USCG Polar class breakers have been servicing ice-bound ports in Antarctica for decades. I was stationed on the Polar Sea back in the mid-80s. Those ships have some amazing capabilities. The article is a little conservative.
Yes, they can easily steam continuously through ice that’s six feet thick. But by backing and ramming they can break ice far thicker. 20 feet for sure... But in ice breaking a lot depends on the age of the ice. Ice gets harder the older it is. Some of that ice has been frozen since the Romans were in Britain. That stuff is harder than concrete. Stuff that’s freshly frozen will break easier.
The Polar Sea got stuck at one point on an ice ridge that was 70ft thick. Ice ridges happen were two massive sheets come together. Like tectonic plates they mash into one another, or subduct, or whatever... And create massively thick ridges that go both up and down... Seriously not something you want to ram into. But it happens. We had to go out on the ice and bury ice anchors behind the ship and winch ourselves back off it. :-)
The Polar class are seriously powerful breakers. Normally they run on a diesel-electric combo... But when serious power is needed they’ve got three gas turbines that direct-drive the three shafts through a mind-numbing reduction gear. The props are sixteen feet in diameter, stainless steel, variable pitch. The shafts keep turning at a constant RPM, and forward-reverse and speed is handled with pitch on the props. The brute force possible with just a slight pitch is something to behold.
Gentlemen!
Thanks, that was excellent information, I had no idea.
And those of who were icebreaker vets, thank you for your valiant service and hardship.