It has emerged that the RN plans to acquire up to three ‘survivable, non-complex warships’ designed from the outset as motherships for autonomous mine hunting boats.
Non-complex warships
The need for four Offshore Support Vessels (OSV) or mother ships to support the future Mine Hunting Capability (MHC) has been known for some time. Although included in the National Shipbuilding Strategy, it was unclear whether the three final ships would be ‘light’ merchant ships, similar to RFA Stirling Castle, heavily modified merchant ships or newbuilds. Assuming funding is approved, it is clear that the RN wants to build warships to a bespoke design, which will fly the White Ensign and be ‘HMS’, potentially continuing the Castle class nomenclature.
The RN wants the motherships to be built to higher standards of damage control and survivability than would result from the conversion of a merchant ship. It can be assumed that these ships will have some self-defense capability, military communications and sensors more advanced than just navigational radar. The level of self-defense capability has yet to be defined, but could potentially include more than just crew-served light weapons. It is becoming increasingly clear that every Navy ship on the drawing board today must have powerful counter-UAV/UAS capabilities at its core.
MHC block 2
RFA Stirling Castle has carried out some initial testing, but its limitations in its intended role are already clear. Her purchase was very good value for money and provides an excellent test bed for MHC Block 1, the pathfinder program to bring autonomous mine hunting into RN service. (More details on progress with Block 1 in a future article). MHC Block 2 will be significantly more ambitious and will require motherships with sufficient capacity.
RFA Stirling Castle lacks a dedicated launch and recovery system (LARS), apart from a crane and the 600 meter long2 the working deck is not big enough. Deck space of at least 1000m2 is required to accommodate the USVs, UUVs, portable operations center, and support kit that comprise a mission module. To achieve an equivalent (and ideally better) effect than existing MCMVs in a mine warfare operation covering a large area, multiple USVs must be deployed. This requires a large deck with enough space for the toolbox.
Future USVs may grow larger than the 12-15 meter boats of the first generation and the motherships will need LARS large enough to accommodate them. Robust LARS that can handle unmanned boats of several tonnes in challenging sea conditions and strong winds are specialist pieces of equipment and there are several companies already offering advanced solutions. A stern ramp can also provide an alternative launch/recovery option depending on weather conditions and vessel type.
Early experience with autonomous mine hunting with RNMB Harrier operating in the Gulf from RFA Cardigan Bay and from shore has highlighted the need for greater situational awareness. For MHC Block 2, the RN is interested in medium-sized UAS to provide basic ISR capabilities. This could be provided by the Peregrine RWUAS (which will commence its first operations in RN service very soon, flying from HMS Lancaster in the Gulf). Rotary-wing aircraft are easiest to operate from a small ship, but cheaper options than Peregrine may suffice. The costs and complications of a dedicated cockpit may not be justified if the RWUAS can fly from the spacious working deck.
MHC-Mothership-concept-2
This is just a draft concept. Loosely based on an existing commercial OSV hull and propulsion system, but with improved watertight subdivision, fire suppression and damage mitigation functions.
Presence
One of the serious issues surrounding the move to unmanned mine hunting is the loss of presence that a conventional MCMV platform provides. A manned warship provides a degree of deterrence to adversaries and could be a platform for allies. The RN can no longer contribute MCMVs to NATO standing mine countermeasures groups or exercises. The mothership could act as a command/support vessel for an MCM group and provide the advanced autonomous mine hunting capabilities that many navies do not plan to adopt in the near future.
The dedicated motherships would act as force multipliers. The Bay-class ship (or future MRSS), which is on long-term deployment in Bahrain, could return to its primary amphibious role. In addition to mine warfare, the OSVs would also have the flexibility to contribute to the RN’s broader undersea fight. In this secondary role, outboard systems deployed by these ships could also perform anti-submarine warfare, seabed warfare and military data collection missions. In extremis they can also be adapted for water technical support, diving, salvage and underwater rescue work.
In theory, the RN has created budget space for MHC Block 2 by accelerating the dismantling of its MCMVs. The NAO report on Defense’s equipment plan, published in November 2022, stated that Block 2 had not yet been funded. A budget line should be established, provided the business case is further developed and then approved during the defense review expected next year. Failure to fund MHC Block 2 would be a disaster, leaving the RN with a greatly reduced MCM capacity, following the risky strategy of divesting conventional assets before autonomous systems are proven and ready.
The construction of the three motherships in the late 1920s to early 1930s is another important project for British naval architects and shipbuilders and further justifies the expansion of capacity. However, it is not inconceivable that budget pressures will lead to the motherships falling out of reach and cheap merchant ships being replaced by newly built warships. The surface battlespace is becoming increasingly dangerous and the benefits of autonomous mine hunting will not be realized if the systems cannot be deployed in contested seas.
Provided MHC Block 2, including the mothership project, proceeds, it will help restore mass and support the global reach of the RN mine warfare forces.