What Might a Wartime OPC Weapons Fit Look Like?


Four years ago I wrote a post suggesting that the Offshore Patrol Cutter might be designed from the start for a wartime weapons fit, but then fit them out with only those systems required for their peacetime missions, which might have included only its helicopter, UAS, and 25 mm Mk38 Mod2 gun(s).

I started with the assumption that the OPC should be able to mount a weight of weapons at least equal to those mounted on the 255 foot Owasco class cutters as built during World War II (140-150 tons). This figure did not include ammunition other than depth charges, consequently, nearly all the weight was above the main deck. This now appears very conservative in that the Eastern OPC design is about twice the size of the Owasco Class. (For another data point, when built, the USS Fletcher, first of a class of 175 destroyers with a design displacement of 2,700 tons, had 161.8 tons of armaments and 190.8 tons of ammunition.)

In the earlier post, a possible wartime outfit that I believed might be used for designing the ship (and the weights I used) included:

Total 124.4 tons

Since we now have a notional design for the cutter and my own views have changed somewhat, I thought it might be worthwhile to revisit how this class might be armed in wartime. The design may have ruled out some of the systems above, but the surprisingly large size suggest it should be fairly adaptable.

In fact it looks like the OPC could be turned into a credible warship adding only deck mounted systems that require only minimal deck penetration for cabling and the like.

What’s already there?:

Based on earlier information, as built, the design will includes provision for

For a total of 28.55 tons

Anti-Ship Cruise Missile:

LRASM topside launcher concept. The size and weight are comparable to launchers for Harpoon. Photo: Lockheed Martin.
Currently there are three potential anti-ship cruise missiles that might be used, Harpoon, LRASM, and Naval Strike Missile. Harpoon weighs 1,523 lb (691 kg) with a 488 pounds (221 kg) a warhead. Naval Strike missile is smaller, longer ranged, and more intelligence with a weight of 900 lbs (410 kg) with a 276 (125 kg) warhead. LRASM is the newest and supposedly the most “intelligent.”
As I posted earlier, I think the Coast Guard could use a couple of LRASM on each of their NSCs and OPCs even in peacetime as a means of addressing the threat of a terrorist attack using a medium or large ship. It is the missile’s range (about twice the others) and purported ability to target specific parts of a specific target rather than its larger warhead, that made the LRASM the system of choice for this role.
Reportedly the LRASM deck mount is comparable in size and weight to the Mk141, which is the standard quad deck launcher for Harpoon. The only source I could find, indicated that the weight of a quad Mk141 with missiles is 27,126 lbs or 13.6 tons, or 27.2 tons for an eight missile battery. Still I can’t believe the LRSM will not weigh a bit more than Harpoon, seeing its warhead is twice as large. I will assume a quad deck mount weighs about 15 tons, or 30 tons for an eight missile outfit. In any case, if other types of missiles were used, they would weigh less.
These might be positioned either on the fantail or on the platforms aft of the 57mm and below the bridge, one deck above the foc’sle where it appears they plan to mount .50 caliber machineguns possibly in Mk49 ROSAM.

RGM-84 Harpoon SSM was fired from a Mk-141 missile launcher aboard USS Shiloh (CG 67). The Shiloh’s beam is only one foot more than that of the Offshore Patrol Cutter. Looking at the photo, you can see that the launchers take up well under half the width of the fantail.


Photo: Click to enlarge

 Evolved Sea Sparrow Missile:
It appears it may be possible to equip the OPCs with ESSM (Evolved Sea Sparrow Missile). A new version of the missile, the ESSM block II, will obviate the need for illuminators that have been required for earlier versions. These would allow the cutter to provide limited local area AAW protection for ships that the cutter might be escorting out up to 25 miles. Additionally they can be used against surface targets.
Using the Mk56 VLS a loaded 12 missile module weighs 11.5 tons. Physically it is not very large. 3.66 m (12 ft) x 2.71 m (9 ft) x 4.65 m (15’3″) high. We could locate one or perhaps two of these on top of the superstructure where they apparently intend to store the third boat.  This may seem relative high in the ship, but it is the same position where the Oliver Hazard Perry (FFG-7) Class frigates mounted their 76mm gun and the OPC is considerably beamier (54 vis 45 foot).


Photo: Click to enlarge. The relatively small foot print of the Mk56 VLS system (pdf) can be seen here on a Danish Absalon-class command and support ship (beam 64 feet, by comparison the Offshore Patrol Cutters’ beam is 54 feet–same as that of the Bertholf class National Security Cutters).  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. The Absalon class has three twelve missile sets, with the third set off camera to the right. 

Photo: 12 earlier Mk48 mod3 VLS for ESSM seen here mounted on the stern of a 450 ton 177 foot Danish StanFlex300 Flyvefisken class patrol boat.  The Mk56 launchers replace the Mk48s with an approximate 20% weight savings. 
This could really be any of three systems, Phalanx, SeaRAM (a modified Phalanx with eleven rolling airframe missiles instead of the 20 mm gun) or the 21 round Mk 49 RAM launcher. Loaded, all three are about 8.5 tons or less.
An operations research study done for Australia “Limitations of Guns as a Defence against Manoeuvring Air Weapons,” (pdf) by Christian Wachsberger, Michael Lucas and Alexander Krstic, Weapons Systems Division, Systems Sciences Laboratory, DSTO-TN-0565 has convinced me that gun systems are unlikely to effective in the future, so for the OPC I would choose two SeaRAM. This has also been chosen for the frigate follow on to the Navy’s LCS.
Two LCS systems could provide automated 360 degree protection against the sudden attack of a coordinated anti-ship missile attack. One system could replace the Mk38 mod2 system currently planned for placement on top of the hangar. A second system could be sited on the superstructure forward and below the bridge, behind and above the 57mm. This might require a small extension of the superstructure to provide a platform sufficiently large enough to both support the system and allow access for maintenance.
AN/SQR-20 Multi-Function Array (Thales CAPTAS 4):
Photo: NavyRecognitionReeling system for the CAPTAS-4 Variable Depth Sonar tether aboard a French Navy FREMM Frigate (Aquitaine class).
If there is a submarine threat, we will need a sonar. Additionally passive towed arrays may be used as a targetting system for anti-ship cruise missiles. In peacetime, a towed array might also be to locate semi-submersibles.
The Thales CAPTAS-4 is one of the systems being considered for the LCS and its frigate derivative. The current version weighs 20.6 tons. The US version will probably be lighter since the Navy is looking for a lighter version for the LCS. Additionally there are lighter options made by Thales and others, so what ever might be chosen is going to be this weight or less. It would of course be mounted on the fantail.

Mk38 mod2/3 and Mk49 ROSAM: 

I will assume that the two Mk49 RO

SAM will be retained and the Mk38 mod2 (or mod3) will be relocated and a second Mk38 (1.15 tons) will be added.


The resulting additions would be:

  • Multi-Function Array (CAPTAS-4) (20.6 tons)
  • MH-60 (11.75 tons)
  • 8 x LRASM (30 tons)
  • 24 x ESSM (23 tons)
  • 2 x SeaRAM (22 missiles) (17 tons)
  • 57mm Mk110 gun w/1000 rounds (15.4 tons)
  • 2 x Mk38 mod2/3 (2.3 tons)
  • 2 x .50 cal. in Mk49 ROSAM (0.25 tons)

This totals 120.3 tons or 91.75 tons more than the planned outfit as built.

We don’t really know if the ship can take this much weight. Assuming it displaces 4,000 tons, which seems likely, this is about a 2.3% increase in displacement and much of the weight is relatively high.

Is it feasible?

There are things that can be done to counterbalance the effects of this additional weight. Some fuel tanks might have to be left permanently full or be converted to ballast tanks. Given the extreme range of the cutter, even half of the design range would be more range than most Navy combatants.

We know the ship is supposed to have some weight moment reservation for additional weapons but we don’t know how much. There is also the requirement that the ship be able to take on, feed and shelter 500 migrants on the foc’sle or flight deck. Those 500 people alone would amount to almost 40 tons of additional top weight.

There are alternatives that could provide a simlar outfit while moving the weight lower. A more extreme change would be to replace both the Mk56 VLS (23 tons) and the 57mm Mk110 (15.4 tons) with Mk41 VLS (33.6 tons) in place of the 57mm. We would loose the gun, but this would provide the additional capability of launching Anti-Submarine Rockets (ASROC) as well. That might be a good trade, but it would require more radical reconstruction.

In short, adding less weight in weapons than carried by the 255 foot Owasco Class cutters of WWII, the Offshore Patrol Cutter could be turned into an effect surface combatant comparable to many frigates. The same sort of alterations could also be appied to the National Security Cutters.

47 thoughts on “What Might a Wartime OPC Weapons Fit Look Like?

  1. The Owasco class had twin 5″ mounts that weighed about 40 tons each. This did not include the ammunition. I am not so sure the Coast Guard wants a full weapons suite. The culture has changed.

  2. It would not need to be anything radical to add utility. Up gun from 57mm to the 5-inch/62 calier gun. Add the Sea Ram. It’s not going to take on a Kirov but it adds utility and survive-ability.

    • What I suggested above would be for a prolonged conflict with a near peer, but for a different type of conflict we could do without several of these systems. If we were doing something like MarketTime, we could probably do it with no changes, but I would still like to have the two SeaRAM in case the insurgents on shore got anti-ship cruise missiles and some vertical launch Hellfire like they are planning for the LCS, would also probably come in handy.

  3. I guess I’m going to be a bit contrarian, or perhaps, more realistic. I’d first ask what the CONOPS for the OPC would be. I see two, primarily: Homeland Security During War (HSDW), or Escort ship for convoys from homeland to Theater of Operations. The third most-likely mission would be in-theater near-shore ops, but the Navy’s LCS should fill that role sufficiently. On ships the size of the OPC (or NSC for that matter), I think we need to question the “do-it-all” capable ship. It’s very hard to include robustly-capable weapon systems in all 3 environments of naval warfare on such small ships. In my view, it is better to be really capable in one or two roles, rather than barely capable in all three…

    In either HSDW or Escort roles, ASW will be the primary threat BY FAR. Air attack is most likely to be via an ASM, launched by a sub, or from stand-off range by a bomber. In HSDW, if there is an air threat, CONUS-based fighters would handle it. In Escort role, a close-in, non-missile air threat would not be easily handle-able by non-robust shipboard systems (anything short of Standard).

    ASW must be the primary focus. In HSDW, P-3/P-8s would be operating heavily in the role in the same areas also. Some manner of data link to cooperatively execute the ASW kill cycle with these highly capable aircraft would be critical. The TACTAS system you’ve identified would be an excellent fit. The H-60 flight deck allows deployment of Navy SH-60s, which would be the primary prosecutor of an ASW attack by the cutter. Shipboard ASW weapons are a problem, not just for the USCG, but for the Navy as well. The lightweight torpedos installed throughout the surface fleet are not truly offensive ASW weapons due to limited range and warhead, and ASROC is very, very long in the tooth and of questionable offensive power as well. Anti-torpedo defensive measures would be critical as well, such as AN/SLQ-25 Nixie.

    For protection against an ASM, arguably the most effective system is the SLQ-32, which I’m thrilled to see appears to be installed upon fitting out! (Great move!!). I am curious if RBOC will also be incorporated from commissioning, as it makes sense as a part of the SLQ-32 system… By going with diesels, there will be a much smaller IR signature, so then comes active defense systems. Both SeaRam and Sea Sparrow are defensive, short-range, SAMs with secondary capability against surface targets. Sparrow has a bigger warhead and slightly longer range, but SeaRam is a self-contained system, which fits MUCH BETTER in the concept of adding on later, not just due to complexity, but also crew training. (SeaRAM just needs turned on, and it automatically detects, tracks, and prosecutes with just a simple, man-in-the-loop authorization to fire.). I do NOT see a reason for both Sparrow and SeaRAM. They overlap too much in their capabilities.

    This leaves surface warfare. I don’t see this as a likely mission given the CONOPS I started with above. In my opinion, it will be an activity extremely similar to the peacetime ops of the CG: interdiction, boarding, and possibly, anti-landing of operatives (a mission better suited to smaller CG platforms). I’m satisfied with the 57mm and the .50-cals for this. No need for Harpoon or its follow-on system. I just don’t see the OPC carting off to a high-threat environment overseas to go toe-to-toe with far more capable, purpose-designed, warships. Is the OPC going to have commercial-level compartmentalization or military? Any armor? It would be suicidal to send OPC into such situations.

    • ESSM and RAM serve different purposes. RAM is a short ranged (only a little over 10 miled in its latest form) self defense weapon. ESSM is a medium ranged system (a little over 25 miles) that provides a degree of area defense. If we are going to protect ships we are escorting from submarine and air launched ASCMs, we will need ESSM. We also need it to shoot down medium altitude UAVs that might also be armed, or tactical aircraft that might be armed with guided bombs (if possible, we want to kill the aircraft rather than the bomb).

    • Soft kill systems (ECM and decoys) have had a much better record against ASCMs than hard kill systems, but ASCMs are getting smarter with target recognition capabilities even being able to target specific parts of the target vessel. Consequently we will definitely need hard kill capabilities if the cutter needs to deal with inbound ASCMs.

      • Agree with both your posts above. I must admit, had a senior moment and was thinking the old Sea Sparrow rather than the new ESSM… Considering the potential enemy’s threat systems, you are right. Best bet would be to have both ESSM and RAM. However, while ESSM gives some capability against aircraft, I’d hope something with Aegis would be part of the escort group too. Realistically, if tactical aircraft are in the threat matrix, there will be more difficult and more numerous inbound targets to address at all ranges. I believe, with propper data links ESSM on say an OPC, could be launched and guided by the aegis ship. Is ESSM able to use CEC?

      • Put a 16 round Mk41 in the NSC along with 40 ESSM, and 6 ASROC’s you would have a powerful ASW/Point defense ship for MSO and escort.

      • Not sure if Cooperative Engagement Capbility (CEC) is applicable to OPC as I have suggested it might be rearmed (probably would be), but if Mk41 VLS is used, NSC or OPC could theoretically load Standard missile and launch it at a target at very long range, using third party information from say an E-2 or E-3, and the target could be either an aircraft or a surface target.

  4. The new OPC seems relatively capable, but IMO, Coast Guard ships should be armed only when absolutely necessary, and only after all available Navy vessels have their full load-out of weapons.

    A basic fitting of 1-57mm, 2 25 or 30mm stabilized weapons, and a few .50 cal are fine for typical patrols. Adding 1 SeaRAM launcher as a basic defensive upgrade would be reasonable. But unless you’re going to add a hull-mounted sonar and adequately train crews for ASW, adding towed array sonars and Mk32 during conflict seems pointless.

    Adding anti-ship missiles could make sense, but again, IMO, these should be left-over Harpoon SSMs to ensure that the NAVY and USCG NSC get front-line systems. Further additions of SAM systems should similarly be limited to an additional SeaRAM, if space/weight permit.

    • A very common point of view, and I understand it. There is a good argument that it is a waste of money to equip before actual conflict. But, in modern conflict, if you are not equipped with it on day 1, you are of little to no use, for quite some time, and, by the time you get equipped, the war may be over, and you were of no use whatsoever…

      One of the cultural problems for the CG is mission expansion. Historically, the CG and its predecessor agencies have been given missions because they were the only civil agency afloat, the Navy didn’t want it, or agencies consolidated. This has left the CG with life-saving, law enforcement, environmental response, ATON, icebreaking, oh yeah, and National Defense. This causes a culture of diversified purpose which undermines objective analysis of what is necessary for each job. It also causes CG leadership (for over a century now) to say the CG can do more with less money. This always results in inadequacy and frequently failure (not always, because brilliant performances by the people saves the CG, usually). Hence, my point above about, “if you don’t have it on day 1…”

      I completely agree with your point about adequate training.

      Insofar as hull-mounted vs. towed array, hull mounted is by far the worse option. First, it is not a simple/easy retrofit; quite the opposite of towed arrays. Second, towed sonars are much more capable.

      I agree a surface to surface system would be nice, but why? ASW will be 80%+ of the threat faced by these ships, unless they are recklessly thrown into the front lines. I see Chuck’s point about targeting a terrorist-driven large ship like an LNG tanker, but other than that, what does it get us for the weight and manpower requirements? (I suppose if you see the CONOPS differently than I do, I understand.)

      • Hopefully we wil train crews as the systems are added.

        In the wind up to WWII, the CG had essentially zero ASW capability. We learned from the Navy and from the Brits–even got some equipment from the Brits. It did take some time for training to catch up, but it was still took less time than building new ships for the Navy. Before the end of the war we were at least as good as the Navy

    • Just want to clarify, when we start talking about weapon systems, I generally am thinking about the war-time national defense mission. In my opinion, for peacetime law enforcement, fisheries/EEZ enforcement, migrant interdiction, drug interdiction, there’s very little additions needed for the weaponry than what is in the artist’s rendering. Intelligence, communications, situational awareness is 75% of the problem there, not weapons…

      There are two general, likely wartime scenarios for the U.S., I think. One is a long-term war, the other is a sudden, sharp strike followed by disengagement and denial. If Russia, China, or possibly N. Korea are involved, the threat of submarines operating near-shore around CONUS is high.

      Yes, Chuck, the CG did gear up for ASW during WWII, but don’t forget we (USN and USCG) sucked for the first year of the war, and U-boots had their “Happy Time” shooting tankers silhouetted against lit up American coastal cities with impunity for a time. (And just for clarity sake, it is easily documentable that the CG was far better than the Navy at ASW, eventually… 😉 )

      The difference today is we’re not fighting commerce raiding U-boots. The threat is SSBNs and cruise missiles each of which could strike deep, deep into the homeland and carry WMD. Granted, mining, inserting operatives, destruction/restricting shipping, and possibly bottling up our naval forces are other possible missions of an enemy submarine on our doorstep, but the strike/WMD mission is scariest. OPCs, FRCs, Navy P-3/P-8 squadrons are right on the front lines of defending CONUS and are capable platforms (if equipped, manned, and trained) and could easily be tasked with creating a robust defense in depth against such threats at the cost of adding a few crewman and systems.

      With their lower speed, civilian-level compartmentalization, lack of armor, and low manning levels, the OPC is not a great asset to put in a high-intensity environment with threats coming from every domain (air, shore, surface, and undersea). It would be too easy to overwhelm their defensive systems, and their vulnerabilities would be great disadvantages. Install multi-domain weapons systems, and commanders will look at them as “mini-Burkes” and put them in precarious situations.

      Make them Sub hunter/killers in team with Navy Patrol Sqdrns. and keep CONUS safe and commerce flowing.

      • The OPCs are built to modified ABS warship rules. The NSCs are not. The OPCs also are supposed to have some ballistic protection. Generally there is very little armor on any warships these days. Destroyers in WWII had almost none.

        Hopefully we will get an earlier jump on the training than we did for WWII.
        If we are wise, we will make changes to the cutters before they are needed.

      • Wow, did not know that. I’m happily surprised about the construction standards and armor. I assumed if they went the commercial standards route with the NSC, they’d do so again with OPC. Since compartmentalization and, to a certain degree, armor is nearly impossible to upgrade/retrofit, I predicated a lot of my CONOPS on avoiding high-threat areas. I wonder how modified the build specifications are from the standard?

        And modern armor is not usually thicker steel, and does not cover the whole ship. It does cover important spaces, which would be catastrophic if hit. In WWII, armor = steel, so of course no DDs had it. Would they have installed modern, lightweight armor over themagazines, if they had it back then? I think probably…

      • FRCs are also built to ABS standard. Main modification I am aware of is that there will be no shock test.

        Fletcher class destroyers had armored trunk protecting the fire control system datal path. That made a big difference in their survivability and ability to stay in the fight.

        I assume the protection the OPCs will have is protection against small arms and “splinters.” (for those unfamiliar with the term, in this context, splinters are fragments either from the warhead or from ship parts blown apart by an explosion.)

      • The NSC’s aren’t complete commercial standards either, they are about 90% military standard. The Coast Guard is pretty quiet about standards/armor and that sort of thing.

  5. Just two questions:

    If ASW will be 80%+ of the threat faced by NSC and OPC, one has to consider that modern 21 inches heavyweight torpedoes firing through the stern can be very useful. Not only can they be fired a stand off distances, they are also devastating anti ship weapons.

    So, if the cutters are getting towed sonars, why not also 21 inch torpedoes?

    Regarding RAM and SeaRAM, embarking just 1 system (i.e., not having 360º coverage) is an acceptable risk for a ship working as an ASW-picket?

    • IMO, yes to both.

      The lack of heavy/offensive ASW weapons for surface ships is a problem. To prosecute any ASW attack at a reasonably safe distance (or at least an equal distance to enemy sub weapons) requires the use of the ASW helo. The only practical (near-term) alternative is 21″ TTs with Mk.48 AdCaps. This has been discussed by the Navy, but no follow-through… The stern is going to get crowded fast. Installing a towed array sonar plus a Nixie system will take up most, if not all space back there.

      And, considering the lower-intensity environment in my CONOPS, a single RAM system should be adequate, especially on this size ship, and especially if mounted high (in place of the 25mm, let’s say).

      • If the only threat is submarine launched ASCMs, then eleven ready missiles (one SeaRAM) is probably enough, but if the ship is close to a hostile shore or subject to air launched ASCMs, then we probably want more ready service rounds than that.

        There is also the potential of missiles coming in from the bow being in a blind spot. Theoretically you could turn the ship, but maybe not–Stealth missiles or extremely fast missiles.

    • I certainly would not mind seeing heavy wieight torpedoes return to ASW escorts, but all the Western Countries that used them previously have removed them.

      The Indian and Russian navies still use heavy weight torpedoes for both ASW and ASuW. In fact the Russians launch their ASROC equivilent from torpedo tubes.

      ASROC has been updated and now uses the Mk54 torpedo and has a range of 24,000 yards. That is really not bad.

    • Specs were not made public, so that is an unknown. If they were converted to ASW escorts, that would certainly be required, and would be added if not included as built.

      I was encouraged to see that the NSCs do have an elevator from the hangar although currently it is used for conventional stores. I would presume the OPC is similarly equipped.

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    • i read it, and it looks like a direct competitor to the FF923. But how would the two ships compare in capabilities and possible weapon load outs. Not really familiar with the European VLS systems. Realizing both projects are paper projects at the moment.

    • A little more news from Defense News. http://www.defensenews.com/articles/france-unveils-new-fti-frigate-ship-is-designed-for-the-french-navy-and-for-export

      “The multimission FTI frigate will carry a 125-strong crew – including a 15-person aviation detachment and with accommodation for another 50 — displace 4,250 tons and come with a price tag 20-30 percent less than the 6,000-ton Fremm, which has entered service with the French Navy with more units under construction by DCNS. The ship has an overall length of 122.25 m and a beam of 17.7 m.”

      The French frigate is also pretty beamy. Length to Beam is also less than 7 to one. Beam is 56 feet.

      Their 2×8 VLS are similar to the Mk41s. The ASTER30s are about the same size as Standard missiles. https://en.wikipedia.org/wiki/Aster_(missile_family)

      • If i had to choose a ship based on weapons fit i would pick the PF923 with its 16 mk41’s. You can quad pack RIM-162 ESSM’s. You can not quad pack Aster15’s. But they probably have designs already to replace the Sylver with the Mk41 for export.

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