The recently decommissioned USS Freedom LCS. Navy hopes to retire nine Freedom-class LCS hulls sooner (USN file image)

Posted on April 6, 2022 at 5:27 p.m. by


[By Lt. Joseph O’Connell]

With all the negative publicity surrounding the Navy’s Littoral Combat Ship (LCS) program, it would seem obvious that the Coast Guard has no interest in acquiring the LCS as a second-hand item. However, with the recent publication of “In Dire Need: Why the Coast Guard Needs the LCS”, new interest in acquiring problematic naval platforms may be growing and deserves to be judged on its merits. The central thesis proposes that the US Coast Guard acquire decommissioned LCS from the US Navy, remove the installed Diesel Engine and Gas Turbine (CODAG) plant, and install a direct drive diesel. While the proposal is noticeably light on the details of the propulsion layout (it is unclear whether the new layout would have a waterjet diesel or use a split/combine gear arrangement), it is s builds on historical Coast Guard precedents for accepting former Navy vessels and converting CODAG installations to diesel direct drives. The concept deserves an analytical look to determine if the main finding, that acquiring recently decommissioned LCS instead of commissioning new Offshore Patrol Vessels (OPCs) has the potential to save the scarce dollars of the Coast Guard, is true. To do this, a rough exploration of what this program would accomplish and at what cost should be compared to OPC designs and costs.

The LCS: designed for speed

One of the riding requirements for acquiring the LCS was “sprint” speeds in excess of 40 knots. Such speeds effectively ruled out traditional propellers as prime movers with waterjet systems taking their place. The Coast Guard does not and has not operated large vessels with waterjet thrusters, and significant propulsion inefficiencies exist when using these thrusters at lower speeds (Figure 1). Due to the physics governing water jets, they are rarely used in vessels that normally operate at less than 30 knots. While repowering itself may be a cost-effective way to clear newly created cutters of an expensive gear problem, it does not solve the propulsion problem of low-speed waterjet operation.

Figure 1: Achievable propulsion coefficient for thrusters applicable to high-speed monohulls

For the sake of argument, we can assume that the Coast Guard would re-engine the LCS with an engine comparable to the two 7,280 KW fairbanks diesels planned for the OPC, with a total combined braking power (BHP) of 19,520. Using publicly available data points on the LCS speed power curve and understanding its cubic nature, we see that this would yield a disappointing 15-20 knots at broadside speed. And while 15 to 20 knots may be acceptable for Coast Guard operations, this does not match the 22+ knots promised by the OPC or the fuel efficiency and lower operating costs of driving stroll designed by the OPC. Due to the waterjet propulsion system, an additional operating cost for the Coast Guard LCS would be fuel and maintenance. Waterjets are terribly inefficient at low to medium speeds and would consume 20-50% more fuel than OPC at similar speeds.

Additionally, as evidenced by the National Security Cutting Speed ​​Operating Profile, the Coast Guard rarely uses high speeds, with the majority of UW time spent loitering after a breakdown, primarily holding position with conditions. light load on the plant. This has caused many Main Diesel Engine (MDE) maintenance issues for the WMSL fleet, and this would likely be the case if LCS were also adopted. The OPC was designed with this operational speed profile in mind and has a planned low-speed electric loiter drive. This drive will reduce low load conditions that degrade engine life and capacity. Additionally, the low-speed drive lengthens cutter endurance by limiting fuel consumption, often a reason cutters return to port for brief stops for fuel (BSF). Given the slower speed and higher fuel consumption, the LCS would be significantly outperformed by an OPC in the majority of Coast Guard mission sets. Without the loiter drive, the Coast Guard LCS would have high-speed diesel engines powering four water jets, exposing both systems to increased degradation due to low operating speeds.

Ship handlers should be warned

Not only would these franken-cutters be fuel-efficient, slower and more expensive to maintain, but they would also be much harder to maneuver. Without the traditional rudder control surface, the LCS uses moving water jets to provide both propulsion and steering – a layout Coast Guard watchkeeping officers are unfamiliar with. With a new lower speed main engine powering the water jet, it is safe to assume that the water volume flow rate would drop, which would decrease the efficiency of the jets for maneuvering. This increases the potential for catastrophic collisions, unscheduled maintenance periods and high repair costs that familiar and more reliable steering systems mitigate.

A final unresolved concern is the aluminum hull of the Independence variant, originally adopted to lighten the ship to make sprint speeds more achievable. Aluminum is unsavory for a potential naval combatant due to its low melting point. The ASU Belknap the fire shows why shipbuilders generally prefer to avoid aluminum. Given the Coast Guard’s growing role in great power competition and the risks associated with naval operations in blue waters, an aluminum-hulled vessel, powered by diesels driving a water jet, seems about as little appetizing than a cutter that could be built.

The true cost of reengineering

The only remaining argument in favor of the adoption of LCS by the Coast Guard is its relative cost to the OPC. Current projections indicate that an OPC will cost an average of $411 million per hull. By taking a holistic analysis, including expected operating costs and operational efficiency, we can make a clear assessment of OPC disposal in favor of LCS recycling. At first glance, it seems like it would be more cost effective to re-engine an existing hull than to build one from scratch. On average, re-engining a cutter would require a long period of dry docking, around 12+ months per hull. This estimate is based on current re-engine times for Legacy Famous-class cutters undergoing a power grid upgrade, with new installations of ship service diesel generators (SSDG) taking around seven months. Given the bureaucratic processes of transferring control of a vessel from the Navy to the Coast Guard, compounded by the availability of replacement engines and gears, we can safely assume that the first OPC, if not the first, will have been delivered when an LCS is operational. Since there is no delivery time advantage for either platform, but speed, maneuverability, maintainability, hull age at delivery and advantages significant endurance ratings for OPC, the cost savings must be substantial to consider LCS worth adopting.

Although it is difficult to accurately predict the cost of re-engining and outfitting a 3,500 ton fighter, we can estimate a range that may be useful for comparison with a new build. Using a standard maintenance drydock for the WMSL – a similarly sized vessel – as a benchmark, we can set a lower threshold of $1 million per month, with an estimated availability of around 12 months, and the engines themselves. -themselves costing over $1 million each. Assuming gear replacement equipment will cost just as much, we arrive at an optimistic figure of $20 million and a more conservative figure of $40 million per hull. Either way, either estimate represents less than 10% of the cost of a new OPC, supporting the original assumption that retooling an LCS to take the place of a OPC would be more affordable. The second major factor in the cost of hull machinery and electricity (HM&E) is the age of the hull, as ships age they become relatively more expensive to maintain, given that the first LCS was established in 2005, commissioned in 2008, the Coast Guard would pay more than $40 million per hull for a vessel over 15 years old that would be expensive to operate, difficult to maneuver, slower and less reliable than anticipated OPCs.

After a brief look at the actual costs to the Coast Guard to adopt LCS, it becomes painfully clear that they would be woefully insufficient to replace the planned OPCs. While this route would be significantly cheaper in the immediate future, it would be a Faustian bargain, requiring the Coast Guard to operate expensive and inefficient cutters. Such cutters would only serve to weaken the Coast Guard’s medium endurance fleet. With the changing geopolitics of today’s world, the US Coast Guard cannot afford to trade well-designed, affordable cutters for recycled marine hulls.

The opinions expressed in this article are those of the author alone and do not represent the positions of any agency or institution.

Lt. Joey O’Connell served aboard two Coast Guard cutters as an engineer. He is currently a Medium Endurance Cutter (MEC) Port Engineer, planning and overseeing depot-level maintenance on MEC’s ​​aging fleet. He holds a bachelor’s degree in mechanical engineering from the US Coast Guard Academy and two master’s degrees, one in naval architecture and the other in mechanical engineering from the Massachusetts Institute of Technology.

This article appears courtesy of CIMSEC and can be found in its original form here.

The views expressed here are those of the author and not necessarily those of The Maritime Executive.