The submarine HMS Agamemnon, the sixth member of the Astute-class, has taken another step toward its formal incorporation into the Royal Navy fleet after successfully completing its first dive. The maneuver took place only days after its official commissioning ceremony, attended by His Majesty King Charles, and was carried out over two days at BAE Systems’ facilities in Barrow-in-Furness, under the supervision of the Royal Navy crew.
The so-called trim dive marks a key phase in the testing and certification process before the submarine begins sea trials and enters operational service. This procedure involves two main activities: the basin dive and the trim and inclination experiment. During the basin dive, various onboard systems are tested, including the ballast tanks that allow the submarine to surface. In the second phase, naval engineers determine the vessel’s center of gravity, both on the surface and while submerged, by shifting 16 tons of lead weights and using pendulums suspended between decks — a method that has been used since the 18th century.
The tests were conducted by BAE Systems and the ship’s crew, under the supervision of naval architects and representatives from the Submarine Delivery Agency (SDA) and the UK Ministry of Defence. The results will confirm the HMS Agamemnon’s performance prior to its final integration alongside the existing HMS Astute, HMS Ambush, HMS Artful, HMS Audacious, and HMS Anson.
HMS Agamemnon was officially named in April 2024 and launched in October of the same year. Measuring 97 meters in length and displacing 7,400 tons, it belongs to the Royal Navy’s latest class of nuclear-powered attack submarines. These vessels are designed to protect the UK’s nuclear deterrent against hostile actions, support global operations, and contribute to intelligence and strategic reconnaissance missions.
The inclusion of HMS Agamemnon comes less than a year after its launch and marks a significant milestone in the renewal of the Royal Navy’s submarine force. In recent months, the Royal Navy decommissioned HMS Triumph, the last of the Trafalgar-class submarines, thus completing the transition to the Astute class.
This modernization takes place amid limited operational availability. In July, HMS Anson returned to Clyde Naval Base in Scotland, leaving the aircraft carrier HMS Prince of Wales without submarine escort during its participation in Operation Highmast in the Pacific Ocean. Meanwhile, HMS Ambush and HMS Artful have remained inactive for several years due to maintenance and upgrade work.
Meanwhile, BAE Systems continues construction of the seventh and final submarine in the program, HMS Agincourt (S125), whose launch date has not yet been officially confirmed. Its entry into service is expected between 2028 and 2029, completing the Royal Navy’s Astute-class submarine program.
*Images courtesy of the UK Ministry of Defence.
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