Modern submarine chaser

[johnpjones1775]

An article about the Irish having to call the RN to scare a Russian sub away from its territorial waters last summer, and thought a sub chaser would be able to solve that problem…but sensors and weapons for ASW have come a long way, and can a ship be built small and cheap enough to really mimic the fleet role their predecessors held?

I feel it could, but a lot of people would be very unhappy with the result.

 

[that_person]

I think they arguably tried to do that with the LCS ASW mission module. A fully missionized LCS was supposed to cost $350 million, have a TA, sensor drones, and a helo to prosecute targets. The obvious downside is the lack of a hull mounted sonar, limited torpedo defense, and no quieting equipment. I do think you could build a modern sub chaser using LCS-type principles though, even while retaining the modular equipment.

 

[johnpjones1775]

I think they arguably tried to do that with the LCS ASW mission module. A fully missionized LCS was supposed to cost $350 million, have a TA, sensor drones, and a helo to prosecute targets. The obvious downside is the lack of a hull mounted sonar, limited torpedo defense, and no quieting equipment. I do think you could build a modern sub chaser using LCS-type principles though, even while retaining the modular equipment.

No, the LCS was never intended to fit the subchaser role. Always been closer to an APD in use and relative availability.

Too big, and not enough hulls but both able to conduct ASW missions if necessary, alone with transport, and defense against small craft

 

[Arjen]

@johnpjones1775 Please change thread title from SUN chaser to SUB chaser? Current title would make thread difficult to track.

 

[that_person]

No, the LCS was never intended to fit the subchaser role. Always been closer to an APD in use and relative availability.

Too big, and not enough hulls but both able to conduct ASW missions if necessary, alone with transport, and defense against small craft

I’d very much disagreed. Sun chasers are characterized as being small, cheap, have very little emphasis on anything besides ASW, and group operations in a flotilla. That very much fits the LCS.

You also realize the original plan was to procure ~55 hulls right, most of which would be upgunned from what we got in reality? Defense against small craft can be handled with the Mk110, there’s no need for dedicated equipment.

 

[H_K]

sensors and weapons for ASW have come a long way, and can a ship be built small and cheap enough

It probably wouldn’t be a dedicated ship. There have been trials of towed sonar modules like CAPTAS-1 aboard various platforms including landing craft and offshore support vessels. These would be perfectly able to do the coastal ASW patrol mission that subchasers used to do, with land based ASW helicopters & patrol aircraft (or drones) handling the engagement with torpedoes.

Thales Captas-1 Towed Sonar Tested Aboard CNIM's L-CAT Landing Catamar

a EURONAVAL 2016 Online Show Daily - Thales, CNIM

navyrecognition.com

French Navy Starts Trials of Variable Depth Sonar aboard Loire-class Offshore Support Vessel - Naval News

The French Navy (Marine Nationale) and French Armament General Directorate (DGA) started trials of the Thales CAPTAS-1 variable depth sonar (VDS) aboard Loire-class offshore support and assistance vessel (BSAM) "Garonne" off Brest, in Brittany.

www.navalnews.com

 

[1Big Rich]

No, the LCS was never intended to fit the subchaser role. Always been closer to an APD in use and relative availability.

Too big, and not enough hulls but both able to conduct ASW missions if necessary, alone with transport, and defense against small craft

I agree on too big. Independence passing Wayne E. Meyer DDG-108

Regards,

 

[TomS]

It probably wouldn’t be a dedicated ship. There have been trials of towed sonar modules like CAPTAS-1 aboard various platforms including landing craft and offshore support vessels. These would be perfectly able to do the coastal ASW patrol mission that subchasers used to do, with land based ASW helicopters & patrol aircraft (or drones) handling the engagement with torpedoes.

Thales Captas-1 Towed Sonar Tested Aboard CNIM's L-CAT Landing Catamar

a EURONAVAL 2016 Online Show Daily - Thales, CNIM

navyrecognition.com

French Navy Starts Trials of Variable Depth Sonar aboard Loire-class Offshore Support Vessel - Naval News

The French Navy (Marine Nationale) and French Armament General Directorate (DGA) started trials of the Thales CAPTAS-1 variable depth sonar (VDS) aboard Loire-class offshore support and assistance vessel (BSAM) "Garonne" off Brest, in Brittany.

www.navalnews.com

I agree with part of this, in that CAPTAS-1 or similar systems are about the minimum acceptable for the sort of role being asked for.

I'm skeptical about this "craft of opportunity" platform concept, though. It falls down on some of the same issues that killed LCS as a serious ASW platform. In particular, self-noise is very bad for ASW, even with a towed sonar like CAPTAS. You need to pay some real attention to silencing of the tow platform, at which point you're headed for at least a semi-dedicated vessel. Also, there are real issues with crew proficiency in COOP scenarios. ASW especially continues to be a very perishable skill that required dedicated crews for systems and platforms both.

So, what is the minimum possible platform that one could use? That hinges on two main issues: what systems do you need for a minimum credible ASW capability and 2) what size do you need for acceptable seakeeping?

1) Bare minimum is a CAPTAS-1 or equivalent sonar, which basically fits a 20-foot container, plus the requisite control room and so forth. And some way to prosecute a submarine contact (else what's the point of tracking?) That translates into at minimum something like ELMA ASW-600 mortars. But preferable would be some sort of light helicopter or heavy VTOL UAS that can drop an ASW torpedo. That air vehicle could also conduct more general surface surveillance when submarines are not around, so that your "sub chaser" is also an effective fisheries enforcement vessel or rescue ship, which is what it is going to spend 90% of its life doing anyway. Plus a gun of some sort, if only to fire warning shots at fishing boats (something around 35-40mm is probably sufficient, possibly up to 57-76mm given the size of modern fiching vessels). You can probably accept a minimum air defense capacity -- decoys and the gun, since this vessel isn't expected to fight above-water combatants or hostile aircraft. Radar can be fairly basic as well, but something with decent perisope detection modes would be helpful.

2) "Coastal" for Ireland means the North Atlantic in winter, so no small patrol boat is going to hack it for at least a third of the year. Bare minimum is probably in the 1000- to 1500-ton range.

Notably, Ireland just bought a pair of 340-ton Inshore Patrol Vessels from New Zealand, which are meant to operate in the Irish Sea so the bigger 1500-ton OPVs can focus on the western coastline. That's assuming the Irish Naval Service ever finds the manpower to operate the bigger ships again.

Government purchases two ships for naval service from New Zealand

The procurement of the two vessels is part of the “regeneration” of Ireland’s Naval Service.

www.thejournal.ie

Two naval ships to be tied up as staffing crisis deepens in Irish Navy

News of the mothballing of the ships comes just a day before Minister for Defence Micheál Martin visits troops in Lebanon.

www.thejournal.ie

 

[johnpjones1775]

I’d say something the around the size of a cyclone.
HMS-x2 hull mounted sonar
Small-medium quadcopter drone squadron to drop sono-buoys
At least 2 single LW torpedo launchers, and USV that can carry 1-2 LW torpedoes
SEARAM or phalanx on the bow, and a few crew served weapons.

Something like that should be less than $100m easy.

I’d very much disagreed. Sun chasers are characterized as being small, cheap, have very little emphasis on anything besides ASW, and group operations in a flotilla. That very much fits the LCS.

You also realize the original plan was to procure ~55 hulls right, most of which would be upgunned from what we got in reality? Defense against small craft can be handled with the Mk110, there’s no need for dedicated equipment.

55 hills divided into use between 3 modules.

 

[TomS]

I’d say something the around the size of a cyclone.
HMS-x2 hull mounted sonar
Small-medium quadcopter drone squadron to drop sono-buoys
At least 2 single LW torpedo launchers, and USV that can carry 1-2 LW torpedoes
SEARAM or phalanx on the bow, and a few crew served weapons.

That does not fit on a Cyclone hull. Not even remotely. Like I said, you're easily up to at least 1000 tons here. (Plus, why on earth two hull sonars? SQQ-23 PAIR was a special case that modern technology has made irrelevant.)

And no "small-medium quadcopter" can carry enough sonobouys to lay a proper pattern.

You do make a good point about USV (or perhaps even UUV) as a towed sensor platform. Nice to have a semi-expendable bistatic source, at least. But again, consider the conditions. How do we feel about an 11-meter RHIB in the North Atlantic. I think it's a gonner.

 

[A Tentative Fleet Plan]

Hope the sensor USV is silenced, and I can't imagine all but the largest USVs currently in the market would be capable of towing any kind of existing towed array.

Certainly large towed sensors seems to need a fairly large (and structurally strong) ship to tow them, apparently Type 2031Z caused severe strain to the Leander-class that carried it, and it was feared that the longer and heavier Type 2038 would do the same to the Type 23s.

 

[TomS]

Hope the sensor USV is silenced, and I can't imagine all but the largest USVs currently in the market would be capable of towing any kind of existing towed array.

There are some really lightweight thin-line towed arrays out there.

Actually, a capacity like this one might be far better suite to Irish needs -- long-endurance USVs towing thin-line sonars, paired with a low-cost MPA for more "active" interventions:

Thales, Ocius team up on USVs equipped for ASW and surveillance missions

Thales Australia and Ocius Technologies have entered a teaming agreement to advance the development and deployment of a scalable unmanned surface vehicle (USV) capability equipped for anti-submarine warfare (ASW) and surveillance missions.

www.navaltoday.com

 

[A Tentative Fleet Plan]

Ireland does have a population slightly smaller than that of Denmark or Norway, and has larger economy than both, I think they can afford actual ASW frigates.

 

[Jimmo952]

I’d very much disagreed. Sun chasers are characterized as being small, cheap, have very little emphasis on anything besides ASW, and group operations in a flotilla. That very much fits the LCS.

You also realize the original plan was to procure ~55 hulls right, most of which would be upgunned from what we got in reality? Defense against small craft can be handled with the Mk110, there’s no need for dedicated equipment.

LCS was initially intended to perform shallow water ASW. Those plans were abandoned when it was determined the ships were not suited for the task.

 

[johnpjones1775]

That does not fit on a Cyclone hull. Not even remotely. Like I said, you're easily up to at least 1000 tons here. (Plus, why on earth two hull sonars? SQQ-23 PAIR was a special case that modern technology has made irrelevant.)

And no "small-medium quadcopter" can carry enough sonobouys to lay a proper pattern.

You do make a good point about USV (or perhaps even UUV) as a towed sensor platform. Nice to have a semi-expendable bistatic source, at least. But again, consider the conditions. How do we feel about an 11-meter RHIB in the North Atlantic. I think it's a gonner.

No one said anything about two hull sonars?

You can definitely fit all of that on something roughly in the size range of a cyclone. 2 LW torpedoes amidships doesn’t take up too much space…though on second thought a single triple launcher a midships would probably take up less space over all.
Aft on a cyclone there’s plenty of space for a USV that could carry a fewW torpedoes, inside there’s plenty of space for sink-buoys and small/medium sized quadcopter, and bow has plenty of room for a SEARAM or phalanx.

Again no one said a single drone. 3-6 send them up, drop buoys, come back, load more onto them, send them out again, to drop more.

 

[johnpjones1775]

LCS was initially intended to perform shallow water ASW. Those plans were abandoned when it was determined the ships were not suited for the task.

That doesn’t equate to a subchaser
Lots of ships have ASW capabilities, even in WWII that didn’t make them sub chasers.

LCSes are much closer in role, size and availability to APDs.
LCSes are too big and too expensive to fill the role of a subchaser, they were never intended to fill that role.

 

[johnpjones1775]

Ireland does have a population slightly smaller than that of Denmark or Norway, and has larger economy than both, I think they can afford actual ASW frigates.

What they can afford and what they’re willing to buy are very different things.

 

[1635yankee]

I suspect that smallest useful "sub chaser" for the North Sea would be about the size of the RN's Batch 2 River class, when accounting for the weight (and volume) of silencing, sensors, weapons, and command and control facilities. Even this may be too small to operate a manned helicopter or UAV in many weather conditions.

----------------

As I'm neither an Irish citizen nor resident, I don't feel it's my place to criticize the decisions of the Irish government, but it seems that they're not trying hard enough to maintain their defense force's personnel numbers. Perhaps they need to raise the salaries and benefits of their defense personnel.

 

[TomS]

No one said anything about two hull sonars?

You can definitely fit all of that on something roughly in the size range of a cyclone. 2 LW torpedoes amidships doesn’t take up too much space…though on second thought a single triple launcher a midships would probably take up less space over all.
Aft on a cyclone there’s plenty of space for a USV that could carry a fewW torpedoes, inside there’s plenty of space for sink-buoys and small/medium sized quadcopter, and bow has plenty of room for a SEARAM or phalanx.

Again no one said a single drone. 3-6 send them up, drop buoys, come back, load more onto them, send them out again, to drop more.

OK, didn't realize that HMS-X2 is a specific (indian) hull sonar.

As far as payload, I reiterate that the payload you describe is much too large for a Cyclone-sized hull. Phalanx weights several times as much as the 25mm mount that sits forward on the PCs. The USV you want replaces the RHIB. The crew served weapons are the same as the PC. And now we're starting to run out of weight and deck area for torpedo tubes, sonar, a UAV pad and hangar, etc.

 

[Scott Kenny]

Frankly, I'm not sure I'd want to be on a 1500ton ship in the winter North Atlantic, I've seen video of waves breaking over the bow of a carrier!

But sure, I'll play.

Bare minimums:

• You need a VDS and possibly a surface towed array to listen, because a sub will either be at periscope depth or under a thermocline. And, if he has friends, only one will be up at PD while the others are deep.
• You need some flavor of active sonar, to politely inform the submarine that he is not being sneaky, and needs to bugger off someplace else. If the towed arrays can do this, cool, if not you need a hull sonar as well.
• And you need a way to violently inform the submarine that he is not being sneaky and needs to bugger off right fooking now. ASROC/Icara/equivalent, helicopter or drone dropping torpedoes, maybe a triple tube of LWTs on deck if you can arrange space for it.
• Deck Gun because this is officially a warship, plus radar and chaff/decoy launchers. Because we're trying to keep this cheap, no SAMs, no AShMs. Maybe a CIWS or SeaRAM mounted somewhere, but that's it.

Having a helicopter deck is just generally useful for 90% of the things you use a ship for, even if you're not actively hunting a submarine at the moment, so I'd say that you need a helo deck on everything big enough to hold one. And if a ship is close to being big enough for a helo deck, look to see how much it'd cost to add the length for a full size helo deck and not just a drone-sized landing pad.

 

[H_K]

I’d consider one of these 70 ton trimarans as an optionally-manned VDS sonar tug. Engagement could be done by land based air or by launching a heavy quadcopter lugging a mini-torpedo.

Benefit of a trimaran being much better seakeeping and range relative to overall size compared to a monohull… still not very comfortable so better unmanned.

View: https://youtu.be/k4kmjMto6Xw?feature=shared

Not convinced it would need much in the way of self-defense, but with lightweight decoy launchers weighing as little as 150kg and small 30mm remote weapon stations weighing 400-500kg with the ability to engage drones and add Stinger or Javelin missiles, those might be nice to have at least “fitted for not with.”

 

[apparition13]

I really like the Danes for this kind of thing. Flyvefisken with the ASW kit could do the job, Knud Rasmussen has the size and helicopter deck to add drones, though it would need more speed so it would also need a larger powerplant.

 

[Scott Kenny]

I’d consider one of these 70 ton trimarans as an optionally-manned VDS sonar tug. Engagement could be done by land based air or by launching a heavy quadcopter lugging a mini-torpedo.

Benefit of a trimaran being much better seakeeping and range relative to overall size compared to a monohull… still not very comfortable so better unmanned. Not convinced it would need much in the way of self-defense or decoys.

The amount of defenses you want on a UUV depends on how disposable you think the sonars are, but if those are passive-only you can probably get away with less defenses on the grounds that they're highly unlikely to be detected. IIRC the USN went with that idea on the SWATH SURTASS ships.

However, the UUVs being passive-only means that they also don't have a way to politely tell the submarine that he's been caught so it's time to leave, which leaves shore-based air or a drone with some active sonobuoys.

My concern about many of the commercial ship hulls is how noisy they are. I'm sure I've told the story before, how the HSV-2 at 30nmi managed to completely drown out a contact we had at 15nmi, and how I had to shout to talk to my OOD standing 2ft away when the HSV-2 was about 5nmi away when we were on the surface. Anything using passive sonars needs to be built for the job.

 

[kaiserbill]

Ireland does have a population slightly smaller than that of Denmark or Norway, and has larger economy than both, I think they can afford actual ASW frigates.

Ireland also has some of the highest debt per capita on the planet, due to the crash and bailout from yesteryear.
2nd highest debt per capita, 4th highest per % of GDP.
Irish GDP figures are very heavily skewed because of tax receipts earned on total EU wide earnings of a few large multinationals due to a lower corporate tax rate.
This lower tax rate is due to be ended shortly, with an approximate 50% increase from 2024, over the current true rate.

Then the true picture will emerge, over time.

In short, the Irish economy is not what it appears to be at all.

The Irish naval service cannot at present man the OPV's it currently has. It can currently only man 2 out of the 8 Offshore Patrol Vessels, and have been forced to decommission 2 of them.
This is a widely known and reported situation within Ireland.

 

[TomS]

IIRC the USN went with that idea on the SWATH SURTASS ships.

Which sort of defies reality, considering how hard the SURTASS ships have been harassed by the PLAN over the years.

 

[Kat Tsun]

Boats are big, expensive, and hard to man now. Presumably the best modern sub chaser is a cheap robotic plane.

Isn't Turkey making maritime/anti-submarine payloads for their MALE UAS? An MQ-9 would be a good UK option.

 

[Scott Kenny]

Which sort of defies reality, considering how hard the SURTASS ships have been harassed by the PLAN over the years.

The USN refitted them with a big Low Frequency Active sonar in the 2000s, so they're not exactly subtle anymore.

 

[johnpjones1775]

OK, didn't realize that HMS-X2 is a specific (indian) hull sonar.

As far as payload, I reiterate that the payload you describe is much too large for a Cyclone-sized hull. Phalanx weights several times as much as the 25mm mount that sits forward on the PCs. The USV you want replaces the RHIB. The crew served weapons are the same as the PC. And now we're starting to run out of weight and deck area for torpedo tubes, sonar, a UAV pad and hangar, etc.

If a mkVI boat can carry 2 mk38s and 4 NSMs I’m sure something roughly size of a cyclone can manage to fit everything I mentioned

 

[Scott Kenny]

If a mkVI boat can carry 2 mk38s and 4 NSMs I’m sure something roughly size of a cyclone can manage to fit everything I mentioned

A Mk38 weighs 2300lbs empty, maybe 2750lbs loaded. 4x NMSs in their launchers weigh about 5000lbs

Actually more like 8600 lbs with canisters, racks, and electronics.

(less than 900lbs/missile).

A Phalanx CIWS weighs 13,600lbs.

 

[johnpjones1775]

A Mk38 weighs 2300lbs empty, maybe 2750lbs loaded. 4x NMSs in their launchers weigh about 5000lbs (less than 900lbs/missile).

A Phalanx CIWS weighs 13,600lbs.

Great, and a mkVI boat weighs 1/5 of a cyclone…which is kinda the point I was making.

I’m going to need to see your sources a cyclone couldn’t carry phalanx considering the skjold class is smaller and mounts a 76mm, and 8 NSMs…

 

[TomS]

4x NMSs in their launchers weigh about 5000lbs

Actually more like 8600 lbs with canisters, racks, and electronics.

I question the basic assertion that a Mk VI can carry two Mk 38 and 4 NSM. With two Mk 38s, there is just barely room to squeeze in a pair of small RIBs. And bear in mind that the USN really wants to get rid of the Mk VIs because they are totally unsuited to the open Pacific. Now, translate to the requirement to operate off Ireland (North Atlantic) which is even worse. Even the Cyclones are really too small for an environment like that.

 

[johnpjones1775]

Actually more like 8600 lbs with canisters, racks, and electronics.

I question the basic assertion that a Mk VI can carry two Mk 38 and 4 NSM. With two Mk 38s, there is just barely room to squeeze in a pair of small RIBs. And bear in mind that the USN really wants to get rid of the Mk VIs because they are totally unsuited to the open Pacific. Now, translate to the requirement to operate off Ireland (North Atlantic) which is even worse. Even the Cyclones are really too small for an environment like that.

The boats carry 2 attached to the sides of the boats.
Surprised me too when I found that out.

 

[Scott Kenny]

Actually more like 8600 lbs with canisters, racks, and electronics.

I question the basic assertion that a Mk VI can carry two Mk 38 and 4 NSM. With two Mk 38s, there is just barely room to squeeze in a pair of small RIBs. And bear in mind that the USN really wants to get rid of the Mk VIs because they are totally unsuited to the open Pacific. Now, translate to the requirement to operate off Ireland (North Atlantic) which is even worse. Even the Cyclones are really too small for an environment like that.

I stand corrected. Didn't think it was 10x the weight of a single missile!

 

[TomS]

The boats carry 2 attached to the sides of the boats.
Surprised me too when I found that out.

Show me. I cannot find an example of this.

 

[Scott Kenny]

Great, and a mkVI boat weighs 1/5 of a cyclone…which is kinda the point I was making.

A ship 5x bigger in displacement cannot necessarily carry 5x the weapons.

A Cyclone carries one Mk38 up front and a second one on top of the deckhouse aft. Dropping an extra 5 tons on the bow will do ugly things to seakeeping, more waves over the bow and breaking the CIWS, if not breaking the bridge itself. Putting that extra 5 tons up a deck will do absolutely hideous things to stability.

The boats carry 2 attached to the sides of the boats.
Surprised me too when I found that out.

The only time I have ever seen RHIBs on the sides of a Mk6 is when the SEALs are actively deploying. Hop off the side of the Mk6 into the RHIB that's in the water, roll into the water off the side of the RHIB. Saves the SEALs a long drop into the water.

 

[johnpjones1775]

Show me. I cannot find an example of this.

Not sure they’ve ever done it.
Just what an active duty officer that’s done his whole career on small combatants informed me.

 

[johnpjones1775]

A ship 5x bigger in displacement cannot necessarily carry 5x the weapons.

A Cyclone carries one Mk38 up front and a second one on top of the deckhouse aft. Dropping an extra 5 tons on the bow will do ugly things to seakeeping, more waves over the bow and breaking the CIWS, if not breaking the bridge itself. Putting that extra 5 tons up a deck will do absolutely hideous things to stability.




The only time I have ever seen RHIBs on the sides of a Mk6 is when the SEALs are actively deploying. Hop off the side of the Mk6 into the RHIB that's in the water, roll into the water off the side of the RHIB. Saves the SEALs a long drop into the water.

I said nothing about RHIBs

Funny how the discussion shifted from roughly cyclone size, to an actual cyclone which I wasn’t talking about.

 

[Scott Kenny]

Funny how the discussion shifted from roughly cyclone size, to an actual cyclone which I wasn’t talking about.

Funny:

Great, and a mkVI boat weighs 1/5 of a cyclone…which is kinda the point I was making.

I’m going to need to see your sources a cyclone couldn’t carry phalanx considering the skjold class is smaller and mounts a 76mm, and 8 NSMs…

 

[Scott Kenny]

I said nothing about RHIBs

Ahem:

I question the basic assertion that a Mk VI can carry two Mk 38 and 4 NSM. With two Mk 38s, there is just barely room to squeeze in a pair of small RIBs. And bear in mind that the USN really wants to get rid of the Mk VIs because they are totally unsuited to the open Pacific. Now, translate to the requirement to operate off Ireland (North Atlantic) which is even worse. Even the Cyclones are really too small for an environment like that.

To which you replied:

The boats carry 2 attached to the sides of the boats.
Surprised me too when I found that out.

RIB=RHIB, depends on when you served as to which acronym was used.

 

[johnpjones1775]

Ahem:


To which you replied:


RIB=RHIB, depends on when you served as to which acronym was used.

Again I said nothing about RHIBs

I was talking about missiles.