ice breaker

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Icebreaker Polarstern
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Track of research vessel Polarstern while breaking ice in the Southern Ocean


An icebreaker is a special purpose ship or boat designed to move and navigate through ice-covered waters. Although this article mainly discusses icebreaking ships, the term can refer to smaller vessels (e.g., icebreaking boats that were used on the Canals of Great Britain in the days of commercial carrying).

For a ship to be considered an icebreaker it requires three components: a strengthened hull, an ice-clearing shape, and the power to push through, none of which are possessed by most normal ships.

To pass through ice-covered water, an icebreaker uses its great momentum and power to drive its bow up onto the ice, breaking the ice under the immense 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, the speed of the ship is increased by having 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 even greater risk of damage than the vessel's hull, so the ability for an icebreaker to propel itself onto the ice, break it, and successfully clear the debris from its path is essential for its safety.

History

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An early 20th Century icebreaker — Sankt Erik launched in 1915. Note the shape of the bow, designed to ride up over the ice.
Even in the earliest days of polar exploration, ice-strengthened ships were used. These were originally wooden and based on existing designs, but reinforced, particularly around the waterline with double planking to the hull and strengthening cross members inside the ship. Bands of iron were wrapped around the outside. Sometimes metal sheeting was placed at the bows, stern and along the keel. Such strengthening was designed to help the ship push through ice and also to protect the ship in case it was "nipped" by the ice. Nipping occurs when ice floes around a ship are pushed against the ship trapping it as if in a vice and causing damage. This vice-like action is caused by the force of winds and tides on ice formations. Although such wind and tidal forces may be exerted many miles away, the ice transmits the pressure.

It is supposed that the first steam-powered icebreaker had been built in Kronstadt, Russia in 1864. The icebreaker was known as Pilot.

At the beginning of the 20th Century several countries began to operate purpose-built icebreakers. Most were coastal icebreakers, but Russia and later the Soviet Union also built several oceangoing icebreakers of around 10,000 tonnes displacement. Several technological advances were introduced over the years, but it was not until the introduction of nuclear power in the Soviet icebreaker Lenin in 1959 that icebreakers developed their full potential.

Function of icebreakers

Icebreakers are needed to keep trade routes open where there are either seasonal or permanent ice conditions. Icebreakers are expensive to build and very expensive to run, whether the icebreaker is powered by gas turbines, diesel-electric powerplant or nuclear energy. They are uncomfortable to travel in on the open sea: almost all of them have thick, rounded keels, and with no protuberances for stability, they can roll even in light seas. They are also uncomfortable to travel in when breaking through continuous thick ice due to constant motion, noise, and vibration.

A modern icebreaker typically has shielded propellers both at the bow and at the stern, as well as side thrusters; pumps to move water ballast from side-to-side; and holes on the hull below the waterline to eject air bubbles, all designed to allow an icebreaker stuck amidst thick ice to break free. Many icebreakers also carry aircraft (formerly seaplanes and now helicopters) to assist in reconnaissance and liaison.

Recent advances

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USCGC Healy (WAGB-20)


The shape optimal for moving through ice makes icebreakers uncomfortable in open water and gives them poor fuel efficiency.

Icebreakers tend to roll side to side to the discomfort of the crew. Some new icebreakers such as the USCGC Healy make use of anti-roll tanks. Anti-roll tanks use computer controlled pumps to rapidly shift ballast water side-to-side to keep the vessel upright.

A greater concern is how well a ship cuts through waves. The ability of a ship to cut through waves can greatly affect its fuel efficiency and even its safety in a storm. Most ships use a sharp or bulbous bow to cut through waves and help prevent waves from slamming the bow of the ship. However, icebreakers have a round sled-like bow. They tend to slam into waves, which can be a risk in high seas.

Recent advances in ship propulsion have produced new experimental icebreakers. Electrically driven propellers are mounted to steerable pods under the ship. These Azimuthing Podded Propulsors, or Azi-pods, improve fuel efficiency, ship steering, ship docking, and remove the need for rudders. Azipods also allow a ship to travel backwards as easily as it travels forwards. The double acting icebreaker is unique because its stern is shaped like an icebreaker's bow. Normally travelling forward, a double acting icebreaker uses a conventional ship bow for a more comfortable ride. When ice is encountered, the ship turns around and travels backwards through the ice. The MT Mastera and MT Tempera are two vessels using this new technology.

In the 1980s hovercraft were shown to be effective as icebreakers on rivers. Instead of displacing or crushing the ice from above, they work by injecting a bubble of air under the ice sheet, causing it to break off and be swept downstream by the current. The purpose is usually not to provide navigation channels, rather, to prevent ice dams from forming on bridge structures, thus damaging them and causing local flooding.

''Media: This computer simulation shows a ship transit through an ice-filled channel.

Notable icebreakers

Argentina

Argentine Navy

Australia

Canada

Canadian Coast Guard

Heavy Icebreaker
Icebreaker
Light Icebreaker

Marine Atlantic

Ontario Power Generation

FedNav

Voisey's Bay Nickel Company

Other

China

  • MV Xue Long

Chile

Denmark

  • Icebraker A551 Danbjørn
  • Icebraker A552 Isbjørn
  • Icebraker A553 Thorbjørn

Finland

Finnish Maritime Administration

Commercial

Maritime Museum of Finland

Germany

International

Japan

Norway

Russia

Nuclear powered

Non-nuclear

Sweden

Swedish Maritime Administration

Comercially owned

  • Tor Viking
  • Vidar Viking
  • Balder Viking

United Kingdom

United States

National Science Foundation

R/V Nathaniel B. Palmer. National Science Foundation. Retrieved on 2007-08-16.

External links

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  • Private companies and institutions (transportation, offshore resources, research)
  • Individuals (large yachts, research).

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Anthem
Hymn of the Russian Federation


Capital
(and largest city) Moscow

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Pilot (Russian: Пайлот) was a Russian icebreaker, often referred to as the world's first steam-powered icebreaker.

Pilot had been built as steam-powered propeller thug.
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Anthem
Hymn of the Russian Federation


Capital
(and largest city) Moscow

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Union of Soviet Socialist Republics (abbreviated USSR, Russian: ; tr.
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The MT Tempera is an ocean-going icebreaking tanker that was finished in 2002.

Using Azipod technology, the MT Tempera and its sister ship the MT Mastera are known as double acting tankers.
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