Studies were caried out in the United States to meet the requirements of the US marines, after the massive battleships of Iowa class retired. It was concluded that naval gunfire support had been crucial during the past operations. Larger calibres provide support at much larger ranges and are essential for destroying fortified positions. To achieve similar effects in suppressing the enemy, a much greater number of rounds would have to be fired from smaller calibre guns like the MK 45 (five-inch). During protracted war, the large calibre guns outshine the missiles and smaller calibre guns because of large replacement costs of the missiles, much less lethality of smaller calibre rounds as well as the large number of both the missiles and rounds required to be stored onboard. With the advent of precision guidance in larger calibre rounds, collateral damage has been considerably reduced. The penetration ability in case of hard targets is practically as good as ordnance delivered by air. The air operations in high threat environments are hindered by availability, mission priorities, weather, as well as prohibitive costs. All these make the large calibre gun a very cost beneficial solution in naval surface fire support (NSFS).

The naval gun continues to be entrenched in its position as the main workhorse armament onboard ships of the major navies. Despite some promising developments in the recent past, the naval gun is likely to remain the mainstay at least till 2025 if not till 2040. Promising development on the laser weapon system (LaWS), whose prototype is going to be positioned onboard USS Ponce next year, may lead to a very cost-effective solution against small boats and UAVs, but it cannot replace the naval gun in all its roles. The electromagnetic rail gun appears promising and can fire non-explosive shells to large distances (more than 100 km) with great accuracy at velocities up to 7.5 Mach, but it is some time away from the prototype stage. The missiles, despite their falling price cannot match the cost benefits afforded by the traditional naval gun. In the interim, technological strides in gun shells and fuses have demonstrated very high ranges (more than 100 km) and accuracies. Oto Melara is developing Vulcano and DART munitions for 127/64 gun and 76/62 Strales. The longrange land attack projectile (LRLAP) for the advanced gun system (AGS) mounted on Zumvalt class destroyers of the US Navy is being developed by BAE Systems.

Advanced Gun System (AGS)

The 155mm (six-inch) advanced gun system, manufactured by BAE Systems (Minneapolis), is intended to fill the gaps in naval gunfire support role of the US Navy in providing a heavy volume, precise and sustained gunfire support to forces ashore. The gap has occurred due to decommissioning of the Iowa class battleships, which had the huge 16-inch guns. The ships could provide massive support to forces in NSFS role and could sustain hits due to protection by heavy armour plating.

The AGS was initially known as the vertical gun for advanced ships (VGAS). However, the US Navy decided to go in for the conventional turret design since the VGAS would have been able to fire only guided munitions and could not have utilised the conventional unguided projectiles. The AGS would be fitted on three Zumwalt (DDG 1000) class destroyers to support the naval surface fire support (NSFS) missions. The AGS will incorporate the AGS intra-ship rearmament system (AIRS) for loading of ammunition and safely moving AGS pallets between the gun magazine’s pallet hoist and the flight deck. The AIRS is an all-electric system with performance in sea conditions up to Sea State 3. Up to 10 rounds per minute can be fired from each gun from an automated 304 round magazine. Eight LRLAP are palleted along with their propellant charges. Thus with fully palleted LRLAP ammunition and automated magazines, the Zumwalt class would provide accurate and prolonged gunfire support ashore. The AGS is being manufactured at three locations namely—Cordova, Alabama; Fridley, Minnesota; and Louisville, Kentucky—and is meeting the ship schedules. The AGS magazines and guns have already been delivered for DDG-1000 to Bath Iron Works. The other two ships are under various stages of delivery as per the requirements of the yard.

The LRLAP ammunition is being developed by BAE Louisville and Lockheed Martin Missile and Fire Control, Orlando, Florida. The LRLAP is capable of hitting targets at a range of 137 km with the rocket booster assisted launch. It is multi-piece ammunition and the shell is loaded with modular launch charges and rocket booster. This enables in carrying out multiple rounds, simultaneous impact (MRSI) attack, in which by adjusting the launching charge and elevation up to six shells, it can hit the target within two seconds or hit different targets if selected. The shell weight is 11 kg, while the weight of the complete round is 102 kg with a length of 88 inches. The LRLAP deploys its fins after ejection from the barrel and is guided by a combination of global positioning system (GPS) and inertial navigation system (INS). Being rocket boosted, the CEP is between 20 and 50 metres. This may be improved in future by the incorporation of semi-active laser seeker. The Zumwalt class thus packs a massive punch through its two AGS mountings.

However, since the AGS design is specific to the Zumwalt class, it cannot be retrofitted on any of the existing ships; BAE has therefore come up with 155mm AGSLite (AGS-L). The AGS-L can fire the LRLAP round up to a range of 74 nautical miles at the rate of six rounds per minute for land targets and also be able to fire a high capacity ballistic 155mm ASuW projectile (ASuWP). The AGS-L can store up to 240 LRLAP and 48 ASuWP. It is claimed that it can be tailored to suit existing ships.

Mk 45 Mod 4, 5”/62-Calibre Gun System Upgrade

The US Navy has been using the five-inch gun virtually since World War II; this gun packs in a more powerful punch with its heavier shell burst charge than other similar systems. The new variant 5”/62-calibre comprise a longer barrel L62 Mark 36 gun fitted on the Mark 45 mount. The gun is used in anti-surface, anti-aircraft and NSFS roles. It is currently manufactured by BAE Systems Minneapolis, Minnesota. It is has been designed for firing longer range munitions while retaining the ability to fire all types of existing ammunition. The 5”/62-calibre gun has better maintenance procedures and improved anti-air and anti-surface capability. Apart from a longer barrel, the modification includes a digital control system and an ammunition recognition system. It also has redesigned gun shield, strengthened mount and a better barrel. The gun is in use on eight cruisers of the CG47 class and 30 destroyers of the Arleigh Burke class. The range with conventional shell is about 15 miles and the rate of fire is 16-20 rounds per minute.

A new projectile, the standard guided projectile (SGP), is being developed by BAE Systems on lines of the LRLAP for this gun. The SGP is propelled by a rocket booster and is GPS/INS guided. The unique feature of the 127mm shell is that it can be retargeted in-flight through GPS updating and can thus tackle moving targets. It is likely to have a rate of fire of about 10 rounds per minute and a cumulative error of probability (CEP) of about 10 metres at full range.

Close-in Weapon System

A close-in weapon system (CIWS) is fundamentally designed as a last ditch measure to target incoming anti-ship missiles/aircraft. CIWS gun systems have suffered from some drawbacks as compared to CIWS missile systems namely: effective range of gun systems is less than 4,500 metres, simulation studies have put the effective kill distance between 500 metres and 800 metres, which gives an interception time of about half a second against supersonic anti-ship cruise missiles (ASCMs) and implies that fragments from the destroyed missile could still hit the ship causing damage to man and material above the waterline. There is also a probability that the missile on being hit may not deviate sufficiently from its path, further the CIWS gun systems take time to train on other missiles which may be targeting the ship. Lastly, gun systems are unable to target missiles which use way point targeting.

However, despite the disadvantages, CIWS gun systems have been retained as a terminal effort to tackle ASCMs. In fact CIWS today employs both guns as well as missiles. Some major CIWS are: Mk 15 Phalanx (Raytheon, USA), Goalkeeper (Thales Naval, Netherlands), DARDO (Breda and Oto Melara, Italy) and the AK 630 (AK Tulamashzavod OAO, Russia). The US Navy has about 250 of the Raytheon’s Mk 15 Mod 21-28 Phalanx CIWS autonomous combat systems mounted on the US naval ships. It can be used also against small craft and for anti-air warfare. The Phalanx System is designed as stand-alone integrated system, encompassing search (KU band radar and electro-optic), detection, target declaration, tracking, threat elevation, engagement, fire control and kill assessment. This ensures the rapid reaction time required for CIWS. Thus it can also be utilised by bolting to decks of ships which do not have any type of combat system. It has six major assemblies namely radar and servo assembly, gun assembly, mount and train drive platform, barbette equipment assembly, electronics enclosure and the local and remote control panels. The search platform is horizontally stabilised and attached to a vertical gyro for sorting and correlating the targets according to range, range rate and angular position. The search antenna has standing wave antennas mounted to search platform for giving elevation coverage. The track antenna has its own rate integrating gyros.

The heart of the Phalanx system is the versatile M61A1 20mm Gatling gun, providing a rate of fire between 3,000 and 4,500 rounds per minute, firing specially designed high kinetic energy rounds. The gun is electronically controlled and pneumatically driven. It consists of a rotating cluster of six barrels with a breech bolt for each barrel. The round is a 20mm MK 149 armour piercing discarding sabot which is a sub-calibre, spin stabilised tungsten penetrator.

The latest modification (the Block 1B configuration) caters to defence against asymmetric threats such as unmanned aerial vehicles (UAVs), small, fast surface craft and slow-flying aircraft. An integrated forward-looking infrared (FLIR) system has been incorporated to enable this feature. It also has an optimised gun barrel (OGB) for closer ordnance dispersion. The OGB can also use enhanced lethality cartridges (ELC) for better target penetration. The Mark 244 Mod 0 ELC has a longer effective range as it uses a heavier optimised tungsten alloy penetrator. Incidentally, the under trial SeaRAM Mk 15 Mod 31 CIWS is also based upon the Block 1B Phalanx with the gun system being replaced by the RIM 116 rolling airframe missile (RAM). It is designed as a companion system to target supersonic ASCMs. It utilises the exact deck dimensions of the Phalanx system and so can be mounted conveniently on ships. It has an 11-cell RAM launcher. The RAM is a Mach 2+ missile with a blast fragmentation warhead of 11.2 kg. It has a range of nine km. It can be guided in three modes namely infrared dual mode enabled (radio frequency and infrared homing), infrared only or passive radio frequency/infrared homing.

Trends

Guns continue to provide a cost-effective solution against targets on land, air and at sea, especially with GPS/INS guided lethal ammunition. The US Navy will continue to equip its ships with naval guns at least till 2025, when the laser weapon system may take over the targeting of small craft and UAVs. The electromagnetic rail gun with its non-explosive shells may not replace longrange heavy guns for some time to come. In case of the CIWS, companion systems having both the gun and the missile launcher appear to be the trend. It may change by 2030, only if the missile costs and sizes drop drastically and the numbers stored onboard can be increased substantially.