Top Attack 155 BONUS In Ukraine

On Wednesday, 4 January, a Russian telegram channel shared several photos of what appear to be miniature satellites. These are in fact 155 BONUS submunitions, an advanced anti-armour, top attack artillery round. Each 155 BONUS round carries two submunitions capable of striking down on a target vehicle once over the target area.

As we’ve seen in other articles/videos including out look at Javelin, NLAW and Russia’s PTKM-1R mine that top-attack weapons can be extremely effective.

Salvaged 155 BONUS submunition (via social media)

Ukraine has received 155mm howitzer systems from Western countries (including DANA, CAESAR, PzH 2000, Zuzana 2 and AHS Krab), with conventional ammunition these are able to accurately engaging targets at considerable distances but the BONUS round allows a 155mm shell to deliver two submunitions capable of penetrating any tank’s top armour with impressive accuracy.

Development of BONUS or the BOfors NUtating Shell (nutating means rocking or swaying) began in the mid-1980s and was developed by Sweden’s Bofors and Nexter of France. Since Bofors’ heavy weapons division was bought out by BAE Systems in 2005, the system has been part of BAE’s portfolio.

BONUS has a base bleed unit which extends its range out to 35km (nearly 22 miles). Once fired the shell separates to deploy two independent sensor-fuzed submunitions. Once separated these submunitions deploy a pair of winglets and rapidly rotate in flight to enable their built-in sensors to detect targets within their search footprint.

Labelled cutaway of a BONUS shell (US Army)

The search footprint can span up to 32,000 square meters with a diameter of 200m in a helical pattern. The munition uses multi-band passive infrared (IR) and LADAR (laser imaging, detection, and ranging) to detect its targets. Once detected the submunition fires its explosively formed penetrator, which can travel at more than 2000m/s. BAE states the penetrator can penetrate between 100 and 140mm of rolled homogenous armour.

BONUS has been in service with the French Army since the early 2000s and has also been procured by Sweden, Finland and Norway. Most recently in 2018 the US Army selected the round for their Cannon Delivered Area Effects Munition (C-DAEM) programme and has been actively procuring it through several contracts since.

Diagram illustrating BONUS’ basic principle (BAE Systems)

A similar munition SMArt 155, developed by Rheinmetall and Diehl BGT Defence, which uses a parachute to slow the submunitions descent rather than winglets, is also believed to be in use in Ukraine. BONUS and SMArt do not fall into the category of weapons banned under the 2008 Convention on Cluster Munitions as they comprise of just two submunitions and both have onboard self-destruction mechanisms. The BONUS round seen in these photographs obviously did not engage a target and its self-destruction mechanism didn’t destroy the submunition before it landed.

The Russian telegram channel that shared the photographs of the munition state that it was found in the Donetsk region. The same post suggested some potential countermeasures, including covering heat signatures with polythene and obscuring the shapes of vehicles might help mitigate the risk posed by BONUS rounds.

Salvaged 155 BONUS submunition (via social media)

From the photographs themselves we can see the submunition is marked No.3374, France, and ‘HMX’ – a type of high explosive. At the top it is marked ‘155 MM AC F1 BON’. The ‘LUL’ marking likely refers to Luchaire Defense. In the second photo we can see the damaged face of the submunition, its EFP plate, the metal winglets and the pop-out sensor assembly with what appear to be three lenses. 

In terms of videos from in theatre that show the use of BONUS there are a number of fairly low-resolution drone videos showing suspected uses of the shells – some of these have also been suggested to be SMArt 155. A video from July perhaps shows BONUS in action, there is no visible parachute, as used by the SMArt 155, visible but there are what appear to be two descending submunitions – the first of which detonates above the target, firing an EFP down onto targets.


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Bibliography: 

155 BONUS, BAE Systems, (source)

155 BONUS, Tankist4, (source)

155 BONUS Mk 2, BAE Systems, (source)

155 Bonus EFP, Bofors, (source)

155mm SMArt, GD-OTS, (source)

Artillery Paratroopers Fire BONUS Mark II, US Army, (source)