Steerprop Builds Record-Size Azimuth Propulsors for Germany’s New Polarstern

Post by : Avinab Raana

Steerprop, a propulsion specialist from Finland, has won the contract to supply what are now the largest mechanical azimuth propulsors ever built for a polar research vessel. These units will power Germany’s next-generation icebreaker, the new Polarstern, built for the Alfred Wegener Institute. The decision reflects rising demands for vessels that can operate reliably in extreme polar conditions, conduct precise scientific research, and minimize environmental impact.

SP 160 PULL ARC Units

Each of the two propulsors Steerprop will deliver is an SP 160 PULL ARC mechanical azimuth unit, rated at 9 megawatts. The propellers themselves are 4.8 meters in diameter. These aren’t just numbers, they matter because of what the vessel must endure. The Polarstern is required to maintain steady progress of 3 knots through multiyear ice up to 1.8 meters thick with 20 percent snow cover. That is a severe ice load. The size, power and design of these propulsors mean the Polarstern will be able to break through ice, manoeuvre, and remain stable under conditions where lesser propulsion systems struggle or fail.

PC2 Class & Reliability

The vessel is built to Ice Class PC2, meaning a high degree of ice strengthening in hull, propulsion and structure. Steerprop’s units are part of its ARC/PULL ARC line of arctic azimuth propulsors which are designed for redundant safety, mechanical robustness, and efficient ice milling. They combine mechanical drive with modern automation for precise control. Over many years Steerprop has supplied azimuth propulsors for icebreakers around the world with solid performance in harsh environments and minimal downtime. For Polarstern, reliability is non-negotiable—it must operate 300-plus days per year in remote Arctic and Antarctic waters, leaving very little room for mechanical delays.

Underwater Radiated Noise Matters

Scientific research vessels must tread lightly. Underwater noise can disturb wildlife, interfere with acoustic sensors and research measurements, and have longer ecological effects. The SP 160 PULL ARC units were designed with this in mind. Steerprop has optimized gearboxes and integrated permanent magnet motor designs to reduce noise at its source. Reduced underwater radiated noise (URN) is now part of the requirement from the Alfred Wegener Institute. This dual pressure, high ice capability and low underwater impact—pushes the envelope in marine propulsion design.

Efficiency and Emissions

Beyond icebreaking and noise, environmental performance is a central pillar for the new Polarstern. The shipyard TKMS and AWI have selected the propulsion system to align with broader low-emissions goals. The propulsion architecture also includes dual-fuel capable engines, some able to run on green methanol as well as diesel and a battery storage system. The ship will have exhaust gas aftertreatment, strict emissions filtering, and design choices aiming to reduce fuel consumption and particulate emissions in sensitive polar regions. This is not simply replacing old hardware, it is rethinking what clean, efficient polar scientific operations can be.

Local Control and Smart Maintenance

Operating such powerful mechanical systems in remote polar environments demands intelligent maintenance and oversight. Steerprop will supply its Care condition-monitoring system which continuously tracks performance, detects anomalies, and enables predictive maintenance rather than reactive repairs. For a vessel that might spend most of the year at sea, possibly weeks away from major repair facilities, that matters deeply. The aim is to schedule part replacements or service only when really needed, thereby reducing downtime and lifecycle cost.

Beyond the Propulsors

Steerprop’s contract extends beyond those two massive azimuth units. They are responsible for the hydrodynamic design of the centre-shaft line propeller as well, this fixed-propeller unit provides forward thrust, especially in open water. Although another manufacturer will build that propeller, it will adhere to Steerprop’s exact specifications. This ensures the entire propulsion package, azimuth units, shaftline propeller, engines, exhaust treatment works as a coherent system. The result should be optimized propulsion efficiency, smoother handling in mixed ice and open water, and fewer mechanical compromises.

The Vessel: New Polarstern’s Mission & Service Life

The vessel is scheduled to enter service in 2030. It will replace the current Polarstern which has served as a scientific polar research platform for decades. The new vessel will be expected to operate up to 310 days of the year in both Arctic and Antarctic seas. It must endure extreme voyages, long deployments, and harsh weather, while supporting scientific research, resupply, possibly station maintenance, and icebreaking tasks. The propulsion demands are severe: ice-thick waters, varying snow cover, rough seas, cold temperatures. Every mechanical design decision must anticipate those stresses over a projected 30-year service life.

Challenges and Engineering Innovations Ahead

Sizing, strength, durability, and environmental control present real engineering challenges. Propellers must handle ice impact, abrasion, and be strong enough to maintain efficiency under snow cover and ice loading. Gearboxes must be shielded and cooled properly; motors must resist extreme cold without loss of performance. Materials must avoid brittleness. For automation, control systems must manage torque, thrust, steering for azimuth units, including station-keeping, tight steering in ice fields and combined operations with shaftline propulsion. All this while minimizing underwater noise, managing emissions and remaining maintainable in seaborne polar conditions.

Science, Climate, and Maritime Capability

The new Polarstern, with its record-size mechanical azimuth propulsors, represents more than just another icebreaker. It will serve as a floating laboratory in the front lines of climate research. As Arctic ice retreats, ecosystems shift, and seas warm, scientific measurement becomes urgent. Reliable, capable vessels equipped with sensitive equipment, low-noise propulsion, and extended endurance become essential. The capability also signals industrial leadership in propulsion engineering. Countries involved in polar research, marine ecology, long range oceanography and climate science will watch how this new vessel performs.

What to Expect by 2030

Between now and 2030 several key milestones must fall into place. Propulsors must be manufactured, tested in cold test facilities, integrated into hull designs. The exhaust and emissions systems must meet long lead time requirements. Sea trials in ice must confirm the performance metrics: ability to maintain speed in 1.8m ice, hold station, turn in ice fields, manage underwater noise. Operation of the predictive maintenance system must prove robust. Finally, the logistic supply of parts in polar regions and long term maintenance plans must be solidified.

A Propulsion Leap for Polar Science

Steerprop’s contract to deliver the world’s largest mechanical azimuth propulsors ushers in a new era for polar vessels. These SP 160 PULL ARC units promise raw power, harsh ice capability, environmental sensitivity and long-term reliability. For Polarstern, this is about more than breaking ice, it is about enabling researchers to reach, observe, protect and understand some of Earth’s most fragile frontiers with tools built for both strength and subtlety.

Azimuth propulsors, Polarstern propulsion, Icebreaker SP 160