The Royal Navy’s Astute class submarines: Part 1 – development and delivery

In the first of a series of articles focussing on the Astute class SSNs, we look at the programme’s history and how decisions made decades ago continue to impact today’s fleet.

Background

In the late 1960s the RN had decided that it would invest heavily in nuclear attack submarines with a force goal of 20 boats, seen as the new capital ships of the day and the most effective weapons to counter Soviet maritime threat. Propelled by a regular drumbeat of construction and development, by the early 1980s it had built the Dreadnought, Valiant, Churchill and Swiftsure classes. These were followed by the 7 Trafalgar class boats, arguably one of the best Cold War SSN designs, delivered to the fleet through the 1980s on time and with an average construction time of about 50 months.

In the late 1970s planners began to consider what would replace the Swiftsure class and began concept development for ‘SSN0Z’. In 1980, the project was suspended as the design teams needed to focus on the Vanguard class SSBNs but in 1984 work resumed on what was now called the follow-on SSN (FOSSN). By 1989 approval had been given for detailed design work to start on the new class which were now referred to as ‘SSN20’ and would have had names starting with ‘W’ (following the ‘V’ used by the Vanguard class). The W class were intended as a high-end boat that would far outclass the Soviet navy’s best (in a similar vein to the US Navy’s Seawolf class) and cost constraints were not a major factor. The end of the Cold War and the 1990 “Options for Change” defence review brought the SSN20 programme to a sudden halt as politicians scrambled to cut defence spending to reap the so-called “peace dividend”. This was the first of a series of decisions that combined to leave a problematic legacy for the RN submarine service.

Trafalgar Batch II

An attempt to build a cheaper/simpler submarine than SSN20 was started and the Government flirted with the idea of buying off the shelf from the US or a joint programme with the French navy. It was quickly realised that buying from the US would work out far more costly and would damage the UK submarine construction industry and the critical strategic ability to build deterrent submarines. Like many similar defence cooperation attempts with the French, it was found not to be practical as requirements and philosophy were too divergent. Instead in June 1991, a £6m contract was awarded to develop a Batch II Trafalgar-class Batch II (B2TC) to an industry team comprising VSEL, British Aerospace, Marconi and Rolls Royce. B2TC would eventually evolve into the Astute class.

An invitation to build the first 3 boats was issued in July 1994. The contenders were the GEC Marconi-led consortium comprising BMT, AMEC, Rolls Royce and Kockums (Swedish conventional submarine builders) against Vickers Shipbuilding and Engineering Limited (VSEL), owners of the Barrow shipyard. GEC Marconi was selected as the preferred bidder in June 1995 but GEC were also allowed to buy out VSEL. This created uncertainty at Barrow with RR and AMEC also withdrawing while the expertise of the assembled teams began to disperse as the government dithered over the contract award.

The contract was finally awarded in June 1997 for the first 3 submarines valued at £2.8Bn including 4 years in-service support for the first two boats. In a conspiracy of optimism, the contractor promised the MoD HMS Astute would be delivered by 2005. GEC Marconi as the prime contractor was responsible for both the design, manufacture and performance of the boats. Previously the outline designs for the majority of submarines and warships were developed by the MoD’s own naval architects in Bath who acted as design authority and project overseers, managing risks and expenditure with a very hands-on approach. This valuable in-house capability with decades of accumulated naval construction experience had started to decline during the 1980s in favour of outsourcing entirely to commercial entities. This was another mistake, one that arguably still negatively impacts the RN.

Astute was supposed to be a ‘low-risk batch II’ option but over time changing requirements had complicated matters. Costs were supposed to be controlled by utilising the Trafalgar’s propulsor, gearbox and steam turbines, elements of the Upholder class SSK design and the integrated Tactical Weapons System upgrade applied to the Swiftsure & Trafalgar classes. The PWR2 reactor, in production for the Vanguard-class SSBN had to be incorporated and it was safer, quieter and more powerful than the PWR1 of the Trafalgars. However, it was considerably larger and the pressure hull had to be increased to 10.7m in diameter. Initial designs (the ‘pregnant worm’) had a bulge to accommodate it but it became apparent a simple constant diameter pressure hull was a better solution allowing a 50% increase in weapons capacity. Although much equipment was incorporated from existing boats, Astute was now a 70% new design and 10 of the 13 major systems on board were completely new or extensively modified compared to the Trafalgars.

Industrial crisis

As GEC began the project it emerged that there was now a lack of specialist submarine designers left in the UK as there had been a 10-year gap since the Vanguard boats were developed. The post-Cold War hiatus and then the delay to starting the Astute class had seen expert designers and engineers disperse to other industries and little new talent being developed. Design work was conducted at the Prime Contractors Office (PCO) in Frimley using the 3D computer-aided design (CADDS5) system that had been used by VSEL to design HMS Ocean. Despite being customised for the job, CADDS5 was not up to the much more complex task of submarine design and there was a lack of experienced staff with CAD skills.

In November 1999, BAe and GEC-Marconi were merged in the last great British defence-industrial consolidation to form BAE Systems which own the Barrow site to this day. Despite the CAD problems, and only about 20% of the design work at Frimley complete, the first steel had been cut in October 1999 as the builders were anxious to meet the contractual milestone. HMS Astute was formally laid down on 31 January 2001. Progress was slow, not helped by a lack of design drawings and the shipyard staff shortages as Barrow was simultaneously involved in reactivating the Upholder class SSKs for Canada, the construction of RFA Wave Knight and the Albion class LPDs. The much smaller BAES team at Barrow in the early 2000s could not match the strength of VSEL of the early 1990s. Also lacking the support and oversight from Bath enjoyed by their predecessors, they were not up to the colossal task of managing both the design and build of a new submarine class. In August 2002 an audit of the project determined that the Astute program was more than three years behind schedule, £700M over budget and work was temporarily suspended. The crisis also resulted in orders for the second batch of vessels being postponed, pending the resolution of the production problems.

BAES worked with the MoD to restructure the programme, and an additional £680M was allocated (£250M from BAES) and a new contract was signed in 2003. The original in-service support element was deleted from the contract in order to save on cost and simplify the task although this stored up major problems for the future. The PCO was moved to Barrow to be on-site and management processes were improved. Critically, 13 submarine designers from General Dynamics Electric Boat in the US were brought on to the project to set up new CAD tools and mitigate the lack of available expertise in the UK. Over 100 designers based in the US also helped create thousands of detailed design drawings needed for manufacture, with $145M eventually paid to GDEB for their services.

Death of FASM

While the Astutes were originally supposed to replace the Swiftsure class boats, the Future Attack Submarine (FASM) project was started in the mid-1990s intended to replace the last 4 or 5 Trafalgar-class boats. Several concepts were explored including three conventional SSK options that were quickly discarded and seven SSNs designs that ranged between 5,000 to 8,000 tonnes displacement, had vertical-launch tubes for cruise missiles or UUVs and had pentaform or X-form control surfaces. The 1998 defence review stated the first FASM would enter service in 2012 but the schedule continued to move to the right. By the start of 2001, FASM was in the Concept phase with Initial Gate scheduled for December 2001 but entry into service had slipped to 2017 due to cost pressures from the Type 45s and carrier project. In May 2001 FASM was cancelled as financial reality and the endless delays meant the Astutes would effectively have to replace both Swiftsures and Trafalgars and SSN numbers would fall sharply.

FASM was replaced by the Maritime Underwater Future Capability (MUFC) project with a remit to look beyond just standard crewed submarine solutions. Initial concepts for MUFC included some very unconventional design approaches including the use of composite materials, a 360-degree ‘platypus’ bow sonar and azimuth water-jet propulsion pods. These very high-risk, ‘blue sky’ options were always unlikely to be adopted but MUFC was also considered a single platform design for both the ‘Successor’ SSBN and a future SSN to replace the Astutes with a mix of vertical launch cells for either cruise missiles or Trident ballistic missiles. Ultimately though, the Dreadnought class SSBN was designed specifically for its nuclear deterrent role. It should be noted that the submarine design expertise and facilities that were expensively re-constituted for the Astute class have been utilised for MUFC and the Successor/Dreadnought SSBN project.

MUFC was delayed for 2 years but formally entered the Definition and Design (PDD) phase in April 2020 with its main focus the SSN Replacement project. In September 2021, two £85 million contracts were awarded to BAES and Rolls Royce respectively for initial design work and 350 people are now working on the SSN(R), the Astute-class successor. HMS Astute was designed to have a 25-year life and will need to undergo nuclear refuelling and life extension if she is to be run beyond 2035. It’s early days for SSN(R) but the first boat is unlikely to arrive before the mid-2040s. SSN(R) will probably be larger than the Astute, based on the Dreadnought hull minus the missile compartment, while retaining the PWR3 reactor, streamlined fin, X-form tail and pump-jet propulsion.

Production

We will not attempt to describe the complex submarine manufacture process in detail but despite the re-baselining of the project in 2003, legacy issues continued to plague construction. Using 3D CAD for design would ultimately drive efficiencies but the workforce of the time was not familiar with plans of such detail and were used to exercising much of their own judgement about how to manufacture and install parts by looking at 2D drawings. There was also a lack of project management skills, an integrated master plan or an effective means to track progress. GDEB expertise helped to gradually overcome these issues and the MoD took a much more hands-on approach to overseeing the project. Some of the initial fabrication of Astute had been conducted in a rather chaotic way and had to be reworked as the design was revised and finalised.

Several major new innovations were introduced during Astute production. The boat is comprised of 8 major construction units which were outfitted to a much greater level than in previous submarines before being joined together. Complete modules for the Manoeuvring Room, Forward Engine Room, Main Propulsion Machinery and Command Deck were fully outfitted and tested before being slid inside the cylindrical pressure hull on rails. Once these modules were in place the hull could be closed with specialist welders required to ensure the joins could withstand enormous undersea pressures. The nuclear regulatory environment had become more stringent and complex over the years and added cost and delay to the project while the shipyard made changes to working practices and procedures. The submarine supply chain had also been allowed to decline since the Vanguards had been completed and BAES and MoD had to take a greater interest in the long-term health of these companies who rely on orders for very specialist items, mostly manufactured in small numbers at irregular intervals.

By the time HMS Astute was rolled out of the hall in June 2007, it was almost 17 years since the yard had conducted the test and commissioning phase of a first-in-class submarine. Engineers with the knowledge to conduct the complex process of bringing all the systems online were in short supply and there was a lack of clarity between the contractor and MoD as to who was responsible for the various steps in the process. There were further mishaps and delays in the T&C phase and HMS Astute did not leave the yard to begin initial sea trials until November 2009.

Into service

Once leaving Barrow the boats never return to the shipyard and the defect rectifications required following sea trials are conducted by the contractor either alongside or in the shiplift at Faslane. The 44,000-tonne Valiant floating Jetty constructed specifically for the Astutes at Faslane was not ready when HMS Astute arrived and they were initially supported by the forward-repair ship RFA Diligence moored in Gareloch. Two phases of Contractor’s Sea Trials (CST) were conducted during 2010 with over 150 engineers and 20 shipyard staff involved in putting the boat’s systems through around 700 test points.

Unfortunately, the start of HMS Astute’s career was marred by two incidents. She ran aground off the Isle of Skye in October 20101 due to navigational errors – highly embarrassing for the RN and the CO was subsequently sacked. The starboard hydroplane was damaged by a collision with the Coastguard tug sent to assist but Astute was eventually pulled off the sandbank at high tide with minimal other damage. In April 2011, while visiting Southampton and entertaining civic dignitaries on board, a disgruntled rating went on a rampage armed with an SA80 rifle. Tragically Lt Cdr Ian Molyneux was killed and another officer wounded before the rating was disarmed by a civilian visitor.

After commissioning in August 2010, HMS Astute began her operational trials period in mid-2011, conducted off the US East coast at the BUTEC ranges she fired torpedoes and Tomahawk missiles. She also exercised with the Virginia Class boat USS New Mexico and proved conclusively that her capabilities matched or exceeded that of the latest US Navy SSN.

During the trials process, serious faults were discovered in this prototype vessel that further delayed Astute’s entry into service. Official comment was limited but the most serious issue was the mismatch between the powerful PW2 reactor and the steam turbines and gearbox derived from the Trafalgar class boats. This issue prevented Astute from reaching the top speed laid down in the original specification (probably more than 30 knots) although this problem has subsequently been resolved. Some construction defects emerged that included corrosion and pipework exposed to full pressure made from the wrong metal that resulted in a leak while at depth and an emergency surfacing. Instrumentation in the nuclear reactor was defective because insufficiently pure lead had been used in the system. These kinds of issues are usually to be expected in a first-of-class vessel and were rectified in time. Astute was finally handed over to the RN in April 2013 and began her first operational deployment in early 2014, almost 15 years after the first steel had been cut.

By March 2021 the Astute project had cost £9.6Bn with boats delivered between 3-5 years behind the original schedule. This necessitated the extension in service of HMS Trenchant, Talent and Triumph with the attendant costs of keeping ageing boats running. The first three Astutes cost a total of £3.53Bn, 21% more than the original £2.8Bn contract.

There were serious delays to boat four, HMS Audacious which had significant internal changes and improvements building on lessons learned from the first three boats. Details about the upgrades are limited but some aspects had already been de-risked and back-fitted to boats 1-3. Updates included changes to the combat system, the elimination of complexity where possible, more use of commercial off-the-shelf (COTS) equipment and better access to make maintenance easier.

The underlying causes of the delay to Audacious have never been properly explained to the public but it had a knock-on effect for the delivery of the last 3 boats. The 4 batch II boats were supposed to cost £5.86Bn but are now expected to total £6.7Bn. The final vessel, HMS Agincourt will cost an eye-watering £1.64Bn, although this compares reasonably well with the $2.8Bn cost of a Block IV Virginia class SSN.

The procurement, design and production process of the Astute class has been extremely problematic but crucially, the actual end products are said to be amongst the best SSNs in the world. Despite their chaotic birth, the designers and builders have succeeded in making an exceptionally quiet boat equipped with arguably the most effective submarine sonar system ever devised. Operated by some of the world’s finest submariners and armed with the latest iteration of the Spearfish torpedo, the Astutes are a truly fearsome weapon. It is a source of lasting regret that the RN will not get more than seven boats and their entry into service has been so stretched out. The Dreadnought class programme at least is benefiting from the many painful lessons from the Astute project and have started their manufacture on a ‘hot’ production line with an experienced workforce ready to go. In a future article, we will look at the design of the Astute class submarines in more detail.