Rheinmetall Skyranger family: defending mobile formations against drones and not only
A one-day event was organised by Rheinmetall to show its Skyranger 35 and Skyranger 30 systems in real during a live fire demonstration at the Ochsenboden firing range, in central Switzerland, to highlight the effectiveness of its systems against drones as well as other air and ground targets
Protecting friendly forces from the most recent air threats, which tend to be smaller, faster, unmanned, with increased autonomy, and reduced radar cross section, not to mention the low cost of some “home-made” solutions that allows saturating air defence assets, has become a must for western armies. Friendly formations in the combat, combat support and rear areas are exposed to a number of risks coming from the third dimension, drones, loitering munitions and more classical air breathing aircraft, as well as surface-to-surface missiles and rockets and mortar and artillery shells. To these we must add ground threats ranging from tanks to infantry fighting vehicles, antitank missiles, and rockets.
Short decision cycle, high level of coordination, the need to protect formations on the move against air threats, make today ground-based air defence an increasing complex business. Transparent battlefield, through several types of air-based observation and targeting assets ranging from satellites to small Class 1 targeting drones, added complexity also to ground assets requirements.
In the past years Rheinmetall developed its Skyranger concept, exploiting in-house existing systems, improving them, and adding newly developed elements. Among the key building blocks, we find the 35 mm x 228 KDG and the 30 mm x 173 KCE revolver cannons, with respective nominal rates of fire of 1,000 and 1,250 rounds per minute.
The final kill-chain element, the ammunition
Let us start from the last element of the kill-chain, the round. The 35 and 30 mm families of rounds available to the Skyranger all leverage on the original 35 mm AHEAD (Advanced Hit Efficiency And Destruction), which development by then Oerlikon Contraves began in the late 1980s mostly aimed at neutralising incoming missiles, production starting in the mid-1990s. The AHEAD concept is based on the accurate measurement of the round speed at muzzle, which allows precise programming of the time fuse, the latter activating a very small explosive charge, less than 1 gram HE according to company data, that “opens” the round generating a cone of tungsten cylinders in front of the target. All witness plates show a typical spiral pattern of shrapnel, the cutting edge of tungsten cylinders improving penetration. The original AHEAD round, now known as PMD062, contains 152 tungsten cylinders, the payload of the 35 mm round being 500 grams while that of the 30 mm round is 200 grams. Two other 35 mm rounds were developed since, currently known as KETF (Kinetic Energy Time Fuse), one aimed at the C-RAM (Counter Rocket-Artillery-Mortar) mission and one more focused on the C-UAS (Counter Unmanned Air Systems) mission. The first one is known as PMD330 and contains 407 cylinders, of course smaller than the ones contained in the original AHEAD munition. Even smaller are the 675 cylinders contained in the PMD428. Looking at the witness plates of those three 35 mm rounds the difference in the number of pellets is pretty obvious as well as the higher density of the ones loaded with smaller fragments; the PMD428 pattern featured also a smaller overall diameter, which further increased the density. The reason of that is the need to intercept very small UAS, one of them smaller than a smartphone being shown after the “treat” by the Skyranger.
Coming to the KETF 30 mm family, currently only one round, the PMC388 is available; it contains 162 cylinders which dimensions and weight are the same of those of the PMD330 round. A new 30 mm round is currently under advanced development, the PMC455; EDR On-Line understood that the configuration is now frozen, the witness plate showing a considerable density. No data were provided on the number of cylinders for the munition under development, but these should be around 550, which considering the payload means they should be smaller than those of the PMD428, underlining the focus on neutralising very small UAS.
The availability of those rounds allows to optimise the effects according to the type of target, Rheinmetall being also ready to develop munitions with mixed types of cylinders, to be effective against a wider type of targets, should a customer require it, EDR On-Line understood. Beside drones and other air threats, KETF munitions are effective also against land soft targets, while in the case of armoured vehicles they “blind” them damaging their optronic sensors, as well as against small and fast naval targets, such as jet-ski and speed boats. Depending on targets, the range of the 35 mm cannon is around 3.5 km while that of the 30 mm one is between 2 and 2.5 km.
Guns and sensors
The main difference between the two cannons is that the 30×173 mm one features a linked ammunition belt while the 35×228 mm has a linkless ammo feed. The turret armed with the 30 mm KCE has 300 ready-to-fire rounds and reloading is done via a logistic vehicle, or with single straps of ammo by the crew itself. The SR35 armed with the 35 mm KDG hosts 252 ready rounds, reloading being carried out in less than 10 minutes by replacing the two magazines at the back of the turret.
Besides having cannons in different calibres, the two versions of the Skyranger (SR) also feature wholly different target detection, acquisition and tracking suites.
The SR30 detects targets using the Hensoldt Spexer 2000M X-band AESA radar which single flat antenna covers 120°, hence three of them are fitted to the turret, one at the back and two at the front, covering the whole 360°. The Spexer 2000M is capable of spectral-based micro-doppler target classification, and can operate in high clutter environments, such as heavy rain or urban scenarios. It can track-while-scan over 300 targets on each 120° sector and can of course operate also on the move. The Hensoldt radar is air-cooled which makes its installation simpler and lighter. Once the target detected, this must be acquired and tracked. The SR30 carries out these functions using an electro-optic head that includes a daylight TV camera, an infrared camera and two laser rangefinders, a wide field of view one for aerial targets and a narrow field of view one for ground targets. The head rotates freely over 360°, its elevation arc being -5°/+85°.
Coming to the SR35, here the radar is the S-Band AMMR (AESA Multi-Mission Radar) by Rheinmetall, which single AESA antenna covers 90°, hence four of them are installed around the turret. A software-defined pulse Doppler multi-mission radar water-cooled, the AMMR can scan simultaneously a wide range of air threats. The acquisition and tracking package features an optronic suite with the same type of sensors used in the SR30, to which Rheinmetall KuTRG (K-under band Tracking Radar Gun) is added. The head can rotate ±150° in azimuth while its elevation arc is -10°/+85°.
For classification and identification, both the SR30 and SR35 rely on an IFF (Identification Friend or FOE), on the operator skills and on an algorithm-based Co-Classifier which proposes its solutions to the operator. Should the target be considered a threat, it is now up to the cannon and ammo to neutralise it. Customers can also add VSHORAD fire-and-forget missiles such as the MBDA Mistral 3 or Raytheon Stinger to the turret.
A platform agnostic, flexible and scalable system
At the static display in Ochsenboden the Skyranger turret was visible installed on a Lynx 41 tracked infantry fighting vehicle as well as on a Piranha 8×8. Depending on configuration, a Skyranger turret has a mass of 4-4.5 tonnes. A lighter version of the SR30 is currently under development for Austria, which Army intends to install it on the Pandur 6×6; no more details were provided, but the number of ready ammunitions will certainly be lower than that in the standard turret.
All Skyranger have a crew of three, a commander, an engagement operator and a driver; the commander is in charge of air and ground surveillance, decision making and communications to the upper command level, while the operator supports the commander in the surveillance task, executes the mission, and provides battle damage assessment.
EDR On-Line understood that a two-man crew solution can also be adopted. What was made clear was the importance to rotate crews in order to keep the system fully operational, an additional burden for the logistic support system; Rheinmetall considers a three-crew system the most valuable solution, one in rest, one operational and the third ready to take over. The company considers that the same manpower, being air defence trained, could also be employed on MANPADs, these VSHORAD systems possibly leveraging information from Skyranger sensors.
Beside these two vehicles, at the static display two mobile active sensor systems were also exhibited.
Hensoldt was showing a Mercedes G-Wagen fitted with three Spexer 2000M antennas on the top, while Rheinmetall was showcasing a Mission Master UGV fitted with four AMMR antennas. Both solutions are proposed to split the active sensor from the effector, increasing the latter survivability. Rheinmetall made it clear that the system on show was the mock-up of an operational concept, the company still having to verify the capacity of the basic Mission Master to provide power to the radar and data-link to make the system operationally viable, the bigger Mission Master XT being eventually ready to replace the smaller robotic vehicle.
Such a solution might fit well into the Skyranger system architecture; the Skymaster battle management system used is scalable and flexible, and the fact that the Skyranger is capable to perform all four steps, detection, acquisition and tracking, classification and identification, and finally engagement, allows deploying it as a stand-alone or ad-hoc tactical unit, known as CN0 (Control Node 0) level, at battery level tactical unit (CN1), and up to battalion task group level (CN2). When multiple Skyranger are deployed, the usual distance between them ranges from 1 to 3 km, depending on terrain and scenarios.
The higher the level, the more the networking among systems as well as information provided by higher echelons allow to improve effectiveness. A nominal battery would include several Skyranger vehicles, usually four to six, one Skyranger radar vehicle, a Skyranger CN1 node and a command vehicle, both the radar and command vehicles being based on the same mobility platform of effector vehicles to ensure the same level of mobility. At the upper level the CN2 usually fits into a shelter, installed on a high mobility truck.
Firing in Ochsenboden
Moving to the firing range, a novelty was visible. The SR35 turret was installed on a Leopard 1 chassis, a solution dubbed by some people the “Gepard 1.5”. According to Rheinmetall, numerous potential customers are still fielding this tank, which could become a viable platform for a Skyranger solution aimed at operating with heavy formations. The tank hull must be fully modified, the driver remaining on the front-right side, the engagement operator being at his left, where usually spare 105 mm rounds were stored. As the Skyranger turret intrudes very little in the hull, the commander station is located in the middle, behind the two operators in the front. A full refurbishment of the chassis in its automotive component will be necessary to increase reliability, mobility being increased by lowering the overall mass, as that of the Skyranger is around half that of the original tank turret, therefore saving some 5 tonnes compared to the MBT configuration, which means over 10%.
As for the SR30, this was fitted on a Boxer 8×8, in the German NNbS (Nah- und Nächstbereichsschutz) SHORAD/VSHORAD configuration, without missiles. Single and multiple drone targets were engaged, as well as static missiles and ground targets, according to range safety limitations.
Although not invited, Mr. Murphy was present at Ochsenboden; a COTS element, a gamepad used in the prototype that will not be part of the production Skyranger, failed to provide a safety signal due to a defective pin, not allowing the SR35 (which we heard firing in the morning during the briefing session) to operate. Being a temporary item, the fault could not be immediately detected by the on-board diagnostic.
Once identified, the system was replaced, and the test was successfully conducted the following morning in front of a good portion of the 26 delegations invited to the Swiss event.
Photos courtesy Rheinmetall and P. Valpolini
