Dramatic advances made in smart munitions in recent years, with US leading the way
Atul Chandra
It is now more than three decades since the US army first used laser-guided artillery munitions in combat. This was during the 1991 Gulf War, when the US army used Copperhead artillery rounds, which were the first cannon-fired smart munitions of their kind. These rounds were used to destroy observation towers being used to direct the planting of land mines around allied positions.
The use of such smart munitions brought about the first major change in how artillery was used in over 500 years. Until then the cannon was largely pointed towards the target and in the centuries that followed, such weapons offered more power and longer range but rarely greater accuracy.
It was the erstwhile American defence firm, Martin Marietta which developed the world’s first cannon-launched guided projectile, nicknamed the Copperhead in 1975. Developing such laser-guided artillery munitions was challenging to say the least, the Copperhead artillery shell featured sensitive electronics that had to be hardened to withstand the force of being blasted out of a cannon, a jolt approximately 8,000 times the force of gravity.
Smart Shell
Over the preceding decades, more advanced versions of precision artillery shells have been inducted into every modern military. But they are an expensive addition to the military inventory, both in terms of procurement and storage and maintenance.
Such munitions can quickly become unaffordable as evidenced by the Lockheed Martin-developed 155mm precision round, dubbed the Long-Range Land Attack Projectile (LRLAP), which was designed for the US Marine Corps and would have revolutionised naval firepower. The LRLAP would have the ability to hit land targets from up to 74 nm away. The LRLAP system featured munitions guided by a Global Positioning System (GPS) and Inertial Navigation System (INS) and at that time it was the most accurate and longest-range guided projectile in US naval history.
The LRLAP was to be fired from the US Navy’s Zumwalt Class warship’s 155mm Advanced Gun Systems. But when the number of warships to be procured was cut to only three, the cost of an individual LRLAP round shot up to nearly a million dollars per round. In comparison, a Tomahawk land attack missile with a range of 1,000 nautical miles also cost approximately USD 1 million (as per 2016 data). The LRLAP programme was cancelled in 2016.
Despite programme failures such as the US LRLAP, the US has proceeded with other Terminally Guided Munition (TGM) programmes such as the Excalibur, which is the US Army’s next-generation cannon artillery precision munition and manufactured by Raytheon Missiles & Defence. The importance of such munitions and the battlefield asymmetry that they provide has been on display during the ongoing Russia-Ukraine conflict.
In July, the United States government announced the supply of something the US had previously not sent to Ukraine: 1,000 rounds of 155 mm artillery shells able to strike targets with greater precision. “This is a new type [of] 155mm artillery ammunition,” a senior US defence official said, “has greater precision. It offers Ukraine precise… capability for specific targets. It will save ammunition. It will be more effective due to the precision. It’s a further evolution in our support for Ukraine in this battle in the Donbas.” These precision rounds being supplied to the Ukraine are something the US military already uses and has in its own stock.
Developing capability
Delivering on cutting-edge artillery capability is not an easy affair. The US army’s Picatinny Arsenal develops about 90 per cent of the lethality within the army and a high percentage for other services as well. As the US military’s Joint Centre of Excellence for Guns and Ammunition, Picatinny Arsenal has 63 munitions laboratories and over 3,000 army scientists and engineers who test and develop everything, from propellants and explosives to pyrotechnics and munitions. Among the recent developments in smart ammunition is the Precision Guidance Kit (PGK).
The addition of a PGK to a 155mm artillery shell is essentially the addition of a GPS-guided fuse that is screwed into the fuse well of the shell in place of the conventional fuse. This gives the projectile near-precision capability. According to the US army, near-precision accuracy for an artillery shell means it has a Circular Error Probable (CEP) of less than 50 meters at a range of 30 km. In comparison, a conventional 155mm projectile would be CEP accurate to about 267 metres for the same range. The PGK’s CEP advantage becomes even greater at shorter ranges, when it can deliver a CEP advantage that is about twice that of a non-PGK projectile when fired out to a range of 15km.
The PGK features fins or canards on the fuse to orient themselves to the target using GPS. The added advantage of such guidance kits is that they cost only a fraction of the cost of a typical guided munition. The additional cost of a PGK-equipped artillery shell over a conventional artillery shell is also largely nullified by the fewer shells required to defeat a target. This could be up to 60-70 per cent lower and the need to carry fewer artillery rounds into a combat zone also leads to a significant reduction in logistical requirements.
The US army was quick to realise the PGK’s battlefield changing nature and decided on their deliveries to US forces in Afghanistan. Australia and Canada are also potential Foreign Military Sales (FMS) candidates. It is hoped that India also joins this list.
Battlefield Differentiator
Long-range precision guided munitions are a prized capability for many modern militaries but out of reach for nearly all of them. The US army, which has a stated aspiration to field systems capable of accurately firing at targets 100 km away before the end of the decade, is the leader in this arena. Currently its 155mm artillery projectiles can typically engage targets no more than about 30 km away.
As a result, the US army’s Extended Range Cannon Artillery (ERCA) programme has developed the XM1113 projectile. It exceeded a range of 60 km during testing in 2018. The XM1113 projectile is a traditional artillery round but is assisted by a rocket to achieve greater ranges. The XM1113 features a much-larger rocket, which pushes out more than twice as much thrust as the legacy system. The XM1113 is also designed to utilise the PGK fuse. Though capable of substantially longer ranges, the new projectile is substantially similar to currently fielded 155 mm rounds.
Material Difference
The US army is also working to ensure that unguided artillery shells, which can be fired out to greater ranges than previous artillery rounds, are also designed to withstand the stresses of such use.
Engineers at the US army’s Picatinny Arsenal have been working to potentially extend the range of cannon artillery with new manufacturing methods that improve artillery shells, allowing them to withstand higher launch velocities and temperatures. This requires new material to be used in the manufacture of artillery shells. “We knew that for larger calibre or extended ranges, the material we were using wouldn’t survive. That was really the impetus for advanced manufacturing,” said Joseph Paras, a materials engineer, who is with the Combat Capabilities Development Command Armaments Centre, which is part of the Army Futures Command.
In an artillery shell, the driving band or rotating band is a band of soft metal near the shell’s bottom, often made of gilding metal, copper or lead. When the shell is fired, the pressure of the propellant forces the metal into the rifling of the barrel and forms a seal. That seal prevents the gases from blowing past the shell and engages the barrel’s rifling to spin and stabilise the shell. But the copper rotating bands for current US artillery projectiles were designed for 39 calibre gun systems. Historically, copper has been used as the rotating band material due to its properties and ability to survive gun launch with minimal damage to the gun tube.
But these copper rotating bands do not survive the high launch velocities and temperatures when used on extended range ammunition and 50+ calibre systems. Hence the US military is exploring solutions to develop not only new material but also new manufacturing methods that do not exist in the US industrial base now. The goal of the programme is to develop a manufacturing solution for the rotating band used on US extended range munitions, including the XM1128 and XM1155.
“This project is going to be tied to the XM1113,” Paras said. “That’s really the target, but in terms of adapting it to other systems, whatever we learn here can be applied to other 155mm or 105mm systems.”