UK: Astute-class submarine HMS Anson completes its first trim drive.

According to information published by BAE Systems on February 12, a major milestone has been achieved in the life of the fifth Barrow-built Astute-class submarine. Under the control of its Royal Navy crew, Anson completed its first trim dive in the town's Devonshire Dock.
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Royal Navy's Astute-class HMS Anson (Picture source: BAE Systems)

The operation saw Anson submerge completely beneath the surface of the water while crew tested onboard systems. This successful exercise proved the safety and stability of the 7,400-tonne, 97 meter-long attack submarine.

A 'trim dive' is done to complete a number of tests. The most important is to help engineers establish the vessel's center of gravity and precise weight.

More than 60 crew members were on board as part of the exercise, which saw tonnes of ballast taken aboard to assist in testing the vessel's stability.

The Astute class is the latest class of nuclear-powered fleet submarines (SSNs) in service with the Royal Navy. The boats are being constructed by BAE Systems Submarines at Barrow-in-Furness. The Astute class is the replacement for the Trafalgar-class fleet submarines in the Royal Navy service.

The Astute class is designed to achieve a top speed of 29–30 knots (54–56 km/h). The boats of the Astute class are powered by a Rolls-Royce PWR2 (Core H) (a pressurized water reactor) and fitted with a pump-jet propulsor.

For detecting enemy ships and submarines, the Astute class is equipped with the sophisticated Sonar 2076, an integrated passive/active search and attack sonar suite with bow, intercept, flank and towed arrays.