As is known, the Vanguard-class is a British class of nuclear-powered ballistic missile submarines (SSBN) in service with the Royal Navy. Commissioned into service between 1993 and 1999, HMS Vanguard, Victorious, Vigilant, and Vengeance were originally designed for a 25-year lifespan. However, this has been extended by up to 13 years, postponing the requirement for a new class of SSBN and bringing the procurement timeframe into line with the Ohio-class replacement program (U.S. Navy).

According to Jon Rosamond, USNI News, the concept work on Britain’s so-called Successor SSBN began in 2007, with the Ministry of Defense appointing an industry team consisting of shipbuilder and design lead BAE Systems plus Babcock (providing the torpedo handling/launch system, signal ejector system, and through-life support expertise) and Rolls-Royce (responsible for the nuclear steam-raising plant). The MOD approved the so-called «Initial Gate» business case for the new submarines in 2011, releasing funds for a five-year assessment phase intended to bring the design to 70 percent maturity.

In 2013, BAE Systems has been awarded contracts totaling £79 million by the UK Ministry of Defence to begin procuring its first long lead items for the Vanguard Successor programme, which will carry the nation’s nuclear deterrent capability from 2028. The MOD released a concept image depicting an aggressively raked sail, X-shaped stern, and bowplanes located below the waterline when the boat is surfaced. Displacing about 17,000 tons, Successor will be slightly larger than the UK’s current SSBNs (15,900 tons).

Propulsion system components, high-grade steel for the pressure hull and other critical long-lead items for the first ship have now been ordered and some manufacturing activities have started. Tony Johns, Managing Director of BAE Systems Maritime – Submarines, said: «Following the Government’s announcement in May 2011 that the programme had passed its «Initial Gate», it is now well into its third year of a five-year design and development phase, during which the submarine’s concept design and operational requirements are being matured into a detailed design. The «Main Gate» procurement decision – giving permission to proceed for full production – is due in 2016».

By aligning the procurement of the Vanguard and Ohio replacements, the U.K. opened up opportunities for collaborative work with the United States in several areas, notably the design of the Common Missile Compartment (CMC) and the nuclear powerplant, and the integration of sonar arrays and associated combat systems.

Although Successor will be fitted with three quad-pack CMC modules, providing 12 launch tubes for Trident D5 ballistic missiles (down from Vanguard‘s 16 tubes), the British government has decided that just 8 operational missiles will be routinely carried on patrol. Meanwhile, General Dynamics Electric Boat will supply outfitted tubes – 87 inches (2.21 m) in diameter and 45 feet (13.72 m) high – for CMC assembly in the U.K.

In October 2014, the U.S. Navy awarded Electric Boat $84 million to start CMC missile tube manufacturing: 12 for the Successor lead ship, 4 for the Ohio replacement program and 1 for the Strategic Weapons System-Ashore test facility at Cape Canaveral. Meanwhile Rolls-Royce is developing the RN’s third-generation pressurized water reactor (PWR3) with technological support from the United States, under the terms of a 1958 intergovernmental agreement to share atomic energy technology for defense purposes. The PWR3 design has benefitted in particular from lessons learned with the S9G reactor that powers the Virginia-class submarines.

Compared with the Vanguards’ PWR2 system (27,500 shp, 20.5 MW), the PWR3 has a simpler circulation design and should be easier to operate. According to Rolls-Royce representatives, it promises a «huge improvement in terms of safety, integrity and availability, while at the same time reducing the through-life costs».

Meanwhile, the U.K. is also participating in the U.S.-led Trident missile life-extension program, which will keep the D5 ballistic vehicle – capable of delivering up to 12 independently targetable nuclear warheads – in service into the 2040s.

One major decision remains outstanding: Whether to replace the Vanguards on a one-for-one basis, at an estimated cost of $17.28-$22 billion (at 2006/07 prices), or attempt to benefit from improved reliability and maintainability by ordering just three SSBN submarines. However, the cost savings inherent in a three-boat solution would be too small compared with total program expenditure, and the RN believes that 4 SSBNs is the minimum required to maintain a credible and continuous at-sea deterrent.

«We have a proud history of collaboration with the United States on submarine programs and I’m pleased to say that continues today», Will Blamey, the Successor program director at BAE Systems Submarines said. «We’re more than halfway through the five-year assessment phase and are making good progress with the submarine design. We’re fully focused on achieving our program objectives and remain confident the first submarine will be in service by 2028».