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January 20, 2023

UK Defense Ministry Buys Offshore Construction Vessel for Subsea Cable, Pipelines Protection

Credit: Jan Verhoog/

Credit: Jan Verhoog/

The UK defense ministry has acquired a subsea construction vessel that used to work in the offshore energy industry. The vessel, Topaz Tangaroa, will undergo a period of military modification and will be used to protect subsea cables and oil and gas pipelines.

The Topaz Tangaora, to be renamed as it joins the Royal Fleet Auxiliary fleet, is the first of two future undersea surveillance ships, and it arrived at Cammell Laird, Birkenhead. Thursday.

Once operational, the ship will be used to protect seabed telecommunications cables and oil and gas pipelines. 

"The 98-meter-long, adaptable offshore patrol vessel – the length of Big Ben – will act as a ‘mother ship’, operating remote and autonomous offboard systems for underwater surveillance and seabed warfare, vital to our national security," the UK defense ministry said.

"Shortly after arriving at Cammell Laird, the ship will be repainted and have critical military equipment installed, before taking up its role as the first of two Multi-Role Ocean Surveillance (MROS) ships, operated by the Royal Fleet Auxiliary (RFA) later this year," the ministry said.

The vessel will be formally handed over to control of the RFA in the next few days, several months ahead of schedule – following an acceleration of the acquisition announced by the Defence Secretary in November 2022.

Defence Secretary, Ben Wallace, said: "The first of two dedicated subsea surveillance ships will join the fleet this summer, bolstering our capabilities and security against threats posed now and into the future. It is paramount, at a time when we face Putin’s illegal invasion of Ukraine, that we prioritize capabilities that will protect our critical national infrastructure.

The Topaz Tangaroa was selected to meet the requirements of the Royal Navy, having been built four years ago to support a mix of underwater operations, including work on oil rigs, construction, maintenance, and inspection work, as well as autonomous submarine operations.

The 6,000-tonne vessel is equipped with a helipad, crane, and expansive working deck and features a ‘moon pool’ – a large access point in the underside of the hull through which submersible capabilities can be launched.

Head of the Royal Fleet Auxiliary, Commodore David Eagles RFA, said: This is an entirely new mission for the Royal Fleet Auxiliary – and one we relish. We have been entrusted with supporting a key operation to safeguard the UK’s infrastructure, security and prosperity and that fills all of us in the RFA with pride. These are really exciting times.

The vessel, will be crewed by around two-dozen RFA sailors, while around 60 Royal Navy specialists will operate the undersea surveillance systems and other survey and warfare systems when embarked. 

The vessel is due to enter operational service in Summer this year, with the programme for the acquisition of a second ship currently in concept phase, the ministry said.

Subsea vehicles are the workhorses of subsea exploration, and in this edition MTR explores the technologies and technique that are helping to deliver increased presence and improved quality and speed of data delivery from the world’s waterways.
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