and cyber techniques. Overall, soft kill systems are more common than hard kill systems as they have wide applicability to other military capabilities such as intelligence, surveillance and reconnaissance and they tend to be much more cost-effective.
Why Soft Kill?
Current AD systems that provide hard kill defence usually take the form of high performance interceptor missiles or guns such as the Phalanx close-in weapons system. Both systems are very effective when applied against low numbers of threats of comparable levels of sophistication. However, missiles currently used for hard kill active defence have severe efficiency limitations. They have a high cost per shot, a low rate of fire and a low magazine capacity which generally means that they are less effective when defending against massed or prolonged attacks by less sophisticated threats. Two examples would suffice to highlight these limitations.
In 2018, a Pantsir S 1M Air Defence system operated by the Syrian AD forces was directly targeted and destroyed in an Israeli air strike. What made the loss of a Pantsir S1 unit all the more embarrassing for Russia was that it was being touted as one of the most advanced AD systems and based on its performance in Syria, Russia was hoping to shore up export orders. The excuse given by Aytech Bizhev, the former Deputy Commander-in-Chief of the Russian Air Force was two-fold. According to his assessment, the reason Israel were able to destroy the missile system was that “it had already used up its ammunition reserve. The other is that it was simply turned off; it was not battle ready.”7
The second incident also involved Russian AD systems deployed in Syria. A drone swarm attack in 2019 reportedly strained the Russian AD systems as ten drones rigged with explosive devices descended over Russia’s Hmeimim air base while a further three targeted the Russian naval base in the nearby city of Tartus. The AD systems managed to shoot down seven drones using anti-aircraft missiles while the other six were taken under control and landed by its military. Three of the drones survived the landing.8 While all the drones were all shot down or neutralised, this incident was the first known use of drone swarm and brought to fore the possibility of saturating AD systems in the eventuality of a massed drone swarm attack.9 Russia deployed its most advanced missile system, the S-400 Triumf but it has not used it as yet. The availability of ready-to-fire missiles (four per launcher) is a factor that will have to be considered as and when the system is used against any hostile air action. Leaving the launchers exposed during reload of missiles, will not be what Russia would want during any air attack.10
Two reasons are speculated to be the reason for the same. First, no ‘worthwhile’ targets have been presented as yet as the coalition air strikes declined since the deployment of the S-400. Second is that the system is not as efficient as claimed.11 The S-300s deployed earlier have similarly not been used against Israeli aircraft as yet.12
The other category of hard kill weapons viz AD guns also have efficiency limitations. These have a very limited effective range and a low magazine capacity. Guns usually engage threats only a few seconds before they would strike the defended asset. They have little margin for error and generally result in significant target debris impacting the defended asset. One of the better known AD gun systems i.e. ZSU-23-4B Shilka’s ammunition capacity is 2,000 rounds stowed aboard the mount (520 rounds per each upper auto cannon and 480 rounds per each lower auto cannon) loaded in 50-round or shorter belts. With each water-cooled 23 mm 2A7 auto cannon having a cyclic rate of 850–1,000 rounds per minute for a combined rate of fire of 3,400–4,000 rounds per minute, it gives a continuous fire time of 30-35 seconds before a gun mount runs out of ammunition not considering the constraints that limit the practical rate of fire, such as barrel overheating. The comparably lower range and target handling capability of guns are other limiting factors.
These factors make it imperative that alternative systems be identified and employed to provide effective and economical AD. The soft kill weapons fit the bill in this regard as they are no less effective and given their advantages in terms of easier logistics, they are a viable option. The other inherent advantages are the relatively low cost with a large or almost unlimited quantity of ‘ammunition’ to take on multiple targets. The effective ranges are large enough to provide effective cover and the systems are ‘error forgiving’. The lack of lethal effect and difficulty in damage assessment, however, remain major disadvantages.
The advanced militaries have started integrating soft kill systems with the hard kill weapons to provide layered AD. The USS Kearsarge of the US Navy is a Wasp class amphibious assault ship which had four layers of air defence all by itself, ranging out hundreds of miles with its AIM-120 equipped AV-8B+ Harriers, to tens of miles with its Evolved Sea Sparrow Missiles, to up-close in personal with its Rolling Airframe Missiles and Phalanx close-in weapons system. Missile decoy launchers augment the anti-ship missile defenses. Even with such advanced AD systems, the USS Kearsarge carried a couple of Light Marine Air Defence Integrated System (LMADIS) as it transited through the Suez Canal in order to counter any possible drone attack.13
LMADIS is a highly mobile anti-drone solution that rides on a pair of Polaris MRZR buggies that has been fielded by the US Marine Corps in an effort to augment its AD capability.14 It uses radio signals to ‘shoot down’ hostile UAVs and it shot down an Iranian UAV in its first reported successful use in July 2019.15
The Russians, with experience gained in Syria, have now practically incorporated EW systems as a key element of all counter-UAS drills. In a typical AD setup, it uses R-934BMV automated jamming station, the Silok-01 EW system and the Pole-21 advanced radio suppression system to discover hostile UAVs in order to interfere with their communications and suppress their control channels, rendering them useless for further operations.16
Use of EW systems has been mastered by Russia, more than any other country to devastating effect. Jammers have been used extensively in the conflict against Ukraine and over 100 drones have reportedly been brought down by Russia, using only jammers. In other cases, the Russian systems emitted signals that caused artillery and missiles to prematurely detonate or veer off course.17
Kill Assessment: The main challenge in using soft kill systems is that they pose problems with kill assessment. It is difficult to know promptly and with high confidence that the soft kill attack has worked because it usually does not result in a large explosion and does not necessarily change the trajectory of the threat weapon. Soft kill defences generally interfere with the internal electronics of the smart weapon, so the external appearance of the weapon might remain largely unchanged until it impacts its target and fails to detonate or misses by a small but sufficient distance. The approach adopted by many current systems is simply to continue applying the soft kill defence until the engagement is decisively over and to plan the remainder of the defence assuming that the soft kill approach has failed. This can lead to significant inefficiency.
Mutual Interference: The soft kill systems, if using EW and jamming techniques to neutralise hostile aerial platforms can also interfere with friendly platforms within range of the system. This is a serious limitation unless highly directional jammers are used. This issue was reportedly flagged by the Indian Army and the Indian Air Force during trials of an anti-drone system developed by the DRDO.18
Weapon Allocation: Soft kill weapons use electronics to deflect threats from intended targets, for instance, by jamming or creating an imaginary target. The use of soft kill weapons provides flexibility, but adds complexity to the allocation of weapons to targets since such weapon not only can simultaneously affect multiple threats, but can also adversely deflect a missile from one asset towards another one.19
Integration: The soft and hard kill systems are used in an integrated manner to provide echeloned defence against hostile actions. Integrating diverse systems with varying control and communication needs of different systems is a challenge that needs to be addressed if all the deployed systems have to be optimally used.
The Way Ahead
The threat of saturation of AD systems is real and remains a matter of concern for all military planners. An integrated drone-and-cruise missile operation such as the September 2019 strike on the Abqaiq and Khurais oil facilities in Saudi Arabia, during which none of the 25 drones and cruise missiles were intercepted, is often quoted to be the type of air attacks that would pose the AD challenge in the 2020s.20 A related issue of equal, if not greater concern, is the cost involved in countering low-tech but threats using high-tech AD systems.
The legacy and currently used AD systems will continue to be upgraded as the Indian Army has fielded its legacy L/70 gun system to counter drones, but the limitations in terms of number of targets that can be handled remain.21 The AD challenge cannot be countered by hard kill or soft kill weapons alone and needs an integrated approach which combines the two and uses them in a synergetic manner to ensure optimum level of AD. To do so, traditional and conventional approach needs to be abandoned and new technologies embraced as we go forward. Ignoring soft kill systems is the ostrich-like approach and will only be counter-productive.
Efficient Threat Evaluation, Sensor Allocation and Weapon Assignment (TEWASA) is the key to exploiting soft and hard kill systems.22 Smart threats, the increasingly complicated and diverse air scenarios and the high volume of data needed to be processed necessitate an efficient TEWASA system that is carried out in an automated manner.
- Ben Hubbard, Palko Karasz and Stanley Reed, “Two Major Saudi Oil Installations Hit by Drone Strike, and U.S. Blames Iran”, New York Times, 14 September 2019
- Marc Rod, “Congress takes aim at Iranian drone issue as concerns mount”, Jewish Insider, 13 Dec 2021 accessed 13 Dec 2021 at https://jewishinsider.com/2021/12/congress-takes-aim-at-iranian-drone-issue-as-concerns-mount/
- “U.S. pulls missile defenses in Saudi Arabia amid Yemen attacks”, Politico, 9 Nov 2021 accessed on 13 Dec 2021 at https://www.politico.com/news/2021/09/11/missile-defense-saudi-arabia-511320
- Lubold, Gerald, “Saudi Arabia Pleads for Missile-Defense Resupply as Its Arsenal Runs Low”, Wall Street Journal, 7 December 2021 accessed 13 Dec 2021 at https://www.wsj.com/articles/saudi-arabia-pleads-for-missile-defense-resupply-as-its-arsenal-runs-low-11638878400?mod=hp_lead_pos11
- Watkins, Ronald, “Israel Unveils Multi-Beam ‘Scorpius’ Electronic Warfare System”, Defense Post, 15 November 2021 accessed 14 Dec 2021 at https://www.thedefensepost.com/2021/11/15/israel-scorpius-electronic-warfare-system/
- Lexico Dictionary at https://www.lexico.com/en/definition/soft_kill
- Brown, Daniel, “Russian air defenses were beaten badly by Israeli forces in Syria on video – here are its excuses”, Business Insider, 14 May 2018 accessed 13 Dec 2021 at https://www.businessinsider.in/defense/russian-air-defenses-were-beaten-badly-by-israeli-forces-in-syria-on-video-here-are-its-excuses/articleshow/64164933.cms
- Reid, David, “A swarm of armed drones attacked a Russian military base in Syria”, CNBC, 11 January 2018 accessed on 13 Dec 2021 at https://www.cnbc.com/ 2018/01/11/swarm-of-armed-diy-drones-attacks-russian-military-base-in-syria.html
- Singh, Col Mandeep, “Saturation of Air Defences: Observations on Failure of Air Defence Systems in Syria”, Indian Defence Review, Net Edition, 27 May 2019 at http://www.indiandefencereview.com/news/saturation-of-air-defences-observations-on-failure-of-air-defence-systems-in-syria/
- It takes about 50 minutes to reload the launchers which can be brought down to 25-30 minutes by a highly trained crew.
- Bronk, Justin, “Could Russian S-400s Protect Syria Against Cruise Missiles?”, Royal United Service Institution, 19 April 2018 accessed at Could Russian S-400s Protect Syria Against Cruise Missiles? | Royal United Services Institute (rusi.org)
- Melmon, Yossi, “Why Syria Isn’t Firing Its S-300 Missiles at Israeli Jets”, Haaretz, 15 May 2020 accessed 14 December 2021 at https://www.haaretz.com/middle-east-news/syria/.premium-syria-s-300-missiles-israel-jets-iran-soleimani-hezbollah-1.8841093
- Tyler Rogoway, USS Kearsarge Transits The Suez Canal With Anti-Drone Buggies Keeping Watch On Deck, The Drive, 20 Jan 2019 accessed at https://www.thedrive.com/the-war-zone/26067/uss-kearsarge-transits-the-suez-canal-with-anti-drone-buggies-keeping-watch-on-deck
- “Marine Air Defence Integrated System”, Missile Defense Advocacy, 16 July 2020 accessed at https://missiledefenseadvocacy.org/defense-systems/marine-air-defense-integrated-system-madis/
- Gina Harkin, “Here’s the New Marine Corps Weapon that Just Destroyed an Iranian Drone”, Military, 18 July 2019 accessed at https://www.military.com/daily-news/2019/07/18/heres-new-marine-corps-weapon-just-destroyed-iranian-drone.html
- Samuel Bendett, “Russia’s real-world experience is driving counter-drone innovations”, The Defense News, 14 May 2020 accessed at https://www.defensenews.com/opinion/commentary/2021/05/23/russias-real-world-experience-is-driving-counter-drone-innovations/
- Sébastien Roblin, “Electronic warfare: The U.S. is losing the invisible fight to Russia’s dominant capabilities”, NBC News, 26 Nov 2019 accessed at https://www.nbcnews.com/think/opinion/russia-winning-electronic-warfare-fight-against-ukraine-united-states-ncna1091101
- Philip, Snehesh Alex, “Soft kill or hard kill, there’s no foolproof system to counter drones. India needs R&D”, The Print, 16 July 2021 accessed 14 Dec 2021 at https://theprint.in/opinion/brahmastra/soft-kill-or-hard-kill-theres-no-foolproof-system-to-counter-drones-india-needs-rd/697012/
- Dimitris Bertsimas, Patrick Jaillet & Nikita Korolko, Multiperiod and Online Optimization for Fleet Defense: Centralized and Distributed Approaches, Operations Research Center, Massachusetts Institute of Technology, Cambridge, MA accessed on 13 December 2021 at https://dbertsim.mit.edu/pdfs/papers/2017-korolko-multiperiod-and-online-optimization-for-fleet-defense.pdf
- Ben Ho, “Air Defence Challenges in the New Decade”, Asian Military Review, 14 May 2020 accessed 14 Dec 2021 at https://www.asianmilitaryreview.com/ 2020/05/air-defence-challenges-in-the-new-decade/
- Saxena, Lt Gen VK, “An Important Milestone Achieved Quietly”, Indian Defence Review , 13 Nov 2021 accessed 14 Dec 2021 at http://www.indiandefencereview.com/spotlights/an-important-milestone-achieved-quietly/
- Dinç, Mustafa. (2018). Threat Evaluation, Sensor Allocation and Weapon Assignment (TEWASA). 10.13140/RG.2.2.34564.58245.