This paper provides the results of model tests in ice to evaluate the performance of the USCG Mackinaw Icebreaker that was equipped with two podded propulsors and compares with the data obtained from the full-scale ice trials. The objective of this collaborative model test program between the NRC and USCG was to understand the capability and limitation of the model tests with podded vessels in ice. As a result, the model tests showed a good agreement with attainable speeds at selected power levels but an overestimation of the ice resistance by an average of 7% (from 10% to 25%). Further discussion of podded icebreaker performance including turning circle tests in ice is provided and future work is proposed. This paper also provides a discussion of two different flexural strength test methods, which are simple beam and cantilever beam tests.
The number of icebreakers with podded propulsors has been increasing in recent years and many new icebreakers are planning to use the pods because of high maneuverability and additional benefits such as low noise and vibration, and various usages of the propeller wake. The first pod unit (1.3 MW) was installed in a utility vessel Seili in 1990. Since then, several ice-going tankers/ icebreakers have used single or multiple pod units, which had up to 16 MW power (Wilkman et al. 2018).