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How do cruise ships turn around?

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📓 The short answer

Cruise ships turn around in tight spaces using a combination of bow thrusters, which move the front of the ship sideways, and azimuth thrusters, which rotate 360° to steer and propel the ship. These systems allow precise movements without relying heavily on tugboats.

📚 The long answer

Cruise ships are often called "cities on the sea" because of their massive size and population. The biggest cruises in the world are over 1,000 ft (305 m) in length and carry 5,000-7,000 passengers.

So when these sea-ties need to dock in narrow ports, how exactly do cruise ships turn around?

Cruise ships maneuver tight turns primarily thanks to two components: bow thrusters and azimuth thrusters.

Bow thrusters push the front of the ship from side to side

Bow thrusters are smaller propellors mounted sideways at the bow (front) of the ship. They are primarily used when the ship is going at low speeds in coastal waters or while entering or leaving a port, especially in challenging conditions like strong currents or high winds.

The bow thruster pulls in water from one side of the ship and expels it on the other, pushing the bow in the opposite direction. They can be operated in both directions, from port to starboard (left to right) and vice versa.

Because bow thrusters enable precise sideways movement when docking, they often reduce or eliminate the need for tugboats in port.

Azimuth thrusters can rotate 360° to propel and navigate ships

For a long time, ships were pushed through the water with fixed propellors and turned using rudders. Newer ships now use a combination of these systems with a type of rotating propeller called an azimuth thruster.

Azimuth thrusters are named after the term "azimuth," which refers to a horizontal angle measured from a cardinal direction, like 90° from north being east. But they're more commonly referred to as "azipods," for the same reason why tissue is often called Kleenex.

Traditional propeller and rudder systems work well for navigation in open waters. However when big ships come into port, they may need to turn quickly and even reverse, which is typically where tugboats would come in.

With azipods, cruise ship captains can control each thruster independently to make precise turns and even "crabwalk" a ship sideways with the help of bow thrusters.

Azipods also differ from traditional propellors because they are typically positioned "backwards" so that they pull water instead of push it. This configuration allows the propellor to hit the water when it hasn't been disturbed by the pod structure, which makes the thrust more efficient.

As you can see, the azipods on big ships are enormous. On the Queen Mary 2, the largest ocean liner ever built, each azipod weighs as much as a Boeing 747 and has a power output of 21.5 megawatts.

--- Thanks for reading this week's newsletter! If you have any thoughts, questions, or favorite GIFs, my inbox is always open. Just hit reply to send me a note! :) ​ All my best, Caitlin ​Click here to read five facts about Caitlin​

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​Sources for this week's newsletter​

🌐 Wikipedia article of the week

​Dazzle camouflage​

"Dazzle camouflage, also known as razzle dazzle (in the U.S.) or dazzle painting, is a type of ship camouflage that was used extensively in World War I, and to a lesser extent in World War II and afterwards.... [It] consisted of complex patterns of geometric shapes in contrasting colors interrupting and intersecting each other.

Unlike other forms of camouflage, the intention of dazzle is not to conceal but to make it difficult to estimate a target's range, speed, and heading."

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👀 Catch up on other curious questions

• ​Is peanut butter a liquid?​​
• ​How are speed limits determined?​​
• ​Why is a second called a second?​​

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