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Major Advance in Royal Navy Nuclear Submarine Technology and Performance By Howard Wheeldon, FRAeS, Wheeldon Strategic Advisory Ltd.

tridentWith the ‘Successor’ Trident Nuclear Submarine replacement programme ‘Assessment Phase’ now nearing completion and with the all-important ‘Main Gate’ investment point targeted by the previous Coalition Government back in 2011 due to be reached at some point during this year the hugely complex military engineering endeavour that is ‘Successor’ will, subject to final commitment to renewal being given by the House of Commons, hopefully very soon be moving forward into the production engineering and build stage.

By the time that ‘Main Gate’ occurs at some point this year well over 70% of the design phase of ‘Successor’ will have been completed. To get this far has required six years of very hard work on the part of the programme partners, BAE Systems, Rolls-Royce and Babcock International just as it has for the hundreds of component suppliers that have already and that will be increasingly involved in the years to come.

A complex programme such as ‘Successor’ demands the highest possible level of engineering skills be secured and retained and at a time when few would argue that as a nation we are suffering a huge shortage of engineering and technical skills. The excellent work done by industry and the MOD customer, the latter particularly in the form of DE&S which has worked hard to ensure that the development process of working with industry has been as smooth as it possibly can, must also be recognised. The modular build process of ‘Successor’ when it eventually occurs will be quite different to how the predecessor Vanguard submarines were built at Barrow-in-Furnace but the companies that have designed and that will build this terrific and complex capability are ready. They have embraced change and they are ready for next stage of the production engineering challenge.

In this first UK defence paper of 2016 I will today attempt to provide a view and update of where I believe the important Trident replacement programme now is. I will also take the opportunity at the end of this piece of providing a short history of the three separate generations of UK submarine based nuclear deterrent capability.

Challenging as it has been demanding ‘Successor’ nuclear submarine capability will, when it finally emerges, be a step change forward in terms of technology development over the existing fleet of Vanguard Class Trident submarines that ‘Successor’ will eventually replace. This is a really complex engineering programme and one that has required industry to think outside of the box as, working with the MOD customer, it has sought to design and build a vital military capability that may still be in service fifty years from now.

Britain has operated an independent submarine based nuclear deterrent capability since 1968 and for all the years since it has been deployed by the Royal Navy on a continuous-at-sea basis. No matter whether we view our nuclear deterrent the capability as being independent or not the vast majority of those that understand the need for strong defence will agree that having our nuclear deterrent capability has deterred our ‘would-be’ enemies including the most destructive forms potential aggressor. Our nuclear deterrent capability is there not only to provide the ultimate means of defence for the UK of course but for our NATO allies as well.

2016 represents the 47th year that the UK has relied on continuous-at-sea submarine based nuclear deterrent capability. True, over the past decade the number of operational missiles carried on our Vanguard Class Trident nuclear submarines has been reduced in accordance with the commitment made within the Non-Proliferation Treaty.

The missile plan, as outlined in the SDSR 2010 strategy document published five years ago, is that the next generation of nuclear submarine capability will carry fewer operational missiles with the number reduced to eight and which in total would mean carrying no more than forty warheads.

As it moves to the end of the assessment phase and toward what in defence procurement parlance terms we now call ‘Main Gate’ the important production engineering process will begin. That is not to suggest that the design engineering process has ended yet but it signals the formal start to a massive build engineering programme that will last into the second half of the 2030’s. Assuming that commitment to renewal will be given by the House of Commons sometime during this year, Successor will officially be the third generation of Ship Submersible Ballistic Nuclear (SSBN) capability in Royal Navy service.

There are a great aspects of ‘Successor’ development programme have been built out from what has been learned during the development and build of the Astute Class submarine. Astute has had its issues in the past and as programme that BAE Systems effectively inherited well into the build process they have done extremely well to ensure that the end capability provided is what the customer demanded. Astute is a nuclear powered attack submarine fitted with conventional weapons. Substantially larger capability than the Trafalgar Class nuclear powered submarines that they replace, a total of seven ‘Astute’ Class boats will have been built by the time the contact ends. To facilitate building of the larger ‘Successor’ Class vessels a £300 million infrastructure upgrade programme due for completion in 2022 is already under way at BAE Systems Barrow-in-Furness facility.

There are though significant changes in ‘Successor’ Class vessel requirement that for the most part have been led by a combination of capability operating efficiency and safety demands together with innovation and change requirement. While the overall mission that Successor will play out as it patrols the oceans around us may not have changed the requirement of what we must be able to provide has. With ‘Successor’ Class capability expected to be in service with the Royal Navy until the midway through the 2060’s and possibly beyond that means that the most up to date design and technology available is required to meet longevity demanded. Babcock International will, as it has done throughout the life of the Vanguard Class nuclear submarine deterrent capability, provide through life support and maintenance requirements for Successor.

Both MOD customer and the BAE Systems, Babcock International and Rolls-Royce supplier partnership have embraced the technology requirement of ‘Successor’ just as they have recognised the importance of holding down costs. They have been incentivised to do that. The revised cost of Trident replacement covering four new Successor Class submarines is £31bn plus a £10bn contingency. While this is substantially more that the inflation adjusted £20bn final development and build cost of Vanguard class through the 1980’s and 1990’s the complexity of ‘Successor’ Class development, technology change and safety related requirement, the substantial change in weapons systems delivery requirement including a newly designed missile compartment, electrical systems and increased system and mission demands make drawing parallels between the two programmes and which are over thirty years apart futile.

Just as the Vanguard Class Trident submarines that will remain responsible for UK nuclear deterrent capability for maybe another twenty years cannot be sensibly compared in terms of cost or improved mission capability over those of the Resolution Class Polaris submarines that they replaced attempting to make cost comparisons between one programme and another when so much technology and mission requirement has changed is probably unwise. Much has also changed over the past few years in terms of requirements for best practice and that can ensure greater safety and through life efficiency combined with lower operating costs.

A good example of engineering and technology advancement and that of inevitability comes at a higher costs is the ‘Successor’ propulsion system. Over the years Rolls-Royce has built over 30 submarine nuclear plants and no fewer than 100 reactor cores. It is well respected for the technology it has developed and built and no other UK company is better versed in the complexity of the nuclear propulsion and that I would argue is vital UK sovereign capability. Having completed the development work in 2014 on a new pressurised water reactor based propulsion system known as PWR3 and that will power ‘Successor’ Class submarines the engineering design process will move into the production engineering phase.

It is at this juncture worth noting that both Vanguard and Astute Class submarines are powered by PRW2 Pressurised Water Reactor propulsion system that was also designed by and built Rolls-Royce, the design of which goes back to the late 1980’s. Highly successful and reliable though PRW2 has been in service it is true to say that both technology and increased systems demands together with ever greater safety requirement in any nuclear environment required that Successor class would have a completely new propulsion system. For the record, a basic PWR propulsion system works by using nuclear fission to generate heat which is then used to turn water into steam to turn the main turbines that propel the submarine through the water.

The PWR3 that will power ‘Successor’ Class is a completely new design of pressurised water reactor capability that exploits technology not available at the time when the Astute Class submarine design was being finalised in the mid 1990’s. Complex engineering design never stands still of course and in this case the innovation of the PWR3 design has been to produce a far less complex and easier to operate propulsion system to the point is that it can achieve both a substantially longer in-service life and lower through-life maintenance costs.

Another important point to emphasise is the much greater requirement for safety to be built into the design and build process. As regulations have changed so too has the need for improved safety requirement. Much has changed since the mid 1980’s when Vanguard class submarines were designed and built and that would see a requirement for additional safety issues to be built in during the later process of refits. Safety requirements are paramount today and under the MOD and industry duty holder obligations and we may anticipate that many have needed to be built into the PWR3 propulsion system just as they have across the rest of Successor.

I recall also that back in 2011 the MOD requirement called for a 25 year life of the propulsion system with the option of at least a five year extension. In addition the overall requirement needed to be combined with suitably low detectability. Noise and vibration is no option for Successor Class submarines.

The PWR3 is but one example of innovation requirement and technology change on Successor compared to what has gone before. There are a great many that we cannot know because quite simply these are off-limits. What we do know is that Successor is the largest new design iteration in nuclear power based propulsion systems that has taken place for the past 25 years and that, Trident weapon apart, it is all UK sovereign design capability. To get it right has required significant investment in test rig equipment

By its very nature nuclear submarine design and build is extremely complex. Indeed, engineering complexity defines all nuclear capability options and I seem to remember many years ago saying that for every one engineer conventional capability programmes four are needed in nuclear. Indeed, Rolls-Royce has been required to grow and upskill across a wide range of engineering disciplines to accommodate the design requirement and develop a new generation of engineers and technical leaders in a relatively short period.

Scrutiny is also extremely important and my understanding is that during the design process in terms of the propulsion plant no less than 500 technical documents have been required by the MOD customer.

Clearly decisions to go with technology change and superior performance that the PWR3 propulsion system has been designed to provide will have increased the overall Successor cost. But as the benefits can be expected to outweigh the increased costs and mindful that the PWR3 propulsion system has been designed to have a considerably longer service life than the PWR2 I for one am not concerned by this possibility. Indeed, I believe that as a nation that we need to be more open to invest in our own future and in order to win we need to think a lot more about innovation and advanced technology design rather than cost. I suggest also that that the push for innovation and change that provides Successor Class submarines to do the job better and more efficiently has been driven in equal measure by the MOD customer and contractor. If not already involved Successor will, assuming the final go-ahead is given, support jobs in a great many UK companies.

When compared to the Successor predecessor Vanguard class submarines I venture to suggest that demands placed on the propulsion systems for outright power will, due to a combination of mission and raised specification needs, have significantly increased.

Interestingly, containing 30% fewer pumps, component parts and maintenance requirements and yet able to meet not only significant increase in safety requirements demanded the PWR3 propulsion system is able to provide more efficient capability and reliability is terms of what the customer has demanded. BAE Systems which is responsible for the design phase of Successor and which in excess of 1,400 employees working on the project and over 240 suppliers engaged along with Successor partner company, Babcock International are all working for the self-same ends – to provide the capability that the MOD wants, on time and on cost.

The Coalition Government was absolutely right in my view to take the decision at the ‘Initial Gate’ process to be mindful of the opportunities presented by technological developments since the design of the Astute Class and in particular, the requirement to sustain the capability throughout the life of Successor Class into the mid 2060’s. Successor design embraces a need that is optimised to the unique role of a nuclear powered and armed submarine capability requirement.

It seems entirely possible that the existing Vanguard Class Trident submarines will be given a further life extension taking these out to 2035 and possibly beyond. HMS Vanguard is currently be refuelled and overhauled and it may well be that a further refuelling of the second of class, HMS Victorious is contemplated. However, if Vanguard Class life extension is being contemplated I would suggests that this is being done for cash flow purposes as opposed to any other reason. Neither would I see this slowing down the build programme start.

As implied in my heading, I believe that Successor really is a step change in submarine technology development and that in this respect it may be regarded as being unique in terms of global sub-surface design capability enhancement. This is a completely new generation of submarine capability and who knows what other benefits the work that BAE Systems, Rolls-Royce, Babcock International and others have done getting Successor to this point may lead too. The four Successor Class SSBN’s when complete (the first is currently due to be commissioned in 2028) will deliver leading edge UK developed science and engineering based technology that will not only have been seen to deliver on customer requirements but also in a cost effective, timely and efficient manner. It will also play big part in retaining, growing and promoting high skilled engineering and manufacturing jobs that the nation so urgently needs and hopefully provide a boost to need to train more people for further new generations of complex defence and aerospace engineering products.

Clearly all parties understand that cost and affordability are issues and industry is the first to recognise this. I have outlined some of what we know differentiates ‘Successor’ from ‘Vanguard’ but of course, due to ‘Successor’ design development being high security there are many other aspects of the programme development that we do not and may never know.  Innuendo that attempts to compare ‘Successor’ Class design, development and potential build costs with those of the Vanguard Class submarines that were designed and built thirty years ago is I suppose rather like comparing development and build costs of a ‘Leander’ Class Frigate with those of a Type 26. All military programmes are different and they are all complex in terms of engineering design. These days nothing stands still for long. Technology, mission capability requirement, system demands and safety are constantly changing variants and they probably always will be.

A final point that I would make is that sustaining nuclear deterrent capability today accounts for around 6% of the annual defence budget, equivalent to 0.13% of total government spending.




Resolution Class Polaris SLBN’s:


Following the signing of the original Polaris deal between the UK and USA in 1963 the nuclear powered submarine capability chosen to deliver the US designed and built Polaris nuclear capability was in the form of four ‘Resolution’ Class submarines for the Royal Navy. The vessels, HMS Resolution, Repulse, Renown and Revenge were to be built at a combination of the then Vickers Armstrong yard Barrow-in-Furness (now BAE Systems primary submarine capability) or at the then Cammell Laird shipyard in Birkenhead. Designed and built in the UK and powered by Rolls-Royce designed and built PWR1 pressurised-water nuclear reactors together with English Electric turbines, the first vessel of the class, HMS Resolution was commissioned into Royal Navy Service in 1967. The four Resolution Polaris submarines operated for a total of 28 years between them until the last was decommissioned in 1996.

‘Resolution’ class vessels were equipped with the US built ‘Polaris’ Submarine Launched Ballistic Missile (SLBM’s) although the boats were generally referred to as SSBN’s (Ship Submersible Ballistic Nuclear) capability. The Resolution Class was an adaptation of the earlier Valiant class SSN (Ship Submersible Nuclear) powered submarine capability. While the four Resolution class vessels had an excellent record in service because they lacked technology that would later be incorporated into Vanguard Class SSBN boats they were expensive to operate particularly in terms of manning and maintenance requirement.

Vanguard Class Trident SSBN’s

Following an agreement signed between the British Prime Minister, Margaret Thatcher and US President Ronald Reagan in 1982 that allowed the UK to procure the US designed and built Trident 11 (D5) nuclear ballistic missile the UK government lost no time in authorising the design of Vanguard class nuclear powered submarine capability. As with the Resolution Class Polaris equipped boats, the new submarines would be based on a continuous-at-sea requirement. Four vessels, HMS Vanguard, Victorious, Vigilant and Vengeance, were built at the Barrow-in-Furness yard of Vickers Shipbuilding and Engineering (VSEL) and which is now part of BAE Systems. The four Vanguard class submarines were built between 1986 and 1999 and commissioned into Royal Navy service from 1993 until 1999.

The Vanguard class submarines had been the largest that had ever manufactured in the United Kingdom. A special purpose-built manufacturing facility, the Devonshire Dock Hall, had been built by VSEL at Barrow-in-Furness for their construction and I was very fortunate in having been invited to the opening of this facility in 1986.

The Vanguard Class submarines were significantly larger than the Resolution Class vessels that they replaced mainly because of the need to accommodate the Trident D5 missile and that both technology and mission requirement had significantly changed. However, the complement of a Vanguard Class boat is somewhat smaller than that of Resolution class vessels – 132 officers and men compared to a crew requirement of 149 on a Resolution class vessel. The Vanguard Class boats include a number of significant engineering and technology capability improvements over the previous generation British submarines, including a new nuclear propulsion design system – the Rolls-Royce PWR2 nuclear reactor, GEC built turbines and a new tactical weapon systems designed for self-defence purposes both before and after missile launch. The 16-tube missile compartment is I believe based on the design of the 24-tube system used by the United States Navy’s Ohio Class Trident submarines.

Some fourteen years after the start of the Trident project, the first submarine, HMS Vanguard, entered service on time and schedule in December 1994. HMS Victorious repeated that achievement, entering service in December 1995. The third Trident submarine, HMS Vigilant, was commissioned in Barrow on 2 November 1996 and conducted her first patrol in June 1998.  The fourth and last UK Trident submarine, the HMS Vengeance, was launched at the Barrow-in-Furness shipyard in Cumbria on 22nd August 1998, commissioned into the Royal Navy at the GEC Marine (formerly VSEL) shipyard in Barrow-in-Furness, Cumbria on 27 November 1999 and conducted its first patrol in February 2001. The estimated cost of the Vanguard class build programme was I believe in the region of £12.57bn.

Vanguard class was a purpose built nuclear ballistic missile carrier but it incorporated a selection of successful design features from other British submarines.

At 16,000 metric tons the Vanguard class vessels have almost double the displacement of the Resolution Class Polaris submarines that they replaced and that had been merely adapted from Valiant class submarines.



In December 2006, then British Prime Minister Tony Blair confirmed the Government intention to retain and modernise the UK’s independent nuclear deterrent and that it would replace the existing Royal Navy Vanguard-Class nuclear-powered (SSBNs) with three or four of the next-generation Successor submarine. In May 2011 the Successor programme entered the ‘Initial Assessment Phase’. Oto s at this point that the vessel concept, requirement and system are finalised.

Modelled in part on the in-service and currently in-build Astute-Class (SSN) submarines, Successor class vessels would be powered by a third-generation (PWR3) nuclear propulsion system developed by Rolls-Royce in collaboration with US Navy. The boats would feature a leading-edge hull design from BAE Systems and eventually be built at BAE Systems Barrow-in-Furness facility in Cumbria. The vessels would have superior missile capability and enhanced electrical systems together with what was then called the next-generation Naval Propulsion Plant. This would have extensive passive features and be designed for disposal; extensive use of automation for submarine control, damage control and condition monitoring; full electric propulsion with shaftless drive; externally mounted tactical weapons; electrical actuation of control surfaces and replacement of obsolete technologies with off-the-shelf equipment.

In the context of what I said earlier in regard of complexity it is worth recalling what Tony Johns, Managing Director at BAE Systems’ Submarines, said at the time of the March 2015 contract funding award “designing a new, nuclear-powered ballistic missile submarine is one of the most challenging engineering projects in the world today. The Successor programme is the largest and most complex project [that] we have ever faced. The funding will now allow us to mature the design over the next 12 months to enable us to start construction in 2016.”


(Note that, due to the ease of ability in finding previously written defence related commentary pieces, chosen to revert back to a numbered based system for defence related papers. However, I will not move back to the volume based system which I abandoned at the end of series Eight. Thus, on the basis of their having been forty UK Defence commentaries per volume this means that together with those written over the past year the current piece is the 343rd in the UK Defence series since the first appeared in 1997).


CHW (London – 18th January 2016)

Howard Wheeldon FRAeS


Tel: 07710 779785


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