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Sometimes I wonder if we are looking at ASW in the wrong way. Sonar looks for noise, metal etc and the RN is good at it, but what happens if we look for silence, or use green light laser to build trip nets, and what about using underwater current to recharge the batteries of dropped sonar systems. Possibly this is the future of ASW sensor platforms.


‘look for silence’….? ‘green light laser’….? ‘using underwater current to recharge the batteries’…? if you think each of these things through, I think you will find that none of them will work…

For example, ‘green light laser’ – light is *very* quickly absorbed/blocked underwater, so fairly useless for anything. Just ask anyone who has ever been scuba diving, especially in the UK… In order to provide any kind of charging power, an underwater turbine will need to be in a fixed position for a reasonable length of time, which means fixing the sonar buoys to the sea bed or some other object which is itself fixed to the seabed, which is not possible for these disposable items. Have a look online at technologies for generating power from ocean currents. As for listening for silence, hmm….

Rob Cameron

I think you’re being a bit harsh. For instance I think Ron may be thinking about using salt water battery technology (as has been used in Stingray torpedoes for a couple of decades). Maybe this has been thought of and can/cannot yet be utilised. But, the boffins have to keep coming up with new ideas- it’s the nature of the game. Given the proliferation of very quiet SSKs in the last 20 years, I really hope that the RN does get more kit, that is effective.


What isn’t mentioned here is what the opposition are up to. It seems fairly obvious that if the software and autonomous vehicles improve the searchers capacity similar technology could be used by the other side. So in the above scenario we have various platforms bussilly listening and triangulating utilising active and passive sonars which are then filtered by very clever software to locate subs. However, as discussed above, the actual platforms that can then engage the targets are limited. If I were the opposition I would be bussilly developing autonomous decoy vehicles to swamp the system with false noise / contacts. I’m not talking about torpedo decoys but long range dummy unmanned submarines creating plenty of chuff confusing and drowning out the search sonars. What then?


So first, green light laser, I am well aware of the light spectrum and sorry but I am a deep sea diver, bring on the armour and heating, all of it in cold water, Brrr, but also I am a communications specialist, signals for me is my home ground. I have some very good friends in Poland who are Proffesors in this type of technology. We even argued out the concept of using green light laser to create a tube for red light laser to pass through in the atmosphere to burn of humidity to stop red laser at high energy output bloomin. Green light laser is especially designed for usage in water. Yes it has a short range, one-two miles max but they are still developing the tech. Link these into a chain then you have a silent trip wire. These guys were looking at it for underwater navigation, you know red routeone stuff.
Batteries, again it is a technology development, sonar bouys move, not much but they move, movement creates energy, just think of your dive watch, there are no batteries, well at least not on mine, movement of the wrist keeps it ‘charged’. There is also the possibility to redesign the rebreather concept for energy. Also think about Japan and the Long Lance Torp. Then again how about a simple mini turbine, propelled by the current just to recharge batteries. Yes I agree there is work to be done but please remember you need to start somewhere. Modern electronics no longer need 12 vols and Amps or milli Amps, but micro Amps and 0ne or two volts to keep them ticking over.
Then there is the simple salt water battery, some zinc, copper and a bloody big ocean, it will be a trickle feed sure, but develop it and who knows.
As for my suggestion of looking for silence, you said you are a diver, tell me is the ocean quiete, no its not. Modern subs are so quiete they create almost a black hole in the back ground noise, so with that being the case then maybe we should look for that. Yes I know its a damned big ocean, but again its future concepts not past developments.
I agree that the ideas are ‘out there’ but with out ideas would we have any of our modern tech?

Meirion X

I sure the sea creatures & fish, make some noise, especially when disturbed by man made vessels, to make the oceans Not truly quite at all!
You can only have a true black hole of sound in the ocean, if something is sucking up noise, I don’t think that is possible at the moment.
Of cause, you could have an area of sea were most sea creatures have been scared off temporary by a sub.

Also the RN needs a long range VL-ASROC warpon.

Will O

Green laser water penetrating Lidar is already being developed & used, see the link below;


Eastern red sea Bottom Topograpghy fully Lidared! (y)


That back hole analogy is a good one. It also shows why using silence is actually near impossible. We actually detect celestial black holes using it’s emissions, otherwise we couldn’t see anything through the natural background noise. Most sound dampening/absorbing systems I know convert sound into heat.

Another method is how light bends because of gravity. This might work since I know sound barriers can actually amplify noise if your at the wrong spot. A large submarine might have the same effect. It would probably be like MAD (Magnetic Anomaly Detector) but in the acoustic domain. With enough computational power, it might work.


Should we be discussing some of this in such a public place, I dont know?


Spot On Ron, In the Marine Seismic industry Seabed Nodes have rechargeable batteries that are getting close to 100 days duration… Induction charging is also used in other applications eg Cable levelers for Towed streamer seismic… AUVs are already being trialed in “Swarm” mode … open source as mentioned above allows for quick adaption to mil requirements … i guess if the budget is there most things are possible.

Kevin Hastie

I never appreciated how much space is needed to accommodate ASW towed array; thats why you cant just bung it on the end of a OPV……which is a shame because it would be a useful role…

Dave G

Is the water where your expect an opv to operate deep enough for a towed array to be used effectively?


Or OPVs have enough range to traverse the Atlantic…

Dave G

Range yes but what about expected operational area. If it is likely to be wanted to operate in giuk gap or mid atlantic then ok. If it is primarily for use in north sea and northern and western approaches to uk (freeing up the frigate based at home), just off the falklands and in the Persian gulf for eg. Is the water deep enough?


The Gulf isnt deep enough. 60 odd meters in most places. With all the bottom debris from the oil industry it will snag and catch almost anything you put down there.
It is just as easy to see a Sub using a Camera and some specialist polarising filters.

Simon m

Lightweight and small towed array that could pretty much go on anything were on display at DSEI 2019 not sure how mature/proven the technology. But it likely to happen soon


Exactly. There was an Israeli firm showing off a small, cheap towed array sonar that can be operated from patrol boats. Uses a thin wire, so does not need a huge winch. It would take up little room on a batch 2 River OPV & would be great as an extra bit of coastal ASW deterrence. i.e. keeping foreign subs away from Faslane.


DSIT Solutions, part of Rafael, Swordfish towed array sonar. Only needs a light winch. Shown off at Pacific 2019. A short article is on the Monch news website.

Bloke down the pub

When you need an extra set of ears in the water, without using throw-away sonar buoys, a towed array on an opv ,or vessel of opportunity such as an offshore supply vessel, is just what is called for. The Canadian Navy, along with Elbit subsidiary Geospectrum , have been working on a containerised system that does just that.


Towed array is not plug and play. S 2087 handling equipment is huge and the power requirements for the transmitter are not small either it needs 600v. The change from the legacy passive 2031 to 2087 required a huge change in the quarter deck structure and power supplies to that part of the vessel. It was major refit work.

Dont forget the other bits of string on the quarterdeck…there will also be a S2091 decoy system on the stbd side that needs to go out as well.

Bloke down the pub

No one is talking about fitting a 2087 on an opv but there are plenty of systems in development which are plug and play and are designed for smaller vessels. Any time that a T23/26 can be relieved from coastal duties by a smaller, cheaper vessel has got to be a good thing for the Navy’s global reach. BTW, Geospectrum’s TRAPS system incorporates a decoy system, thereby removing the need for extra ‘bits of string’.

Wise Old Owl

Geospectrum TRAPS decoy system is ‘Vapourware’. There is one in S2170.
Source Level of TRAPS is the same as an active sonobuoy – not a Frigate level solution for a Tier 1 Navy.


Good article. Couple of comments on issues not discussed… But significant force multipliers without additional hulls or airframes.

1. ASROC. Preferably the Japanese version that is significantly longer range / quicker than the current US version
2. Wildcat dipping sonor
3. Wildcat sensor data link
4. Data link comand and control links between vessels



Adding FLASH to Wildcat (in some miniaturised form) would require a significant avionics upgrade to avoid a 3rd crew member and allow the Observer to operate and ‘fight the battle’ from the LH seat. Otherwise it’s endurance would be greatly curtailed by the extra weight. Not impossible and hugely useful, but I doubt the finances would be made available to make it a reality. Having said that I believe the South Koreans use it in this role (as the Dutch used their Lynx as mini dippers) but have found no information on endurance or weapon load.
And as for no Data Link/Rover capability on Wildcat, well that’s a travesty!


Original plans were for, and design full caters for, a dipping sonar fit. Spending cuts removed the capability from RN versions.

James Fennell

Don’t the South Korean Wildcats have dipping sonar?

Will O

ASROC/Type07 are at least a decade away, can’t happen till T26 arrives with Mk41s.
So is it worth fitting the Type 23s with MILAS in the meantime, being as the last is not scheduled to retire till around 2035?

Phillip Johnson

Ah! Multi statics. It is a lovely concept which goes back at least 30 years. Early trials were underway in the 90’s but lost its priority when the USSR imploded.
Simply it is separating the Sonar transmitter from the Sonar receiver(s) and then processing the data from multiple receivers to better localise a target.
It has a couple of problems:
1. You need to know moment by moment the exact position of your transmitter and receivers.
2. It is best used in defence of a fixed location, a force transiting at even 15 kns can leave a set field behind very quickly.
3. Like any system with an active component a submarine will hear the sonar transmission way beyond effective detection range.
Bi statics have the feel of working if everything is set up perfectly and an ASW force has the time to pursue a target. Which in turn assumes adequate numbers of assets on scene..


There’s a great deal of detection mentioned here but there seems to be a lack of engagement. Relying on a helicopter to engage submarines seems insufficient, why no ASM’s?


I think most of us agree an ASROC weapon is needed for T26, but given tight budgets and uncertainty it’s perhaps understandable that efforts are being focused on detection rather than prosecution.

Detection is by far the more complex of the two, and it has an inherent deterrent effect that is effective in both peace and wartime scenarios. Take the SOSUS net across the GIUK gap, or China’s sonar wall around the South China Sea. Even in peacetime, you don’t want to be giving data on your acoustic signature to a potential future opponent.

Meanwhile, we do still have several means of prosecuting targets, by submarine, helicopter, and soon MPA again. We still have most of the next decade to procure an ASROC weapon before we could even field it anyway, and Stingray needs either an upgrade or replacement around the same time. It’s more than plausible that the two needs will be rolled into one, with the two most likely options being a purchase of US weapons or an fusion between an upgraded Stingray and the RUM-139 booster.

James Fennell

Anti-submarine rockets were in the T26 rfp and ‘nice to have’ options in the T31 rfp – so I think there is an ambition to get them.

Simon m

For me this is good news and should provide some uplift in capability.

But I think development of the wildcat is a must really especially considering the smallish numbers of Merlins.There is no real reason aux tanks cannot be added along with a sonar system and lightweight sonobuoys.

If the army wildcat could be transferred to the RN and upgraded then this would give better mass and allow merlin to concentrate further out. The army never really wanted wildcat and could benefit from something like a H145m/AW139 or AW139 mix giving the army better utility & potentially capability than wildcat.
Though I don’t know if the RN would have enough pilots for extra helos?

ASROC would be a good purchase I wonder if any could be fitted to T23 towed array maybe using adaptable deck launcher? The ISSGW weapon could then be redeployed to T23 GP T31 or T45? Once T26 in service the ADL could be transferred to T45/T31 to allow Mk41 compatible weapons.

Considering NavyX I am surprised there is no talk of looking at the Wave glider concept as this looks a good system for providing persistent ASW and could be deployed in home waters by OPVs.
New vtol and fixed wing UAVs with reasonable payload and range are required as well.

Not sure if they could be armed with mini torpedoes and or depth charges?

T31 needs a bow mounted sonar as a minimum and if possible a cheap towed array.


Add a decent sonar to Type 31e with ASROC in Mk41 vls. Make the most of the limited assets you have! Alternatively, scrap Type 31e build at least two more Type 26 and spend money on maintaining six Tupe 23 with towed array in service for many more years.

Richard j

Gets my vote. Plus add anti sub torpedoes to all RN vessels. Type 45s not too different to old Bacchante class – if helo is US.


All positive but a lot of these initiatives are the sort of upgrade paths that are essential just to keep these systems relevant and modern as apposed to representing ‘ahead of the curve’ refinements.

Replacing the RAF’s Sentinel’s with overland equipped Poseidon’s for a larger 14-16 dual mode fleet seems like a no brainer.

Dipping sonar’s for the RN Wildcat’s, ASROC for Type 26 and at least a bow mounted sonar for Type 31 are all things that would also collectively offer a substantial jump in capability for a smallish price-tag.


Sentinel, Poseidon, future AWACS, the Air Tanker fleet, Rivet Joint should all have been based on 1 civilian ETOPS airframe type (or possibly 2 types, for redundancy) from the get go.

Hopefully we can right this historical wrong going forwards. Certainly opting for Wedgetail is a step in the right direction, although in my mind the A330 platform seemed better suited than a 737, in terms of range and space for future upgrades and mission stations. Who knows, maybe in the 2050s we might all be fitting frickin’ lasers to our AWACS! But on balance Wedgetail was a known quantity, and therefore fairly low risk, which is the sort of procurement contract we need for the next few years.

Having said that, I’m in no rush to replace Sentinel, and I hope it gets a life extension. It provides a valuable service, and I think that if it goes out of service as scheduled, there is no money to run a replacement programme, and we would likely see that capability lost if it withdrawn, rather than replaced, even if the replacement was just ripping out the gubbins from the Embraers and stivking them in a 737.

I probably would’ve opted for A330 for air tanker and AWACS, and 737 for ASW, and Elint (basically replacing Nimrod) and Sentinel/ISTAR could have been either, depenfing on need, ie A330 if we wanted a larger control aircraft like the USAF’s JSTARS, or 737 if we wanted a simpler set up as we had with Sentinel.

Now, with A330 for refuelling, and 737 for ASW and AWACS, it prob makes sense to go with 737 again for the Rivet Joint and Sentinel replacements, when the time comes. But I can’t see that happening for a while.

Not sure the Wildcat pilots will take too kindly to being reassigned to sub hunting, they’ll have to start behaving themselves and stop acting like hooligans hooning it around all over the place!

Will O

Sentinel, P8A & Wedgetail were all great choices, the UK got it just about spot on (eventually).
Refueling, hmm, not so much.

EC37B for Elint would get my vote.

Would 737 for ASW really be your first choice?

I’d actually like to see some smaller MPAs to compliment the P8As. Everything being large & high end isn’t good.

At the very small end, maybe even IOMAX Archangels, I think they’d be good for loitering & checking out radar contacts that the P8As make? May save P8s from having to make detours to take closer looks at things?
Costs per flight hour would be virtually negligible.
They even use an MX-15Di for EO/IR (which presumably better suits their lower altitude profile).
Would thus be a near perfect match with the P8A?

I also think this little aircraft would make a good convert to a small MPA;
Just as per the Archangel;
PT6A turboprops (thus straightforward maintenance)
STOL from unprepared airstrips
– but Kodiaks can also come with floats.
“Range: 1,132 nm (2,096 km) 135 ktas, 12,000 ft [3,700 m]
Endurance: 9.9 hrs (95 ktas, 12,000 ft [3,700m])”
Service ceiling: 25,000 ft [a] (7,620 m) (like the IOMAX)
Low cost; $2.5m each
One rather serious caveat; all those accidents.

Or perhaps a navalised Combat Caravan?

Are we not missing a trick by overlooking something already made closer to home;
The Britten-Norman Defender MPA? It already exists. Why are there none in the UK’s inventory?!

Sort it out UK, & order some Defender MPAs!

Will O

It would be madness to replace the Sentinel. They’re relatively new. If anything, the UK should order more of them.
The Sentinel R1s could do with an upgrade, maybe a midlife upgrade (& lose some weight, replace some of that decade old wiring with fibre optics). The RAF lost RAPTORs (DB-110) when it lost the Tornado, & RAPTORs were useful, so it would be bonkers now not to fit those (ideally newer 3rd Gen.) to those Sentinels.
As the-marquis says, ‘it provides a valuable service’. Essential, to the UK and our allies. Those Sentinels should not be leaving the RAF.

It would make sense to fit the APS-154 AAS, except (if Gabriele Molinelli is to be believed & he usually is) use of the MX-20HD EO/IR camera turret would be lost.
The other thing, is I think linking up the Poseidons with ASTOR might be a bit more ungainly.
Ordering more P8As would be great, but if so, they should also focus on ASW. Surely a direct replacement of another 7 P8As in place of the perfectly good, four or five existing Sentinel R1s, would add a great deal of cost. Cost is bad lol.


Going multi-static is a big improvement in capability, and I think the right way to go. Just imaging how a single ping, observed from 4-8 sonar can provide “change in dimension” level of information.

It is also important that, while the submarines (without good silent communication tool) can only do bi-static, the surface fleet only can go multi-static.

A small number of “pinger”, listened from many silent “listeners” gives large ambiguity for enemy SSK. Yes, enemy SSK knows the location of pinger from hundreds of miles away, but do not know where the “listener” is located. They won’t know if they were already detected or still hidden, which will make their tactical decision making very difficult.

I am all for multi-static ASW.

Meirion X

Not possible for a pinger to be located hundreds of miles away, because of the curvature of the Earth. Also, sound in ocean be drown out over a long distance.


Curvature of earth does not affect the sonar range, because it will be reflected at the sea surface, so called convergence zones. On the other hand, yes the sound power will decrease with distance.

For example, CAPTAS-4 is said to have a range out to 150 km = 2nd ocean convergence zones. And it is against Submarine. So, the pinging VDS sound of CAPTAS-4, famous for being very powerful, can be detected by another TASS from much farther away, I understand.

May be you are right that not as far as hundreds of miles away, but surely more than 100nm away, I guess. (I was looking for the SURTASS range for detecting Soviet SSN, but could not find a number…)


On the other hand, what “addition” shall be considered to RN for ASW is not clear for me.

Adding ASROC to T26 looks very important. In active ASW world, enemy SSK can be detected “in surprise” and ASROC with short reaction time may make a big difference.

Adding something ASW to T31, I have no good idea. It is NOT just adding a hull sonar, but ASW crew team, analysis electronics and software. Cost of the hull sonar itself is only a fraction of the total cost. And still, it is just a hull-sonar in normal hull, surely not a powerful ASW tool.

Rather, adding a few P-8 will be more cost-efficient way to go? We all know current 9 airframe is far from efficient.

Also, how about USV-based ASW, like ARCIMS ASW system? I guess, adding “ARCIMS ASW system” with its system and crew team, might be better than adding hull-sonar to T31. USV-ASW system will be “a lttile more” expensive than a simple hull sonar, but its total cost including the whole ASW crew team might not be largely different. Also, if no ASW threat is there, the ARCIMS USV can be used in many other tasks, while the hull sonar onboard T31 is just a dead-weight.

CDR Chip

Does anybody know anything about the Russian wake detection sensors?

They look like a bunch of spikes mounted on a board, but I don’t know much about them other than that. I’ve heard that the RN knows more about them than we Americans do.


Excellent article, but in listing the UK’s ASW order of battle, the author has left off a key weapon that has helped keep the UK’s territorial waters safe for the past 9 years:

The C130 Hercules fitted with the Mk1 Eyeball and a optical sensor enhancement system optimised for daylight operations (a pair of Minolta binoculars some airman long since retired had bought on a rotation through Hong Kong in the 1980s)

Simon m

I would like to see flash added to wildcat. There has also been fibre optic sonar developed so perhaps this would take up less space.? Add to this mini sonobuoys. Not sure as to why a major avionics upgrade needed as it can already handle surface attack in a complex environment & sonar was already design and in use by ROK. Some work needs to be done with aux tanks for wildcat as it really could do with a range increase for all ops

I think we also need to look at the RAF getting extra protector UAVs configured for ASW or getting tritons.

Added to this shipborne UAV and USV need to begin to be purchased and support on ship sensors. Use of maybe depth charges combined with these may give a further offensive capability?

I heard a rumour there were 3 extra sets of towed array sonar if so get these deployed on T31.

Trainable decoy launchers could also be used to get sonobuoys in the water as well as improving protection of the fleet.

Why not look a CAMM/stingray/depth charge solution to provide standoff submarine capability? This could be integrated with EXLS, the mushroom farms, may not give quite the range of ASROC but could be a useful addition?

We don’t deploy torpedoes from ships anymore but how about looking at UUVs such as bluefin 12 could these use the launchers or space where launchers are.

Another possible tool could be the adoption of the Waveglider system especially where blocking/area monitoring/denial is useful


I’m not sure if we’re looking at ASW in the right manner. Sonar searches for noise, metal, and the RN is good at it, but what if we look for quiet, or use a green light laser to create trip nets, or utilise underwater current to recharge the batteries of sonar devices that have been dropped?