29 June, 2016 by Staff Reporter
The US polar icebreaker fleet currently includes three ships — two US Coast Guard ships and one ship operated by the National Science Foundation. The icebreakers are multi-mission ships that can break through ice, support scientific research operations in both Arctic and Antarctic waters, and perform other missions typically performed by Coast Guard ships. Of the Coast Guard’s two polar icebreakers, the largest is a 122m “heavy” icebreaker called Polar Star.
Polar Star is one of the largest ships in the US Coast Guard and one of the world's most powerful non-nuclear ships.
Operating out of its home port in Seattle, Washington, the Polar Star was specifically designed for open-water icebreaking, and its features include a reinforced hull, special icebreaking bows, and a system that allows rapid shifting of ballast to increase the effectiveness of its icebreaking. The high-powered diesel engines aboard the Polar Star, as well as its uniquely designed hull, allow the vessel to break through ice more than six metres thick, and to power through ice around a metre thick with minimal effort.
The Polar Star's hull is so strong that it can absorb the high impact of its ice-breaking duties. The hull’s strength is produced almost entirely from the ship’s massive internal support structure. Its shell plating and internal support structures are fabricated from steel that has especially good low-temperature strength.
Polar Star's hull shape is designed to maximise 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 buoyant stern. The curved bow allows Polar Star to ride up onto the ice, using the ship's weight to break through.
With such a sturdy hull and high power to back it up, the 13,200 metric ton Polar Star is able to break through ice up to 6.4 m thick by backing and ramming, and can steam continuously through 1.8 m of ice at 5.6 km/h.
The Polar Star has a variety of jobs while operating in polar regions. During Antarctic deployments, its primary role is to break a channel through the sea ice in order to resupply the McMurdo Research Station in the Ross Sea. Resupply ships use the channel it creates to ship food, fuel and other goods to the station, to ensure it makes it through Antarctica’s harsh winter.
The ship also serves as a scientific research platform, housing five laboratories and accommodation for up to 20 scientists. The Polar Star is used mostly as a research vessel for geology, vulcanology, oceanography and sea-ice physics, amongst other disciplines.
Polar Star carries two helicopters during major deployments, which support scientific parties, as well as completing ice reconnaissance, cargo transfer, and assisting with search and rescue missions.
Polar Star was commissioned into service on January 19, 1976, and is now several years beyond its intended 30-year service life. Due to worn-out electric motors and other problems, the Coast Guard placed the ship in caretaker status on July 1, 2006. The US government provided funding to repair the Polar Star and return it to service, reportedly at a cost about $57 million, and the ship was reactivated on December 14, 2012.