Spot On!

This is an article published in our April/May 2016 Issue.

M777 155mm howitzers
The US Army, Marine Corps and the Canadian Army’s M777 155mm howitzers, shown firing in Afghanistan. They have increased their range to 40km and achieved an accuracy of five metres at that distance using PGMs. (US DoD)

Precision Guided Munitions (PGMs) have the potential to alter the way artillery indirect fires are employed and to potentially take on missions previously only possible with direct fire weapons, heralding a step change for artillery and ground operations in general.

Capitalizing on electronics miniaturization has permitted packaging advanced guidance and homing sensors into the warhead of artillery and mortar projectiles as small as 81mm but more commonly in 120mm and 155mm calibre. Using a number of techniques already well demonstrated in aircraft-delivered munitions, these PGMs at the least significantly enhance the efficiency of artillery by tightening the CEP (Circular Error Probability; the size of the circle in which a round fired from a weapon will, with high probability, impact) and, at best, will strike a point target. The ramifications of these attributes are still being absorbed and reflected in artillery employment techniques and tactics.

artillery PGM
An operational benefit of the artillery PGM is that the increased round accuracy will effectively neutralize a target and do so without the need for firing adjusting rounds. This would reduce the engagement time and allow two or three guns to have the same effect as a battery of six or eight. (US Army)

Sensor Technologies

Artillery PGMs have focused primarily on the large 120mm and 155mm calibres. These sizes provide the PGM with greater effect-on-target in that the larger warhead has more explosive power, fragmentation and penetration. In addition, they have much greater range and typically broader support roles, particularly 155mm artillery, reflecting a larger number of target engagement possibilities appropriate for PGMs.

Some of the first PGMs reflected the needs of the anticipated battlefield of Northern Europe during the Cold War which emphasised destroying large numbers of Soviet Union and Warsaw Pact (WARPAC) armoured vehicles during an air-land battle involving the North Atlantic Treaty Organisation (NATO). The objective was to attrite the expected mass of armour with main battle tanks and anti-tank guided missiles engaging first line Soviet/WARPAC units and artillery using sub munitions equipped ‘cargo’ rounds and PGMs against following units.

The focus was reflected in a trend from the 1960s through the early 2000s toward reliance on the cargo projectile which would release a large number of high explosive and mine sub munitions over large target areas. This use of sub munitions (also termed cluster bomblets or CBUs: Cluster Bomb Units) was paralleled in air-delivered ordnance. However, it became evident from the aftermath of combat during the US involvement in the Vietnam War between 1965 and 1975, and during US-led interventions in Iraq and the Balkans that the bomblet sub munitions retained a very high ‘dud rate’. Many would not explode and would become a hazard for months and years to friendly troops and unsuspecting civilians. As a result many of these CBUs were prohibited by the 2008 Convention on Cluster Munitions. Any sub munitions thereafter was required to have multiple redundant self-destruct mechanisms. With most sub munitions off-the-table, attention began to shift to alternates. Coincidently advances in miniaturizing electronics was opening the way for packaging these capabilities in fuses and warheads.

The Convention not only eliminated the cluster munitions, it also signalled an increasing recognition and concern for limiting collateral damage in applying weapons in general. This recognition combined with the nature of counter insurgency operations and accompanying focus on building rather than destroying, increased attention to reducing unintentional damage and casualties. These efforts were complicated by the increasing urban nature of many conflict areas. The concept of using overwhelming firepower reflected in the number of rounds fired to subdue an opponent was becoming no longer a reasonable option.

The first ‘modern’ PGM was the M712 Copperhead which was equipped with laser homing guidance. The M712 was developed by Martin-Marietta (now Lockheed Martin) in 1975. Its original impetus was not necessarily reducing collateral damage but rather giving artillery the capability to contribute to attriting the expected onslaught of Soviet tanks in a war in Europe (see above). The M712 was an anti-armour weapon. It homed in on the energy reflected from the target when ‘painted’ by a GLTD (Ground Laser Target Designator) aimed by a forward observer on the ground or from a laser designator equipping an aircraft such as a reconnaissance helicopter. Fired from a 155mm howitzer to a maximum range of 16 kilometres/km (9.9 miles), it has a shaped charge warhead to defeat armoured targets. It was employed during the US-led Operation DESERT STORM to expel the Iraqi occupation of Kuwait in 1991. The M712 required that the target be painted until the round impacted. A benefit of this was that it assured that the target struck was the one the observer had specifically identified. Thus, it was possible to select, designate and reliably destroy high value targets like command vehicles and air defence assets even when they were on the move.

M712 Copperhead
The M712 Copperhead was introduced in 1975 as a precision strike munitions for artillery. It required an observer to designate the target with a laser. The seeker in the head of the projectile would home in on the laser energy reflected by the target. (US DoD)

The Soviet Army fielded its own laser guided 152mm projectile in 1986, the 30F39 Krasnopol. Like the M712 it was fin-stabilized, using a base bleed (where a small gas generator increases the air pressure directly behind a shell to reduce drag during its flight) to extend the range to 20km (12.4 miles). The ground observer’s laser designator could mark a target out to five kilometres (3.1 miles) range from their position and it could be used against stationary and moving targets as long as they were visible. A characteristic of all laser seekers is that they ‘lock-on’ to the strongest ‘signal’. With the delivery gun firing from behind the observer designating the target, the strongest reflected signature ‘seen’ by the seeker will be that reflected of the target. Yet in highly mobile combat or where artillery support might be provided from fire bases situated at any heading from the observer and target this may not be the case. Should the gun be firing where the trajectory of the projectile and seeker is inbound to the observer, it is possible that the designator itself could be the dominant signature and perceived by the laser seeker as the target, clearly not a desirable circumstance for the observer.

Another approach to providing an ant-armour capability to artillery is that used by Bofors and Nexter who collaborated on the development of the 155 BONUS. This 155mm artillery round uses base bleed technology to extend its range to 35km (21 miles) with a 52 calibre gun and 27km (16.7 miles) for a 39 calibre gun. It is a cargo projectile that releases two infrared imaging sensor sub munitions. Once released and descending they scan for target heat signatures and steer using winglets toward the target. Once over head, they detonate with an Explosively Formed Penetrator (EFP) designed to penetrate the less protected top of the target. BONUS is in service with the French, Finnish and Swedish Armies and has been evaluated by the US Army. An improved BONUS Mk.II has been developed with improved target discrimination.

The SMArt 155 is similar to the BONUS. It is a development of GIWS, a partnership between Rheinmetall and Diehl BGT Defence. It too is a 155mm artillery round, designed for a long range and indirect fire top attack using two sub munitions. A primary difference is that it uses parachutes in the descent after release from the munitions. It is in service with the Australian, British, Greek and Swiss armies and the Heer (German Army).

GPS Guidance

The expansion of the Global Positioning System (GPS) network coupled with advances in micro electronics has allowed precise locations to be provided in very small electronics packages. GPS has been adapted to the artillery projectile which when combined with manoeuvring fins or winglets permit the round to be programmed to steer towards and hit a specific programmed location within a few metres. The Excalibur M928 developed by Raytheon and BAE Systems’ Bofors division (not to be confused with the Bofors mentioned above) for the 155mm howitzer uses this technique. The programme is a cooperative development that began in 2008 between the United Sates and Sweden providing a fully-integrated projectile that can be fired from the full range of 155mm howitzers in service with both countries with accuracy of 20 metres (65.6 feet) CEP or better.

The Excalibur has a near vertical decent onto the target. This optimizes the blast and fragmentation effects on the target while also reducing collateral damage. (Raytheon)

Excalibur has a range of up to 40km (24.8 miles) in its latest 1b base-bleed version and in fact achieved a successful combat engagement during the US-led intervention in Afghanistan of 36km (22.3 miles). The initial 1a version has been further improved upon in the 1b to reduce production cost, increase accuracy and address early reliability issues. Tests of the 1b have verified that the projectile routinely achieves accuracy of five metres (16.4 feet) CEP and better. An ‘S’ version adds a semi-active laser targeting capability that offers one metre (three feet) accuracy. It, as well as an ‘N’ naval version for the 127mm gun used on many naval warships, has been presented by Raytheon (please see Gerrard Cowen’s Cannon Fodder article in this issue for more discussion of naval gun developments). Presently Australia, Canada, the Netherlands, Norway, the United Kingdom and the United States are in possession of, or have ordered, Excalibur.

Orbital-ATK has taken a different path toward providing advanced guidance to the 155mm projectile. Its PGK (Precision Guidance Kit) is a ‘course correction’ projectile provided as a kit that transforms a standard 155mm projectile into a PGM. The PGK M1156 allows the gun crew to change the fuse and adds fins to the standard M549A1 and M795 155mm projectiles. The M1156 accepts a lower accuracy to bring down the unit price of each round. The last unit price of the Excalibur was $40000 but it had been $150,000. The PGK’s unit price was expected to drop in 2016 to under $11000 from $20000; however, this price could be affected if orders are lower than projected. The PGK’s CEP accuracy is under six metres (20ft). Recognising that the CEP of the standard fused M549 is 267m (875ft), this is still an exceptional improvement. The PGK is in service with the US Army, the US Marine Corps, and the Australian and Canadian Armies. The design has also been adapted to the 120mm heavy mortar.

Naval PGMs

Naval guns have, in many navies, been superseded by missiles for surface-to-surface engagements. The greater range and accuracy of the guided missile offered benefits that guns for many years could not provide. While generally acceptable in ship-to-ship combat the trend toward eliminating or reducing major calibre guns on naval combatants became a major concern to naval forces as naval gunfire is critical in inserting forces into hostile littoral areas, particularly in the initial stage of a landing before artillery can be established on the ground. The lack of shipboard guns compromised the ability to provide naval fire support to the landing forces. Naval guns can be on-station and immediately available to respond to calls-for-fire and are less likely to be affected by weather and visibility (as might be the case for close air support and battlefield interdiction). The challenge for naval guns today is first to provide greater range to allow ships to stand off the coast, thereby reducing their vulnerability to ground launched anti-ship missiles. Secondly, given the increased range and recognising the limited number of ships and guns available to support a landing, navies must examine how to increase their target engagement efficiency.

USS Porter
The introduction of PGMs to naval guns are giving them a new level of capability. The increased range and point target accuracy make them an effective answer to the small fast attack boat threat. Here the USS Porter fires its Mk.45 127mm gun. (US Navy)

OTO Melara (now Finmeccanica), one of the leaders in naval guns, took on these challenges. It developed the Volcano munitions family consisting of unguided (BER) and guided (GLR) ammunition for the 127mm naval gun. Realizing the suitability of their concept to land warfare they applied the same techniques to 155mm artillery. The BER (Ballistic Extended Range) is unguided multi-role ammunition with multi function (Altimetric, Impact, Delayed Impact, Time, Self-Destruction) programmable fusing. The GLR (Guided Long Range) is equipped with canard controls and an inertial measurement unit (IMU)/GPS guidance system with an optional Semi-Active Laser (SAL) terminal guidance. The rounds are fin-stabilized sub-calibre and as a result are able to reach ranges of 50km (31 miles) and 80km (49 miles) respectively for the BER and GLR. The 127mm naval round also includes a version with an infrared imaging seeker for terminal guidance against ship targets.

OTO Melara Volcano
The OTO Melara Volcano extended range munitions use a sub-calibre projectile. Shown in this illustration it has a ‘sabot’ or collar that fills the bore but detaches as it levels the barrel. (Finmeccanica)

In 2012 OTO Melara and Diehl BGT Defence signed a cooperation agreement for production and further development of these and future large-calibre conventional and guided ammunitions for naval and army use. In May 2014 the companies demonstrated the Volcano firing to a range of 50km using a Krauss-Maffei Wegmann/Rheinmetall PzH2000 self-propelled howitzer at the Alkantpan Proving Ground in South Africa. Firings included production configurations of both the guided (GPS and SAL) and unguided versions. Company representatives indicated that the 50km was the safety limits of the range and that the 80km capability of the system would have been otherwise attained.

OTO Melara has further adapted the sub-calibre concept of the Volcano to offer extended range and guided 76mm projectiles for use in their 76/62 naval gun that is employed by 55 navies worldwide. The Vulcano 76 round gives the gun a true multi-mission capability not only against surface targets at sea and on land but also enhances its air defence role. The 76mm Vulcano offers a range of 40km, more than double the conventional round. Coupled with the 76/62s very high rate of fire a single gun can effectively and accurately deliver a salvo in seconds. The unguided 76mm BER was tested 2013 with the guided GLR demonstrated in 2014, with the qualification of the munition for low-rate initial production expected imminently. Fielding of the 76 Vulcano would significantly expand naval gunfire capabilities as shore attack and gunfire support for amphibious forces could be conducted by smaller vessels like corvettes and large patrol vessels that are both more numerous (over 153 vessel classes in 45 navies carry the 76/62) and are more likely to be readily available to be tasked with gunfire support as opposed to more expensive larger combatants.

Another PGM development focused on naval guns is the Long Range Land Attack Projectile (LRLAP) being developed by Lockheed Martin Missile and Fire Control for the US Navy’s BAE Systems 155mm Automatic Gun System (AGS) used on the ‘Zumwalt’ Class Destroyer. The LRLAP uses base bleed rocket assist to extend the range; GPS and inertial navigation system guidance and extended fins achieve a glide trajectory and course correction. It has a 73.9 nautical miles (137km) maximum range with the AGS capable of firing ten rounds-per-minute. Drawing on the 155mm system a version of LRLAP has been designed in cooperation with BAE Systems to be used with the 127mm naval gun. In an interesting turn BAE Systems has taken the LRLAP and is offering it as the Multi-Service Standard Guided Projectile (MSSGP) and offering it as an extended range PGM for the BAE Systems M109 and M777 respective self-propelled and towed howitzer.

M777 155mm howitzers
The US Army, Marine Corps and the Canadian Army’s M777 155mm howitzers, shown firing in Afghanistan. They have increased their range to 40km and achieved an accuracy of five metres at that distance using PGMs. (US DoD)

The success of the LRLAP appears to have possibility encouraged the US Navy to revisit naval gun PGMs. In May 2014 Naval Sea Systems Command (NAVSEA) issued a Request For Information (RFI) on guided rounds available that can be fired from the BAE Systems’ Mk.45 127mm gun. Raytheon submitted a version of Excalibur, OTO Melara the Volcano, and BAE Systems its MSSGP. Paul Daniels Program Manager at Raytheon told AMR that their naval version utilized 100 percent of the front end components of the existing Excalibur. This high commonality allowed them to successfully test fire the round in September 2015.

It is not yet clear if this RFI will lead to a US Navy 127mm PGM programme, but Rear Admiral Thomas Rowden, director of surface warfare for the Office of Naval Operations (OPNAV) has publically stated that, based on the success of LRLAP “If we can do it cost effectively, then we would be foolish not to extend the range of those weapons.” Beyond the shore bombardment role these naval PGMs could offer an effective counter to the anti-ship missile equipped fast attack craft.

Operational Impacts

Since its inception, the destructive effect of artillery has been just one aspect of its ability to influence combat; the other is its physiological effect. Artillery PGMs multiply the impact of both. Coupled with the increases in range without loss of accuracy PGMs broaden the tactical strike options of ground commanders. With PGMs a ground commander is now able to engage with organic ground assets specific targets that previously would have required attack by aircraft. Employing artillery would be more responsive, require less coordination, and not subject to unavailability due to weather.

Possibly more important is the ability to strike critical targets rapidly and seemingly at will fits ideally into the concept of manoeuvre warfare, where the enemy is incapacitated through disruption and shock. Here the emphasis is less on destroying the opponent physically but rather undermining their abilities to respond. It can be, therefore, more valuable to eliminate command and key supporting assets that will disrupt and demoralize than to destroy one hundred main battle tanks. The artillery PGM provides this capability to ground combat commanders at every level from company upwards. This contribution is of greater operational value than the often-advertised fact that using a PGM will save ammunition; a purely logistical benefit that is meaningless if ammunition is plentiful.

The artillery PGM has the potential to not only change the way indirect fire is employed but to alter the application of ground attack aircraft and potentially missiles in support of ground force manoeuvre. Based on US and Allied experience so far in Afghanistan it appears that the appreciation for the capabilities of the PGM are being recognised but that the broader tactical and operational aspects are still evolving.

by Stephen W. Miller