Counter-UAS: fighting drones with Bullfrog, Skyranger & Co

Counter-UAS, the defence against unmanned aerial vehicles (UAV), is moving ever further into focus for all armed forces in view of the threat situation in conflicts. Recently, the call for so-called hard-kill systems in particular has grown ever louder.

The reason: soft-kill solutions, that is, interrupting the radio link (jamming) that a UAV may need in order to be remotely controlled, to transmit an image or to determine its position via GPS, are increasingly being circumvented and thus rendered ineffective. A current example is the cable-guided first-person view (FPV) drones in Ukraine, which receive their control signal via fibre-optic cable and send their image back over it. Another example is drones with image recognition software, which no longer need a control signal. Also increasingly relevant are unmanned aerial systems that navigate by optical terrain recognition; in theory this works, at least over land, without range limitation. Jamming has no effect on such systems.

Most recently, the US company ACS (Allen Control Systems) attracted attention with its new hard-kill system called Bullfrog. Bullfrog relies on purely optical target search, target acquisition, target recognition and target tracking, and on a small calibre. “Machine vision” and pointing accuracy are at the centre and are intended to enable a perfectly ordinary M240 machine gun in 7.62×51 NATO calibre to neutralise a detected UAV with just a few rounds.

Recipe: high muzzle velocity and direct hits with a small calibre

This sets ACS Bullfrog apart from the crowd. The vast majority of systems in service or at least under trial so far rely on multi-sensor suites, specifically also on microwave radar and on automatic grenade calibres in the range of 25 to 40 millimetres.

The advantage of radar: it is all-weather and day/night capable, but the devices are usually also very expensive.

The advantage of larger calibres: the rounds act on the target through explosion and fragments, and there are also various techniques for detonating them without impact, for example by proximity or by means of “timing” (time fuze), as in the case of Ahead ammunition. The disadvantage of the rounds: they are relatively expensive, they are large and limit the number of rounds at the gun, and the V0, the velocity at which the round leaves the barrel, is low.

For comparison: with the M240 the V0 is around 850 metres per second, so a target at a distance of 250 metres is hit in around 3/10 of a second.

With the 40-millimetre automatic grenade launcher from Heckler & Koch, by contrast, the V0 is just under 240 metres/second. To cover a distance of 250 metres, the grenade therefore needs slightly more than one second. If one bears in mind that even commercially available small drones can reach speeds of 15 to 20 metres per second, it becomes difficult to hit them.

The automatic grenade launcher can be upgraded to use programmable grenades. A direct hit on the target is then not required; the effect on the target roughly corresponds to the explosion of a hand grenade. Against a small drone target the destruction radius will be relatively small, possibly one to two metres. Moreover, the probability that a fragment hits the drone and puts it out of action drops sharply. That is why several grenades are fired.

In future, lasers will also gain in importance. The first systems are already being tested as prototypes or in small series. First attempts to bring them into service are discernible. They are still very large systems, some taking up an entire semi-trailer truck. And the effect on the target only occurs after irradiation lasting several seconds. Nevertheless, it is already clear that sooner or later there will be no way around the laser.

Success in firing trials

Ultimately, the truth lies on the field – the firing range. ACS had applied and was invited to “T-REX 24-2”. The US Defense Department’s Technology Readiness Experimentation exercises serve to present state-of-the-art military technologies for rapid technology development.

This year's second event took place from 19 to 26 August at Camp Atterbury, Indiana.

According to ACS, Bullfrog is said to have been the only system demonstrated that was able to carry out the entire chain of detecting, tracking, identifying and engaging drones on its own. This includes engaging several drones in quick succession.

The cost per drone kill by Bullfrog is said to be around 10 euros.

Austrian Armed Forces equip with Skyranger and Panther for counter-UAS

The Austrian Armed Forces (Bundesheer) also pursue several approaches to counter-drone defence. In the soft-kill field, for example, ELDRO (electronic warfare for counter-drone defence) has made a name for itself in recent years. It uses state-of-the-art technology from the German world market leader Aaronia.

The Pandur Skyranger is eagerly awaited. With 36 systems from the German manufacturer Rheinmetall, built on Pandur Evolution 6×6 wheeled armoured vehicles produced by General Dynamics European Land Systems-Steyr in Vienna-Simmering, the Austrian Armed Forces are not only the launch customer but have so far also placed the most firm orders of all customers for this modern air defence system.

To create a further pillar in the fight against drones, the Bundesheer, together with the manufacturer ESLAIT, is working to upgrade the WS4 Panther electrically remote-controlled weapon station (EFWS) of the Pandur wheeled armoured vehicles for counter-drone defence.

In the basic version, a 12.7-millimetre machine gun is fitted on the Panther. Aiming is done remotely with daylight and thermal imaging cameras, a laser rangefinder and a searchlight. There is also a launcher system. Fully stabilised and with automatic target tracking, the WS4 can hit targets very precisely even on the move.

At “Airpower 2024”, a turret version with a 40-millimetre automatic grenade launcher, a radar, a jammer and a considerably more powerful searchlight was presented for the first time. With precise trajectory measurement, jamming, dazzling and programmable grenades, the aim is to successfully tackle drones in future as well.