Northern Sea Route Reconnaissance Study. A Summary of Icebreaking Technology

Abstract : Since the advent of steam power, icebreakers have been built to navigate in ice-covered waters. The hull forms of early icebreakers were merely an adaptation of open water hull shapes, by sloping bow angles more to create vertical forces for breaking ice in bending. However, these bow forms were found to be unsuitable for sea-going vessels because they push broken ice ahead of them. This experience led to construction of all sea-going vessels with wedge-shaped bows from 1901 to 1 979. With the introduction of low-friction coatings and the water-deluge system, it is now possible to operate ships with blunt bows efficiently in broken ice. New developments in marine propulsion technology have also been incorporated to obtain better icebreaking efficiency and performance. Both fixed-pitch and controllable-pitch propellers are in use. Nozzles surrounding the propellers are also used to increase the thrust and to reduce ice-propeller interaction. Electrical and mechanical transmission systems have been used in icebreakers to improve the characteristics of the propulsion system. Though many types of prime movers are used in icebreakers, medium-speed diesel engines are the most popular because of their overall economy and reliability. Appendix A is a description of the Russian icebreaker Yamal, which is one of the largest and most powerful icebreakers of the world today. Appendix B contains an inventory of existing ships that are capable of navigating in at least O.3-m-thick ice. Some of the present icebreakers are capable of navigating almost anywhere in the ice-covered waters of the Arctic and the Antarctic, and multi-purpose icebreakers have been built to operate not only in ice during the winter but also in open water doing other tasks during the summer.