Which of the following lists three propulsion system types used on ships?

• A. Gas turbine, diesel engine, and steam turbine
• B. Diesel engine, steam turbine, and electric motor
• C. Gas turbine, electric motor, and hydraulic drive
• D. Nuclear reactor, diesel engine, and gas turbine

Answer: (A)

propulsion systems on ships are categorized by the main prime mover that drives the propeller. The three most common prime movers are diesel engines, steam turbines, and gas turbines. Each brings different strengths: diesel engines are robust and efficient for steady, long-duration use; steam turbines can deliver very high shaft power for large vessels; and gas turbines offer high power-to-weight and quick response for fast ships. Together they form the standard trio of propulsion options you’ll encounter on ships.

Electric motors show up in propulsion systems, but they’re usually part of an electric-drive setup where a prime mover (diesel, gas turbine, or steam turbine) runs a generator to power the motor. They’re not considered one of the primary propulsion plant types in this context. Nuclear propulsion exists but only on a limited class of ships, so it isn’t part of the typical three-type list.