Heavy RAS in development for MARS programme LOGISTICS VESSELS
R
OLLS-ROYCE is currently progressing the design and development of a new 6-
tonne capable Heavy Replenishment at Sea (HRAS) rig as part of the UK’s Military Afloat Reach and Sustainability (MARS) programme. It is envisaged that the HRAS system will be fitted to two new Fleet Solid Support (FSS) ships, one of three new classes of afloat support ship projected by the MARS project. The FSS ships’ primary role will be Carrier
Strike Support to Future Carrier (CVF) operations. HRAS is intended to enable the MARS FSS ships to provide stores at the necessary tempo to support CVF operations, and is therefore presented as analogous to their ‘main armament’. To mitigate development risk, the MARS Integrated Project Team formulated a ‘phased’ programme, intended to progressively mature and prove the HRAS concept through a progressive five-stage process of parallel concept development, detailed design, manufacture, and shore and sea trials. The outline HRAS requirement promulgated
to industry in 2004 called for a system able to transfer loads of up to 6tonnes; conduct RAS operations up to and including Sea State 7; achieve transfer rates of between 20-25 loads per hour; operate at vessel speeds of 10knots- 14knots and at separations of 30m-80m; and be capable of worldwide operation.
An Invitation to Tender for Phase 1 of the
HRAS design and development programme was issued to seven companies in July 2005, with four responding with offers. In November that year, Alstec, Rolls-Royce Marine, and Weir Strachan & Henshaw were down selected and split an aggregate £255,000 of costs to undertake parallel concept design activities, together with production of supporting documentation. This initial element was funded through the Ministry of Defence’s Marine Engineering Development Programme. The three companies submitted their
respective HRAS concept designs to the MARS Integrated Project Team (IPT) in July 2006. Following evaluation of the competing concept designs, Rolls-Royce was, in November 2006, down selected to undertake a detailed equipment design and costed trials programme under Phase 2 of the HRAS programme. The maturing MARS requirement, and greater understanding of the HRAS design drivers as a result of the phase 1 investigations, has resulted in some finessing of the system requirement. The required sea state limit has been reduced to Sea State 5, the required ship separation is now 37m-55m, and the maximum RAS speed has increased to 15knots. The HRAS concept advanced by Rolls-
Royce leverages on the company’s previous RAS rig experience, not least the principles
of all-electric system design and automatic transfer adopted for the abeam tensioned-wire RAS rigs, previously supplied to the auxiliary oiler replenishment ships RFA Fort Victoria and RFA Fort George. This offers benefits of lower through-life costs and reduced maintenance, equipment availability after long periods of inactivity, the elimination of system contamination risk, and zero damage to machines in the event of cable damage. In addition, electrical systems afford a
simple interface with indicators and control systems, a more flexible system design and architecture, and increased availability. They are also more environmentally friendly, offer lower noise and vibration, and longer machine life expectancy. Moving from a 2-tonne to a 6-tonne load
transfer capability requires higher jackstay tensions and therefore a larger diameter jackstay rope. There is also a requirement to maintain compatibility with legacy vessels [which demands a 2-tonne payload capability], and to be able to accommodate variable load dimensions. The requirement for the HRAS rig to transfer
both 2-tonne and 6-tonne loads has driven Rolls-Royce to propose a split mast solution. That enables the utilisation of a common drive arrangement, but to have the 2-tonne trolley and the 6-tonne trolley side-by-side. This dual
The HRAS solution proposed by Rolls-Royce capitalises on the company's long experience in the design, development, manufacture, and operation of abeam tensioned-wire RAS rigs for the RFA, including the 2tonne dual-purpose replenishment system fitted to the AORs Fort Victoria and RFA Fort George.
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WARSHIP TECHNOLOGY MAY 2007
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