OPC “Placemat”

Criticism of the Littoral Combat Ship Program continues unabated, with additional fuel thrown on the fire by a series of machinery casualties. With the new administration indicating they will take a look at existing programs, looking for savings, at the same time they are seeking a much larger fleet, it seems likely the LCS program will get a second look. After initially choosing to base the new frigate, on one of the LCS designs, it now appears the Navy is willing to look at other hulls.

Perhaps the Offshore Patrol Cutter (OPC) might be considered.

• It is larger than either of the two LCS designs.
• It cost less–about half as much.
• It is built to ABS Naval Vessel Rules.
• It is likely that anything that can be added to the LCS can be added to the OPC.
• It has two to three times the range and endurance.
• It can operate in heavier seas.
• It has 25% more generator capacity than the Freedom class LCS (unable to find info on the Independence class.)
• It’s more spacious interior makes it easier to maintain.
• It’s engineering plant is simpler and probably more reliable.
• It’s efficient hybrid diesel/electric propulsion system permits much long loiter times.
• It’s propulsion system is probably inherently quieter than the water jets used on the LCSs–an advantage for ASW.
• It’s only real disadvantage is lower speed and that can be mitigated if necessary.

The GAO has recommended a two year hiatus.

LITTORAL COMBAT SHIP AND FRIGATE
Slowing Planned Frigate Acquisition Would Enable
Better-Informed Decisions

What GAO Found
The Navy’s vision for the Littoral Combat Ship (LCS) program has evolved significantly over the last 15 years, reflecting degradations of the underlying business case. Initial plans to experiment with two different prototype ships adapted from commercial designs were abandoned early in favor of an acquisition approach that committed to  numerous ships before proving their capabilities. Cost, schedule, and capability expectations have eroded over time, as shown in the table below. More recently, the Navy attributed a series of engineering casualties on delivered LCS to shortfalls in crew training, seaframe design, and construction quality.

Additionally there is Congressional opposition.

Sen. John McCain (R-Ariz.) plans to hold hearings on the Navy’s frigate program amidst calls to open the competition to more domestic and foreign designs.

“The frigate acquisition strategy should be revised to increase requirements to include convoy air defense, greater missile capability and longer endurance,” (emphasis applied–Chuck)

The high speed requirement has resulted in ships with water jet propulsion systems that are inappropriate for ASW escorts, ships that have relatively short range and poor seakeeping. These characteristics make the ships less capable of independent operation and helicopter launch and recovery in rough weather, particularly for the mono-hull Freedom class. The Aluminum hull, trimaran Independence class has great aviation facilities and a bit better range and cruise speed, but its aluminum hull raises survivability issues.

The Navy now sees that they need a frigate and they chose to meet this requirement using a modified LCS, but the LCS has notable weaknesses that mean it may not have been the best choice. In addition now it seems they see a need for local area airdefense that was not initially considered  According to a recent DefenseNews report, 

“A study group called the Requirement Evaluation Team (RET) has been formed to examine how to add a local air defense capability to the frigates to protect Combat Logistics Force ships – the supply and support ships that bring fuel, ammunition, spare parts and food to warships at sea. The frigate design as currently envisioned is armed with anti-missile and anti-aircraft missiles, but only to protect itself.

“The goal, according to a draft document, is – at a minimum – to double the loadout of Evolved Sea Sparrow Missiles (ESSM) Block 2 from 8 to 16 or incorporate a Mark 41 vertical launch system with at least 8 Standard SM-2 missiles. The SM-2 is one of the primary anti-air weapons carried by the fleet’s Aegis destroyers and cruises.

“…We’re looking at further increases to survivability, and we’re looking at endurance, pushing the envelope. And as always we’re going to balance that against technical risk and cost.”

Additionally it now appears they may be more expensive than previously reported.

A frigate based on the Offshore Patrol Cutter could be a cheaper and, in many respects, superior alternative.

WHY DO WE NEED FRIGATES AND WHAT SHOULD BE ITS CHARACTERISTICS?

A nation chooses to build frigates rather than destroyers because it needs numbers. They choose to build a frigate rather than smaller corvettes because they want longer range and better sea-keeping.

If you are looking for numbers, it make no sense to build a frigate that cost 75% that of a Burke Class DDG and provides only 50% of the capability. We can’t build enough of them without impacting other programs. The Europeans are making ships like this, but they are not intended to complement destroyers like the Burke class, they are intended to replace them. They are the premier warships of their respective navies.

In navies that actually have destroyers, frigates tend to be around 4,000 tons full load, The Chinese Type 054A are reportedly 4053 tons full load and the Russian Admiral Grigorovich class 4,035 tons full load. South Korea’s Incheon batch II class frigates will be 3,592 tons full load. Japan has recently announced that they will be building two 3,000 ton frigates a year instead a single 5,100 ton destroyer annually (whether this is full load displacement or something less is not clear). The very numerous Oliver Hazard Perry (FG-7) Class were about 4,200 tons full load. While no final official figure has been published, the Offshore Patrol Cutters are also expected to be about 4,000 tons. Any significant modification is likely to make them displace as much or more than the Perry class. 4,000 tons is already larger than any US Navy destroyer of World War II and would have been considered a light cruiser in WWI

Small warships are not the answer for open ocean escort either. When escorting large ships, a small escort may be unable to keep up, regardless of its nominal maximum speed. I had access to the USCGC Duane’s war diary and was a bit surprised to learn that there were instances when, because of weather, the 2,300 ton, 20 knot cutter was out running smaller 1,300 ton World War One design destroyers that were nominally capable of 35 knots. Smaller ships also tend not to have sufficient range for more than theater coastal operations.

WHY NOT BASE A FRIGATE ON AN LCS DESIGN?:

In some respects the LCS look appropriate for conversion to frigates. They are not too small, but are notably cheaper than the Burke class DDGs, and their crews are much smaller than the more than 300 member crew of Burke class destroyers. They are a little smaller than most modern frigates, 3,500 tons for the Freedom (LCS-1) and 3,100 tons for the Independence (LCS-2) class. Unfortunately, the original concept of a very high speed, shallow draft, forward based, modular vessel specializing in Littoral combat has resulted in compromises that make them a poor basis for an Open Ocean Escort Vessel.

The high speed requirement has resulted in crowded machinery spaces that make access for underway repair difficult. They have short legs, likely generate a lot of noise, and are reportedly weight critical.

PRICE COMPARISON:

The last contract for two LCS ran about $550M each. The award to Eastern for construction of up to nine Offshore Patrol Cutters (OPC) if all options are exercised is $2.38B. That is only $264.4M per ship. Additionally the Coast Guard contract includes a warranty that requires the builder to fix construction errors while the Navy contracts require the Navy to pay for correction of construction faults.

“Upgrading” the existing LCS designs to fill the frigate mission may exacerbate their existing problem with range. A post from Warisboring.com notes:

“The frigate will also be slower than the standard LCS and have shorter range. (emphasis applied–Chuck) All in all, the frigate version “was the least capable option considered” by the Navy out of several alternatives, the report stated.”

It goes on to note,

“But it was the cheapest and quickest to produce … which is the whole point. The Navy is desperate to get ships under construction as older vessels age out. The sailing branch currently fields 274 deployable warships — well under its goal of 300.”

The root of the problem is the LCS’ lightweight building materials — aluminum—and its size and unorthodox shape. In other words, it simply and physically cannot ever be as survivable as an older FFG 7, or Oliver Hazard Perry-class frigate.

The GAO notes:

A minor modified LCS could not be modified to the level of vulnerability resistance of the FFG 7 due to LCS weight and design constraints that would prevent adding more physical structure. For example, Navy task force officials told us that approximately 200 tons of additional weight in steel would need to be accommodated in the LCS seaframe designs if the Navy wanted to upgrade it from commercial build standards to more robust, Navy-like specifications like those used for FFG 7. Task force officials told us that this weight increase would have required a major modification to the LCS design or a new ship design.

PAYLOADS vs PLATFORMS:

When Admiral Greenart wrote his seminal article, “Payloads over Platforms: Charting a New Course,” published in the July 2012 US Naval institute Proceedings, he said, “We need to move from “luxury-car” platforms–with their built-in capabilities–toward dependable “trucks” that can handle a changing payload selection.”

The LCS are not really luxury cars, but they are sports cars–high strung, expensive to maintain, with outstanding capabilities over a limited range of activities but perhaps impractical for many purposes. The greater the payload you attempt to stuff into them, the less appropriate they appear to be.

Certainly not a sports car, the OPC, by contrast, is an “F-150 pickup,” simple, practical, easy to maintain, with a spacious interior, and fast enough for most purposes, and with optional horsepower upgrades possible if you really want it faster. Recently it seems the required payload is being increased to include 16 anti-ship cruise missiles (ASCM) and either 16 ESSM or an 8 cell Mk41 to provide a degree of AAW protection for ships escorted.

OTHER THAN BEING CHEAPER, DOES THE OPC HAVE ANY ADVANTAGES?: 

Actually the Offshore Patrol Cutter enjoys several advantages:

Range: The range we see quoted for the OPC, 10,200 nmi is far more than the 3,500 and 4,300 given for the Freedom and Independence classes respectively. The ranges for the LCS classes is quoted for 18 knots while the range for the OPC is for 14 knots so the range difference is not as great as it may first appear, but even at 18 knots it is likely the OPC will have a range of over 6,500 nmi. That means the OPC will not have to break off operations to refuel as frequently as its LCS counterparts.

Endurance: The OPC is designed for 60 days endurance while the LCSs are only designed for 21 days. Again the OPC will not have to break off operations to replenish as frequently as its LCS counterparts.

Operations in higher sea states: The DHS considered the possibility of replacing OPCs with LCSs but noted that while the OPC is designed to operate both its boats and helicopter in seas up to 4 meters, the LCS was expected to operate boats only to 2.1 meters and helicopters to 3.7 meters.

Quiet Operations for ASW: The water jet propulsion chosen for the LCSs work well at high speed but are relatively noisy and less efficient at low speeds. Additionally the OPCs are designed with “Promas rudders” which are claimed to increase maneuverability, speed, and fuel economy while decreasing noise compared to a conventional propeller/rudder interface

MODIFYING THE OPC TO FULFILL THE FFG ROLE:

Even before the Requirement Evaluation Team recognized the need for greater air defense capabilities and greater endurance, it was anticipated that the LCS would require major redesign.Quoting a recent Seapower Magazine article “Features Shaping Up for Lockheed Martin’s Frigate Proposal for Navy“,

Patton expects the FF to retain the 118-meter length of the Freedom class, with a steel hull and an aluminum topside. The additional berthing and cooling requirements, along with other hull, mechanical and electrical enhancements, will involve approximately a 40-percent redesign of the ship.(emphasis applied–Chuck)

While I think the OPC could be made a credible warship with relatively few modification, it is likely that the Navy would want to make some changes which I will discuss later.

The OPC has the advantage of having already been designed for a larger crew. Unlike the LCSs, it provides accommodations for 126, very near the expected complement of an FFG.

ASCM and ASW  Installation: The OPC could likely support installation of 16 anti-ship cruise missiles (ASCMs)

Below is a Harpoon installation on a Ticonderoga class cruiser, which has a beam of 55 feet–only one foot greater than that of the Offshore Patrol Cutter. As you can see, moved over to the side, it would not require the entire fantail leaving room on the fantail for ASW equipment. There may also be some room for ASW equipment in the compartment below the fantail.

Below is the Harpoon installation on a 3,600 ton ANZAC class frigate, a smaller ship, which has a beam of 49 ft–five feet less than that of the Offshore Patrol Cutters. A similar installation could be made on the OPC on the O-2 deck between the gun mount and the bridge.

091104-N-3038W-255 GULF OF OMAN (Nov. 4, 2009) The Australian navy frigate HMAS Toowoomba (FFH-156)

ESSM AAW missile installation: The Mk56 launch system provides a relatively light and structurally non-intrusive way to support the Evolved Sea Sparrow Missile System. The earlier and 25% heavier Mk48 system was used to provide up to 12 Sea Sparrow vertical launch missile tubes on the 450 ton full load, Danish Flyvefisken class STAN FLEX 300 vessels. The relatively small foot print of the Mk56 VLS system (pdf) can be seen below on a Danish Absalon-class command and support ship (beam 64 feet, ten feet more than the Offshore Patrol Cutter but they provide three twelve launch tube sets for ESSM). Two sets are visible in the foreground, one set of twelve with missile canisters with red tops in place to the right, on the ship’s centerline, and a second set of twelve without canisters to the left. A third set  is off camera to the right. 16 Harpoon launchers are seen in the background. It appears likely the OPC could support two twelve missile sets on the superstructure above the boat davits.

Photo below: Mk48 mod3 VLS for ESSM seen here mounted on the stern of a 450 ton 177 foot Danish StanFlex300 Flyvefisken class patrol boat.  Each tube could contain two, so this small installation could have provided 24 ESSM. The Mk56 launchers replace the Mk48s with an approximate 20% weight savings. (My wife tells me these look like port-a-potties.)

Replace the Mk38 mod2 with SeaRAM: Replacing the 25mm Mk38 mod2 atop the hangar with a SeaRAM would provide a stand alone missile system capable of defending the ship even if all power fails. Hopefully a second SeaRAM could also be provided forward as well.

Without major structural changes I believe the OPC design could be adapted to support

• an ASW system/multifunction towed array
• 16 anti-ship cruise missiles (with possible land attack capability depending on the choice of missile)
• 24 Evolved Sea Sparrow missiles
• At least one, perhaps two, SeaRAM systems
• Plus the planned 57mm Mk110

MAJOR DESIGN CHANGES:

The Navy may want to make additional changes including.

• A bigger gun
• More armor
• Less self noise
• Better radars
• More Speed
• More Missiles

These are all achievable at a cost.

Replace the gun: 

There has already been discussion about the desirability of replacing the 57mm on the LCSs. From the discussion it appears nothing larger would fit on the Independence class and nothing larger than a 76mm could fit on the Freedom class.

I see no reason why, given some strengthening of the structure, OPC based frigates could not be armed with the 5″/62 Mk45 mod4. This would provide much needed Naval Gunfire Support capability and potentially extended range guided projectiles. This is apparently not even an option for the LCS designs. 

The OPC’s 57mm Mk110 occupies some valuable real estate. If it is not replaced by a larger gun, it might be replaced a second SeaRAM system or a Vertical Launch missile system. If replaced by a missile system, it would likely be desirable to provide at least a pair of Mk38 mod3 mounts in place of the planned .50 caliber mounts.

070111-N-4515N-509
Atlantic Ocean (Jan. 9 2007) – Guided missile destroyer USS Forest Sherman (DDG 98) test fires its five-inch gun on the bow of the ship during training. The Sherman is currently conducting training exercises in the Atlantic Ocean. U.S. Navy photo by Mass Communication Specialist Seaman Apprentice Joshua Adam Nuzzo (RELEASED)

Add armor: This is another area where a displacement hull like the OPC’s would not be as adversely effected by additional weight, than the more exotic hull forms of the LCSs.

Less Self Noise: Making less noise is always an advantage in ASW. The less crowded engine rooms of the OPC probably make providing additional isolation easier. In addition upgrading the hybrid propulsion motors to 1,000 HP, as was considered at one time, would allow the ship to make 13 knots on generators alone.

Replace the radar: The OPC, like the LCSs will have a multifunction radar. This could conceivably be replaced by a more capable radar, including perhaps a scaled down version of the SPY-6.

Extend the hull–for speed: The speed figure we have for the OPC is a sustained speed of 22.5 knots I presume this means that maximum speed in all but the most adverse conditions is about 24 knots. This is enough for most purposes. It will keep up with Navy Amphibs and is faster than most merchant ships, but most frigates tend to have a speed of about 28 knots. That would likely require doubling the horsepower. This could be done by extending the hull amidships about 10 meters (33 feet) to provide what I believe would be a third main machinery space. A gas turbine might be added and would probably boost speed to 29 knots or more, but instead adding two additional diesel engines of the type currently planned would most likely provide 27-28 knots without the complication of another type of engine.

Use the extended hull–for a missile farm: Additional length, added to increase speed, could provide space for additional vertical launch systems amidships. These could be Mk41 systems or the newer Mk57s like those used on the DDG-1000, which are heavier but safer and require less maintenance.

SUMMARY:

Because of its conventional hull and greater displacement it is likely anything that can be added to a LCS can also be added to an OPC. The OPC could likely accept even more additional weapons than either of the LCS designs.

The OPC already enjoys several advantages over the LCSs most notably much longer range.

Modifying existing LCS designs will still involve much work and considerable risk. The OPC may require substantial modification as well, but the OPC already has far more accommodation space and range than either LCS design.

Using the OPC as the basis for a new Navy frigate is likely to save at least $200M per ship compared with similar modifications to a LCS design.