US Coast Guard USCGC Pickering cutter to feature Kongsberg Maritime's Promas propulsion system.

On April 10, 2024, Kongsberg Maritime was selected by the American shipbuilder Austal USA to supply their Promas propulsion systems for the fifth ship in the United States Coast Guard's new Offshore Patrol Cutter (OPC) program. The vessel, named the US Coast Guard Cutter (USCGC) Pickering, marks the first in this class to be built by Austal USA in Mobile, Alabama.
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The first Heritage-class ship, the USCGC Argus (WMSM-915), was launched on October 27, 2023, by Eastern Shipbuilding. (Picture source: Eastern Shipbuilding Group)

Under the terms of the contract, Kongsberg Maritime will provide not only the twin Promas propulsion systems but also steering gear, rudders, fin stabilizers, and tunnel thrusters. The Promas system integrates the propeller, hub cap, rudder bulb, and rudder into a single hydrodynamically efficient unit. The system is designed to channel the water flow from the propeller through a hubcap onto a rudder bulb, effectively using the swirling energy typically lost in the slipstream to generate additional forward thrust.

This configuration not only streamlines water flow and minimizes drag but also enhances the propulsive efficiency of the vessel. The rudder features a twisted leading edge that reduces the risk of cavitation and optimizes propulsion, and it can be fitted with an extension flap to further improve maneuverability depending on the vessel's needs.

The Promas system is designed for various vessel configurations, including conventional single- and twin-screw ships, naval and special purpose vessels, and those requiring ice class specifications. It is also available for new builds and as an upgrade for existing vessels, with options for four and five-bladed propellers and a nozzle to enhance thrust and fuel efficiency. Its design facilitates easier installation and compliance with actual and future emissions regulations.

The system improves propulsive efficiency by approximately 6-8%, which corresponds to a reduction in fuel consumption and emissions, leading to cost savings over time, as highlighted by Björn ten Eicken, Vice President – Naval at Kongsberg Maritime. This efficiency is particularly valuable for the long-duration missions anticipated for the OPC program, which aims to replace the US Coast Guard's medium endurance cutters while enhancing the fleet's long-term offshore capabilities to meet both current and future mission requirements.

The US Coast Guard plans to acquire a total of 25 Heritage-class cutters through the Offshore Patrol Cutter (OPC) program, initiated as part of the US Coast Guard's Integrated Deepwater System Program to replace older medium endurance cutters with newer, technologically updated vessels. Intended to bridge capabilities between the larger national security cutters and the smaller fast response cutters, the OPC program has experienced several challenges, including budget constraints and delays in design finalization. Finally, in September 2016, Eastern Shipbuilding was awarded the contract to construct the first Offshore Patrol Cutter, an important step in the procurement process.

These Heritage-class cutters, displacing 4,520 tons and having a length of 110 meters, will support a range of US Coast Guard's missions such as maritime law enforcement, search and rescue, and national defense. Powered by two MAN engines that drive controllable pitch propellers, these new vessels are expected to achieve a top speed of 24.5 knots and a maximum cruising range of 10,200 nautical miles at 14 knots. They will carry a crew of 126 people, have an endurance of 60 days, and are equipped with facilities to support MH-60 or MH-65 helicopters.

In terms of armaments, these cutters are equipped with modern armaments, including an MK 110 57 mm gun, a BAE Systems Mk 38 Mod 3 25 mm gun with a 7.62 mm co-axial gun, and several M2 Browning .50 caliber machine guns, enhancing their capability to address various maritime threats. Additionally, the design allows for the addition of further weapons and systems if needed for operations in more hostile environments.

The Promas system improves propulsive efficiency by approximately 6-8%, which corresponds to a reduction in fuel consumption and emissions, leading to cost savings over time. (Picture source: Kongsberg Maritime)