|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
The following HTML text is provided to enhance online readability. Many aspects of typography translate only awkwardly to HTML. Please use the page image as the authoritative form to ensure accuracy. TABLE 6.1 Current U.S. Coast Guard Polar Icebreakers tional by the conclusion of fiscal year 1990…. In preparing such plans, the Secretary shall consult with other interested federal agencies for the purpose of ensuring that all appropriate military, scientific, economic and environmental interests are taken into account. The design proceeded expeditiously, but delays occurred when a company with Arctic experience proposed to lease an icebreaker to the government. Consequently, OMB denied replacement icebreaker funding in the 1988 budget. An A-104 lease-buy analysis was completed in 1989 and showed that the net present value of a lease would be 10 to 15 percent more expensive than buying the ship. This finding cleared the way for Congress to appropriate funds to procure one ship. Funding was provided in the Defense budget thereby further slowing actual procurement. HEALY, delivered in 1999, was designed with modern science facilities to meet the increasing demand for Arctic research and has proven highly capable in that role. The characteristics of the current fleet are listed in Table 6.1. THE CURRENT WORLD FLEET OF POLAR ICEBREAKERSThe U.S. Coast Guard generally has used the thickness of ice broken continuously at 3 knots as a simple measure of icebreaking capability. Therefore, icebreaking ships for Coast Guard or military owners are not required to be built to meet classification society requirements. However, requirements for the structural integrity of ice-capable ships are specified in the rules of the various classification societies, for example, the Russian Maritime Register of Shipping, Lloyd’s Register, Det Norske Veritas, American Bureau of Shipping, and Germanischer Lloyd, and national regulatory authorities (Canadian, Finnish-Swedish, and Russian). These requirements are divided broadly into Baltic Rules for ice-strengthened vessels and Arctic Class Rules for icebreaking ships. Most classification societies have similar requirements for ice-strengthened vessels or ice type ships, which are divided into classes depending on their design ice thickness of up to 1.2 meters. Local structure design ice pressures depend principally on the ice class and hull area. In contrast, classification society requirements for icebreaking ships have historically varied somewhat in terms of definitions of hull areas, which are strengthened, and design load intensity relative to design ice and operating conditions. An approximate correspondence between different classification societies’ ice classes is shown in Table 6.2. How- TABLE 6.2 Approximate Equivalencies Between Classes
|
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
