Feature 2 | ADVANCED HULLFORMS Transformable E-Craft enters service
Late 2010 saw a highly innovative vessel, Susitna, enter service in the USA. Built by Alaska Ship & Drydock, the vessel is a demonstrator funded by the Office of Naval Research (ONR) to prove the concept of a variable draſt, beachable, landing craſt that is also capable of carrying a large payload in variable sea states.
Susitna will
operate partly as a monohull and partly in SWATH mode.
T
he twin hull vessel, which can also operate in light ice conditions, is now in operation as a ferry on
the challenging passage across Knik Arm between the Mat/Su Borough region and Anchorage, Alaska. Te vessel is capable of operating both as a Small Waterplane Area Twin Hull (SWATH) and as a monohull. Such is the potential of this genuinely
unique design that it has also attracted the attention of the US Navy, which is interested in it because it offers the potential to meet evolving requirements for ‘transformable’ naval vessels that can carry men and equipment across long distances, at speed, but also come in close to shore and disembark men and equipment. The Knik Arm in Alaska – as the
waterway that forms part of Cook Inlet, north of Anchorage, Alaska, where Susitna will operate – is known for its particularly challenging conditions. The tide in the
16 Warship Technology March 2011
Knik Arm is the second most extreme in North America, and the temperature in the area ranges from well below freezing to extreme summer temperatures. In winter, brash ice and 0.6m (2ſt) thick ‘pan ice’ is pushed by winds with gusts up to 70kts. Te
The ‘transformable’ ferry is designed to be able to beach itself.
waves in the Knik Arm average 3.5-5ſt, and tidal currents run at up to 8kts with nominal currents at 4.75kts, reversing twice daily. Tis being the case, the innovative new
design needed to be able to operate in air temperatures ranging from -50°F to +100°F
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