Precision guided artillery munitions in future warfare

Sub Title : A brief history of development of PGMs, the advantages thereof and suggestions as to their induction

Issues Details : Vol 13 Issue 6 Jan/Feb 2020

Author : Maj PV Krishnan (Retd)

Page No. : 48

Category : Military Technology

: January 28, 2020

Future conflicts will be limited both in time and space. This coupled with enhanced battlefield transparency and decreasing tolerances for collateral damage make it necessary for the forces to have a suitable inventory of precision guided munitions (PGMs). The article details a brief history of development of PGMs, the advantages thereof and suggestions as to their induction

It is generally accepted that the nature of future conflicts, especially in the Indian sub-continent, are most likely to be short, intense, day & night operations, with all assets displaying enhanced mobility and fleeting exposure. The intention would be to deliver a preponderance of precision guided fire power, from as small a footprint as possible. Real time day & night battle transparency and the resultant enhanced threat to survivability would make it imperative for fire power assets to significantly elevate riposte efficiency, albeit with a smaller logistics tail, and be capable of achieving ‘lasting neutralisation’ or even ‘destruction’ of the targets, with appreciably smaller amounts of ammunition and in much faster time frames. All of the foregoing point to the need for precision guided munitions.

For more than five centuries, since the invention and advent of artillery, when a target was located, cannons were lined up, the muzzle was pointed in the general direction of its mark and the gunner fired away, dozens of rounds of ammunition, one after another, until the target was caught in the deluge. Throughout the centuries, new cannon munitions offered more power and longer range but rarely greater accuracy. That changed in 1975, when Martin Marietta developed the world’s first ‘Cannon Launched Guided Projectile’ (CLGP), a.k.a. Copperhead. Once fired, the Copperheads sprouted small flip-out wings and control fins and glided along the path of the laser, reflected from the intended target by a laser designator fired by the Observer, delivering warheads to its target with unrivaled accuracy. This method of guidance is called ‘Semi Active Command Line of Sight’ (SACLOS).

In early 1960s, another route was being explored to guide artillery projectiles onto intended target, without the need for an Observer to designate them. Project Sense and Destroy ARMor, or SADARM, is a United States ‘smart’ submunition capable of searching for, and destroying tanks within a given target area. The concept was initially demonstrated in the late 1970s with the 203 mm M509 ‘Improved Conventional Munitions’ ICM projectile, but by 1983 the project shifted focus to the 155 mm caliber. This ammunition proved to be less accurate than the Copperhead; pre-production samples tested in 1993 gave poor results with only nine out of 42 submunitions hitting their targets. Fixes were applied and further testing resulted in 11 hits from 13 submunitions, finally matching the hit-probability of CLGPs.

The SADARM shell, with an electronic time fuze, is fired from a normal 155 mm artillery gun, set to burst at 1,000 m above the target to release two SADARM submunitions. Once the submunition is ejected from the projectile, a parachute opens, to de-spin and slow the submunition. A second parachute then deploys, and as it spins, its sensors, comprising of a millimeter-wave radar, a passive millimeter-wave radiometer and an infrared telescope, sweep a decreasing spiral track beneath the submunition to scan an area about 150 m in diameter. When the submunition detects a target, its charge is detonated, to project an explosively formed penetrator that has enough energy to penetrate the thin top armour of most main battle tanks. If the submunition reaches the ground before it finds a target it self-destructs.

In the late 1990s, the Indian artillery too was looking at various options like the Russian Krasnopol and Swedish Bonus to increase its precision, lethality, effectiveness and efficiency. In pursuance of this objective, a Concept of Smart Munitions was evolved, as shown in Figure 1.

The Family of Smart Munitions can be divided into four categories, namely; Low Cost Competent Munitions (LCCMs), Sensor Fuzed Munitions (SFMs), Terminally Guided Munitions (TGMs) and Brilliant Munitions. These are explained in detail as below: –

  • LCCMs. With the advent of 155/52mm guns, it became possible to achieve a maximum range of about 42 Km. At such ranges, the spread of a base-bleed extended range shell would be about 400 metres, thus adversely degrading lethality. In the early 1990s after the first Gulf War, while Raytheon was working on the M982 Excalibur round, in the late 1990s Swedish Bofors, US Alliant Tech (ATK) and BAE Systems started working on much more cost-optimal yet nearly equally precise guidance mechanisms, collectively referred to as Guidance Integrated Fuzes (GIFs). The Swedes were working on a concept called Trajectory Correctible Munitions (TCMs), in which a radar at the gun end tracked the trajectory of a shell till its vertex, and an on-board GPS based navigation system compared instantaneous location defined by GPS, radar location and predicted data, and generated a correction matrix to bring the shell to the intended point of impact on its downward trajectory. ATK, BAE, Junghans Micro Tek (JMT), Thales, IAI of Israel and a few more countries were simultaneously working on similar projects in their respective countries, called Course Correction Fuzes (CCFs). Experiments have been explored in 1D and 2D CCFs. Today, a normal GPS-INS Excalibur or a similar round from Oto Melara-Diehl GmbH boasts of a CEP of about 10 metres (Figure 2), while a GPS-INS+Semi Active Laser System (SALS) round can achieve a CEP of less than 2 metres. In comparison, the latest ATK Precision Guidance Kit has a CEP of 10 metres. While a typical GPS+MEMS INS+SALS round costs about $50,000/-, a PGK costs about $10,000/-.
  • PGMs. While the US Army discontinued the development and induction of SADARM, since other types of ammunition which could achieve the same effect had emerged, Diehl GmbH inducted its ‘Submunition Modular Artillery (SMArt) round not only in the German Army, but with a few more customers around the world. The Swedes merged their TCM with the US Excalibur programme to realise three types of Excalibur munitions, namely; Unitary Penetrating Warhead Round, Extended Range GPS+INS round and a very precise GPS+MEMS INS+SALS round.
  • TGMs. The Indian Army purchased 3,000 rounds of the binary Krasnopol round. However, owing to various reasons, the plan to manufacture the ammunition indigenously and induct in large numbers, did not fructify. Even the Copperhead CLGP has not been a resounding success. It is this space that is being occupied by Oto Melara-Diehl GmbH’s Vulcano and Raytheon-BAE Systems AB’s Exclibur S Increment-1, both of which are a sort of ‘Next-Gen CLGP’.
  • Brilliant Munitions. Any munition capable of discriminating between potential targets in terms of inter-se priority, switching from one target to another after the first one has been designated, able to abort mission at the very last moment, and able to be recovered for subsequent use, was defined as ‘Brilliant Munitions’.

Loitering Munitions (LMs) first emerged in the 1982 Lebanon War (OP DRUGSTORE), where Israeli DELILAH and HARPY UAVs were used for reconnaissance, as decoys and as anti-radar munitions against Syrian SAM sites in Lebanon’s Bekaa Valley. In late 1990s, when TGMs and PGMs were on the verge of being introduced into military service and LCCMs were maturing at a rapid rate, major developments such as in improved sensor technology, electric propulsion, composite airframe, etc., meant drones got smaller to the point where they could be carried and launched by individual soldiers. The United States fielded AeroVironment’s “Switchblade” in 2012 which was used in Afghanistan against “high value targets. While limited in endurance, the Switchblade could loiter over the battlefield if the target was not immediately visible after launch.

In this role, the loitering munition is seen to provide to a small unit leader, a more precise alternative to guided artillery and traditional drones. Loitering munitions are cheaper than dedicated missiles fired from HALE/MALE drones and have faster “response” times, being able to be launched by soldiers on the ground. Being directly guided by cameras on board, they are far more accurate than guided artillery, landing within meters of a target compared to tens of meters for a laser guided artillery shell. Given their low radar, visual, and thermal signatures, loitering munitions are very hard to track and kill. Success on a future battlefield may very well be determined by which side can use loitering munitions to the greatest effect.

While all these developments augur well for the future as far as precision engagements are concerned, this also leaves us with the proverbial oxymoron of “Problems of Plenty”. The question has to be addressed in two parts; i.e., one of LCCMs, PGMs and TGMs, and a wholly separate issue of LMs.

Consider that a 155mm gun has a 1st Line Scale of 90 rounds, of which a certain number of rounds are electronic time fuzed carrier shells like smoke, illuminating & DPICM, and the balance are plain HE. Of these HE rounds, a certain percentage are fuzed with PD with Delay, and a small number with Proximity Fuzes. It is nobody’s case that the entire 1st line HE rounds should comprise of precision guided ammunition of one type or the other. Not only is that economically unviable and unwise; it is not even tactically desirable. There are more tactical contingencies which need old fashioned suppression and immediate neutralisation, than destruction delivered by a single round. Given the cost-to-benefit-ratio, there is a case to have a larger number of LCCMs per gun, and somewhat lesser number of PGMs/ TGMs. What these actual numbers should be, or could be, is beyond the ambit of this discussion.

LMs pose a completely different set of questions. Should they be distinct and separate artillery units, replacing conventional gun and rocket units? Is there a need to consider a dedicated network of command and control, from gathering of real time actionable intelligence on high value and fleeting targets, till the decision of executing a fire assault? If LMs proliferate to all arms like Infantry, Mechanised Infantry and Armour, how will the firepower emanating from different arms be coordinated?

Given the fact that a medium gun has about 90 – 100 rounds as combat scale presently, while the transition to PGMs or Smart munitions is underway, a pragmatic approach would be to have 60-70 rounds of dumb munitions (HE / Smoke / Illuminating with PD / Proximity / Electronic Fuzes) and balance 25 rounds comprising of  LCCM / DPICM / TGM / PGM. The number of non precise / unguided munitions can be scaled down further as PGMs will have assured hits on targets, thereby further reducing the overall combat scales of ammunition per gun. This will also have corresponding effects on logistics and balance out the costs.

As far as LMs are concerned, it is perhaps the simplest to start with Special Forces, who could be scaled a mix of light and medium LMs to substitute their rocket launchers and ATGMs. Mechanised Infantry and Armour could consider using medium LMs as a turret mounted additional weapon to their existing inventory, which gives them not only ability to target selectively, re-target and abort the mission when required, but also gives them ISTAR capabilities. As far as long endurance LMs are concerned, these lie in the domain of artillery. It would be prudent to commence by inducting at Artillery Division level, a battery of six launchers, each with multiple pods, and employ the weapon as a strategic asset. Though there is a school of thought suggesting replacing conventional rocket launchers with long endurance LMs, it may be prudent to take one step at a time, before completely substituting LMs for GRAD BM-21/ PINAKA/ SMERCH MBRLs.

Whether it is the induction of classical guided munitions like LCCMs/ PGMs/ TGMs or that of the newly emerging and exciting technology of LMs, there is a need to study the magnifier and force multiplier effects by conduct of Red-Blue war gaming, followed by some limited exercises with troops, before we can evolve a cogent and conclusive policy in its scaling, stocking and employment.