Long Shots: naval gunnery is back in fashion

From DTI September 2007 issue

Long Shots

Sep 7, 2007

Bill Sweetman

Naval gunnery is back in fashion as surface ships go for greater impact

Guns on warships are like the guns on fighter aircraft, in that they have often been considered on the road to extinction. When the U.S. Navy's gigantic Iowa-class battleships were decommissioned in 1992, the era of 16-in. guns firing 2,700-lb. shells ended forever.

Arguably, advances in ship gunnery had stopped long before, with the automatic high-rate-of-fire 8-in. (203-mm.) weapons on the Des Moines cruisers. The 4.5-in., 5-in. and 130-mm. guns on more modern warships -- all in the same overall class -- were secondary armament, the main offensive and defensive weaponry comprising missiles.

But gunnery is making a comeback because the role of the warship is changing once again. One of the main functions left for a non-aviation surface combatant is to support land combat in littoral regions, particularly in the opening stages of a conflict before airports and seaports are secure. Amphibious and airborne forces flow into a combat zone along slender pipes, and the presence of a warship can let them leave heavy artillery behind the first waves.

However, contemporary naval guns don't shoot far enough to provide much help to land forces. A recent example of a naval gunfire operation that made the headlines was the firing by the Aegis destroyer USS Chafee (DDG-90) of "more than a dozen" unguided shells from its 5-in./54-cal. BAE Systems Mk 45 Mod 2 main gun on the position of a suspected Al Qaeda operative in northern Somalia on June 1. But this was unusual: with a range of 13 naut. mi. (24 km.), the Mk 45 is normally useless for fire support.

Now, the U.S. Navy has two major gun programs in the works. Underway for many years, and not without its challenges, is the Raytheon-developed EX171 extended-range guided munition (ERGM), which is intended to dramatically increase the range of the Mk 45s fitted to Arleigh Burke-class destroyers: the modified gun and rocket-boosted, guided shell are intended for a range as high as 63 naut. mi. (117 km.), allowing them to shoot 38 naut. mi. (70 km.) inshore from a 25-naut.-mi. standoff range. For example, a ship sailing off Dover could hit the Defense Systems & Equipment International site in London's Docklands.

The 155-mm. Advanced Gun System (AGS), under development for the DDG-1000 Zumwalt-class destroyer, is even more ambitious: the biggest new naval gun designed since World War II, it is intended to lob its Long Range Land Attack Projectile (LRLAP) to ranges of at least 83 naut. mi. (150 km.). This is almost four times the range of the guns on the Iowa-class battleships, and exceeds the range of the ultra-long-range "Paris gun" fired by Germany in World War I.

ERGM started as a Texas Instruments program in 1996, with the goal of initial operational capability (IOC) in 2001. The program is now under contract with Raytheon, which acquired TI in 1997, and is not expected to achieve IOC until 2011. "If it was easy, it would have been done a long time ago," comments Navy program manager Capt. Lee Bond.

ERGM is a GPS-inertial guided, rocket-boosted munition with fold-out tails and movable canard steering fins. Initially designed to carry a payload of submunitions, it was redesigned with a unitary payload in 2002. Only two of seven test flights in 2005 were regarded as anything except failures. "The shock of accelerating from zero to hypersonic speed is kind of hard on the electronics," says Bond with some understatement.

In 2004-06, the Navy explored an alternate round, the Ballistic Trajectory Extended Range Munition (BTERM) from ATK, but this too experienced test failures and the Navy canceled it, although development continued through Fiscal Year 2006 under congressional funding. Meanwhile, Raytheon has produced a redesigned ERGM system -- that addresses both technical and obsolescence issues -- while BAE Systems and the Navy have worked on making acceleration within the gun more stable.

The Navy has also reduced the number of ERGM-capable ships, abandoning plans to equip 22 Ticonderoga-class cruisers with the weapon. It will now be fitted to the last 32 Burke-class ships, starting with DDG-81 Winston S. Churchill, which carry the improved 62-caliber Mk 45 Mod 4 gun.

The redesigned -- and, it is hoped, definitive -- ERGM round is headed for a four-round engineering demonstration firing series in December. This should be followed by a 20-round series of reliability firings, ending in September 2008 and paving the way for a low-rate initial production (LRIP) decision. That will lead to land-based development test firings and integration tests with the Mk 45 Mod 4 gun and its Mk 160 fire-control system, with shipboard tests starting in 2010.

After the extremely difficult development of ERGM, producing a bigger, longer-range, rocket-boosted projectile for AGS might seem foolhardy. However, Bond believes that the newer gun is in some ways less risky. The guidance, navigation and control (GNC) electronics are the same size, leaving more space for packaging and protection, and the new gun has been designed by prime contractor BAE Systems to provide smoother acceleration. Lockheed Martin is responsible for the development of LRLAP, and test firings of prototype weapons in summer 2005 were largely successful, achieving a range of up to 63 naut. mi.

AGS is a radical gun system with an all-electric, unmanned mount -- matching the more-electric systems of the ship itself -- including a 300-round automated magazine. The system is designed for a sustained rate of fire of 10 rounds per minute, with the gun elevating to a vertical position for loading. The turrets match the low radar cross-section design of the DDG-1000. So far, the LRLAP is the only projectile that AGS will fire: in order to let the GPS acquire a satellite signal more quickly, the barrel has less twist in the lands and grooves that impart spin to the round, so the ability to shoot an unguided projectile has been lost.

AGS and LRLAP have completed some successful trials and the first gun, mount and LRLAP projectiles for development testing are now being designed. The next test firings will not take place until mid-FY 2009. The program office's goal is to have the weapon ready for integration in FY 2011. Currently, the two authorized DDG-1000 ships are due to be delivered in FY 2012 for operational evaluation starting in the last quarter of FY 2013.

A key feature of both ERGM and the AGS is known as MRSI (multiple rounds, simultaneous impact). By adjusting the elevation angle and the projectile's flight path, the time of flight to a given point can be changed, making it possible for up to six rounds per gun -- 12 rounds per salvo from the two-gun DDG-1000 -- to impact within a second. This is why Bond can compare the effectiveness of a single DDG-1000 to a Marine artillery battalion with 18 guns. Normally, one of three batteries in the battalion is moving at any one time, leaving 12 guns to fire, and since individual rounds cannot achieve MRSI, the ship's two guns deliver an equivalent salvo. Over the longer run, too, the AGS has a higher sustained rate of fire than conventional artillery.

The Mk 45 Mod 2 gun is on the latest Burke-class destroyers. Rocket-boosted projectiles make it effective for offshore fire support.Credit: BAE SYSTEMS

However, this capability comes at a cost that makes the AGS and DDG-1000 controversial. In the long evolution of the ship design from the DD-21, through the DD(X) and into the DDG-1000, displacement has been reduced and features removed to save money. The initial design envisaged a magazine capacity of 1,200-1,500 rounds, but that was first cut to 920 rounds and then to the current 600 (that is, one 300-round magazine per mount). In one sense, 600 rounds is a lot; in another sense, it is only 30 min. of firing. According to analyst Robert Work of the Washington-based Center for Strategic and Budgetary Assessments, the Navy has developed an "infinite magazine" concept in which DDG-1000s are resupplied with palletized ammunition that the ships receive by helicopter lift without leaving the firing line.

Even with the reduced weight, the DDG-1000 is the biggest U.S. Navy surface combatant since the 1950s nuclear cruiser USS Long Beach. And, as Work points out, there is a dichotomy between the DDG-1000's stealthy design and a concept of operations that involves routine approaches by very non-stealthy helicopters. Also, the weapon load represents a challenge for any helicopter operation. Even discounting the mass of pallets and propellant, a full load of LRLAPs represents 16 sorties by today's CH-53E, the heaviest Navy/Marine helicopter, and eight deliveries by the forthcoming CH-53K. Moreover, the CH-53E fleet is vastly overstretched, and the CH-53K will not even begin to be operational until 2015.

Further complicating the picture is the fact that based on current plans, the DDG-1000 ships will remain a small class. The Navy intends to adapt the design to the CG-21 cruiser optimized for air and missile defense, with the two AGS mounts replaced by missile-launch tubes. As a result, the entire AGS/LRLAP program is likely to end up arming seven platforms at most.

In Europe, the main focus has been on developing improved rounds for in-service 127-mm. guns, since Germany has abandoned plans for 155-mm. armament in its new frigates. The largest new-technology program in the field of naval gunfire support is the development by Oto Melara of Italy of the Vulcano family of extended- and long-range sub-caliber munitions for that company's family of 127-mm. naval guns, as well as for the Mk 45 gun family. The slender sub-caliber projectiles do not carry the same explosive load as the ERGM, but obtain greater range without rocket boost.

Phase 1 of the Vulcano program is backed by the Italian and Netherlands navies, and may have found a third customer in the German navy.

With two 155-mm. rapid-fire guns, DDG-1000 has a more powerful gun armament than any ship designed since World War II.Credit: U.S. NAVY CONCEPT

Italy has 14 surface combatants equipped with an Oto Melara 127-mm./54-caliber main gun, comprising two Durand de la Penne-class destroyers, eight Maestrale-class and four Lupo-class frigates. Ten new Italian/French Fremm-type frigates will receive the latest 127-mm./64-caliber extended-range variant, which has a firing rate of 35 rounds/min.

Germany recently also ordered the 127/64 guns for its four new F125 frigates (plus a fifth gun to equip a land-based test site). This decision was deemed remarkable because it meant the end to an ambitious plan to equip the F125 ships with naval versions of army artillery systems, notably the Krauss-Maffei Wegmann/Rheinmetall PzH 2000 self-propelled 155-mm./52-caliber howitzer and the guided multiple-round rocket launcher (GMLRS). According to German industry sources, the complexities of modifying and porting these land-based systems to make them suitable for the naval environment had been underestimated.

In the Netherlands, the main naval gunfire support weapons available to the Royal Netherlands Navy are the 127-mm./54-caliber Oto Melara guns carried on the four new LCF-type air-defense and command frigates. According to the country's state secretary for defense procurement, Cees van der Knaap, these guns assume extra importance now that the new Dutch government has canceled a proposed buy of Raytheon tactical Tomahawk land-attack cruise missiles for the LCF ships.

"The Netherlands has teamed with Italy in an effort to improve the land-attack munitions available for these guns," says van der Knaap. "In a first phase, this Vulcano project entails the development of unguided munitions with a range of up to 70 km. (38.8 naut. mi.). The munitions will be available next year." Development and procurement is costing the Netherlands 19 million euros ($25 million), he says.

Phase 2 entails the development of guided munitions with a range of more than 100 km. (55.5 naut. mi.), says van der Knaap, but whether the Dutch (or the Germans) will participate in this phase, or indeed acquire the extended-range guided Vulcano munitions, is yet to be decided.

According to Oto Melara, the Vulcano program intends to provide warships with the capability to perform long-range precision bombardment against area targets with a radius of more than 250 meters (such as a tank company or a logistics installation), against point targets with a radius of around 100 meters (a brigade command post), and against precision targets (10-meter radius) such as bunkers or vehicles.

For this mode, Vulcano rounds will start a GPS/IMU (inertial measurement units)-controlled glide 60 sec. after firing, when they are 50 km. downrange and at the 18-km. apogee of their ballistic trajectories. They will perform a GPS/IMU-controlled terminal top-attack when above the target. The glide phase will typically last 140-230 sec.; the terminal attack phase 10 sec.

Oto Melara also plans to equip a Vulcano variant with an infrared terminal seeker, providing long-range, precise anti-surface warfare capability against naval targets, including small fast-patrol boats. In this version, the Vulcano round starts looking for the target when overhead at an altitude of 2,500 meters (8,200 ft.). In both modes, the rounds carry a pre-fragmented semi-armor-piercing warhead.

Sabots separate from Vulcano airframe upon exiting the barrel.Credit: OTO MELARA

System design requirements include a maximum effective range of 70 km. for the unguided munition, 100 km. for guided munitions fired from the 54-caliber gun, and 120 km. for guided munitions fired from the 64-caliber gun. Accuracy is said to be better than 20 meters; payload performance is designed to deliver 100 kg. (220 lb.)/min. over a 1-hr. sustained period, 200 kg./min. over a 3-min. period and 300 kg./min. over a 10-sec. salvo.

The Vulcano concept is based on a fin-stabilized projectile without rocket assistance. Range enhancement is achieved by greater muzzle velocity and improved aerodynamics compared with a full-caliber shell, Oto Melara says. The Vulcano rounds will be compatible with existing loading systems (although the 127-mm./54-caliber Compact operated by the Dutch and the in-service Italian ships need minor modifications).

So far, live-firing tests show that the airframes designed for the Vulcano extended and long-range rounds create no anomalous wave pressures and have "good average muzzle velocity" of 1,070 meters/sec., Oto Melara claims. Ranges of more than 48 km., with the apogee point at a range of 27.5 km. and an altitude of 10,500 meters (34,500 ft.), were achieved using a gun elevation of 33.5 deg. Wind-tunnel tests in Germany in 2006 looked at two designs for the canards that are used to control the round in its terminal phase, and tested the control actuation section under realistic pressure conditions.

The advantage of the European approach appears to be less lofty goals, possibly yielding a better chance of success, and the fact that it is compatible with a wide range of future guns, while ERGM is confined to a subgroup of a single ship class.

Overall, naval gun design remains an unusual industry -- building boutique quantities of weapons custom-fit to a few ships. Maintaining the technology for shipboard guns will probably continue to strain national budgets.

With Joris Janssen Lok in The Hague.