Mobile Mortars to Shoot and Scoot.

Mortar gunners are very aware that the modern battlefield is a dangerous place, especially where their combat activities are concerned. Thanks largely to modern mortar location radars, mortar firing positions can be discovered well before their first bombs are delivered on target. Once a mortar location is known, retaliation from the opposition will soon follow. If mortars and their operators are to survive on modern battlefields they have to acquire two major tactical assets -- mobility and protection.

Conventional mortar teams usually have to carry their weapons, fire control equipment, communications and ammunition on their backs. Their mobility, considering the weights and volumes involved, is thus limited, even with light mortars. In addition, firepower potential is restricted to the number of bombs a team can carry. Light and special forces have to accept these limitations, for the fire support that infantry mortars can provide would not otherwise be made available. So, whatever transpires, well-laden infantry mortar teams will continue to operate.

Simply carrying mortars and their teams in soft-skin vehicles can bestow a measure of mobility, plus the capability to carry more ammunition and other supplies, but the vulnerability factor remains high. The best solution, when it can be achieved, is to carry mortars in some form of armoured vehicle, thereby obtaining both mobility and protection.

Numerous examples of APC-based mortar carriers can be found, usually with 81.4 or 82 mm mortars so arranged that they fire through opened roof hatches over what was originally the troop compartment. Numerous bombs can be carried in racks around the vehicle, so a considerable number of fire missions can be carried out before re-supply becomes necessary. This reasoning inexorably leads us to higher efficiency, and therefore to larger calibres.

Changes

Indeed, a major change is coming with the increasing acceptance and adoption of larger calibre mortars, usually 120 mm. The advantages of larger mortar calibres, and 120 mm in particular, are many, with range and payload capacity high on the list, yet their size and weight when on field carriages constricts their mobility and time in and out of action.

A standard 120 mm mortar has a maximum range well in excess of that from 81.4/82 mm mortars, while the internal volume of a 120 mm bomb is sufficient not only for a much larger high explosive payload, but for many other alternatives as well, including dual-purpose bomblets. In addition, 120 mm illuminating bomb contents can be brighter and remain alight for longer, while smoke screens can be rendered more opaque, longer-lasting, and even multi-spectral to provide cover from surveillance devices. The advantages of the 120 mm mortar are such that some armies regard them as artillery assets rather than as infantry weapons.

The coming of the guided mortar bomb is a further reason why the 120 mm calibre is becoming increasingly attractive (while smaller calibres could also be guided, the costs involved in relation to their necessarily lesser warhead capabilities have tended to make them impractical -- remember the defunct Merlin?). At present, there is only one fully autonomous round in service, the Swedish Saab Bofors Dynamics-Bofors Defence Strix. To date, the Strix seems to have been deployed only with field rather than mobile mountings, but tests have been made in conjunction with the AMS and the Amos, and studies have been carried out in the recent past for a specific potential customer with a view to fitting the Strix with slip rings that would have enabled it to be fired from French rifled barrels. The Strix, adopted by Switzerland, has a maximum range of 7500 metres and, as we shall see, can be fired from the Swiss Bighorn. However, the Strix might well have to undergo further development if its potential market is to widen. It was indeed developed at a time when large concentrations of tanks would have had to be dealt with. Now a higher precision is required and Saab Bofors Dynamics is looking for partners to achieve this, perhaps through the use of GPS and of a more advanced seeker that would, inter alia, allow target identification

Well advanced is the Russian Gran (Facet) 120 mm laser-guided projectile from the KBP Instrument Design Bureau at Tula. It relies on laser guidance in much the same way as gun-delivered guided projectiles like the American Copperhead and the Russian 152/155 mm Krasnopol: a forward-located laser target indicator illuminates the target onto which the Gran will home, thanks to its nose-mounted sensor canard surfaces.

The Lockheed Martin/Diehl 120 mm Precision-Guided Mortar Munition (PGMM) XM935 is under development to be fired from the US Army's M120/M121 120mm mortar system (the M121 is the version used on the self-propelled platform, the M1064 based on the M113 APC), although it can be fired from any other 120 mm smoothbore mortar. The PGMM is intended to be operated using one of two modes, the first being the laser target illumination technique as employed by the Russian Gran. Another option is an entirely autonomous mode employing infrared target detection along the same lines as the Swedish Strix. The PGMM is still at the advanced development stage, with an intended maximum range of 15 000 metres. One further requirement is that each round should cost under $ 20 000!

One further prospect would have been the French TDA 120 Aced projectile. Unfortunately, the project was shelved by the French DGA procurement agency. It was designed as a cargo bomb carrying two top-attack anti-armour Aceds, themselves shrunk versions of the millimetric and infrared-sensor 155 mm warheads that had been developed during a competitive programme which was eventually won by the infrared-only Saab Bofors-Giat Bonus. Aerospatiale Matra, however, has recently introduced yet another French alternative to guided bombs. Named Alfo and still under study, these would be guided to the target by optical fibre link.

Turrets 

To fire mortars from armoured turrets means that they have to be breech-loaded. This is no novelty, as TDA of France has long manufactured a range of 60 and 81.4 mm breech-loaded mortars for light armoured vehicle turrets. These are essentially direct fire, close range, self-support weapons. Turret-mounted 120 mm breech-loaders are a different proposition but present few technical challenges.

The challenges have been met in several ways. One can be seen with the joint venture between Delco Defense Systems and BAE Systems' RO Defence. Known as the Armoured Mortar System (AMS), this involves a single smoothbore 120 mm mortar barrel in a light, fully revolving armoured steel turret. The mortar's origins date back to 1985, even though the full AMS project started much later, resulting in an order for 73 AMS turrets to be mounted on General Motors Light Armored Vehicle (LAV) wheeled APCs for the Saudi Arabian National Guard.

The AMS turret arrangement allows short into-action times while the 8 x 8 chassis provides rapid departures. Another advantage is that the mortar can be fired in the direct fire mode against other vehicles or hard targets, the on-target effects being equivalent to 122 or even 155 mm artillery projectiles. In the more usual indirect fire mode the maximum range has been demonstrated up to 9000 metres.

Although the AMS turret has been selected for the LAV chassis there is no reason why it could not be accommodated on other vehicles. A stretched Ml13 APC is one possible application and there could be many others. This is typical of most 120 mm mortar turrets, as demonstrated by another example, the Finnish Hagglunds/Patria Vammas Amos (Advanced Mortar System).

The Amos turret sports two three-metre long, 120 mm smoothbore barrels on a common cradle, each with its own recoil system so that single barrel only firing can be employed, if required. As with the AMS, a barrel-mounted fume extractor keeps firing gasses out of the turret. Maximum range is up to a considerable 13 000 metres and, as the Amos has been designed to meet a common Scandinavian requirement, the guided Strix is almost certain to eventually complete the picture.

The Amos has considerable `stretch' potential. An auto-loading system could increase the current firing rate of up to 24 rds/min, while advanced digital fire control systems and turret drives could further enhance accuracy and reduce the time needed to lay the barrels on target. To date the Amos has been demonstrated mounted on the Hagglunds Vehicle CV90 tracked chassis and the Patria Vehicles XA-185 6 x 6 APC chassis. Other carriers in prospect could include the Patria Vehicles XA-203 6 x 6 for the Finnish Army, and the Russian BMP-3 IFV. An attempt to mount the Amos on a Russian MT-LB tracked carrier chassis was deemed unsuccessful.

Russia

As usual, the Russians have gone their own way. Their approach has been to develop what they term gun-mortar systems employing a single rifled barrel.

Two separate Russian solutions have emerged. One of which is the 2S31 Vena, with a fully enclosed turret on a modified BMP-3 IFV chassis. Its projectiles bear little resemblance to conventional mortar munitions, while the single 2A80 barrel can fire a variety of projectiles, including cargo rounds. The maximum range for a 120 mm HE projectile from the Vena system is about 18 000 metres.

The second is the 2S23 Nona-SVK, based on a modified, wheeled BTR-80 8 x 8 APC chassis. Here the 2A60 rifled barrel fires more conventional 120 mm rifled mortar projectiles, including those of French TDA origin, although one oddity is an anti-armour Heat projectile intended to be delivered when using the turret's direct fire capability. Maximum range firing a rocket-assisted high-explosive bomb is 12 850 metres. It has been reported that a batch of 100 Nona-SVKs have been sold to China.

Neither of these gun-mortar systems can fire the laser-guided Gran, as the Gran is intended to be launched from smoothbore mortars.

Through the Hatch

Serious alternatives to the necessarily expensive and technically challenging turret-mounted mortars are being developed by TDA with the rifled 120 mm 2R2M 120, Ruag Land Systems (formerly SW) with the Bighorn and Soltam with the Cardom. Those mortars have to fire through the open hatches of the vehicle's roof and, unlike their turreted counterparts cannot, therefore, perform direct fire. On the other hand, they do not require heavy vehicle modifications or the development of a specific turret. They also tend to be self-contained, meaning that they are relatively easy to install, generally just requiring a power supply.

The French TDA 2R2M 120 mm rifled mortar has several futuristic applications and has been demonstrated both from the wheeled Mowag Piranha 8 x 8 and the United Defense M113.

At first sight the proposed open-topped installation resembles that of many existing mortar carriers, the difference being that the 2R2M mortar is intended to be pointed remotely and loaded automatically. On-board fire control systems are able to determine the target and the firing position coordinates, make the necessary firing calculations and lay the barrel accordingly, the crew merely monitoring matters.

TDA has developed the possibilities of this system to a stage known as the Dragonfire. For this the 2R2M mortar is towed or dropped into a firing position and left, the idea being that it could be remotely controlled. Firing trials with the US Marine Corps undertaken in January and again in March 2000 and are said to have caused quite an impression, particularly with regards to range and accuracy. Strangely, the US Marine Corps also requested a `standard' LAV-mounted 2R2M for high-level military exercises involving thirteen km-range HE and illuminating rounds as well as French smoothbore rounds (apparently US officers were totally bemused by the fact that use of old-stock smoothbore ammunition with the rifled 120 mm was common practice in the French Army for training purposes).

According to TDA, and as these lines are being written, tests should start to demonstrate that off-the-shelf US Army smooth-bore mortar rounds are indeed compatible with the rifled mortar of the 2R2M and thereby confirm full interoperability of the weapon. The 2R2M was personally fired by a high-ranking US Army officer during a visit to France. The system will be presented on 12 and 13 June, 2001 at the Ft. Benning Infantry Conference. Also of particular interest is the 17 km range achieved by the Rap-VLR round. TDA is also preparing to launch a new cargo round into production for a foreign customer in 2002. Little is know for the time being on the type of grenades carried, but the French DGA is said to be planning an evaluation campaign that could lead to a French Army order around 2003 or 2004. TDA told Armada that semi-active laser guidance like the Russian Gran was being investigated.

Ruag Land Systems entered the vehicle-carried mortar scene a little later; this was in 1997 when the Swiss Army launched a tender for proposals. The programme was put on ice a year later, but the, at the time SW, factory recognised export potential and carried on with the development. There are now two running prototypes of the Bighorn, as it is called. The Bighorn is fully self-contained and boasts a bolt-on/off smoothbore design. It only requires a 24 Volt supply, carries its own batteries in case of a power failure yet still has a hand-activated pump back-up system, in the event of a total electrical supply failure. The semi-automatic loader does not clamp the rounds, but rather has a cradle carrier that slides the round up to the muzzle without damaging the softer skins of some cargo rounds. The firing pin can be triggered manually or automatically and the breech can be opened to extract faulty rounds and facilitate maintenance. The inertial reference unit (currently a Kearfott Napos, but another laser gyro-based system could be used) is actually bolted onto the trunnion, in line with the barrel axis, ready to assist fast barrel positioning and ensuring a rapid reaction to fire orders. When all parameters have been entered, a screen on the control panel displays a reticule and a symbol that the gunner simply needs to place onto the bull's eye position with the joystick to complete the laying of the system. A fully automatic laying system would be possible, but according to Ruag, the costs involved would be out of proportion with the simple and quick manual operation (as tested by one of the authors).

The Bighorn has a recoil system that considerably reduces the stresses imposed by firing when using relatively light carrier chassis. The maximum recoil forces produced when using the maximum charges (approximately 484 kN) are dampened by 70 per cent compared to conventional systems, so the scope of carrier choices is much enlarged. In fact, all early tests where performed from a simple 6 x 6 lorry and, according to Ruag, the weapon can be mounted on any chassis capable of carrying a load of 1.5 tonnes, like a humble Duro for example. However, since the actual scope is to see it in armoured vehicles, it has been fired from an M113. Installations on an FNSS, and other exotic tracked armoured vehicles, are expected to take place very soon. The semi-automatic loader can permit a burst firing rate of four rounds in 20 seconds. The Bighorn is of course compatible with all available 120 mm ammunition, and that includes the Strix mentioned above (but in that case has to be loaded manually). Finally, the Bighorn can be had with an insert to enable it to fire 81 mm rounds, a useful feature for training or if a smooth transition to the larger calibre has to be made by using up an existing stock of rounds.

Soltam Defence has a similar autonomous system known as the 120 mm Computered Automatic Recoil Mortar System, or Cardom, involving a Soltam 120 mm mortar on a special turntable mounting in the back of an M113. The recoil system adjusts automatically to allow a full 360 [degrees] barrel traverse from within the APC interior, while laying operations are carried out by computer control. The response from such a system can be very rapid, although an autoloader or other under-cover loading method has yet to be introduced. No doubt one is on the way.

Wiesel 2

The Rheinmetall Landsysteme Wiesel 2 provides yet another example of one possible future design approach to the mobile mortar. Unlike the other systems mentioned above, the MaK Wiesel 2, a `stretched' version of the earlier Wiesel model, was developed specifically as a lightly armoured air-transportable vehicle for rapid reaction and airborne forces. It is thus small and light, the combat weight of the basic chassis being just over four tonnes.

The installation of a 120 mm mortar on such a light chassis has therefore resulted in a novel design approach. The mortar is carried over the top of the hull and lowered to the ground from the back of the hull for firing. Recoil stresses are reduced by a soft recoil system, together with stabilisers lowered to the ground, one either side of the vehicle. The Wiesel 2 installation involves muzzle loading, although this is carried out from within the vehicle's protection. To achieve this, the barrel is tilted to a horizontal position, loaded and then brought back to its firing position. An on-board fire control system allows fire missions to be conducted rapidly. The first customer will probably be the German Army

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In short

* "Mobility means `vehicle', which in turn means that the systems can be heavier, boasting larger calibres"

* "Smaller and lighter man-portable mortars would thus tend to be restricted to commando or special forces missions"

* "The battle between the turret-mounted and plalform-mounted mortars appears to be a pure marketing war, as the two types have different missions and operating costs."