How Are Cruise Ships Powered?

The beauty, luxury and, quietness of most cruise ships can be awe inspiring when cruising on one or even just watching from the dock. They look so majestic at sea and seem to maneuver their giant hulls dock side with little effort.

What goes on below the main decks, in the engine room is what is even more amazing. How do these huge ships move seemingly effortlessly through the sea?

Most of the older cruise ships use Diesel engines. These engines are connected to a Gear Box or Transmission, this reduces the RPM coming from the engine to the shaft. The shaft runs through the hull (covered by a packing gland or seal ring to keep the water on the outside of the boat) and on the end of the shaft is the propeller or often called the screw. The screw is shaped very similar to an airplanes propeller, but turns slower and has increased pitch or bends on the blades, because for a ship the screw is meant for power not speed.

Some of the newer Cruise ships use Gas Turbine Engines; these give off fewer emissions and are smaller in size without losing horsepower. The gas turbine engine generates heat that is turned into electrical power. For this to happen compressed air is ignited in a combustion chamber, where the hot air is forced over a turbine. The turbine is used to drive a shaft which spins electrical generators, and these generators spin the ships shaft and wheel as well as provide electrical power to the vessel.

There are also Diesel Electric Engines, these are very similar to the gas turbine engines except for they use output shafts rather than turbines to create electrical power to turn the shaft and screw.
The newest of the cruise ships have what is called Azimuth Thrusters. These are pods or housings that are similar in looks to a cort nozzle. These pods house the propeller and can spin a complete 360 degrees. This completely eliminates the need for rudders because you can know maneuver by turning the screws. It also gives the ship increased and quicker stopping power because you're not changing the direction of the screw like on conventional shafts. The Azimuth Thruster uses less fuel and decreases exhaust emissions. They can also be powered by either Gas Turbine or Diesel-Electric engines.
The technology has come extremely far for marine engines in the last decade. Cruise ships have gone from single screw coal fired steam engines that plumed black smoke where ever they went, not to mention how loud they were. To today's engines that barely emit any exhaust and cannot even be heard above decks.