With the centre barge lowered a vehicle is loaded onto Susitna.


and in both brash ice of 0.6m and ‘Punky’ pan ice (the hull will be strengthened to Ice Class FMA 1B). It will also have to cope with wind speed gusts of up to 70kts, and 43kts sustained, also Sea States of up to SS 4 (Beaufort) (SS-5 Pierson-Moskowitz sea spectrum). In the area in which it will operate, tidal currents of up to 8kts can be expected (nominal 4.75kts reversing) and the tidal reach is 1.8m to more than 10.6m (6ft to more than 35ft), with suspended sediment of 1.5-2g/litres of glacial silt in summertime water. The performance and capabilities of


the ferry will be closely monitored by the ONR in order to assess its military potential, in particular, whether a military version of the craſt could transform itself between two distinct modes: a deep-water SWATH transporter and a shallow draught landing craſt. Te ONR’s primary objective with the


E-Craſt is to demonstrate that a vessel that can operate as a multipurpose, expeditionary cargo and troop ship, operating efficiently at high speed, in ice and in shallow water, as well as having the capability to beach itself to load/discharge vehicles up to the size of a main battle tank. Susitna differs from a conventional


SWATH hullform in as much as it has a centre section or barge that can be hydraulically raised and lowered (as shown


Warship Technology March 2011 Closing the bow ramp. 17


in the images reproduced here). The buoyancy of the SWATH hulls can also be adjusted whilst the vessel is under way. Two modes of operation envisaged are thus envisaged for Susitna: SWATH mode – for stability in high sea states, when the weather is poor; and monohull mode for operation in shallow waters. Te US Navy is particularly interested


in Susitna because the seabasing concept requires ‘connectors’ – fast craſt capable of transporting men and heavy equipment ashore – and it sees the E-Craſt as a concept capable of fulfilling such a mission. Seabasing connectors must have high


speed, high capacity and be able to operate in almost all sea states, and in shallow water. Tese are somewhat contradictory requirements for a conventional vessel, hence the interest in a design that can transform itself into different modes of operation. Lockheed Martin, which sub-contracted the ferry to Guido Perla &


design of


Associates in Seattle, noted that, in commer- cial service, Susitna will accommodate around 20 vehicles and 100 passengers. Te hull concept for Susitna was originally developed by Lockheed Martin, and Lew Madden who developed the vessel concept while working for the company. WT


Feature 2


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