Arktika-class icebreaker
The "Arktika" class is a Russian (former Soviet) class of nuclear-powered icebreakers. Formerly known as "Project 10520 nuclear-powered icebreaker", they were the largest and most powerful icebreakers until the 2016 launch of the ship named Arktika. Ships of the "Arktika" class are owned by the federal government, but were operated by the Murmansk Shipping Company (MSCO) until 2008, when they were transferred to the fully government-owned operator Atomflot. Of the ten civilian nuclear-powered vessels built by Russia (and the Soviet Union), six have been of this type. They are used for escorting merchant ships in the Arctic Ocean north of Siberia as well as for scientific and recreational expeditions to the Arctic.
Otso (icebreaker)
During extensive ice trials in the Bothnian Bay in March 1986, "Otso" was put through a series of test to determine her icebreaking capability. In a race against the 1975-built "Urho" in level ice, "Otso" beat the older but more powerful four-propelled icebreaker by more than a ship's length, showing that in terms of ice resistance the new icebreaker was superior to her predecessor. In ice, she could easily maintain a speed of and small ice ridges along the way appeared to be of no consequence to the vessel. However, the strength of the new icebreaker was put to the ultimate test when she encountered a large pressure ridge reaching all the way to the seafloor some below the surface. After preparations, "Otso" was accelerated to a speed of and rammed into the ridge at full power. Since the new icebreaker had a smooth inclined stem and lacked the bow propellers of her predecessors, she rode up the ridge and began listing to the port side as the hull rose from the water. After coming to a stop, "Otso" slid back by herself without utilizing the engines, and the ridge was penetrated on the second charge. The robustness of the ship and its propulsion system were further proven when the icebreaker was backed into a ridge at "to prove to the customer it doesn't break".