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Until the dawn of military aviation a century ago, commanders always wanted to know what lay beyond distant hills or just over the horizon. The infantry squad of today has the more modest requirement of wanting to know what might be lurking behind a nearby wall or terrain ridge, or in the case of urban operations what might be lurking around the next street corner.

Since tactical air assets may not be able to provide a timely answer, there is a requirement for lightweight and rapidly-deployable reconnaissance systems. The goals of short-range reconnaissance are to determine the location, strength, and potential tactical weaknesses of enemy forces – information needed in order to determine a suitable course-of-action.

Unmanned Air Vehicles (UAVs) have become an established method of providing situational awareness for ground forces, but many existing types are controlled at a higher level than that of infantry squads, so getting coverage of the local combat area could take more time than is available to front-line soldiers during a fast-evolving tactical situation. For units which need urgent reconnaissance information, the most obvious solutions are small remotely-controlled air or ground vehicles equipped with cameras and other sensors.
As any major defence exhibition will demonstrate, there is no shortage of small UAVs or even unmanned ground vehicles (UGVs), but in many cases the manufacturer of the hardware and the soldiers who need such recce aids will have very different ideas as to what constitutes “lightweight” or “easily deployable”.

Ideally, what the front-line soldier needs is a tiny hand-launched UAV, and this has led to the development of ever-smaller and lighter designs. Many larger models are powered by a small piston engine, but the smaller hand-launched examples use electric motors.


With manufacturers now offering systems that can be categorised as ‘mini-UAVs’ or even ‘micro-UAVs’ and ‘nano-UAVs’, the US Army has now fielded a range of lighter-weight systems. At company level, it uses the hand-launched Aerovironment RQ-11 RAVEN in -11A and -11B variants. Procured as an urgent wartime requirement, and used in operations Enduring Freedom, Iraqi Freedom, and New Dawn, the RAVEN series is reported to be in service with around 10 countries. The RAVEN has a wingspan of 1.37 metres, weighs 1.8 – 1.9 kg, and has a tactical radius of 10-12 km.

The USMC is known to operate Aerovironment’s RQ-12A, a 1.5 kg micro-UAV with a wingspan of 1.02 m, a maximum speed of 45 kn, and operating altitude of 150 m, and an endurance of 50 min. Other known users are Australia and the Netherlands.

At platoon level, the US Army will deploy the Short-Range Reconnaissance (SRR) UAV. Six rival off-the-shelf commercial designs from Altavian, Lumenier, Parrot, Skydio, Teal Drones, and Vantage Robotics were evaluated in 2019 and early 2020 against a requirement for a UAV weighing 1.4 kg or less that would be able to fly continuously for 30 minutes, and be able to land at a vantage point overlooking a target area in order to extend its total mission time. In April 2020, Parrot announced that was working with its US partner NEOTech to build a final prototype batch for delivery to the US Army and the Defense Innovation Unit (DIU) in July 2020.

When it created its PD-100 BLACK HORNET micro-UAV, the Norwegian company Prox Dynamics gave a new meaning to the term “tiny”. Taken into service by the Norwegian and UK forces, and used by the latter during combat operations in Afghanistan, the complete system weighs only 1.3 kg, and includes an air vehicle that weighs only 18 g. This tiny rotary-winged air asset has an airspeed of about 18 km/hr, a line-of-sight range of 1.5 km, and an endurance of about 25 minutes. Launched by hand and controlled via a tablet, it carries a tiny video camera whose real-time output is downlinked to its user.


In 2016, the US Army tested the BLACK HORNET improved version of the PD-100 during Maneuver Battle Lab Army Expeditionary Warrior Experiments at Fort Benning in Georgia, and US special operations forces are reported to have used the system operationally.

In December 2016, Prox Dynamics was acquired by FLIR Systems in a deal worth US$134M. Following a UAV “fly-off” at Fort. A.P. Hill, Virginia, that tested three rival systems, the US Army awarded FLIR Systems a US$2.6M order for 60 BLACK HORNET III UAVs on 30 May 2018. These would enter service as the Soldier Borne Sensor (SBS) system. The hardware that had been used in the fly-off was later fielded by a Brigade Combat Team, and the Army announced the long-term goal of providing most of its infantry squads with one Soldier Borne Sensor system. This would consist of a base station equipped with a hand controller and display unit, and two air vehicles – one equipped for day missions and the other for use at night. The first US unit to take the system into action was a brigade of the 82nd Airborne that deployed to Afghanistan in 2019.

The BLACK HORNET III air vehicle is 166 mm long and a total weight of 33 g. It has a two-bladed main rotor or 123 mm diameter, and a two-bladed tail rotor mounted at the end of a slim tailboom. It has a ceiling of more than 1,000 m, and an endurance of 20 minutes. Two alternative payloads are available – one for day use and combining two EO cameras, and a night configuration with sensor-fused imagery from one EO camera and one thermal imager.

Like the PD-100, BLACK HORNET III uses a joystick-based control unit and a separate display. The air vehicle can be flown under manual control using imagery from the on-board sensors, or guided by GPS along a pre-programmed route. The original PD-100 version could sometimes lose its radio link and/or GPS signal when operating in urban conditions, but the BLACK HORNET III version is designed to operate in GPS-denied conditions such as the interior of buildings. The air vehicle will fly a return-to-base route once its mission has been completed, or if it loses datalink connectively.

A Vehicle Reconnaissance System variant mounts an array of four launch containers (known as ‘cassettes’) for air vehicles. The system can control one or two air vehicles simultaneously, and integrate these into a battlefield management system. FLIR Systems plans a developed version that would allow the air vehicle to return to its launch cassette at the end of the mission, so that it can be recharged for further use.

BLACK HORNET has now been ordered by around 30 countries. Perhaps the biggest problem this system faces is its cost. When the UK ordered a batch of 160 BLACK HORNET systems in 2013, the pricetag was £20M.

Four-rotor quadcopter drones have proved popular with civilian users, so it is hardly surprising that this layout has been adopted for military applications. Examples include the Aeryon SCOUT, which weighs 1.4 kg without a payload, and China’s DJI Mavic Pro which weighs just under 0.75 kg, and has an endurance of just over 20 minutes. Mavic Pro is reported to be used by the Israel Defence Forces as a company-level asset.

EMT’s FANCOPTER has a less conventional configuration which combines two coaxial rotors used to provide lifting power, and three small steering rotors. It weighs 1.5 kg, and has an endurance of around 3 hours.

Ground-Based Systems

Ground-based robotic systems have been used for more than 40 years, but most early examples were relatively heavy and designed for Explosive Ordnance Disposal (EOD) tasks. Their payload included TV cameras, manipulator arms, and systems intended to neutralise explosive devices. Since the manipulator arms were sized to handle relatively heavy loads, these vehicles were relatively heavy, and had to be transported to their operating location. To be an effective tactical reconnaissance aid, a UGV needs to be light enough to be carried to a frontline position.

For propulsion, the normal solution is to use battery-powered electric motors to drive wheels or tracks. On a small vehicle, these tracks will often be made from rubber or a similar material, but in some cases a specialist form of track better suited to sandy or muddy terrain is used.

Some UGVs are based on a miniature version of the tracked or wheeled chassis used by manned fighting vehicles, but some have an articulated chassis that will be better suited to rough terrain and the task of climbing or descending stairs. One example of this is the Delta Micro. Originally developed by Inuktun Services. This is manufactured by the Canadian company Recce Robots International (R2i2). Delta Micro is driven by two electric motors. As its original designation as the Variable Geometry Tracked Vehicle (MVGTV) indicates, the vehicle’s configuration of three wheels per side allows the shape to be altered to match the tactical situation. In its sensor-raised configuration, the tracks take on a triangular layout.

The sensor payload of UGVs often consists of one or more day-only or day/night TV cameras able to display imagery of the area around the vehicle, and a microphone able to capture nearby sounds. Some form of built-in source of visible-light or infrared light is also carried.

Control of the vehicle and its sensors is normally handled by a unit that will allow the vehicle to be set to travel at a desired speed, steered, and stopped as required. It may well have the ability to direct the camera and light source towards an area of interest. Just as with the vehicle itself, this hardware should be as light as possible. It may be custom-designed, or based on a PC, tablet, or smart phone Communications between the ground station and the vehicle can be either by cable or via a radio link. While a cable will be of limited length – probably less than 100 m – a radio link could in theory operate at ranges of up to 1 km. In practice, the performance of a radio link could be affected by the local terrain, and in built-up areas associated with urban warfare could be limited at around 300 m.

Throwable Systems

By acquiring Endeavor Robotics in February 2019, FLIR Systems was able to add the FirstLook UGV to its product line. Optimised for operation in areas in which it is difficult for a UGV to manoeuvre, FirstLook is designed to cope with climb obstacles up to almost 18 cm in height, to turn in place, and to self-right if capsized. The last of these features in important for a UGV that is marketed as a ‘throwable’ system. It weighs 3 kg, and carries an audio subsystem, plus colour TV cameras that incorporate zoom lenses and an illuminating light. Another throwable UGV in this weight class is Nexter’s four-wheeled NERVA LG. Prototypes weighed 4-5 kg, but 3 kg is the target weight for production examples.

The PocketBot three-wheeled UGV was developed by Novatiq as a throwable system. It weighs 0.85 kg and is equipped with a forward looking optical sensor with an X8 zoom lens that can be trained in elevation and depression, an IR illumination source, a microphone, and a small loudspeaker. These audio subsystems are linked to a bidirectional communications link, so allow the operator to talk with persons located by the UGV.

Another design that incorporates a two-way audio communications link is the 1.3 kg DRAGON RUNNER Mini tracked UGV developed by QinetiQ North America. Like the control link of this throwable UGV, the on-board two-way audio subsystem has a maximum range of 200 m, and according to the manufacturer, communications can be maintained through up to four interior walls of a building.

An even more dramatic delivery system is used by the SG Robot developed by the South Korean company Hanhwa. Less than 0.65 kg in weight, and propelled by a combination of two wheels and a trailing arm, this UGV is designed to be launched in the same manner as a rifle grenade, and delivered to target areas up to 250 m away. When used against targets more than 100m distant, a second UGV will be needed in order to serve as a communications relay. The vehicle carries a low-light TV camera, as well as a small explosive or tear-gar warhead that can be triggered by radio command.

Not all throwable systems incorporate propulsion. As its name suggests, the 0.6 kg Sphere developed by Russia’s SET-1 is of spherical configuration. Designed to be thrown into an area of tactical interest, it is 90 mm in diameter, and has no propulsion system. It relies on the weight of the lithium-ion batteries housed in its lower hemisphere to orientate the unit after it lands in the target area. The upper hemisphere contains an array of four cameras that provide 360-degree coverage, a microphone, and a transmitter that sends the imagery to an Operator Control Unit.
Urban warfare can create problems for many types of UGV. For example, a vehicle dispatched along the rail tunnels of an underground rail system, could face the potential situation of having to get from the rail level to that of the platform of a station, while exploration of the station could involve hurdles such as a passenger ticket barrier which has jammed in the closed position. One novel approach to UGV mobility is the URBAN HOPPER developed by Sandia National Laboratories. As its name suggests, this 5 kg unit can jump to heights of up to 8 m. This capability allows it to enter buildings through ground-floor windows, or to cope with a flight of stairs.

One problem with UGVs is that they must avoid obstructions such as rocks, tree stumps, and patches of impassably-steep terrain, while not venturing into hazardous areas such as bogs. For the moment, a UGV needs hands-on guidance from its operator, but artificial-vision software could prove a long-term solution to this task. As with UAVs, technology is providing the front-line soldier with personal-recce capability that would have seemed close to science fiction some 20 years ago.

Following an earlier career in engineering, Doug Richardson is a defence journalist specialising in topics such as aircraft, missiles, and military electronics.