Armed With ERGM, Navy Gun Fire is Fast and Deadly

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

By JAMES RIPLEY

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.

Once launched, the round stabilizes as the six tail fins deploy. The rocket motor ignites at a predetermined time propelling the round up to a maximum altitude of 80,000 feet. Four forward positioned canards then deploy providing the primary control surfaces.

The ERGM is provided guidance and initialization data from the gun weapon system.

An encrypted code in the guidance unit allows it to acquire and track GPS satellites for its guided trajectory toward the pre-initialized target location. The GPS works in conjunction with an inertial navigation system that actually controls the flight. A guided gunfire flight test in June 2002 demonstrated ERGM's accuracy to within 4 meters of the intended target.

The ERGM is designed to arrive at the target nearly vertically to maximize the blast effect of the unitary warhead. A multiple round simultaneous impact capability may also be directed by the gunfire computer system, allowing up to nine rounds fired from one gun to be programmed to simultaneously arrive on target in a predetermined pattern within 1.5 seconds of each other. This area target coverage has potential to produce a volume-of-fire effect with fewer rounds than would be required with conventional munitions.

A Critical Design Review for the ERGM was conducted in May 2003 at Raytheon Missile Systems in Tucson, Ariz. An independent executive review team expressed its confidence that the ERGM and the propelling charge designs meet requirements with test plans in place for qualification; have mitigated risk; meet fundamental safety criteria; are producible; and meet the acquisition program baseline cost threshold. The ERGM was approved to proceed with the land-based flight test effort.

The series of land-based flight tests began in the summer of 2003 at White Sands Missile Range. These tests--scheduled to run through the end of 2004--will progressively validate the design and performance of all the ERGM subsystems.

The ERGM has been successfully test fired at tactical launch pressure from the upgraded Mod 4 gun at White Sands Missile Range in New Mexico. These tests validated the gun's capability to fire the ERGM to extended ranges. Final gun modifications are being completed to match the deployment of the ERGM, scheduled for 2006.

Naval Fires Control System

The Naval Fires Control System (NFCS) is a computer-automated mission planning and battle management system that will enable surface forces to conduct land-attack missions within a network-centric environment. The NFCS significantly automates shipboard fire support management functions in order to reduce NSFS team manning and shorten mission-processing time.

The system will digitally connect a surface combatant to the Advanced Field Artillery Tactical Data System (AFATDS) being used by the Army and Marine Corps. That connectivity flows through the AFATDS system at either the ground unit's fire support coordination center or the Strategic Arms Coordination Center (Automated) located on an amphibious assault ship. NFCS receives targeting data, conducts planning and coordination of surface fires, and executes fire missions through interfaces to the ship's weapon control systems. This automated process is a major improvement to the traditional method that relies solely on voice radio communications for a call for fire.

Major functions of NFCS include providing a tactical picture for operational area situation awareness; scheduling, assigning and directing engagements of preplanned and call-for-fire missions; dissemination of position data relayed from ground forces; real-time coordination and deconfliction of fire support missions with joint force missions; the selection of the proper ammunition; monitoring the execution of fire missions; and reporting readiness levels of the land-attack shipboard system.

The NFCS has performed well during land-based testing conducted with live gunfire at Naval Surface Warfare Center Dahlgren's Potomac River Test Range in Virginia. A further at-sea test which also included live gunfire was conducted onboard the destroyer USS Howard in September 2002. During this test, the world's first shipboard live fire digital call-for-fire was executed. The initial operational capability for NFCS is scheduled for June 2004.

Future

The Mk45 Mod 4 gun along with the ERGM and NFCS will be major land-attack components to be installed under the Cruiser Conversion program. Other surface fire support programs under development include the Autonomous Naval Support Round, which is similar to the ERGM but flies a guided profile; various warhead improvements; and the 155mm Advance Gun System and the 155mm Long-Range Land-Attack Projectile which will be installed on the next-generation destroyer, DD(X).

Challenges ahead that must be resolved as these transformational systems join the fleet include establishing reliable over-the-horizon communications to conduct long range fires, and refining deconfliction procedures to accommodate ERGM and similar rounds that travel through joint airspace.

The integrated land attack systems described above that are being delivered by the NSFS program office will provide a major improvement in sea-based fires to the warfighter. The progress on these programs demonstrates the commitment by the Navy to deliver highly capable surface fires as envisioned in the Sea Strike component of Sea Power 21. *

James Ripley is deputy program manager, Naval Surface Fire Support, Naval Sea Systems Command.