6
U.S. Polar Icebreaker Fleet

ICEBREAKING SHIPS—AN HISTORICAL PERSPECTIVE

The Early Years

Icebreaking ships are a relatively new evolution in the history of ship design and construction. Conventional ships in or near ice-covered waters from the earliest years of recorded history had to do their best to avoid the ice. If they failed, they risked being trapped in ice with the potential loss of the ship and crew due to the extreme pressures and strength of the ice.

As early as 1819, Lt. William E. Parry of Great Britain tried to sail his 375-ton bark, HECLA, through the Northwest Passage. He was forced to winter on Melville Island before turning back in 1820 due to his inability to penetrate the ice. HECLA was not designed for operation in ice, and this was true of many of the other early polar explorers’ ships. Although the desire to explore the Antarctic and Arctic may have initiated the development of ships designed to operate in and around ice-covered waters, this desire was closely coupled with the commercial aspirations of whalers and seal hunters. Initially, these purpose-built ships were intended only to survive in the harsh environments, not to routinely break ice. As such, they were considered ice-strengthened ships.

By the latter part of the nineteenth century, ships were being built for the purpose of breaking ice. British shipyards constructed several powerful icebreaking ships for the Imperial Russian government. Around the same time Canada ordered several smaller icebreakers to perform escort service in the St. Lawrence River and Gulf.

The U.S. Navy and the Revenue Cutter Service each had interests in ice-filled waters, but neither had specialized ships for operation in the ice until the late 1800s. The Revenue Cutter Service used conventional cutters to perform patrols in the Arctic on a regular basis since 1880 when CORWIN made her first patrols there. The Revenue Cutter Service acquired its first ice-strengthened ship in 1884 when the U.S. Congress authorized the purchase of BEAR, a 10-year-old sealing vessel built in Scotland. BEAR was purchased to perform a rescue mission of a U.S. Army expedition stranded on northern Ellesmere Island. The rescue mission was a success and showed BEAR’s characteristic to be ideally suited to Arctic Ocean cruising around Alaska. BEAR was originally built as an ice-going sealing ship with closely spaced 24-inch oak frames, heavy internal beams and stanchions, a reinforced bow, and Australian iron-bark sheathing covering the oak hull planking from keel to waterline.

While some cities in the United States had employed ships to work in harbor ice as early as 1837 when CITY ICE BOAT NO. 1 was built in Philadelphia for use on the Delaware River, the first large U.S. ship built to work in ice was not designed and built until 1927. Drawing on the experience of 47 officers with Arctic experience, the U.S. Coast Guard contracted with Newport News Shipbuilding and Drydock Company to build the 216-foot steel-hulled NORTHLAND. Displacing 1,785 tons with welded and riveted construction, an industry periodical stated that “for its size, [it was] the strongest and heaviest steel hull which has ever been projected.”

Although the NORTHLAND patrolled the Alaskan Arctic for 11 years, she was a disappointment. Her slowness and poor handling characteristics prevented her effective use in the waters of the “lower 48.” This, coupled with the end of commercial whaling in the Arctic, caused Coast Guard Headquarters to question the need for continued operation of a large specialized cutter for only six months each year. “Even a former NORTHLAND commanding officer believed that a regular cruising cutter could perform all of the routine Arctic cruise functions, except for assisting vessels in ice.” Unstrengthened cutters cruised to Point Barrow in 1939, 1940, and 1941.

President Franklin Roosevelt issued an Executive Order



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Polar Icebreakers in a Changing World: An Assessment of U.S. Needs 6 U.S. Polar Icebreaker Fleet ICEBREAKING SHIPS—AN HISTORICAL PERSPECTIVE The Early Years Icebreaking ships are a relatively new evolution in the history of ship design and construction. Conventional ships in or near ice-covered waters from the earliest years of recorded history had to do their best to avoid the ice. If they failed, they risked being trapped in ice with the potential loss of the ship and crew due to the extreme pressures and strength of the ice. As early as 1819, Lt. William E. Parry of Great Britain tried to sail his 375-ton bark, HECLA, through the Northwest Passage. He was forced to winter on Melville Island before turning back in 1820 due to his inability to penetrate the ice. HECLA was not designed for operation in ice, and this was true of many of the other early polar explorers’ ships. Although the desire to explore the Antarctic and Arctic may have initiated the development of ships designed to operate in and around ice-covered waters, this desire was closely coupled with the commercial aspirations of whalers and seal hunters. Initially, these purpose-built ships were intended only to survive in the harsh environments, not to routinely break ice. As such, they were considered ice-strengthened ships. By the latter part of the nineteenth century, ships were being built for the purpose of breaking ice. British shipyards constructed several powerful icebreaking ships for the Imperial Russian government. Around the same time Canada ordered several smaller icebreakers to perform escort service in the St. Lawrence River and Gulf. The U.S. Navy and the Revenue Cutter Service each had interests in ice-filled waters, but neither had specialized ships for operation in the ice until the late 1800s. The Revenue Cutter Service used conventional cutters to perform patrols in the Arctic on a regular basis since 1880 when CORWIN made her first patrols there. The Revenue Cutter Service acquired its first ice-strengthened ship in 1884 when the U.S. Congress authorized the purchase of BEAR, a 10-year-old sealing vessel built in Scotland. BEAR was purchased to perform a rescue mission of a U.S. Army expedition stranded on northern Ellesmere Island. The rescue mission was a success and showed BEAR’s characteristic to be ideally suited to Arctic Ocean cruising around Alaska. BEAR was originally built as an ice-going sealing ship with closely spaced 24-inch oak frames, heavy internal beams and stanchions, a reinforced bow, and Australian iron-bark sheathing covering the oak hull planking from keel to waterline. While some cities in the United States had employed ships to work in harbor ice as early as 1837 when CITY ICE BOAT NO. 1 was built in Philadelphia for use on the Delaware River, the first large U.S. ship built to work in ice was not designed and built until 1927. Drawing on the experience of 47 officers with Arctic experience, the U.S. Coast Guard contracted with Newport News Shipbuilding and Drydock Company to build the 216-foot steel-hulled NORTHLAND. Displacing 1,785 tons with welded and riveted construction, an industry periodical stated that “for its size, [it was] the strongest and heaviest steel hull which has ever been projected.” Although the NORTHLAND patrolled the Alaskan Arctic for 11 years, she was a disappointment. Her slowness and poor handling characteristics prevented her effective use in the waters of the “lower 48.” This, coupled with the end of commercial whaling in the Arctic, caused Coast Guard Headquarters to question the need for continued operation of a large specialized cutter for only six months each year. “Even a former NORTHLAND commanding officer believed that a regular cruising cutter could perform all of the routine Arctic cruise functions, except for assisting vessels in ice.” Unstrengthened cutters cruised to Point Barrow in 1939, 1940, and 1941. President Franklin Roosevelt issued an Executive Order

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Polar Icebreakers in a Changing World: An Assessment of U.S. Needs on December 21, 1936, directing the U.S. Coast Guard to assist in keeping channels and harbors open to navigation by means of icebreaking operations. Recognizing that the nations of northern Europe whose waters were often ice-covered had made major advances in icebreaking ship development in the early twentieth century, the U.S. Coast Guard directed Lt. Edward H. Thiele to make a survey of northern European icebreakers. He obtained valuable information, especially from the Swedes and the Finns. It was ironic that Thiele found that one of the most advanced Swedish icebreakers, the 258-foot YMER built in 1932, had been designed using the bow form of the Great Lakes car ferry ST. MARIE. Subsequently, Thiele was part of a team that designed a class of successful 110-foot icebreaking tugs for harbor and channel work—the first completed in 1939. In 1941, another large icebreaking vessel was authorized and commissioned in 1942 as the STORIS. She was an enlarged 230-foot version of a class of 180-foot buoy tenders. Although STORIS was designed to serve as a light icebreaker in Greenland waters, she gained special recognition in 1957 when she, with two 180-foot tenders, became the first U.S. ship to travel the Northwest Passage from west to east. World War II All of the foregoing designs led to the development of the first true U.S. icebreakers, the Wind class. Once again the President of the United States was instrumental in this decision. Rear Admiral Edward H. Thiele remembered that in 1941 he had obtained orders to the AMERICAN SAILOR as executive officer, believing that too much Washington duty might affect his career adversely. While the ship was fitted out in Baltimore, he was recalled to Coast Guard Headquarters by Engineer-in-Chief Harvey Johnson, who took him to the commandant’s office. There Commandant Waesche handed him a note that the President had written to Treasury Secretary Morganthau stating, “I want the world’s greatest icebreakers.” Thiele speculated that these ships were to support the construction of an airfield at the head of Greenland’s Sondre Stromfjord and to aid in the shipment of lend-lease supplies to Archangel, the Russian White Sea port. Thiele, tasked to lead the design effort, was exploring various alternatives. At the same time, Secretary Morganthau recommended to the Secretary of State that the United States negotiate the purchase of one or more Russian icebreakers. The Russians offered the KRASIN built in 1917 in Great Britain. While Thiele felt KRASIN was “ancient history at best,” the deal fell through only due to the pressing need of Russia to keep the seaway to Archangel open. Thiele’s design was far different from anything ever built in the United States. The Wind class would have half again the beam (63 feet, 6 inches), two-thirds more draft (25 feet, 9 inches), and almost four times the displacement of STORIS. Five and a half times more horsepower required two shafts, one of the most radical differences from the previous succession of single-shaft icebreaking ships, that also offered obvious advantages of redundancy in case of shaft or propeller damage far from repair facilities. The large beam let the ship cut a wide track in ice for escorted ships to follow and, as importantly, decreased the risk of ice damage to the propellers set as far inboard as possible. Similarly, the deep draft enabled the use of large propellers for strength and power, and put their blade tips deep enough to lessen contact with floating ice. A diesel-electric propulsion plant was chosen. Proven in several previous applications, it offered economy in fuel consumption and generated relatively high horsepower for the space required. The machinery components could be arranged flexibly within the ship. The six diesel engines and generators provided redundancy and flexibility for operations that would include long periods of icebreaking at full power and lengthy, open-water transits at low power levels. Diesel-electric propulsion would also deliver maximum thrust when the ship was stopped, a frequent occurrence when operating in difficult ice conditions. Additionally, the operating environment required that machinery remain unaffected by the shocks that result from propellers striking ice, which a diesel-electric plant addresses by electrical, rather than mechanical, linkages between components. An icebreaker’s hull form is crucial to its effectiveness. The Wind class design incorporated a sloped forefoot that met the ice at a 30-degree angle. By that time, this had become a distinguishing feature of icebreaking ships. This bow configuration, with its surface sloping down and aft below the waterline, is key to how an icebreaker works. As the ship forces itself against a horizontal ice surface, the bow rides up on the ice until the vessel’s weight breaks the ice in a downward motion and displaces the broken pieces to each side. In the Wind class design, this action distributed the icebreaking forces efficiently over the entire forebody. The stern was similarly shaped to permit backing into ice when backing and ramming. To absorb the repeated impacts of ice and withstand its potential crushing pressures, the hull had enormous strength. Flare in the hull helped reduce frictional effects when moving through ice and in ice under heavy pressure would cause the ship to be lifted rather than crushed. The 1 1/4-inch hull plating of high-tensile steel increased to a thickness of 1 5/8 inches along the ice belt. However, the real strength lay in the entire structure of deck beams, structural bulkheads, and frames spaced 16 inches apart. Double bottoms and wing tanks surrounded the engineering spaces with a layer of protection in the event the hull plating was punctured. The Swedish icebreaker YMER served as a general prototype for the Wind class design. The YMER influence can be seen most readily in the inclusion of heeling tanks and a bow propeller. The three pairs of heeling tanks were connected by 24-inch ducts and 60-horsepower (9hp) reversible pumps that could transfer 13,600 gallons of water per minute

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Polar Icebreakers in a Changing World: An Assessment of U.S. Needs to induce a heel of about 5 degrees to each side of the vertical in 90-second cycles. This capability offered a means of breaking the frictional “lock” of ice and snow on the ship’s sides. Peak tanks at the bow and stern permitted the ship’s fore-and-aft trim to be varied as much as 5 feet so that the bow could attack the ice at a better angle under different conditions of loading. The reversible bow propeller protruding forward from the forefoot near the keel could apply up to 3,300 horsepower to assist in breaking ice. However, it proved easily damaged and of little practical use in polar ice conditions and was soon removed from all Wind class vessels. Based on this initial design, the U.S. Coast Guard hired Gibbs and Cox, one of the largest naval architectural companies in the United States, to perform the detailed design. Finally, on November 15, 1941, a contract was awarded to Western Pipe and Steel Company to construct four ships at its newly created shipyard near Los Angeles. This company had the experience and technology to work with heavy high-tensile steel plating. Thus, the NORTHWIND, EASTWIND, SOUTHWIND, and WESTWIND were born. Subsequently, it was decided to transfer the NORTHWIND to the Soviet Union to help ensure her continuation in the war. She was renamed SEVERNI VETER in 1943 and sailed off to the Russian Arctic. A replacement was ordered, and EASTWIND, SOUTHWIND, and WESTWIND were delivered in June, July, and September of 1944. In 1945, WESTWIND and SOUTHWIND were turned over to the Soviets and two more replacements were ordered. By war’s end, EASTWIND and the “new” NORTHWIND were serving the U.S. Coast Guard, while the last two replacement icebreakers were delivered to the U.S. Navy as the BURTON ISLAND and EDISTO, beginning the Navy’s entry into icebreaker operations. Postwar Fleet The United States secured the return of the icebreakers loaned to the Soviet Union; and they joined the U.S. fleet as the ATKA and STATEN ISLAND (flying the Navy ensign) and the WESTWIND (returning to the Coast Guard). In addition, Gibbs and Cox designed a larger version of the Wind class known as the GLACIER. When commissioned by the Navy in 1955, at 310 feet long, 74 feet abeam, and displacing 8,449 tons with 10 diesel engines producing 21,000 horsepower on two shafts, she was the largest icebreaker among the eight heavy icebreakers then operated by the United States. While the two services exhibited an extraordinary level of cooperation over the years, it became apparent that the Navy could not justify continuing operation of icebreakers when it needed combatant ships to replace its aging World War II fleet. Consequently, a Memorandum of Agreement was signed between the Department of the Treasury and the Department of the Navy providing for “The permanent transfer to the Coast Guard, at the earliest practicable date, but not later than 1 November 1966, of jurisdiction, control over, and responsibility for operating and manning the five U.S. Navy icebreakers in high latitudes to fulfill U.S. Navy mission requirements.” Thus, after a 20-year presence in operating icebreakers, the Navy relinquished its role to the Coast Guard. Even with a fleet of eight icebreakers, the workload for the ships was large. Supporting logistics, escort, and patrol in both the Antarctic and the Arctic was a challenge because of the virtual explosion of these activities in the years immediately following the war. However, by the mid-1960s these activities were beginning to abate and budgetary constraints led to the retirement of the first Wind class ship in 1969, the EASTWIND. As early as 1963, the Coast Guard began discussing the need for new icebreakers. A design team was formed by 1965 and commenced a lengthy period of review, research, and design. In 1969, based on the anticipated acquisition of new highly capable icebreakers, U.S. Coast Guard planners projected a need for a fleet of only five polar icebreaking ships to meet requirements. The fleet was to consist of four new icebreakers and GLACIER. The final design of what was to become the Polar class, was a ship design that substantially exceeded the capability of previous U.S. icebreakers. At 399 feet and 13,190 ton displacement (more than twice the displacement of the Wind Class), the ships had space for two helicopters and an unprecedented suite of scientific facilities. The hull design was well researched, and special alloy steel that possessed a 50 percent increase in yield strength over mild steel was used in hull plating, ice frames, and weather decks. The first new ship contract was awarded to Lockheed Shipbuilding and Construction Company in Seattle in 1971. Two years later a contract was awarded for a second ship. These were to become the POLAR STAR and the POLAR SEA, respectively. Recognizing that the new ships could not be completed for some time, a program was created to rehabilitate and modernize two Wind-class ships to bridge the gap. NORTHWIND and WESTWIND were selected to undergo vessel rehabilitation and modernization (VRAM) at the Coast Guard Yard in Curtis Bay, Maryland. This work was completed and the two ships returned to service in 1974-1975, six months before the POLAR STAR was delivered to begin its shakedown process. During 1974, SOUTHWIND, EDISTO, and STATEN ISLAND were decommissioned. POLAR SEA was delivered in 1978. When BURTON ISLAND was decommissioned in 1978, the Coast Guard had a fleet of five icebreaking ships. ASSESSMENT OF NATIONAL ICEBREAKER REQUIREMENTS While the U.S. Coast Guard continued to prepare a series of icebreaking ship designs, the costs associated with proposed new ships was growing. This caused the proposals

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Polar Icebreakers in a Changing World: An Assessment of U.S. Needs to be reanalyzed and reconsidered, and ultimately, in 1980, the Office of Management and Budget (OMB) rejected the proposed budget request for a new icebreaker. Study followed study until 1983 when the Coast Guard organized a Polar Icebreaker Requirements Study (PIRS), which was unique in that it involved other federal agencies for the first time. The other agencies included the Department of Defense, National Science Foundation, and Maritime Administration, all of which were utilizing the services of the existing fleet. In the same year, OMB directed that all icebreaker costs be fully reimbursable, and a complex scheme of fixed costs to be reimbursed to the Coast Guard was developed along with actual expenses incurred in polar regions. Ultimately the National Oceanic and Atmospheric Administration (NOAA), Department of Transportation, and OMB joined the PIRS study group. The final 400-page report stated that there were “no satisfactory alternatives to take the place of polar icebreaking services.” A summary of the PIRS findings follows. In studying icebreaker funding, PIRS reviewed the full reimbursement system in detail. While recognizing the theoretical advantages of incorporating full icebreaker costs in the budgets of user agency programs, the PIRS report also reflected the general discontent with reimbursement. The report cited the following disadvantages: Increased difficulty in managing an icebreaker fleet, when unexpected perturbations in agency budgets can eliminate large amounts of funding with little notice, Inefficient utilization due to the rigid allocation of icebreaker days, Difficulty in providing support for other than the designated users, and Potential for reduction in the icebreaker fleet due to distorted reimbursement incentives. The impact of reimbursement was felt even before completion of the PIRS report. The $5.3 million transferred to the Maritime Administration (MARAD) bloated the small agency’s research and development budget substantially. When the 1984 budget reduced MARAD’s R&D appropriation to its traditional level, MARAD redirected its icebreaker funding to its other traditional programs. The Coast Guard was left without funding for one of the five ships. PIRS also assessed funding acquisition costs under shared arrangements with other agencies and with industry without discovering any attractive alternatives. After making estimates of operating and capital costs, PIRS concluded that an icebreaker fleet is essential to the national interest and should be operated by the U.S. Coast Guard. The report’s significant recommendations include the following: The Coast Guard should maintain a fleet of four icebreakers to meet the projected requirements. In a minority opinion the Coast Guard argued that a fifth icebreaker should remain “in reserve” due to the age of the ships and a possible increase in requirements. Design of a new icebreaker should start immediately, emphasizing research as well as escort and logistics capabilities, and should reflect the needs of both primary and secondary users. Icebreaking capability should be between that of the Wind and Polar classes. Capital cost of replacement icebreakers should be funded by the Coast Guard. Reimbursement should be reexamined and a joint recommendation for change pursued through the budget process. Scientific capabilities of the Polar class icebreakers should be improved. Based on the PIRS, the U.S. Coast Guard began consulting with other agencies concerning requirements for a future icebreaker design. At the same time, three of the existing ships were experiencing increased wear and tear and the Coast Guard had funds to operate only four, not five, ships. Consequently, WESTWIND was placed in layup with a small caretaker crew. By 1986, Coast Guard engineers were expressing concerns about the structural integrity of the GLACIER. Because 21 to 28 percent of her hull plating had been lost to corrosion, much of her hull framing and some 20 percent of structural decks and bulkheads were deemed inadequate. Emergency repairs permitted her to sail on the 1986-1987 Antarctic mission, but she was operationally restricted to “limited ice transit.” The cost of a full refurbishment, coupled with her manpower-intensive configuration and high operating costs, led the commandant to decommission her in 1987. This left the nation with four icebreakers. Bringing WESTWIND back into service proved more challenging than expected, and NORTHWIND too began to falter. Engine problems forced her to miss resupply operations in Greenland in 1987, and with the lack of a backup, the commandant was forced to request Canadian assistance. This led to the decommissioning of WESTWIND in 1988 and NORTHWIND in 1989, leaving the United States with only two heavy icebreakers. THE PRESENT FLEET OF U.S. ICEBREAKERS Even as the old fleet was in rapid decline, but not yet lost, there was a strong sense that new icebreakers were needed. The PIRS report was one of the indicators, and the Coast Guard Authorization Act of 1984 stated: It is the sense of the Congress that the United States has important security, economic, and environmental interests in developing and maintaining a fleet of icebreaking vessels capable of operating effectively and independently in the heavy ice regions of the Arctic and the Antarctic. The Secretary of the Department in which the Coast Guard is operating shall prepare design and construction plans for the purchase of at least two polar icebreaking vessels to be opera-

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Polar Icebreakers in a Changing World: An Assessment of U.S. Needs TABLE 6.1 Current U.S. Coast Guard Polar Icebreakers Characteristic POLAR STAR and POLAR SEA HEALY Length (feet) 399 420 Displacement (long tons) 13,334 16,165 Cruise speed (knots) 12 12 Endurance (days, nautical miles) 205, 23,000 205, 23,000 Power (SHP) 60,000 30,000 Crew size 134 67 Scientists 20 50 Icebreaking capability 6 feet at 3 knots 4.5 feet at 3 knots NOTE: SHP = shaft horsepower. tional by the conclusion of fiscal year 1990…. In preparing such plans, the Secretary shall consult with other interested federal agencies for the purpose of ensuring that all appropriate military, scientific, economic and environmental interests are taken into account. The design proceeded expeditiously, but delays occurred when a company with Arctic experience proposed to lease an icebreaker to the government. Consequently, OMB denied replacement icebreaker funding in the 1988 budget. An A-104 lease-buy analysis was completed in 1989 and showed that the net present value of a lease would be 10 to 15 percent more expensive than buying the ship. This finding cleared the way for Congress to appropriate funds to procure one ship. Funding was provided in the Defense budget thereby further slowing actual procurement. HEALY, delivered in 1999, was designed with modern science facilities to meet the increasing demand for Arctic research and has proven highly capable in that role. The characteristics of the current fleet are listed in Table 6.1. THE CURRENT WORLD FLEET OF POLAR ICEBREAKERS The U.S. Coast Guard generally has used the thickness of ice broken continuously at 3 knots as a simple measure of icebreaking capability. Therefore, icebreaking ships for Coast Guard or military owners are not required to be built to meet classification society requirements. However, requirements for the structural integrity of ice-capable ships are specified in the rules of the various classification societies, for example, the Russian Maritime Register of Shipping, Lloyd’s Register, Det Norske Veritas, American Bureau of Shipping, and Germanischer Lloyd, and national regulatory authorities (Canadian, Finnish-Swedish, and Russian). These requirements are divided broadly into Baltic Rules for ice-strengthened vessels and Arctic Class Rules for icebreaking ships. Most classification societies have similar requirements for ice-strengthened vessels or ice type ships, which are divided into classes depending on their design ice thickness of up to 1.2 meters. Local structure design ice pressures depend principally on the ice class and hull area. In contrast, classification society requirements for icebreaking ships have historically varied somewhat in terms of definitions of hull areas, which are strengthened, and design load intensity relative to design ice and operating conditions. An approximate correspondence between different classification societies’ ice classes is shown in Table 6.2. How- TABLE 6.2 Approximate Equivalencies Between Classes Classification Society/ National Administration Approximate Class Equivalents Canadian Arctic Shipping Pollution Prevention Regulations   CAC 1 CAC 2 CAC 3 CAC 4 Type A Type B Type C Type D Russian Maritime Register of Shipping LL1 LL2 LL3 LL4 ULA UL L1 L2 L3 Det Norske Veritas P30 P20 P10 I15 I10 I05 1A* 1A 1B 1C Lloyd’s Register of Shipping LR 3 LR 2 LR 2 LR 1.5 LR 1.5 LR 1 1A 1B 1B 1C Finnish-Swedish Maritime Administrations           1AS 1A 1B 1B 1C 1C Germanischer Lloyd           E4 E3 E2 E1 Bureau Veritas           1AS 1A 1B 1C American Bureau of Shipping           1AA 1A 1B 1C

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Polar Icebreakers in a Changing World: An Assessment of U.S. Needs TABLE 6.3 Approximate Equivalencies Between Classes per ABS (from most ice capable to less ice capable) Baltic ABS Russian Vessel Russian Icebreaker Canadian Proposed IACS   A5   LL1 CAC1 PC1   A4   LL2 CAC2 PC2   A3 LU9 LL3 CAC3 PC3   A2 LU7/8 LL3-LL4 CAC4 PC4-PC5 IAS A1 LU6/LU5 LL4 Type A PC6 IA A0 LU4   Type B PC7 IB B0 LU3   Type C   IC C0 LU2   Type D     D0 LU1   Type E   ever, because the rules are different, any attempt to draw equivalencies is somewhat subjective, and this can place serious restrictions on ships that could conceivably operate in regions governed by different national regulations. For example, the American Bureau of Shipping (ABS) has constructed a recent comparison among selected classification societies shown in Table 6.3 that defines new categories and variations in correspondences. It is also important to note that the International Association of Classification Societies (IACS) has been working on a standard range of ice classifications shown as PC 1 through PC 7. It is anticipated that these will be adopted in the near future and should be helpful in describing the capabilities of ships classified by those societies that belong to IACS. While there are differences, the essential approach taken in the more recently revised rules is to specify maximum design loads based on ship-ice interaction models that have been calibrated with full-scale measurements. The design loads depend on displacement and power and are applied to different structural elements according to a pressure-area relationship. Scantlings are determined using elastoplastic criteria that permit stresses in excess of yield so that some permanent hull deformation is acceptable. Compared to traditional ship structural design methods, this leads to a combination of thinner plate, bigger frames, and larger frame spacing. As noted earlier, the U.S. Coast Guard has generally used the thickness of ice that can be broken continuously at 3 knots as a measure of icebreaker performance; but it was too difficult to extract this information for all icebreakers in the world fleet, and this simple, loosely defined rule-of-thumb cannot be matched consistently to the various ice classification schemes. In seeking a general definition of a polar icebreaker, one authority has developed a listing that includes the following parameters: Having sailed in significant sea ice in either the Arctic or the Antarctic, Ice strengthening sufficient for polar ice, and most significantly, Installed power of at least 10,000 horsepower Historically, ships with lower power levels have successfully operated in polar regions, but as demonstrated by the evolution of U.S. Coast Guard designs in the last 40 years, mass and velocity are the key factors in breaking heavy ice. Propelling heavy ships and/or developing higher speeds requires considerable power. Thus, while information has been obtained and could be provided on as many as 60 icebreaking ships, many of these are not believed truly suited for polar icebreaking. Table 6.4, which draws heavily on data provided by L.W. Brigham (personal communication, October 2000), provides a listing of the current inventory of polar icebreakers organized by country of ownership. Baltic icebreakers have also been included, although it is often a matter of opinion rather than fact which ships have some polar capability. This presentation was chosen to highlight both the fleet size and the key data for various nations having interest in the polar regions. The world fleet of icebreakers with greater than 10,000 horsepower is 50. Russia has the largest fleet. Finland, Canada, and Sweden each operate six to seven icebreakers. The Unites States has four ships, and six other countries have one to three ships. Only Russia has used nuclear propulsion plants (seven ships). Only Russia and the United States operate ships with propulsion greater than 30,000 horsepower. Most icebreakers operate primarily in the Baltic Sea area. Russia is notable for its emphasis on icebreaker tourism. ICEBREAKER TECHNOLOGY In continuous running mode, icebreakers break ice by weight. As an icebreaker is propelled forward, it moves up onto the ice, and the weight of the hull breaks the ice. The traditional icebreaker bow is in the form of a spoon that fa-

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Polar Icebreakers in a Changing World: An Assessment of U.S. Needs TABLE 6.4 Current Polar and Baltic Icebreakers in the World Fleet, February 2006 Ship Name Country of Ownership Year Entered Service Propulsion Plant Operations ARKTIKA Russia 1975 N:75,000 NSR ROSSIYA Russia 1985 N:75,000 NSR SOVETSKIY SOYUZ Russia 1990 N:75,000 NSR; Arctic tourism YAMAL Russia 1993 N:75,000 NSR; Arctic tourism 50 LET POBEDY Russia 2006 (est.) N:75,000 Not yet operational TAYMYR Russia 1989 N:47,600 NSR VAYGACH Russia 1990 N:47,600 NSR KRASIN Russia 1976 DE:36,000 NSR; Antarctic VLADIMIR IGNATYUK Russia 1977 D:23,200 Arctic escort KAPITIN SOROKIN Russia 1977 DE:22,000 NSR; Baltic escort KAPITIN NIKOLAYEV Russia 1978 DE:22,000 NSR KAPITIN DRANITSYN Russia 1980 DE:22,000 NSR; Arctic and Antarctic tourism KAPITIN KHLEBNIKOV Russia 1981 DE:22,000 NSR; Arctic and Antarctic tourism Tourism AKADEMIK FEDOROV Russia 1987 DE:18,000 Arctic and Antarctic research and logistics FESCO SAKHALIN Russia 2005 DE:17,500 Standby or supply vessel, Sakhalin Island SMIT SAKHALIN Netherlands– Russia charter 1983 D:14,500 Beaufort Sea; Sea of Okhotsk; Sakhalin Island SMIT SEBU Netherlands– Russia charter 1983 D:14,500 Beaufort Sea; Sea of Okhotsk; Sakhalin Island MUDYUG Russia 1982 D:10,000 NSR coastal MAGADAN Russia 1982 D:10,000 NSR Pacific coastal DIKSON Russia 1983 D:10,000 NSR coastal URHO Finland 1975 DE:21,400 Baltic escort SISU Finland 1976 DE:21,400 Baltic escort OTSO Finland 1986 DE: 20,400 Baltic escort KONTIO Finland 1987 DE: 20,400 Baltic escort FENNICA Finland 1993 DE:20,000 Arctic offshore/ Baltic escort NORDICA Finland 1994 DE:20,000 Arctic offshore/ Baltic escort BOTNIKA Finland 1998 DE:13,000 Arctic offshore/ Baltic escort LOUIS ST. LAURENT Canada 1969, 1993a DE:30,000 Arctic research and escort TERRY FOX Canada 1983 D:23,200 Arctic escort and logistics HENRY LARSEN Canada 1988 DE:16,000 Arctic escort and logistics AMUNDSEN Canada 1982, 2002b DE:15,000 Research PIERRE RADISSON Canada 1978 DE:13,400 Arctic escort and logistics DES GROSSELIERS Canada 1983 DE:13,400 Arctic research and escort ODEN Sweden 1989 D:23,200 Arctic research/Baltic escort ATLE Sweden 1974 DE:22,000 Baltic escort YMER Sweden 1977 DE:22,000 Baltic escort FREJ Sweden 1975 DE:22,000 Baltic escort TOR VIKING Sweden 2000-2001 DE:18,000 Baltic escort BALDERR VIKING Sweden 2000-2001 DE:18,000 Baltic escort VIDAR VIKING Sweden 2000-2001 DE:18,000 Baltic escort/Arctic research POLAR STAR US 1976 GT:60,000 DE:18,000 Arctic and Antarctic research and logistics POLAR SEA US 1977 GT:60,000 DE:18,000 Arctic and Antarctic research and logistics HEALY US 2000 DE:30,000 Arctic research and response NATHANIEL B. PALMER US 1992 D:12,700 Antarctic research and logistics SHIRASE Japan 1982 DE:30,000 Antarctic research and logistics POLARSTERN Germany 1982 D:17,200 Arctic and Antarctic research and logistics KIGORIAK Netherlands 1979 DE:16,600 Offshore support ALMIRANTE IRIZAR Argentina 1978 DE:16,000 Antarctic research and logistics SVALBARD Norway 2002 DE:13,500 Patrol AURORA AUSTRALIS Australia 1990 D:12,000 Antarctic research and logistics NOTE: D = Geared Diesel; DE = Diesel-Electric; GT= Gas Turbine; N= Nuclear; NSR = North Sea Route. Ships of at least 10,000 propulsion horsepower are listed. aLOUIS ST. LAURENT in service in 1969 was rebuilt and recommissioned in 1993. bAMUNDSEN in service in 1982 as SIR JOHN FRANKLIN was converted and returned to service in 2002.

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Polar Icebreakers in a Changing World: An Assessment of U.S. Needs cilitates this action. The ability of an icebreaker to break ice is, therefore, a function of the ship’s weight (displacement) and propulsive power for forcing it onto the ice. Successful year-round navigation in any area depends on the ability of icebreakers to escort tankers through anticipated ice regimes consistently, with minimum delays and with no additional risk to ships or crew caused by ice conditions (Johansson, 2004). Developments in icebreaker technology in the last quarter-century have been inspired in large measure by the oil industry. Proven technological advances during this period have made it possible to construct reliable icebreakers capable of assisting year-round tanker transportation within the limits of safety and pollution prevention regulation. Ships presently in service demonstrate that this can be accomplished by icebreakers of much less power than many others still operating with older technology (Johansson, 2004). Level ice is broken by using the force of the ship to bend the ice to its breaking point, rather than by crushing it. Early experience and theoretical calculations showed that blunt bow forms with small stem angles could break level ice more efficiently than wedge-shaped bows with larger stem angles (Johansson, 2004). However, problems occur at sea when icebreakers encounter ridges formed by the movement of highly mobile sea ice. The first seagoing icebreaker, MURTAJA, built in Sweden in 1890, had a blunt spoon-shaped bow form that was designed for breaking level ice efficiently. However, the bow pushed ice ahead of the ship, hindering performance at ridges. Seagoing icebreakers were designed with comparatively inefficient wedge-shaped bows, while those built for level ice in lakes and rivers had blunt bows (Johansson, 2004). In 1979, the KIGORIAK was the first seagoing icebreaker since MURTAJA to have a blunt spoon-shaped bow. The KIGORIAK had three major design features. The first was a water wash system that pumps large volumes of seawater onto the ice in front of the ship, which is designed to reduce the friction between the bow and the ice to permit the bow to ride up onto the ice. This ship also employed a stream of water along both sides in an attempt to reduce friction against the hull. The second design feature consisted of reamers fitted to the hull of the ship at the widest part of the hull. The reamers were designed to reduce the friction along the mid-body of the ship. Operating in an asymmetrical fashion, they were designed to break ice by bending it downwards as the ship moves forward and by bending it upwards when the ship moves backward. The reamers create a channel of about 1-meter width on each side of the ship, greatly reducing friction between the ice and the hull and allowing greater maneuverability in ice. The third was the installation of a nozzle surrounding the ship’s propeller, which has the effect of increasing thrust and protecting the propeller from larger ice pieces (Johansson, 2004). In 1982 when the ROBERT LEMEUR was built, low-friction Inerta paint was applied to its hull in an attempt to reduce hull corrosion. (Inerta paint has been used on U.S. Coast Guard polar and domestic icebreaking vessels since the 1970s.) Conventional paint is removed by the ice, and unprotected portions of the hull corrode. The corrosion results in an uneven surface that causes more friction between hull and ice. These improvements in the ROBERT LEMEUR led to a further 20 percent reduction in the power necessary to accomplish the same tasks performed by the KIGORIAK (Johansson, 2004). In 1989, the Swedish icebreaker ODEN, was delivered. The ODEN was built on the ROBERT LEMEUR concept and had 24,000 horsepower. In addition to using the spoon-shaped bow form, Inerta paint, and a hull wash system, the ODEN was fitted with larger reamers than its predecessor and a fast-heeling system. The system pumps water very quickly within the vessel from one side to the other (as much as 800 tonnes in 25 seconds), rocking the ship in heavy ice so that the reamers break the ice at the sides of the ship. In full-scale operation the ODEN has moved at a continuous speed of about 3 knots in 2-meter-thick ice. On several occasions she has reached the North Pole during research expeditions (Johansson, 2004). Two Finnish icebreakers, FENNICA and NORDICA, built in the early 1990s, were built with symmetrical reamers, designed to break the ice by bending it downwards when moving forwards and backwards. The icebreakers were also fitted with two stern propellers that are able to turn 360 degrees around an almost vertical axis. The initial purpose of the rotating propellers was to improve maneuverability in both ice and open water to make dynamic positioning possible in concert with three transverse thrusters in the bow (Johansson, 2004). In 2005 the U.S. Coast Guard accepted delivery and commissioned its newest icebreaker, the MACKINAW (WLBB 30). This icebreaker replaced the 290-foot icebreaker of the same name (WAGB 83), built in 1944 to provide icebreaking services on the Great Lakes. The new MACKINAW is considered a multimission vessel because it was designed both to provide heavy icebreaking services and to maintain floating aids-to-navigation on the Great Lakes. The new MACKINAW incorporates several state-of-the-art icebreaking features including the following: Twin azimuth pod propulsion with the ability to rotate 360 degrees, integrated with a bow thruster for maximum maneuverability in ice and in open water; Integrated electric propulsion system using diesel-powered generators with electric motors in the azimuth pods; Computer-based monitoring and control providing extensive automation of ship maintenance and operation; An integrated bridge system providing the flexibility to operate the ship with only one watchstander; and A podded propulsion system, which is the first ever used on a U.S. Coast Guard vessel and was incorporated in the design after ice tank testing of podded and conventionally shafted models in Helsinki.

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Polar Icebreakers in a Changing World: An Assessment of U.S. Needs Icebreaker technology has changed over the past several decades in four primary areas (Mikko Niini, personal communication): Hull design Auxiliary icebreaking capability Propulsion plant design Dual-role (double-acting) vessel designs Hull Design An icebreaker’s performance is heavily dependent on its hull design. Current icebreaker designs were developed with heavy reliance on historical designs with incremental improvements being driven by model tank testing (ice capable). A primary consideration is control of the flow of broken ice around and under the hull. Protecting the rudder(s) and propellers(s) or propulsion units is of paramount importance in icebreaker hull design. Advances are usually achieved through trial and error in ice tank testing and are validated in full-scale tests. Several new icebreaker concepts have been proposed but not yet put into practice. For example, the oblique icebreaker is an asymmetrical hull design that is meant to enable one small icebreaker to perform the escort service that usually requires two. The specific oblique icebreaker design tested is for a small escort vessel with a 20.5-meter beam overall that is capable of opening a channel in ice more than 40 meters wide in a single pass. Model tank tests showed the design to be viable. Auxiliary Icebreaking Capability Auxiliary icebreaking capabilities include water wash systems where large volumes of water are pumped over the bow to reduce ice-hull friction, and fast heeling systems for rocking an icebreaker in tight ice conditions. In addition, bubbler systems have also been utilized effectively. A bubbler system blows compressed air out under the hull that will exert upward buoyant force on the ice causing it to lift and break. The compressed air also serves as a friction reducer to improve hull performance. Propulsion Plant Design Icebreaker propulsion plants have changed dramatically since the first sail-powered icebreakers. Steam and later diesel engines drove power through reduction gears to fixed pitch propellers. Those systems were prone to mechanical damage as the propeller struck ice chunks broken at the bow. Later, controllable pitch propellers were tried. The current systems use electric drives that decouple the propellers from the prime mover to reduce ice impact damage. (Consider that some of the ice chunks moving under and along the icebreaker’s hull are the size of a school bus). The electric drive systems use propellers connected directly to an electric motor. The electricity to drive the motors is produced by onboard generators. Those generators can be driven by diesel engines, gas turbines, or steam turbines (with either nuclear or conventional fossil fuel boilers). The electric drive systems also give greater flexibility for engine room design and eliminate the need for shafts and reduction gears. To further protect the exposed propellers, nozzles or ducts were installed around the propellers. These had the added benefit of increasing thrust by improved water flow. The current state of the art in icebreaker electric drive with power units is considered to be azimuth pod drives (as installed on the latest U.S. Coast Guard icebreaker MACKINAW); however, some consider them to still be in the developmental stage and unreliable. An azimuth pod drive is an enclosed unit that hangs below the hull and contains the electric drive motor attached directly to a propeller. The azimuth pod is capable of being rotated 360 degrees, enabling full thrust to be applied in any direction very quickly. Azimuth drives have been used extensively on cruise ships and other commercial vessels including ice-strengthened ships. It is anticipated that the next generation of icebreakers will likely be equipped with azimuth drives. The biggest challenge is building larger azimuth drive units to power icebreakers capable of working in multiyear ice. The goal is to build single-unit azimuth drives capable of 25 megawatts (~33,000 horsepower). Current azimuth drives are available up to 20 megawatts (~26,000 horsepower). Additional work is being done on improving the efficiency of the electric drive systems such as those using AC–AC drives. Dual-Role (Double-Acting) Vessel Design Possibly the most innovative concept to emerge in recent years in icebreaker technology has been the introduction of double-acting hull designs. A vessel with a double-acting hull has standard seakeeping characteristics when moving forward. The vessel is reversed with an icebreaking stern shaped for breaking ice. This concept has been used on a range of vessels including offshore supply vessels (e.g., FESCO SAKHALIN, delivered 2005), general purpose or container ships (e.g., NORILSKIY NICKEL, delivered 2006), and AFRA-max tankers (MT TEMPERA and MT MASTERA, delivered 2003). Azimuth pod drives have been installed on double-acting ships. It is possible that the next-generation polar research vessel will incorporate a double-acting hull design (to improve seakeeping while in transit to the polar region) with twin azimuth pods, diesel-electric power plants (efficiency and emission considerations), redundant machinery (safety and reliability), and extensive use of stainless steel (hull and propellers). It is not yet clear, however, if the double-acting hull design is completely applicable for a polar icebreaker, which must occasionally work in the heaviest navigable ice, where frequent back-and-ram operations are required.

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Polar Icebreakers in a Changing World: An Assessment of U.S. Needs Icebreakers Under Construction There are currently six icebreakers under construction in the world’s shipyards: Construction of a large Russian icebreaker of the existing ARKTIKA class has been under way for more than 10 years, with commissioning expected in October 2006. The nuclear icebreaker is 522 feet long with a 100-foot beam. It is reported at 25,000 deadweight (deadweight is a measure of cargo capacity, whereas displacement is usually reported for icebreakers), making it the largest nuclear icebreaker in the world. This icebreaker was originally named URALS but now appears to be named 50 LET POBEDY. Two offshore icebreakers are being built at Aker Yards for the Sakhalin 2 project (offshore oil development in the Russian Far East). One terminal icebreaker at Aker Yards is planned for the Sakhalin 1 project (offshore oil development in the Russian Far East). Two Baltic Sea escort icebreakers (diesel powered) are under construction at Baltic Shipyard, Russia, for Rosmorport of Russia. Five of the six icebreakers under construction are being built for specific commercial operations. The sixth, the Russian nuclear icebreaker, is being built for general Arctic operations support. Shipbuilding for Arctic operations is focused primarily on building ice-strengthened commercial ships such as oil tankers, offshore supply vessels, bulk carriers, and container ships. Ice-strengthened liquefied natural gas tankers are also being planned. U.S. POLAR ICEBREAKER OPERATIONS IN THE LAST TWENTY YEARS The mission deployment of U.S. polar icebreakers has evolved in the last half-century. During World War II, the Arctic became for the first time a national security concern, and this perspective of the Arctic, as a zone of defense, extended seamlessly into the Cold War period. The operational focus for icebreakers was concentrated in these years almost exclusively on defense-related logistics. Postwar Antarctic operations took on a similar military character, where even after the International Geophysical Year (1955-1956) the massive logistics of the U.S. science program continued to be conducted as military operations. The beginnings of mission change were indicated by the Navy’s decision to leave the icebreaker business in the 1960s, which signaled the end of polar logistics as a naval mission of importance. By the 1980s, science activities overshadowed the remaining defense logistics mission in Greenland, where the abandonment of bases left only Thule with a requirement for sealift. The need for better polar science capabilities was a key theme of the 1984 Polar Icebreaker Requirements Study. Increasing interest in polar research brought new users, from the Department of Defense science establishment and from civilian agencies such as the National Oceanic and Atmospheric Administration, U.S. Geological Survey (USGS), Maritime Administration, and academic associates of their programs. In 1970 the National Science Foundation assumed overall management of the U.S. Antarctic Program. The U.S. Coast Guard icebreaker fleet began to be operated with other agencies requesting specific cruises and funding the fuel and variable costs on a reimbursable basis. Throughout the 1980s and 1990s, POLAR STAR and POLAR SEA alternated deployments to Antarctica each year to conduct the McMurdo break-in, Palmer Station resupply, and other logistics and science tasking. On two occasions a second Polar class ship went south either in standby status (1988) or to perform Antarctic Treaty inspections (1995). Until decommissioning in 1987 (after her twenty-ninth Antarctic deployment), GLACIER also spent several months of the Antarctic summer each year conducting science support in the vicinity of the Weddell Sea and Antarctic Peninsula. The POLAR SEA and POLAR STAR performed the heavy icebreaking associated with the break-in, while GLACIER generally operated in open water, the marginal ice zone, and sea ice where demanding icebreaking was rarely required. In the western Arctic—the Bering, Chukchi, and Beaufort Seas—either POLAR STAR or POLAR SEA usually deployed during the summer and fall months each year. The work was almost entirely research related in a variety of disciplines, for USGS, NOAA, and both classified and unclassified work for the Office of Naval Research. Both POLAR STAR and POLAR SEA conducted a series of trafficability studies, under MARAD sponsorship, to measure shipboard stresses and icebreaking performance in various ice conditions. These cruises occurred in the Chukchi and Bering Seas in both summer and winter conditions. In 1984, POLAR SEA was nipped between two moving ice sheets north of Prudhoe Bay for five days and faced the prospect of wintering over. Fortunately, a combination of transferring weight aft and using full power, the heeling system, and an ice anchor implanted off the stern freed the ship. The trafficability research program sought to provide design knowledge for icebreaking commercial ships, especially for crude oil transport, and was completed by the late 1980s. The annual resupply of Thule Air Base necessitated the presence of an icebreaker in the eastern Arctic every summer, although ice conditions were variable and actual vessel ice escort was needed infrequently. This mission requirement—“Operation Pacer Goose”—was satisfied easily by the East Coast-based NORTHWIND or WESTWIND, often in conjunction with research work for the International Ice Patrol, until 1988. From 1989 until 1993, either the POLAR STAR or the POLAR SEA was deployed from Seattle for Pacer Goose. Although research projects were usually inte-

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Polar Icebreakers in a Changing World: An Assessment of U.S. Needs grated into these lengthy deployments, icebreaker standby for Thule was provided more efficiently by an agreement with the Canadian Coast Guard in 1993. In 1985, POLAR SEA made a rare transit of the Northwest Passage in order to facilitate her return from Thule. The only U.S. vessels to have previously made the passage were three ice-strengthened Coast Guard cutters in 1957 and NORTHWIND in company with the tanker MANHATTAN demonstration project in 1969. POLAR SEA’s transit aroused considerable Canadian concern over sovereignty issues and the status of the waterway. The need for routine use of the Northwest Passage by U.S. icebreakers resulted in a practical agreement with Canada. In 1988, heavy pack ice moved down to Point Barrow and blocked POLAR STAR’s western exit from the Beaufort Sea, requiring an escape to the east via the Northwest Passage and return to Seattle via the Panama Canal. Subsequent transits of the Northwest Passage were made by POLAR STAR in 1989 and HEALY in 2000 and 2003. By 1990, the U.S. polar icebreaker fleet consisted only of POLAR STAR and POLAR SEA. Nevertheless, the early 1990s were a period of especially active operations. The POLAR STAR and POLAR SEA operated in the eastern Arctic annually for six consecutive years, while still continuing to meet McMurdo Sound tasking and occasional western Arctic cruises as well. During these years the POLAR STAR and POLAR SEA also underwent major system upgrades to their science equipment and laboratories. Arctic science expeditions became larger and more international. The ambitious International Arctic Ocean Expedition sought to reach the North Pole from the Norwegian Sea in 1991, but U.S. participation had to be aborted when POLAR STAR suffered damage to a propeller shaft. However, the challenging Northeast Water Polynya projects (NEWP I and II) were completed successfully in northern Baffin Bay in 1992 and 1993. POLAR SEA crossed the Arctic Ocean via the North Pole in company with LOUIS ST. LAURENT in 1994, historic “firsts” for both the United States and Canada. The latter half of the 1990s were leaner operational years. Antarctic operations continued routinely, although in 1998 POLAR STAR towed the resupply tanker 1,500 nautical miles from the Ross Sea to New Zealand after the much larger vessel lost propulsion. However, few Arctic deployments were funded by other agencies. The Coast Guard initiated and funded several science-of-opportunity cruises to the Chukchi Sea, some deep into the Arctic pack, in order to maintain proficiency and meet increasing science needs. POLAR SEA began one of these cruises by participating in a multinational oil spill exercise near Sakhalin Island and ended it with a diversion to change out the crew and science party of the Canadian icebreaker DES GROSEILLIERS, which had drifted unexpectedly beyond air resupply range during a 13-month in-ice drift project. The icebreaker fleet gained new capacity and capability, especially with regard to research in the Arctic, with HEALY’s delivery in 2000. After completing ship performance and science testing and arriving in Seattle via the Northwest Passage, HEALY conducted a challenging geologic exploration of the Nansen-Gakkel Ridge northeast of Greenland for her first research cruise in 2001. Since that time, the new icebreaker has conducted annual Arctic deployments between April and November. HEALY deployed to the western Arctic in 2002 and 2004, worked in both western and eastern areas in 2003 and 2005, and had spring and summer projects scheduled for the Bering and Chukchi Seas in 2006. The Antarctic resupply mission has become increasingly challenging since 2000. With ice dynamics in McMurdo Sound disrupted by massive tabular icebergs calved from the Ross Ice Shelf, the annual break-in has faced multiyear ice and fast ice extents up to three times the normal situation. Both POLAR STAR and POLAR SEA were deployed in 2002 and 2004, and HEALY was dispatched at short notice to assist in 2003, between Arctic summer missions. The small U.S. fleet could not sustain the pace of two-ship operations at McMurdo; HEALY could make the long deployments south only by curtailing planned Arctic science missions significantly, and both POLAR STAR and POLAR SEA faced serious age-related mechanical problems requiring extended time in a shipyard. Accordingly, the Russian icebreaker KRASIN was chartered to assist POLAR STAR in 2005. In 2006, KRASIN attempted the break-in alone but broke a propeller blade before escorting the tanker and container ship through difficult ice conditions. U.S. Navy divers were unable to replace the propeller blade. POLAR STAR was dispatched from standby in Seattle and made a direct transit to McMurdo Sound. Fortunately, the supply ships successfully delivered their cargoes by the time POLAR STAR arrived, leaving her only some grooming work for next year’s airfield. POLAR SEA completed extensive repair and maintenance work in June 2006 and deployed to the Arctic in July and August. POLAR SEA is scheduled to conduct the break-in early in 2007. To save money, POLAR STAR has been laid up with a small caretaker crew. KRASIN will be unavailable in 2007, and prospects for an assisting or backup icebreaker are unknown.

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