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What Are The Big White Balls on Top of Cruise Ships? – Radome Guide

If you’ve ever been on a cruise ship, you may have wondered what the big white ball shapes are that you’ll find on the top of a lot of cruise ships.

They often resemble giant golf balls and you’ll usually find multiples on a cruise ship. They’re very obvious on Royal Caribbean, Carnival, and MSC cruise ships.

What Are The Big White Balls on Top of Cruise Ships? 

The big white balls on top of cruise ships are Radomes. A Radome is made up of two parts, a Radar and a Dome, hence the name Ra-dome. The dome covers the radar equipment protecting it from the weather and hiding it from guests. A radome can also include satelitte equipment.

Radomes contain rotating radar antennas and satellite discs, which will be constantly on the move. Radomes are designed to allow movement not only from the radar itself but also from the ship. The ship is subject to movements caused by weather and the ocean, so it is critical that the Radome is large enough to allow this movement.

The satellite equipment held within Radomes is used for communication, entertainment and navigation purposes.

cruise ship white balls on top radome

What are Radomes on Cruise Ships Used For?

The majority of cruise ships have more than one Radome. Cruise ships need a lot of equipment and also need to have backups available should one fail.

Radomes have multiple functions:

Radomes Provide Protection From The Weather

Radomes are used by cruise lines for multiple reasons, one of the most important being that they provide a weatherproof enclosure for any radar equipment.

Due to their location on the top deck of the ship, the equipment has to withstand rain, wind and any other bad weather elements such as sleet or hail.

Ice is particularly troublesome for any equipment and on some cruise routes, the cruise ship may experience snow and ice build-up. If the equipment housed within the dome was to get icy, this could cause big problems for the cruise line.

Protecting the equipment within with a Radome also means that the cruise line has to replace the equipment less often and therefore can save money by installing the domes.

Radomes Hide Radar Equipment

It’s unlikely that guests taking a cruise would appreciate looking at the radar equipment of a ship or having this in their photos.

Some of us may enjoy this but the majority would not. Personally I find it quite interesting but most prefer the look of the Radome covers.

The white round shapes of the Radomes are inconspicuous and unlikely to be noticed by the majority of cruisers. Even if you’ve cruised multiple times it’s unlikely that you’ve ever noticed the Radomes.

cruise ship white balls on top radomes

Radomes Protect Passengers

Having the radar equipment inside the Radome provides protection for the passengers of the ship. Some parts of radars rotate and keeping these hidden away in the Radome reduces the risk of any accidents.

Guests really shouldn’t be climbing on the radar equipment on the top of the cruise ship but people often do silly things.

What Are Cruise Ship Radomes Made From?

Radomes on cruise ships are usually made of fiberglass, a reinforced plastic using glass fibers, or a PTFE treated fabric.

Radomes on cruise ships are constructed with materials that very minimally reduces the electromagnetic signal transmitted or received by the antenna. The Radome casing is effectively almost transparent to the radio waves that pass through it.

Radomes are usually made by independent contractors, they work to certain standards but the equipment inside the Radome may change over time and the Radome is designed to allow this.

Are Cruise Ship Radomes Always Ball Shaped?

Radomes in general can be built in multiple shapes, they can be spherical shapes, geodesic shapes (incomplete spheres) or almost any other shape.

The most common shapes for radomes have a curved top. This shape is aerodynamic and because the wind on a ship can come from any direction, the curved edge of the radome is able to deal with this.

If you are cruising on a cruise ship where the radomes aren’t immediately obvious, this doesn’t mean that there aren’t any.

It means that they are likely another shape or hidden away.

cruise ship white balls radome

Why Are The Radomes on Cruise Ships White?

Radomes are usually white because white is the best color for keeping the contents of the Radar cool. A black or darkly coloured Radome would attract heat from the sun and could cause problems for the equipment inside.

Cruise lines are able to change Radomes but they usually last for multiple years. It isn’t an easy job to change a Radome as the video below shows:

Is It Just Cruise Ships Have That Have White Ball Shaped Radomes?

It isn’t just cruise ships that have Radomes which are white and ball shaped. Many other types of ships also have a very similar design.

Radomes are common in the airline industry too. The front ‘nose’ part of an airplane is a Radome protecting the equipment inside while providing an aerodynamic shape.

Other ships, helicopters and buildings will also have Radomes. Many buildings will have Radomes covering the satellite equipment on top of the roof.

Below is an example of a very large Radome from the Research Institute for High Frequency Physics and Radar Techniques in Germany.

FGAN Research Institute for High Frequency Physics and Radar Techniques
Photo: Gunther

Do All Cruise Ships Have Radomes?

All cruise ships have radars but not all have Radomes. Some ships may have their radar equipment out of site and some may leave it uncovered.

Some ships may have fake Radomes, although this is more common on Yachts and other ships as opposed to cruise ships.

Some shipowners may even install empty Radomes for security purposes in order to ‘trick’ other people into thinking that they have more equipment than they do. Similar to how some home owners install fake burglar alarms.

To Conclude:

The white ball shapes on top of cruise ships are Radomes. These are a combination of a radio equipment and a dome. Cruise ships have Radomes to protect radar and satellite equipment from the weather and to improve the appearance of the equipment for guests.

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