"....Polar Star has sufficient hull strength to absorb the high-powered ice breaking common to her operations. The shell plating and associated internal support structure are fabricated from steel that has especially good low-temperature strength. The portion of the hull designed to break ice is 1-3/4 inches (45 mm) thick in the bow and stern sections, and 1-1/4 inches (32 mm) thick amidships. The hull strength is produced almost entirely from the massive internal support structure. Polar Star's hull shape is designed to maximize icebreaking by efficiently combining the forces of the ship's forward motion, the downward pull of gravity on the bow, and the upward push of the inherent buoyancy of the stern. The curved bow allows Polar Star to ride up on the ice, using the ship's weight to break the ice.
With such a sturdy hull and high power to back it up, the 13,000-ton (13,200 metric ton) Polar Star is able to break through ice up to 21 feet (6 m) thick and steam continuously through 6 feet (1.8 m) of ice at 3 knots (6 km/h)........ More
