Across the globe, increasing threats of terrorist attack against national targets, infrastructure and population, have security agencies on high alert. Incidents of explosive smuggling, including losses of radiological materials, are reported to be on the rise. Post-conflict unexploded ordnance contamination also remains a serious problem, globally. These factors, in turn, are driving urgency within defence industry and scientific circles, to research, innovate and develop powerful tools, techniques and technologies able to detect explosives of all kinds in a wide range of scenarios.
Explosive detection, commonly used in border control scenarios and at airports and maritime ports, is the catch-all term for various non-destructive methods of inspection using a range of equipment, techniques, and procedures to determine the presence of explosives or explosive residue in, or on, a container, surface, clothing, or other suspect item. Explosive detection is also used in military contexts; in the previous issue of ESD, for example, we looked at some of the unmanned de-mining systems currently in development, or employed, to help rid the world of hidden landmines through typically ‘destructive’ techniques. However, it is the initial detection of such ordnance, using various ingenious means and scientific methodologies that’s relevant here. This article, therefore, not only touches on some science incorporated into detection products and methods, but also the market for explosive detection equipment, industry players and some of their solutions on offer; it also looks at certain de-mining innovations, including a fascinating, NATO-sponsored research project that has the de-mining community ‘buzzing’.
Detection Methods and Science
For the major groups of explosives – the nitroaromatic explosives, nitrate ester, and nitramine explosives, as well as explosives based on inorganic nitrates – the use of colourimetric testing is a well-established and widely-used method to detect explosives. This relies on colour-changing, fluorescent sensors that can detect and identify multiple explosive types within 10 seconds or less, differentiating between such explosive compounds as: TNT, Tetryl, PA, TNT, DDNP, DMNB, HMX, RDX, and PETN.
This kind of testing involves applying a chemical reagent to a suspect item and observing for known, common colour reactions that indicate if an explosive material, and typically what type, is present. However, this approach relies on the presence of nitrogen to achieve positive results, whereas in cases where explosives do not contain nitrogen and are, for example, chlorate or peroxide based, such as TATP (Acetone Peroxide), colourimetric detection is not as effective, if at all.
Spectrometry of various kinds, e.g. Ion mobility spectrometry (IMS), similar to mass spectrometry (MS), is also widely used to identify target molecules in a range of lab, back-room, and operational applications forming the basis of several product solutions deployed in places like airports. Gas chromatography (GC) is sometimes used to separate molecules prior to MS, and can offer another layer of information about a particular molecule aiding in its identification. Explosives can also be detected using computed axial tomography (CT) x-ray scanning, which can determine the density of a material, unless obscured within some form of casing or other electronic equipment, and match it to a threat library; such CT systems are used in scanning machines at events, airports, and other locations. Whilst other complex scientific methodologies can be employed to detect for explosives, space prohibits any worthwhile discussion of these in this article. With a similar reference to space, the use of taggants to mark explosives at manufacturing stage is worth a brief mention; taggants are used to make detection and identification by animals and equipment easier, and to enable agencies to trace an explosive back to the maker and, potentially, to the buyer. That said, the evolution of explosive taggants is very involved; some taggants tried have had adverse effects on an explosive’s performance in legitimate operational scenarios, while others have not withstood the forces of detonation well enough to be worthwhile. One latest method of explosive marking is the Nuclear Barcode, which tags explosives by adding low concentrations of eight different elements to the explosive, and then reads the tag from the post-blast residue using neutron activation analysis to identify the elements and their concentrations.
The Market for Explosive Detection Solutions
The global explosive detection equipment market has been monitored and analysed by the Technavio research group since 2017 and its recently released report “Global Explosive Detection Equipment Market 2019-2023” suggests that the sector is poised to grow by some US$3.1Bn during this 4-year period. This growth, apparently, is driven by “the enhanced security mandate of authorities”, which, in the face of recent terrorist attacks in Europe, Asia, and worldwide, is unsurprising. In addition, the anticipated advent of wearable explosive detection equipment will, according to the research, further boost growth in the sector.
With the illicit movement of explosive materials, security agencies globally are not only being encouraged to enhance their security planning, but are also facing mandates to deploy preventative measures such anti-explosive detectors and scanners across a range of critical infrastructure sectors, including, but not exclusively: aviation, offshore oil and gas, transportation, the air cargo supply chain, and maritime sectors.
But with an even wider range of global applications, from border security, public safety, and defence, to airports, transportation and logistics security, all demanding reliable explosive and explosive trace detection, the development of devices, such as hand-held detectors, ground-mounted, and vehicle-mounted screeners is increasing.
Let’s take a look at some of these from some a handful of leading explosive detection specialists.
Makers of Explosives Detection Equipment
While a great many companies are involved in the explosive detection sector, contributing to the industry’s projected figures, only a handful can be mentioned here. As with most in the sector, they employ some of the science mentioned above in their products, as well as other methods and technologies.
Falling into the latter category with its battle-proven Husky Mounted Detection System (HMDS) is Chemring Sensors and Electronic Systems’ (CSES). HMDS, a product of CSES subsidiary, NIITEK, now integrates a Wire Detection (WD) Array with the HMDS’ Ground Penetrating Radar (GPR) with the combined effect that it can now, not only detect sub-surface IEDs, but also the command wires and wiring systems used to remotely detonate or trigger them. CSES’ GPR was specifically designed for detecting metallic and non-metallic mines, and its handheld system, Groundshark, uses GPR together with electromagnetic induction (EMI) to detect, locate, and visualise buried hazards and anomalies, with precise target centering providing real-time audio and video feedback. The product meets MIL-STD-810F/G requirements for ruggedised military equipment. GPR is also at the core of the company’s R-VISOR GPR (robotic VISOR) robot-mounted mine and IED detection system, combined with a sophisticated metal detector, giving the user the ability to mark and visualize buried IEDs, antipersonnel, and anti-tank landmines.
Another player in this sector and using GPR for IED detection is Cobham Antenna Systems, which markets both hand-held and vehicle-based modular and scalable systems that can be integrated onto a range of tactical robots and vehicle platforms. One of its solutions is the Vallon MINEHOUND VMR3 hand-held detector, a joint-development with Vallon GmbH in Germany. It combines Cobham’s 1GHz GPR with a Vallon metal detector (MD), a dual-sensor approach that provides advanced high-performance detection of metallic, minimum-metal and non-metallic threats, including mines and IEDs.
The system’s MD and GPR can operate simultaneously, or individually; when a threat is located, the MD audio provides accurate position information as well as an accurate indication of how big an object is. The GPR audio provides additional position and depth information and identifies the radar cross-section of the target. The system can differentiate between targets and false clutter caused by such things as bullet casings, shrapnel, and other non-explosive metallic objects. The MD function, however, is the prime search capability and offers a highly sensitive technology to locate even minimum-metal mines (such as the PMA3 and M14), with MD sensitivity set by the operator. The GPR is self-calibrating when in use and indicates it is operating correctly with an audio signal every 7.5 seconds. A dedicated state-of-the-art DSP processor provides all control and signal processing functions.
Another provider of handheld explosives detection equipment, as well as desktop solutions, is FLIR Systems. The company’s Fido X-Series (X2, X3, X4) of handheld explosives trace detectors (ETDs) combine sensitivity, speed, and ease of use for security teams in a variety of field scenarios, including preventative screening operations where fast, accurate results are needed. These solutions all rely on FLIR’s proprietary TrueTrace technology, which detects a broad range of threats at nanogramme to sub-nanogramme levels, including military, conventional, homemade, as well as liquid explosives using multiplexed luminescence technology; each TrueTrace sensing material is formulated to react to a specific class of explosives. The slightest change in luminosity is measured to determine the presence of invisible explosives residue and the speed with which the TrueTrace technology enables the Fido-X solutions to deliver results make them suited to mass transit, sporting arena and critical infrastructure checkpoint applications. Front-line operators using the systems collect surface residue from the surface of vehicles, laptops, bags, cell phones, belts, crates, boxes, letters, or other items using a sampling swipe, which is then inserted into whichever ETD is in use. Any particles are heated, vapourised, and are drawn into the detector to be swept across the TrueTrace detection materials; any change in response on each detection channel is measured and analysed by the detector to deliver either an all-clear response or threat alarm. TrueTrace can detect a number of emerging explosive formulations and has a quick, three-minute start-up time and a fast ten-second analysis phase. The company’s Fido X4 was actually launched at the end of last year, incorporating a new new five-channel TrueTrace sensor array that delivers expanded threat coverage.
The company is currently working on a hardware integration kit that will sync Fido X4 with the company’s Packbot unmanned ground vehicle, widely used for explosive ordnance and bomb disposal, later in 2020.
Complementing FLIR’s handheld portfolio are solutions like the company’s ‘GC-MS’ gas chromatography/mass spectrometry-based Griffin G510 portable solution, which adds further accuracy at the scene of a detection event; GC-MS technology can quickly confirm the identity of an explosive to deliver additional forensic-level intelligence.
Also supplying handheld detectors is L3Harris, which has its H150E handheld explosives and narcotics trace detector in use with several end users. This handheld detector can rapidly detect and identify trace amounts of a wide variety of explosives and narcotics using a ‘real-time’ detection algorithm for fast results, alerting the operator as soon as it detects a threat. Like systems mentioned earlier, it has a rapid clear-down cycle and other features that minimise system contamination, ensuring the detector is ready for the next sample within seconds, even after a positive detection. A positive threat result is indicated by both visible and/or audible alarms, with the substance identification clearly displayed. Spectrograms, administrative functions, and diagnostics can be accessed and viewed on the integrated 4.3-inch colour touchscreen.
Detecting Explosives at Airports
No article on explosives detection would be complete if it did not, at some point, refer to the detection systems we all encounter on a daily basis traveling through airports or entering large convention centres and the like. Two players – amongst many – active here are L3Harris and Smiths Detection.
Meeting what it says are current and emerging regulatory requirements, the checked baggage security screening solutions in the L3Harris explosives detections portfolio are many. Differentiated by the speed with which they can perform their scanning functions, (which translates to numbers of bags that can be analysed per hour), systems include the widely deployed eXaminer 3DX, the enhanced speed eXaminer 3DX-ES, the high-speed eXaminer XLB and the ultra-high-speed, dual-energy MV3D. All these scanners link into L3Harris’ OptiNet networking infrastructure, which connects them to viewing stations and search workstations typically seen as we all pass through airport security.
Taking the XLB as an example, the system can scan 1,200 bags per hour (bph) and like the other scanners mentioned, uses dual-energy CT technology / 3-D Continuous Flow CT; operators will view high-resolution, 3-D images of alarmed bags in their entirety, or individual threat objects from any angle to help resolve alarms quickly.
The MV3D can scan even faster at 1,800 bph and uses a series of fixed X-ray sources and multiple detector arrays to create high resolution 2D and 3D images of target objects. This design provides the end user with the operational benefits of a traditional automated checked baggage screening system and the detection performance previously available only from rotational-gantry CT systems.
Smiths Detection’s HI-SCAN 10080 XCT is another dual-energy scanner that can handle 1,800 bph; it has performance capabilities based on Smiths Detections’ dual-energy x-ray line scanner with a proprietary single energy volumetric CT scanner providing full 3D, high-resolution imaging and reconstruction. The system is currently being trialled at Sydney Airport in Australia to screen carry-on and hold baggage. This follows successful explosives detection trials that ended late last year of another of Smiths’ solutions at the airport, the CT-based HI-SCAN 6040 CTiX used to screen carry-on bags.
Detecting Explosives with Animals
Perhaps the most widely recognised animals used to detect explosives are dogs. With noses that possess up to 300 million olfactory receptors, compared to about six million in humans, dogs can, when alert and not tired, be extremely sensitive to different target materials. Once a sniffer dog becomes fatigued, boredom can set in and its effectiveness in detecting explosives diminishes. That said, in addition to having a huge number of olfactory receptors, the part of a dog’s brain devoted to analysing smells is, proportionally speaking, some 40 times greater than the corresponding area in a human brain. Working with specially trained handlers, sniffer dogs will generally give a trained, passive response when they recognize an explosive scent, understood by the handler, but not bystanders.
In mid-2018, such sniffer dogs, capable of detecting minute traces of explosives concealed in air freight, were deployed in cargo sheds at British airports to reinforce the UK’s aviation security. Designated free running explosive detection dogs (FREDDs), though working in close partnership with their human handlers, the dogs are used to check large volumes of air cargo for a range of explosive materials, complementing existing screening methods. Each animal undergoes 12 months of rigorous training to achieve government certification before being deployed, though are subject to a regular quality assurance programme throughout their operational lifetime to ensure the animals’ detection capabilities are maintained.
While man’s best friend may have held the ‘lead’ position (excuse the four-legged pun) in the explosives sniffer-animal league tables for many years, it may soon be time to ‘roll over’ (sorry again) – in some scenarios, though not all – and make room for a six-legged, four-winged interloper.
For at least the last 20 years now, the ability of honeybees to ‘sniff’ out explosives has been known, and their potential to be trained to detect explosive materials has been the subject of research and study by a select number of leading scientists and institutes, including the world-renowned Rothampstead Research.
Results, however, have so far not been commercialised or deployed operationally, although that situation may be about to change in the not-too-distant future.
NATO Support for Bee Detectors
A NATO-financed project under the ‘NATO Science for Peace and Security Programme’ initiative has reached a point where it projects that explosive-detecting honeybees, trained to sniff out the trace explosives detectable in disused minefields across the globe, will be ready for operational deployment in the next five to 10 years.
The ’Bees4Exp’ project [Biological Method, Bees, for Explosive Detection] began in November 2017 and its current 3-year schedule is due to conclude in November 2020; the project is developing innovative methods and technologies to detect legacy landmines using trained bee colonies, employing three different techniques: training honeybees for explosive detection, using polymer films as explosive sensors, and imaging honeybees as they fly over and congregate in the region of unseen landmines. Project partners are the Croatian Mine Action Centre and its Centre for Testing, Development and Training, the University of Banja Luka’s Faculty of Electrical Engineering, the University of Zagreb’s Faculty of Transport and Traffic Sciences and the University of St Andrews’ Organic Semiconductor Centre.
With mines still present across Croatia, Bosnia and Herzegovina, as well as many countries through the world, the region’s academic institutes have been investigating de-mining for years; with their understanding of how expensive, time consuming and dangerous most current de-mining procedures are they want to come up with innovative solutions using biological methods of explosive detection to use alongside other proven, well-developed techniques. And what they now recommend is using trained bee colonies as efficient, standalone detection tools.
Two main methods, passive and active, are used with the trained honeybee colonies. Passive – this part of the NATO project is where the bees are allowed to fly freely around a suspect area, pollinating as they go. In the process they also pick up trace particles of explosives from leaking mines; TNT after time degrades to DNT, which releases the volatile molecules the bees pick up from grasses and meadow plants and flowers. When they return to their hives, the researchers have created ‘tunnels’ through which the bees must walk to reach the colony inside.
The walls of the tunnels are coated with luminescent organic semiconductor films/ Super yellow film and pick up the explosive particles, which can be analysed. The bees fly around the same area for ideally three days (one is too short and five too long) and once analysis of the tunnel samples is complete it can be seen clearly whether or not the area is contaminated by mines/IEDs.
Active – this part of the NATO project is being undertaken in Zagreb and involves the use of drones (not the male honeybee variety, of course!) to follow bees from the hives – bees which have been trained to associate the scent of explosives with sugar water, which results in them swarming, quite accurately, over and around a location on the ground where they think there is a source of nectar, when, in fact, they are actually hovering over unexploded ordnance/mines. Flying above the area, and equipped with high-definition and thermal cameras, three drones monitor the honeybee movements and produce a detailed overlay of targets on the ground.
The project is organized into seven work packages (WP) shared between the four partners: WP 1 Management; WP2 Honeybees training and management; WP3 Video acquisition system development; WP4 Bees distribution analysis; WP5 Chemical sensors for explosive detection; WP6 System integration; WP7 Dissemination and communication.
The NATO-funded Bees4Exp project hopes to integrate each key aspect of the project – detection, sensors, imaging – into a flexible, sensitive, and robust technological solution that can be effectively employed in the field. The project team views these new ‘tools’, tested in Croatia, Bosnia and Herzegovina, as low-cost technologies appropriate for use in many countries around the world. [The team consists of Professors Zdenka Babić and Nikola Kezić from the Faculty of Agriculture in Zagreb University, who pretty much started it all, along with drone expert, Mario Mustra, also from Zagreb. Bee expert, Janja Filipi, is from Zadar University and Zdenka Babic and Mitar Simic are from Banja Luka’s Faculty of Electronic Engineering. Scottish team members include Ross Gillanders and Graham Turnbull from St Andrews.]
ESD got in touch with Dr Ross Gillanders, Senior Research Fellow at the University of St Andrews’ School of Physics & Astronomy, who heads the university’s contribution to the project along with colleague Graham Turnbull. He said that by November this year it is hoped that the ‘techniques developed will be ready to start a validation process to move them towards commercialisation using blind tests’, with results thus far ‘looking very good’. At the same time, however, the team is trying to identify new funding sources for this follow-on work; Gillanders said that participants from industry are yet to get involved in this exciting work, though the team is confident interest will grow, and actively participates at events such as the Mine Action conference where exposure to industry participants presents mutual opportunities.
Of the test site at Benkovac, Gillanders said that some 1,000 mines and explosive ordnance – a mix of mainly Russian and Yugoslavian devices – are present over the 10,000-square-metre, simulated-minefield site. He said that the amount of explosive material returned to a hive by bees is something the team is trying to calculate as it can be an indication of the density of mines in a given area. He also indicated that they see honey bees as a complement to other explosive detection methods: “The aim is to give the de-miner another tool in the toolbox. For instance, bees are not an all-year-round solution, nor are they suited to all topographical scenarios; a seasonal April-September operational timeframe in areas with vegetation seems likely as their optimum performance period. And they also don’t like high winds.”
In terms of how the methodology would be commercialized, whether by creating ‘specialist trained bee colonies’ and how they would be used, Gillanders told ESD that, “I think training them, then leaving the colony in a community [where there is a local landmine problem], is likely, although everything else — optical sensing, drones, signal processing — would be delivered more as a service.”
Tim Guest is a freelance journalist, UK Correspondent for ESD and former officer in the UK Royal Artillery.