It has emerged that the Royal Navy plans to acquire up to three “survivable, non-complex warships” designed from the outset as mother ships for autonomous minehunters.
Non-complex warships
The need for four offshore support vessels (OSVs) or motherships to support the future minehunting capacity (MHC) has been known for some time. Although they were envisaged in the National Shipbuilding Strategy, it was unclear whether the three final vessels would be ‘lightly converted’ merchant ships, similar to RFA Stirling Castle, heavily modified merchant ships, or newbuilds. Assuming funding is approved, it is clear that the Royal Navy wants to build warships to a bespoke design, flying the White Ensign flag and named ‘HMS’, possibly continuing the Castle-class nomenclature.
The Royal Navy wants the motherships to be built to higher damage control and survivability standards than would be the case for a converted merchant ship. It is expected that these ships will have some self-defence capability, military communications equipment and more sophisticated sensors than just a navigation radar. The level of self-defence capability is yet to be defined but could potentially include more than just crew-served light weapons. It is becoming increasingly obvious that any naval vessel on the drawing board today should have powerful anti-Unmanned Aerial Vehicles (UAVs)/UAS capabilities as a basic fit.
MHC block 2
RFA Stirling Castle has conducted some initial testing, but her limitations in the intended role are already apparent. Her purchase was well worth the money and provides an excellent testbed for MHC Block 1, the pioneering program to introduce autonomous minehunting into Royal Navy service. (More details on the progress of Block 1 in a future article.) MHC Block 2 will be considerably more ambitious and will require motherships with corresponding capabilities.
RFA Stirling Castle does not have a dedicated launch and recovery system (LARS), apart from a crane and the 600 m2 Working deck is not large enough. Deck area of at least 1000m2 is required to house the USVs, UUVs, Portable Operations Center and supporting equipment that make up a mission module. In a live mine warfare operation covering a large area, multiple USVs must be deployed to achieve the same (and ideally better) effect than existing MCMVs. This requires a large deck with plenty of space for equipment.
Future USVs may be larger than the first generation 12-15m boats, and the motherships will need LARS of sufficient size to accommodate them. Robust LARS capable of handling unmanned boats weighing several tonnes in difficult sea conditions and strong winds are specialist pieces of equipment, and there are already several companies offering advanced solutions. A stern ramp can also provide an alternative launch/recovery option depending on weather conditions and type of boat.
Initial experience of autonomous minesweeping with the RNMB Harrier operating in the Gulf from RFA Cardigan Bay and from land has highlighted the need for better situational awareness. For MHC Block 2, the RN is interested in medium-sized UAS that provide basic ISR capabilities. These could be provided by the Peregrine RWUAS (which begins its first deployment in RN service from HMS Lancaster in the Gulf very soon). Rotorcraft are easiest to pilot from a small ship, but cheaper options than Peregrine may suffice. The cost and hassle of a dedicated flight deck may not be justified if the RWUAS can fly from the spacious working deck.
MHC Mothership Concept 2
This is just a rough concept. It is loosely based on an existing commercial OSV hull and propulsion system, but with improved watertight compartmentation, firefighting and damage control capabilities.
Present
One of the most serious issues with moving to unmanned minehunting is the loss of the presence provided by a conventional MCMV platform. A manned warship provides a level of deterrence to adversaries and could be a rallying platform for allies. The Royal Navy can no longer contribute MCMVs to NATO mine countermeasures groups or exercises. The mothership could act as a command/support ship for an MCM group, providing the advanced autonomous minehunting capabilities that many navies do not plan to introduce in the near future.
The dedicated motherships would act as force multipliers. The long-term Bahrain-based Bay-class ship (or future MRSS) could return to its primary amphibious role. Beyond mine warfare, the OSVs would also have the flexibility to contribute to the Royal Navy’s larger undersea fight. In this secondary role, the external systems deployed by these ships could also perform anti-submarine warfare and seabed warfare and military data collection missions. In extreme cases, they could also be adapted for surface engineering support, diving, salvage and submarine rescue operations.
In theory, by accelerating the retirement of its MCMVs, the RN has created budgetary headroom for MHC Block 2. The NAO report on the MoD’s equipment plan, published in November 2022, states that Block 2 is not yet funded. A budget line should be established, subject to further development of the business case and subsequent approval in the Defence Review expected next year. Failure to fund MHC Block 2 would be disastrous, as the RN would then be left with a greatly reduced MCM capability as it follows the high-risk strategy of divesting conventional assets before autonomous systems are proven and operational.
The construction of the three motherships in the late 2020s to early 2030s is another significant project for UK naval architects and shipbuilders, and further justifies the expansion of capability. However, it is not inconceivable that budget pressures will lead to the motherships being downsized and new-build warships being replaced by cheap merchant ship conversions. The surface battlespace is becoming increasingly dangerous, and the benefits of autonomous minehunting will not be realised if the systems cannot operate in contested waters.
Provided MHC Block 2, including the mothership project, goes ahead, this will help restore mass and underpin the global reach of the Royal Navy’s mine warfare force.