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Better by design? Navies focus on adaptable vessel concepts
By Martin Driver
16 January 2008
There are many advanced new hullforms on trials around the world, but no formal navy programme better illustrates how diverse design approaches can achieve similar goals than the US Navy's (USN's) Littoral Combat Ship (LCS).
One of the winning LCS designs uses a traditional-looking yet innovative high-speed semi-planing monohull offered by a team led by Lockheed Martin; the other features a slender, stabilised trimaran created by a team led by General Dynamics.
Less well known than LCS - but technically more advanced - are a number of technology demonstrators based on yet more sophisticated hullforms, the key focus of which is on vessels that are capable of transforming themselves for different roles while in operation.
The first of these is the United States' Transformable Craft, or 'T-Craft' - also known as the 'Seabase Connector' - for which industry consortia led by Umoe Manídal of Norway and Alion Science and Technology of the US were downselected for Phase 2 of the project by the US Office of Naval Research (ONR) at the end of November 2007.
The ONR's T-Craft requirement envisages a "fuel-efficient vessel capable of self-deployment and high-speed transit." In keeping with USN and US Marine Corps seabasing strategy, it would be capable of servicing a large 'parent' ship stationed 100-200 miles (161 km) offshore, delivering troops, supplies and vehicles.
Fully amphibious, the T-Craft would be beachable. It would deploy in an unloaded state and be capable of travelling up to 2,500 n miles to a seabase, where it would demonstrate excellent seakeeping abilities.
The vessel would then serve as a high-speed connector, attaining a speed of 40 kt in Sea State 4 to convey troops as well as wheeled and tracked vehicles to beachheads. It would have a payload capacity of four to 10 M1A1 main battle tanks, or their equivalent, and be capable of carrying up to 750 tons.
The T-Craft is intended to have three modes of operation: a fuel-efficient or seakeeping mode for long-distance open-ocean transits; a high-speed or shallow-water mode for rapid seabased military vehicle transfer operations; and an amphibious mode for traversing sandbars and mudflats to achieve final delivery of the payload.
Since there are no existing high-speed vessels that can meet the T-Craft requirement - or even parts of it - designing and building a hullform to satisfy the ONR's brief will be no easy task.
Four Phase 1 contracts for the T-Craft programme were previously awarded to Alion, Umoe Mandal, and US-based Textron and Navatek. Under the first phase of the project, the four companies developed preliminary design concepts for inclusion in the T-Craft amphibious connector prototype.
In Phase 2, the contractors downselected by the ONR will develop detailed designs that can be model-tested against one another to validate performance.
The winner will progress to Phase 3 and build and test a T-Craft prototype.
Image: Alion’s T-Craft design, one of two selected to proceed to the next stage of the US Navy programme’s assessment phase. (Alion)