Armed with ERGM, Navy gun fire is fast and deadly

Sea Power, Sep 2003 by Ripley, James

New Gun, Fire Control System Enable Ships to Boost Accuracy on Inland Targets

Captain Joe Stevens and his Marines were in position to assault the terrorist compound ten miles inland when, right on time, explosions erupted around the compound. Stevens was somewhat surprised how fast it all happened and was amazed at the accuracy of each round. Three rounds hit on and around the two guard posts, four rounds landed in the vehicle parking area, and six more rounds hit the anti-aircraft battery that was positioned near the compound. The Extended-Range Guided Munition (ERGM) rounds that were fired from the two destroyers in the expeditionary strike group all landed within two seconds of each other. Capt. Stevens noted that the effect was truly devastating since the terrorists had no time to take cover.

The Marines quickly moved in to secure the compound with very little opposition. A few minutes later Stevens was informed that his Dragon Eye unmanned aerial vehicle had spotted three vehicles with armed terrorists approaching a couple of miles down the road. He quickly had his forward observer submit a call for fire using the Data Automated Communications Terminal, which sent a digital fire request to the Supporting Arms Coordination Center (Automated) on the amphibious assault ship USS Iwo Jima 15 miles off-shore. The fire mission was quickly forwarded to the destroyer USS Shoup's Naval Fire Control System (NFCS) via digital interlink for execution. Within three minutes of the request the Shoup's 5-inch/62-caliber Mk45 Mod 4 gun had fired off four more ERGM rounds in a predetermined pattern available in the Mk160 Gun Computer System. A few minutes later the ERGM rounds landed in a line down the road catching the lead vehicle and causing the others to drive off the road and attempt to take cover. As the Marines started firing at this group of terrorists, the forward observer used his Target Location and Designation and Handoff System to laser identify the enemy's position and call in another fire mission. Stevens knew these terrorists didn't have a chance when three ERGMs simultaneously landed on top of them. He then called in four MV-22 tiltrotor aircraft for the unit's extraction. The mission was a complete success with no friendly casualties.

This battle scenario illustrates the possible implementation of new capabilities currently under development by the Naval Surface Fire Support Program Office at the Naval Sea Systems Command. Programs providing these capabilities will support the new transformational concepts described in the Navy's Sea Power 21 and the Marine Corps' Expeditionary Maneuver Warfare documents.

Key Naval Surface Fire Support (NSFS) components under development include the 5-inch/62-caliber Mk45 Mod 4 gun, the ERGM, and the Naval Fires Control System.

The Mk45 Mod 4 Gun

The new 5-inch/62-caliber Mk45 Mod 4 gun replaces the older Mk45 Mod 2 version-which has a range of only 13 nautical miles-that has been the only naval gunfire support system in service since the retirement of the Navy's battleships more than a decade ago. Installation of the Mod 4 gun began on the destroyer USS Winston S. Churchill and will eventually equip all subsequent Arleigh Burke-class guided-missile destroyers. Selected Ticonderoga-class guided-missile cruisers also will receive the new gun under the Cruiser Conversion Program.

The Mod 4 gun, with its improved recoil and more advanced electronics, was primarily designed to accommodate the ERGM. The gun also fires the conventional 5-inch round. The Mod 4's barrel is 40-inches longer than the barrel of the Mod 2.

The Mk45 Mod 4 is a component of the Mk34 Mod 1 Gun Weapon System-a fully integrated subsystem of the Aegis Combat System-that interfaces with the Naval Fires Control System. The other two major components of the system are the Mk160 Gun Computer System and the Mk46 Optical Sight.

The Development Test and Evaluation for the Mod 4 gun mount was successfully completed aboard the destroyer USS Lassen in November 2002, followed by an Operational Test and Evaluation and Maintenance Demonstration event for the Mod 4 gun mount in December 2002. The gun was qualified to fire conventional rounds for the two Mod 4-equipped destroyers that deployed to the Persian Gulf for Operation Iraqi Freedom.

ERGM

ERGM is a revolutionary, rocket-assisted, boost/glide trajectory projectile that can be fired from the Mod 4 gun to ranges in excess of 50 nautical miles. With guidance from a global positioning system (GPS), the highly maneuverable ERGM will strike targets within a few meters of a specified target location.

The 110-pound ERGM round consists of three basic subsystems: the navigation and control electronic subsystem; the unitary blast/fragmentation warhead; and the rocket motor.

The ERGM uses the high-energy, Ex 99 nitramine propelling charge that is being specifically developed for the ERGM round. The propelling charge greatly increases muzzle energy to levels that create a very challenging environment for any projectile, let alone one that includes a rocket motor and a highly sophisticated guidance electronics unit.