Large cruise ships typically host 1,800 passengers or more, plus 800 staff. Remarkably, many of these massive structures—three football fields long and 14 stories high—can deftly turn on a dime, spin 360 degrees, even mosey sideways.
For years big ship propulsion had a standard configuration: a propeller in the rear with a rudder behind it to steer. But increasingly, they are being equipped with an innovative propulsion system called the Azipod, made by ABB Oy in Finland. This gigantic electric motor and propeller hang underneath the back of the ship from a hefty swivel that allows the rig to rotate 360 degrees, driving the ship in any direction. Smaller bow thrusters, installed laterally under the waterline in the nose of the hull, help to push the boat from side to side near docks or obstructions.
The Oosterdam, owned by Holland America Line, is typical of big ocean liners. Five diesel engines, one gas turbine and two Azipods move the floating high-rise swiftly and smoothly. The power comes at a price: 90 gallons of heavy fuel oil are consumed per mile when running at moderate speed on three engines; up to 150 gallons are needed per mile when all five engines are bucking headwinds and swells at top speed. “Every day I recalculate the fuel figures and adjust operations” to maximize fuel efficiency, said Willem Dullaert, chief engineer of the Oosterdam when this writer was onboard earlier in the year. For example, ballast, fuel or freshwater might be pumped from tank to tank to alter how the craft rides.
On supporting science journalism
If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.
“Each ship has a most economical draft,” notes Cees Deelstra, Holland America’s director of nautical operations. “We even consume fuel and water out of different tanks to perfect the trim.” In calm seas, about two thirds of the power generated moves the ship and the rest caters to its inhabitants’ desires.
The scale of equipment in the bowels of such boats is impressive. An adult can literally walk inside an engine, which occupies the volume of a suburban living room. Evaporators the size of small cars can each desalinate almost 140,000 gallons of seawater a day to provide freshwater for passengers and staff. Engines are cooled with closed-loop freshwater systems that, in turn, are cooled by adjacent closed loops of seawater. Cruise lines used to give patrons who asked brief tours of their ships’ guts, but sadly, concerns about terrorism have ended the inside look on most excursions.
Did You Know ... GREENER BOAT: Newer cruise ships process “graywater” from showers and sinks into clean water for various operations. So-called blackwater from toilets is also treated; cleansed water is discharged at sea, and solidified waste is brought ashore. Some operators are also experimenting with smokestack scrubbers to filter engine emissions.
LAW ON THE SEA: As soon as passengers step onto a ship, they enter into the legal system of the owner’s home country. For example, the Oosterdam sails under the Dutch flag, so all people onboard are subject to Dutch law.
HIDDEN CREW: For a weeklong trip, the Oosterdam sails nine navigation officers, 17 engineers, an environmental officer, an information technology officer, an electrician, a carpenter, a locksmith, an upholsterer and a tilesetter. Passengers are pampered by 400 room stewards and 400 waitstaff—all from Indonesia and the Philippines; these employees work seven days a week for 10 months a year, sleep two to a room and move about via hidden stairways.
Inside The Ship:
Note: This story was originally published with the title, "Working Knowledge: Nimble Skyscrapers at Sea".
