An icebreaker propulsion system has to be versatile in order to perform at optimum efficiency in all operating conditions. It must be economical when steaming in open water, and yet deliver large thrusts in the bollard condition. It must also withstand the loads imposed by the fee, which can be in the form of a steady load during tee milling, or a transient load due to tee impact. All these factors combine in a complicated manner, and physical model experiments are currently the best method available for studying the problem. An experiment program to predict the propulsive performance of an icebreaker must therefore address both the open water and icebreaking aspects, in an accurate and efficient manner.

This paper discusses some techniques developed to predict the propulsive performance of large ice­breakers, using models in a refrigerated tee basin and a towing tank. It is based on some experiments recently carried out at the Institute for Marine Dynamics (IMO). in St. John's, Newfoundland and the results are used for illustration purposes throughout this paper.

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