Should the RN consider buying conventional submarines, even at the expense of frigates?

The 2015 Defence Review promised the UK would build a new ‘cheaper and simpler’ frigate to complement the more expensive Type 26. This Type 31 frigate offers the attractive possibility that the total number of Royal Navy warships could be increased, albeit after 2030. Threats to surface ships continue to proliferate, adding to the challenge of making the Type 31 a credible warship. Meanwhile, the undeniably potent RN submarine fleet is far too small. Here we ask if the RN should prioritise expanding its submarine force with the same enthusiasm it applies to frigates.

The predominant concern in recent discussions about the strength of the RN has been around the need for more frigates. There is no argument that surface escort numbers are at a very low level indeed. If current programmes run on time, the Royal Navy will need to manage with 19 frigates and destroyers until 2030 at the earliest. We have written previously about the value of investment in capability of OPV’s to ensure warships deploy in combat roles rather than undertake constabulary and humanitarian missions, and this will hold true for at least the next 14 years – retaining Batch 1 OPV’s in service would be helpful in this respect, particularly given incoming pressures on Royal Navy to patrol the UK EEZ post-Brexit.

It is also clear that in the interim, the Royal Navy will need to invest in weapons and emerging technologies to maximise capabilities of Type 45 and Type 23. A replacement for Harpoon, installing Mk 41 VLs on T45 and expanding use of unmanned platforms are medium term aspirations. Beyond that, directed energy weapons, advanced decoys, and torpedo defence measures will be needed for the surface ship to survive in the ever-more demanding naval environment of the future. As ever in discussions about future equipment, ensuring there is sufficient trained manpower available both in the short and long-term is critically important.

Setting aside what happens in the immediate future, the Royal Navy would ideally want to have at least 24 surface combatants to meet standing deployments and provide sufficient numbers to independently sustain a carrier task group without partner nation support. This is still well below the size of the fleets of the past, but there is an acceptance that modern surface combatants have become increasingly expensive to build, and numbers have to be constrained. The French Navy is planning just 15 frigates and destroyers of varying capability as the core of its future surface fleet.

The reasons behind increasing cost are relatively clear – the modern frigate needs to have a broad spectrum of offensive capability, as well as being able to self-protect against sophisticated electronic and cyber warfare, complex anti-shipping missiles (including hypersonic and potentially ballistic weapons) and the enduring threat of the submarine. In a future conflict, the absence of any these capabilities will leave any surface combatant extremely vulnerable.

Speaking up for the silent service

Lurking on the margins of the debate about surface combatant numbers is the painful truth that the surface fleet is fairing relatively well compared to the submarine service. Whilst the Astute class submarines entering into service are extremely capable, only seven are planned and these will be spread thin especially when assigned to support future carrier task group operations, conduct independent patrols and protect the deterrent submarines. Procuring additional SSN’s seems unlikely, not least because they are ferociously expensive. The latest boat, HMS Audacious is priced at a staggering £1,492m.

There are alternatives. The development of advanced diesel-electric hunter-killer submarines (SSK) such as the German Type 212 enables extended periods of submersion of up to three weeks. Battery technology continues to improve, it could even supplant the complex Air Independent Propulsion(AIP) systems currently required. Whilst lacking the global reach of an SSN, at around £500 million the initial outlay is marginally more than the likely cost of a Type 31 frigate, but with much lower through-life costs, with a typical complement of 30, compared with around 100+ for a frigate.

Although more limited in some aspects of capability than a frigate, modern SSK’s enjoy a number of advantages over surface combatants, not least that they are extremely hard to detect and destroy. They have also proven highly effective – in an exercise in 2013 the U-32 eluded the entire anti-submarine warfare capability of a US carrier group and succeeded in firing dummy torpedoes, effectively sinking the carrier.

As a result SSK’s continue to pose a threat to opposing naval forces which need to commit significant resources to anti-submarine warfare, and are increasingly capable of deploying a broader range of technologies including mast mounted UAV’s, guns (for patrol or constabulary duties), alongside anti-shipping, surface to air and land attack missiles. Smaller and more agile, SSK ideally suited for operations in shallower littoral waters – close into shore to deploy special forces, or in the Gulf, for example – where SSN’s may be less effective. For the RN, a small fleet of SSKs would be invaluable for operations around the UK and in European waters, providing the first line of defence against foreign submarines, providing a step-change in UK ASW capability. More boats would reduce the enormous pressure on the undersized submarine force and release the SSNs for global deployment. Small conventional boats are far better suited for training, particularly for officers to gain command experience before graduating to the SSNs and SSBNs. At present, the RN must either conduct training using its precious and very expensive SSNs or rely on sending personnel to train on allied submarines. The surface fleet would also benefit from greater ASW training opportunities and a different kind of opponent.

Constraints on submarine construction capacity

The Barrow shipyard, the UK’s only submarine construction facility, will be busy completing Astutes and then Dreadnought SSBN orders into the late 2030’s. Delays in Dreadnought procurement mean that some of the Astute SSN’s currently entering service may need to be decommissioned before manufacturing capability is free to build their replacement. Assuming the Astute boats do not need mid-life reactor refuelling, as was the intention at the start of the project, HMS Astute’s reactor will reach the end of its life and she will need replacing by the next generation SSN by 2035 at the latest.

Including an advanced SSK building programme in the National Shipbuilding Strategy for the 2030’s onwards could deliver continuity in submarine design capability beyond completion of the Dreadnought programme and provide a bridge in manufacturing and capability until the Astute replacement is available.

The SSNs must remain the RN’s priority but design and procurement for SSKs would need to start sometime around 2022 and could help to significantly de-risk pressures on the Astute replacement, as well as offering a much-needed boost in submarine numbers from 2030 onwards. Expanding manufacturing capability to build smaller non-nuclear submarines also appears a more affordable option than significantly increasing the rate of SSN construction and could one day offer export potential.

Royal Navy Submarine construction 2000 2044

The infographic above illustrates the approximate decommissioning, construction and replacement schedule for the Royal Navy’s submarines (Click here for larger version), together with a proposal to acquire SSKs.

The funding the build-up of additional skilled manpower together with expanded facilities to build conventional submarines in the UK would be a very significant challenge. Although potentially politically unattractive, purchasing the hulls and propulsions systems directly ‘off the shelf’, constructed in Germany which has years of specialist SSK design & manufacturing experience, would be a considerably quicker and cheaper alternative. (France, Sweden and Japan also have SSK design and build capability that could be considered). This would go aginst the long-standing government policy of not building fighting vessels abroad but they could at least be fitted out in the UK with RN standard weapons and electronics. Alternatively, an existing SSK design could be licenced from abroad and technical experts brought to the UK to assist with the project.

Choices, choices…

Any expansion in RN warship numbers is a long way off, and sustaining or improving the capability of current and planned vessels, and supporting the necessary manpower to make them useful must remain a priority.

Looking beyond 2030, the Royal Navy needs to ensure the best balance in terms of overall capability to project power and defend the UK’s interests at sea. Frigates will remain essential for sea control purposes and as escorts for capital ships, but ‘wont of frigates’ must not be the only consideration in deciding on the overall shape of the fleet.

If the Royal Navy can cope with 19 surface combatants over the next 13 years (which it will have to do in even the best-case ship building scenario) it may do well to consider investing more heavily in expanding the submarine service which offers a different but equally effective way to project power. A mixed hunter-killer fleet of twelve or more SSN and SSK, alongside around twenty frigates and destroyers, looks a far more balanced proposition, and potentially better value for money, than increasing frigate numbers alone.

The benefits of additional submarines are considerable. Even if some funds were diverted from frigate construction, it should be recognised that building, manning and generating a new infrastructure to support advanced SSKs presents a difficult, but not insurmountable task that would need considerable political backing.

Thanks for John Dunbar for the major contribution to this article