A detailed model has provided what’s likely our best idea of how the U.K. Royal Navy’s new Dreadnought class nuclear ballistic submarine, or SSBN will appear. The four Dreadnought boats represent one of the most important U.K. defense programs in many years and it’s notable to see how many advanced features the design includes, as the Royal Navy seeks to find the optimum balance between speed, stealth, and incredibly destructive firepower. The four new SSBNs (known as ‘bombers’ in British parlance) will replace the Vanguard class that entered service in the 1990s.
The impressive model of how the new Dreadnought is expected to look was presented recently at the U.K. House of Commons, as part of Rolls-Royce’s nuclear portfolio demonstration during the government’s “Nuclear Week in Parliament.” A photo of the model from that event was subsequently published by the company on LinkedIn and appears at the top of this story. Rolls-Royce is responsible for designing and supplying the Pressurised Water Reactor 3 (PWR3) nuclear propulsion plant for the Dreadnought.
In the past, the Royal Navy and the submarine’s manufacturer BAE Systems have published artists’ concepts of the SSBN, like the one above, but they have generally lacked this level of detail. The Royal Navy has, however, already published limited specifications for the boat, which include a displacement of 17,200 tonnes (18,600 tons) and a length of 153.6 meters (504 feet).
As well as the overall highly streamlined hull form, the SSBN features a notably low-profile, raked sail, something that is increasingly common in modern submarine designs. Some designs have gone further still, replacing the previous tower-like sail with just a small fairing, as seen on the small Chinese submarine that appeared in 2019. Meanwhile, the U.S. Navy is looking at the possibility of having its future nuclear attack submarines fitted with non-traditional sails, including ones that are inflatable, popping up when required, but otherwise concealed to preserve the submarine’s speed, maneuverability, and acoustic stealth. The sail on the Dreadnought class is a less radical approach, but it clearly reflects the move toward smaller sails, driven by these requirements. On the model, the sail is topped with at least three periscopes and sensor masts.
A relatively small pair of diving planes are installed in the sides of the hull, in a location immediately ahead of the sail.
In front of the sail, on the top of the hull, there appears to be a post-like structure, which may well be an intercept sonar, as found in a similar location on British nuclear-powered attack submarines.
The new model provides what’s probably the best visual indication of how the SSBN’s submarine-launched ballistic missiles (SLBMs) will be configured within the hull, which has five deck levels.
Compared with previous SSBN designs, the Dreadnought class also has a notably low-profile missile compartment aft of the sail. Rather than projecting out of the hull in a box-like fashion, as on some earlier SSBN designs, this area actually appears to be somewhat sunken into the hull. The missile section is actually divided into three separate missile compartments, each one comprising four missile tubes (known as a ‘quad pack’), for a total of 12 tubes.
The previous Vanguard class SSBNs have 16 missile tubes, but in practice, only eight are carried on patrols, to comply with treaty regulations.
The U.K. Ministry of Defense has also said in the past that only eight of the 12 tubes on each Dreadnought class will be operational, with the other four being filled with ballast to ensure the boat remains stable.
The reasoning behind the reduction in total missile tubes is not entirely clear but reflects a similar trend in the United States. The U.S. Navy’s new Columbia class SSBNs will have 16 missile tubes, compared to 24 on the previous Ohio class SSBNs. However, four of the tubes on each of the Ohio boats were deactivated as a result of arms control agreements with Russia.
Like the Vanguard class SSBNs that they will be replacing, the Dreadnought class will be capable of launching Trident 2 D5 missiles.
A maximum of 40 warheads is currently carried on board the Royal Navy SSBNs when on deterrent patrol, each Trident missile being able to carry multiple warheads, or multiple independently targetable re-entry vehicles (MIRVs). While each Trident can theoretically carry 14 MIRVs, depending on the type, 40 warheads on each patrol amount to approximately five per missile, although how the warheads can be spread across the missiles is variable.
Currently, the Vanguard class SSBNs go to sea with Trident armed with a version of the U.S. W76 warhead, which dates back to the 1970s and is known locally as the Mk 4/A. For the Dreadnought class, the United Kingdom is developing the new A21 nuclear warhead. The A21 was previously known publicly simply as the Replacement Warhead Program and is also now called Astraea; you can read more about it and its progress here.
The Astraea is being developed in parallel with the U.S. W93, which is expected to begin entering service in the 2030s, and the former may well be derived, at least in part, from the latter.
Other armaments for the Dreadnought class submarines will include Spearfish heavyweight medium-range torpedoes, which will be launched from four 533mm torpedo tubes in the front of the hull.
The rear of the SSBN reveals details of the pumpjet propulsion system as well as the X-rudders, which are installed for the first time on a British submarine.
The pumpjet propulsor is designed to reduce the noise of the submarine, especially at high speeds. According to the Royal Navy, the Dreadnought class will be its quietest submarine yet and will be able to achieve a maximum speed of at least 20 knots. Its actual top speed will almost certainly be higher than this, with submarine performance figures generally being shrouded in secrecy.
Generally speaking, pumpjets offer various advantages over propellers, above all the ability to reach higher speeds without noisy cavitation — this means they can transit long distances around much more stealthily. Pumpjets are also more efficient across most of a submarine’s performance envelope and have particular advantages in shallow water. On the other hand, they are also heavy, costlier, and more complex than a propeller.
Immediately ahead of the propulsor are the X-form rudders. According to the Royal Navy, “Whereas previous submarines have used traditional rudders due to their speed and the depths at which they operate, improvements in control and safety now allow for X-form rudders.”
As we have discussed in the past, an X-shaped stern configuration provides improved maneuverability, efficiency, and safety, and also helps reduce the acoustic signature across significant parts of the submarine’s operating envelope compared to the more traditional cruciform system. The X-shaped stern configuration has become increasingly popular and is now found on other submarine designs around the globe, including the U.S. Navy’s new SSBN, the Columbia class. However, while the fins on the U.S. design are staggered, with the two upper ones being mounted slightly further forward, those on the Dreadnought class are, according to the model, all mounted at the same position on the length of the hull.
Not obvious from the model, the Dreadnought class will accommodate 130 crew members, including three chefs, and one doctor. For the first time in a Royal Navy submarine, the boats will also feature separate female crew quarters, toilets, and washing facilities.
The Dreadnought class is scheduled to enter service starting in the early 2030s and the estimated total program cost of around $43 billion makes it by far the most expensive single U.K. defense program — this figure notably doesn’t include the cost of replacing the warheads for the Trident missiles.
The Dreadnought class is a very powerful expression of British military capability, putting it in an elite group of nuclear-armed nations.
The program is also at the center of a warship-building program that should see the Royal Navy receive 28 warships and submarines, including the new Type 26 and Type 31 frigates, the Astute class attack submarines, as well as new Fleet Solid Support ships and Multi-Role Support Ships (MRSS), a new class of amphibious warfare vessels.
This, in turn, is all part of a new-look military strategy, which includes a commitment to increase defense spending to 2.5 percent of national wealth by 2030.
Production of the Dreadnought class will take place at BAE Systems’ complex in Barrow-in-Furness, in the northeast of England, once work on the sven-strong Astute class is completed. The BAE’s construction facility will undergo an upgrade costing hundreds of millions of dollars, which includes an enlargement that will allow it to build the Dreadnought class. In October last year, a “significant” fire took place at the Devonshire Dock Hall (DDH) building in Barrow-in-Furness, as we reported at the time, although there are no reports that it will affect the timeline for the Dreadnought class builds.
While we will have to wait a bit longer to see the first of the Dreadnought class taking shape at Barrow-in-Furness, the latest model presented by Rolls-Royce provides us with what’s probably the most useful indication so far of the appearance of the Royal Navy’s next nuclear ballistic submarine.
Contact the author: thomas@thewarzone.com