Figure 4.4-9 Average number of voyage-days for each of the three ships; full voyage, voyage in NSR and escorted voyage (average values from 1957 to 1990)
For the 50BC, the longest voyage was also in March, taking 42.7 days (27.3 days in the NSR); the shortest voyage was 28.8 days, again in September (16.1 days in the NSR). Although the 40BC takes slightly less time to navigate the NSR than the 50BC does, in total voyage-days the 50BC's voyage is about two days shorter. This is because the 50BC is about 2.5 knots faster than the 40BC in open water, suggesting the importance of open-water performance for overall profitability. The number of days of icebreaker escort depends on the severity of the ice conditions. The 25BC and 40BC possess roughly equal icebreaking capability. When the northerly and southerly routes are compared, the 25BC requires more days of icebreaker escort in the southerly route than does the 40BC from December to May, whereas the 40BC requires more icebreaker escort than the 25BC does from June to November. The selection of route is highly dependent on the season. In the winter, the landfast ice extending along the coast makes ice conditions severe for navigation; at this time of year, operations are more convenient along the northerly route, since ships navigate in the marginal waters of landfast ice, abundant in polynyas. In the summer, open water can be found along the coast, making the coastal route more advantageous. Changes in average sea speeds in the major NSR waters by month are shown for the 50BC in Figure 4.4-9. During the winter months from December to May, sea speed in all regions is in the range of 4-7 knots, with sea speeds ranging somewhat higher in the Laptev Sea. In the winter, as the number of days on which icebreaker escort is required increases, the speed of the icebreaker becomes the dominant factor. Ice conditions are easiest in the summer months from August to October, enabling the 50BC to achieve speeds of 9-14 knots. In the East Siberian Sea, sea speeds are found to be slower in the most cases than in other regions. As shown in Appendix 5-2, the results for the 25BC and 40BC are not dramatically different than those for the 50BC. The dependences on operation month and type of ship were examined by the freight rates defined by the ratio of the operational costs for each voyage to transported cargo tonnage (Table 4.4-8). Capital cost accounted for the largest proportion of operational cost (see Appendix 5-2). The lowest operational cost per voyage was that of the 50BC, at around $890,000-1,080,000, while the most expensive was the 40BC's, at $1,190,000-1,600,000. In these cost calculations, voyage-days, sea speed, operational cost, etc. were averages for 30 years or so, based on the sea ice data from 1957 to 1990. The number of voyage-days per voyage includes three days for loading and three days for unloading at each end. For details of the cost calculations, please see Appendix 5-2.
