It has emerged that the RN plans to acquire up to three “surviving, non-complex warships” which were originally designed as motherships for autonomous mine-hunting boats.
Non-complex warships
The requirement for four Offshore Support Vessels (OSVs) or motherships to support the future Mine Hunting Capability (MHC) has been known for some time. Although written into the National Shipbuilding Strategy, it was unclear whether the three final vessels would be “light touch” conversions of merchant ships similar to the RFA Stirling Castle, heavily modified merchant ships, or new vessels. Assuming funding is approved, it is clear the RN wants warships built to a custom design that will fly the White Ensign and be “HMS”, perhaps continuing the Castle class nomenclature.
The RN wants the motherships to be built to higher standards of damage control and survivability than would come from converting merchant ships. It can be assumed that these ships will have some self-defense capability, military communications and sensors more sophisticated than just navigational radar. The level of self-defense capability has yet to be defined, but could potentially include more than crew-served light weapons. It is increasingly clear that every naval vessel on the drawing board today should include a powerful adversarial UAV/UAS as a baseline.
MHC block 2
RFA Stirling Castle has conducted some early trials, but its limitations in its intended role are already apparent. Its purchase was very good value for money and provides an excellent test platform for MHC Block 1, the RN’s autonomous mine hunting program. (More details on progress with Block 1 in a future article). MHC Block 2 will be significantly more ambitious and require motherships with sufficient capacity.
RFA Stirling Castle lacks dedicated launch and recovery systems (LARS) other than crane and 600m2 the work platform is not large enough. Deck space at least 1000 m2 is needed to house the USV, UUV, portable operations center and support suite that make up the mission module. In a live mine combat operation covering a large area, more USVs will be required to achieve an equivalent (and ideally better) effect than existing MCMVs. This requires a large deck with plenty of room for a tool kit.
Future USVs may evolve to be larger than the 12-15m boats of the first generation and motherships will need LARS of sufficient size to accommodate them. Rugged LARS, which can handle unmanned ships of several tons in rough sea conditions and strong winds, are special equipment, and there are several companies already offering advanced solutions. A stern ramp may also provide an alternative launch/recovery option depending on weather conditions and vessel type.
Earlier autonomous mine hunting experience with the RNMB Harrier operating in the Persian Gulf from RFA Cardigan Bay and from shore highlighted the need for greater situational awareness. For block MHC 2, the RN is interested in medium-sized UAS to provide basic ISR capabilities. This could be provided by the Peregrine RWUAS (Very soon to begin its first operations in RN service flying from HMS Lancaster in the Gulf). Rotary-wing aircraft are easiest to fly from a small ship, but more affordable options than the Peregrine may do. The expense and complication of a dedicated cockpit may not be justified if the RWUAS can be flown from a spacious working deck.
MHC-maternal-concept-2
This is just an outline concept. Loosely based on the existing commercial hull and OSV propulsion system, but with improved watertight compartmentation, fire fighting and damage control features.
Presence
One of the serious problems associated with the transition to unmanned mine hunting is the loss of presence offered by the conventional MCMV platform. A manned warship provides a measure of deterrence for adversaries and could be a platform for convening allies. The RN can no longer contribute MCMVs to NATO permanent mine countermeasures groups or exercises. The mothership would be able to act as a command/support vessel for the MCM group as well as offer advanced autonomous mine hunting capabilities that many navies do not plan to adopt in the near future.
Specialized motherships would act as force multipliers. The Bay-class vessel (or future MRSS) long deployed in Bahrain could return to its primary amphibious role. As well as mine warfare, OSVs would also have the flexibility to contribute to the wider RN undersea battle. In this secondary role, off-board systems deployed by these vessels can also perform anti-submarine warfare, seabed warfare and military data collection missions. In extreme cases, they could also be adapted for technical support on the surface, diving, recovery and underwater rescue work.
In theory, the RN has created a buffer for the MHC Block 2 budget by accelerating the decommissioning of its MCMVs. The NAO’s report on the MoD’s equipment plan, published in November 2022, said Block 2 had not yet been funded. A budget line should be established, subject to further development of the business case and then approval under the Defense Review, which is expected next year. Failure to fund MHC Block 2 would be a disaster and leave the RN with a severely limited MCM capability in line with a high-risk strategy of selling off conventional assets until the autonomous systems are validated and ready.
The construction of three motherships in the late 2020s to early 2030s is another major project for UK naval architects and shipbuilders and further justifies capacity expansion. However, it is not inconceivable that budget pressures will result in motherships being scrapped and cheap merchant ship conversions being replaced by newly built warships. The surface combat space is becoming increasingly dangerous, and the benefits of autonomous mine hunting will not be realized unless the systems can be deployed in contested seas.
Assuming MHC Block 2, including the mothership project, goes ahead, it will help restore mass and support the global reach of the RN Mine Action Force.