Cruise ships are some of the largest ships on the water by volume and by the number of people carried, they have every other ship beat. The world's largest cruise ship, Harmony of the Seas, can carry 6,780 guests and 2,100 crew members. Aside from the numbers, these ships are usually adorned in opulence. They are designed in such a way that stepping aboard feels like you are stepping into a world class hotel on land. As you can already guess, engineering these mega ships takes some innovative solutions and a lot of work. Before we get too far into the specialized engineering behind cruise ship construction, you can watch the entire process in the time-lapse video below.
Cruise ships are able to float because of their displacement of water. The physics behind why these massive ships can float has very little to do with the actual weight of the boat. The world's largest cruise ships can weigh upwards of 70 thousand tons, but as long as an equivalent amount of water is displaced, the ship will continue being buoyant.
Engineers who design cruise ships will rarely ever give concern to the overall weight of the boat when considering buoyancy. They will, rather, talk about the displacement of the ship. By coupling the proper amount of displacement for the ship with powerful engines and a streamlined hull, they can make maneuvering the ship even easier.
While these ships tend to be massive, their engineering sections are similar to ships and boats of smaller size. The parts used on these mega ocean liners are admittedly much bigger than their smaller counterparts, but the mechanics are roughly the same. Below, you can see a video that will walk through various parts of the engineering sections of a cruise ship. While it doesn't explain each section, you can begin to grasp the magnitude of work that it takes to keep everything running smoothly.
Displacing such a massive amount of water naturally means that it takes a lot of power and torque to get cruise ships moving. Older ships, and even some modern ships, will use large diesel engines to generate the necessary thrust. More modern ships will use gas turbines or diesel electric engines due to their efficiency and superior engineering. As the engine cranks, the power is transferred through a transmission and into the propeller shafts.
While the engines are typically used for propulsion and maneuvering of the ship, having a ship that carries so many passengers and recreational equipment means the power demand is high. For many ships, engineers choose to devote one of the many engines within the ships solely to electrical generation to supply the crew's needs.
Unlike ships of past, the propeller systems of modern cruise ships have a much greater directional versatility. This means that there are often several thruster propellers on the port and starboard side of the ships mounted in the aft. These allow for slight movements left and right. The main propellers are often mounted on rotational bearings that allow the engineers to move the thrust vector on an axis tangent to the bearing of the ship. This allows for these monstrously sized ships to maneuver in the same way that a much smaller vessel would. You can see some of this technology in the video below.
Opulence and Design
The backbone of cruise ships is their engineering prowess, but no one would want to take a vacation on them if they weren't filled with world-class luxury. Cruise ships are designed with the most expensive rooms on the outside of the ships and the least expensive rooms towards the interior with no windows. Fitting as many rooms into the ships is obviously a priority for cruise lines, but ultimately the allure of these ships are the public amenities on board.
Upper decks of cruise ships are usually filled with outdoor activities like pools, slides, zip lines. All of these activities are rooted in the fact that the engineering of the ship keeps it stable and safe. In many ways, the interior of cruise ships match or exceed hotels on land, all the while being held up by impressive maritime engineering. The video below will show you some features of the world's most luxurious cruise ship. You may want to turn your volume down before it starts, the sound quality is less than desirable.
They Keep Getting Bigger
If you have noticed anything about cruise ship trends, it is that they keep getting larger and larger. Propulsion technology and naval engineering capabilities have pushed the size of cruise ships to the extreme. Right now, the main limiting factor to cruise ship construction isn't that they can't get bigger, it's that only certain ports can handle such monstrous ships. From a monetary perspective, cruise companies want to make ships as big as possible to pack as many people on board and make the ride as smooth as possible. However, no one wants to take a cruise if you can't sail anywhere.
For cruise ships to continue getting bigger, we will need to see overhauls of many foreign ports in desirable destinations. The size and magnitude of many cruise ships nowadays make them harder to maneuver and handle from a port management perspective than large container ships. While it used to be the ship construction that held their size back, now, port construction will be the limiting factor for cruise ship construction.