When mortars roll in ...

The universally deployed mortar is currently undergoing a period of reassessment. While light, handy and readily portable 60 mm mortars are to be retained by special and airborne forces for the foreseeable future, the 81/82 mm mortar is fading from fashion. The warhead delivery and range advantages of heavier-calibre mortars, 120 mm predominating, are such that they are being widely adapted at the expense of the 81/82 mm equivalents.

Heavy mortars are exactly that--heavy. When deployed as infantry weapons in the field they can be awkward and cumbersome loads that take time to get in and out of action. The 'get away' manoeuvre is important in these days of mortar locating radars when firing a mortar is certain to attract rapid retaliation from the enemy.

The solution is to make heavy mortars more mobile by coupling them with vehicle platforms to become self-propelled mortars (SPM). Most armoured fighting vehicles can be used as the basis for an SPM system, although platforms can vary from barely altered truck chassis to specialised tracked armoured vehicles; the latter are beginning to predominate within many armed force inventories. One important aspect of this mobility potential is how the mortars should be installed on their carrier chassis. Should mortars be installed within the hull, firing through roof hatches or mounted in traversing turrets?

For/Against

At first sight the advantages of the turret-mounted mortar would seem to outweigh those of the open roof hatch approach. As the mortar installation can be fully enclosed by armour, the crew will be protected from shell bursts and small arms fire. They will also have protection against nuclear, biological and chemical (NBC) warfare attacks. Mortar crews operating from open-topped vehicles (usually modified armoured personnel carriers) do not share these two major assets.

More turret advantages emerge when fire control is considered. Large barrel traverses can be introduced rapidly, especially when computer-based fire control systems become involved. The barrel can also have a direct-fire capability, a feature totally lacking with the open-topped carrier option. Direct fire from a mortar tube may be effectively utilised against a wide array of targets, from structures to vehicles. Any strike from a 120 mm mortar bomb, delivered directly or indirectly, will disable any truck or light armoured vehicle.

Yet the turreted mortar also has some convoluted features. Breech loading mechanisms have to be introduced, as do recoil mechanisms. By contrast, open-topped carriers do not demand such complications, complications that not only add complexity but also weight and unit cost. In an era of rapid deployments by air, any weight additions have to be avoided wherever possible, one of the main reasons why the open-topped carrier approach can be preferred.

Another important consideration in favour of open-topped carriers is that a conventional baseplate and field mounting can also be carried and brought into action should the carrier vehicle become disabled or should the operational situation demand dismounted deployment. Another positive factor for the open-topped carrier is that it can be readily concealed within formations of other similar carriers. By contrast, any turret-mounted mortar is more obvious and may be marked out for special attention by an enemy. Finally, the number of potentially available platforms for turreted mortars versus the base-plate type is a factor of three to eight.

Turrets

To date it has to be stated that the open-topped option is the one that prevails numerically yet there are several turreted mortars on the market.

One of the first turret mounted mortar systems to be developed was the 120 mm armoured Mortar System (AMS) designed by BAE Systems, RO Defence, and Delco Systems (now part of General Dynamics Land Systems). The former concern is responsible for the turret and smooth bored weapon, while the latter company deals with the computerised fire control system and sights.

Ammunition for the 120 mm AMS has been developed and manufactured by the Belgian Mecar concern. The AMS has also been tested with the Swedish Bofors Defence/Saab Bofors Dynamics 120 mm Strix precision guided munition and the Ruag Land Systems 120mm mortar cargo bomb carrying 32 submunitions, each with a Heat warhead.

The first customer for the 120 mm AMS was the Saudi Arabian National Guard, who ordered a total of 73 systems as part of its contract with General Motors Defense of Canada for 1117 Light Armored Vehicles (Lav). The 120 mm AMS has also been installed on other chassis for trial purposes, including the United Defense M113A2 APC, Mobile Tactical Vehicle Light and Saudi Arabian Abdallah Al-Faris Al Fahd AF-40-8-1 8 x 8 APC.

RO Defence and Delco Systems are now working on a Next Generation Turret (NGT) that will feature a number of innovations, including all-electric turret drive and weapon elevation systems and a new fire control computer.

In 1996, the now Alvis Hagglunds of Sweden and Patria of Finland signed an agreement to develop a turret-mounted twin 120 mm mortar system designated Amos (Advanced MOrtar System). Within this consortium, Alvis Hagglunds is responsible for the turret and Patria for the twin 120 mm smoothbore mortars.

Although developed as a private venture, the Amos subsequently received funding from Finland and Sweden. The system has already been integrated with a Patria XA-203 (6 x 6) APC for extensive trials with the Finish Defence Force. The latter is expected to install production turrets on its new Armoured Modular Vehicle (AMV-recently selected by Poland). The Amos has also been installed on an Alvis Hagglunds CV90 series fully tracked chassis and Sweden is expected to order 50 to 70 systems (funding permitting--the chassis are already being built by Alvis Hagglunds). The current Amos PT1 turret weighs 5800 kg but production versions would depend on the armour protection level and whether an ammunition-handling unit was installed, thus the weight of the lightest Amos turret is 3300 kg. Range depends on the type of mortar bomb, but firing a Patria 120VAM15.00 bomb, a maximum range of 10,000 metres can be achieved. Various fire control options are being marketed.

In June of 2002, Patria Hagglunds received an order from the Swedish Defence Materiel Administration (FMV) for a study concerning the integration of the Amos on a combat boat produced by Dockstavarvet, and the subsequent production of the first integrated test combat boat.

In the late 1980s the ZTS company, located in what is now Slovakia, developed the 120 mm Pram-S system based on a stretched and modified BMP-2 armoured personnel carrier chassis, then being produced under licence. The Pramm-S is fitted with a 120 mm breech loaded mortar that can be aimed, loaded and fired under armoured protection. Maximum range is just over 8000 metres, with the maximum rate of fire being 18 to 20 rounds per minute. A total of 80 rounds of 120 mm mortar ammunition are carried, of which 21 are in the ammunition conveyor system and 59 in the magazines. Only twelve production Prams-S systems were built.

The Russian Army has long deployed a number of self-propelled gun/mortar systems originally developed for issue to its Air Assault Divisions. The first of these, the 120 mm Anona 2S9 saw extensive use in Afghanistan. The 2S9 is based on a modified BMD-1 airborne combat vehicle chassis having a turret armed with a 120 mm breech loaded gun designated the 2A51. Ammunition is loaded manually, with a rammer to assist in loading, especially at high elevations. Turret traverse is 35[degrees] left and right and the high elevation capability of +80[degrees] proved very useful in the mountainous terrain prevalent in Afghanistan.

Ammunition fired by the 2S9 includes HE, white phosphorus and smoke. The standard HE bomb has a maximum range of 8855 metres while a rocket assisted bomb reaches 13,000 metres.

Russia subsequently developed the Nona-SVK 2S23 based on the chassis of the widely deployed BTR-80 (8 x 8), which provides extended strategic mobility potential as it is wheeled. It is understood that this system has not been produced in significant numbers.

The latest self-propelled mortar developed by Russia is the 120 mm 2S31 Vena based on a much-modified BMP-3 infantry fighting vehicle chassis originally developed by the Kurgan Machine Construction Plant. The Motovilikha Plants Corporation was responsible for turret and systems integration.

The 2S31 Vena has a fully enclosed turret armed with a 120 mm rifled barrel that can be elevated to +80[degrees].An on-board automatic survey and orientation system is installed and optics include a day/night image intensification sight incorporating a laser rangefinder. It is capable of direct and indirect fire and can deliver an HE projectile to a maximum range of 18,000 metres. Also available is a cargo round carrying 35 submunitions. 70 mortar bombs are carried, 22 of them in ready-use magazines. The maximum rate of fire is quoted as eight to ten rounds a minute. The mortar can also fire the KBP Instrument Design Bureau 120 mm Kitolov-2M laser-guided projectile with a maximum range of 13,000 to 14,000 metres. Targets for this projectile can be designated from the Vena turret or a remote ground-mounted designator.

Norinco (China North Industries Corporation) has developed and is offering for export a 120 mm turret-mounted mortar system based on the WZ 551 (6 x 6) armoured personnel carrier, currently deployed in large numbers by the PLA. There have been reports that Russia supplied at least some of the technology used in the development of this system. It has a long rifled barrel similar to that used on the Russian 120 mm 2S31 Vena. According to Norinco, the mortar has a maximum range of 8500 metres firing a standard bomb, or 9500 metres with a special HE projectile. A semi-automatic loading system is provided. The complete system weighs 16.5 tonnes and it is fully amphibious.

The above covers the main types of turreted mortar currently available. The future looks bright for at least two of them as the US Army has a requirement for a Non-Line Of Sight--Mortar (Nlos-M) to be part of its Future Combat Systems programme. The two systems short-listed to meet this requirement are the Patria Hagglunds twin-barrelled 120 mm Amos and the BAE Systems, RO Defence/ Delco Systems 120 mm AMS.

Open Hatches

Continuing the US Army theme, the service has replaced its old self-propelled mortars with the 120 mm M120/M121 Battalion Mortar System (BMS). The BMS is a two-part system; with the M121 carrier-mounted version using the M1064 platform based on the M113, the ground-based version being the M120. The actual mortar is an Israeli Soltam 120 mm smoothbore design having a maximum range of 7200 metres with an HE bomb. The development of the XM395 Guided Mortar Munition for the 120 mm BMS has been underway by Lockheed Martin and Diehl for some years. A new mortar fire control system will also be introduced.

The US Marine Corps continues to use the Improved M252 81 mm mortar on its LAV 8 x 8s, offering a maximum range of 5700 metres with an M889 bomb. There is also a mortar carrier version of the US Army's Stryker.

In France, TDA has been developing and manufacturing mortars for many years, its 120 mm MO-120-RT rifled mortar having been sold to over 20 countries. This is normally towed by a truck or wheeled armoured vehicle. TDA subsequently developed the 120 mm TDA 2R2M system as a private venture. This TDA system has since been integrated into a number of chassis, tracked and wheeled, as well as being used for the US Marine Corps Box Mortar concept which calls for a remotely controlled and fired 120 mm mortar. The remote function is greatly assisted by the 2R2Mr, which has an automatic muzzle-loading system.

When the 120 mm 2R2M is retracted under armour protection in the hull an enemy cannot tell if it is a self-propelled mortar or a normal armoured personnel carrier. The rifled mortar and its associated hydraulic recoiling system are mounted on a turntable, allowing it to be rapidly traversed through 360[degrees] with a joystick, which is also used for elevation. The modular design incorporates a loading system that carries the bomb all the way up to the muzzle and drops it into the barrel. A location and positioning system (incorporating GPS and a land navigation system) can be added to the fire control system.

The mortar itself is ballistically identical to the standard 120 mm MO-120-RT towed system and fires the same ammunition family. Its maximum range using standard ammunition is 8135 metres. When firing a rocket-assisted projectile the maximum possible range is increased to 13,000 metres.

Soltam is the leading artillery and mortar developer and manufacturer in Israel and currently markets a wide range of mortar systems and ammunition. One of the latest offerings is the 120 mm autonomous mortar for self-propelled applications known as the Cardom, which has been tested in a number of tracked and wheeled armoured personnel carrier chassis. The Cardom integrates a Soltam Systems 120 mm mortar with navigation, self-positioning and ballistic and fire control systems. The recoil system consists of a hydro-pneumatic recuperator located beneath the cradle housing. This system is so arranged that it attenuates the firing loads,, especially on wheeled vehicles. Maximum range is quoted as 7200 metres and it can be ready to fire within 45 seconds of coming to a halt.

Ruag Land Systems of Switzerland has developed the Bighorn 120 mm recoiling mortar system for installation in tracked and wheeled vehicles. Like the French 2R2M, this has a semi-automatic loader to provide a high rate of fire. The Bighorn, laid by actuating a joystick, is also fitted with on-board navigation, positioning and computing, combined with integrated hydraulics and electric power. The Bighorn can fire a burst of four rounds in less than 20 seconds and is capable of a sustained rate of fire of twelve rounds per minute. Using a 'hatched' vehicle, the Bighorn can stop and be in firing position (~30 seconds), fire its twelve rounds (~one minute) and be on the move again in approximately two minutes.

Singapore Technologies Kinetics (STK) is developing the 120 mm Super Rapid Advanced Mortar System (120 Srams) for installation in tracked and wheeled armoured vehicles. The Srams is claimed to have a high rate of fire as it is fitted with a semi-automatic ammunition transfer system and a patented valve system in the breech mechanism. This is to allow the bomb to drop faster down the barrel. It also has special barrel cooling arrangements. The Srams maximum range with standard ammunition is 9000 metres, or out to 13,000 metres with assisted ammunition. The system is also integrated with an automatic fire control system that enables it to perform autonomous fire missions.

For many years the standard German Army self-propelled mortar has been a 120 mm smooth bore mortar mounted in the rear of a modified M113, although this combination lacks the mobility to operate with the Marder 1 infantry fighting vehicle.

Some years ago, Rheinmetall Land Systems developed, as a private venture, a 120 mm system based on the Wiesel (Weasel) light carrier chassis. It was subsequently demonstrated to the Germany Army but the initial response was lukewarm. This changed during 2002 when the company was awarded a contract for two pre-production systems based on the elongated Wiesel 2 chassis. Strictly speaking, the Wiesel 2 Light Armoured Mortar Carrier, as it is known, is not an 'open hatch' design as the mortar is located over the hull rear. Before the systsem comes into action a stabiliser is lowered on either side of the hull at the rear. The barrel, which is then still horizontal, is fed by the loader though the muzzle; it is then raised to the required elevation and triggered. The mortar is aimed, loaded and fired from within the three-man crew compartment (commander, loader and driver), which also houses the total of 30 bombs all under complete protection. The current German Army requirement is for up to 96 Wiesel 2 Light Armoured Mortar Carriers.

The Development of a new German IFV is now being undertaken by Projekt System & Management (PSM). It can be anticipated that a 120 mm SPM version will be developed, possibly incorporating a foreign turret.