The U.S. Navy supported the Oct. 23 launch of a U.K. Royal Navy Trident II D5 Fleet Ballistic Missile (FBM) built by Lockheed Martin. The unarmed missile was launched from the submerged Royal Navy submarine HMS Vigilant in the Atlantic Ocean.

The test marked the 143rd successful test flight of the Trident II D5 missile since design completion in 1989 – a reliability record unmatched by any other large ballistic missile or space launch vehicle.

“The Royal Navy and the U.S. Navy continue to demonstrate the readiness and reliability of this highly capable system,whose mission is to discourage aggression,” said Melanie A. Sloane, vice president of Fleet Ballistic Missile programs, Lockheed Martin Space Systems Company, the Trident missile prime contractor. “The cooperation of both governments, supported by industry, provides a credible submarine-based strategic deterrent.”

The test, which was part of a Demonstration and Shakedown Operation that verified the integrity of the strategic weapon system following an overhaul of the submarine, was the 10th consecutive successful Trident II D5 missile test flight by the U.K. since 1994. The missile was converted into a test configuration using a test missile kit produced by Lockheed Martin that contains range safety devices, tracking systems and flight telemetry instrumentation.

First deployed in 1990, the D5 missile is currently aboard U.S. Navy OHIO-class and Royal Navy VANGUARD-class submarines. The three-stage, solid-propellant, inertial-guided ballistic missile can travel a nominal range of 4,000 nautical miles and carries multiple independently targeted reentry vehicles.

The UK Ministry of announced that  it has awarded BAE Systems a further £315M for ongoing design work for the replacement to the Royal Navy’s Vanguard class submarines.

The announcement followed the one made in May this year, when it revealed it had placed an initial £328M design phase contract with BAE Systems Maritime – Submarines.

The Vanguard class, which carries the UK’s nuclear deterrent, will be replaced from 2028. BAE Systems already has more than 1,000 employees working on the replacement programme, the majority of which are focused on developing the new submarine’s complex design.

BAE Systems Maritime – Submarines Managing Director John Hudson said: “The design of a nuclear-powered submarine is one of the most complex and technically demanding engineering programmes undertaken by the maritime industry. This further work underlines the MoD’s confidence in our ability to deliver a design that will meet the future needs of the nation’s nuclear deterrent.