Modern submarine chaser

Yes, I pointed out how a boat much smaller than a cyclone can carry a heavier load than a cyclone, therefore a vessel roughly the size of a cyclone can easily mount a phalanx on the bow.

If you look at post #9 the context of my use of the word cyclone is pretty clear.
 
Yes, I pointed out how a boat much smaller than a cyclone can carry a heavier load than a cyclone,
Smaller boats always have a greater weapon:size ratio than larger boats, which greatly complicates the comparison. Larger ships have longer endurance, which means more food, fuel, and spare parts, plus more habitable space for the crews.


therefore a vessel roughly the size of a cyclone can easily mount a phalanx on the bow.
Maybe. If designed for it. And it's still going to be wave-beaten in bad weather, which tends to break things really hard.

You want to stick a CIWS up as high as you can to give the longest radar horizon, despite the ugly things that does to your stability. Look at where the CIWS are placed on US ships: Burke, one or two decks above the main deck. LCS, on top of the hangar.

I'd do a diesel-electric with a gas turbine electric for ~35knot sprint speed (nuclear subs are fast). All heavily rafted for silence. Stick all the generators down in the bilge for stability purposes. CIWS on top of the hangar for field of view/fire. Hangar and flight deck big enough for a Seahawk at a minimum, better if we can stuff an EH101 Merlin in there (greater export possibilities that way). Bofors 57mm Mk110 on the bow, we know that turret can take waves. Surface and VDS towed arrays. Whatever radar the host country uses most, the display model would use Sea Giraffe. Needs an EOTS as well, ideally something like the F35 DAS but that's stupid expensive right now.

And crap, that's really close to an LCS without the stupidly high speed requirements.


Cool, not what I was talking about.
So, you meant that MkVIs carry 2x NSMs on each side?
 
Worth pointing out that the Project 1214.2 Pauk, a Soviet subchaser whose main ASW sensor is a helicopter dipping sonar, is slightly bigger than the Cyclone-class, and displacement is increased by 75%.

Once you start accounting for improved accommodation (I assume most countries would want living conditions better than "1970s Soviet Subchaser"), and LO shaping, you are going to end up with something bigger.

How much silencing for ASW does a Sa'ar 5 have, and how much can actually be accommodated on a hull that size? I think that would be a much better base for any kind of Brown Water Small Anti-Submarine Ship, although I'd probably want something bigger for Blue Water work.
 
Worth pointing out that the Project 1214.2 Pauk, a Soviet subchaser whose main ASW sensor is a helicopter dipping sonar, is slightly bigger than the Cyclone-class, and displacement is increased by 75%.

Once you start accounting for improved accommodation (I assume most countries would want living conditions better than "1970s Soviet Subchaser"), and LO shaping, you are going to end up with something bigger.

How much silencing for ASW does a Sa'ar 5 have, and how much can actually be accommodated on a hull that size? I think that would be a much better base for any kind of Brown Water Small Anti-Submarine Ship, although I'd probably want something bigger for Blue Water work.
You can get away with a smaller subchaser in the Baltic or even in the Pacific than you can in the North Atlantic. Since the inspiration for this discussion was Ireland, I'm building for Winter North Atlantic.
 
DK Brown did draw up a Castle-class OPV-derived towed array tugs, but that wasn't really a stand-alone Subchaser, but part of a larger system including MPAs, and ASW Helicopters operating from other ships (the towed-array tug had a flight deck, but not a hangar). Giving it a self-defence capability brought it up to Type 23 cost. He was of the view that there was a gap in viability between a certain cost range for warships.

If the main limit is seakeeping, and you really wanted to hold down size (although I don't know why you would), maybe SWATH would be viable?
 
DK Brown did draw up a Castle-class OPV-derived towed array tugs, but that wasn't really a stand-alone Subchaser, but part of a larger system including MPAs, and ASW Helicopters operating from other ships (the towed-array tug had a flight deck, but not a hangar). Giving it a self-defence capability brought it up to Type 23 cost. He was of the view that there was a gap in viability between a certain cost range for warships.

If the main limit is seakeeping, and you really wanted to hold down size (although I don't know why you would), maybe SWATH would be viable?
Not trying to hold down size so much as cost.

And yes, a SWATH would definitely work. That's what the USN built for their ultimate SURTASS ships, and the hulls could easily support a big helicopter deck as the Victorious class is 235ft long and 94ft abeam, while the Impeccable class is 282ft long and 96ft abeam. The ships are pretty slow, however, they only do 10-12 knots.

I'm just not seeing any prices for those ships, which annoys the hell out of me.

Something like a Victorious class SWATH hull is a solid foundation. Just needs to add basic self defense systems (chaff, jammers, etc), helicopter deck and hangar with 1x AW139 and a drone big enough to carry 600lbs of torpedo, and a gun to warn off poaching fishing boats. That gun could be a CIWS, since they do have a manual/surface attack mode now, it could also be up to a Mk110 57mm. I'm skipping ESSMs and the FCS to use them on cost grounds. The Victorious class also only needs a crew of 19, add another 10 for the aviation detachment and 3 for the gun for a total of 32 crew, so that will help with manning the beast.
 
Smaller boats always have a greater weapon:size ratio than larger boats, which greatly complicates the comparison. Larger ships have longer endurance, which means more food, fuel, and spare parts, plus more habitable space for the crews.



Maybe. If designed for it. And it's still going to be wave-beaten in bad weather, which tends to break things really hard.

You want to stick a CIWS up as high as you can to give the longest radar horizon, despite the ugly things that does to your stability. Look at where the CIWS are placed on US ships: Burke, one or two decks above the main deck. LCS, on top of the hangar.

I'd do a diesel-electric with a gas turbine electric for ~35knot sprint speed (nuclear subs are fast). All heavily rafted for silence. Stick all the generators down in the bilge for stability purposes. CIWS on top of the hangar for field of view/fire. Hangar and flight deck big enough for a Seahawk at a minimum, better if we can stuff an EH101 Merlin in there (greater export possibilities that way). Bofors 57mm Mk110 on the bow, we know that turret can take waves. Surface and VDS towed arrays. Whatever radar the host country uses most, the display model would use Sea Giraffe. Needs an EOTS as well, ideally something like the F35 DAS but that's stupid expensive right now.

And crap, that's really close to an LCS without the stupidly high speed requirements.



So, you meant that MkVIs carry 2x NSMs on each side?
Yep
 
DK Brown did draw up a Castle-class OPV-derived towed array tugs, but that wasn't really a stand-alone Subchaser, but part of a larger system including MPAs, and ASW Helicopters operating from other ships (the towed-array tug had a flight deck, but not a hangar). Giving it a self-defence capability brought it up to Type 23 cost. He was of the view that there was a gap in viability between a certain cost range for warships.

If the main limit is seakeeping, and you really wanted to hold down size (although I don't know why you would), maybe SWATH would be viable?
Larger ship will require larger crew if only more BMs to do paint and preservation on the ship.
 
Larger ship will require larger crew if only more BMs to do paint and preservation on the ship.
Or grabbing a bunch of dudes from wherever to apply paint while in port... For most anyone looking at a subchaser, short patrols of 2-3 weeks and back in.
 
And what about DC?
Small crews on large ships is how you end up like the moskva
Moskva ended up like it did because of a combination of the lack of smoke control (which any Western warship designed with the experience of the Falklands war should have) and lack of breathing apparatus, which led to smoke from the fires caused by the Neptune strike to incapacitate much of the crew, build-up of fire-fighting water, progressive flooding from scuttles and bulkhead glands, and a long low-lying quarter deck (common to many Soviet warships) which led loss of buoyancy when submerged.

Notably Moskva didn't have a small crew, she had a relatively large one, around double that of a modern DDG.

Moskva, and other Soviet warships in general, are not designed with a "steel is cheap and air is free" mindset, they tend to be very densely packed. The Slava-class were designed as cheaper Gas-Turbine powered alternatives to the Kirov-class, if anything they're smaller than they should be.
 
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In the absence of a developed ASROC (Sea Lance?) the main weapon against hostile submarines is a helicopter.
Shore based helicopters can also be used for Search and Rescue.
Working with longer ranged Maritime Patrol aircraft (MPA) they provide effective coverage without the cost of ships.
A decent ASW escort like the T23 or George Leygues is only necessary for a blue water navy.
 
In the absence of a developed ASROC (Sea Lance?) the main weapon against hostile submarines is a helicopter.
Shore based helicopters can also be used for Search and Rescue.
Working with longer ranged Maritime Patrol aircraft (MPA) they provide effective coverage without the cost of ships.
A decent ASW escort like the T23 or George Leygues is only necessary for a blue water navy.
However, a towed-array ship with a helo deck is very generally useful. Fisheries enforcement (just saw an article that combined vessel transponder data with satellite, and revealed that some 75% of world fishing fleets do not operate a transponder), search and rescue, etc ad nauseam.

Remember that you're talking about 200nmi offshore for your EEZ area, which is a bit of a reach for any helicopter without inflight refueling.
 
Thinking more about it, I think the city class MCM could be easily adapted as a sub chaser.

Larger than i was originally thinking, but it seems it would be the most realistic option for a modern western sub chaser.
 
Thinking more about it, I think the city class MCM could be easily adapted as a sub chaser.

Larger than i was originally thinking, but it seems it would be the most realistic option for a modern western sub chaser.
That may actually be a really good hull to work from, for people not worried about the Winter North Atlantic.

It's got the power to two long arrays or paravanes, it's got a minimal sonar and magnetic signature from being a minesweeper base. 15 knots isn't terrible, but definitely isn't going to be able to get ahead of a nuke boat to corral it.

But it's only got a UAV deck instead of a full helo deck/hangar. That might be adjustable, lose some of the USV and minesweeping gear for better aviation capabilities.
 
That may actually be a really good hull to work from, for people not worried about the Winter North Atlantic.

It's got the power to two long arrays or paravanes, it's got a minimal sonar and magnetic signature from being a minesweeper base. 15 knots isn't terrible, but definitely isn't going to be able to get ahead of a nuke boat to corral it.

But it's only got a UAV deck instead of a full helo deck/hangar. That might be adjustable, lose some of the USV and minesweeping gear for better aviation capabilities.
Considering they have relatively small quadcopter drones that can carry fairly small torpedoes now, loading a few up with sonobuoys shouldn’t be an issue.

Have 2 on standby with torpedoes, while 4-6 drop buoys.
 
Considering they have relatively small quadcopter drones that can carry fairly small torpedoes now, loading a few up with sonobuoys shouldn’t be an issue.

Have 2 on standby with torpedoes, while 4-6 drop buoys.
Understand that an airdropped torpedo is some 800lbs (600lbs of weapon plus 200lbs of parachute pack). I haven't seen a good number for sonobuoys but I'd suspect in the 200lb range, which means that any given drone is only packing about 4-6 Sonobuoys.

What I'm getting at is that having full size helicopter facilities is a lot more generally useful than even 6-8x MQ-8B or bigger drones. Not for hunting subs, but for all the other stuff you send a ship out to do in the ocean.
 
I haven't seen a good number for sonobuoys but I'd suspect in the 200lb range, which means that any given drone is only packing about 4-6 Sonobuoys.

L3 Harris has made a sonobuoy dispenser pod that has been demoed on the MQ-9B. It can dispense 10 full-size sonobuoys or 20 dwarf buoys. Loaded, it weighs in at about 750 pounds. (A Mk 54 torpedo is about 610 lbs, plus parachute pack)


So, that tells us that we need a drone with a payload on the order of 750 lbs and an endurance of a couple of hours minimum to lay buoys and prosecute the findings. That's not commonplace, yet. The BAE/Malloy T-600 managed to drop a Stingray torps in an exercise recently but it is credited with a nominal payload of only 440 lbs (200 kg) so it was very much overloaded. The new T-650 might be closer.

The alternative is to switch to an ultralight torpedo like the ones the USN is interested in for counter-UUV and anti-torpedo roles. But they are pretty borderline for actually attacking a sub on open water.
 
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L3 Harris has made a sonobuoy dispenser pod that has been demoed on the MQ-9B. It can dispense 10 full-size so obvious or 20 dwarf buoys. Loaded, it weighs in at about 750 pounds. (A Mk 54 torpedo is about 610 lbs, plus parachute pack)

Okay, that probably puts the buoys at 50-60lbs each. Which is obviously good, since it allows drones to carry more.



The alternative is to switch to an ultralight torpedo like the ones the USN is interested in for counter-UUV and anti-torpedo roles. But they are pretty borderline for actually attacking a sub on open water.
Frankly, even a Mk46/50/54/Stingray/etc is marginal against subs in open water. Range is just horribly short so all the sub does is run for ~10 minutes.

I'm starting to think that the next airdropped torpedo is going to be something approaching the size of a Mk48 (3700lbs/1700kg), or at least a Mk37 (1450lbs/650kg). Simplest option is a Mk54 with a double-sized (~20km range) or triple-sized (~30km range) fuel tank.
 
Okay, that probably puts the buoys at 50-60lbs each. Which is obviously good, since it allows drones to carry more.




Frankly, even a Mk46/50/54/Stingray/etc is marginal against subs in open water. Range is just horribly short so all the sub does is run for ~10 minutes.

I'm starting to think that the next airdropped torpedo is going to be something approaching the size of a Mk48 (3700lbs/1700kg), or at least a Mk37 (1450lbs/650kg). Simplest option is a Mk54 with a double-sized (~20km range) or triple-sized (~30km range) fuel tank.

Mk 54 Mod 2 reverts to the SCEPS power plant like the old Mk 50. That was a real screamer, supposedly. And a deep diver as well.
 
Mk 54 Mod 2 reverts to the SCEPS power plant like the old Mk 50. That was a real screamer, supposedly. And a deep diver as well.
It's not speed and depth that you necessarily want, it's endurance while at speed.
 
It's not speed and depth that you necessarily want, it's endurance while at speed.

Speed helps, though. Having a 20-knot speed advantage makes the "no escape" zone a lot larger than a 10-knot edge. And Mk 50 was credited with about 50% more range than the Mk 54. If that translates into Mk 54 Mod 2, it's going to have a lot better odds of running down a sub than its OTTO-fueled predecessor.
 
Speed helps, though. Having a 20-knot speed advantage makes the "no escape" zone a lot larger than a 10-knot edge.
depends on how fast the target sub accelerates. Rumor has it that Seawolf-class can run a Mk48 out of endurance if it's not launched within 4500y of them.

And Mk 50 was credited with about 50% more range than the Mk 54. If that translates into Mk 54 Mod 2, it's going to have a lot better odds of running down a sub than its OTTO-fueled predecessor.
Okay, that's a worthwhile add.

Just ironic that the Mk54 is the Mk50 sensors and warhead on the Mk46 engine/afterbody, so Mk54mod2 is just a Mk50 again.
 
As I understand it the purpose of subchasers as opposed to full ASW frigates/DEs is cheapness & numbers. This does not really mesh with the demands of modern ASW. However, there are some things that can be done. Take a small costal freighter like this coaster from DAMEN. Modify the design with a COTS gas turbine, electric transmission driving twin screws and a finer bow for more speed (20 or so knots). Use the hold for a big capstan trailing a VDS (running it around the superstructure) There's room left over in the hold for helicopters and 1 or 2 lifts (not the big frontline jobs but something like the McDonnell Douglas MD 500 Defender's ASW version). It's big enough to hold 8-10 of the things, and those are going to be the main ASW weapon. These birds are not NEARLY as effective as a proper frigates helicopter, but they are fairly cheap and multiples could be kept on station. The hold is deep enough and the deck is broad enough that a VLS could be installed and still not interfere with landing/takeoff. However, a VLS nest would kind of defeat the purpose because you'd need a fire control system of some kind and the missiles would cost more than the ship. If that must be done, I'd suggest putting 2 fighter radars on the thing (much as was envisioned for Sea Phoenix). The only other militarization needed would be silencing, (which if you're using a gas turbine and electric drive should not be challenging) and turning the lower hold over to fuel and ASW torpedoes (which, we need to remember are obscenely expensive/ slow to build right now). This vessel is small enough & simple enough to be built in mid-sized commercial yards and presumably could be cranked out quickly. The weapons would be the helicopters, CIWS, bolt on fire control and possibly a vls installed in the hold. One could probably put dozens of the things in the water in a few years.
 
Another option would be to modify a big Offshore crew transport vessel. This would have much of the same benefits, not need any re-design for speed, but would not enjoy the same deep hold capacity for helicopters & drones, but the broad deck would allow helicopter operations, maybe 2-4 MD500s in hangars and some drones in the hold. A towed VDS would need to be worked in as well and deck space would need to be found for CIWS.

This more austere option has the benefit, at least here in the US, that there are a LOT of shipyards set up in and near the gulf of Mexico that than build these things. I suspect that there is a similar situation in northern Europe.
 
As I understand it the purpose of subchasers as opposed to full ASW frigates/DEs is cheapness & numbers. This does not really mesh with the demands of modern ASW. However, there are some things that can be done. Take a small costal freighter like this coaster from DAMEN. Modify the design with a COTS gas turbine, electric transmission driving twin screws and a finer bow for more speed (20 or so knots).
4500t isn't really small, it's the size of a frigate, historic sub-chasers have been under 1000t. (China's Hainan Class, 430t, Russia's Pauk class 500t)

And I'm not sure your concept is particularly cheap.

Damen Combi-Freighter 4500: $10m (scaling down from $11.5m for a Combi-Freighter 5000)

Based on comparable sized ships, I'd guess you need around 15,000Kw for 20kts, which is pushing up towards an LM-2500. That's about $10-12M for the engine alone.

8-10 MD-500s: minimum of $15m, probably more like $25m with minimum equipment

VDS: $5-10m

2 Fighter radars: $20m (Blue Vixen was estimated at $5m in 2003

CIWS: $10-15m

Minimal VLS + Missiles: $5m?

Total: Somewhere in the region of $75-110m
 
Another option would be to modify a big Offshore crew transport vessel. This would have much of the same benefits, not need any re-design for speed, but would not enjoy the same deep hold capacity for helicopters & drones, but the broad deck would allow helicopter operations, maybe 2-4 MD500s in hangars
It's a 325t design, the deck is roughly 10x22m. An MD 500 is 10m long with a 10m rotor span - you can't fit two on that vessel never mind 4, there's barely room for one. There's a reason subchasers don't carry helicopters and even frigates and destroyers only carry one or at most two helicopters. Even the MD 500 is only slightly smaller than a Wildcat or a Panther and there's just not the space on a small vessel.
 
As I understand it the purpose of subchasers as opposed to full ASW frigates/DEs is cheapness & numbers. This does not really mesh with the demands of modern ASW.
Correct.


However, there are some things that can be done. Take a small costal freighter like this coaster from DAMEN. Modify the design with a COTS gas turbine, electric transmission driving twin screws and a finer bow for more speed (20 or so knots).
Finer bow would also require a finer stern, that's a big redesign.


Use the hold for a big capstan trailing a VDS (running it around the superstructure) There's room left over in the hold for helicopters and 1 or 2 lifts (not the big frontline jobs but something like the McDonnell Douglas MD 500 Defender's ASW version). It's big enough to hold 8-10 of the things, and those are going to be the main ASW weapon. These birds are not NEARLY as effective as a proper frigates helicopter, but they are fairly cheap and multiples could be kept on station.
No, an MD500 requires a 10m clear flight deck (and would need folding rotors to not need a 10x12m hangar spot).

You're not sticking more than maybe 4 of those into a 4500 ton ship.


The hold is deep enough and the deck is broad enough that a VLS could be installed and still not interfere with landing/takeoff. However, a VLS nest would kind of defeat the purpose because you'd need a fire control system of some kind and the missiles would cost more than the ship. If that must be done, I'd suggest putting 2 fighter radars on the thing (much as was envisioned for Sea Phoenix).
Nah, stick with CIWS and/or SeaRAM, which is mostly self-contained and doesn't need any other radars added.


The only other militarization needed would be silencing, (which if you're using a gas turbine and electric drive should not be challenging)
You'd be shocked at how hard that is. Especially if you get a funny resonance at 59.8Hz or something similarly unexpected. (Actual example, unique to one ship in a class. No, you don't need to know which class, just that none of the other ships in the class have that hum.)


and turning the lower hold over to fuel and ASW torpedoes (which, we need to remember are obscenely expensive/ slow to build right now). This vessel is small enough & simple enough to be built in mid-sized commercial yards and presumably could be cranked out quickly. The weapons would be the helicopters, CIWS, bolt on fire control and possibly a vls installed in the hold. One could probably put dozens of the things in the water in a few years.
While the necessary silencing would not be anywhere near as easy as you expect it to be, and you wouldn't have anywhere near as many helicopters as you think, overall this isn't bad.
 
It's a 325t design, the deck is roughly 10x22m. An MD 500 is 10m long with a 10m rotor span - you can't fit two on that vessel never mind 4, there's barely room for one. There's a reason subchasers don't carry helicopters and even frigates and destroyers only carry one or at most two helicopters. Even the MD 500 is only slightly smaller than a Wildcat or a Panther and there's just not the space on a small vessel.
It should be no more than 8 feet wide folded
 
Trying to do ASW on the cheap given the state of the art on subs is, indeed, a desperation move. However, I'm pretty sure that the MD 500 can be carried in some numbers, its height is about 9 feet, its landing skid width is 6.45 feet, its fuselage width is 4.57ft so there should be enough room between two of the things parked so close that the skids are nearly touching to do basic maintenance. The fuselage length is a tad under 24 feet. I'm pretty sure that a folding rotor version is available, the Taiwanese used them on their FRAM destroyers using the old DASH hangar IIRC. If it is not then a folding rotor arrangement should be able to be implemented given enough lead time for what is a mobilization program. MD 500 is not in the same league as a Seahawk for effectiveness but carrying 4 would allow an SC to have one always on station most of the time. For a vessel no bigger than a big FAC this would seem to be a game changer, however, I have no idea how long even one of these austere whirlly-birds takes to make. They could be a serious production bottleneck.

I tend to agree that a missile suite it not realistic for what is a mass production "lilly-pad" anything beyond a SEA-RAM or two & crew served weapons is probably unrealistic, even a MK 57 is probably too much.

Regarding silencing I di indeed know very little about it, other than it's almost as much art as science. I was thinking about a proposal by the late D.K. Brown for a costal minesweeper, where the powerplant was a gas turbogenerator in something like a shipping container, physically isolated from the hull by foam or such, transmitting power to electric motors with short shafts.

I'm not proposing converting existing vessels, but using C.O.T.S. designs as starting points for stuff that can be built in generally civilian yards.

Thanks a lot for all the feedback!
 
It should be no more than 8 feet wide folded
That doesn't make any difference, I'm afraid, the deck is only big enough to take one with rotors spread. Remember, even D K Brown's 1,600t Castle Class, with a flight-deck sized for Sea King or Merlin could only take one helicopter, and that only for refuelling, there was no room for a hangar.
 
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.
One would have thought so yes. However our politicians have had other more pressing priorities (to them at least).

On a tangent:
Were we to lose US support we are in a reasonable position here – as should always have been the case. The Americans are our friends but nobody likes a friend who can’t look after themselves and never lends a hand. We need more of everything, of course, but what we do have is good: and we lend a hand when we can, as in the case of British strikes alongside America against the Houthis.

This is far more than can be said for the Irish, who can’t do anything for themselves – or worse, can’t be bothered to and assume someone will do it for them.

Ireland’s Defence Minister is on record as saying:

“Ireland will never be in a position really to engage in [anti] submarine warfare”.

This backwards-leaning stance sits at odds with his Defence Force’s mission statement for the navy which states, “Defence roles include defending territorial seas, deterring intrusive or aggressive acts, conducting maritime surveillance, maintaining an armed naval presence, ensuring right of passage, protecting marine assets…”

He’s right though. Ireland has no frigates or submarines. It claims to have two “maritime patrol aircraft”, Airbus C295s, but these are not Poseidons: they are unarmed fishery patrol planes with no underwater capabilities.

Ireland uses fossil fuel for 86 per cent of all its energy. The Corrib field is Ireland’s only domestic source of fossil fuel: as such it is “critical infrastructure” indeed. Given the fact that Ireland is also totally, abjectly dependent on imports of oil and gas by ship, and that it gets around ten per cent of its electricity by undersea cable, it is clear that Ireland absolutely cannot survive for long if a hostile actor gets control of its undersea environment.

The Irish navy’s stated role is to provide that protection and control but the minister in charge says that he can’t do it. Ireland has a GDP larger than Norway’s – and yet here it is, reliant on Norway’s real maritime patrol aircraft to help defend it.

The difference is that the Norwegians are not freeloaders.
 
What you need is something like the Mexican Oaxaca-class OPV. Already has space for a helo on 1,700t. Replace the interceptor boat with a sonar suite, throw on a few torpedo tubes and some handheld SAMs and call it good.
 
Understand that an airdropped torpedo is some 800lbs (600lbs of weapon plus 200lbs of parachute pack). I haven't seen a good number for sonobuoys but I'd suspect in the 200lb range, which means that any given drone is only packing about 4-6 Sonobuoys.

What I'm getting at is that having full size helicopter facilities is a lot more generally useful than even 6-8x MQ-8B or bigger drones. Not for hunting subs, but for all the other stuff you send a ship out to do in the ocean.
I'm late to this party and haven't read all the way through, but the standard dispenser (LAU-126/A) is rated for any A-class store, between 10-40 lbs. The newest sonobuoys (Q-125) are about 36 lbs.

I think the breakthrough is going to do all the processing on the ship or on the P-8, or even on shore, while using anything and everything from P-8's, MQ-9's, to Helos, to lay patterns for you and relay the data back for processing. Same with ships with sonar (or even USV's with that function). Let it all get collected at the flag ship. That all takes bandwidth though, which won't always be available. For patrolling one's own coast though, probably sufficient.

Something of the Moskva configuration and function at about 75% size with accommodation for maybe 8 helos you can use to lay patterns and relay data back to process and manage a relatively large zone as the ASW flagship. And then prosecute with the helos or whatever other platform can get there the fastest.

You can't chase subs anymore without air, imo. If you put a capable ASW flag with a frigate or two, you should be golden. For "green water" patrols, you can supplement with more traditional multipurpose patrol ships (200-400 ton) with sonar to collect more data and make an annoyance of themselves.

The farther out in blue water you push, the less time you have for shore-based air (P-8's, MQ-9, helos) on station. Then you need more organic air, and you essentially end up with a full-size Moskva because you need more coverage and will inevitably have broken birds needing fixing.

There's a reason no-one uses small subs chasers anymore.
 
Given the way the fast Irish Sea ferries suffer badly when a 'Big Westerly' roars in, with the open Atlantic at least thrice worse, superb sea-keeping would seem the first priority, with dash-speed a close second...

Actually doing sub-hunting runs a poor third to being there...

I noticed a comment above about rig supply ships, designed for a brisk commute regardless of unkind, in fact 'scary-hostile' sea-states...

Seems we're looking for a hull-form that would be 'comfortable' in the 'Roaring Forties', at ease in the 'Drake Passage'...

Getting the c/g low must be a priority:
Seems silly, but is there any way to fit a 'disappearing turret' to fore-deck ?
A 'useful' CIWS or quick-firer is a hefty lump, lowering roof even deck-flush must improve ship stability...
 
I'm late to this party and haven't read all the way through, but the standard dispenser (LAU-126/A) is rated for any A-class store, between 10-40 lbs. The newest sonobuoys (Q-125) are about 36 lbs.
Thank you for that!

So a drone that is either packing a LWT or Sonobuoys could reasomably carry ~15-20 sonobuoys. That's a reasonable number for a single screen line, maybe 2.

You can't chase subs anymore without air, imo. If you put a capable ASW flag with a frigate or two, you should be golden. For "green water" patrols, you can supplement with more traditional multipurpose patrol ships (200-400 ton) with sonar to collect more data and make an annoyance of themselves.

The farther out in blue water you push, the less time you have for shore-based air (P-8's, MQ-9, helos) on station. Then you need more organic air, and you essentially end up with a full-size Moskva because you need more coverage and will inevitably have broken birds needing fixing.

There's a reason no-one uses small subs chasers anymore.
I'm not sure a 200-400ton ship could have enough sonar to be worth the effort needed to silence it.

Let's go ahead and aim for a ~2000ton ship (or bigger, Perry class were 4000tons) that can carry a full sized helicopter for ASW, but more importantly SAR and generally flying around and chasing fishing boats out of your EEZ.

And give it a QH-50 sized UCAV to carry sonobuoys or a torpedo to drop, in weather that's too nasty to launch the manned helicopter.



Given the way the fast Irish Sea ferries suffer badly when a 'Big Westerly' roars in, with the open Atlantic at least thrice worse, superb sea-keeping would seem the first priority, with dash-speed a close second...

Actually doing sub-hunting runs a poor third to being there...
I think I'd rather have superb quieting over high dash speed, but being able to do ~35knots is a likely requirement. Don't need to be an LCS and do 40 knots.



I noticed a comment above about rig supply ships, designed for a brisk commute regardless of unkind, in fact 'scary-hostile' sea-states...

Seems we're looking for a hull-form that would be 'comfortable' in the 'Roaring Forties', at ease in the 'Drake Passage'...

Getting the c/g low must be a priority:
Seems silly, but is there any way to fit a 'disappearing turret' to fore-deck ?
A 'useful' CIWS or quick-firer is a hefty lump, lowering roof even deck-flush must improve ship stability...
Yes, one of those rig supply ships is probably the best hull type. Just need to do a whole lot of quieting to make the hull and towed sonars work well.

The OTO 76mm has a non-penetrating turret option (Sovraponte) that weighs about as much as the Phalanx CIWS, that's what I'd stick on the modern sub-chaser/OPV. The base OTO 76mm installation is ~7.5 tonnes, but the Sovraponte is ~30-40% lighter, so ~5 tonnes. An early Phalanx is ~5700kg. That's an unloaded weight for the Sovraponte, but 76 rounds of 12.5kg each is 950kg, making a total of about 6 tonnes. The downside to the OTO 76mm is that it needs a separate radar/fire control, while Phalanx is all integrated.
 

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