Guidance

Countering drone threats to shipping

Published 20 May 2024

Overview

Aerial drones, often called uncrewed aerial systems (UAS), are a rapidly increasing aviation technology with widespread global use in multiple domains. Aerial drones are manufactured in a range of different sizes from small toys to hobbyist units, to specialised commercial units and large military drones. Each drone type provides varied capabilities, which are developing at pace, supporting their use for both civilian and military purposes. Benefits of their use include providing safer and more cost-effective ways of carrying out activities while having a lower environmental impact than traditional solutions.

Aerial drones offer many use cases for the civilian maritime industry, including but not limited to:

• inspection and surveying assets – for example, inspecting the hull or mast of a ship, or port infrastructure, as part of an asset maintenance program, reducing the need for people to access hazardous areas
• cleaning difficult to reach areas of a vessel
• capturing images and recording videos of a vessel for media advertising purposes
• monitoring emissions and taking air quality readings in busy shipping lanes and near ports
• supporting search and rescue missions in maritime emergency situations
• delivery of cargo such as critical spares or medical supplies as part of logistics for shipping operations

However, their accidental or deliberate misuse can present threats to commercial maritime vessels. Aerial drones have been used maliciously in events that have led to disruption and harm. An extreme example of this is using military grade or weaponised commercial drones, as seen in the attacks on the MV Mercer Street and the Pacific Zircon vessels.

While aerial drones can be used to present threats to commercial maritime vessels, there are a range of mitigations available. However, these need to be proportionate to the anticipated threat and should be fully assessed to determine if they will provide a net positive benefit to a maritime organisation, as each mitigation option carries strengths and weaknesses.

Scope

This guidance is intended to help the maritime industry to understand aerial drone technologies, the potential threat to maritime vessels and options to mitigate the threat. It focuses on aerial drone threats and associated response options.

Aerial drones considered in this guidance include systems of a commercial nature such as ‘small’ commercially available drones that are less than 20kg in weight as defined by the Civil Aviation Authority (CAA), or weaponised drones (sometimes referred to as loitering munitions) such as the Shahed 136 loitering munition.

Threats and response options for other types of drone, such as amphibious drones, surface or subsurface remotely controlled autonomous vehicles, swarms of aerial drones (for example, 2 or more drones flying in a coordinated manner by a single operator), and large scale, military aerial drones such as the Thales Watchkeeper WK450, Baykar Bayraktar TB2 and General Atomics MQ-9 Reaper, are out of scope for this guidance. Threats from, and response to, military anti-ship missile systems are also out of scope.

Introduction to drone technologies

Drone systems in the context of this guidance are remotely controlled or autonomous aircraft without any human pilot, crew or passengers onboard.

Aerial drones, interchangeably called Uncrewed or Unmanned or Unpiloted, Aircraft or Air or Aerial, Systems (UAS) or Remotely Piloted Aircraft System (RPAS), can be used not only for a wide range of civilian but also several military use cases including reconnaissance and weapons deployment.

Typical components of a UAS as defined by the National Protective Security Agency (NPSA)

Drone or uncrewed aerial vehicle (UAV)

A flying aerial vehicle, typically with multi-rotor or fixed wing configurations, which can carry a payload (such as a camera). Typically used to either capture data (such as images, videos, survey data) or to carry and deploy a payload (such as medical supplies, weapons, herbicides for crop spraying).

Command and control signals

Signals transmitted and received by the drone and its controller, to direct flight activity and in some cases, transmit data such as live video feeds and flight data back to the pilot.

Smaller drones are typically controlled by radio frequency (RF) systems using wifi or Industrial Scientific Medical (ISM) frequencies. Control using 4G or 5G telecommunications networks is becoming more common, to increase the range of connectivity between the drone and its operator, resulting in increased drone operational ranges, including when flying at sea and away from coastlines.

Larger, more expensive drones may use satellite links and more sophisticated control systems.

The frequencies and signal strengths used will be dictated by local regulations and vary around the world.

Controller or ground control station

The system transmits control signals to the drone to allow a pilot to control and direct the drone’s activity and to receive data from the drone itself, such as live video feeds.

Additional elements typically involved in a drone flight include the following.

Pilot(s)

The person responsible for controlling the drone, from take-off and flight to landing. Typically, in the UK the pilot requires a CAA licence and registration, depending on the type of drone used and drone operations planned.

Geographical information system (GIS)

A system used to process data transmitted from the drone, to help the pilot and end user make informed decisions. For example, for flight planning, monitoring video feeds from the drone, monitoring ‘near real time’ GPS location tracks of the drone’s flight path or post processing scans of an area of land to form a 3-D model.

Current aerial drone technologies

Aerial drone systems can be found in many shapes and sizes, from small toys to commercial products to military platforms. Typically, the larger the drone, the more advanced its capabilities. There are many different standards and classification systems for drones, including those from the European Union Aviation Safety Agency (EASA).

A simplified summary of typical drone capabilities

Small hobby drones including toy drones (EASA class C0)

No payload (load carrying capability), weight less than 250g with maximum speeds of approximately 68km/h and a maximum range of 120 metres from the controller under the C0 regulations. Some small drones may be able to far exceed these limits.

Expensive hobby and small commercial drones (EASA class C1)

Less than 900 g including any payload, with speeds of up to 68km/h under the C1 regulations, they typically have GPS enabled flight and advanced sensors such as collision avoidance technology and high-definition cameras. They are usually operated within visual line of sight (500m), but many are capable of operation over a few kilometres.

Professional commercial drones (EASA class C2)

Less than 4kg including payload carrying capabilities, some are capable of speeds in excess of 80km/h and operation at ranges of several kilometres, depending on local regulations. Often used for professional photography or survey work they have GPS enabled flight and advanced sensors such as collision avoidance technology and can often be fitted with specialist cameras and sensors, including thermal imaging systems.

Large commercial drones (EASA class C3)

Less than 25kg including payload carrying capabilities, these include high-cost drones for specialist applications including cinematography, mapping, agricultural spraying or delivery. As such, they may have a wide range of operational capabilities depending on the intended application.

Drones regulated as traditional aircraft (EASA class C4)

Drones greater than 25kg potentially with significant payload carrying capabilities. They would typically be required to comply with the same regulations as traditional aircraft, with capabilities commensurate with general aviation.

Military drone

A wide range of drones are used by the military, from micro drones to very large platforms with high payload capacity (100kg or more), often designed with advanced sensors, positioning systems, power sources for long endurance (hours of flight), high speeds (140km/h and over) and long ranges (can be up to thousands of kilometres).

Aerial drones are typically manufactured as either a ‘multi-rotor’ configuration (such as commonly available quad copter drones) or a ‘fixed wing’ configuration. Specific weaponised drones can also be produced such as the Shahed 136 loitering munition. Each offers a range of strengths and use cases due to their varying capabilities. Further details for each configuration type are given in the following sections.

Multi rotor drones

Multi rotor drones are the most common drone type due to their commercial availability, flight stability and ease of use. They often incorporate technologies such as collision avoidance sensors and accurate GPS positioning systems, allowing them to be flown by pilots with minimal experience or training.

In multi rotor systems, such as quad-copters or hexa-copters, lift and thrust are produced by rotatory propellers rather than wings, allowing vertical take-off and landing (VTOL), stable flight control and hovering capabilities.

Due to their range and endurance, multi-rotor drones are more likely to be seen near ports or docks in the maritime domain. For example, a drone used to conduct a search and rescue mission near the coastline would need to stay within the communication and video transmission range of its pilot and ensure it has battery life to return to home.

Example multi rotor drone capabilities and use cases include:

• payload delivery – flying to a target and delivering a payload such as medical supplies to the deck of a ship
• videography – taking off from a ship, hovering and taking images and videos of a picturesque location, or for advertising purposes
• search and rescue – providing aerial footage of an emergency scene off a coastline including use of thermal imaging to find people at sea, even hovering above the event and dropping buoyancy aids, thus supporting local emergency services
• precision spraying – equipping the drone with cleaning products and flying to a difficult to access location to carry out cleaning
• emissions monitoring – equipping the drone with air quality reading sensors and deploying it to monitor emissions levels, as conducted by drones in the Strait of Gibraltar
• survey and inspection – equipping the drone with camera or specialist sensor payloads, flying to a hazardous location and recording images/scans to inform maintenance plans, removing the need for people to enter hazardous environments

Example multi rotor drone platforms and their specifications include:

• hobbyist multi rotor drone: DJI Mini 3 Pro (take-off weight <0.249kg, maximum flight time 34 minutes, maximum speed (at sea level, no wind) 56km/h, size unfolded width with propellers 0.362m)
• commercial multi rotor drone: DJI Matrice 300 RTK (maximum take-off weight 9kg, maximum flight time 55 minutes, maximum speed 83km/h, size unfolded propellers excluded width 0.670m)
• military multi rotor drone: Lockheed Martin Indago 3 (take-off weight with payload included 2.26kg, 50 to 70 minutes endurance with payload, Aircraft Datalink range 10-12km)

Multi rotor drones can be flown using several operational modes, as follows:

• radio link and GPS – flown directly by a pilot using a radio link (for example, wifi, 4G, 5G) and, if required, flying using a pre-planned flight path of GPS waypoint coordinates
• tethered power supply – multi rotor drones can also be tethered to a ground-based power supply and control link, to provide greater endurance for extended flight in a fixed location – for example to hover above a location and act as a mobile CCTV tower
• first person view (FPV) – FPV flying is where a pilot wears a headset showing a forward-facing camera feed from the drone, which can provide additional situational awareness to aid pilot control, especially where visual line of sight is blocked or when navigating obstacles
• perch and stare – some multi rotor drones can be operated in ‘perch and stare’ modes, where the drone flies to a target, lands and discreetly records video or intercepts signals while stationary before taking off and returning to its operator

Fixed wing drones

Fixed wing drones use a set of wings to generate lift and control flight like conventional aeroplanes with propellers used to provide forward thrust. They sometimes need a catapult launcher system or smaller systems may need to be thrown to get airborne. Fixed wing drones offer long range, high speeds, and endurance (flight time), but they are unable to hover or land vertically.

Due to their range and endurance capabilities, fixed wing drones are more likely to be found at sea in the maritime domain, where they can be launched from a coastline or ship to conduct a mission many kilometres away.

Example fixed wing drone capabilities and use cases include:

• long range delivery of payloads – carrying and delivering medical supplies to remote locations
• surveying landscapes, assets and infrastructure – taking images, videos and 3-D scans of coastlines, infrastructure or buildings using cameras and optical sensors, including LiDAR technology to create 3-D digital models
• reconnaissance – flying to and around a large target, capturing images and videos to provide intelligence for a mission

Example fixed wing drone platforms and their specifications include:

• hobbyist fixed wing drone – Talon GT Ready To Fly Drone (weight 1.1kg, up to 15km range, up to 45 minutes flight time, maximum flight speed 100km/h, payload capability 0.3kg)
• commercial fixed wing drone – Windracers ULTRA Drone (nominal endurance 12+ hours, cruise speed 135km/h, maximum take-off weight 450kg, payload up to 100kg and up to 1,000km distance). Designed for delivery of medical and other supplies.
• military fixed wing drone – AeroVironment RQ-20B Puma AE (3+ hours flight endurance, speeds up to 83km/h, weight 6.3kg, 20km range)

Fixed wing drones can be flown using several operational modes, as follows:

• radio link and GPS – flown directly by a pilot using a radio link (for example, Satellite, wifi, 4G, 5G) and if required, flying using a pre-planned flight path of GPS waypoint coordinates
• first person view (FPV) – FPV flying also exists, where a pilot wears a headset showing a forward-facing camera feed from the fixed wing drone, providing additional situational awareness to aid pilot control

Hybrid systems are starting to appear in the commercial drone market, capable of taking off like a multi copter and then transitioning to fixed wing flight, providing a versatile long-range system capable of hovering and landing in confined areas.

Loitering munitions and military drones

Drones equipped with explosives and targeting capabilities can be used to act as Loitering Munitions – where the drone flies to a target area, waits or loiters, then attacks the target by flying into it, causing an explosion and damage. These are sometimes referred to as kamikaze drones or one-way attack drones. Loitering munition drones have been used to attack maritime vessels such as attacks by HESA Shahed 136 drones on MV Mercer Street1 and the Pacific Zircon vessels.

Further information on loitering munition threats can be found in the Oil Companies International Marine Forum (OCIMF) document Loitering Munitions – The Threat to Merchant Ships.

Due to their range and endurance capabilities, loitering munitions pose a greater threat at sea than commercial drones with improvised explosive payloads as they can conduct an attack many kilometres from shore. However, they could also be used at shorter ranges, for example to attack a docked vessel in port.

Military drones can be found in a range of configurations, including as fixed wing and multi-rotor drones and are increasingly used around the world. They can have sophisticated sensor systems and may carry weapons including missile systems. These are considered to be outside the scope of this guidance and any threats they pose will require military grade countermeasures. In some regions commercial drones are being modified to act as military platforms or loitering munitions.

Example loitering munition use cases and capabilities include:

• loitering munitions attack vehicle – carrying explosive payloads and flying directly into a target to cause damage and disruption such as using a Shahed 136 to attack and damage a commercial maritime vessel
• reconnaissance – flying to and around a target such as a ship, capturing images and videos to provide intelligence for a mission – for example, to identify vulnerable areas of the vessel at which to direct an attack

Example loitering munition platforms and specifications include:

• Shahed 136 (approx. 200kg, low radar signature due to delta-wing design, low altitude flight profile (max 1,000m), estimated extensive flying range to be as much as 3,300km)
• AeroVironment Switchblade 600 (40+ km range, 40+ minutes endurance, loiter speed 113km/h, sprint speed 185km/h, 15kg munition weight)

Future drone technologies

Drone capabilities continue to develop at pace, including an emerging airspace infrastructure market of software and hardware systems increasing their versatility, capability, range and load carrying ability. Even small drones are increasingly being developed with many of the sophisticated capabilities once only available on high end systems. Example future drone technologies to be aware of include the following.

Artificial intelligence (AI)

Use of AI for increasing flight stabilisation and control, decision making and data processing, such as more accurate navigation in difficult weather conditions and targeting for precision payload delivery including automatic target recognition.

Navigation systems

Many drones currently rely on GPS to provide location data. Increasingly, drones are emerging with capabilities to determine their location with other technology including inertial navigation, terrain and target recognition cameras or alternative satellite systems to increase their navigation resilience. 

Battery developments

Drone power sources and system efficiencies continue to develop, offering greater range and payload capabilities, which could lead to longer flights at sea and heavier or more complex payloads. Use of alternative power sources, including hydrogen fuel cells, which can further increase flight range is starting to be seen on commercial drones.

Uncrewed traffic management (UTM)

UTM technology is being developed to allow management of the airspace where drone activity is taking place. These systems allow airspace management to plan commercial drone flight paths, deconflict routes, monitor flight activity in a region and respond to unplanned or emergency events. This is intended to enable greater drone use, including in areas such as ports and docks, in a planned, communicated, and transparent manner. In some regions, stakeholders such as vessel crews may have access to UTM details of authorised drone activity in their vicinity. UTM is sometimes referred to as unified traffic management, where drone airspace management is combined with general aviation air traffic control (ATC).

Remote identification (RID)

In some regions, requirements for drones to broadcast flight data are being introduced, in a similar manner to automatic identification system (AIS) in shipping. The RID system typically comprises a transmitter on a drone (sending the data such as flight coordinates, speed and direction), which can be received using a small device or via an internet app. This technology could be used in the future to support maritime operators deconflict between legitimate and threat drones flying near one of its vessels.

Beyond visual line of sight (BVLOS) flying

In many countries, most small commercial drones are required to fly within the visual line of sight (VLOS) of the pilot, mainly for safety reasons. Beyond visual line of sight (BVLOS) flying allows commercial aerial drones with greater flexibility and operational capabilities. Technologies and regulations are being developed in many areas to enable BVLOS operation. Most drones already have BVLOS flying capabilities, but such operations can be limited by local regulations.

Electric vertical take-off and landing (eVTOL) aircraft

Sitting somewhere between helicopters and heavy lift drones, eVTOL aircraft are starting commercial operation in several parts of the world, including their use as ‘drone taxis’. These can provide rapid transit to port areas and potentially provide ship to shore transport in the future, thereby providing an alternative to helicopters. As the technology develops these will be remotely or autonomously piloted in the same manner as drones, but with human passengers. Such systems may appear to be large drones from a distance, further raising concerns over the appropriate use of some counter drone technology.

Drone threats to commercial maritime vessels

Aerial drones can be used to pose a wide range of threats to ships, ranging from minor harm due to inappropriate use by passengers, to criminal activity and up to state sponsored terrorism at the extreme. These threats are often similar in nature to conventional threats, but involve the use of a drone as a tool. For example, drones can be used as a different attack vector to deliver explosive threats as an alternative to water borne improvised explosive devices (WB-IED) or anti-ship missiles (ASM) to damage a vessel. In that example, an aerial drone could be operating as a loitering munition involving a weaponised commercial drone, or using a purpose-built system such as a Shahed 136.

Maritime organisations should conduct a thorough aerial drone threat and vulnerability assessment to understand which drone threats are relevant for their operations, particularly factoring in geographies of activity, cargo and vessel type and any geopolitical considerations.

General principles on how to assess the threats from and vulnerability to aerial drones can be found in NPSA guidance Countering Threats from Uncrewed Aerial Systems - Assessing the Threat and Vulnerability.

Such a threat assessment is a critical first step to developing a proportionate and effective response.

Some examples of drone-related threats relevant to commercial maritime vessels are detailed below.

Explosive delivery

Drones can be used to carry an explosive munition, loiter around a target and attack a vessel, leading to damage, disruption, and injury. This threat may be conducted by loitering munition drones, for example, Shahed 131 or 136 drones that have previously damaged vessels in the Strait of Hormuz. Further information on loitering munition threats can be found in the OCIMF document Loitering Munitions – The Threat to Merchant Ships.

Potential consequences of this threat include:

• vessels are disrupted or damaged and crew may be injured or killed
• repairs to the vessel are required, leading to increased costs and time in dock away from operations
• environmental impact of cargo spillage
• a risk of fire or a secondary explosion of the cargo, if a vessel such as an oil tanker is carrying hazardous materials

The results of specific studies exploring the vulnerabilities of ships to explosive threats can be found in the OCIMF documents:

• Ship Security – Hull Vulnerability Study
• Ship Security – Bridge Vulnerability Study

Reconnaissance

Drones can be used as a surveillance system to capture images of the vessel and its operations or to intercept communications signals using specialist equipment – for example, recording crew conversations to inform plans for piracy. There is also potential for ‘perch and stare’ activity where a drone lands on the vessel and provides extended undetected surveillance or intercepts cyber signals from the vessel.

Potential consequences of this threat include:

• images of the vessel, its crew and onboard activities are captured and transmitted to the drone operators
• cyber signals are intercepted and transmitted to drone operators for malicious use
• vulnerability to malicious activity including piracy is increased
• images or intelligence gathered may be used for purposes including propaganda, invasion of privacy or corporate espionage

Protest by a special interest group

Drones can be used to cause disruption to ship activity as part of a protest, for example, recording footage of protestor activities such as spraying paint on a vessel, broadcasting propaganda and communicating political statements.

This threat is more likely to be conducted by small commercial multi-rotor drones near shore and ports due to their availability, relatively inexpensive cost and ability to hover over the vessel.

Potential consequences of this threat include:

• ship is disrupted and delayed in sailing from the port
• reputational damage for shipping organisation and the port due to the potential impact on operations and possible negative media attention

Hazardous chemical or biological materials delivery

Drones can potentially be used to hover and deploy hazardous materials onto the crew and vessel, for example, spraying chemicals to damage cargo on a ship. This threat is more likely to be conducted by multi-rotor drones due to their hovering capabilities for more accurate material spraying. Crop spraying drones designed for agricultural use, such as to deploy fertiliser and pesticides, could be repurposed for such an attack.

Potential consequences of this threat include:

• vessels are disrupted or damaged and crew may be injured or killed
• vessel requires repairs or decontamination leading to increased costs and time in dock away from operations
• contamination of cargos such as grain

Vessel sabotage and disruption

Drones could potentially be deployed to deliberately sabotage or cause disruption to vessel systems. For example, sabotage could be achieved by flying directly into vulnerable sections of the vessel to disrupt critical ship systems such as navigation or communication equipment. Additionally, a drone could cause disruption by being used to transport electronic systems capable of emitting a signal which interferes with systems on the maritime vessel, for example, to cause GPS jamming. A drone could also be used as part of a cyber-attack, such as ‘spoofing’ GPS location signals to causing navigation errors, transmitting a false AIS signal mimicking the presence of another vessel or enabling a cyber ransomware attack.

Potential consequences of these threats include:

• vessels could be disrupted or damaged and crew may be injured or killed
• vessel requires repairs leading to increased costs and time in dock
• ship navigation system and crew situational awareness of other vessels in surrounding waters is compromised, leading to dangerous sailing conditions or navigational errors related to territorial waters or hazards such as sandbanks

Unauthorised and negligent drone use

The crew or passengers may use a drone onboard without permission, for example for taking images of the ship in a picturesque location. This threat is most likely on vessels such as cruise liners by users of small commercial multi-rotor drones due to their availability, relatively inexpensive cost, and ease of operation.

Potential consequences of this threat include:

• disruption of onboard activities to safeguard against the risk of injury to crew or passengers
• injury to people or damage to property

Mitigating drone threats to maritime vessels

Countering aerial drones is a complex and complicated challenge in any domain, but especially so in maritime environments. Maritime organisations should consider the following good practice activities when designing and implementing their solution.

Conducting a drone threat and vulnerability assessment

Initially, organisations should consider conducting a thorough assessment to identify which drone threats and vulnerabilities exist for their maritime assets. Organisations should consider which factors are most likely to influence drone threats, such as:

• the geography of their operation – for example, any shipping routes where drone threats are more likely or have previously occurred
• the vessel’s cargo
• national waters used
• vessel type
• wider international politics at the time of sailing

In time, this drone threat and vulnerability assessment should form part of the organisation’s ‘business as usual’ risk assessments for their maritime operations. Any risk assessment must be kept under regular review.

NPSA guidance on how to assess aerial drone threats can be found in Assessing the Threat and Vulnerability of Uncrewed Aerial Systems. Although the guidance is designed for fixed site protection, the general principles can be applied to maritime protection.

Key outcomes of the assessment should include that:

• potential threat actors are identified
• the priority threats are identified (for example, explosives attack, piracy, passenger safety) and the potential consequences of such an incident are understood
• the key vulnerable areas are identified, such as the bridge, hazardous cargo, crew locations
• any existing mitigations that may reduce the vulnerability are recorded, such as the presence of a ‘citadel’ or other secure areas
• any specific drone types of concern have been identified – for example, small commercial, loitering munition, military platform
• the geographic location of high-risk areas of relevance are identified
• the number of vessels at risk and their frequency and duration of operation in high-risk areas is understood
• the information gathered in carrying out the threat and vulnerability assessment may have additional utility, such as informing negotiations for insurance cover

Defining drone mitigation operational requirements

Multiple options exist to mitigate drone threats, the most common of which are detailed in the following sections. 

Those operational requirements may lead to the consideration of physical mitigation options, including vessel targeting hardening or the use of armed guards.

Vessel target hardening

To add protection to a vessel and crew under threat from an aerial drone, maritime organisations could consider the use of vessel target hardening as a mitigation option – by reinforcing or protecting critical vessel components and vulnerable areas to limit and control the potential damage a threat drone could cause.

This could allow a vessel to simply ‘wear the threat’, which means rather than directly trying to engage a threat drone to stop its flight, vessel target hardening provides sufficient protection so that if a drone attacks the ship, the crew will be kept safe and the ship operational.

Target hardening a vessel should be directed by the drone threat and vulnerability assessment to identify the most likely drone threats and critical areas of a vessel susceptible to a drone attack. Organisations should then consider developing target hardening requirements and identify appropriate target hardening options against a defined criteria set and installing the chosen protection to required areas of the vessel. For example, applying netting and ballistic protection around vulnerable cargo, vessel systems and components, as well as creating hardened and protected crew safe shelter areas onboard with sufficient emergency response equipment.

Further guidance on vessel hardening can be found in the OCIMF document Guidelines to Harden Vessels.

Using vessel hardening to mitigate aerial drone threats provides the vessel with the following.

• A degree of protection from drone attacks, to decrease risk to crew health, potential impact to ship operations and protect cargo.
• A degree of deterrence to weaponised drones, by visually demonstrating their threat can be nullified by implemented target hardening options.
• Once installed many vessel hardening options will provide 24/7 protection with no ongoing crew interaction.

Weaknesses of using vessel hardening to mitigate aerial drone threats include the following.

• Identifying areas of the vessel’s vulnerability to a drone attack is likely to be time-consuming and expensive.
• Sourcing and fitting protective systems to the vessel is also likely to be time consuming, expensive and their presence may impact day-to-day operational activities.
• Hardening materials may also require regular inspection, maintenance and lifecycle management, leading to additional, ongoing costs.
• Measures such as using ballistic glass may require structural reinforcement to install and their weight may reduce vessel fuel efficiency. This may significantly limit the number of areas that can be considered, for example limiting them to just protecting the bridge.
• Drone attacks may still occur and most physical hardening options will only protect selected highly vulnerable points, so this merely limits the probable consequences.
• The degree of protection needs to be proportionate to the anticipated threat to be effective – simple netting is unlikely to be effective against large loitering munitions.

Key considerations of using vessel hardening to mitigate aerial drone threats include the following.

• Use of safe areas (or citadels) is reliant on having an early warning of a drone threat to provide sufficient response time.
• Some hardening options may degrade with time and exposure to the elements.

Armed guards

Armed guards can also be used to mitigate aerial drone threats (where legal and in accordance with flag state regulations). This can include acting as spotters for aerial threat drones and using kinetic effectors such as guns fitted with specialised drone scopes to mitigate the threat.

Read more about kinetic effectors in the section of this guidance on counter drone effector technologies.

Guidance on the use of security on ships can be found in the OCIMF document Guidance for the Employment of Private Maritime Security Companies.

Using armed guards to mitigate aerial drone threats provides the following.

• Crew with suitably qualified experienced personnel to directly engage a threat drone flying near their ship.
• A ship lookout to provide early warning of a drone.
• A degree of deterrence by demonstrating the presence of a dedicated security force.

Weaknesses of using armed guards to mitigate drone threats include the following.

• Early warning of the threat drone and its location is required to allow the guards to respond effectively. It can be very challenging for a person to spot a drone, due to its size, speed and manoeuvrability, potentially providing very short response times.
• Even if the guard successfully shoots the drone, its momentum may still carry it into the vessel or any explosives may detonate in close proximity to the ship or crew.
• The use of a firearm on the vessel may itself present a significant safety risk to the vessel, crew and neighbours on land and sea.
• The legalities of using armed guards in commercial shipping and targeting a drone in the territorial waters being sailed needs to be considered.
• Flag state authority is required to carry armed guards and possession of weapons onboard may cause issues with local authorities in some areas.
• Having a dedicated armed security team may be very expensive.

Creating drone incident response management plans

Organisations should consider the development of aerial drone threat incident response plans, to formalise processes and activities they would conduct if an aerial drone threat event occurred. Examples of information that could be included within a drone incident response plan include:

• individual crew responsibilities should a threat drone be detected are laid out
• the process to alert the vessel crew is defined for example, via a dedicated drone alarm sound or specific tannoy announcements
• procedures for lockdown of the vessel are listed, for example, crew taking cover, emergency teams to standby
• processes for the implementation of response actions, including the use of counter drone systems if they are available, are defined
• contact details and processes for reporting of drone sighting to regional maritime authorities are readily available
• post event activities for stand-down or incident recovery are provided
• procedures for logging the event details and identification of any lessons learned to inform future updates to the response plans are available

Key benefits of creating a drone incident response management plan include:

• the crew are provided with a clear understanding of what to do during drone threat events and can respond in the safest and most effective manner
• response processes, activities and responsibilities are clearly defined

Conducting regular drone event training exercises and drills

Organisations should also consider conducting regular drone threat specific drills and training exercises to ensure their crew are prepared for an aerial drone event and can execute the relevant drone incident response management plan under pressure.

Key benefits of conducting regular drone event training exercising and drills include:

• the crew are prepared for a drone threat event and respond in the safest and most effective manner
• response processes, including the use of equipment and activities are rehearsed

Engagement with maritime security agencies – intelligence gathering and information sharing

A further option for maritime organisations to consider is to engage with local maritime law enforcement bodies, militaries, port security stakeholders and other shipping organisations that are operating within the regions of concern. This can support the timely provision of regional threat information, including details of any recent attacks or activities by hostile groups. Such information is invaluable in reviewing threat and vulnerability assessments and developing plans to minimise any risks.

This should include developing networks for you to share pertinent information with and developing links to groups who can help if there is an incident, such as the Coast Guard.

This concept could be expanded to include the formation of forums with other maritime organisations, for example, to provide alert networks whereby if a threat drone is sighted by a vessel crew this can be rapidly communicated to nearby shipping, potentially using digital selective calling (DSC) and very high frequency (VHF) marine radio. Such collaborations would also be of benefit in deconflicting legitimate and threat drones and in responding to any incident.

Considering drone awareness and deterrence campaigns

Drone awareness and deterrence campaigns can be used to discourage some aerial drone threats. For example, the use of visual tools such as signage, social media adverts and flyers as part of a drone awareness and deterrence campaign aimed at minimising unauthorised and negligent drone use around vessels, ports and cruise ships.

Drone deterrence campaigns are relatively low cost. They can:

• engage multiple stakeholders such as crew, passengers, port authorities, maintenance teams and service providers, thereby increasing counter drone collaboration between organisations
• encourage legitimate drone operators to inform vessels that they are flying in the area, reducing the level of nuisance alarms

Weaknesses of drone deterrence campaigns to mitigate drone threats include the following.

• Drone deterrence campaigns are only likely to reduce the threat of unauthorised and negligent drone use, with little to no impact on threats from hostile actors.

Key considerations of using drone deterrence campaigns to mitigate aerial drone threats include the following.

• This may be very effective against negligent drone use onboard, such as on cruise ships.
• Such campaigns may inspire the idea of using drones as an attack method.

Introduction to counter drone technologies

As drone technologies have become increasingly capable and available, their potential to deliver threats has led to the development of systems to identify aerial drone activity, monitor their behaviour and, if necessary, stop the threat. Such technologies are generally referred to as counter UAS systems (CUAS).

These systems were initially designed for state level operation to counter military grade threats but are now increasingly being marketed for civil applications, such as protecting the airspace around critical national infrastructure (CNI) assets including airports, power stations, ports and oil and gas platforms.

CUAS technologies are specialist systems designed to detect, track and identify potential threat drones to provide early warning of threats and apply a counter measure effect on the drone.

Definitions of CUAS functions

Detect

The ability to sense the presence of a drone. Alerts the user of a drone flying in the vicinity of the asset it is protecting, for example, a maritime vessel. 

Track

The ability to determine the drone position and movement over time, such as approaching the protected asset and, therefore, potentially posing a threat or moving tangentially. Allows the user to follow the drone’s movement and prepare a response. 

Identify

The ability to determine the size and type of drone. Allows the user to analyse the potential threat of the drone based on its characteristics. 

Effect

Using a technical effect to prevent the drone from completing its intended activity. Allows the user to influence the drone’s behaviour before it attacks the target, for example, forcing the drone to land or the pilot to lose control.

A wide range of technologies are available, which can be used individually or in combination to scale to the ascertained risk. CUAS systems are often best deployed as a suite of systems to counter the threat of aerial drones; there is no single ideal universal solution, or ‘silver bullet’. Operators may decide to only install part of the CUAS capability, for example, a basic detection capability to provide early warning and inform an onboard response without any active defence technology.

Before investing in such systems, it is best practice to first conduct an aerial drone threat and vulnerability assessment, understanding the most realistic level and type of threat, the likelihood of experiencing such threats and the probable consequences. This will help in defining operational requirements and mitigation options. General principles on how to assess the threat and vulnerability of aerial drones can be found in NPSA guidance Countering Threats from Uncrewed Aerial Systems – Assessing the Threat and Vulnerability.

To ensure any chosen CUAS Detect, Track, Identify, Effect (DTI-E) system fully meets the operational requirements, it is good practice to carry out rigorous in-situ testing, ahead of procurement, installation, integration and operation.

Counter drone technologies

Counter drone detect, track and identify technologies

A range of sensor technologies can be deployed to detect, track and identify a drone. Examples of common CUAS DTI technologies are provided below. Each technology offers strengths and weaknesses and consideration must be made for which technology(s) offer the most suitable capabilities to meet a maritime organisation’s operational requirements and mitigate the specific threat(s) to the vessel it will protect. Organisations should also apply the general considerations stated in the section of this guidance on selecting CUAS technology when assessing the following CUAS DTI technologies.

The following sections detail typical strengths and weaknesses of individual CUAS DTI sensor types. However, solutions have been developed where multiple CUAS DTI sensors are integrated into one overall CUAS system to provide a more comprehensive capability. Maritime organisations should be cognisant of the potential for using such an integrated sensor solution, noting they may require a compatible command and control (C2) system, to integrate and overlay different DTI sensor outputs onto one visual information system for a CUAS operator to monitor.

Passive radio frequency analysers

These DTI sensors detect radio frequency (RF) signals and analyse them to identify if they match stored drone RF signals used to communicate between the drone and pilot, typically by reference to a library of signals. Many systems use multiple sensors to triangulate the source of each signal to provide a tracking capability.

Some systems can intercept and read the control signals from a drone to gain further details of the operational parameters such as altitude, speed and direction. These are often referred to as a ‘cyber’ detection system.

Strengths of passive radio frequency analysers include the following.

• Can often identify multiple drones at any given time.
• Have relatively low hardware cost compared to some other CUAS DTI sensors.
• A passive sensor that listens for RF signals, rather than emitting them, reduces the need for any telecommunications licences to operate.
• Cyber systems can provide significant operational information about the detected drone.
• Some systems can also identify the location of the drone operator.

Weaknesses of passive radio frequency analysers include the following.

• The detection range is limited by the strength of RF radio signal being received, the size of the receiver and the background interference levels. For example, weak signals may not be detected in the presence of stronger RF sources.
• Tracking functionality is often limited, with some systems only giving the quadrant in which the source of the RF (drone and controller) has been detected. Other DTI sensors, including cyber systems, can provide clearer tracking such as plotting detections as a flight path onto a digital map for the user to monitor.
• Most RF detection systems rely on the equipment having suitable library references or decryption protocols for the threat drone in order to operate. If these are not in the library nothing will be detected.
• Drones not using wifi control frequencies, such as those controlled by 4G, 5G, satellite links or autonomous flight are also unlikely to be detected by many systems.
• False alarms due to RF interference or incorrectly analysing wifi signals from sources other than drones may be experienced.

Key considerations in relation to passive radio frequency analysers include the following.

• Cyber detection systems can be considered as signal interception and as such their use could in some areas be considered as breaching espionage laws - the consequences of being accused of espionage can be severe.
• The supplier’s ability to provide drone RF signature library updates to detect new or modified drone control protocols should be considered, including the cost implications for this such as subscriptions and software maintenance fees.

Radar sensors

Radar DTI sensors emit pulses of radio waves and then receive and process reflections of these radio waves to detect and determine a drone’s location. Some radar systems can further analyse these signals, using the micro-doppler effect, to distinguish between aerial objects such as birds from drones based on the radar reflections from rotors or propellers. A wide range of radar technologies can be used, from conventional scanning radar systems to 3D holographic radar panel technology, each of which has a variety of benefits and limitations.

Most drones have a small ‘radar cross section’ meaning their response will be too small to be seen by conventional maritime navigational radar systems.

Strengths of radar systems.

• Typically offer the greatest detection range and tracking capabilities of CUAS DTI sensors.
• Detect a wide range of drones regardless of their communication signals (for example, wifi, 4G, 5G, satellite).
• Can detect and track multiple drones simultaneously.
• Can operate day and night, including at times of low visibility for example due to fog.
• Many radar systems can also determine the altitude of a target drone.

Weaknesses of radar systems include the following.

• Radar systems may give false alarms by mistaking objects such as birds or rotating fans (such as those installed for air management systems) for drones.
• The size and construction of the threat drone will impact the effective range and probability of detection by radar systems.
• CUAS radar systems have the potential to cause interference with other radars such as the ship’s marine radar, other vessel’s radars or port radars and may require to be licensed to operate on specific frequencies.
• Interference from cross chatter between radars may impact CUAS performance. On ship, in-situ testing is recommended to check for interference with other radars and to calibrate the CUAS radar for optimum performance.
• Most counter drone radar systems have been designed for land use and may not work optimally on a moving vessel at sea. Operation on a ship can be negatively impacted by pitch and yaw, wave impact, moving and changing horizons and reflection from waves and on shore vehicles and buildings.

Key considerations in relation to radar systems are as follows.

• There is a wide range of CUAS radar systems, some of which may have significant power requirements which could be challenging to provide on a commercial maritime vessel. 
• Radar systems need to be located where the superstructure of the vessel will not block line-of-sight otherwise performance will be limited due to shadowing effects. Port infrastructure and buildings can also be an obstruction when operating a radar close to shore. Consideration should be given to determining the optimal locations on the vessel to install the radar.
• Drone detection radars vary considerably in size and weight and larger systems could therefore have an impact on a vessel’s buoyancy, stability and fuel efficiency. Holographic radar panels can weigh over 350kg each, with four needed to provide 360° coverage.
• The size, power and operating frequencies of drone detection radar vary significantly, with some producing high energy outputs that can be hazardous to health at close range. A safety assessment should be undertaken for non-ionising radiation when considering any new radar installation.

Optical sensors

Optical DTI systems use a camera sensor like CCD cameras, image intensifiers and infra-red cameras to capture footage of a section of sky and process it to identify a drone against background items. Most commonly, other CUAS sensors cue a camera towards the location of a potential drone and the optical sensor can then be used for target identification and threat assessment, such as identifying if the drone is carrying a payload or is a known threat platform.

Camera systems capable of providing 360° images or scanning the sky to detect drones without other sensors are now entering the market. Some systems have artificial intelligence (AI) image analysis software capable of providing additional information such as identifying types of drone, others rely on operator assessment.

Strengths of optical DTI sensors.

• Can be used to inform a threat assessment of a drone. For example, to determine the size of the drone, any payload it is carrying and the type of payload.
• Support the identification of legitimate drones and other aircraft, minimising the risk of false alarms and unnecessary or inappropriate responses.
• Detect a wide range of drones regardless of their design or communication signals (for example, wifi, 4G, 5G).
• Images and videos of threat drones captured by optical sensors can be used for post event investigations and to inform future responses.

Weaknesses of optical DTI are as follows.

• Optical DTI sensor range varies relying on the camera lens magnification and resolution to identify small drone targets. They are typically best suited to short ranges, probably limited to 1 to 2km.
• Optical sensors using AI could mistake other objects such as sea birds and other legitimate aerial vehicles such as helicopters for a drone. However, the image will support operators in confirming the identity of the suspected threat.
• Some AI image analysis systems may require an up-to-date library of drone images and footage to be trained on, which will regularly need updating. Keeping the library up to date could be challenging if the CUAS sensor is regularly at sea. The supplier’s ability to provide such updates and the cost implications, such as subscriptions and software update requirements, should be considered.
• Camera systems need to be calibrated to provide the relative position of detected drones, which may be challenging on a moving vessel leading to accuracy challenges.
• Sea conditions and weather conditions such as sea mist or spray may obscure camera sensors, reducing visibility and therefore limiting performance due to obstruction in poor visibility conditions in the operating environment. Sea water may also result in corrosion or damage to lenses increasing maintenance costs and causing reliability issues.

Key considerations in relation to optical DTI sensors are as follows.

• Consideration of whether the vessel’s threat drones are likely to be seen by an optical sensor at the desired detection ranges.
• Camera systems need to be located where the superstructure of the vessel will not block line-of-sight to enable them to see the drones, otherwise performance will be limited. Consideration should be made to identify a suitable location on the vessel to install the optical sensor in a place which will provide ongoing clear line of sight for the area of sky it is monitoring.
• Thermal imaging infra-red cameras or image intensifier systems will be required to provide detection capability at night which are likely to have lower resolution that daylight systems. The performance of any system for day and night detection must therefore be considered.

Acoustic sensors

Acoustic DTI sensors detect a drone’s motor noise using microphones and processes these acoustic signals to determine if they match stored drone sound signatures.

Strengths of acoustic DTI sensors include the following.

• Acoustic DTI sensors can detect a wide range of drones and are not reliant on their control signal.
• The sensors are relatively small and low cost compared to some other technology such as radar, requiring little power or support infrastructure.
• Using multiple acoustic sensors may allow the rough direction to the drone to be assessed - this is unlikely to have great accuracy compared to some other technologies.

Weaknesses of acoustic DTI sensors include the following.

• Sensor range is limited by the sensitivity of microphones and how noisy the drone is, in addition to the system’s ability to detect the drone motor above other sources of noise such as wind noise and marine engines.
• Drone noise originating from long ranges may be challenging to detect, particularly in heavy seas or strong winds. As the noise from different drones varies considerably, consideration should be given to whether threat drone(s) of concern are likely to be detected by an acoustic sensor at the desired detection ranges.
• Access to military systems such as loitering munitions by the CUAS manufacturer may be challenging, reducing the availability or quality of their library noise signatures. The cost of software and library updates and the ability to update them whilst at sea should be considered.

Key considerations in relation to acoustic DTI sensors are as follows.

• Consideration should be made to identify a suitable location on the vessel to install and operate the acoustic sensor, in a place which has minimal background acoustics which could otherwise lead to false alarms or reduced performance.
• Acoustic sensors require an up-to-date library of drone motor noise signatures to detect drones. If a specific drone is of concern, operators should check that the library contains their specific signature.  

Counter drone effector technologies

A range of technologies can be deployed to counter a threat drone, which is often referred to as effectors. An overview of common CUAS effector technologies is provided below.

Each effector technology offers strengths and weaknesses, and consideration must be made for which technology(s) offer the most suitable capabilities to meet a maritime organisation’s operational requirements and mitigate the specific threat(s) to the vessel it will protect. Organisations should also apply the general considerations stated in the section of this guidance on selecting CUAS technology when assessing the suitability of the following CUAS Effector technologies.

CUAS effector technologies are often designed in a way where they are targeted towards the location of the threat drone by a CUAS DTI system. Maritime organisations should be cognisant of the opportunity to use such an integrated system of CUAS DTI-E sensors, noting they require command and control (C2) systems, interfaces and Graphical Information Systems (GIS) to operate. For example, an integrated CUAS DTI-E solution could provide a CUAS operator with a single integrated visual information screen to monitor threat drone detections, tracking and identification and provide an effect activation button or automatically activate the effect technology as required. 

Although many systems provide the option of automatic effector activation, this is not generally recommended. Due to the risk of collateral damage through inadvertent activation, it is generally recommended there should be a human operator who reviews the potential threat and approves any effector action.

Kinetic systems

Weapons including net guns and firearms can be used to deploy a ‘kinetic effect’ to engage a threat drone.

Kinetic effect: inflicting damage through physical impact, where damage is related to the velocity and mass of the projectile.

This could be using a net to capture or entangle the drone and force it to fall into the sea, or use of firearms to shoot the drone, damaging it sufficiently to cause it to crash.

Military grade weapons systems including missiles and radar guided automatic guns are outside the scope of this guidance as they would not normally be suitable for deployment on civil vessels.

Strengths of kinetic weapons include the following.

• Kinetic weapons provide crew with capability to directly engage a threat drone before it reaches its target and can complete its attack.
• Modified gun sights are available to increase the likelihood of being able to successfully shoot a drone down. Specialist weapons rounds such as shotgun cartridges have been developed which could potentially increase the success rate of disabling a drone with firearms.

Weaknesses of kinetic weapons include the following.

• It can be challenging to accurately hit a small, fast-moving target. This can be further complicated if firing from an unsteady platform such as a vessel in rough seas, or in poor visibility.
• The effective range of some kinetic effectors is quite short - for example, the distance a net can be propelled or the range of a shotgun round. An aerial drone may be able to fly at a distance beyond the effector range and still carry out threats such as surveillance.
• The available response time to successfully engage a drone may be very short if the drone is within its attack range, that is, the time for the effector system to be readied for use, cued towards the drone and accurately aimed before being fired. Multiple shots may be required to obtain the desired effect.
• Kinetic effectors may present a hazard to those onboard a ship or in the vicinity of their use.
• Drones engaged but not destroyed may still present a risk, potentially hitting the vessel or other ships or structures in the vicinity. In the case of loitering munitions, even if a kinetic effector damages the drone, the warhead may still detonate and present a hazard from the blast and shrapnel.
• Kinetic effectors may require regular maintenance or calibration.
• Kinetic weapons often require either an automated targeting system or suitably trained members of the crew to operate. This may be unfeasible to resource for commercial vessels.

Key considerations in relation to kinetic weapons are as follows.

• In some territories, especially conflict zones, the possession of firearms onboard may be seen as illegal resulting in severe consequences if the vessel is inspected.
• Where firearms are allowed, it is likely that there will be regulation as to their safe storage and the approval of anyone who will use or access them. This could include firearms licences and vetting procedures, with only authorised firearms users allowed to operate them.
• Any firearms should be safely stored in an appropriate gun safe, which may limit the speed of response to an incident.
• Net launchers may be considered as firearms in local regulations, making them subject to the same legislation as rifles and shotguns.
• The cost of consumables such as net projectiles should be considered, especially for use at sea where it is less likely that the systems will be recovered for reuse.

Jamming systems

Radio frequency jamming CUAS effectors transmit a signal which blocks the signal between the drone and its controller. This interruption of the control link can cause the drone to change behaviour, for example, hover and land or return to a ‘home’ location. Jamming of the video signals from the drone to interfere with the pilot’s ability to target or view activities onboard a vessel is also possible.

Some systems are also designed to jam GPS signals, preventing the drone’s ability to receive GPS location data, making them more difficult to fly and preventing many forms of autonomous flight.

Strengths of jamming systems are as follows.

• RF jammers provide the crew with the capability to disrupt the control and flight of a drone, limiting its threat by reducing its ability to target or observe the vessel.
• They can be effective at jamming a range of signals associated with the threat drone, such as wifi, 4G, 5G, satellite communication, video link and navigational control but only when the jammer can operate on the appropriate frequency.
• Jammer systems usually have a wide area of effect, so accurate targeting is not necessary.

Weaknesses of jamming systems are as follows.

• Control signal jammers will interfere with all signals on the frequencies they are broadcasting on, potentially causing collateral harm. This could include interference to systems operating on the vessel and any systems being used by others within the interference range. Technologies susceptible to interference include wireless controllers and keyboards, internet enabled devices, wireless security cameras and some medical devices.
• GPS jamming will interfere with the navigation of all vessels or aircraft in range, for example interfering with automated docking systems, or preventing accurate navigation in hazardous waters.
• The response to jamming will vary between drone systems and is unpredictable, depending on the make and model of the drone, whether it is a multicopper or fixed wing design and how it has been programmed. They may hover, try to return home, attempt to land at their current location or just fly out of control. Some drones may continue their original flight path using other navigation methods such as inertial guidance.

Key considerations in relation to jamming systems are as follows.

• Jammer systems are designed to transmit on specific frequencies, which need to match the electronic communication frequencies used by the drone. They will therefore be ineffective against drones operating on different frequencies to those being jammed or using alternative navigation systems, for example 2.4MHz wifi jamming system will not be effective against drones operated using telecommunication (4G/5G) networks, satellite communications, inertial navigation or autonomous flight. The control link frequencies and signal strengths used by drones can vary around the world depending on local regulations.
• The effective range of jammers will depend on the effectors’ power and antenna efficiency, relative to the power and distance of the signal being broadcast between the drone and pilot being jammed. This can vary from hundreds of meters to several kilometres.
• While some jammers are directional, interference in all directions should be anticipated.
• In some territories it may be illegal to simply be in possession of jamming systems, with GPS jammers being of particular concern in many parts of the world. Use of control link jammers by anyone other than those approved by national authorities may also be illegal in many countries, including the UK.
• The interference effect of jamming may cross into territories beyond those where the ship is located, thus introducing wider regulatory concerns. For example, use in international waters could interfere with systems in a nation’s territorial waters.
• Jammers should only be operated by suitably trained members of the crew.

Spoofing Systems

Spoofing CUAS systems transmit a control signal that mimics and replaces the drone operator’s control signals, allowing the CUAS operator to influence the drone’s behaviour. For example, it could cause the drone to fly to a desired safe location rather than the intended target. This is sometimes referred to as ‘cyber takeover’.

Another form of spoofing can involve producing false GPS signals, causing the drone (and any other GPS controlled systems) to believe it is in a location different from the true position. 

Strengths of spoofing systems.

• Spoofing systems provide the capability to influence and possibly control the behaviour of a drone flying near the ship, limiting its threat by reducing its ability to reach the intended target location.
• If the drone can be controlled and safely captured, it could be used as evidence for follow up investigations and prosecution.
• A control link spoofing system may be capable of impacting a single specific drone without any impact on other drones in the vicinity, even if they are of a similar design.

Weaknesses of spoofing systems.

• GPS spoofing systems, in particular, may cause interference and disruption to other vessel’s navigation systems operating in the area.
• Cyber control link spoofing will only work on systems where the specific drone protocols are fully understood and programmed into the CUAS system and where they can be broadcast on the correct frequencies. Any drone operating on other protocols or using incompatible frequencies will be unable to be influenced.
• Any drone software or firmware changes to the drone from those programmed into the spoofing system may require the CUAS system to be updated – the development of new control protocols may be a slow and expensive process.

Key considerations in relation to spoofing systems.

• The range of spoofers may depend on their power and antenna efficiency relative to that of the primary controller.
• Spoofing may be illegal in many regions.
• Spoofing involves cyber signal interception, which may be classified as espionage in some countries.
• When spoofing the control links of a drone, the CUAS operator in effect becomes the drone pilot and is therefore responsible for control of the drone and any resulting harm it may cause.

Hunter-killer drones

Hunter-killer drone systems deploy a defensive drone to intercept the threat drone and deploy an effect, to disable the threat drone before it reaches its target. Although these could be operated manually, several ‘drone in a box’ solutions are under development enabling the drone to be constantly on standby for rapid deployment.

Strengths of hunter-killer drones are as follows.

• A hunter-killer drone provides the capability to directly engage a threat drone with a defensive system at range and before it reaches its target.
• Interception can involve several different ‘effectors’ depending on the system used, potentially including firing nets, using onboard weapons, using onboard jammers, or in the most basic form using the interceptor drone as a kinetic weapon and flying it into the threat drone causing it to crash.
• Some hunter-killer drones are being developed with the capability to capture a suspected threat drone and return it to a safe location. However, it may not be desirable to bring a captured drone onboard if it is suspected that it may present a danger to the ship, for example, if an explosive device is being carried.
• Because the hunter-killer drone operates away from the vessel, the risk of damaging the vessel itself due to the onboard ‘effector’ is reduced.

Weaknesses of hunter-killer drones are as follows.

• A hunter-killer drone deployed at sea must be able to operate in challenging flying conditions and from an unsteady launch platform.
• To successfully intercept a threat drone may require an automated targeting system or suitably trained members of the ship’s crew to pilot the hunter-killer drone and deploy its defensive systems. This can be very challenging with fast moving threat drones and could be difficult to resource for a commercial vessel.
• A hunter-killer drone is likely to be large and could be hazardous for the crew to operate onboard, particularly during take-off and landing back on the ship.
• A hunter-killer drone may be expensive to procure, install and operate. If the drone is lost at sea during a mission, it will require investment to replace it. Ideally, reserve drones should be available for contingency purposes to avoid relying on a single system.

Key considerations in relation to hunter-killer drones are as follows.

• Any hunter-killer drone would need to be sufficiently capable to mitigate the anticipated size and type of threat drone to be effective.
• If the interceptor is too slow or too small, it may not have sufficient range, speed and endurance to be able to respond in time, or its effect may be insufficient to overcome the threat. The time available to intercept the threat will be reliant on the successful detection and identification of the threat drone using DTI systems.
• If more than one threat drone is present, it is likely multiple hunter killer drones would be required which may need to be controlled simultaneously.
• A hunter-killer drone may only be equipped with one defensive system and if this initial engagement misses the target drone, a secondary effector option may be needed.
• A hunter-killer drone is likely to require calibration of its flight control sensors and routine maintenance requiring a skilled technician, which could be unfeasible to resource for a commercial vessel.

Energy weapons

Energy weapons such as lasers or radio frequency directed energy weapon (RF-DEW) can be used to target and disrupt a drone, and cause it to fall into the sea. Energy weapons are designed to cause damage to the drone’s structure or control electronics but without reliance on any kinetic effects.

As set out in the key considerations section, it should be noted that energy weapons are currently considered to be military systems and are rarely considered for civilian use. They are unlikely to be relevant to commercial maritime operators at present but are covered here for completeness, as they are often highlighted in media reporting.

Strengths of energy weapons.

• Provide the capability to directly engage and possibly destroy a threat drone before it reaches its target and completes an attack.
• Can operate at a significant range.
• The operation of an energy weapon is not dependent on any specific characteristic of the threat drone, such as the control protocols.

Weaknesses of energy weapons are as follows.

• Firing a laser towards an aerial drone target may lead to unplanned collateral damage to other vessels and systems in the vicinity, potentially damaging any object in its path. High energy lasers can cause significant damage to softer targets than drones, such as living things, at significant ranges.
• RF-DEW systems which disrupt the drone’s electronics are particularly likely to cause ‘fratricide’ or collateral damage, negatively impacting the electrical systems on the maritime organisation’s vessel and any nearby electronic systems.
• Targeting any small fast-moving drone is challenging leading to accuracy and performance limitations. With lasers, it may be necessary to hold the beam on the drone for several seconds to have a critical effect. Any laser energy not being absorbed by the drone will continue in the same direction until it dissipates or finds an alternative target. RF-DEW systems tend to spread energy over a much wider area than lasers, making targeting easier but increasing the risk of collateral damage.
• Energy weapons typically have very high power requirements, potentially beyond that available on commercial maritime vessels.

Key considerations in relation to energy weapons.

• They are likely to be illegal in many countries for civilian commercial vessels to install and operate and are typically considered to be advanced military grade systems.  
• The cost and power requirements of such systems can be very high and are likely to be prohibitively expensive for a commercial maritime vessel.  
• The effective range of an energy weapon depends on the amount of power being used and the vulnerability of the target to damage.

Evaluating counter drone technology for use in the maritime domain 

It is important that any response is reasonable and proportional to the anticipated threat, considering the likelihood and probable consequences of any incident. This will be informed by carrying out a threat assessment. Different levels of response may be appropriate, scaling between options including: 

• tolerating the threat 
• adding it to the maritime organisation’s emergency response planning (this could include initiating training drills for crew response and monitoring any threat warning information channels) 
• initiating damage limitation controls, often referred to as ‘target hardening’ of the vessel 
• installation of CUAS DTI technology to provide early warning of a drone’s presence 
• installation of CUAS DTI-E capabilities to provide early warning and a means of attempting to stop any attack 

The risks and consequences of taking counter drone actions against all potential drone sightings should be considered. These can vary from disruption to business, developing a blasé attitude to any sighting even if it may be a real threat, or overreacting and taking countermeasures against legitimate drone operations. 

Deconfliction with legitimate drones 

Legitimate drone activity is already underway in the maritime domain and is becoming more prevalent. For example, to inspect hulls in docks, support search and rescue operations and monitor emissions levels in the Strait of Gibraltar. Any mitigation solutions should consider the capability to distinguish between legitimate drones and threat drones, to minimise false alarms and, if using CUAS effector systems, to reduce the risk of accidentally interfering with or damaging a legitimate drone. 

Ensuring the solution meets operational requirements 

Organisations should be proactive in developing their operational requirements for their drone mitigation solution and should ensure that any CUAS option they choose fully meets these requirements. Practical demonstration of CUAS system capabilities should be requested where practicable, or independent testing sought rather than relying on the manufacturer’s claimed performance assessments. 

Solution performance testing and maintenance at sea 

If considering installing CUAS systems, their practicality and performance levels at sea should be understood via thorough in-situ demonstration and testing. This could range from weather resistance to validation of CUAS capability to ensure they meet operational requirements. Organisations should also assess maintenance requirements, including support options in the event of system damage or malfunction at sea. 

Solution financial costs and cost-benefit analysis 

Numerous costs are likely to exist including, but not limited to, the cost of purchase, installation, ownership (maintenance, licencing and updates to software), insurance and operation (staffing, training). A detailed cost-benefit analysis of each option under consideration should be conducted to inform any business case. Leasing of CUAS systems may be considered as an alternative to purchase if the requirement is only short term or if there are concerns over the practicalities of using the system. 

Solution staffing and training requirements 

Suitably qualified and experienced operators are often needed to operate CUAS systems. Operator recruitment, training and salaries should be considered if procuring a system that requires dedicated resources. The use of effective command and control (C2) software to operate the CUAS system can minimise the user burden, for example providing the operator with audio visual alerts of drone detection. Training the crew on what actions to take if there is a suspected threat must also be planned. 

Legal implications of possessing, installing and operating solutions in multiple countries 

The legal implications of possessing, installing and operating drone mitigation solutions onboard a vessel may vary across international waters, international air space, at sea and close to land such as near ports, especially near military facilities. The maritime operator and crew are likely to be deemed liable for any breaches of local laws and ignorance of such laws is not usually considered as a defence. It is therefore advisable to seek legal advice in advance. 

Examples of legal concerns include: 

• carrying CUAS effectors, especially kinetic systems, onboard a commercial maritime vessel may cause it to be deemed a weaponised ship 
• operation of jamming and spoofing systems may not be legal in many locations 
• using a CUAS detection system to intercept and analyse electronic signals may be considered as espionage in some areas 

The legal and financial implications associated with using a drone mitigation solution should be understood, including liabilities related to any collateral damage unintentionally caused directly or incidentally by using a CUAS effector system. 

Solution integration with existing vessel systems 

Counter drone solutions may cause interference with existing vessel technologies such as navigation and communication systems. Any technical solutions should have an integration testing and evaluation plan for in-situ testing onboard vessels to determine compatibility with other critical ship systems. Potential issues to assess before committing to installing any new systems include RF interference, power consumption and power supply, weight and any impact on vessel stability, suitable installation locations and integration with existing ship management systems and procedures (such as installing a CUAS system’s visual display interface into an existing security control room). 

Multi-mitigation solution option approach 

Depending on the vulnerabilities and threats identified, organisations may require multiple approaches to provide the desired level of protection. This could, for example, include having emergency response plans, protected muster areas and CUAS systems to provide an early warning. Use of several sensors for detection can provide greater assurance and understanding of any suspected threat, for example, integrating a radar for long range drone detection and cameras to assist the CUAS operator in assessing if the drone poses a threat. 

Mitigation action consequences 

Engaging a drone to mitigate a potential threat may lead to a number of consequences, some unintentional. For example, jamming a threat drone may cause it to change direction and hit someone else or it could inadvertently also interfere with a local maritime vessel’s navigation systems. Maritime organisations should therefore identify and assess possible consequences of deploying a drone mitigation solution during their response planning and determine specific scenarios where the solution’s use is overall beneficial, valid and proportionate for the consequences it may cause.

Selecting counter drone technology

Having carried out the threat assessment and requirements capture, organisations may wish to start considering the purchase or lease of CUAS systems.

Further guidance can be found in the NPSA publication Countering The Threats From Uncrewed Aerial Systems – A Guide To Selecting CUAS Technology.

It is recommended that a checklist be created based on the issues below and the requirements captured and that responses to these are discussed with any potential CUAS suppliers before any decisions are made.

Performance specification

• What specific drone types and models can be detected by the CUAS DTI system and does this include the anticipated drone types and threats?

• What is the required detection range for the anticipated threat and how much response time would this provide? For example, if a drone is capable of speeds of 60km/h and can be detected by the CUAS at a range of 2km, this potentially only provides a 2-minute warning.

• Can the vendor provide evidence of their capability against the threat platforms the maritime organisation has identified as of concern and at what operational ranges?

• Has any independent testing and evaluation process been carried out to validate this?

• What is the deployment time for any effector system relative to the warning time?

• What is the operational range of any effector system?

• How many drones can be tracked or affected at any one time?

• What is the false alarm rate (FAR) of any detection system?

• Are there known performance limitations of the systems, how do they impact the operational requirements and what can be done to minimise them? For example, an optical camera may perform poorly at night and should be supplemented by the use of a thermal camera.

• How does it discriminate between drones, aircraft and other objects such as birds?

• Can the CUAS technology differentiate between a legitimate drone and a hostile system?

Performance at sea

• How has the CUAS been proven in a maritime domain, and are the test conditions appropriate to your anticipated shipping areas? For example, operating temperatures, sea conditions, the pitch and roll of the ship, movement relative to the shore and weather can all impact performance.

• What design features are present and what testing has been done to ensure it remains operable at sea? This could include waterproofing, gimbal stabilisation systems etc.

• Has it been tailored for at-sea deployment, operation, and maintenance? How does this differ from any land-based variant?

Safety

• Are there any safety considerations the user should be aware of and if so, how should compliance be ensured? An example could be hazards from electromagnetic fields where a minimum safe distance may be mandated.

• What accreditation and evaluation has taken place, such as CE marking?

• Are there any risks with explosive or flammable cargo? Is the CUAS system intrinsically safe?

• What safety procedures are required to safely operate the CUAS?

• When assessing the suitability of any CUAS system for installation, safety is a critical consideration. For example, if operating on a vessel carrying hazardous cargo such as fuels the electrical safety and potential ignition sources will need consideration. If installing radar systems, the risks of non-ionising radiation should be assessed.

Integration into the ship

• How does the system meet the maritime organisation’s operational requirements (including size, weight, power requirements and mounting options for the vessels)?

• What are the power requirements for the equipment? Where would it draw this power from when installed on the vessel and what redundancy is needed?

• What are the procedures to install and uninstall the systems? For example, space, power, configuration, sensor calibration, ship location, use of a crane and mounting brackets.

• If more than one technology is to be installed, the interoperability of the systems (such as integration of a single control software system for radar and camera systems) should be addressed.

• Have any concerns regarding the legality of use been addressed within the CUAS selection process?

• What assessments have taken place to ensure the CUAS does not interfere with other onboard systems, other vessels or port technologies within the vicinity?

• Can the supplier provide technical and practical support to operational testing to ensure compatibility with the ship and other maritime systems?

• How must the CUAS integrate with existing on-board systems and processes? For example, integrating with other user interfaces, such as an AIS display.

• How do the power and data connections need to be configured?

• Does the CUAS system need to be installed in a position to provide a clear line of sight to detect or affect any drones and minimise performance limitations due to line-of-sight obstruction?

• Some CUAS systems can be very large and heavy, so the load-bearing capacity of any installation needs to be assessed.

Ongoing support

• How will the CUAS be future proofed against new and changing drone threats?

• What regular or future software updates, hardware replacement and servicing are required?

• Can the supplier detail the expected cadence of these services and updates, their response time and the availability of technicians to complete any CUAS maintenance at sea or in the dock?

• Maintenance requirements, including the availability of spares suitably qualified support staff and the ability to carry out maintenance in the vessel’s region of operation, should be fully understood.

• What aspects of the system are user serviceable? What spares and training are needed to support this?

Operational Requirements

• Which C2 systems are required to operate the CUAS?

• What are the training and workforce requirements to operate the system?

• How can any concerns regarding the legality of use be addressed?

• Given the potential quality of a selected C2 system, how will it impact staffing and training requirements?

Cost of system

• What is the CUAS’s total cost of installation, including purchase or lease, installation, power and network connection, integration with other systems and tailored to any specific needs?

• If leasing some or all of the system, any additional costs or liabilities should be understood including loss, wear and tear, or damage to equipment, additional charges per deployment (for example, for each deployment of a hunter killer drone) and end of contract removal costs.

• What is the CUAS’s total cost of ownership? This may include maintenance support, library updates, if appropriate, spares and consumable costs if any, and software support.

• What are the staffing requirements to operate the system, including any associated training costs?

• What is the anticipated operational life expectancy and end-of-life strategy for the system, including the cost and environmental impact of decommissioning?

Further guidance

Further guidance related to countering the threat of aerial drones to maritime vessels can be found in the following documentation.

UK counter-unmanned aircraft strategy - sets out the UK government’s strategy to mitigate the malicious, criminal use of drones, including threats to the UK’s national security and critical national infrastructure.

Countering threats from unmanned aerial systems (NPSA) - guidance on assessing and mitigating the security risks posed by uncrewed aerial systems.

A guide to selecting CUAS technology (NPSA) (PDF) - guidance on steps that critical national infrastructure sites should take to deliver C-UAS technology.

Assessing The Threat and Vulnerability of Uncrewed Aerial Systems (NPSA) (PDF) - how to assess the vulnerability of a site to the threat of uncrewed aerial systems.

Developing operational requirements for C-UAS detect, track and identify technology (NPSA) (PDF) - guidance on steps critical national infrastructure sites should take to develop operational requirements for C-UAS technology.

Loitering munitions – The Threat to Merchant Ships (OCIMF) - information paper which covers the threat posed by loitering munitions (LM) such as the Shahed-136, which has been used against commercial vessels, operational characteristics and trends related to the employment of these systems and the technical characteristics of LM and considerations, including guidance for best practices.

Guidelines to Harden Vessels (OCIMF) - guidelines on relevant topics such as use of armed security, safe muster points (citadels), chain link fences to mitigate explosives.

Guidance for the Employment of Private Maritime Security Companies (OCIMF) - guidance intended to help owners/operators with pre-selection considerations before entering into any agreement with a private maritime security company#.

Ship Security – Hull Vulnerability Study (OCIMF) - computer-based simulation study to assess the vulnerability of a tanker to a range of threats.

Ship Security - Bridge Vulnerability Study (OCIMF) – study on maritime vessel’s bridge’s vulnerability to firearms and blast.

Protection against Unmanned Aircraft Systems: Handbook on UAS protection of Critical Infrastructure and Public Space – a 5 Phase approach for C-UAS stakeholders.

Protection against Unmanned Aircraft Systems – handbook on UAS risk assessment and principles for physical hardening of buildings and sites.

Drone Drills - How to Prepare for a Drone Incident (JAPCC) – emergency procedures for swift and efficient crisis management across military, civil and public sectors.

A Comprehensive Approach to Countering Unmanned Aircraft Systems (JAPCC) – a technical manual covering all aspects of having to counter the full spectrum of unmanned aircraft and their respective system components.

Terms of use

While the advice given in this guidance has been developed using the best information currently available, it is intended purely as guidance to be used at the user’s own risk. This guidance should not be seen as endorsing any specific drone, counter drone or other security technology or manufacturer.

All drones, counter drone systems, vessels or other items referenced in this guidance are for illustrative purposes only and no inference as to their threat or capability should be drawn.