Icebreaker

An icebreaker is a special-purpose ship or boat designed to move and navigate through ice-covered waters, and provide safe waterways for other boats and ships. Although the term usually refers to ice-breaking ships, it may also refer to smaller vessels, such as the icebreaking boats that were once used on the canals of the United Kingdom. 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 frozen-over water or pack ice. The bending strength of sea ice is low enough that the ice breaks usually without noticeable change in the vessel's trim. In cases of very thick ice, an icebreaker can drive its bow onto the ice to break it under the weight of the ship. A buildup of broken ice in front of a ship can slow it down much more than the breaking of the ice itself, so 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 shafts, etc.) are at 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. Prior to ocean-going ships, ice breaking technology was developed on inland canals and rivers using laborers with axes and hooks. The first recorded primitive icebreaker ship was a barge used by the Belgian town of Bruges in 1383 to help clear the town moat. The efforts of the ice-breaking barge were successful enough to warrant the town purchasing four such ships. Ice breaking barges continued to see use during the colder winters of the Little Ice Age with growing use in the Low Country where significant amounts of trade, and transport of people and goods took place. In the course of fifteenth century the use of ice breakers in Flanders (Oudenaarde, Kortrijk, Ieper, Veurne, Diksmuide and Hulst) was already well established.