General Electric Marine is planning to offer its GE38 small gas-turbine engine in an upcoming Navy competition for the Landing Craft Air Cushion replacement program. The GE38 already has been selected by the Marine Corps for its CH-53K heavy-lift helicopter.
The company also is evaluating potential opportunities for the GE38 with the Navy’s planned Flight III build of Arleigh Burke–class Aegis destroyers, which the Navy will start funding in Fiscal Year 2016. The Flight III ships, now expected to begin with DDG-121, will incorporate dramatically upgraded combat, command, control, and communications, intelligence and surveillance, and ship computing and control systems. The Flight III variant will retain the current DDG-51 hull form, however.
The Navy is studying options for propulsion-plant architectures for the Flight III. A critical driver, Navy and industry officials say, is the ship’s combat system—weapons, sensors, and processing architectures—that depends on the hull, mechanical, and electrical system for operating power.
GE Marine’s LM2500 gas turbine engine, with a Navy rating of 29,500 hp, powers the Navy’s 22 Ticonderoga-class cruisers and the entire Burke class, four engines per ship. The company provided its LM2500+ gas turbine, rated by the Navy at 35,000 hp, for the Makin Island (LHD-8), the eighth and last Wasp-class amphibious assault ship, in a hybrid arrangement of two LM2500+ engines and two electric auxiliary-propulsion motors. The same configuration also is going aboard the America (LHA-6), the first of a new class that will replace the Tarawa class. The America is scheduled for delivery to the Navy in 2012.
The hybrid setup on the Makin Island already has demonstrated significant savings in fuel costs. Because gas turbines operate most efficiently at higher speeds, savings can be realized when the ship is transiting at slower speeds, which is most of the time, by using the auxiliary electric motors.
A new gas turbine for the Flight III ships would be the prime mover for any of several propulsion-power architectures under consideration, including conventional mechanical drive, as with the current Ticonderogas and Burkes; a hybrid configuration like the one on the Makin Island; and full-up electric drive, which will be the power system for two Zumwalt-class destroyers (DDG-1000 and -1001) now being built at General Dynamics’ Bath Iron Works in Maine. The Zumwalt system is based on an advanced induction motor built by Converteam.
The Navy plans to backfit the Burkes now in the Fleet with a hybrid system under development by DRS Technologies and General Atomics. The team won a Naval Sea Systems Command contract in July 2009 to develop a prototype hybrid-electric drive, or HED, for the Burke backfit.
The HED system consists of a permanent magnet motor, motor drive, and power converter developed by DRS, integrated with system-control electronics provided by General Atomics. During HED low-speed operations, as on the Makin Island, the gas turbines provide power through a motor drive and a frequency converter to the permanent magnet motor, which is fitted to the ship’s reduction gear. This approach, referred to as an electric propulsion system (EPS), is a one-way-drive process that moves power from ship service to propulsion. In a two-way-drive hybrid, which is being considered for Flight III, power is shifted from propulsion back to the electric plant in an arrangement called EPS-propulsion-derived ship service, or EPS-PDSS.
In October 2010 the DRS-GA team completed assembly and component-level testing. The HED configuration will be delivered to the Navy’s land-based engineering site in Philadelphia for further testing this spring, aiming for at-sea testing on board the Truxtun (DDG-103) in 2012.
Officials say that all-electric drive appears unlikely for Flight III because of the size and complexity of the motor and associated components. Electric drive requires several power-conversion modules (PCMs) for distribution of power to ship systems, as well a PCM that acts as a motor drive.
Power-systems engineers stress that a critical priority in choosing the propulsion-power architecture for Flight III is the Navy’s plan to introduce the air-missile-defense radar, or AMDR, for use in the Navy’s ballistic-missile-defense mission. The AMDR, which will consist of S- and X-band segments for detection, tracking, and targeting of ballistic missiles, will require significantly more power than the Aegis SPY-1 air-defense radar. Possible options are more powerful generator sets or additional generators. Raytheon, Lockheed Martin, and Northrop Grumman won Navy contracts last year for studies of AMDR design concepts.