Implications of ice class for an offshore patrol vessel

Abstract

The importance of the Polar Regions, both in the Arctic and Antarctic, is likely to increase as environmental and geopolitical developments (e.g. as a result of global warming and increasing shortages in fossil fuels) increases international interest in these areas. With this in mind many nations, are increasingly considering the operation of naval vessels in these areas. This paper identifies the aspects of vessel design that must be addressed to enable an offshore patrol vessel (OPV) OPV sized vessel to operate in ice conditions and estimates the cost of adding this capability. A baseline 90 m OPV design was developed that had no requirement for ice operation and a unit platform cost (UPC) calculated for the vessel using a simple, weight based, cost model. The changes that would need to be made to this vessel in order to achieve increasing levels of ice capability were then identified and the ship was redesigned to accommodate these changes. The resulting UPC cost estimates for the ships give an indication of the whole ship cost implications of adding a requirement to operate in ice for a vessel of this size. Two variants were developed, the first to ice class 1C (Lloyds Naval Ship Rules) and the second to Ice Class 1AS. These represent light ice conditions (with icebreaker assistance where necessary) and difficult ice conditions, first year ice up to 1.0m, (without the assistance of icebreakers) respectively. The structural and ship system requirements of Lloyds Naval Ship Rules together with the relevant recommendations on winterisation were incorporated in both designs.