An icebreaker is a special-purpose ship designed to move and navigate through ice-covered waters, and provide safe waterways for other boats and ships. For a ship to be considered an icebreaker, it requires three traits most normal ships lack: a strengthened hull, an ice-clearing shape, and the power to push through sea ice.
Icebreakers clear paths by pushing straight into ice pockets. The bending strength of sea ice is so low that usually the ice breaks without noticeable change in the vessel’s trim. Custom-built to the point of being almost unseaworthy on the open waves, these goliaths smash their way through 3-meter (10-foot) thick ice crusts to create viable pathways for other vessels.
A Brief Overview
The ice breakers have long served to keep shipping transport routes open in the Arctic. In the mid 1800s, they were powered by steam. In the 1930s, they transitioned to diesel, and in the 1950s, diesel-electric. Today, the industry boasts of nuclear-powered icebreakers. This is how these modern marvels function:
- Extremely powerful engines propel the ship on top of the ice.
- The massive ship’s weight allows it to break through ice up to 10 feet thick.
- The double hull is rounded to direct the ice fragments away from the ship so it, and often the ship following it, has a clear path forward.
In cases of very thick ice, an icebreaker can drive its bow onto the ice to break it under the weight of the ship. Because a buildup of broken ice in front of a ship can slow it down much more than the breaking of the ice itself, icebreakers have a specially designed hull to direct the broken ice around or under the vessel.
The external components of the ship’s propulsion system (propellers, propeller and shafts) are at a greater risk of damage than the vessel’s hull, so the ability of an icebreaker to propel itself onto the ice, break it, and clear the debris from its path successfully is essential for its safety.
Evolution of Nuclear Powered Ice-Breakers
The fuel demands for running an ice breaker are enormous. Burning diesel, a standard VLCC 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, the same vessel 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.
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.
Ice-breaking vessels have been built since the 1830s. It is interesting to note that while today’s enormous icebreakers generally use nuclear power to generate the immense thrust needed to power through the ice fields, in other ways, the design hasn’t changed too much for nearly 200 years.
Hull – The Lifeline of an Ice Breaker
When the ship hits ice, the smooth bow causes the front end of the ship to ride up on top of the ice, so the vessel’s immense weight can then crush it from above. The hull is shaped to push the crushed ice out of the way of the ship’s propulsion system, where it could cause significant damage.
The hull is strengthened and reinforced to deal with the additional stress it has to handle, and it’s also coated with a low-friction solution that makes it easier to glide over the ice rather than catching or grabbing as it rides over.
Arktika-class icebreakers have a double hull, with the outer hull being approximately 48 mm thick at the ice-breaking areas and 25 mm thick elsewhere. There is water ballast between the inner and outer hulls which can be shifted to aid icebreaking.
As ice pressures vary between different regions of the hull, the most reinforced areas in the hull of an ice-going vessel are the bow, which experiences the highest ice loads, and around the waterline, with additional strengthening both above and below the waterline to form a continuous ice belt around the ship.
Why Ice-Breakers are Essential
The Arctic North end of Russia is believed to hold as much as a quarter of the entire world’s oil deposits, hidden in one of the toughest and least hospitable environments on the planet. Getting to this and then transporting it back to refineries is a monolithic task that requires the most advanced and robust technology and machinery.
Some of the world’s richest reserves are buried beneath the beds of the Berents sea, north of Russia and well into the Arctic Circle. It’s estimated that this area holds somewhere around a quarter of all the oil reserves in the world.
But the same area that gets no sun at all for at least one day every year, and which is so cold that the sea itself freezes over with 2-meter (6.5-foot) thick ice for more than two thirds of the year. When it’s not frozen over, there’s a 12-meter (40 foot) wave to deal with. It’s one of the world’s most extreme environments.
Ice Breaker on Open Water
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. When the seas come up, 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.
Today, climate change is dramatically shifting the nature of ice breakers work. Sea ice is receding in vast areas and there’s significantly less ice for the ships to break through these days. In 2018, the extent of sea ice is already lower than it was in 2012, which was the record low. That means more open water, or ‘blue Arctic,’ as they call it, as opposed to ‘white Arctic.’
(References: www.popsci.com, www.newatlas.com, oceanwide-expeditions.com, www.wikipedia.com)
Sea News Feature, February 15