Polaris: the no-compromise Baltic Sea assistance icebreaker
In 2012, the Finnish government authorised the procurement of a new Baltic Sea assistance icebreaker. The aim was to develop a novel concept for the challenging ice conditions in the Bay of Bothnia – one that would surpass the capabilities of any previous icebreaker in the region. The successful result was Polaris, a true game-changer in the field of icebreaking.
The northern Baltic Sea between Finland and Sweden – the Gulf of Bothnia, and in particular its northernmost part, the Bay of Bothnia – is characterised by ridged ice fields under pressure, dense brash ice belts, and narrow ice channels. These create extremely demanding conditions for commercial traffic during winter. To maintain the flow of imports and exports, icebreakers are the cornerstone for keeping navigation lanes open and assisting cargo and passenger vessels transiting the area.
Challenging established ideas to redefine icebreaking
The Finnish Transport Agency (now the Finnish Transport Infrastructure Agency), which was tasked with procuring the design and construction of the new icebreaker, sought to challenge established norms and redefine how icebreaking and assistance operations could be improved – aiming to raise efficiency to an entirely new level. The success of Finnish icebreaker projects has always been based on fit-for-purpose, tailored designs.
Their goal was to create an icebreaker with superior operational and assisting capabilities, specifically tailored to the conditions of the Bay of Bothnia. The benchmark was set at a minimum of the same level of performance as the Urho-class icebreakers built in the mid-1970s.
This represented a new, qualitative way of setting targets for overall operational icebreaking capability. In the past, performance had been defined solely in quantitative terms, using numerical values or – as was the case with the Urho class – using the propulsion power as the only metric.
“It required translating an operational requirement into measurable and verifiable technical terms,” explains Chief Designer Mika Hovilainen from Aker Arctic Technology.
The baseline was established through extensive ice model tests for Urho, using testing methods that were not available when the icebreaker was built. These tests provided ice manoeuvrability and performance benchmarks that served as the reference points against which new, innovative ideas were measured.
Two concepts selected for further study
Aker Arctic won the design tender. The contract, signed in 2013, included the development of two outline-level concept alternatives as part of a two-month rapid Concept Exploration Phase and, following the selection of a single concept, the development of the final contract design.
The two outline-level concepts were, first, a conventional design with an icebreaking bow and two azimuthing propulsion units in the stern, and second, a novel design featuring a third propulsion unit in the bow – an unprecedented configuration with no parent design, inspired by the Finnish Transport Agency’s forward-looking vision.
A groundbreaking propulsion configuration
Following evaluation, the Finnish Transport Agency selected the concept with the novel propulsion configuration for the final contract design development, due to its exceptional operational potential.
Although the oblique icebreaker Baltika featured a bow propulsion unit to enable its unique sideways icebreaking mode, Polaris introduced the third azimuthing propulsion unit primarily to enhance the vessel’s overall capability in demanding Baltic Sea ice conditions and icebreaking assistance operations. The result is increased manoeuvrability, and thus safety, when escorting ships through ridged ice, cutting free beset vessels, and towing them in the stern notch.
Aker Arctic had already gathered extensive experiences from developing the Double Acting Ship (DASTM) technology for Arctic container ships in the previous decade. These ships demonstrated impressive ridge penetration when operating astern using azimuthing propulsion, due to the hull flushing effect created by having a propulsor on the icebreaking end of the vessel.
Jarkko Toivola from the Finnish Transport Agency also recognised the benefits of azimuthing bow propulsion for close towing – and was proven right. Using the bow propulsion unit in close towing improves both the safety and effectiveness of the propulsion thrust, versus having stern propulsors spinning in close proximity to the towed vessel.
The propulsion configuration became the defining feature of Polaris, with her close-towing capabilities being dramatically improved compared with other Baltic icebreakers. This has been proven by long-term statistics.
“The successful propulsion configuration has since become the new standard in icebreaking,” Hovilainen adds.
Greater efficiency brought fewer assistance needs
To meet the original performance requirements, Polaris would have needed just 15 MW of propulsion power. However, when it was found that the cost impact of an upgrade was negligible, this was increased to 19 MW, significantly enhancing her operational capability.
Polaris can use the flush from her propulsors to clear ice around assisted vessels and maintain ice channels more effectively, reducing the need for close towing. When towing is necessary, Polaris performs the operation faster and with greater manoeuvrability than previous generations of icebreakers, allowing her to assist more vessels in less time.
“She represented a huge leap beyond all previous generations of Finnish icebreakers, achieving more with the same effort,” notes Hovilainen.
Multiple innovations in the design
While the propulsion configuration was Polaris’ most significant innovation, the vessel incorporated several other novel features.
In addition to her bow form, which required a new line of thought, Aker Arctic’s traditional double-wedge stern was further refined to improve turning capability. One of the lessons learned from past icebreaker projects was that azimuthing propulsion alone does not guarantee sufficient manoeuvrability for a Baltic Sea assistance icebreaker.
The design also introduced a dual-fuel power plant using liquefied natural gas (LNG) as the primary fuel – a first of its kind for icebreakers. At that time, LNG was considered a more climate-friendly option than marine diesel oil (MDO), and the Finnish government supported its adoption.
However, incorporating LNG posed challenges. Both technology and regulations were still evolving during the concept development phase, requiring careful design decisions and adaptations during construction. As a cryogenic liquid, LNG must be stored in specialised tanks, limiting placement options on board. Additionally, since LNG must be kept cold year-round, this proved challenging for a seasonally operating vessel.
Polaris was also the first Finnish icebreaker to include a built-in oil recovery system. Making full use of her capabilities and agility, Polaris is able to perform oil spill recovery operations in harsh weather and icy conditions. This required design considerations, such as integrated tank capacity, ice-strengthened equipment hatches, and adequate heating systems – vital to her oil recovery role.
Designed with the Baltic Sea environment in mind, Polaris combines fuel-efficient icebreaking, dual-fuel capabilities, oil recovery, and a zero-dumping policy to minimise her environmental impact as much as technology allowed at the time.
Tests confirmed all requirements
The new concept was verified through multiple model tests during the contract design phase. Following construction, extensive sea trials confirmed superior course stability (both ahead and astern), exceptional manoeuvrability, and excellent open-water speed and bollard pull, both forward and aft. The power plant showed rapid response times, regardless of fuel type.
In January 2017, she departed from her home port of Helsinki for her first operational season in the Bay of Bothnia, which she was specifically designed for. Captain Pasi Järvelin, who had overseen two years of construction, immediately praised Polaris’ agility.
Later that season, in March 2017, official ice trials were conducted. A team of four Aker Arctic experts – Topi Leiviskä, Toni Skogström, Tuomas Romu, and Juha Ala-Soini – spent five days on board verifying that all design requirements were met.
Departing from the port of Oulu, they encountered a 10-metre-thick, 95-metre-wide ice ridge, which Polaris penetrated with ease while going forward. A second ridge, 13.6 metres thick, was also crossed effortlessly with slight wiggling of the azimuthing thrusters.
Performance trials in 72-centimetre-thick level ice with a flexural strength of 600 kPa were a success: Polaris achieved a speed of 12.7 knots ahead and 12.2 knots astern. Near Kemi, the icebreaker maintained a speed of 14 knots in a brash ice channel where the ice rubble was 174 centimetres thick. Turning tests in 60–90 cm ice demonstrated that, if needed, Polaris is able to turn on the spot.
“After the first winter, Polaris was clearly the best icebreaker I had ever worked on,” said Captain Järvelin following the trials. His opinion has not changed over the years.
A new generation begins
Polaris was the first vessel in a new generation of icebreakers and the Aker ARC 130 design family. Two years after her delivery, two larger and more powerful icebreakers for Arctic use were completed, based on the Aker ARC 130 A design, which featured the same propulsion configuration.
Polaris also became the inspiration for Sweden’s next-generation icebreaker design, the Aker ARC 130 S. One of the concept alternatives evaluated for Finland’s upcoming icebreaker, the Aker ARC 130 B+, features a similar three-thruster propulsion layout.
Senior Naval Architect Tuomas Romu emphasises, however, that new vessels designed more than a decade after Polaris should not – and in some cases cannot – be copies of the old concept, due to increased operational experience, technological development, and evolving regulations.
“While the concept of three propulsion units remains, and there may be visual similarities, the hull form and internal layout of the new Swedish and Finnish vessels will be fundamentally different,” he says.
Icebreakers are built to last decades
Polaris brought icebreaking on the Baltic Sea to an entirely new level and remains the most advanced icebreaker built for the region. Larger and more powerful, she is also more agile and efficient. Many of her design elements have since become standard in icebreaker development. The acquisition process itself was notably efficient, achieved in just 3.5 years.
“With the weather and environmental changes we have seen in the Baltic over the past decade – less level ice and more ridged fields and brash ice belts – Polaris has proven to be an extremely efficient tool,” says Hovilainen.
However, she was only the beginning. Later vessel concepts with further refined hull forms have improved energy efficiency and assistance performance. Today, newer technologies and alternative fuels, such as methanol, offer additional climate-smart options.
“The shelf life of a design is limited,” notes Romu. “To reduce lifetime costs for a 50-year investment, we must apply the latest innovations in technology, emissions, and safety during design. Otherwise, a vessel risks being outdated even before construction ends. Therefore, continuous development and innovation are essential to our work at Aker Arctic – for the benefit of our clients and the shipyards constructing our designs.”
| Technical specifications |
|---|
Builder: Arctech Helsinki Shipyard, Finland (yard number 510) |
Length: 110 metres |
Beam: 24 metres |
Design draught: 8 metres |
Max draught: 9 metres |
Tonnage: 3,000 DWT |
Ice Class: PC4 icebreaker (+) |
Installed power: 2 × Wärtsilä 9L34DF, 2 × Wärtsilä 12V34DF, 1 × Wärtsilä 8L20DF |
Propulsion: three ABB Azipod VI1600 units, 1 × 6 MW (bow), 2 × 6.5 MW (stern) |
Speed: 17 knots in open water, 4 knots in 1.8 m level ice |
Endurance: 20 days on MDO |
Design is the most critical success factor
Investing in an icebreaker is a decision that spans 50 years. Success depends on choosing a vessel design that performs reliably throughout its lifetime, while keeping operating costs under control. At Aker Arctic, we know what it takes.
With a proven track record of 59 built and delivered vessel designs over the past twenty years, 700 model test series, and 150 full-scale trials in diverse ice conditions worldwide, we have refined the formula for a successful vessel that will ensure return on investment and lifecycle value for half a century. Polaris is a shining example of this approach.
1. The customer – the Finnish Transport Agency – had a clear vision of the icebreaker they required.
2. The vessel was tailored for its primary tasks – icebreaking and assistance duties in the northern Baltic Sea – drawing on Aker Arctic’s decades of accumulated know-how.
3. Innovative technology was integrated to ensure that lifetime costs remain manageable for taxpayers.
4. Close collaboration between the customer, designer, and shipyard ensured that Polaris progressed on schedule. She was designed and built within just 36 months.
This year, we celebrate Aker Arctic Technology’s 20th anniversary as an independent ice technology company. In 2005, the ice technology expertise was transferred from Helsinki Shipyard to Aker Arctic, allowing our ice experts to focus entirely on icebreaker design and maintain global leadership in this demanding field. Since then, we have been involved in more than half of the world’s icebreaker projects. Every icebreaker design is mission-specific and tested in real conditions – ready for sea ice before it ever touches the sea.
Ice, as an engineering material, is inherently unpredictable because it exists close to its natural melting point. Only ongoing research can take this factor into account. Every Arctic marine environment is different, with ice types that vary greatly across regions and seasons. Navigating in ice requires specialised knowledge based on experience. At Aker Arctic, these are challenges we continue to address – and advance – every day.
Text: Catarina Stewen
