BBG(X) - DISCUSSION ONLY

[Desertfox]

And what exactly your sub would do, after it fires its missiles - and got all patrol planes, drones, sattelites, warships and hunter-killers zeroed on its location? Because launch of CPS anywhere near China coastline would allow Chinese to immediately pinpoint the submarine position. CPS is NOT a Tomahawk; the CPS launch would be detected immediately, and starting point would be calculated in mere seconds. After which - sattelites would start to scan for water disturbances, patrol planes would rush into area to begin search, and hunter-killer groups would be deployed.

How exactly your submarine is supposed to survive that? Unless she is firing from reliable "bastion", provided by surface forces and aviation, the submarine have little chances to survive retaliation. And in conventional warfare, risk would be impractically high.

All this applies far more to a surface warship...

 

[Dilandu]

All this applies far more to a surface warship...

Far less, because while submarine could ONLY hide, sufrace warship could actively defend itself.

 

[Not James Stockdale]

I truly cannot understand why the Navy intends to field the CPS within its surface fleet. It is clearly an intermediate-range ballistic missile. Its range enables launch platforms to strike targets while remaining well outside enemy detection and surveillance coverage, making it entirely unnecessary to mount such a weapon on frontline combat vessels optimized for high-level stealth design.

The Chinese have a huge number of reconnaissance satellites and anti-ship ballistic missiles that can hit out to 5,000 km, so any surface ship moving in to launch CPS has to be able to survive in that environment.

Which is also retarded. Worrying about what kind of shore bombardment gun you put into an ABM platform is like worrying about what kind of tail gun you put into a B-21.

A 5-inch gun with HVGP is kinematically similar to an ESSM.

 

[Firefinder]

That sort of stuff will ruin any manoeuvring ability, but it probably wont stop the mass of the missile continuing its trajectory. Especially if theres a lump of tungsten penetrator in it. Theoretically a kinetic hit could damage the aerodynamics enough to throw it off course.

Of course it then becomes a game of WHEN.

Cause remember Mach 5 is a Mile a Second or 1.6km sec.

5 seconds is how long a ship needs to drastically change course.

Which means that at any distance at or over 5 miles, or rather 5 Seconds of UNGUIDED travel time...

A ship, even one like the Tubby or CVN, with warning CAN DODGE.

Cause it's not the speed of the projectile you need to worry bout, but the time you have to react.

Every second over that 5 makes it that much more likely for an aware warship to dodge you Unguided Hypersonic Tungsten dart.

That before getting into the weeds of if the Missile was even on a course that it could ballistically hit the ship or the fact that unpower gliders are. not going mach 5 below 30k feet, more like Mach 2-3 at best assuming it didn't need to waste energy to dodge. That last bit is highly unlikely so you have even more time to dodge.

Which leads to whole other fun discussions others will likely touch on better.

But to tldr it.

Ships, even big are far more agile then many expect and can force misses easily.

 

[CastleBravo]

The Chinese have a huge number of reconnaissance satellites and anti-ship ballistic missiles that can hit out to 5,000 km, so any surface ship moving in to launch CPS has to be able to survive in that environment.

I still don't think BBG(X) is meant for China. It is to hold targets at threat you might otherwise need a carrier group for. BBG(X) frees up all the carrier groups so they can go fight China.

 

[Foo Fighter]

Just pondering on why you would have a BGS like that with a small escort or none at all in harms way.

Would they not be better as part of a fully fledged task force and cover all bases?

 

[cccgong]

Many proposals for 27" SM3/SM6, CPS/LRHW is ~34" diameter.

You could quad-pack SM2s into a 36" tube, for example.

It would also allow for multipacking of PAC3. There's a huge number of reasons to go for new larger tubes, in addition to the tapped out growht margin on SM3/6.

I still don't think BBG(X) is meant for China. It is to hold targets at threat you might otherwise need a carrier group for. BBG(X) frees up all the carrier groups so they can go fight China.

Carriers whose aircraft + cruise missiles have less range than missiles out of CPS? While being more expensive (needs other ships for defense).

The Chinese have a huge number of reconnaissance satellites and anti-ship ballistic missiles that can hit out to 5,000 km, so any surface ship moving in to launch CPS has to be able to survive in that environment.

A 5-inch gun with HVGP is kinematically similar to an ESSM.

Not the anemic version that has been advertised. A clean slate redesign or one using the gun on the Zumwalts yes and that would still require a booster on the projectile not a simple non-powered projectile. But not the current sabot setup for the 5 inch guns.

 

[Not James Stockdale]

Of course it then becomes a game of WHEN.

Cause remember Mach 5 is a Mile a Second or 1.6km sec.

5 seconds is how long a ship needs to drastically change course.

Which means that at any distance at or over 5 miles, or rather 5 Seconds of UNGUIDED travel time...

A ship, even one like the Tubby, with warning CAN DODGE.

Cause it's not the speed of the projectile you need to worry bout, but the time you have to react.

Every second over that 5 makes it that much more likely for an aware warship to dodge you Unguided Hypersonic Tungsten dart.

That before getting into the weeds of if the Missile was even on a course that it could ballistically hit the ship or the fact that unpower gliders are. not going mach 5 below 30k feet, more like Mach 2-3 at best assuming it didn't need to waste energy to dodge. That last bit is highly unlikely so you have even more time to dodge.

Which leads to whole other fun discussions others will likely touch on better

First, ASBMs use onboard guidance to actively track the target ship - that's what makes them ASBMs. They would be able to track a ship through any kind of turn. Second, it takes a lot longer to turn a ship than 5 seconds. I wouldn't count on anything less than 30 seconds at the absolute best to turn and begin moving away, and that's from the moment the wheel on the bridge begins turning. You'll need a lot more time to actually make the decision and relay the order.

I still don't think BBG(X) is meant for China. It is to hold targets at threat you might otherwise need a carrier group for. BBG(X) frees up all the carrier groups so they can go fight China.

The carriers don't have the range to get into the early stages of the China fight when DF-21s are flying all over the place. A ship with CPS, on the other hand, can hit targets in the Taiwan Strait while avoiding most of the close and medium-range threats. I would be looking at IRBM-derived ASBMs like the DF-26, air-launch cruise missiles from Chinese bombers, and anything launched by Chinese ships or submarines.

I like the idea of horizontal cold launchers. Torpedo launchers have been able to fling 21" diameter and 3,500 pound tree stumps off ships for decades. Now give it a set of folding wings to flip out at launch and a way to move it 20-30 miles away before it points skyward and gives a farewell to the missile. Not great for PAC-3 but great for something like ballistic missile, to conceal the exact location of the launch platform. Or it probably is easier to simply launch from a submarine tube like they are working on doing with NSM.

That makes sense, but I think a quasi-expendable USV with a pair of Mk 70 containers can do the same thing with better time to impact, more range from the command platform, and without having to worry about submerging a missile in saltwater.

If you want even more distance, you could use a floating container to hold the missile for a few hours while the launch platform moves away. Something like that might work with both ships (if you give the ships 21" torpedo tubes) and submarines. The container could launch the missile after a set time or wait to receive a launch order by radio.

The Mk 48 torpedo expends about 1,000 lbs of fuel to move a 650 lbs warhead and 2,000 lbs body that range, so you won't be able to fit a full-size Tomahawk in that kind of envelope. I would expect something closer in size to the NSM or Harpoon as a payload.

 

[CastleBravo]

The carriers don't have the range to get into the early stages of the China fight when DF-21s are flying all over the place. A ship with CPS, on the other hand, can hit targets in the Taiwan Strait while avoiding most of the close and medium-range threats. I would be looking at IRBM-derived ASBMs like the DF-26, air-launch cruise missiles from Chinese bombers, and anything launched by Chinese ships or submarines.

The carriers can do a lot of useful stuff without getting into DF-21 range like help keep those bombers from getting too far past Taiwan.

With a 2000nmi missile, the Army can cover the strait and a ways inland from Guam/Tinian, no need for an over 9000 megabuck battleship. If you need to hit further inland, you can do it with any ship you can park the Dark Eagle trailer on.

 

[greedo]

Then you lose control of the Sea Lines of Communications.

The minimum feasible capabilities for a ship continue to rise and rise. There is very little choice in the matter. Either you are able to defend against the attack or you have no ability to continue to move things by sea. And either you lose a war that is across the ocean from you or your country starves to death. Your choice.

If we're expecting BBG(X) to keep the SLOCs open, then we'll need to build far more than planned. Cruisers/CVSG etc aren't intended for keeping SLOCs functioning.

 

[greedo]

Then you lose control of the Sea Lines of Communications.

The minimum feasible capabilities for a ship continue to rise and rise. There is very little choice in the matter. Either you are able to defend against the attack or you have no ability to continue to move things by sea. And either you lose a war that is across the ocean from you or your country starves to death. Your choice.

Let's not get too hyperbolic. There are limits to what can be funded. And it remains to be seen how a couple dozen extremely expensive ships will be used, countered, and maintained over the years. I remember when the MX was deployed, and now we're reinventing the wheel because of that arms control treaty.

If we were a serious nation, with sound leadership, we'd be building a helluva lot more submarines than this vanity ship.

And the US is not at risk of starving if it can't defeat China in their own backyard.

 

[greedo]

Because a ballistic missile coming out of an empty patch of ocean is the start of global thermonuclear war.

If a ballistic missile of any type is used against a nuclear armed opponent, it will inevitably lead to a GTW.

 

[greedo]

Assuming that they aren't nearby... which submarine can't check.

ASW aircraft, especially helps most definitely can be detected by submarines...

 

[Josh_TN]

A 5-inch gun with HVGP is kinematically similar to an ESSM.

Has such been deployed yet? Is there a program to do so?

 

[Josh_TN]

I still don't think BBG(X) is meant for China. It is to hold targets at threat you might otherwise need a carrier group for. BBG(X) frees up all the carrier groups so they can go fight China.

Then they are pointless.

 

[Josh_TN]

Far less, because while submarine could ONLY hide, sufrace warship could actively defend itself.

The surface warship has zero options to hide; the submarine can be 30nm away in an hour. No question which I would rather be on. Unless you were right under an opponent MPA - and that would be an impressive feet of air superiority east of Taiwan - the submarine has a very good chance of slipping away.

 

[CastleBravo]

Not the anemic version that has been advertised. A clean slate redesign or one using the gun on the Zumwalts yes and that would still require a booster on the projectile not a simple non-powered projectile. But not the current sabot setup for the 5 inch guns.

Bring back the 8" Mk71 MCLWG as a smoothbore cannon at >100kpsi and you have something that rivals the 32 MJ EM gun. EM gun would still have higher velocity, but 8" could do ~1800m/s and beat the EM gun on muzzle energy with a heavier projectile for better ballistic coefficient, base bleed, more KE pellets, ect. Then experiment with ETC on the 8" gun and try for >2km/s.

 

[Dilandu]

the submarine can be 30nm away in an hour.

At 30 knots speed, the submarine would be detected from the other side of Pacific.

 

[Josh_TN]

The carriers can do a lot of useful stuff without getting into DF-21 range like help keep those bombers from getting too far past Taiwan.

With a 2000nmi missile, the Army can cover the strait and a ways inland from Guam/Tinian, no need for an over 9000 megabuck battleship. If you need to hit further inland, you can do it with any ship you can park the Dark Eagle trailer on.

CSGs realistically can attack surface targets out to about a thousand miles with LRASM and MALD-N with modest refueling, and the escorts can do the same with tomahawk. A CSG could stay a thousand miles off the Chinese coast outside effective DF-21 range while still being a huge threat to any landing zone or PLAN force east of Taiwan. DF-26 is obviously still in range.

The effectiveness of PRC ISR would also have a huge effect on the threat level. PLARF would be largely dependent on orbital assets for targeting at these ranges, at least until they had air superiority over the first island chain.

 

[Josh_TN]

At 30 knots speed, the submarine would be detected from the other side of Pacific.

An exaggeration. If cavitation on the propulsor could be prevented with a combination of depth and slower speed, there is not a lot of signal outside broadband flow noise. A Virginia’s pump jet is built specifically to prevent cavitation at higher speeds, at the cost of efficiency and top speed for a given amount of power.

Call it 20nm then. It is a much better option than being in plain sight, and it can be magnified with acoustic decoys/submarine simulators.

 

[Josh_TN]

If a ballistic missile of any type is used against a nuclear armed opponent, it will inevitably lead to a GTW.

Someone failed to inform Israel of that.

 

[Josh_TN]

ASW aircraft, especially helps most definitely can be detected by submarines...

Very conditionally. Passive listening for low altitude passes, or else passive ESM *if* the aircraft is radiating at the water. US P-8s now do ASW at high altitude and use glide kits on their torpedoes; you would never hear them acoustically. No idea if PRC MPAs do the same.

 

[Scott Kenny]

And what exactly your sub would do, after it fires its missiles - and got all patrol planes, drones, sattelites, warships and hunter-killers zeroed on its location? Because launch of CPS anywhere near China coastline would allow Chinese to immediately pinpoint the submarine position. CPS is NOT a Tomahawk; the CPS launch would be detected immediately, and starting point would be calculated in mere seconds. After which - sattelites would start to scan for water disturbances, patrol planes would rush into area to begin search, and hunter-killer groups would be deployed.

How exactly your submarine is supposed to survive that? Unless she is firing from reliable "bastion", provided by surface forces and aviation, the submarine have little chances to survive retaliation. And in conventional warfare, risk would be impractically high.

Same thing a Trident sub does after launch: go deep and run like hell.

So CPS is the missile, not the launcher. I thought (based on publicity renders) they would use the 12 cell GVLS from LM. Not 12×3, just 12 missiles, but if not used for CPS they supposedly quadpack the standard Mk-41 cells.

Technically, CPS was the program that led to LRHW, but most people still call it CPS.

At least on the Zumwalts, they're using Trident-sized tubes (rather, VPM-sized as they're not long enough to hold Trident) to hold CPS/LRHW tubes. 4x 87" tubes, each holding 3x CPS/LRHW for a total of 12. If used for Tomahawks (the only 21" missiles designed for cold launch) the Advanced Payload Modules can hold 7x 21" weapons.

For the BBG install, it's not clear whether the plan is still the APMs from the Zumwalts but 12 of them since there's room or if they plan to use the GVLS proposal. APMs would be cheaper and tested, GVLS would be more compact.

Assuming that they aren't nearby... which submarine can't check.

Sure they can. Pop to periscope depth, the ESM antennas are built into the periscopes. Tomahawks are launched from PD, though it's not clear how deep you should be for launching CPS/LRHW.

Just pondering on why you would have a BGS like that with a small escort or none at all in harms way.

Would they not be better as part of a fully fledged task force and cover all bases?

Depends.

Back in the 600-ship Navy days (1990-91), each carrier had 2 cruisers in the group, 2 DDGs, and 2 Sprucans. Plus there were 4x surface action groups with an Iowa, one CG, and a trio of DD/DDGs.

It would also allow for multipacking of PAC3. There's a huge number of reasons to go for new larger tubes, in addition to the tapped out growht margin on SM3/6.

I keep forgetting about PAC3s. (where's the embarrassed emoji?)

First, ASBMs use onboard guidance to actively track the target ship - that's what makes them ASBMs. They would be able to track a ship through any kind of turn. Second, it takes a lot longer to turn a ship than 5 seconds. I wouldn't count on anything less than 30 seconds at the absolute best to turn and begin moving away, and that's from the moment the wheel on the bridge begins turning. You'll need a lot more time to actually make the decision and relay the order.

While any ship is going to go into instant evasive maneuvers as soon as someone calls "Vampire, Vampire, Vampire, incoming missiles!" a big ship has rudder movement time and just flat takes a long time to start turning. At best we're probably talking 1 minute between slalom turns.

The carriers don't have the range to get into the early stages of the China fight when DF-21s are flying all over the place. A ship with CPS, on the other hand, can hit targets in the Taiwan Strait while avoiding most of the close and medium-range threats. I would be looking at IRBM-derived ASBMs like the DF-26, air-launch cruise missiles from Chinese bombers, and anything launched by Chinese ships or submarines.

At least my mental model was using CPS/LRHW to engage the AShBM launchers/batteries, so that the carriers can get close enough to engage them with aircraft strikes.

At 30 knots speed, the submarine would be detected from the other side of Pacific.

Nah. Seawolves are rumored to be as loud at full speed as a 688i idling at the pier. And IIRC the Virginias have the same propulsor design.

 

[Desertfox]

Far less, because while submarine could ONLY hide, sufrace warship could actively defend itself.

Guess what, China has far far more weapons capable of targeting surface warships that they have weapons targeting submarines. The entire PLARF can't touch subs, and most other ASW weapons have to be right on top of the sub to engage.

 

[Josh_TN]

Nah. Seawolves are rumored to be as loud at full speed as a 688i idling at the pier. And IIRC the Virginias have the same propulsor design.

The rumor I heard a couple decades ago was “as quiet at 20knots as a 668 tied to a pier”, but I assume there is some myth or hyperbole to that assuming there’s any truth at all. Certainly cavitation, the greatest source of high speed noise, can be controlled with propulsor design and increased depth. Pump noise was generally the next loudest noise from what I understand as a non squid, and in Ohio that was handled by free circulation at lower power. I assume Virginia uses that or something equally clever. That leaves low freq propulsor noise, which is generally attenuated more in shrouded propulsor designs like VA, and the broadband increase in flow noise, which is usually a lot harder to identify because it is not frequency specific. Plant noise should be more or less equivalent at any speed, same with transients.

Certainly being underwater where only sonar can find you is preferable to being on the surface where basically any sensor can track you, potentially even from orbit, especially when you have marked your position and explicitly given away your platform type.

 

[johnpjones1775]

Assuming that they aren't nearby... which submarine can't check.

Yes assuming they aren’t nearby by, but considering the 2000ish mile range on CPS, that would be extremely unlikely. If they were that would just be the worst of luck.

 

[CastleBravo]

Yes assuming they aren’t nearby by, but considering the 2000ish mile range on CPS, that would be extremely unlikely. If they were that would just be the worst of luck.

The sub would download the latest intel from the satellites and know where all the enemy surface combatants are prior to launching a missile. If one is nearby it gets a missile too.

 

[Josh_TN]

The sub would download the latest intel from the satellites and know where all the enemy surface combatants are prior to launching a missile. If one is nearby it gets a missile too.

The sub can just hear the surface ships, if they are remotely close enough to be a threat. Possibly helicopters too, especially if they are using an active dipping sonar. Fixed wing MPAs would be by far the biggest threat because they the fastest transit time to the target area and the lowest chance of being detected by the launching sub.

 

[EmoBirb]

Guess what, China has far far more weapons capable of targeting surface warships that they have weapons targeting submarines. The entire PLARF can't touch subs, and most other ASW weapons have to be right on top of the sub to engage.

Submarines are constricted in the Taiwan Strait and SCS though. The first Island Chain would be basically entirely off limits in a hot war, the second Island chain would be contested and losses of highly trained crews and very expensive nuclear submarines would be guaranteed. Surface ships at least have higher chances of the crew surviving any given encounter.

 

[Josh_TN]

Submarines are constricted in the Taiwan Strait and SCS though. The first Island Chain would be basically entirely off limits in a hot war, the second Island chain would be contested and losses of highly trained crews and very expensive nuclear submarines would be guaranteed. Surface ships at least have higher chances of the crew surviving any given encounter.

Agree the first; disagree with the second. Inside the first chain, boats are limited by geography and extremely shallow water, outside a relatively small area inside the SCS. Outside that there are no choke points and depth falls off a cliff, and I think the PLAN would struggle to hunt there without at least sufficient air superiority such that its MPAs could transit over Japanese or Philippine outer islands safely (or alternatively Taiwan itself).

 

[Desertfox]

Why would you be shooting CPS from inside the Strait!? If you need to hit Western China its probably easier from the Arabian sea or via bomber.

 

[EmoBirb]

Agree the first; disagree with the second. Inside the first chain, boats are limited by geography and extremely shallow water, outside a relatively small area inside the SCS. Outside that there are no choke points and depth falls off a cliff, and I think the PLAN would struggle to hunt there without at least sufficient air superiority such that its MPAs could transit over Japanese or Philippine outer islands safely (or alternatively Taiwan itself).

My rationale is that the PLAN and PLAAF can deploy shorter range MPAs and SSKs within the first Island Chain, which would free up the higher capability assets like XLUUVs, USVs, SSNs and more capable MPAs and UAVs to prowl the second Island Chain. Where you had USN and PLAN SSNs play cat and mouse with each other. Which is why I said that it would certainly be contested and see losses (to both sides, but I didn't assume I had to clarify that).

Admittedly, I wouldn't necessarily say that the PLAAF establishing air superiority over the SCS would even be a question of 'if' and more so how quickly they can mobilize their assets and what sortie rates they could consistently sustain. But we're now leaving the BBG(X) relevant portion of the discussion and entering more into general US-China War in the SCS territory.

Either way, I think a capable surface combatant armed with CPS for long range strike capabilities against land and sea targets isn't a bad idea per say. In fact I'd argue having dedicated CPS 'strike cruisers' would be rather wasteful. So having both VLS and CPS doesn't conflict at all in my eyes, especially as VLS should mostly be seen as a mainly defensive system meant to defend the own vessel and ships of a wider combat group in general proximity. Also having CPS for offensive strike means that the number of Tomahawks in the VLS cells can either be greatly reduced our outright eliminated, depending on what the mission is. After all not every scenario is taking on the PLAN. If the plan is to just flatten 'Random Country Nr. 5's infrastructure, then both CPS and more Tomahawks can be carried for land strikes, living up to the BB designation (missiles are just the big naval guns of the 21st century after all). That's now less so directed at you @Josh_TN and more so addressing the general discussion of the last pages.

 

[johnpjones1775]

The sub would download the latest intel from the satellites and know where all the enemy surface combatants are prior to launching a missile. If one is nearby it gets a missile too.

We’re not talking about surface combatants…

 

[Josh_TN]

Touche. I was originally thinking in terms of the US using CPS against China or Russia. It would be difficult keeping a conventional conflict with either of those and the US non-nuclear.

In any US-PRC conflict, China would be sending ballistic missiles everywhere almost immediately. I doubt the US would respond with nukes until one actually detonated. And clearly China better get used to the idea that there would be US strikes on its territory if it starts bombing US bases, even if its strikes were limited to the pacific.

I think nuclear weapons would generally be avoided in an environment of nuclear parity where the conflict is not existential, but there of course is always a risk of nuclear conflict when the countries involved have them.

 

[Grey Havoc]

Guess what, China has far far more weapons capable of targeting surface warships that they have weapons targeting submarines. The entire PLARF can't touch subs, and most other ASW weapons have to be right on top of the sub to engage.

That might perhaps be an unwise assumption. For example, there is nothing stopping the PLARF from putting a nuclear armed torpedo on a DF-21 (shades of a certain proposal for the RN back in the 1980s involving a planned 'British' Pershing).

US P-8s now do ASW at high altitude and use glide kits on their torpedoes; you would never hear them acoustically. No idea if PRC MPAs do the same.

That particular CONOPS has been running into more than a bit of trouble in practice, not least because a lot of the deployable UAV systems that were supposed to make it at least some bit practical, e.g. MAD drones, have remained vapourware or have else been cancelled outright.

 

[Josh_TN]

That particular CONOPS has been running into more than a bit of trouble in practice, not least because a lot of the deployable UAV systems that were supposed to make it at least some bit practical, e.g. MAD drones, have remained vapourware or have else been cancelled outright.

Do you have a link? I do not see how flying low would help P-8 since only the Indian version has a MAD boom.

 

[Scott Kenny]

Do you have a link? I do not see how flying low would help P-8 since only the Indian version has a MAD boom.

There's still a practical limit to how far you can drop a sonobuoy and have it land where you want it.

Or have them survive impact with the water.

Flying at 200ft and the buoys land where you want them and survive landing.

 

[TomS]

There's still a practical limit to how far you can drop a sonobuoy and have it land where you want it.

Modern buoys use GPS, so you know exactly where they are rather than just having to rely on precision delivery and a guess about their drift.

The math for doing TMA gets a bit harder, but compute is cheap.

 

[Josh_TN]

I had thought modern deployment included spinning the buoy up and delaying the chute open event to increase precision. I also thought there some efforts to measure the drift of buoy drop and compensate for windage on subsequent drops, whether that involved gps on the buoy or just triangulation of its signal.

But in any case, I suspect a turbofan P-8 is a much quieter and faster platform than a P-3.

 

[Scott Kenny]

I had thought modern deployment included spinning the buoy up and delaying the chute open event to increase precision. I also thought there some efforts to measure the drift of buoy drop and compensate for windage on subsequent drops, whether that involved gps on the buoy or just triangulation of its signal.

I'd hope so.

But the whole point of the P-8 was to stay up high and economically cruise while other UAVs/CCAs flew low and dropped most of the sonobuoys.

But in any case, I suspect a turbofan P-8 is a much quieter and faster platform than a P-3.

P-3s have a very distinctive 68hz tonal line on sonar. Same with old C-130s up through -H models (same engines, same spacing on the wings, same number of prop blades).

I spent about 8 hours under what felt like every P-3 in the Pacific Fleet one deployment, stuck in a box in the water while the P-3s roared overhead and dropped sonobuoys. You could hear the P-3s roar with your bare ears, and then feel the 19khz dentist-drill of the sonobuoys in your teeth and bones.