[16] However, already in the late 1800s captains operating ships in icebound waters discovered that sometimes it was easier to break through ice by running their vessels astern.

This was because the forward-facing propellers generated a water flow that lowered the resistance by reducing friction between the ship's hull and ice.

[17] These findings resulted in the adoption of bow propellers in older icebreakers operating in the Great Lakes and the Baltic Sea, but as forward-facing propellers have a very low propulsion efficiency and the steering ability of a ship is greatly reduced when running astern, it could not be considered a main operating mode for merchant ships.

[18][19] For this reason it was not until the development of electric podded propulsion, ABB's Azipod, that the concept of double acting ships became feasible.

The 90,000 DWT tankers were designed to transport oil and gas condensate from the Pechora Sea in the Russian Arctic, where ice conditions during winter can be considered moderate and the ships would operate mainly in astern mode, first to Murmansk and then Rotterdam, where most of the distance can be travelled in open water year round.

The old ships had traffic restrictions during the worst part of the winter because of their lower ice class of 1C and could not deliver their cargo all the way to the refineries in Porvoo and Naantali because they were denied icebreaker assistance.

[19] To solve these problems Kværner Masa-Yards Arctic Research Centre developed a new 100,000 DWT Aframax tanker concept together with Fortum Shipping, which ordered two vessels from Sumitomo Heavy Industries in 2001.

[24] While the price of the contract was not made public, the company later admitted that the 60–70 million euro estimate was "quite close to the truth".

[25] Occasionally they also carried cargoes in the Gulf of Bothnia and even outside the Baltic Sea depending on the amount of oil in the refineries' storage tanks.

[2] In March 2022, the 19-year-old Mikines appeared on list of tonnage sold for demolition,[31] but resumed trading and was renamed Alma in June 2022.

The stern is, however, shaped like an icebreaker's bow, and the vessel is designed to operate independently in the most severe ice conditions of the Baltic Sea.

[13] The ship has diesel-electric powertrain with four main generating sets, two nine-cylinder Wärtsilä 9L38B and two six-cylinder 6L38B four-stroke medium-speed diesel engines, with a combined output of 20 MW (27,000 hp).

[8] When built, Mastera and her sister ship were the first tankers propelled by ABB Azipod electric azimuth thrusters capable of rotating 360 degrees around the vertical axis.

The pulling-type VI2500 pods in these two ships, with a nominal output of 16 MW and 7.8-metre (26 ft) fixed-pitch propellers turning at 86 rpm, are the most powerful ice-strengthened Azipod units ABB has ever produced.