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Post by throttleup on Jan 11, 2012 12:46:17 GMT
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Post by throttleup on Jan 11, 2012 15:09:16 GMT
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Post by numerouno on Jan 11, 2012 15:50:58 GMT
Even icebreakers can get stuck in ice, happens occationally even in the Baltic, when winds pack up ice. For the diesel-powered ships, it will be useless to spend fuel then. When the wind changes, the ice will release its catch. The Finnish Urho class of conventional design is said to be able to penetrate 15 meters thick packed ice. (source: the video below) I collected some icebreaker clips from Finnish sources. If I remember correctly, some 60% of the world's icebreaker fleet is made in Finland. yle.fi/elavaarkisto/artikkelit/talvisen_itameren_tyojuhdat_45728.html#media=45733Choose "Jäänmurtajan arkipäivää perämerellä" ("Ordinary day on an icebreaker in the north of the Gulf of Bothnia"). The programme is from 1977, it contains an animation of the icebreaker principles, and research video. (0:50). For some HD action, see 27:00 onwards. The ship "Sisu" is still operating, she and her sister ship are the last ones to deploy, and only for difficult conditions, I wonder if they'll be used this winter or not. (Three more ships in the class are operated by the Swedish.)
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Post by curiousgeorge on Jan 11, 2012 18:00:03 GMT
How it was done in 1956. USS Burton Island
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Post by numerouno on Jan 11, 2012 18:18:31 GMT
the 'sugar ice' mixure refreezes in the -26C conditions
Refreezed, once broken ice will be no problem for some time to come. Remember, it's the air, not the water that will be at -26C. (Since you're in Finland, see where Helsinki ducks spend their time during winter.) The Arctic lead will close first due to wind and currents.
There is no icebreaker conceivable that could maintain normal operating speed in heavy pack ice. The Urho class can maintain close to 14 knots in regular ice with a thickness of 2-3 meters (6-10 feet). (Source: the programme above.)
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Post by numerouno on Jan 11, 2012 20:01:42 GMT
I think you are forgetting that ice or a warm duck insulates water and the thicker the ice the less heat in the ice compared to the warmer water under the ice. Ie coldness or less heat is 'stored' in the thick ice but very little is in contact with the water.
Yes, the feathers of a duck are excellent insulating material and what is very important, repel water. The reason for the ducks to favour spending their time in water is the fact that in winter when air is -20C, the water will be about 20 degrees warmer, minimizing the loss of radiated heat from their bodies, as conductivity of heat in water will be minimized by those excellent feathers. Their uninsulated feet will also feel "warm".
There is no heat nor cold "stored" in ice as such, above its natural thermal capacity, and the latent heat as solidified water. Phase change energy of ice blocks in water will locally disturb the energy balance, yes. But the phase change energy drawn from water is not dependant on air temp. What a fully developed ice cover does, and is, is an insulation that is just enough good an insulation from air to prevent any further forming of ice underneath it.
Any quickly grown ice in the opened lead will be weak, and can be easily reopened as there is no homogenous structure that is present in ice that has grown undisturbed. (Known as "steel ice" in Finnish parlance.) Pack ice is strong as it's a kind of composite structure consisting of different ices in different configurations, a kind of plywood. In any case, conditions in the Arctic will be such that those narrow leads will be mechanically erased in a short time.
Refueling of the Alaskan arctic has apparently never been attempted before.
.. in winter, you must surely mean?
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Post by numerouno on Jan 11, 2012 22:02:11 GMT
You have misunderstood my explanation as to why finely crushed very cold ice will freeze water near the freezing point.
No phase changes or latent heats are involved in my explanation.
No I have not. Your ice will undergo a phase change, melting in water. This phase change will require energy. This energy is overwhelmingly drawn from water, not air. Undisturbed, and in darkness, ice will not be "enormously cold", but its temp will be somewhere in between the air temp on the above, and the sea below. There will be what is known as gradient inside the ice between these two temps.
It was not I who showed the 1956 pic.
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Post by throttleup on Jan 11, 2012 23:23:46 GMT
Healy UpdateUpdate Jan. 10, 5:30 p.m. from Capt. Carter Whalen, president of Alaska Marine Pilots Today's progress is about 50'. Healy is trying to free Renda right now from an ice ridge. There is better, more favorable ice ahead. Many factors at work out there. A tough day for all. That's fifty feet progress today. Tough sledding. www.alaskadispatch.com/article/update-aboard-renda-slow-going-tuesday--------------- 50 feet.
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Post by numerouno on Jan 11, 2012 23:25:16 GMT
When ice melts it acts to cool the mixture. When it freezes it acts to warm the mixture.Freezing adds warmth to the mixture only to the extent that the temperature at the point of freezing will "automatically" stay at the pre-determined freezing point valid under the conditions (considering salinity). The medium for heat transfer will overwhelmingly be water, not air. There can arise a host of practical scenarios depending on what salt content different ices of different ages broken have, how badly the icebreaker mixed up the layers of water during the icebreaking process etc etc. Icebreakers can reverse as easily as sail forward due to their bow propellers. The latest development is a sideways working icebreaker: www.akerarctic.fi/publications/pdf/aker%20arc%20100.pdf
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Post by throttleup on Jan 11, 2012 23:31:11 GMT
Stop the Presses!Nevermind the Healy! All is well!Arctic sea ice continues to shrink, even in frigid winterEven as winter clamps down, our polar ice cap continues to dwindle. Despite the arrival of frigid winter temperatures north of Alaska, the sea ice of the Arctic Ocean ended 2011 far below average in both extent and volume, continuing its decades-long shrink toward summer oblivion, according to the most recent estimates posted online by polar observers. www.alaskadispatch.com/article/arctic-sea-ice-continues-shrink-even-frigid-winterSomebody tell dontgetoutmuch! Although he's probably outside trying to find his roof...
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Post by numerouno on Jan 11, 2012 23:56:28 GMT
One possible point on this saga sprang to my mind -- the boat could simply be too wide for the lead this icebreaker opens, so pressure from leftover ice in the lead pushing through the edges of the channel causes too much friction, mechanically. Icebreakers use air "bubblers" and/or stainless steel plating at the waterline to overcome this.
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Post by numerouno on Jan 12, 2012 12:07:28 GMT
Iceskaters, I don't think there is any other kind of ice on sea than the "mostly submerged" kind. Not even in the Eemian :.)
The Healey might be wider than the tanker, but the ice left in its wake I think will not compress favourably against the edges of opened channel when the tanker sails in it. Unlike the icebreaker, the hull shape of the tanker is not designed to minimize friction against ice. The icebreaker hull seeks to push the blocks of ice deeper in water, away from the opened route. Naturally all active devices to minimize friction are absent.
Some reports say icebreakers would "ram" the ice in difficult conditions. What they actually do is they utilize their own weight and hull shape to climb on top of the ice and crush it downwards. By using the pumpable water ballast to sway itself the ship will then be able to "dig a trench" in the ice much thicker than its own draught.
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Post by numerouno on Jan 12, 2012 21:16:56 GMT
Ice could be grounded.Yes it could, but in the Arctic the ships won't be seen anywhere close to grounded ice, unless perhaps when the master is suffering from a suicidal tendency. The waters are not totally uncharted after all. The icebreaker has to reverse and then move forwards again and again until it is thru the obstruction. I doubt an icebreaker can dig a trench in thick iceYou don't have to harbour any doubts about it, while you can simply watch the 1977 icebreaker video I gave the link to. If you don't understand the language (the fact is stated explicitly in the narration), you can read again what I told you about it. See the animation at 0:50, or watch the icebreaker in action starting from about 27:00 doing just the thing. Here's that link again: www.yle.fi/elavaarkisto/artikkelit/talvisen_itameren_tyojuhdat_45728.html#media=45733
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Post by numerouno on Jan 12, 2012 23:42:31 GMT
A trench is a three sided hole going lengthways in for example the earth.
Icebreakers create passages thru the ice rather than trenches.
Iceskaters, apparently you can't Finnish, but suggesting I can't either is a bit rich.
The narration from the document from 2:28: "Jos potkurivoima ei yksin riitä, kaytetään kallistuskoneistoa. Aluksen sivuille, kannen korkeudelle, on sijoitettu valtavat vesitankit. Metrin paksuiset putket yhdistävät tankit voimakkaisiin pumppuhin. Siirtämällä vesimassat aluksen toiselta puolelta toiselle, voidaan murtajaa kallistella ja siten estetään murtajan kiinnijääminen jäämassoihin. Keinahdellesssan puolelta toiselle murtaja painollaan tunkeutuu yhä syvemmlle jäähän rikkoen sitä ja painaen jäämassat alaspäin. Tälla tavalla Sisu pystyy avaamaan uoman ahtaumavyöhykkeisiin, joiden paksuus on huomattavan paljon suurempi kuin aluksen oma syvyys. Murtaja ikaan kuin 'kaivaa' jäähän avo-ojan. Tarvittaessa se pystyy tunkeutumaan uskomattoman paksujen ahtaumavyöhykkeiden läpi."
My quick translation of the above: "If the power from the propellers is not enough, the heeling mechanism will be used. On both sides of the vessel, at the level of the first deck, are installed huge tanks of water. Tubes that are one meter in diameter interconnect these through powerful pumps. By moving the masses of water from one side to another, the icebreaker will be made to heel and thus prevent it getting stuck in the masses of ice. As the icebreaker is heeling, it will be penetrating even deeper into the ice by its own weight crushing ice and pressing ice masses further underneath. In this way the Sisu will be able to open a passage into ice that is considerably thicker than the vessel's own depth. The icebreaker as it were 'digs' an open trench into the ice. If needed, it's able to penetrate through incredibly thick zones of pack ice."
I should think this is quite enough to settle the issue? Or are you saying me and the document makers got it wrong?
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Post by numerouno on Jan 13, 2012 0:39:04 GMT
Something is not right. For example you said the Urhu class could go thru 2 to 3 m of ice at 14ktsThe narrator said the speed "hardly" slows down from the top speed of 14 kts under breaking 2-3 ("pari") meters of ice. We can deduce from that the talk was about maximum effort, not the normal economical speed. In the documentary, on the bridge I hear they are planning to cover some 75 nautical miles in something over 5 hours under their operation. It was a bit unclear due to the rustle on the deck. I think the word trench is open to interpretation and further investigationHere's the google pic search on "avo-oja", the word used: images.google.com/search?tbm=isch&hl=EN&source=hp&biw=1270&bih=880&q=avo-oja&gbv=2&oq=avo-oja# At this point in time I find it incredible that low temperature ice could be crushed like that. Snow yes or if it were near freezing. Well I don't know what your exact deficiency in understanding auditory, written and illustrated material is, but such are the facts presented in any case. EDIT: Urho class vessel Ymer: This is a photo and video report the icebreaker Ymer, one of Sweden's three icebreakers cruising through the Bay of Bothnia between november and april every year to assure ship's traffic to the important industry ports such as Luleå on the Swedish coast. Day and night, this ship fights though the ice that sometimes is up to 5 and more meters thick. But this does not stop the Ymer. It's built to break any ice, even if it has to "drill" itself though ice walls. As it is of a high economic interest to keep open all waterways all year round, Ymer and its entire crew give their best - often by passion not by duty.adrianstreun.prosite.com/30678/312689/gallery/isbrytare
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