The adage that stealth is a submarine’s main defense is true today and tomorrow. Speed, depth and countermeasures can all help a submarine escape, but not being seen in the first place is the best way to survive. So it is no surprise that the submarines being built today are going to be stealthier than the ones already in service. Certainly in leading ‘nuclear navies’ like the U.S. Navy, French Navy and Russian Navy.
And naturally Britain’s Royal Navy. Their new Dreadnought Class, currently under construction, includes innovative features which promise to take stealth to a new level.
Four Dreadnought Class submarines are being built to replace the current fleet of Vanguard Class boats. They will be armed with Trident D5 missiles to continue the United Kingdom’s continuous at-sea deterrent. The new class will be slightly larger, mainly to incorporate a number of new stealth features. In the underwater arena, being stealthy principally means being quiet, so we can expect the new boats to be the quietest yet.
The Quiet Game: Royal Navy Stealth
The Royal Navy’s emphasis on stealth is already visible in the external appearance of their submarines. Since the 1980s submarines have been fitted sound reducing ‘anechoic’ tiles. And the current generation Astute Class has the anechoic coating designed in. This leads to a better fit and optimal performance compared to adding the tiles after it is built.
The Astute’s hull is completely covered in anechoic tiles. You can see several types of tiles placed on the hull, sometimes in layers, to optimally reduce the target echo strength. Added to this there is a distinct chine running around the bow and the upper hull and sail (fin) are angled to reduce sonar reflections.
Radical New Hull Design
The Dreadnought Class takes this even further. The official graphics used by the builder, BAE Systems, shows the chine running all the way along the hull. This is a strong hint to a completely new style of submarine design. A thin outer hull, like an extended casing, entirely covers the regular cylindrical inner hull. This allows the sloping sides to extend right down the hull instead of being limited to the upper hull.
Dreadnought’s outer hull will be much lighter than the true ‘double hull’ construction typical of Russian submarines. And its purpose is different. We know from the common missile compartment, which will be the same as is used on the U.S. Navy’s Columbia Class, that the submarine hull remains the single-hull type. This means that it has its strengthening rings (called frames) on the inside. Russian boats have these frames on the outside, between the two hulls, and use the outer hull as part of their structure. On Dreadnought the outer hull is about stealth.
As well as being angled to deflect incoming active sonar, it will be coated with anechoic tiles. And it is a safe bet that the anechoic coatings will extend to the inside, in the flooded area between the inner and outer hulls.
Some other submarines are also adopting this new take on a double-hull submarine. The German designed Type-212CD will include an even more visible angled outer hull. There is no suggestion that the British design is borrowing from the German boat however. And the complex multi-layer anechoic treatment is likely unique.
The outer hull will also present some advantages, creating more space under the casing. We can speculate that this could accommodate future sensors, uncrewed underwater vehicles (UUVs) and countermeasures. It also seems likely that the boat’s flank array sonars will be mounted flush with the outer hull. This will be a cleaner than the current British and American boats which have them added as patches.
'Built with pride in Barrow'- the latest piece of Dreadnought makes a move. Four Dreadnought-Class submarines will be built in Barrow to replace the Vanguard-Class that are currently in service with the Royal Navy. #Submarines #Cumbria @RoyalNavy @SamPlum4 @cumbrialep pic.twitter.com/I1pWxNQ5aB— BAE Systems Maritime (@BAES_Maritime) July 6, 2020
And There Is More…
Other improvements to stealth will be internal. For many years, and still in some other leading navies, the main focus for making the submarine stealthy was in make the propulsion quieter. Royal Navy boats are already considered very quiet in this regard. But the Dreadnought will incorporate new Turbo-Electric drive.
Turbo-electric drives use the nuclear reactor to generate electricity. This powers an electric motor which drives the propulsor. This should be quieter than driving the propeller shaft directly. While turbo-electric drives have been used aboard nuclear submarines before, this (together with the U.S. Navy’s Columbia Class) will be the first time it has been used on serial production boats. And on the Dreadnought it will be driving an improved, quieter, pumpjet propulsor.
Like the stealthiest existing submarines Dreadnought will feature ways to protect against electromagnetic detection and tracking. And we can speculate that it’s outer surface will be a different color to previous versions. Possibly blue, to improve visual stealth when near the surface. Although that is less of a concern in the SSBN’s natural habitat in deep waters of the North Atlantic region.
Dreadnought is a massive undertaking for UK industry. But research and investment in submarine technologies, over many years, should pay off. Of course a lot of this will not be confirmed until the submarines are rolled out of the shed. There is a natural tendency to secrecy surrounding submarine design. And often features are added or subtracted during construction, often for cost reasons. However, based on what we know currently, expect the Dreadnought Class to take stealth to the next level.