ADVANCED HULLFORMS
Further applications for Navatek fast ship technology
T
he T-Craft is the second mission-specific, military application of Navatek’s dual-use
(military-commercial) technology to emerge this year from its advanced ship research and development programme. Earlier this year, Navatek Ltd and Maryland-
based defence contractor General Dynamics Robotics Systems (GDRS) won a US$8.5 million contract to build two advanced prototypes of an Unmanned Surface Vehicle (USV) destined to be integrated into the US Navy’s Littoral Combat Ship (LCS). The total value of that contract, if all options are exercised, is US$11.3 million. ‘We’re recognised as a world leader in
the design of advanced ships,’ claimed the company. ‘In addition to federal research funding we receive, we have invested over US$13 million of our own money in these projects over the last five years.’ Navatek advanced ship prototypes
stretch back to 1989 when Navatek I, the first commercial, Coast-Guard certified Small Waterplane Area Twin Hull (SWATH) ship in the US entered service. Subsequently, Navatek teamed with Lockheed Martin to build and test their fast SLICE (1996), and worked with the Office of Naval Research to develop the 160ft Navatek-patented lifting body ship, Sea Flyer, and another lifting body ship called the HDV- 100. Navatek scientists have also invented a
patent-pending, wave energy conversion device that harnesses the power of ocean waves to generate electricity. The US$400,000 effort, funded by Navatek, has produced a scale-model demonstrator which began ocean- testing in April.
The T-Craft needs to combine the attributes of an air cushion lading craft with those of an SES or SWATH.
• Self deploying over a long distance in high sea state unloaded.
• Significantly higher payloads (four to 10 times).
• Fully loaded unrefuelled range >500nm at 40knots.
• The ability to traverse sand bars and mud flats.
• Fully amphibious landing capability. Technical barriers include:
• Transition of propulsion systems from in water to out-of-water mode.
• Variable/retractable skirt geometry. • High strength, lightweight, long-wear materials.
• Use of active ride control systems. • Human system integration. • Vehicle transfer at the seabase.
Other obvious challenges include weight
control, system/subsystem reliability, the variable/retractable skirt geometry, and the need to use high strength, lightweight, high
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load-bearing, fatigue-, and wear-resistant innovative marine composites. Another is the development of mechanisms to transition from Surface Effect Ship (SES) to Air Cushion Vehicle (ACV) deployment whilst maintaining cushion sealing efficiency. Other systems that will need to be developed
and successfully integrated within the T-Craft platform include novel rapid, automated roll- on roll-off (ro-ro) connector systems which are high sea-state tolerant, plus the ability to carry out safe close-proximity transfer in high sea states. To work with the seabase and T-Craft a
Seabasing Stable Transfer Platform is being developed, this being a rapidly self deployable ship-to-ship transfer platform that would utilise an articulating spar connected to an interchangeable multi-mission catamaran. While transiting, the spar is operated in the
horizontal position and the vessel behaves as a fuel efficient trimaran. At the sea base, the spar is ballasted to the vertical position taking advantage of the low water-plane area to provide a highly stable platform for transfer operations
between a variety of platforms through Sea State 5. The multi-mission catamaran is detachable for shallow water operations independent of the spar, and the spar also provides a near shore breakwater as well as a rapidly deployable to-to discharge facility. The problem to be overcome with the
Seabasing Stable Transfer Platform is, of course, that transfer of cargo and materials cannot normally be accomplished in conditions above Sea State 2 or in swells which cause load pendulation (the variety of vessels at the sea base will result in out-of-phase motions requiring a stable ship-to-ship transfer platform).
Low-Draft, Stabilised High-Speed Surface Connector Working in support of SAIC under contract to the ONR, CDI Government Systems in the US has been assisting with the development of advanced computational methods for the design of unconventional hullforms under the ONR High-Speed Sea Lift (HSSL) programme. As the company explained recently, the emphasis has been on improving the prediction
WARSHIP TECHNOLOGY MAY 2007
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