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NSWC PCD Supports Future Fleet, ONR's T-Craft

Navy News Service

Story Number: NNS120907-10

By Jacqui Barker, Public Affairs, Naval Surface Warfare Center Panama City Division

PANAMA CITY, Fla. (NNS) -- Naval Surface Warfare Center Panama City Division (NSWC PCD) engineers are supporting two specific technology transitions related to the Office of Naval Research (ONR)'s Transformable Craft 'T-Craft.'

The two technologies, finger skirt design improvements and a composite/aluminum hybrid lift-fan design are being realized as feasible for use on U.S. and allied Navy air cushion vehicles (ACV).

U.S. Navy ACV platforms such as the current landing craft air cushion (LCAC) and future ship to shore connector (SSC) serve many purposes, including the transport of equipment and personnel between locations at sea and ashore during humanitarian assistance/disaster recovery (HA/DR) and major combat operations (MCO).

"NSWC PCD has supported ONR in its oversight of the T-Craft designs since we were invited to participate during phase one of the program back in 2007," said Bob Teer, air cushion vehicle branch head. "We were brought in to participate in the assessment of the three T-Craft designs developed during this phase. In this capacity we served as SMEs to ONR in their assessment of which designs should continue in phase two.Phase two consisted of contract designs for the T-Craft."

Specifically, NSWC PCD Expeditionary and Maritime Systems Department (Code E) engineers have provided ONR with ACV Subject Matter Expertise (SME) and program management support for the T-Craft program since 2007. This effort has led to improved lift-fan and bow seal finger design features that could be included in future ACV designs.

The T-Craft designs compliment the U.S. Naval Sea-Basing strategy as a leap-ahead technology, and have capitalized on NSWC PCD's ACV design experience. NSWC PCD, a component of the Naval Sea System Command (NAVSEA), is the platform in-service engineering agent (ISEA) for the LCAC fleet, according to Teer.

Initial design proposals sought a prototype connector capable of being fuel-efficient and self deployed during open ocean transits. The connector also needs to be capable of high speed shallow-water transits while fully loaded with at least four M-1 tanks; include personnel berthing; execute good sea-keeping during cargo transfers at sea, and have amphibious operations capability.

NSWC PCD T-Craft Team Lead Rob Cole stated that a number of technology transitioning opportunities were realized at the conclusion of the contract designs. Two of which found suitable for further development prior to transition to programs of record were the lift-fan design for cushion inflation, and the finger skirting that supports the bow during on-cushion operations. NSWC PCD was tasked to support ONR in the further refinement and development of these technologies.

The lift fan is being designed and constructed by Umoe Mandal in Mandal, Norway. The fan will be the largest composite lift fan ever constructed, and is based on the prior success of an earlier (and smaller) version built by Umoe for the U.S. Navy's LCAC. This earlier design was tested by NSWC PCD in 2009 and 2010 in Panama City, Fla. This new hybrid design uses composites as well as aluminum, and is based partially on the specifications of the SSC lift fan. It will include improved features for maintainability with life cycle costs projected to be less than current aluminum designs.

"Our engineering efforts were also in design of the bow seal fingers used for model testing, as the T-Craft fingers are larger than any other created before. They were designed to seal the supporting air cushion and be flexible to minimize drag. Surface Effect Ships, such as T-Craft, are sensitive to drag, which drives the thrust and power requirement needed to operate at high speed."

Researchers at the University of Michigan and the University of New South Wales conducted bow seal experiments with the model fingers, and collaborated with NSWC PCD and ONR on how to better understand bow seal resistance in order to improve bow seal designs. The experiments, conducted at the U.S. Navy's Large Cavitation Channel located in Memphis, Tenn. in the spring of 2011, tested seals and materials in a controlled environment. Cole said the test demonstrated the finger behavior at various speeds and provided insight as to how the behavior affects drag.

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