The USS Arleigh Burke (DDG-51) Destroyer entered service in 1991. Since then, over 50 ships of this class have been constructed. The production of these ships is slated to end in a few years with DDG-112, however these vessels will be serving in the US fleet for many years to come. They have received numerous upgrades over the years to pace new and emerging threats, yet the propulsion and electric power plant has remained largely unchanged. While this mechanical drive train has proven itself to be very reliable, the design suffers from poor fuel economy when compared to other warships. Consequently, there has been recent interest in exploring the addition of new technology such as a hybrid electric drive or "loiter motor" to improve the fuel efficiency of these ships. Most surface combatants spend very little of their underway time operating at full speed. A typical US warship spends over one third of it's underway hours at 12 Kts or less, using only a small fraction of it's installed power. Even operating the ship on a single gas turbine in "trail shaft" mode, results in very lightly loaded gas turbine main engines which are inherently inefficient. Numerous studies of all electric warships have shown sizeable fuel savings (20-40%) can be achieved over existing mechanical drive ships. Nevertheless, it has been shown to be financially impractical to convert an existing mechanical drive ship to an all-electric drive configuration due to the very high conversion costs. Hybrid drives, such as CODLAG/CODLOG plants, where an electric motor powers the ship up to a certain cruising speed and a mechanical drive system powers the ship above that speed, have been employed successfully in the Royal Navy's Type 23 Frigates. This type of propulsion plant would be much less costly to retrofit into an existing ship than an All Electric Ship (AES) plant and might possibly be cost effective, depending upon the details of the conversion cost and potential fuel savings to be gained in the remaining life of the converted ships. This paper will explore the operational concept for adding a hybrid electric (COGLOG) drive system to the existing ships, examine a number of technologies for implementing such a system and demonstrate the potential for significant fuel savings if such a system were fielded. Both fuel savings and Time on Station (TOS) improvements for implementing a hybrid drive on the DDG-51 are noteworthy and will be reviewed.
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