Green Paper: Lightweight Deployable Anti-Drone Perimeter Defense System: A Trophy APS-Inspired Approach

Abstract

Small first-person view (FPV) drones have emerged as a significant threat on modern battlefields, as seen prominently in the Ukraine conflict twz.com armyrecognition.com. These miniaturized unmanned systems can surveil, drop explosives, or act as kamikaze munitions with devastating effect, yet they are often too small and low-flying for traditional radar-based defenses to reliably detect crfs.com. This paper proposes a conceptual, lightweight, deployable anti-drone perimeter defense system inspired by the Trophy Active Protection System (APS). The envisioned system – designed for military forward operating bases and temporary camps, with secondary applications for law enforcement and civilian property protection – combines acoustic detection, laser/LIDAR ranging, and a scatter-shot kinetic interceptor in a modular turret configuration. Drawing on lessons from the battlefield and existing counter-drone innovations, the system would form an overlapping “dome” of protection when several units are networked around a perimeter. Each unit uses microphone arrays to hear incoming drones (notably the high-pitched whine of FPV quadcopters), pinpoints their approach, then employs LIDAR for precise range tracking as the drone nears. When a hostile drone enters the kill zone, a rapid-fire launcher discharges a birdshot-like spread of projectiles to neutralize the drone mid-air. The approach is analogous to Trophy APS on armored vehicles (which shoots down incoming rockets twz.com), but scaled to human-portable form and tailored for low, slow, small aerial targets. This paper details the system’s design rationale, components, and operation, with references to relevant field data (such as Ukraine’s successful acoustic sensor network defenseone.com and the emerging use of anti-drone shotguns asiatimes.com). Military use cases are emphasized – protecting troops from FPV drone attacks in conflict zones – while also discussing civilian scenarios like policing illegal drone incursions. We conclude that a Trophy-inspired hard-kill drone defense, while challenging, is both technologically feasible and urgently needed to counter the evolving drone threat.

Introduction

The rapid proliferation of small drones on the battlefield has created an acute need for short-range anti-drone defenses. In Ukraine’s ongoing conflict, small commercially-derived drones have become “an exceptionally useful” asset for both reconnaissance and attack armyupress.army.mil. Cheap quadcopters modified to drop grenades or serve as one-way FPV kamikaze drones are now inflicting heavy casualties and targeting even small units in the field asiatimes.com thefirearmblog.com. Some estimates suggest that drones account for up to three-quarters of battlefield casualties in Ukraine, far surpassing artillery and other traditional threats asiatimes.com. These drones can loiter quietly, then strike troops from above by dropping munitions or by diving in with explosive payloads. A typical FPV attack sees an operator piloting a fast quadcopter (often via video goggles) to hunt vehicles or trenches, or to drop a grenade directly onto a target. Because they are small, low-flying, and often made of plastic or carbon fiber, such drones have a tiny radar cross-section comparable to a bird’s – making them difficult for conventional military radars to detect or classify crfs.com robinradar.com. In high-clutter, low-altitude environments, traditional radar systems struggle with false alarms (e.g. confusing drones with birds) and limited line-of-sight coverage near ground clutter crfs.com. The result is that many small drones can penetrate existing base defenses undetected until it’s too late.

Current counter-drone measures at the squad or base level have limitations. Electronic jamming (“soft kill”) has been widely employed to disrupt drone control links, but this approach is growing less effective. Newer drones often use frequency-hopping radios or even fiber-optic tethers, making them resistant or immune to jamming asiatimes.com. Moreover, broad-spectrum jamming can interfere with friendly communications and drone systems, creating collateral effects on the battlefield asiatimes.com. Some advanced UAVs incorporate semi-autonomous guidance (machine vision or pre-programmed attack profiles) that allow them to complete missions even if their radio link is jammed asiatimes.com. Nets and physical barriers have seen some use (e.g. net launchers or wire barriers to ensnare drones), and while such methods can work at fixed sites asiatimes.comasiatimes.com, they are impractical for mobile forces and have a limited effective range. High-energy lasers are another countermeasure under development – capable of burning drone electronics or sensors – but field-deployable laser systems are still in early stages; they face challenges with power supply, atmospheric attenuation, and maintaining beam focus on fast-moving small targets asiatimes.com.

The military has found stop-gap solutions in kinetic means – essentially shooting down drones with guns. On the front lines in Ukraine, both Russian and Ukrainian soldiers have begun using shotguns as a last-resort defense against quadcopters asiatimes.com thefirearmblog.com. At close ranges (tens of meters), a shotgun blast offers a spread pattern that is more forgiving than a rifle bullet when aiming at a tiny, flying target. There are documented cases of soldiers successfully downing incoming FPV drones with shotguns – for example, a Russian soldier in Ukraine detected an approaching FPV drone with a radio scanner and shot it out of the sky before it could detonate armyupress.army.mil. This ad-hoc approach has proven effective enough that formal products are emerging: in 2024, Italian arms maker Benelli unveiled the M4 “Drone Guardian”, a 12-gauge semi-automatic shotgun optimized for counter-drone use asiatimes.com. It features a proprietary extended choke and barrel design to tighten shot groupings for longer reach, and comes paired with specialized ammunition loaded with hard tungsten pellets asiatimes.com. Each shell (using #6 shot of ~2.75 mm pellets) carries around 350 tungsten pellets totaling 34 g, providing a dense cloud of projectiles on each firing asiatimes.com. Tungsten’s hardness helps penetrate the tough frames of military-grade drones, which can resist softer lead pelletsasiatimes.com. Another innovation, the “Skynet” 12-gauge round, ejects a set of tethered fragments that entangle a drone’s propellers; if the round misses, it deploys a small parachute and falls safely to the ground asiatimes.com. These developments underscore the demand for effective hard-kill solutions against drones at close range.

At a larger scale, defense firms are adapting vehicle-mounted Active Protection Systems (APS) – originally designed to shoot down anti-tank missiles – to the drone threat. Israel’s Trophy APS, the inspiration for our proposed system, is a combat-proven system that uses radars and directed explosives to intercept incoming rockets and missiles in flight twz.com. Trophy has demonstrated over 90% interception success against anti-armor projectiles, protecting tanks like the Merkava and Abrams in combatarmyrecognition.com. However, the standard Trophy system (a several-ton vehicle-mounted unit) has limits in anti-drone defense. Notably, early versions of Trophy covered threats up to about 55° in elevation – adequate for horizontal missile threats, but insufficient against drones that can dive from directly overhead armyrecognition.com. Indeed, during the war in Ukraine, FPV drones armed with RPG warheads or grenades began exploiting top-down attack angles beyond Trophy’s original coverage armyrecognition.com. In response, Rafael (Trophy’s developer) announced in late 2024 a Trophy upgrade to handle top-attack drones, emphasizing how “increasing Trophy’s ability to engage threats from above could be valuable for swatting down hostile drones”, including agile FPV types twz.com. This confirmed the viability of using hard-kill active defenses against drones: if a tank can be protected by intercepting munitions mid-air, perhaps a field base can be shielded by intercepting drones in flight.

Problem Statement: Front-line units and temporary bases currently lack a lightweight, rapid-deploy system to detect and defeat small drones before they can deliver lethal effects. Human sentries with rifles or shotguns provide only a partial solution, as detection is a major challenge – the first warning might be the drone’s whir or a visual sighting, often seconds before impact. There is a clear need for an automated perimeter defense system that can continuously scan for small drones and neutralize them at a safe standoff distance. Such a system should be portable and quick to set up (for use at forward operating bases, command posts, or even dispersed infantry positions), and it should cover 360° and the full dome of the sky above a position. The system must rely on sensors effective against low-signature drones (beyond traditional radar), and must incorporate a fast-reacting effector (interceptor) with a high likelihood of hitting a small, fast-moving target. All of this should ideally be achieved with minimal operator workload and without imposing heavy logistical burdens (e.g. large power requirements or constant resupply of expensive interceptors).

Proposed Solution: Inspired by the Trophy APS concept, we propose a modular anti-drone perimeter defense system consisting of multiple small turret units that work in concert to form a protective “dome” around a site. Each unit combines (1) acoustic detection, (2) laser/LIDAR tracking, and (3) a scatter-shot kinetic launcher. The system is envisioned to operate largely autonomously: acoustic arrays would passively listen for the distinctive sound signatures of drone motors, cueing the system to a potential target long before it is visible. Then, an active LIDAR sensor would lock onto the drone to provide precise range and trajectory data, enabling fire control solutions. Finally, once the drone enters intercept range (e.g. within tens of meters of the perimeter), a small fragmentation charge or shotgun-like blast is fired to destroy or disable the drone. Multiple units (e.g. 3–4 or more) can be distributed around a base to cover all approaches, with overlapping fields of view and fire. The units would communicate to share detections and coordinate engagement so that the closest or most optimally positioned turret fires, while others hold fire or cover other sectors. In effect, this creates a lightweight “Counter-Drone Dome” – an active defense shield analogousto how Trophy APS creates a bubble of protection around a vehicle twz.com, but scaled for dismounted use and tailored to the unique threat profile of small drones.

 Example: https://youtu.be/fH_x3kpG8Z4?feature=shared

The remainder of this paper details the design and components of this proposed system, examines its operational concept, and discusses implementation considerations. We also highlight real-world data points and case studies – notably from the Ukraine war – that inform the system’s feasibility. While our focus is on military applications, we later discuss how such a system (or its components) could translate to law enforcement and civilian contexts, such as protecting public events or private property from intrusive drones. By synthesizing current technologies into a cohesive defense concept, this work aims to show that a deployable Trophy-inspired anti-drone system is both necessary and achievable given recent advances.

System Design and Architecture

Acoustic Detection Module

At the core of the system’s early warning capability is an acoustic detection module. Unlike radar or optical sensors, acoustic sensors excel at picking up the auditory signatures of drones even when visibility is poor or the drones are flying nap-of-the-earth. Small multi-rotor drones generate a characteristic buzzing or whining noise from their rotors and motors. These acoustic signatures can be detected at surprisingly long ranges given a quiet background and proper filtering – often on the order of hundreds of meters for larger quadcopters, though effective range decreases for very small or quiet models. In Ukraine, an entire national-scale system has proven the effectiveness of acoustic detection: as of 2024, Ukraine fielded a network of almost 10,000 acoustic sensor stations across the country to monitor for low-flying Russian drones defenseone.com. This distributed acoustic “Sky Fortress” system, built from simple microphones and smartphones on poles, can triangulate drone locations and cue air defense teams defenseone.com. In one test, when Russia launched 84 one-way attack drones in a mass salvo, the Ukrainian acoustic network helped shooters intercept all but four defenseone.com – a remarkable success rate that saved high-end missiles for larger threats defenseone.comdefenseone.com. The U.S. Army has taken note of this low-cost approach; American generals have lauded Ukraine’s acoustic network for “almost positively identifying drones in the distance” and urged integrating similar passive acoustic sensors into U.S. defense systems twz.comtwz.com.

For our proposed perimeter defense unit, the acoustic module would likely consist of an array of microphones arranged to perform direction-of-arrival (DOA) detection. By analyzing the time differences of the drone’s sound reaching each microphone, the system’s processor can infer the bearing (and elevation angle) of the incoming drone. Modern signal processing and machine learning techniques can further classify the acoustic signature, distinguishing drones from other noises like vehicles, small arms fire, or birds. Specialized algorithms (and training data from known drone acoustics) enable identification of the “fingerprint” of quadcopter noise mindfoundry.ai. The system could thus filter out false positives and raise an alert only when the sound matches drone acoustic profiles. Another advantage is passive operation: unlike radar or active scanning, simply listening does not give away the sensor’s presence or location, a tactical benefit.

In practice, each turret unit might have a small acoustic array mast that can fold out or extend when deployed. Upon detecting a valid drone acoustic signal, the unit’s control computer would calculate an initial approach vector for the target. This information is then passed to the turret aiming system and to any neighboring units via a network link. Because sound detection alone provides bearing but not precise range, the system would next activate its LIDAR tracker to lock onto the target and determine distance.

One challenge for acoustic detection is environmental noise and interference. Battlefields are noisy – gunfire, engines, wind, and other ambient sounds could mask or confuse drone sounds. However, advanced filtering and the high-frequency whine of small rotors (often in the ~100 Hz to several kHz range with distinctive harmonics) can mitigate this. Additionally, deploying multiple acoustic sensors around a perimeter allows triangulation of sound, improving accuracy and providing redundancy if one sensor is in a noisy spot. The turret units could form an acoustic mesh network, sharing raw or processed audio data to collectively determine a drone’s location. This cooperative sensing is analogous to how multiple microphones in Ukraine’s network pinpoint incoming drones for air defenders defenseone.com. Overall, acoustic detection provides the first line of awareness, cuing the system that “something is coming” often before the drone is directly overhead. It addresses the radar gap: even if the drone is radar-stealthy or flying below radar line-of-sight, it cannot hide its telltale buzz.

Laser/LIDAR Tracking and Ranging

Once the acoustic module has indicated an incoming drone and its approximate bearing, the next step is precise tracking and range measurement. Here we employ a Laser Detection and Ranging (LIDAR) system or similar time-of-flight laser rangefinder on the turret. LIDAR offers high-resolution targeting against small objects – it emits rapid pulses of laser light and measures the reflections to determine distance with centimeter-level precision. Compared to radar (with wavelengths of centimeters), a LIDAR’s light waves (typically near-infrared, e.g. 905 nm or 1550 nm) are orders of magnitude shorter in wavelength, enabling them to detect and map very small objects like mini-drones robinradar.comcrfs.com. Indeed, research has shown LIDAR can be effective in detecting and even imaging small drones at relevant ranges, albeit with some constraints. For example, a low-cost scanning LIDAR system called “LiSWARM” demonstrated the ability to detect and track individual drones within a swarm, using a scanning laser to spot objects only a few tens of centimeters in size crystal.uta.edu. In our context, the LIDAR would be used in a targeted mode: rather than continuously scanning the whole sky (which could be resource-intensive), it would be cued by the acoustic bearing to focus on a specific sector. Essentially, the system slews the turret toward the incoming sound and then fires a rapid sequence of laser pulses in that direction to find the range to the target.

Once the drone is “painted” by the LIDAR, the system gets real-time data on its distance, altitude, and relative speed. Many modern LIDAR units can also provide some reflectivity data or even a point cloud of the target, which can help confirm it is a drone (though small drones will only return a few points). With continuous or high-frequency pulsing, the LIDAR can track the drone’s trajectory inbound. This information feeds into the fire-control solution: the system will calculate the optimal moment and angle to fire the interceptor such that the spread of pellets or fragments will intersect the drone’s path.

LIDAR has advantages and trade-offs. On the plus side, it is highly precise and difficult for the drone to sense (some drones might detect the LIDAR’s laser, but unlike radar or sonar, there’s no broad emission that gives warning to an operator). It also functions independently of any radio emissions from the drone – useful against drones that may not emit much RF (e.g. pre-programmed or optical-guided drones). However, LIDAR performance can degrade in adverse weather: heavy fog, smoke, or dust in the air can scatter and absorb the laser pulses, reducing effective range. Rain or snow can create false returns or clutter. Therefore, in a complementary fashion, the acoustic system (which isn’t affected by darkness or light fog but can be affected by wind) and the LIDAR system (which isn’t affected by moderate noise but can be affected by optical obscurants) will back each other up. In clear conditions, the LIDAR might acquire a drone at, say, 200–300 m. In hazy conditions, the detection range might shorten, but by then the acoustic system would already have the drone tracked via sound until the drone is close enough for the laser to get a clear return.

An alternative or complement to LIDAR could be an infrared (IR) camera with thermal imaging, which can spot the heat of drone motors against the sky. However, IR provides angle-only tracking unless using stereo vision, and small electric drones have limited thermal signatures. Thus, the active ranging ability of LIDAR is a strong asset in this system. Some commercial counter-drone systems for fixed sites use micro-doppler radar to detect drone propeller movements robinradar.comrobinradar.com, but those radars tend to be larger and require careful tuning to avoid bird false alarms. Given our emphasis on portability and coverage of dead zones, LIDAR is a fitting choice for the short-range, high-precision tracking needed.

Kinetic Interceptor (Scatter-Shot Turret)

The final and most crucial element is the kinetic interception mechanism – effectively, the system’s “weapon” that will disable or destroy the drone. We propose a scatter-shot launcher mounted on each turret, drawing inspiration from Trophy APS’s use of fragmenting projectiles and from the battlefield use of shotguns against drones. The interceptor could take one of several forms, but the common theme is that it should fire a spread of small projectiles to maximize hit probability against a tiny aerial target. Possible implementations include:

• 12-gauge Shotgun-based Turret: A scaled-up version of the anti-drone shotguns like the Benelli M4 Drone Guardian, but mounted on a motorized turret. This could use actual shotgun shells (e.g. 3-inch 12-gauge shells) loaded with specialized drone-defense rounds. Each turret might have a revolving magazine or feeder holding several shells (for multiple engagements). When cued to fire, it would discharge a shell producing a cone of pellets. For example, using a tungsten #6 shot shell as described earlier would send ~350 dense pellets toward the target asiatimes.com. Even a portion of those impacting the drone’s rotors or electronics can bring it down. Shot spread and range can be tuned via the choke design; a tighter choke gives longer reach at the cost of a narrower spread. Benelli’s “Advanced Impact” choke claims to extend effective range beyond 50 m for drone targets thefirearmblog.com. A turret could likely handle even larger 10-gauge or 8-gauge rounds for more shot, though those are less common. The advantage of using COTS shotgun ammo is reliability and ease of resupply, but recoil management and reload speed would need to be addressed in the turret design.
• Fragmentation Munition Launcher: Another concept is a small grenade launcher or mortar-like device that fires a programmable air-burst round. Upon command, the round would explode at a calculated point near the drone, spraying it with a sphere of shrapnel. This mimics how Trophy APS interceptors work – Trophy’s launchers shoot a small explosive that creates a directed blast of fragments to “neutralize the threat, forming a precise matrix aimed at the area in front of the incoming projectile”armyrecognition.com twz.com. For anti-drone use, an airburst can be extremely effective: even a drone not directly hit by fragments may be knocked off course or have propellers damaged by the shock and shrapnel. Some existing C-UAS systems like the Oerlikon Skyshield use timed-fuse shells to create flak bursts against drones (Rheinmetall’s 35mm “AHEAD” rounds are an example, though that is a large system). Our system would require a much smaller analogue, perhaps a 40 mm grenade-size warhead with a pre-fragmented casing. The LIDAR’s precise range data would allow setting the burst distance accurately. A fragmentation approach increases one-shot kill probability but adds the complexity of an explosive munition (with safety and regulatory implications for law enforcement use).
• “Birdshot” Flak Rockets: A hybrid approach could involve miniature rockets or recoilless shells that on launch release a swarm of pellets or darts. For instance, a small rocket that flies out 30–50 m and then ruptures to disgorge a cloud of high-velocity pellets in the drone’s path. This would mitigate concerns of gun recoil on a small turret while still delivering shot. The Skynet round mentioned earlier is essentially a shotgun shell variant of this concept (using tethered nets)asiatimes.com. One could envision a scaled variant for longer reach.

For this paper, we will assume a shotgun-style kinetic interceptor for concreteness, as it aligns with known successful tactics armyupress.army.mil and available technology. Each turret’s weapon could be, for example, a double-barreled 12-gauge launcher, allowing two shots in quick succession before reloading. Using multiple shots provides a follow-up chance if the first salvo misses or only partially damages the drone. The system’s fire-control can assess if the target is neutralized (e.g., drone falls or signal is lost) and decide to use the second barrel if needed. The spread pattern can be designed to cover a certain solid angle. For instance, at 50 m distance, a choke producing a 1-meter diameter spread would be desirable to compensate for aim error and target movement, while still concentrating pellets enough to shred a drone. Smaller drones might require a denser pattern (hence smaller shot like #6), whereas larger quadcopters could be engaged with slightly bigger shot (#4 or even buckshot) for deeper penetration. Tungsten or steel shot is preferable to lead for hardness; tungsten in particular, though expensive, has the weight and strength to punch through drone motors or batteries asiatimes.com.

The kinetic nature of this defense raises an important question: is it safe to fire off scatter-shot rounds around a base? In a combat zone, the risk of stray pellets is often acceptable compared to the risk of a drone delivering a grenade. Still, our system can be configured to minimize collateral hazards. First, the engagement range is relatively short (likely under 100 m), so most pellets will lose lethal energy quickly after that distance. Small birdshot pellets decelerate fast and pose little danger beyond a certain radius. Second, the system can incorporate geofencing and angle limits – e.g., it will not fire directly inward toward the base, only outward or upward. The overlapping placement of turrets means each generally fires away from friendly positions. Third, if using an explosive fragmenting round, the fragmentation pattern can be designed to be mostly one-directional (much like Trophy’s interceptors are aimed outward from the vehicle). Backstops or radar-triggered cutoffs could prevent firing if the drone is so close that debris would rain on the defended site – though in practice, letting a drone that close would be a last resort anyway.

Reliability and speed are key: the system must detect, track, and shoot within a few seconds at most. FPV drones can travel over 100 km/h (≈30 m/s) in attack runs, and often come in low. If initial acoustic detection happens at, say, 150 m out, the drone might be 5 seconds away from reaching troops. Our design goal is to engage by around 50 m out or more, which gives perhaps a 3-second window for final engagement. Modern electro-mechanical turrets can slew and fire in well under a second once cued – similar to automated close-in weapon stations. The Trophy APS, for instance, reacts near-instantaneously to rocket threats at close range (milliseconds reaction time) armyrecognition.com. While our system won’t match that speed (due to using sound cues and possibly having more weight to move), it should respond fast enough given the distances.

To improve effectiveness, multiple turrets can even engage the same target sequentially: e.g., the first unit fires, and if the drone survives or dodges, a second unit from another angle can fire a fraction of a second later as the drone enters its sector. Networking and coordination logic (possibly using VHF/UHF radio or a wired link between units) will be essential to avoid wasteful duplication or crossfire. Only one turret should fire at a time at a given drone, unless a miss is detected.

Modular Deployment and “Dome” Coverage

The system is envisaged as modular – each turret is a self-contained unit (with its own sensors, weapon, power source, and processing), and multiple units can be combined to scale up the protected area. For a temporary base camp or forward outpost, we might deploy 3–4 units to cover a perimeter roughly circular or rectangular in shape (more units for larger perimeters). The units would be positioned at intervals, ideally elevated on tripods or building rooftops/towers if available, to maximize their line-of-sight. Once activated, the units would automatically form a wireless mesh network, sharing sensor data. This cooperative arrangement yields a 360° defensive dome: overlapping acoustic coverage and fields of fire that cover all azimuths and a full hemisphere overhead.

A three-unit configuration could be arranged in a triangle around a small camp, each covering 120° sectors with some overlap. Four units could be at the corners of a perimeter, each covering ~90°. Because each turret can rotate 360°, they are not fixed to one sector, but sector responsibility can be assigned to distribute the load and prevent all units from firing at the same target unnecessarily. In essence, the software would designate which unit has the best shot at an approaching drone based on direction and range, and that unit becomes the primary engager while others monitor. If the primary fails to neutralize the drone and it crosses into another unit’s quadrant, the secondary unit can take over. This layered engagement approach ensures multiple opportunities to stop the threat.

To achieve a dome-like coverage, the turrets must also handle targets coming from high angles. The turrets should have elevation freedom to shoot nearly straight up (90° elevation). A dome of perhaps 100–150 m radius around the base could be protected in this way, intercepting drones before they are directly overhead. Drones can of course dive from higher altitudes, so detection at altitude is important – acoustic detection often works better when the drone is low (since ground terrain can block sound if the drone is beyond line of hearing). But if a drone is directly diving from high above, a combination of acoustic (if it was heard on approach) and possibly one turret’s microphones pointing upward might catch it, or the LIDAR might even detect a descending object if scanning upward. One could also incorporate a short-range radar altimeter sensor pointing up to detect any object dropping from high altitude, as a backup.

Each unit being lightweight and deployable implies that a small team (2–3 soldiers) could carry and set up a turret within minutes. We imagine a system weight on the order of 10–20 kg per unit (excluding ammo), making it man-portable. Components could break down into a base with folding tripod legs, a sensor/weapon head, and an ammo magazine. Power could be supplied by rechargeable batteries or a small generator; acoustic sensors and fire-control computers are low-power, but the LIDAR and turret motors might draw more. Swappable batteries (common military rechargeable packs) could keep it running through missions. Given the importance of continuous operation, especially at night when drone attacks are frequent, a hybrid power with a quiet generator feeding a battery (so that there’s no downtime) might be used at bases.

In terms of mobility, the turrets could be mounted on small vehicles or even integrated onto armored fighting positions. For example, an infantry platoon in defensive posture could emplace two units covering their front and flanks. If they move, they can pack the units onto a pickup truck or armored carrier and redeploy at the next position. This is a stark contrast to big fixed anti-drone systems (like Israel’s Drone Dome C-UAS, which is typically vehicle-mounted and not foot-mobile).

The modular nature also adds redundancy: if one unit fails or is destroyed (e.g., shelled by the enemy), the others still function. They can also be spaced such that a single artillery shell or loitering munition strike can’t easily take out all units at once – a resilience that is crucial given that these units themselves might become high-priority targets for the enemy once their effectiveness is known.

Field Applications and Case Studies

Military Use Case: Forward Operating Base Protection (Ukraine Conflict)

To illustrate how the system would work in practice, consider a scenario drawn from the Ukrainian experience. In 2023–2024, Ukrainian troops often established temporary forward positions – for example, an outpost in a treeline or an urban strongpoint – which came under frequent Russian drone attack. Russian forces have used FPV drones carrying RPG-7 warheads to devastating effect against such positions, flying directly into foxholes or against vehicle hulls. Meanwhile, Ukrainian forces have done similarly to Russian positions. Traditional air defenses (like MANPADS or vehicle-mounted guns) have difficulty engaging these drones due to their small size and short engagement window.

Now envision that a Ukrainian forward operating base (FOB) is equipped with four Anti-Drone Perimeter Defense units (as proposed in this paper). They set up the units at roughly the four corners of their perimeter, each on a 2 m mast for a clear view. Early one morning, the acoustic sensor on the west side unit picks up the faint buzz of an incoming FPV drone approaching at low altitude. The system’s acoustic classifier flags the sound as a drone (distinct from the background diesel generator hum and distant gunfire) and triangulates with the north-side unit’s microphones to get a bearing. The networked system alerts the base: a warning might sound for troops to take cover, even as the turrets automatically orient toward the threat. Within a second, the west unit’s LIDAR has locked onto a tiny moving speck 100 m out, coming in fast over a field. The drone is perhaps 20 m off the ground, heading for the camp. The fire-control computer calculates the lead and range – it decides to engage when the drone crosses within ~60 m. At that point, the west turret fires its first barrel. A burst of tungsten pellets spreads into the drone’s path asiatimes.com. Many miss, but a few strike the quadcopter’s propellers and battery. Observers hear a shotgun-like report and see the drone destabilize and spiral down, crashing well short of the perimeter. If that shot had missed outright, the drone might have veered, but then the north turret (which also had visual on it by then) could fire its interceptor as a backup. In this incident, the drone is destroyed; any explosive it carried detonates on the ground harmlessly away from personnel. Moments later, another drone approaches from a different quarter – this time a fixed-wing loitering munition at higher altitude. The acoustic signature is different (a gasoline engine buzz), and multiple units pick it up. The system, recognizing a larger target, might choose a different engagement method – perhaps waiting until it’s overhead and then firing a near-vertical fragmentation shot. Through the day, the base fends off several such drones, expending only inexpensive kinetic rounds, and without needing human operators to manually scan the skies or spray bullets. This preserves ammunition and allows soldiers to stay under cover until threats are neutralized.

This scenario reflects what Ukrainian forces have improvised: human lookouts listening for drone motors and trying to shoot them down with rifles or machine guns (there are videos of soldiers unloading rifles at buzzing drones, usually with low success). Our system would vastly improve the detection and hit probability, automating the “detect and shoot” loop. It essentially creates a localized CIWS (Close-In Weapon System) for drones, akin to a mini Phalanx gun guarding an FOB. Importantly, it addresses the main challenge troops have voiced: “The challenge really is detection”reddit.com. Once you know a drone is there, shooting at it is possible – and a purpose-built system can shoot much more accurately than a startled soldier with an AK. By providing an autonomous detection and targeting capability, the system buys time and increases confidence in countering drone threats.

We can draw parallels to the Trophy APS on tanks: Israeli tank crews gained tremendous confidence once they had Trophy, knowing it would intercept RPGs they couldn’t even see coming. Similarly, infantry at a base could operate more securely with an active drone shield that knocks down threats coming over the wire.

Secondary Use Case: Law Enforcement and Civilian Protection

While conceived for military use, a scaled or modified version of this system has clear potential for law enforcement, critical infrastructure security, and even private landowners dealing with rogue drones. In recent years, there have been high-profile drone incursions into civilian airspace: for example, in 2024 a drone sighting over a packed NFL stadium in Baltimore caused a game to be halted and spurred the league to re-evaluate aerial security police1.com. In another case, a drone over a concert with 40,000 attendees led to an emergency stop of the show until the drone left police1.com. These incidents, though ultimately benign, highlighted how vulnerable public events are to potential drone-based attacks or disruptions. Police and event security increasingly seek means to detect, track, and if necessary, disable drones entering restricted airspace police1.compolice1.com.

A full military-style hard-kill system might be excessive or legally problematic in a civilian setting – firing shotgun shells into the air in an urban area is generally unsafe. However, the acoustic and LIDAR detection components alone could be invaluable for early warning and tracking. For instance, a few acoustic units could be deployed around a stadium or along a border of a secure facility to act as a “drone alarm.” These could cue security personnel or automated cameras to the presence of a drone. Law enforcement could then use more targeted countermeasures (like radio-frequency jammers or net guns) if lethal force is not appropriate. Notably, acoustic detection works especially well for the small hobbyist-type drones that are commonly used by careless or malicious actors, and which often evade radar and blend into visual clutter.

In more remote or private settings – say, a rural property owner concerned with drones spying on livestock or a prison facility combating drone contraband drops – a scaled-down version of the turret with a small scatter-shot device could be viable. In fact, there have been real cases of civilians shooting down drones that trespassed over their property, leading to legal battles over airspace rightsnpr.orgcontext.news. The frustration with intrusive drones has even reached lawmakers: in the U.S., a “Defense Against Drones Act” was proposed in 2025 to explicitly allow individuals to shoot down drones flying under 200 feet over their property with a shotgun (without facing legal penalties, provided they report the incident) burchett.house.gov. This underscores both the desire for and the controversy around civilian drone defense. A system like ours, if made available commercially in a legally sanctioned form, could allow a property owner to passively detect intruding drones and perhaps deploy a non-lethal countermeasure (like an entangling projectile or a directed jammer) to bring it down. For police, a rapidly deployable counter-drone unit could help secure accident scenes, crime scenes, or VIP events where unauthorized drones might be scouting or recording. In 2018, for example, FBI agents during a hostage situation were reportedly surveilled by hobby drones operated by criminals – a scenario that current law leaves law enforcement ill-equipped to handle in real time. A portable system that can be thrown up around a command post to watch for “eyes in the sky” would be a force multiplier.

It should be noted that in civilian contexts, rules of engagement and safety are paramount. Non-kinetic or low-collateral interceptors (nets, blunted projectiles, or just forcing the drone to land) would be preferable. The acoustic and LIDAR elements, however, remain the same challenge: detect the small drone. Our system’s approach to using multi-sensor fusion to reliably detect and track drones could certainly be adapted to non-lethal effectors for those environments.

Challenges and Considerations

While the proposed Trophy-inspired anti-drone system is promising, several challenges must be addressed in design and deployment:

• False Alarms and Discrimination: Acoustic sensors might pick up noises from friendly drones (e.g. one’s own surveillance UAVs) or environmental sounds. Similarly, the system might detect birds or flying debris with LIDAR. Ensuring a high detection probability for real threats while keeping false positives low is critical – otherwise the system could waste ammo or even pose a hazard by firing at non-threats. Advanced classification algorithms, multi-sensor confirmation (requiring acoustic and LIDAR confirmation before trigger), and perhaps integrating an electro-optical camera for visual verification can mitigate this. The system could even employ an “identify friend or foe” (IFF) mechanism for known friendly drones via RF interrogation or visual tags.
• Safety and Rules of Engagement: On military bases, any autonomous weapon raises safety concerns – one must prevent friendly fire incidents. The system should be programmed with safe zones where it will not fire (e.g. inside the perimeter or in the direction of known friendly positions, aircraft, etc.). In active combat, this is easier (anything coming from enemy side at low altitude is likely hostile), but in mixed environments (e.g. urban areas or UN peacekeeping missions), careful control is needed. A man-in-the-loop mode might be used where the system tracks automatically but a human operator confirms before firing, except in imminent attack scenarios. Particularly for law enforcement use, legal frameworks would likely require human authorization before any kinetic action.
• Weather and Environment: Extreme weather can degrade both acoustic and LIDAR performance. High winds scatter sound and could mask drone noise; heavy rain or sandstorms could blind the LIDAR. The system should have environmental sensors to adjust sensitivity (e.g. increase acoustic gain in wind or switch to alternate sensors if one is ineffective). It might also integrate radar as a complementary sensor for when conditions hinder the primary ones, although a high-performance short-range radar would add to cost and power needs. Night operations should generally be fine since acoustic and LIDAR are not dependent on daylight (though adding a thermal camera could further help at night).
• Power and Logistics: Running multiple sensors, motors, and possibly a cooling system for the LIDAR continuously will consume power. In a base scenario, generators can be used; for dismounted use, battery life will be a limiting factor. Efficient power management (idle modes when no threats, waking up on acoustic cues) can extend runtime. Ammunition resupply is another factor – if drones attack in swarms or repeatedly, the system might expend dozens of rounds. The design should allow quick reloading (perhaps a drum magazine of shells or a clip of airburst munitions). Soldiers would need to carry extra ammo and have a reloading drill.
• Countermeasures: Adversaries will likely develop counter-countermeasures. They might attempt to acoustically dampen drones (e.g. better propellers or noise-cancelling tech) or use very quiet electric glider drones. They could fly in pairs – one drone to bait the system to fire and reveal its position, then a second to attack the now-located turret. The system should thus be as low-signature as practical (perhaps using camouflage and not emitting except LIDAR which is invisible). Mobility helps – units can reposition to avoid being precisely targeted. Additionally, our system might incorporate a degree of redundancy: multiple smaller barrels rather than one, so a single lucky hit by the enemy doesn’t knock out all capability.
• Integration with Broader Defense: This system would ideally tie into a larger network (especially in military use). For instance, if a drone is detected, it could cue electronic warfare units to try jamming it (two layers of defense). It could alert all nearby units via battle management systems. If a higher-level radar or C2 system has tracking on incoming drones, it could feed that to the local system as well. Ensuring interoperability (common communications protocols, etc.) will increase effectiveness.

Despite these challenges, the technology building blocks are available and have shown success individually. Ukraine’s improvised systems have demonstrated that passive acoustics + human shooter can defeat drones armyupress.army.mil; our proposal essentially automates and enhances that formula. Active protection philosophy from armored warfare shows the value of engaging threats in the air before impact twz.com.

Conclusion

The rise of small drones – particularly FPV and other mini UAVs – has transformed the threat landscape for military and security forces. They have proven capable of surveillance and precision attack, while eluding many traditional detection systems, as vividly illustrated in the Ukraine war twz.comarmyrecognition.com. In response to this challenge, we have outlined a conceptual lightweight anti-drone perimeter defense system that marries acoustic sensing, LIDAR tracking, and kinetic interception in a Trophy APS-inspired framework. This system is designed to be deployable by troops on the ground, creating an active protective dome over forward bases or other high-value sites. By leveraging passive acoustic sensors for early detection defenseone.com and a rapid hard-kill mechanism (a scatter-shot turret) for final interception asiatimes.comasiatimes.com, it addresses both halves of the counter-drone problem: finding the threat and neutralizing it.

The Trophy APS analogy is apt – just as Trophy changed the survivability of armored vehicles against missiles, a portable drone APS could significantly reduce the danger posed by buzzing quadcopters and loitering munitions to dismounted units. The system emphasizes low-cost and modularity: its key components (microphones, LIDAR, shot shells) are relatively inexpensive compared to guided missiles or high-end radars. This is important when facing swarms or sustained drone assaults, where using a $50,000 missile to down a $500 drone is not sustainable. In Ukraine, a network of $400 acoustic sensors linked to gunners has already exemplified the cost-effective approach, reportedly costing less than a pair of Patriot missiles to cover the whole country defenseone.com. Our proposed system could protect a local area for a similarly economical price point, while drastically increasing force protection.

Military adoption of such technology could happen in the near term. Already, some Western militaries are testing shotgun-based drone defenses and AI-enabled detection systems. It is plausible that within a couple of years, platoon-level anti-drone kits (including sensor fusion and smart turrets) could be standard issue. This concept also fosters greater situational awareness – even when not firing, the acoustic/LIDAR network serves as extra “ears and eyes” on the battlefield, alerting units to enemy drone activity and possibly locating the drone operators via triangulation techniques (an aspect we did not delve into deeply, but if one can track the drone path backward, one might find the launch point or operator).

For law enforcement and civilians, we stressed that the same core detection capability is a boon. As drones become ubiquitous, ensuring public safety requires the ability to detect illicit drone use – whether it’s a paparazzi drone over a private estate or a potential terror threat over a crowd. The adaptation of a perimeter defense system to these roles might focus on early warning and non-lethal interdiction, but the principle remains: one must actively guard the skies on a micro-scale, just as larger defense systems guard against traditional air threats.

In conclusion, the lightweight anti-drone perimeter defense system proposed here is a synthesis of combat-proven strategies and emerging technologies. It is conceptually and technically grounded in real-world data: we know drones can be heard defenseone.com, we know they can be shot down with spread munitions armyupress.army.mil, and we know automated defenses can react faster than human reflexes armyrecognition.com. While further engineering development and field testing would be required to refine such a system, the outline presented provides a roadmap for how militaries (and perhaps police forces) could counter the small drone threat proactively. In an era where “every soldier is a C-sUAS soldier” by necessity armyupress.army.mil, tools like this will be critical in leveling the playing field. By taking inspiration from the Trophy APS and tailoring it to current needs, we can protect those on the ground from the eyes – and bombs – in the sky.

Example:

References:

Altman, H., & Rogoway, T. (2024, July 24). Ukraine’s Acoustic Drone Detection Network Eyed By U.S. As Low-Cost Air Defense Option. The War Zone. defenseone.com defenseone.com

Army Recognition. (2024, July 23). Focus: Adapting Protection Systems Against Drones – Trophy APS Put to Test. ArmyRecognition.com. armyrecognition.com armyrecognition.com

Bryen, S. (2025, April 5). Scattershot shotguns a good way to kill precision drones. Asia Times (republished from Weapons and Strategy newsletter). asiatimes.com asiatimes.com

Decker, A. (2024, July 20). Ukraine’s cheap sensors are helping troops fight off waves of Russian drones. Defense One. defenseone.com defenseone.com

Mendelson, Y., & Tabbara, R. (2025, Feb 28). How law enforcement can detect and apprehend criminal drone pilots at large events. Police1. police1.compolice1.com

Trevithick, J. (2024, Oct 8). Trophy Armored Vehicle Protection System Gains New Ability To Defeat Drones. The War Zone. twz.com twz.com

U.S. Army (Army University Press). (2024). Bayraktars and Grenade-Dropping Quadcopters II: Year Two of Ukraine-Russia Drone Warfare (Military Review Online Exclusive). armyupress.army.mil

Robin Radar. (n.d.). Why Traditional Radar Isn’t Effective at Tracking Drones. Robin Radar Systems Blog. robinradar.com

CRFS. (2023). Drone Detection: Myths and Reality. CRFS Technical Blog. crfs.com

Office of Rep. Tim Burchett. (2025, Mar 6). Rep. Burchett introduces Defense Against Drones Act (Press Release). burchett.house.gov

The Firearm Blog (Moss, M.). (2024, Sep 3). Benelli Introduces the M4 A.I. Drone Guardian. The Firearm Blog. thefirearmblog.com thefirearmblog.com