A modern cruise ship’s average speed is 20 knots (23 miles per hour), with maximum speeds reaching 30 knots (34.5 miles per hour).
Top speeds of the large cruise ships carrying a thousand or more passengers do not reach much more than 26 knots (30 miles per hour). The largest passenger ship globally, Royal Caribbean’s Symphony of the Seas, has a maximum speed of around 25 knots (29 miles per hour).
You will typically see ship speeds given in knots (knots-per-hour). The most advanced aircraft carrier in the U.S. fleet, the USS Gerald R. Ford, has a speed that tops out around 35 mph. For comparison, Usain Bolt’s human speed record is 27.8 mph.
In the grand scheme, a cruise ship’s top speed is mostly irrelevant because they will almost always sail at their cruising speed, usually around 20 mph. Emergencies – a passenger who requires hospitalization, another ship in distress, or an approaching storm – are usually the only reasons a cruise ship will go its expensive-gas-guzzling full-throttle.
Do Cruise Ships Go Faster at Night?
Even though cruise ships are huge, they can move fast. They do most of their traveling late at night while the passengers are sleeping. That is why we all sleep so well; the ship is rocking back and forth at full steam ahead. On longer cruises, the cruising speed might even be lowered to time arrival, so it is not in the middle of the night.
Knots are derived from nautical miles. Navigation at sea was historically done with trigonometry, it still is, but we leave the math to the computers. Understanding that the earth was a sphere, navigators divided it up into 360 degrees with corresponding latitude and longitude lines. The equator is considered zero degrees. Extending out to the north and south poles are 180 and -180 degrees, respectively, with the prime meridian and the longitudinal lines extending east and west from it.
Can a Cruise Ship Outrun a Hurricane?
If a storm is threatening one area of the Caribbean or Atlantic, cruise lines will reroute their ships to a different destination. Yes, cruise ships can typically “outrun” a hurricane because storms tend to move about 8 to 10 knots, while ships can attain speeds of up to 22 knots or more.
A nautical mile is 1/60th of a degree. Why divide by 60? Because there are 60 minutes in an hour. By measuring the speed like this, mariners can express their per-hour speed in terms of their movement along the earth’s latitude and longitude lines. If you start at the equator and travel 60 knots per hour due north, that means in one hour, you will be at a latitude of one degree north.
Generally, one nautical mile is equivalent to 1.15 miles.
A top speed of 29 mph is 33.4 knots
An average cruising speed of 20 mph is 23 knots
Why Are Cruise Ships So Slow?
Speed used to be a premium for ocean-going vessels. Owning the fastest ship was something to brag about. In 1952 the fastest record for a passenger ship crossing the Atlantic was set by the liner United States. It covered the 3,521-mile distance between New York City and Le Havre, France in 82 hours and 40 minutes, or three-and-a-half days, clocking in with an average speed of 42.6 mph.
That earned it the Blue Riband, a distinguishment reserved for the fastest Atlantic crossing of a passenger ship in regular service.
Before the advent of airplanes, a fast ship meant spending fewer days, or weeks, on unpleasant and treacherous ocean crossings. Today’s airplanes have made speed an obsolete factor for passenger ships. Perhaps this is best symbolized by the United States; it set the record in 1952, and no one has bothered to challenge it since.
And the faster alternatives that emerged in the middle of the 20th century have only improved going into the 21st.
While part of this has to do with incentive, another part has to do with natural laws’ limits. Because of the fluid and displacement dynamics of large vessels in the water, every extra mile-per-hour gained in speed beyond about 25 mph requires an exponential increase in the amount of power, and by extension, fuel.
Because cruise ships are so massive, the only way they can displace enough water to stay afloat is by having a considerable amount of their hull, about 30 feet worth, submerged. Having this much of the hull underwater also has the advantage of making cruise ships relatively stable in rough seas.
The disadvantage of this design is that ships with significant displacement hulls cannot go fast. When you see a speedboat shoot by you on the lake, you will notice the entire front of its hull is planing above the water. But if you were to dive under a speedboat when it was stopped, you would see that hardly a foot of it is submerged. That is why speedboats can glide over the water and cruise ships cannot.
Do not underestimate a cruise ship’s average speed of 20 miles per hour. For a vessel that can maintain that speed without needing to slow down, over one day, that is 480 miles, and over a week, that is 3,360 miles.
Real-Life Modern-Day Speeds
Here is a look at some real cruise itineraries to demonstrate how fast cruise ships are sailing.
Norwegian Cruise Line has a route from New York City to Bermuda to Port Canaveral in Florida. Eager guests sail aboard the 2,394-maximum-passenger-capacity Norwegian Pearl, built in 2006 complete with two main propeller engines and three bow thrusters.
It departs New York at 8 pm and arrives two days later at 9 am in Bermuda’s Royal Naval Dockyard, a 36-hour voyage. Passengers set sail from Bermuda the next day at 12:30 pm and arrive at Port Canaveral two days later at 7 am, a 43.5-hour voyage.
That works out to:
New York City to Bermuda (771 miles) – 21.4 mph average speed
Bermuda to Port Canaveral, Florida (979 miles) – 22.5 mph average speed
Princess Cruises offers a 111-day round-the-world cruise beginning and ending in Fort Lauderdale aboard its Pacific Princess. Built in 1999, she can hold a maximum of 826 passengers and is driven by two enormous propellers.
While circumnavigating the globe, the ship has a Pacific crossing from Los Angeles to Honolulu – more than five days at 133 hours – and an Atlantic crossing from Walvis Bay, Namibia, to Natal, Brazil, which takes over eight days at 200 hours.
This comes out to:
LA to Hawaii (2,559 miles) – 19.2 mph average speed
Namibia to Brazil (3,515 miles) – 17.6 mph average speed
Engines That Pack a Punch
Cruise ship engines are massive. The standard design is two or even three main engines at the rear of the ship. Many ships have additional bow thrusters that help the front of the ship move left or right. An increasingly standard main-engine thrust design is to have propellers capable of rotating 360 degrees to give ships extra maneuverability.
Just one of the main propeller engines of a cruise ship can weigh 250 tons. That is how much each weighs on Royal Caribbean’s Symphony of the Seas, the largest cruise ship ever built. And each of those five-blade propellers puts out 20 megawatts or brute force. That is enough energy to power a medium-sized city, or if you prefer truck analogies, 26,820 horsepower in a single-engine.
You might be surprised to learn that right now, most of the largest cruise ships are propelled by electric engines, including the Symphony of the Seas. But do not get the idea these are ocean-going Teslas.
These engines are known as diesel-electric; the electricity that powers them is made on-board with diesel-powered generators. Symphony of the Seas’ 16-cylinder diesel generators are each four-stories high. Together, if they are at full power, they can burn through 66,096 gallons of fuel per day. That is why the gas tanks on the giant cruise ships can carry up to two million gallons.
Environmental Pressures on Cruise Ship Engine Design
Environmental issues are increasingly at the forefront of policy discussion. When you buy an airplane, train, or bus tickets today, you will often see a box to check so you can pay a few extra dollars and offset your carbon footprint.
The cruise industry has not been spared from the spotlight on this issue, especially its diesel-hungry luxury liners. Some cities in Europe are already laying down plans to ban diesel cars for their offending sulfur dioxide and particulate matter. It does not help that diesel used in shipping is worse on these fronts than automobile diesel. This has caused some previously out-of-favor ship engines like gas turbines to start making a comeback.
Gas turbine engines are efficient. They benefit from the power they produce as internal combustion engines and create additional power by recycling hot post-combustion gasses for extra kinetic and thermal energy.
The kinetic energy of the engine’s internal combustion portion can be used to turn the ship’s propellers. The captured vent gas is channeled through additional turbines that spin to generate electricity. Finally, when the hot exhaust leaves the engine’s internal portions, it can be used in steam-powered drive shafts for additional mechanical energy.
Both types of engines, diesel-electric and gas turbines, can generate comparable amounts of horsepower. While gas turbine engines may be more complicated to maintain and costly, market trends favoring the environment make the prospects for gas turbines more realistic.
Some companies are already starting to market combination engine packages for cruise ships. A diesel-electric motor drives the ship’s propellers, and its electricity is generated by gas and steam turbines.