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We’re going to need a bigger icebreaker!

Dec 30 2013

Image source: BBC News 28 Dec 2013 article:China icebreaker fails to reach stuck Antarctic ship

On Christmas day, the Captain of the Russian research vessel‘Akademik Shokalskiy’ with a complement of 74 persons onboard, comprising of scientists, crew and a number of members of the world’s media, sent out a mayday as his vessel was beset off Eastern Antarctica. Fierce winds had moved rafts of pack ice that had rapidly surrounded and trapped his vessel.

On the 28thDec 2013, the Chinese icebreaker ‘Xue Long’ (Snow Dragon), which was the closest rescue vessel, could approach no closer than 7nm to the ‘Akademik Shokalskiy’ and was forced to return to the open sea. The news of ‘Snow Dragon’s’ aborted attempt coincided with reports from the Australian Maritime Safety Agency (AMSA), which is performing the role of Rescue Coordination Centre (RCC), that a French icebreaker ‘L'Astrolabe’ had also failed to penetrate the ice.

With the news that ‘Snow Dragon’ could no longer proceed, AMSA advised that the ‘Aurora Australis’, was on its way to the Russian vessel (ETA 29th December). AMSA also advised that, should ‘Aurora Australis’ be unable to break the‘Akademik Shokalskiy’ clear from the ice, then ‘Snow Dragon’ has a helicopter onboard that can be used to rescue the passengers.

Today (30th December) after two initial failed attempts it now remains to be seen as to whether the ‘Aurora Australis’, which has the highest icebreaking rating of the three, will be able to go any further than the other two vessels.

Summary based on news articles fromBBC.com/news and Reuters.

 

Argentinian icebreaker ‘Almirante Irizar’ attempting to liberate ‘Magdalena Oldendorff’ from the ice on 19th July 2002

Although it is occurring in the height of the southern hemisphere’s summer, the current situation is reminiscent of the time the 21,000 dwt German cargo vessel ‘Magdalena Oldendorff’ was beset in ice off Antarctica in June 2002. She waited 5 months for the seasons to change despite the efforts of Argentina and South Africa, and even an icebreaker that was dispatched from Sweden, to free her.

 

What are the options to break free the Akademik Shokalskiy’?

The following extracts from the section on ‘Ships that are beset in ice’ are reproduced from Witherby Seamanship’s publication ‘The Ice Navigation Manual’:


Beset in Ice

The phrase `keep moving in ice' is a critical one for shipboard operators to remember. However, while there are times when the ship should be allowed to become beset, the propellers must still be kept turning at slow revolutions until it is able to move again.

A ship becomes beset in ice because of the pressure of ice on the hull. The most common way for this to occur is when open pack ice closes in because of the wind or current. When the ice has been under pressure for some time, rafting, ridging or hummocking can occur.

One method for determining whether the ice pressure is increasing is to watch the track astern of the ship. If the ice either side of the track is closing quickly this shows that there is strong pressure on the ice and gives a warning of the prevailing conditions. Another method to determine if the pressure is coming on or off is to observe the floes in the general area around the ship. Rafting and ridging is a sign that the pressure is coming on, and collapsing of the ridges is a sign it is coming off. Any change in the wind direction should be carefully noted, particularly if the ship is following an inshore lead. If a ship becomes beset, there are a number of ways in which it can try to free itself without assistance.


 

Coming Astern

This action has to be carried out with great care since damage can be caused to the propeller and rudder by ice fragments in the water nearby, particularly if the ship is not equipped with an ice knife or horn. When a ship is beset, it is essential that the propeller is always kept moving to assist in clearing the blocks. Once the ship begins to move astern, the rudder must be kept amidships or damage to the rudder can easily occur.

Under no circumstances should any attempt be made to ram the ice ahead. If the ice is of such thickness to have stopped the ship then it is very dangerous to proceed by ramming. The alternatives are to back out and try another route or await an icebreaker to assist.

Forcing a passage through ice by ramming is not to be recommended. However, there may be circumstances when it is the only option to achieve progress. If this activity is carried out, the main engines should be operating with astern propulsion before the ship actually comes to a stop. In this way, the impact of stopping the ship may be lessened to some degree. This will also ease her extraction.


Alternate Ahead and Astern Movement

Alternate full ahead and full astern movements, combined with the full use of the rudder in the ahead mode only from hard port to starboard, can have the effect of loosening the ship. Care must be taken if the ship begins to go astern during these manoeuvres, as the rudder must be amidships when moving astern. If the ship is extracted then it can continue ahead if the ice is not too thick.

The rudder must be amidships when moving astern. However, if the rudder moves involuntarily then you should go ahead.


Changes in the Ballast Distribution

Owing to the time necessary for this operation, changing the ballast distribution would be an extreme procedure to carry out and only considered if an icebreaker was not available. The whole aim is to free the hull from the ice by transferring ballast from one tank to another and changing the trim and/or the list of the ship. The smaller the ship, the less time would be taken with such an exercise. Smaller ships with onboard lifting equipment can try swinging weights over the side to rock the ship free.

Even for a ship that has been frozen in an ice field overnight, heeling of the vessel will exert sufficient pressure around the perimeter of the ice hull boundary to break the ice. Often however, the ice breaks some distance from the ship's hull, leaving some ice that adheres and presents an ice profile that generates increased friction at the waterline.Typically, the necessary angle of heel to exert sufficient bending of the ice at the ice-hull interface is achieved by heeling the vessel 5°. On larger vessels, such an angle of heel would not be practical and on such vessels the angle of heel should not result in a change in submergence at the waterline of more than 1 metre.

 

 

A Summary of Actions when Beset

While forcing through ice by increasing speed, a loaded ship can get stuck by ice gripping the bilge keel area of the hull. Conversely, a ship in the ballast condition and trimmed by the stern that has mounted the ice cannot move astern. A ballasted ship in brash conditions can `ground on it' as she builds up a large ball of brash ice beneath the hull.

 

  

Method of freeing

the ship

Action

Using the engines/rudder to shake the ship

Shift the rudder from side to side while operating the engine at full speed ahead. This will permit a slight swing of the stern to either side and result in the whole ship moving slightly forward. After this, move astern and the ship can be freed. In ships fitted with twin propellers, it is advisable to alternately operate the engines in opposite directions.

This sudden movement change from full ahead to full astern and vice versa will help to `shake' the ship free.

Using ballast

Free the ship by heeling, which can be achieved by pumping water to the port then starboard ballast tanks.

Alternatively, pump water in the forepeak and aftpeak tanks, initially filling the forepeak with water and pumping out the aftpeak, then transferring water from the forepeak to the aftpeak.

Using patience

It is sometimes sensible to wait a period of time as the pressure of the ship on the ice and the effect of higher temperature of the hull in direct contact will result in the ice and snow melting a little. The water that forms acts as a lubricant.

Ramming

Ramming is used to attempt to pass through ice that has proved too thick to break. It requires extreme caution. The art of ramming is a simple process of determining the optimum distance to back away from the ice edge that will allow you to build up sufficient speed to break the ice without damaging the ship with the least distance moved astern.

This process should be started with short strikes, ie rams, to help you determine the thickness and hardness of the ice.

The impact forces when ramming the vessel against the ice edge can be very high and even for ice strengthened vessels these forces may result in damage. Therefore, ramming should be restricted to low speeds to help reduce this risk. Ramming should not be undertaken by vessels that are not suitably ice strengthened or by vessels fitted with a bulbous bow.

 

Icebreaker Assistance for Beset Ships

Where icebreaker assistance is requested by a beset ship that cannot free herself, towing may not always be the best option. The movement of the icebreaker in close proximity to the ship may break up and loosen the surrounding ice and allow the ship to move independently or under icebreaker escort from the area. Alternatively, towing by the icebreaker into an area of clear water may be necessary.

 

Ships that find themselves beset in ice should endeavour to keep the main engines turning ahead slowly. This action will hopefully keep the propellers and rudder areas clear of ice accumulation until the icebreaker can break the ice on either side and ahead of the ship.

Where thin ice is present, icebreakers would probably expect to make an approach from astern using the same channel that provided the initial entry for the ship. As the icebreaker nears the trapped ship, the icebreaker generally moves along the side of the ship and breaks the ice towards the bow. The icebreaker moving astern passes down the opposite side of the beset ship before proceeding ahead and instructing the ship to follow her.

In multiyear ice, the icebreaker would circle in the ahead mode around the stern and make the third pass on the original side before proceeding ahead.

Ships being assisted by icebreakers can become stuck in three ways:

  • If small ice pieces and some larger fragments get churned into a solid mass in the channel behind the icebreaker
  • if the channel behind the icebreaker gets blocked by ice under the influence of wind and currents
  • if channel curves are too tight for the length of the ship.

If there is a sizeable pool of free water astern of the beset ship, or open small ice pieces, the beset ship should move astern when the pressure is released so that, when the icebreaker moves in front, there is less ice to break.

The icebreaker track will take account of the necessity for major course alterations to be executed in loose ice or open pools.

 

Extracted from the 416 page volume ‘The Ice Navigation Manual’ published in 2010 By Witherby Seamanship.

For more details and to buy, please see: http://www.witherbyseamanship.com/the-ice-navigation-manual.html