What does it take to reach the bottom of the world?
For starters, you’ll need a well-designed hull, tapered like a football for maximum maneuverability. Then add a generous supply of horsepower; 75,000 is a good round number. Finally, you’ll need some weight to help break the thick ice, about 13,000 tons. To round this equation out you’ll need experience, especially the understanding that the best way to operate an icebreaker is to avoid ice in the first place.
In short, there’s no single factor that makes the Coast Guard Cutter Polar Star‘s icebreaking possible. It’s an art that began with the first sketches of its blueprint and is still being perfected each time a new ice pilot qualifies to drive the 399-foot cutter. Each winter (summer in the Southern Hemisphere, Polar Star’s normal operating area) the crew is run through an icy gauntlet that tests every element of the ship’s capability.
“We began seeing sea ice near 62 degrees latitude south, but the pack ice we found further down was no real challenge as it was under heavy melting stress, rapidly retreating and further narrowed by a growing polynya, or ice-free area, opening northward from the other side,” said Pablo Clemente-Colón, the U.S. National Ice Center‘s chief scientist, who just happens to be aboard the Polar Star for their 2016 mission. “Then we hit the fast ice, where we are now; where the work starts.”
The work indeed started in McMurdo Sound with 13 miles of ice between the open Ross Sea and the U.S. Antarctic Program’s McMurdo Station 18 days prior to the first supply ship’s arrival.
First, the cutter collides with the edge of the fast ice at about six knots. The 13,000-ton cutter’s 1.75-inch thick steel bow and the aforementioned power and weight come into the equation here, upon initial approach toward McMurdo Station.
“We have diesel electric engines for general open-ocean steaming and some grooming of very light ice, up to six feet of ice,” said Lt. Cmdr. Kara Burns, the Polar Star’s engineer officer. “Then we have what we consider our boost mode, our main gas turbines. They really allow us to get through six feet of ice or upwards to 21 feet of ice when we’re backing and ramming.”
Those gas turbines, enormous pieces of machinery that can each transform jet fuel into 25,000 horsepower, are the key to putting the Polar Star where it needs to be: above the ice. When the cutter rams a thick plate, that power drives the rounded bow up on top of the ice, at which point gravity takes over.
“We carry three times the fuel capacity of a 378 or a [national security cutter],” said Burns, comparing the Polar Star to the Coast Guard’s largest non-icebreaking cutters. “The extra weight on the ship, as far as the liquid load capacity, is used as a cantilever mechanism. As the vessel rides up on the ice, the hydrostatic pressure forces the stern up and pushes the bow down, acting as a hammer on the ice.”
In this case, the world’s biggest hammer.
Rest assured control of such awesome power is not handed out on a whim. It’s only after qualifying to maneuver the cutter in normal open water conditions, and a meticulous review from the commanding officer, that a new ice pilot is able to take the throttles and the helm from the ship’s aloft conn: a small control center five stories above the highest deck.
“They have to understand the different kinds of ice; they have to understand the ship’s capabilities and its limitations, and how to break ice safely,” said Capt. Matthew Walker, commanding officer, Polar Star. “The best way to break ice is to avoid ice, but when we’re down here we can’t do that.”
If the Polar Star crews of years and decades past hadn’t given the ice its due respect, the ship wouldn’t have made it to the 40th birthday it had in January. Before it comes to backing and ramming, the ice pilot has to know to dodge, or at least look for thinner ice when possible.
Carefully navigating through wayward floes in the Southern Ocean and beginning to break only when necessary, the crew accomplished another trip from one side of the planet to another. The grunt work, the supply vessel escort of Operation Deep Freeze 2016, the U.S. military’s logistical support of the NSF’s U.S. Antarctic Program, lies ahead.
With power and weight, with lessons passed down from one crew to the next, and with a hull made particularly for this type of work, the Polar Star moored at McMurdo Station Jan. 18, 2016. They’re as far from their home in Seattle as they could possibly be, but on familiar ground at the bottom of the world.