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  • Writer's pictureSarah Whiteford

How are ships launched?

It’s Fun Fact Friday and we’re going over ship launching!

If you’ve ever wondered how huge ships get into the water, we’ll cover all the launching methods from the slow and boring to the fast and crazy, with videos!

Ship construction can take months for smaller vessels and years for larger ships. Costs can go into the hundreds of millions for large transport vessels and dynamically positioned ships. After all that hard work and money spent, how do they get into the water? Smaller ships can be lifted and set down in the water, sure, but what about the big ones? Large vessels can be over 1000 feet long and have a deadweight of over 200,000 tons. Let’s take a closer look at how different types of ships are launched.

There are four main types of launching processes:

  1. Gravitational

  2. Floating-out

  3. Mechanical

  4. Airbag

Gravitational launching

We’ll cover gravitational launching first, which is basically letting the vessel slide into the water under the force of gravity. A ramp is used to slide the ship into the water, and varies depending on the direction and type of method used, being further divided into three types:

Longitudinal oiled slideway

Longitudinal steel-roller slideway

Side oiled slideway

Image Credit: We are the Mighty

One of the oldest methods of ship launching, longitudinal oiled slideway type launching uses a lubricated slide system that the ship slides down to enter the water. Oil or wax is used to help the process move smoothly. This method is relatively simple and doesn’t require special equipment, with the downsides being the lubricant gets into the water, and a lot of pressure can be put on the front of the ship as it launches.

Longitudinal steel-roller slideway launching is just like oiled slideway, but steel rollers are used instead of a lubricant to facilitate movement. A steel plant is used on the wooden slide to help in the sliding and protect from the steel balls. A simple net bag is located at the end of the slide to catch the steel balls so they can be reused later. It’s a very effective method but with higher installation costs.

Slide oiled slideway launching is a very common method for launching large ships. The slideway can extend into the water or stop at the water’s edge, where the ship falls into the water and must gain steadiness by itself. This launching requires a strong ship with excellent stability. Extra care has to be taken as this method is usually used in narrow waterways, and can flood nearby roads and lots or damage the ship if it hits the shore or a wall. Despite the dangers to the ship, this is also by far the coolest method to watch! Check out some of the sideway launches in the video below:

Video credit: marineinsight

Floating-out launching

With floating-out type launching, ships are built in a dry-dock. Once the construction is complete, the dry dock is simply filled with water until the ship can be floated out. This is one of the most common methods used nowadays: it’s easy on the ship and very safe, but quite expensive. On the other hand, I have to agree with We are the Mighty, it would be fun to see a huge cruise ship just slide sideways into the water with a huge splash…”This is a much less violent way of launching a ship than throwing it over the side of the dock, but it's also way less cool. Think about that — you could just chuck the Disney Fantasy directly into the Caribbean...”

Image Credit: We are the Mighty

Mechanical launching

Mechanical launching is pretty straightforward: set the ship in the water gently. This method is not without its dangers as it requires a crane or other lifting system, but is a commonly used method for getting small ships launched. For larger ships, this really isn’t an option due to the sheer size and weight of the vessels.

Air bags

Air bags are a safe method for launching many types and sizes of ships. Rubber air tubes are placed under the ship, which then are used to guide the ship into the water with gravity. It doesn’t require a slideway or the associated complexities and costs that go with it.

If you want to see some crazy ship launches, check out this longer video:

Video credit: HD1080ide

Happy Fun Fact Friday!


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