Combined gas or gas

A COGOG drive ( for combined gas or gas ) is a marine propulsion concept where two different gas turbines can be connected to the drive shafts. A highly efficient, lower-power turbine is used for cruising, while a more powerful turbine for high speeds is employed.

As with COGAG drive is the advantage in reduced fuel consumption, since a small turbine at 100% power less fuel consumed than twice as powerful, which runs at 50 % power. In contrast to COGAG concept, the turbines are not parallel here for marching and fast speed, but always used only individually. Thus the complicated gear assembly of COGAG drive falls away, the price is a higher overall weight of the drive at the same maximum power.

COGOG comes before all the war ships. Examples are the frigates of the Dutch Kortenaer class and the destroyer of the Canadian Iroquois class.