Starboard inboard profile of the New Corinth (L-21) class amphibious assault ship
New Corinth class amphibious
Amoskeag Iron Works
Wasp class amphibious assault
Landing helicopter deck
33,280 metric tons light
4 × Rolls-Royce MT30
16,668 km (9,000 nm)
2 × Willard Marine Sea Force
up to 60 armoured vehicles
900 officers & enlisted
1,100 officers & enlisted
2-000-3,000 officers & enlisted
Synergy Nucleus Combat
2 × MK 56 8-cell VLS
up to 40 fixed-wing,
Flight deck with 12°
The New Corinth (L-21) class is a type of general-purpose amphibious assault ship designed to a core requirement of transporting a full-strength Combined Arms Battalion and delivering its personnel, equipment and supplies over-the-horizon by means of landing craft operated from a stern docking well. The L-21 class has been designed for maximum flexibility to quickly adapt to a number of roles including light aircraft carrier, sea control ship and joint command ship, and can perform power projection, mine countermeasures, and humanitarian and other contingency missions on short notice. While being capable of operating independently in these roles it will most commonly be deployed as part of a larger task force (TF) that includes an amphibious transport dock with well deck, a fast combat replenishment ship, two or more escorting destroyers, and an attack submarine. To this end the L-21 class is equipped with flag facilities that provide command, control and communications to coordinate air and amphibious operations.
The L-21 class are of all-steel construction using corrosion-resistant super-austenitic stainless steel (SASS) in the hull and HY-80 steel in the superstructure, with HY-100 steel plate armouring the flight deck. Extensive sloping and use of non-magnetic steels and composite materials ensure a low radar cross-section (RCS), low infra-red (IR) signature and low magnetic field. The structure incorporates passive countermeasures including hull sides inclined at 10° to reduce radar cross-section, and epoxy-bonded Amitto carboxy-terminated butadiene nitrile (CTBN) anechoic tiles below the waterline to reduce acoustic signature. In common with all modern vessels of the Etoile Arcture Maritime Forces and Korrodosian Imperial Navy the L-21 class is pre-assembled in modular sections that are fitted out before final assembly.
The superstructure features a flush-deck with side island, a full-length axial flight deck with ramp (ski jump), aft deck jump jet landing area with jet blast collector, folding port and starboard deck-edge elevators, a full-length aviation hangar, ~4,000 lane metre capacity vehicle and cargo storage areas, berthing for c.2,000-3,000 troops, and a rear landing craft docking well. The latter features an inclined ramp above the waterline which is flooded by the ship's ballasting system allowing launch and recovery of landing craft through a large stern gate. Ramps and cargo/weapon elevators internally connect the hangar, vehicle and well deck, and staging areas for loading cargo on to landing craft. A material handling system transports palletised stores and equipment by continuous roller conveyors and monorails running the full length of the ship.
Both the combat information centre (CIC) and joint intelligence centre (JIC) for directing operations are located in armoured enclaves underneath the island for maximum protection. Medical facilities include an 18-bed intensive care ward, 4-bed isolation ward, 48-bed primary care ward, 8 operating rooms, X-ray and MRI scanner wards, two dental surgeries and a laboratory, with facilities for four casualty overflow wards with up to 400 beds by converting passenger berthing.
The propulsion system consists of four streamlined podded tractor propulsors of high hydrodynamic efficiency that locate machinery outside the hull saving volume that would otherwise be taken up by bulky inboard motors, fixed shafts and steering gear. Each pod is based around two contrarotating five-blade fixed-pitch propellers driven by a water-cooled, constant speed, transverse-flux electric motor and contrarotating reduction gear. These podded units can be operated at low power levels for high fuel economy, offer low noise and vibration for quieter operation, and have superior cavitation performance to deliver high cruise speeds with minimal wake.
The propeller blades are of a stainless steel highly skewed design and are bolted at the leading edge of the pod for easy repair or replacement. Forward and reverse thrust is provided by simple reversion of propeller rotational direction. The two inboard pods are fixed (non-azimuthing) while the two outboard pods pivot through 360° (azimuth) for rudderless steering on electric steering motors driven through a slip-ring assembly. The pods can be operated independently or together for improved manoeuvrability, and being externally mounted can be repaired or replaced without a lengthy and expensive drydock stay.
At low speeds, while berthing and during emergencies bow and stern thrusters provide steering control. The thrusters are of the reinforced tunnel type with four-blade fixed-pitch propellers and retracting butterfly-type doors that reduce underwater drag when not in use.
The generator plant is located above the waterline in a machinery house beneath infra-red suppressing side stacks on the superstructure to minimise ducting. The generator sets (gensets) are indirectly coupled to the pod propulsors by flexible space-efficient power linkages via transformers that match the voltage, frequency and power needs of the motors.
The prime movers are six gas turbine generators coupled by bearings to alternator drives, consisting of four aero-engine-derived Rolls-Royce MT30 twin-spool, high-pressure ratio gas turbine generators rated at 36 megawatts each, augmented by two GEC/Alstom SGT-100 Typhoon simple-cycle gas turbine generators rated at 5.7 megawatts to provide boost power. The total installed power is 142 megawatts, sufficient to propel the ship at 30 knots when steaming and supply all hotel services. To conserve fuel only two MT30 gas turbine alternators can provide a cruise speed of 20 knots, with all six engines being used when high speeds are required.
A full authority digital control (FADC) system monitors the engines and switchboards, generators and transformers controlled by an electronic power management system that divides and distributes the power flows between the propulsion system and hotel services. In case of a prime mover casualty the smaller SGT-100 gensets along with battery packs provide minimum power (10% of installed power) to propel the ship at a 10-knot emergency speed.
A partial-collective overpressure protection system provides a nuclear, biological and chemical (NBC) protected citadel in all interior spaces. The system monitors air quality and filters contaminants and toxic gasses from ship air with STANAG 4447 clean air filters integrated into the heating, ventilation and air conditioning (HVAC) plants. Automated damage control systems provide detection of fire, blast, smoke and flooding, and operate automatic flood control systems to maintain buoyancy and stability by closing watertight hatches and doors, and automated fire suppression systems with water mist sprinklers and clean agent extinguishers to control and extinguish fires.
The L-21 class is designed to operate a composite air wing that can include medium-size to large helicopters, V-22B Osprey tilrotors, and multi-role vertical/short takeoff and landing (VSTOL) aircraft. There are nine landing spots for rotary-wing aircraft, with a maximum of 23 metres of deck space for a rolling takeoff or landing of helos or V-22Bs, and 140 metres of deck provided for takeoff and landing runs by VSTOL aircraft. The flight deck terminates in a steep 12° angle ramp (ski jump) to provide additional lift for aircraft at full load.
The L-21 class vessel can carry 3-4 landing craft in its well deck for the over-the-horizon landing, recovery and redeployment of assault forces ashore. The well deck can either be flooded for float-on/float-out (FLO-FLO) of landing craft such as the Navantia LCM-1E or CNIM L-Cat 200 Multi Purpose Landing Catamara, or kept dry for fly-in/fly-out operation of air cushion landing craft such as Textron's Ship-to-Shore Connector Landing Craft Air Cushion (SSC LCAC-100).