The most technologically advanced submarine built for the Royal Navy, which has a sonar capable of tracking ship movements across thousands of miles, is in the repair shop after its most basic part failed at the first test.

One of the million components that make up HMS Astute, the first of a new generation of nuclear-powered hunter-killer submarines, stopped working and caused serious damage.

The submarine, which has been built by BAE Systems at its shipyard in Barrow-in-Furness, Cumbria, and has cost more than £1 billion, was launched in June and is due to come into service in 2009. It is already more than three years late because of technical and project-management difficulties.

Now the builders are working all hours to ensure that there are no further delays, after the turbogenerators were damaged when, during a test of the systems, the oil stopped circulating. For a whole minute the mighty turbogenerators ran metal on metal after a lubrication pump failed. Scoring marks are having to be removed in a delicate engineering procedure.

The new submarine has been fitted with a nuclear reactor whose fuel will last throughout the boat’s service with the Navy. A digital optical mast on board replaces the traditional periscope. But the simple failure of the oil pump is a serious embarrassment.

“We don’t yet know whether there is going to be a delay in the programme, but they are working hard to make sure there isn’t,” the Navy said.

Navy officials said they assumed that the submarine builders were culpable and would have to meet the costs of the damage.

BAE Systems said that the repair work should be completed by the end of the year. A spokesman said: “The incident was the result of a lubrication pump failing to operate during testing of the system. Once this failure had been identified, the test was immediately halted, but by that time both turbogenerators had sustained damage because oil had ceased to circulate.” The spokesman added: “There was no nuclear material on the submarine at the time of the incident and the reactor was not affected.”

The turbogenerators provide electrical power for systems on the submarine and are located in the engine room in the aft section of the boat.

The repair work to remove the scoring marks on the generator shafts is being carried out inside the hull at BAE’s Devonshire Dock Hall complex in Barrow-in-Furness.

BAE said that measures had been taken to ensure that a similar incident did not happen again.

The company said that the intention remained to deliver the first of the new class of submarine to the Ministry of Defence by the autumn of next year, with the in-service date some time in 2009.

The first of the 7,400-tonne submarines, which will replace the Swiftsure Class and Trafalgar Class boats, has cost £1.2 billion. The MoD has ordered four of the submarines, and the Navy is hoping that there will soon be a contract for a further two or three. The other three now being built are HMS Ambush, HMS Artful and HMS Audacious. The MoD’s current plans are to have a hunter-killer fleet of seven submarines after 2022.

All aboard

£42bn The estimated “whole-life” cost of seven of the submarines

£9bn The cost of the concept, design and manufacture

£32bn The in-service costs, including crew pay and maintenance

£1bn The estimated cost of the disposal of the fleet

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