(Published in SP’s Naval Forces Oct- Nov 13)
Guns Remain in Navy’s Future Plans
“The kind of fire support that the Marines need for manoeuvre ashore in the littorals is not the tactical Tomahawk, it’s the kind that comes from a gun….we don’t have it [even though] the requirements have been articulated. … We have a hard requirement for a gun. We are not going to fall off from that requirement.”
-LT Gen Emil Bedard, USMC, Deputy Commandant for Programs
Studies were carried out in the US to meet the requirements of the US marines, after the massive battleships of IOWA class were 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, and that 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 (5 inch). During protracted war, the large calibre gun outshines the missiles and the smaller calibre guns because of large replacement costs of the missiles, much less lethality of smaller calibre rounds as well as the large numbers of both the missiles and rounds required to be stored on board. With the advent of Precision Guidance in larger calibre rounds, collateral damage has been considerably reduced. Their 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 work horse armament on board 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 on board 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 explosives shells to large distances (>100Kms) 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 (>100Kms) and accuracies. M/s Oto Melara is developing Vulcano and DART munitions for 127/64 gun & 76/62 Strales. The Long Range Land Attack Projectile (LRLAP) for the Advance Gun System (AGS) mounted on Zumvalt Class Destroyers of the US Navy is being developed by BAE Systems.
The Oto Melara 127/64 gun has been discussed in the SP’s Naval Forces issue Apr-May 2012 and also in Dec 2012-Jan 2013, in this article it is intended to discuss the main guns carried by the US Navy.
Advanced Gun System (AGS)
The 155mm (6-inch) Advanced Gun System, manufactured by BAE Systems (Minneapolis) , is intended to fill the gaps in Naval Gun Fire Support role of the US Navy in providing a heavy volume, precise and sustained gun fire support to forces ashore. The gap has occurred due to decommissioning of the Iowa Class Battleships, which had the huge 16-inch guns, those ships could provide massive support to forces in NSFS role and they themselves could sustain hits due to their 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 their 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. For the other two ships they are under various stages of delivery as per the requirements of the yard.
The LRLAP ammunition is being developed by BAE Louisville, Kentucky 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 6 shells can hit the target within 2 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 GPS and Inertial Navigation System. Being rocket boosted, the CEP is between 20 and 50 meters. 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 155 mm AGS-Lite (AGS-L). The AGS-L can fire the LRLAP round up to a range of 74 nautical miles at the rate of 6 rounds per minute for land targets and is also able to fire a high capacity ballistic 155 mm 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-Caliber Gun System Upgrade
The US Navy has been using the 5 inch gun virtually since WWII; this gun packs in a more powerful punch with its heavier shell burst charge than other similar systems. The new variant 5”/62–calibre comprises of 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 whilst retaining 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 8 cruisers of the CG47 class and 30 destroyers of the Arleigh Burke class. The range with conventional shell is ~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 this 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 ~10 rounds per minute and a CEP of ~ 10 meters at full range.
Close in Weapon System CIWS
A close in weapon system 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; (a)The effective range of gun systems is less than 4500 meters, simulation studies have put the effective kill distance between 500 meters and 800 meters, which gives an interception time of about ½ a second against supersonic ASCMs and implies that fragments from the destroyed missile could still hit the ship causing damage to man and material above the water line; (b) 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 to other missiles which may be targeting the ship;(c) 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 on coming ASCMs, in fact CIWS today employ both guns as well as missiles. Some major CIWS are; Mk 15 Phalanx (USA), Goalkeeper (Netherlands), DARDO (Italy) and the AK- 630 (Russia). The US navy has ~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 ant- air warfare. The Phalanx System is designed as a standalone integrated system which encompasses 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 be 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 is has its own rate integrating gyros.
The heart of the Phalanx system is the versatile M61A1 20 mm Gatling gun, providing a rate of fire between 3000-4500 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 20 mm MK 149 armour piercing discarding sabot which is a sub calibre, spin stabilised tungsten penetrator.
The latest modification (the Block 1B configuration) caters for defence against asymmetric threats such as UAVs, small, fast surface craft, and slow-flying aircraft. An integrated forward-looking infra-red (FLIR) system has been incorporated to enable this feature. It also has an optimized 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 (Enhanced Lethality Cartridges) has longer effective range as it uses a heavier optimized 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 9 kms. 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.
The above discussion brings out the fact that 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 long range 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. The above may change by 2030, only if the missile costs and sizes drop drastically and the numbers stored on board can be increased substantially.