MSS (Medium) – Offshore Construction Vessel
The previous example showed a basic offshore platform supply vessel conversion, taking a second hand UT705 as the starting point, or, buying a new vessel of similar size. What seem evident, is that whilst useful in some roles, the lack of aviation facilities and very low speeds severely limited its utility. By improving aviation facilities, the one thing that made it useful, space, was curtailed.
This leads to a conclusion that if we are intent on either converting a merchant vessel, or taking one as start point, it probably needs to be longer than 80m.
Vigor Industrial and Ulstein did collaborate to propose a X Bow based vessel for the US Coastguard, based on a specialist offshore design. The SX-151 was 100m long, 16.5m wide and with a top speed of 22 knots. A large hangar, mission bay and accommodation for over 120 personnel completed the design. It was perhaps a bit too radical for the USCG, who knows, but it didn’t progress.
Submarine tenders and other patrol vessels have also been proposed based on the SX 119 Field Support/Standby Vessel. The Field support/Standby role requires a multi-purpose design for rescue, oil recovery and towing so they tend to have higher speeds, excellent firefighting capability, flexible small craft handling, plenty of accommodation space and improved helicopter handling facilities. At 90m though, it is perhaps best suited to the MSS (Small) category than this. Ulstein have also developed the Discovery concept to further exploit the X Box concept.
The French are bringing into service a pair of vessel designs, four of the Kership Bâtiment multi-mission (B2M, “multi-mission ship”) and four of the Bâtiments de Soutien et d’Assistance Hauturiers (Offshore support and assistance vessels BSAH)
These ideas use a derivative of designs in use in the offshore industry, why is it that this shipping sector produces such a rich vein of innovative and low cost designs, three reasons I think?
Evolutionary Maturity; the basic superstructure forward design has remained relatively unchanged over many decades of demanding operation in extreme environments such as the North Sea. But what has changed over this period are the details. Refined in response to a demanding customer requirements, designers have responded over many iterations to the point where mature designs of every kind are available almost off the shelf. The supply chain and support ecosystem is equally mature, and this brings its own cost benefits.
Competition; a vibrant and healthy global market invariably has competition and this competition has created a fertile atmosphere for innovation. Because there are many experienced designers, shipyards and suppliers worldwide we can tap into this extremely competitive market and drive out benefits. This is in sharp contrast to naval shipbuilding which is generally sclerotic, relying on government subsidies and often failing to innovate at the same rate.
Innovation; although the fundamentals have remained fairly constant, sub systems have evolved at a rapid pace, benefitting from competition, steady demand and an overwhelming need to reduce operating costs by increasing utilisation. Wave piercing designs such as the Ulstein X Bow are genuine innovations that we can take advantage of, the innovation being essentially paid for by the oil and gas industry. Power, propulsion, boat handling, whole ship control systems and positioning technologies have all benefited from an atmosphere of commercially driven innovation.
In Part 1, I had a quick look at the larger offshore support vessels, such as those used for pipe-laying, seismic research, dive support, well intervention, field support and construction. These tend to be larger than straightforward PSV’s, between 100m and 180m. They are designed and built by organisations such as Havyard, Wärtsilä, Ulstein, Rolls Royce, STX, Vard and Damen
The reason I have elected to ‘go large’ is because of the trade off between payload space and aviation space,a larger vessel has more space, and it is space that really allows the concept to get going.
Given that they also contain a high degree of specialist equipment like saturation diving facilities, moon-pools, heavy lift subsea cranes and pipe laying equipment, a second hand vessel would include a great deal of equipment removal before any conversion could start. So, it is probably better to start with the basic design but build new.
The Starting Point
One such innovative vessel is the multi-purpose subsea Ulstein SX-121
Ulstein have designed and/or built six such designs over the last decade, costs have varied as there are obviously slight differences in final specification but the first few between 2006 and 2008 varied between 600 Million NOK and 900 Million NOK, approximately £50 million and £75 million. More recent orders in 2012 and 2013 averaged £65 million.
It would seem reasonable to set the baseline design and build cost at £65 million.
Specifications for the SX-121 Viking Poseidon include;
Dimensions; Length: 130m Beam: 25m Draught (max): 7.8m Speed (max): 14.5 knots Deadweight: 10,400 tonnes. Deck area 1,620 m3
Capacities: Fuel oil (MDO): 3280 m3 Fresh water: 990 m3 Technical fresh water: 519 m3 Ballast water: 7700 m3
Accommodation; hotel facilities for 106 persons, 6 state cabins with day and bedroom, 46 one bed cabins, 13 two bed cabins, 7 four bed cabins. All cabins with separate toilet and shower. Hospital and sick bay. Galley, scullery, mess (60 seats), day rooms, smoker’s day rooms, dry provisions, cooler, and two freezer rooms. Misc. conference rooms, 30 seat auditorium, offices and heli reception. Deck pantry, wardrooms, laundry, trim/games room. ROV Control room, online room, offline room, workshops. All facilities suitable for male and female crew.
Class Notation; DnV 1A1, SF, E0, DYNPOS-AUTRO, NAUT-OSV(A), CLEAN, OPP-F, CRANE, COMF-V(3), COMF-C(3),HELDK-SH, DK(+)
Power and Propulsion; Two tunnel thrusters, two swing-up azimuth thruster.DP3 positioning system. Diesel electric power and propulsion plant, Four main generator engines, each of MCR 2850 kW. Two main generator engines, each of MCR 1530 kW (1450 kWe / 1611 kVA) at 900 rpm. Exhaust catalyst for all six engines. Fuel consumption, harbour 5m3 per day, 12 knots 38 m3 per day.
Winches and Cranes; Knuckle boom shipboard / harbour crane, 10 tonnes at 20 m outreach. Two Folding cranes, 2850 kg at 10 m outreach. 250 tonne Active Heave Compensated Offshore Knuckle Jib Crane. Main winch SWL 200 tonnes single line, 3000 m net hook travel. Auxiliary Winch SWL 25 tonnes. Two combined windlass / mooring winches, One double mooring winch, pull 12.5 tonne, Two tugger winches, pull 12 tonne, Two mooring winches aft, pull 12,5 tonne
Navigation and Communications; S-band ARPA radar and X-band ARPA radar, Digital chart system ECDIS, Radio installation according to GMDSS – area A3, Satcom C, Fleet-77, Two V-Sat communication antennas Internal Communication ULSTEIN COM® common distribution of automatic telephone, data network and satellite TV antenna signal to all offices and cabins. Telephone system, separate PA, DECT.
Other; Two moon pools with well vented dampening chambers at all sides 8m x 8m and 5m x 5m. Two enclosed lifeboats with davits, each of 106 persons Life rafts: Four off 35 p. and two off 37 p., in davits. MOB boat (10 persons) with one-armed davit. Work class ROV hangar and launch/recovery equipment, module tower, 22m 14.7 tonnes capacity helideck, multi-skidding system for 100 tonne pallets, reinforced deck. Two Fresh water generators, 15 m3/24h, One Reverse osmosis plant, 25 m3/24h
From a systems and capacities perspective, this is a world away from the UT705 in example 1, accommodation is of the absolute highest standard, ships systems, power, positioning, likewise.
The innovative X Bow is said to provide a number of advantages…
- Higher transit speed in calm water due to low angles of entry and increased waterline length
- No bow flare, eliminating bow impact and slamming in foreship
- Lower pitch and heave accelerations due to foreship volume distribution and slender hull water line
- Reduced noise and vibration levels in foreship due to soft entry into waves
- Less spray
- Negligible occurrences of green water on bridge deck
- Working deck and deck equipment better protected due to hull extended to full beam in accommodation area
- Higher transit speed in head and following sea, giving reduced power consumption and/or higher fuel efficiency in waves and still water
Using the Viking Poseidon allows a start point to be established but there are a number of design features and systems we either don’t want, or want to change. The goal is still to minimise this amount of change, but in our context, am struggling to see the value of a well intervention tower.
Power and Propulsion
A top speed of 14.5 knots is still 3 or 4 knots short of what would be acceptable. The diesel power generation capacity is used for the high demand deck machinery so basic installed power may be enough. If not, a modest increase of a few knots may not increase costs a great deal. If we could go from 15 knots to 18 knots within the existing hull form, it would be extremely desirable to do so. Given one of the principles of MSS is to embrace the concept of experimentation, there may be room for testing new systems such as a DC Bus, permanent magnet thrusters, composite propellers, ducted propellers or rim thrusters. Another Ulstein design, the PX105, features a seawater injection system for exhaust gasses. Instead of routing the exhaust pipes up through the ship, leaving behind the bridge as per most designs, it is exited at sea level. This is done to provide an improved field of vision from the bridge but there are obvious tactical advantages as well.
No changes are likely to be needed to the basic hotel facilities. Capacity is enough for the ship’s crew and approximately 60-70 embarked personnel. The accommodation also includes a range of offices, briefing rooms and workshops, these may need some minor changes. Weapons and explosives storage would need to be incorporated and the hospital/clinic facilities improved and expanded. The spacious bridge area might also be modified to include an operations room. The ships boat and lifeboat deck would remain unchanged.
The helicopter landing pads seen on offshore construction vessels are used conventionally for crew changeovers whilst the ship is maintained on station. They are not usually used at night and tend to be limited in sea state operability. On HMS Protector, the helicopter deck was moved from the forward position to the cargo deck. A typical manufacture of such helicopter decks is the Dutch company, Bayards. Constructed of aluminium, they can also be fitted with various additional fixtures such as lighting and automated fire monitors. They have also joined forces with Barge Master to develop a stabilised flight deck.
Although this type of helideck does provide the ability to move personnel they are no use for cargo or vehicles, so if MSS is to exploit helicopters fully, it needs a more conventional solution. If it is to operate helicopters, as opposed to just provide a landing facility, it will also need a hangar and space for maintenance and stores, fuel, weapons and other supplies. The Viking Poseidon helideck should therefore be deleted from the design, another saving of cost and top weight.
The same applies for example 1, basic pintle mounted automatic weapons and man portable systems only.
Much like example 1, the principle changes would be to install a military communication system and basic radar/electro-optical sensor fit.
Like example 1, any drilling mud and bulk powder tanks, pumps and pipes can be removed and used for other purposes, also as example 1, most likely stores and fuel. This removes costs and complexity whilst providing for additional spares, and space for food, construction materials and other stores.
As can be seen from above, the changes at this point are minimal, the most significant changes would be those to the working area, above and below it. There would also be change in the ROV operating area in the main superstructure.
Moon Pool and ROV Hangar
Vessels working on deep offshore oil and gas facilities generally use tethered unmanned systems or Remotely Operated Vehicles, sometimes at extreme depths in excess of 2,000m. Most of the MCM/Survey unmanned systems are relatively compact in comparison to the large, heavy duty, ‘work class’ ROV’s commonly used in the offshore industry and tend to be autonomous or untethered.
Moon pools are designed to provide offshore vessel operators with maximum operating time in deep water and extreme sea states, time being very definitely money. Mines countermeasure norms might be inshore, shallower water and less extreme weather so the advantages of a moon pool might not be as evident and given that they take up considerable volume and add complexity and cost.
The rectangular block immediately to the stern of the bridge is for these work class ROV’s, one is launched through the moon pool and the other through the large vertical doors. The moon pool is 5mx5m and extends from A deck to the bottom of the ship. From A deck to the uppermost deck, D Deck, the space is used for ROV handling and storage. Together, this is a significant volume (shown with a blue breakout in the images below).
Moon pool damping tanks reduces wave motion so the ability to covertly deploy a UUV in high sea states does provide value to MSS, but not enough. Removing the moon pool, ROV handling systems and the ROV itself, removes a significant cost element.
Removing it also provides additional volume from the main deck and below, and above that, it can be removed completely, effectively, extending the cargo deck forward by approximately 7m.
There is also a large moon pool on the cargo deck, this too can be removed.
Deck Fixtures, Cranes and Winches
The deck is extremely robust with a high loading capacity, we might save some money by slightly reducing this but another big saving would be had by removing the skidding system. A skidding system is used to move extremely heavy modules and undersea construction equipment.
The large 250 tonne AHC crane weighs in excess of 350 tonnes without the below deck machinery. We don’t need it, so it can go. In order to resist the turning moment when using the crane at depths of hundreds or thousands of metres the vessel is fitted with a significant anti heeling system, tanks, pumps and control systems. Although a crane will be part of the ultimate design, it is unlikely to be of such high capacity, so the anti-heeling system could be scaled back as well.
The smaller crane will have value in the final design so can be left in place.
- Skidding System Video 1
- Skidding System Video 2
- AHC Crane Video 1
- Module Handling Video
- Load Handling Video
By removing the two moon pools, Work Class ROV facilities, heavy lift crane, winches, cable spools, helideck and module skidding system we have also removed a considerable cost, space, weight and power demand.
What we are left with, is in effect, a high specification PSV with excess power and crew facilities, but both excess power and accommodation is a good thing in context of MSS.
Leave the crane and helideck in place, and a simple RFA Diligence is probably there.
The cargo deck would be approximately 110m long by 25m wide (although the actual cargo space might be slightly smaller due to walkways and cargo rails. By removing the crane, main moon pool and associated equipment, the tween deck becomes vacant, approximately 5m high with the same approximate dimensions as the main cargo deck above.
Looking at images of the MV Sarah or Skandi Constructor, also SX-121 designs, they both have a mezzanine deck at the stern. The Normand Installer also shows a similar deck arrangement and the various seismic survey vessels have built up superstructures for the full deck length.
This provides a good indication of what can be done, simply extend that mezzanine deck forward to the superstructure and it results in a large flat open deck, underneath the main deck, and underneath that the tween deck, all of roughly the same dimensions except for the tween deck which is shorter due to propulsion machinery.
The tween deck would be 7m high and the main deck, slightly lower. The 7m tween deck would be high enough for all in service vehicles, in service construction plant on their transport trailers, a high cube container on a trailer and even a Merlin helicopter.
The main deck however, may need to hold double stacked containers, helicopters or small craft, 7m is not high enough, at least 10m is needed, with additional space for gantry cranes and handling equipment.
10m, conveniently, takes it to the same level as B Deck
Like Example 1, the main deck will need service connection panels, this is quite important to extending the functionality of the vessel. Air handling, lighting, fire detection and suppression systems would also be fitted.
And that is pretty much it in terms of deck configuration, mezzanine deck, 8-10m high enclosed main deck and 7m high tween deck, the latter two with service connectivity and all with appropriate tie down/lashing points.5
Aviation is an important component of most role sets but aviation facilities can be complex and inexpensive. Deck handling equipment, tie downs, night vision device compatible lighting/markings, landing aids, fuel handling and a number of other systems add to the cost. Modelling deck movement is also a complex task.
But it is important.
The mezzanine deck would therefore effectively form a large single flight deck, 110m long and 25m wide. It should also be capable of supporting a fully loaded Chinook. The mezzanine flight deck can also be used for vehicles, equipment, containers and modular systems.
A hangar is an essential item, it provides sheltered maintenance and storage space for helicopters and UAV’s. There are two basic options for a hangar, put one on the same level as the mezzanine deck or install a lift to the main deck and use that. Retractable hangars can be used when space is at a premium and a temporary Rubb shelter is a quick and cheap way of providing temporary covered space. A hangar on the same level as the mezzanine flight deck would reduce the usable length of the deck but a lift to the main deck would reduce its useable length.
The preferred option is to create a hangar on the same level as the mezzanine flight deck, sized to house two Merlin or Wildcat helicopters.
With blades folded, a Wildcat is approximately 14m long, 4m high and 3m wide. A Merlin, approximately 16m long, 5m high and 5m wide. With blades and tail unfolded, a Merlin is 23m long, 7m high and 19m wide. 31m long, 19m wide and 7m wide, a Chinook with rotors turning could fit. 20m long, 9m high and 10m wide and a folded CH-53 would fit. A V-22, when folded, requires 19m in length, 6m width and 6m height. Have a longer hangar, the flight deck becomes shorter but making the hangar 35m long allows the largest helicopter to fit yet still provides 65m unimpeded length for aircraft and UAV flight operations, comfortable for a Chinook, Merlin, CH-53 or V-22. Making the hangar the full width, 25m, also allows a rotors turning Chinook to fit. The hangar would therefore be 25m wide, 35m long and 8m high, a large space, but one that allows the largest helicopters in service to fit, and multiple smaller types. Now, making hangar doors that large may be an interesting challenge for manufacturers like Par Systems, Curtiss Wright, FHS, Calzoni and Aljo.
The top of the hangar is neatly in line with E Deck.
Forgive the crude diagram, but this is roughly what it would look like.
The Fort class replenishment vessels provide a good example of large hangars, if a single piece door is not practicable, splitting the door and making the hangar only accessible to helicopters with rotors folded may be the only solution available. Either way, the core objective is to have a large flexible hangar with an appropriate door mechanism. A small air operations control room will also be required.
On smaller vessels, like frigates and destroyers, in order to secure and move helicopters in higher sea states they need a variety of systems like the Claverham Deck Lock. The deck lock system requires the pilot to hover over a steel grid in order to deploy the locking ‘harpoon’. Once engaged the hydraulic actuator system, from Claverham, pulls the helicopter onto the deck, compressing the oleo leg in conjunction with negative thrust from the rotor. This system can secure the helicopter to the deck without needing any personnel to approach it, an important safety consideration. The deck lock grid is available from a number of manufacturers and widely used. Additional securing straps are often used and the deck lock released, it is a flexible system and because the actuator sits on the centre of rotation the helicopter can be easily manoeuvred into the most favourable position for subsequent takeoff. The pilot has immediate confirmation that the helicopter is secure and is not reliant on others. Once secured to the deck, a means of transporting to the hangar is required and these fall into two broad types, rail assist and tug. The MacTaggart Scott
This system can secure the helicopter to the deck without needing any personnel to approach it, an important safety consideration. The deck lock grid is available from a number of manufacturers and widely used. Additional securing straps are often used and the deck lock released, it is a flexible system and because the actuator sits on the centre of rotation the helicopter can be easily manoeuvred into the most favourable position for subsequent takeoff. The pilot has immediate confirmation that the helicopter is secure and is not reliant on others. Once secured to the deck, a means of transporting to the hangar is required and these fall into two broad types, rail assist and tug. The MacTaggart Scott TRIGON system is used by many operators and makes use of computer controlled steel wire ropes to secure and move helicopters. It uses a series of cables, with the three rail PRISM system specifically on Type 23 for Merlin, this
It uses a series of cables, with the three rail PRISM system specifically on Type 23 for Merlin, this document makes a good case for the all round superiority of TRIGON.
For large ships or small ships in calmer weather, an electric tractor unit is used to move the helicopter. The Royal Navy use the Indal MANTIS (formerly Douglas Equipment) battery powered handle for example.
Given the large size and designed in stability of the SX-121, it may be possible to dispense with these systems and just make use of tie down points and handlers.
In service in the Royal Navy are a number of heavy duty tie down straps, couplers and chains from Drallim. It would make sense to use the same.
An air weapons system will store and move air weapons from their stowage locations to weapon preparation areas prior transfer onto aircraft. Re-stowage of unused munitions is also part of system operation and a high degree of automation will reduce manual handling. A non-automated systems may also be appropriate, such as those from Varivane. Inside the hangar, an overhead gantry crane would need to be installed, perhaps similar to the design by Seward Wyon for the Type 45 Destroyer. Future rotary UAV’s may also be housed in the hangar. Helicopter Landing visual aids and lighting will be required, similar to those provided by AGI Limited including Homing Beacon Lighting, pilot eye line lights, visual approach lights, control systems and the Advanced Stabilised Glide Slope Indicator (ASGSI)
Fuel handling systems from Fluid Transfer Limited would complete the aviation facilities.
There is a big difference between providing a helipad for infrequent crew changes and the facilities required for safely operating helicopters and UAV’s from the ship, but it is an important function and one which require the appropriate specification.
Doors, Lifts, Access Ramps and Cranes
The ability to gain access to the decks, move vehicles, personnel and modules between them, and launch and recover small craft and unmanned systems is fundamental to the design.
The first thing to consider is how vehicles, modules and containers can be loaded onto the main and lower decks. Although it would increase flexibility, specifying a slewing quarter ramp at the stern of the main deck will add a great deal more cost that a simple side door and ramp. In the interests of economy, two side doors near the forward superstructure will allow easy access for vehicles and cargo from the quayside. Manufacturers include TTS, Macor, Seanet, Navalimpianti and Macgregor.
These are not constant tension and cannot be lowered to sea level which does preclude using them to load pontoons but that is an acceptable trade-off.
Once loaded onto the main deck, vehicles and stores will need to access the lower cargo deck. Options for the lower cargo deck boil down to a ramp or lift. A lift would require substantial machinery and likely to impinge a great deal on available space. ROR ships commonly use ramps, ether fixed or hoistable, to access lower decks.
A fixed ramp would need careful placement to accommodate vehicle and container handler turning circles but it is a very cheap option. A ramp usually takes up eight times the deck height, approximately 56m, at a single lane width of 4m. Taking access space and turning circles into account, this would be pretty much the full length of the lower deck.
Electrical or hydraulic ramp covers are another common piece of equipment that provides a watertight seal and allows the ramp area to be used on the upper deck area.
Being very generous with spacing to allow for tie down bars (instead of floor mounted twistlocks) there would be enough space for 30 TEU, 60 if double stacked. Using 4m as a lane metre width, again, generous, this works out at 240 lane metres, 60 Land Rovers or 20 MAN HS 6×6 trucks for example.
The lower deck would be used a simple storage area, no roof gantry crane and no service access points. A basic ventilation and fire detection/suppression system would complete the installation, perhaps with some under ramp pallet racking and fire doors to partition the area. The reason for this simplicity is two-fold, first cost, and second, the equipment contained on this deck will not be frequently moved.
The main cargo deck will be used mostly for modules, small craft and unmanned systems storage and movement.
There are three main challenges;
One; equipment may need to be moved during operations.
Two; equipment may need to be launched and recovered to the sea.
Three; modules may need services such as power, water, chilled water, compressed air and waste.
A deck grid system with multiple tie downs and retractable twistlocks will allow containers and lifting/storage cradles and frames to be secured against ship movements. Modules will generally be ISO container sized but small craft such as patrol boats, or unmanned systems, may fall outside these standardised dimensions. Vehicles can be lashed using strops and chains so lashing points must be distributed throughout the two deck areas.
If chains and strops are used to tie down containers from the top, the angle of the chain or strop is such that space is needed between containers to form the correct angle. This is not acceptable in a space constrained deck area so pop up locking risers can be fitted on the gridded layout that container twistlocks can be fixed into.
The NDM Cargo Securing System offers another alternative.
Moving boats, boat cradles, unmanned systems and modules can be carried out using fixed or mobile systems.
Container mobilsers, both manual and powered, can be used to rapidly move containers and lifting frames around the deck, they can also be used for loading and unloading to quayside. Not everything has to be powered and simple mechanical equipment still has utility, Recotech in Sweden make the 17 tonne capacity Wing Lift, Anga in Poland and Haacon in Germany also make similar equipment that can be used for limited moves and loading.
These manual systems can be slow and have a lower lift weight capacity but the advantage of not needing power is obvious,especially for the wheeled lifting jacks. They also allow containers to be loaded and unloaded from vehicles without any MHE but would be dangerous to use onboard in all but the most calm conditions.
Powered systems address a number of the problems with using manual systems.
The US DoD, as part of the wider Seabasing initiative, have also been investigation the problem of moving ISO container sized loads at sea. The Dense Pack Access Retrieval and Transit (DPART), omni-directional aircraft and vehicle platforms and Wheeled Container Lift and Manoeuvring System (C-LMS), for example.
Container mobilisers are similar in concept to the large shuttle and straddle carriers seen in container terminals. They are much easier to transport, can operate on moderate to poor surfaces and can be easily used indoors or where space is tight due to a low height and small footprint. For loading and unloading containers at a port, they are ideal. Combilift, ISO Loader, Meclift and Mobicon are notable manufacturers in this space, the latter selected by the US Navy for moving containers on and off LCS. The Mobicon straddle carrier uses two lifting frames that operate together rather than the rigid frame of the combilift. Mobicon also make a soft terrain version that because of the low container height are not vulnerable to tipping over should a soft patch or hole be encountered, they are more or less tip proof. The Meclift is intended for use on storage yards.
Any of these relatively cheap systems would be an ideal addition to MSS, relatively cheap, easy to operate, efficient, widely available and able to move containers around the ship, and on and off it.
A high level X-Y gantry crane system could also be fitted to access the full length and width of the main cargo deck. There are a number of manufacturers of suitable marine gantry cranes including Street, Stahl and Demag, to name only three. They can include multi-point lifting to prevent loads swinging and rotation devices for accurate placement.
The next challenge is launching and recovering small craft and unmanned systems to the sea, this requires access doors and a means of lowering and raising the loads into the sea. We can look at vessels like the Type 26 Frigate, US Navy Sea Fighter, Littoral Combat Ship and offshore support and construction vessels for examples. The main problem is handling large and cumbersome loads in high sea states and traversing the splash zone, safely.
For the Sea Fighter vessel, it was the UK’s BMT Nigel Gee that completed much of the development work. The mission bay system allowed fully loaded 16 tonne ISO container sized module to be moved from the flight deck to the cargo deck and then positioned to the appropriate location, including the stern launch ramp that could be used for 7m and 11m RHIB’s. Sea Fighter module handling was a clever system, but it was space constrained to only 12 mission modules, the load area was restricted by vertical supports and importantly, could not be used underway.
The Type 26 Frigate (or Global Combat Ship) mission bay will accommodate a range of small craft such as Inshore and Offshore Raiding Craft, Sea Boats (up to 12m long) and up to ten 20ft ISO containers. In addition to boats and containers, it can also accommodate a Merlin or even two Wildcat helicopters. The first image below is from a Babcock investor presentation and shows the mission bay being used to disembark a RHIB. The Type 26 GCS project team are also leading on a couple of projects that will benefit NATO standardisation, namely module interfaces and shock protection. A mock-up of the bay has been constructed at RNAS Yeovilton to allow experimentation, especially with regard to moving loads inside and outside the bay. DSTL and the US company, Weidlinger Associates, have created a solution to ensure containers remain secured after being subject to explosive shocks, testing has been carried out at an underwater range in Scotland with very encouraging results.
The crane system is rated at 15 tonnes and can extend to the side of the ship for loading and unloading. The crane itself is based on a model used for handling containers on North Sea oil rigs, again, experimentation has determined how it can be effectively modified to accommodate a range of movement and orientation of the ship. As can be seen from the secon images below, it has changed since the earlier design, the one on the right is the latest design. Marine Systems Technology and PAR Marine will supply the x-y crane used in the mission bay, the same manufacturer that provides the crane for the US Navy LCS Freedom class and DDG-1000.
Although not part of the programme, Rolls Royce/ODIM are doing a lot of work in this area, specifically, with robotic technology.
The NDM/Palfinger Container and Pallet Handling System is another that is available off the shelf.
MacTaggart Scott will supply mission bay side doors for the Type 26.
As the Mine Countermeasures and Hydrographic Capability (MHC) Programme progresses there may also be further work with the crane system to allow it to launch and recover autonomous unmanned systems.
Suffice it to say, they are templates on which to base any system for MSS.
It will also come as no surprise that the offshore industry has similar problems and a range of solutions
Small craft telescopic launch davits are available from a number of manufacturers such as Caley, Ferri, Rolls Royce, Red Rock, Navalimpanti, and Vestdavit. Some of these can lift up to 25 tonnes, accommodate large craft and operate safely in high sea states.
Vetsadavit have launched an integrated mission bay concept called the MissionEase System.
Although it cannot move containers at sea, one has to ask how much this is actually a requirement.
For launching unmanned and autonomous underwater vehicles many of their manufacturers also produce specialist Launch and Recovery Systems (LARS) that could be easily incorporated into the cargo deck. Whether the REMUS 600 will be part of the future Royal Navy suite of MCM equipment is not clear but Kongsberg make a containerised LARS that could be used through a side door.
A stern ramp is often used in vessels that require launch and recovery of rescue craft very quickly and this technology has also found its way into a number of naval and coastguard vessels. They are not especially easy to integrate because of their interactions with propulsion and other systems, and a potential loss of strength and stability, but it seems those issues are solvable with good design. The relative roll and pitch characteristics of both the main ship and small craft can be very different which leads to a high training requirement. BMT published a great paper on the subject a few years ago that details the pro and cons of each approach. Most systems automatically adjust to hull contours but for larger catamaran workboats, special adapters can also be used.
A few videos and images, the LCS one does not look like fun to me!
Completing this section would be a 10×10 ft cargo lift between the lower and main decks and helicopter hangar. This would allow the rapid movement of pallets, trolleys and 8ft containers.
Hopefully, this section has shown that all the systems that would make MSS into a functional and useful vessel are available off the shelf, there are no wheels being invented or re-invented here.
As with the previous example, we should compare this one with each of the potentials roles and see how things pan out.
Humanitarian Assistance Disaster Response; MSS (Medium) would provide an excellent platform for HADR missions. The lower deck would ordinarily be used for vehicles, pallets and containers, no need to move until after arrival in the mission area. As described above, 60 pickup type vehicles or 20 standard 6×6 cargo trucks and anything in between like engineering plant and logistics vehicles. As a minimum, these could be substituted for 30 TEU, 6o TEU if double stacked. The air operations capability would support helicopter lift and unmanned ISTAR systems like a Scan Eagle or any of the off the shelf mapping systems widely available. At maximum capacity, and leaving no room for boats or modules but taking into account turning circles, RORO ramps and other fittings, the main deck has approximately 400 lane metres, approximately 30 6×6 trucks, each with a 20ft ISO container. A Mexeflote could be carried disassembled on the main deck and unloaded using the telescopic gantry systems or deck crane. There would be an argument to design in some ‘open deck’ space to make this easier. If not a Mexeflote, the space and lifting capacity of the handling system would allow landing craft to be embarked. With excess accommodation for approximately 60 personnel, the response team would be sufficient. More could be embarked if using modular accommodation units.
Training and Defence Engagement; a lot of space means a lot of training opportunities and unlike MSS (Small) the aviation facilities would also allow that be included in the training matrix.
Maritime and Littoral Security; with a combination of multiple helicopters, UAV’s, RHIBS and larger patrol craft, and even hovercraft, MSS Medium would be a very good ‘mothership’ 60 additional personnel, again, would be easily carried without reverting to modules and the ample space on the main deck would allow any small craft to be hangered and maintained for long periods. There would also be ample space for prisoner facilities.
Medical Support; Like MSS Small, I remain to be convinced that the main deck could be used for a Role 3 hospital facility without a permanent conversion but if that were accepted, it would be an excellent platform, whilst still retaining some capacity for the other roles.
Salvage, Repair and Fire Fighting; by retaining the large crane, using a modular workshop facility (similar to those used in the land environment) and modular diver support system, it would provide excellent salvage/repair and submarine tender facilities. There would be an argument that a larger crane and some open deck retention would make for a better capability.
Experimentation and Systems Development; I think it would be taken for granted, that the large open deck, crane, services connectivity and additional accommodation would provide a very good platform for experimentation and systems development, especially emerging unmanned surface vessels and aerial vehicles.
MCM and Survey; same arguments for MSS Small, but obviously, it would be able to carry considerably more off-board platforms, host emerging unmanned aerial vehicles in the MCM role, and carry out the MCM command function for larger and/or enduring deployments. Its excess space and excellent handling facilities, coupled with accommodation for many personnel, would make an interesting system, if unmanned systems mature as expected. For survey, again, the development of off-board systems will be linked to suitability but for basic instruments like bottom profilers and CDT’s, the handling systems should be more than enough, although some open space at the stern and a small A frame might be best suited.
Ship to Shore Logistics Support; in addition to carrying supplies, vehicles, personnel and engineering plant for port repair, another suitable task would be that of providing a ship to shore fuel transfer capability. It would also be able to carry a great deal of supplies in their own right
Special Forces and Intelligence Support; whether carrying raiding craft, small landing craft, vehicles, personnel or even a swimmer delivery vehicle, the carrying capacity and flexibility afforded by the main deck space would provide obvious utility for special forces. Containerised signals equipment could also be used to provide an additional and innocuous capability for gathering intelligence. Unmanned systems would also be potential carries and the aviation capacity would provide another valuable enhancement.
Submarine Rescue; ironically, the lack of open deck space might make it impossible to host the NATO Submarine Rescue System. The acid test is whether the Launch and Recovery System (LARS) could be fitted to the flight deck and operated from there.
MSS (Medium) is basically more of MSS (Small), the additional accommodation, aviation facilities and covered main deck, with its flexible handling and launch/recovery systems really do make the difference in many of the potential roles.
It is difficult to estimate costs because like much of this, it would be guesswork, if we start with £65 million starting price and then remove the moon pools, ROV, ROV handling, skidding system, active heave compensated crane and fluid handling, how much would it be reduced by?
We know the PX 121 is going for £20 million to £30 million so that sets the hard stop point, perhaps if we guessed at a reduction of £20 million we would not be far off. If the military comms, additional sensors, aviation facilities and all the cargo deck systems came in at £20-30 million we would not be far off our original target price of £75 million.
There may be some discussion on the stern arrangements, whether a boat launching ramp is needed, or if some open space would be desirable to a fully enclosed area for example.
As with example 1, will leave you to decide whether it would be money well spent, or whether there is actually a requirement.