As part of an update to Parliament on the progress of the Trident replacement program, Britain’s Ministry of Defence (MoD) has released a concept image of the Royal Navy’s next ballistic nuclear missile submarine. This coincides with the awarding of two contracts to BAE Systems Maritime-Submarines for £47 million (US$76 million) and £32 million (US$60 million) to begin preliminary design work on the nuclear-powered submarines, currently called the Successor class, which are intended to replace the Navy’s aging fleet of of Vanguard-class boats by 2028.

The Royal Navy’s four Vanguard-class Trident ballistic missile-armed submarines have been in service since 1993 as the key component of Britain’s Independent Nuclear Deterrent (IND) policy, with the Navy's 16 Lockheed Trident D5 submarine-launched ballistic missiles (SLBMs) carrying up to 192 nuclear warheads in MIRV re-entry vehicles. Conceived during the Cold War as a replacement for the Resolution-class Polaris submarines, the Vanguard-class is now itself in need of replacement as the first of the class, HMS Vanguard, is due for a major refit in 2017.

Since 2011, the MoD has been carrying out a directive by Parliament to come up with a replacement for the current Trident submarines. According to the update, which included the released image, the MoD, along with BAE Systems, Rolls-Royce and Babcock International, have concluded that the alternatives of a land- or sea-based deterrent, or a more exotic one, such as nuclear-armed cruise missiles on attack submarines, would not be as efficient or cost effective as a like-for-like replacement of the current Trident system.

HMS Vanguard (Image: Ministry of Defence)

The concept image showing a distinctly streamlined hull is only an approximation of the final design, which has yet to be determined as the British government sorts out defense policy, budget priorities, and the future nature of the IND. According to the MoD, the £11-14 billion (US$18-23 billion) (at 2006 prices) boats are expected to be larger, stealthier, more complex, and safer than the Vanguard and will serve from 2028 until the mid 2060s. However, exactly how many of them will be built, and what their deployment will be is uncertain until Parliament makes its final decisions in 2015.

The Successor submarine will be powered by a Rolls-Royce PWR3 nuclear reactor that will not require refueling for the entire life of the boat. The design and construction methods will be based on those of the Astute-class attack submarines currently being built. The MoD says that the lessons learned from Astute will allow Successor to be built in less time than the smaller submarine.

Inside the new Successor will be 12 missile tubes instead of the current 16. Like the current boats, Successor will carry Trident D5 missiles. Since the US Navy is working on a replacement for its own Ohio-class missile submarines, the US and the UK are jointly developing the Common Missile Compartment for both designs. Under this agreement, the Electric Boat division of General Dynamics will supply the missile tubes, while Britain will build and install its own compartments.

Though the Trident missiles will be bought from the US, the nuclear warheads and re-entry vehicles will continue to be British-built. Since the current stock of UK warheads is not slated for replacement until the 2030s, they don’t factor into the current Successor design.

According to First Sea Lord Admiral Sir George Zambellas, "The Royal Navy has been operating continuous at-sea deterrent patrols for more than 40 years and the Successor submarines will allow us to do so with cutting-edge equipment well into the future."

The MoD states that, though Parliament has yet to make its final decisions on the Successor, BAE Systems was awarded contracts this week because the long lead time in developing the new submarines means that preliminary work must begin even before the design is settled upon. Work on details like structural fittings, electrical equipment, castings and forgings must be ordered now or there is an increasing risk of delays and consequent cost overruns.

In a statement, Defence Secretary Philip Hammond says, "This £79 million (US$129 million) investment is another important milestone in our preparations to build these world-leading submarines. The current Vanguard Class of deterrent submarines perform a vital role in the defence of the UK and the replacement for this capability is of national importance.

"The Successor programme is supporting around 2,000 jobs, and up to 850 British businesses could benefit from the supply chain as we exploit the most modern technologies and employ a significant portion of the UK’s engineers, project managers and technicians over the coming years."

Sources: Gov.UK (1), (2 (PDF))