CODOG

CODOG
Alureiter · Public domain · source
Name	CODOG
Type	Combined diesel or gas
Inventor	--
Country	--
Date	--
Usage	Marine propulsion

CODOG

Combined diesel-or-gas (CODOG) is a marine propulsion arrangement that permits a ship to use either diesel engines or gas turbines to drive propellers but not both simultaneously. It is employed to balance fuel economy at cruising speeds with high power for sprinting, and has been installed on warships and some large civilian vessels. The architecture sits alongside other marine systems such as combined diesel and diesel, combined diesel and gas turbine with electric transmission, and combined gas and gas, and has influenced naval architecture and fleet operations worldwide.

Overview

CODOG systems enable platforms to alternate between medium-speed diesel engines and high-power gas turbines for shaft propulsion. Designers and navies including the Royal Navy, United States Navy, Imperial Japanese Navy, French Navy, Royal Australian Navy, and German Navy have evaluated CODOG for frigates, destroyers, corvettes, and patrol vessels. Shipyards and firms such as BAE Systems, DCNS, Fincantieri, ThyssenKrupp Marine Systems, and Navantia have integrated CODOG into export designs alongside alternative arrangements from manufacturers like General Electric, Rolls-Royce Marine, MTU Friedrichshafen, and Wärtsilä. CODOG complements combat systems made by Lockheed Martin, Raytheon Technologies, Thales Group, Saab Group, and Northrop Grumman when endurance and burst speed requirements must be reconciled.

Design and Operation

A CODOG propulsion train typically comprises diesel engines connected through clutches and gearboxes, and gas turbines coupled by separate clutches, converging on common reduction gears that drive fixed-pitch or controllable-pitch propellers. Naval architects at institutions such as Newcastle University, Massachusetts Institute of Technology, University of Southampton, and Chalmers University of Technology examine hydrodynamics and machinery layout to optimize shafting, gearbox loads, and acoustic signature for platforms like the Type 23 frigate, MEKO series, or Karel Doorman-class frigate. Control systems from suppliers like Siemens, ABB, and Honeywell manage mode selection, clutch engagement, and automated transition sequences. Operational constraints require procedures from admiralties such as the Royal Netherlands Navy and Canadian Forces to avoid engaging diesel and gas turbines simultaneously; integrating auxiliary systems and electrical generation often involves cooperation with firms including Siemens Energy and MAN Energy Solutions.

Applications and Use in Naval Vessels

Navies have applied CODOG to ships requiring fuel-efficient cruising with occasional high-speed dash capability. Examples include frigates, corvettes, offshore patrol vessels, and some guided-missile platforms used by the Royal Norwegian Navy, Hellenic Navy, Turkish Navy, Brazilian Navy, and Polish Navy. Navies operating in littoral zones—such as the United States Coast Guard and Royal Canadian Navy—assess CODOG against CODAG and CODLAG when mission profiles include long transits and rapid interception. Integration with weapons suites by companies like MBDA, Rafael Advanced Defense Systems, Bharat Electronics Limited, and sensors from Sperry Marine or Kongsberg Gruppen influences hull form, displacement, and endurance. Ship classes featuring CODOG or related arrangements have participated in multinational exercises such as RIMPAC, NATO BALTOPS, Exercise Malabar, and Exercise Cutlass Express.

Advantages and Disadvantages

Advantages of CODOG include fuel efficiency at patrol speeds, simpler gearbox arrangements compared with combining power sources simultaneously, and reduced maintenance complexity relative to full hybrid electric systems—attributes valued by operators like the Royal New Zealand Navy and Republic of Korea Navy. Disadvantages include limitations on continuous high-speed operation due to gearbox thermal loads, the need for robust clutch systems developed by manufacturers such as ZF Friedrichshafen and Renold, and reduced redundancy compared with combined transmission systems used by Japan Maritime Self-Defense Force vessels. Acoustic and infrared signatures influenced by engine selection affect detectability against platforms employing sonar suites from Lockheed Martin Undersea Systems or Atlas Elektronik and infrared sensors by FLIR Systems; logistical footprints and fuel types tie into supply chains managed by defense ministries such as those of United Kingdom, France, India, and Italy.

Historical Development and Notable Implementations

The evolution of combined propulsion traces through twentieth-century innovations in gas turbine development by firms like General Electric, Pratt & Whitney, and Rolls-Royce Holdings and diesel technology from Sulzer, Birkitt, and MAN SE. Cold War-era experimentation by the Soviet Navy and NATO navies led to fielded CODOG installations on post‑Cold War frigates and corvettes; notable implementations include classes built by Vosper Thornycroft, Blohm+Voss, Yantar Shipyard, and Garden Reach Shipbuilders & Engineers. Specific ship classes associated with similar combined systems—while not invoking variants in naming—appear in the fleets of the HMS Neptune-era designs, Richelieu-era modernization efforts, and export programs delivered to countries such as Chile, Indonesia, Malaysia, and Philippines. Trials, refits, and modernization programs managed by defence contractors including BAE Systems Surface Ships and Indra Sistemas have continued to refine CODOG gearboxes, clutch control, and integration with modern combat management systems.

Category:Ship propulsion