The Largest Icebreaker in the World is the 50 Let Pobedy, this Icebreaker is 159 meters long (524 ft) and weighs 23,439 metric tons (25,837 tons). That’s peanuts next to the massive tankers and container ships it clears a path for, but it makes it the largest icebreaker in the world.
Nuclear Power – the only practical choice for Arctic icebreakers
In order to constantly provide enough power to shove that bulk up over mile after mile of ice, the 50 Let Pobedy (let’s just call it the Victory) runs a pair of nuclear reactors that generate a combined 55.2 megawatts (74,000 horsepower), which hits the water through three electric propulsion motors.
Why nuclear? Well, to put it simply, the fuel demands of the task at hand would be outrageous using any other power source. Burning diesel, the Victory would use more than 100 tons (90.7 metric tons) of fuel a day, and have a severely restricted range as a result. But running on nuclear power, she burns less than half a kilo (1 pound) of uranium even on the toughest day, at constant full power across 2.8-meter (9.2-foot) thick ice.
Image credits:Denizci Online/Flickr
With nuclear reactors on board, fuel stops become almost a thing of the past – a handy feature considering they work in extremely remote areas and have no other compelling reason to come in to port. In fact, the world record for endurance is held by one of Victory’s older cousins, the Arktika, which stayed in service on the ice for 357 days without entering a port once.
In fact, the specific needs of icebreaking vessels make them one of the only cases where nuclear propulsion is economically practical – barring nuclear submarines, which take advantage of the fact that the reactors don’t require oxygen to run. Nuclear reactors are more expensive to build than combustion engines, and enriched uranium doesn’t come cheap – but at the end of the day, by virtue of sheer volume, the fuel costs end up being much, much lower than an equivalent diesel engine.
No, the main issue is insurance. Imagine trying to insure one of these things, given the catastrophic and lasting damage that could occur in the “unlikely event” of an accident. Luckily, so far, there has not been a major incident.
Image Credits: Christopher Michel/Flickr
Icebreakers – almost unseaworthy outside their element
Icebreakers are an excellent example of a laser-focused vehicle. In the same way as a half-million dollar sports car can be a real pain around the speed humps and u-turns of the city, these goliaths of the Arctic are very poorly designed for operation outside their specific envelope.
The key element here is that rounded bow. A shape best suited to riding up on ice shelves and crushing them from above, it causes the ships to roll from side to side in the waves when sailing on open water, making for a very seasick ride for the crew.
When the seas come up (remember those 12-meter waves we spoke about earlier?) the shape opens itself up to another problem – where a typical pointed bow can pierce through an oncoming wave, greatly reducing its effect on the boat, the rounded bow of an icebreaker lets the water slam into it at full force.
These are certainly not comfortable vessels on the open water. Even once on the ice, the crew has to deal with the constant jarring and shuddering of ice breaking beneath the boat, as well as the low, constant rumble it produces.
A relatively new development in engine design, however, might put dedicated icebreakers out of service for all but the thickest surfaces.
Double-acting reversible tankers – ships that go both ways
In the 1990s, a new class of propulsion device was designed. Previously, most ships had a fixed propeller system which could run either in forward or reverse, and some sort of rudder arrangement for steering, but the development of the azimuth thruster pod instantly changed the state of the game.
These hardy propulsion pods hung under the ship’s hull, housing a motor and propeller, with the ability to rotate each pod 360 degrees to provide thrust in any direction. This makes the ships much more maneuverable.
Azipod rotating thrusters, fitted to a ship under construction
It turns out, the pods also have a special advantage in icebreaking applications. These “Azipod” propulsion units typically have their propellers facing forwards and operate in a pulling motion to take advantage of an untroubled stream of water. When you turn them 180 degrees and run the ship backwards, it turns out that the intense agitating power of the Azipods can actually help break ice from underneath.
In fact, ships running astern (backwards) with Azipods leading the way have proven to be significantly more efficient at breaking ice than ships with the same bow shape running with rear propulsion.
This means that you can build ships with an icebreaking bow and Azipods at the rear, and a regular wave piercing bow at the front – double-acting reversible ships that can efficiently drive forward in the open sea without any of the roll effect of a dedicated icebreaker, but that can turn tail and run butt-first if they run into sea ice and need to smash through it. They can perform both jobs with high efficiency, while carrying cargo.
Here’s an example, the MT Tempera – one of the first double acting cargo ships. Here she is running ahead in open water:
MT Tempera, one of the new class of double acting reversible ships, going backwards to act as an icebreaker
These double-acting ships, many of which are now in operation, more or less render the dedicated icebreakers obsolete where the ice is only a meter or a meter and a half thick – which opens up a lot of shipping routes. But the big boys like the 50 Let Pobedy are still needed when the going gets really tough with ice beyond 2 meters thick.
I hope you’ve enjoyed this quick overview – the icebreaker and double acting ship class is such an impressive answer for such a specific problem in such a harsh environment that we thought it was worth a feature.