Combined gas turbine and gas turbine (COGAG) is a type of propulsion system for ships using two
gas turbine
A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directio ...
s connected to a single
propeller shaft
A drive shaft, driveshaft, driving shaft, tailshaft (Australian English), propeller shaft (prop shaft), or Cardan shaft (after Girolamo Cardano) is a component for transmitting mechanical power and torque and rotation, usually used to connect ...
. A
gearbox
Propulsion transmission is the mode of transmitting and controlling propulsion power of a machine. The term ''transmission'' properly refers to the whole drivetrain, including clutch, gearbox, prop shaft (for rear-wheel drive vehicles), differe ...
and
clutches allow either of the turbines to drive the shaft or both of them combined.
Using one or two gas turbines has the advantage of having two different power settings. Since the
fuel efficiency of a gas turbine is best near its maximum power level, a small gas turbine running at its full power is more efficient compared to a twice as powerful turbine running at half power, allowing more-economical transit at cruise speeds.
Compared to
combined diesel and gas (CODAG) or
combined diesel or gas
Combined diesel or gas (CODOG) is a type of propulsion system for ships that need a maximum speed that is considerably faster than their cruise speed, particularly warships like modern frigates or corvettes.
For every propeller shaft there is ...
(CODOG), COGAG systems have a smaller footprint but a much lower fuel efficiency at cruise speed and for CODAG systems it is also somewhat lower for high speed dashes.
List of COGAG ships
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guided-missile destroyer
A guided-missile destroyer (DDG) is a destroyer whose primary armament is guided missiles so they can provide anti-aircraft warfare screening for the fleet. The NATO standard designation for these vessels is DDG, while destroyers who have a prim ...
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Indian Navy
The Indian Navy is the maritime branch of the Indian Armed Forces. The President of India is the Supreme Commander of the Indian Navy. The Chief of Naval Staff, a four-star admiral, commands the navy. As a blue-water navy, it operates si ...
)
* (aircraft-carrier) (
Indian Navy
The Indian Navy is the maritime branch of the Indian Armed Forces. The President of India is the Supreme Commander of the Indian Navy. The Chief of Naval Staff, a four-star admiral, commands the navy. As a blue-water navy, it operates si ...
)
*
Type 22 frigate
The Type 22 frigate also known as the ''Broadsword'' class was a class of frigates built for the British Royal Navy. Fourteen were built in total, with production divided into three batches.
Initially intended to be anti-submarine warfare fri ...
(Batch 3) (
Royal Navy
The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against ...
)
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Royal Navy
The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against ...
)
* (
Italian Navy)
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Japan Maritime Self-Defense Force
, abbreviated , also simply known as the Japanese Navy, is the maritime warfare branch of the Japan Self-Defense Forces, tasked with the naval defense of Japan. The JMSDF was formed following the dissolution of the Imperial Japanese Navy (IJN) ...
), and subsequent destroyer classes
* (
Japan Maritime Self-Defense Force
, abbreviated , also simply known as the Japanese Navy, is the maritime warfare branch of the Japan Self-Defense Forces, tasked with the naval defense of Japan. The JMSDF was formed following the dissolution of the Imperial Japanese Navy (IJN) ...
), helicopter carrier
* (
Japan Maritime Self-Defense Force
, abbreviated , also simply known as the Japanese Navy, is the maritime warfare branch of the Japan Self-Defense Forces, tasked with the naval defense of Japan. The JMSDF was formed following the dissolution of the Imperial Japanese Navy (IJN) ...
), helicopter carrier
*
Type 055 destroyer
The Type 055 destroyer (NATO/ OSD Renhai-class cruiser) is a class of stealth guided-missile destroyers ( guided-missile cruisers per NATO/OSD standard) being constructed for the Chinese People's Liberation Army Navy. It is a multi-mission desi ...
(
People's Liberation Army Navy)
* (
Russian Navy)
* (
Republic of Korea Navy
The Republic of Korea Navy (ROKN; ko, 대한민국 해군), also known as the ROK Navy or South Korean Navy, is the naval warfare service branch of the South Korean armed forces, responsible for naval and amphibious operations. The ROK Navy i ...
)
* (
Royal Norwegian Navy
The Royal Norwegian Navy ( no, Sjøforsvaret, , Sea defence) is the branch of the Norwegian Armed Forces responsible for naval operations of Norway. , the Royal Norwegian Navy consists of approximately 3,700 personnel (9,450 in mobilized state, ...
)
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United States Navy
The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...
)
* (
United States Navy
The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...
)
*{{Sclass, Wasp, amphibious assault ship, 1 (
United States Navy
The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...
)
Marine propulsion