Artillery: Acrobatic Guided Shells

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May 29, 2020: The U.S. Army has successfully tested the new 1B version of the Excalibur GPS guided artillery shell. The 1B model can turn in flight and hit targets behind a ridge (the “reverse slope”) or under a bridge. In effect, the Excalibur is programmed to carry out a high-speed U-turn so that it comes down behind a ridge next to a bridge. Artillerymen have mentioned that they are often asked to hit Islamic terrorists on the reverse slope or under a bridge because that provides them some protection from guided artillery shells, rockets and mortar shells.

The 1B may not enter service because of cost or reliability issues. Moreover, there is already a cheaper solution for hitting personnel or equipment on a reverse slope or under a bridge; the MOFA (Multi Option Fuze for Artillery). Entering service in early 2003, American artillery units began to receive one of the few fuze breakthroughs in over half a century. The M782 MOFA is a multi-mode fuze. Before GPS guidance was added, there were four basic fuze functions for artillery shells. And never before have the original four been found in one fuze. The M782 can be set to explode on contact, or after a short delay once hitting something, in order to do more damage to fortifications or buildings. Then there is ToT (time on target) where the shell explodes in the air after a certain number of seconds. Finally, there is Proximity Mode, where a tiny radar set in the fuze detonates when the shell is 5-10 meters (16-30 feet) from something (usually the ground). The ToT and Proximity setting both produce air-bursts, which do less damage because most fragments up and outs rather than right into the ground. The Excalibur 1B explodes on the ground, inflicting more damage to the target.

MOFA can also be set by machine, which is how fuzes are set if a lot of them have to be set in a short amount of time. MOFA made life a lot easier for artillery crews and replaced seven earlier fuzes. After 2003, older fuzes quickly disappeared from service. MOFA comes in two versions, one for 105mm shells, and the other 155mm shells and bother are still in use despite the appearance of GPS guided shells.

One reason for developing the 1B version was to keep Excalibur completive with the cheaper M1156 Precision Guidance kit fuze, which became available in 2011, costs one fifth what Excalibur does and is screwed into the front of the shell, just like MOFA or any other fuze would be. A similar M395 GPS guidance fuze for 120mm mortar shells was introduced in 2011 and has been popular (and successful) with the troops. The 120mm mortars are attached to brigades and controlled by the brigade commander. The M395 equipped 120mm shell lands within six meters of the target at 7,000 meters (max range of most 120mm shells) and became available shortly after M1156. That was because both these fuzes used the same tech and were from the same manufacturer.

The army has found that GPS guided shells were more successful than anticipated. As a result orders for “dumb” (unguided shells) were sharply reduced. The high accuracy often meant that only one Excalibur or M1156 equipped shell had to be used to destroy a target. This meant that demand for GPS guided shells also soon declined. Another reason for lower GPS shell demand was the fact that were so many other guided missiles and bombs available. These often destroyed targets before GPS guided shells got a chance. The GPS guided MLRS (GMLRS) rocket has been very popular and often the first choice of commanders in need of some precision firepower. The army also uses a lot of laser-guided Hellfire missiles, fired from AH-64 helicopter gunships. In addition to the reduction in Excalibur production, the army has cut the number of M395 GPS guided 120mm shells on order.

From the beginning, Excalibur and the ATK fuzes were facing a lot of competition from GMLRS (GPS guided multiple launch rocket system), which cost about the same as an Excalibur shell but has a much longer range and a bigger bang. Another edge GMLRS had was the truck-based HIMARS rocket launcher. Only costing about $3 million each, these smaller truck mounted MLRS (HIMARS) rocket launcher systems have become very popular. HIMARS carries only one, six MLRS rockets, container (instead of two in the original tank-like MLRS vehicle). But the 12 ton truck can fit into a C-130 transport, unlike the 22 ton tracked MLRS, and is much cheaper to operate. The first HIMARS entered service in 2005, about a year after GMLRS did.

The 309 kg (680 pound) GMLRS missile is a GPS guided 227mm rocket that entered service in 2004. It was designed to have a range of 70 kilometers and the ability to land within meters of its intended target, at any range. This is possible because it uses GPS (plus a backup inertial guidance system) to find its target. The army soon found that GMLRS was just as accurate at max range (about 85 kilometers). This enabled one HIMARS vehicle to provide support over a frontage of 170 kilometers or in places like Afghanistan, where the fighting can be anywhere, an area of over 20,000 square kilometers. This is a huge footprint for a single weapon (an individual HIMARS vehicle) and fundamentally changes the way you deploy artillery in combat. Excalibur has a max range of 37 kilometers, and 120mm mortars about 7.5 kilometers.

Nearly all GMLRS rockets are fitted with an 89 kg (196 pound) high explosive warhead. About half of that is actual explosives. These have been used with great success in Iraq, Syria and Afghanistan, where several thousand have been fired so far. The guided rocket is much more effective than the older, unguided, version and has replaced it in the U.S. military. The army stopped buying unguided rockets in 2009. The accuracy of GMLRS means that one rocket does the job that previously required a dozen or more of the unguided ones. That's why HIMARS is so popular. While it only carries six rockets, that's often enough to last for days, even when there's a lot of combat. One GMLRS will often get the job done destroying or demoralizing the Taliban foe.

The GPS 155mm and 120mm shells still have an advantage over GMLRS. The 120mm mortar round has about 2.2 kg (five pounds) of explosives, compared to 6.6 kg (15) pounds in a 155mm shell. The smaller explosive charge limits collateral damage to civilians. But in Afghanistan, it was more common to need a large bang (which GMLRS can deliver). Excalibur was more suited to Iraq and Syria and while American troops left Iraq by 2011, they were back in 2014 using lots of ATK fuzes, especially in Syria where one battery (six 155mm howitzers) was more effective than ten times as many guns firing unguided shells. That battalion was a key element in the ISIL (Islamic State in Iraq and the Levant) loss of their capital (Raqqa) in eastern Syria.

Meanwhile, there are a lot of precision weapons, with small warheads, readily available to the infantry. The Javelin missile has a 4 kg (9 pound) warhead, and the larger TOW has a 5.9 kg (13 pound) warhead. The Hellfire missile has a 9 kg (20 pound warhead). The air force also has its SDB, a 114 kg (250 pound) small diameter bomb, carrying 23 kg (51 pounds) of explosives.

There is still demand for unguided 155mm and 120mm shells. There are times when you need firepower over a large area (several hundred meters by several hundred meters), and for this unguided shells do the job best and cheapest. But precision (or “smart”) shells are the future and these weapons are expected to continue getting cheaper.

Excalibur was becoming cheaper and more accurate and reliable after the AKT fuze showed up. There was less demand for both Excalibur and ATK fuzes because other guided weapons were also getting cheaper, more portable, easier to use and more reliable. This included lightweight explosives equipped UAVs (like Switchblade and Firefly) that infantry could carry and used for reconnaissance and to attack any enemy discovered. The infantry often needs portable precision firepower right away and now they have it.

While MOFA seemed like a major technical advance for artillery in 2003, few realized it was just the start of a decade of even more breakthrough weapons. GMLRS came in 2004, Excalibur in 2007, and ATK fuzes in 2011 along with similar advances in precision weapons carried and used by the infantry.

Excalibur 1b may not enter service for the same reason the 1970s Copperhead laser guided 155mm shell failed to gain widespread acceptance. Copperhead worked but it was too expensive (ten times more than Excalibur) and required someone within a few kilometers of the target operating a laser designator. In practice there was little demand for Copperhead. Russia and China still make laser guided artillery shells, adopting that tech in the 1980s and 90s before GMLRS and Excalibur showed up. The Russians and Chinese have copied GMLRS but not yet GPS guided shells.

 


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