Questions about Submarine abilities

[kato]

sounds an awfully lot like it would require the use of active sonar

Where do you read active sonar into that? The downwash itself creates a ripple in the water, which spreads through the medium and can be picked up by passive sensors provided they are sensitive enough. There's nothing about it that an active ping would enhance.

 

[Firn]

A system like IDAS will always be a hard sell because of the inherent limitations.

• To use it forces the sub to stay close to the surface, increasing its vulnerability to detection.
• “The submarine can acquire ASW helicopter when submerged, by localizing the ripple effect created by the rotor downwash” sounds an awfully lot like it would require the use of active sonar, a dead giveaway if the helicopter has dropped any passive sonar buoys. Probably won’t work well in anything over sea state 1.
• Rocket propulsion underwater is noisy. Unless the helicopter is almost on top of you he probably has enough time to get a general location and drop his torpedo(s) before you can kill him.

IDAS or similar systems are of course not a silver bullet and their use depends on a myriad mix of circumstances and considerations on the mission, threat etc by the driver. It is important to consider why, where, when and by whom it was initiated.

Such a missile has the following potential uses:

a) Self-defense or ultima ratio against ASW helicopters, likely operating in twos or threes as part of a ASW team. The driver will of course try hard to avoid a situation in which he might be force to use it. If he has to use it as a last resort, I suspect he will have to make heavy use of it, relasing depending on the numbers of helos 4 or more to kill the near threat. Hopefully this will cripple the ASW hunter force and it will depend on the other ASW assets to hunt down the sub with all the risks.

b) Destruction of light surface ships or elements of it. Might be used when the target is not worth a heavy torpedo and when there is no big ASW threat.

c) Attack of ground targets near the shoreline, perhaps in support of inserted forces, depends of course also on METT-TC

d) Shooting down a military/civilian aircraft starting from an airport close to the sea, maybe from something like CAPTOR. Of course this is not something you expect a western SSK to do.

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About your points:

- I see little reason why the SSK should have to stay particulary close to the surface to release IDAS

- The downwash by the rotor is of course detectived detected passively by the submarine, just as the sound signature of MPA or the sound of the ASW engine. Of course the range from which it can be detected depends on a lot of variables.

- Of course the propulsion system is noisy compared to a slow moving heavy torpedo. Traveling underwater it will telegraph the presence of the submarine to passive sonar, flying through the air will give at least give an area reference when detected and tracked by radar etc.

BTW: IDAS is based on the IRIS-T a missile achieving Mach 3 with an operational range of roughly 25 km. As it is not launched by aircraft and had to be heavily adapted it won't be so high performing, but an ASW heli should be compared to a modern fighter a rather easy target.

 

[My2Cents]

Where do you read active sonar into that? The downwash itself creates a ripple in the water, which spreads through the medium and can be picked up by passive sensors provided they are sensitive enough. There's nothing about it that an active ping would enhance.

Ripples would be on the surface, how would passive sensors detect them, they don't make any sound like white caps. Or by ripples do they inidcate elsewhere that they mean the noise generated on the surface of the water, not motion of the water.

 

[My2Cents]

BTW: IDAS is based on the IRIS-T a missile achieving Mach 3 with an operational range of roughly 25 km. As it is not launched by aircraft and had to be heavily adapted it won't be so high performing, but an ASW heli should be compared to a modern fighter a rather easy target.

From the article (emphasis added):

This unique submarine launched anti-helicopter weapon is designed to protect attack submarines from anti-submarine helicopters, as they become vulnerable hovering low above water, dipping their sonar in search of enemy submarines. This subsonic missile is optimized to seek out such slow targets, which pose significant risk to a submarine operating at littoral, ‘brown’ waters.

One of the development challenges was the propulsion system. The same rocket was required to provide thrust for both underwater and airborne flight. The rocket was designed to sustain the missile’s at optimal velocity in submerged flight, and accelerate to subsonic flight while airborne, reaching effective range of 20 km.

Probably only the sensor systems come from the IRIS-T.

From the article I would infer that the rocket performance is limited by the need for the same engine to operate underwater, higher thrust would probably result in the internal pressure rising to high and the engine explodes. The velocity is also limited by the fiber optic link.

- I see little reason why the SSK should have to stay particulary close to the surface to release IDAS

That depends on your definition of ‘particularly close to the surface’, I would call it anything less than 100’ (30m) to the top of the sail. Still, I missed the reference to ‘brown water’, so ir would be possible to assume that the sub would already be operating in water depths less than 150’ deep.

Actually, it does not seem that unlikely a weapon given the current emphasis on naval special operations and de-emphasis of the anti-ship role.

 

[kato]

Or by ripples do they inidcate elsewhere that they mean the noise generated on the surface of the water, not motion of the water.

Sound is motion. Or, from the physical aspect, a pressure oscillation that traverses a medium from source to listener. A ripple in the water is just the same, an oscillation of the water with a specific frequency, amplitude, wavelength.

Considering individual divers can be detected through the ripples they create in water with their motion from at least half a mile away with a halfway decent hydrophone array, the considerably stronger ripples created by the downwash from a helicopter should be detectable at several miles distance minimum.

 

[Firn]

From the article (emphasis added):


Probably only the sensor systems come from the IRIS-T.

From the article I would infer that the rocket performance is limited by the need for the same engine to operate underwater, higher thrust would probably result in the internal pressure rising to high and the engine explodes. The velocity is also limited by the fiber optic link.

The missile body seems to have quite similar dimensions as well. The important bit is of course that it's warhead has an increased payload of 20kg compared to 12 kg of it's parent. The reduced speed is most likey due to, as you said underwater performance, but range would also have been an important consideration. Despite the 'sationary' underwater launch it seems to have a range of roughly 20km, making the No-Escape zone against rotary ASW assets even with subsonic speed quite large. Due to the nature of the target the IRIST-T seeker might be indeed somewhat of an sensor overkill.

That depends on your definition of ‘particularly close to the surface’, I would call it anything less than 100’ (30m) to the top of the sail. Still, I missed the reference to ‘brown water’, so ir would be possible to assume that the sub would already be operating in water depths less than 150’ deep.

Actually, it does not seem that unlikely a weapon given the current emphasis on naval special operations and de-emphasis of the anti-ship role.

There is nothing to suggest that this missile can not be fired at considerable depth, if the missile is constructed in a way to withstand the ever increasing water pressure. With all that downwash and noise from relative near ASW choppers it should be a relative small problem to get a good enough passive sonar bearing on the listening ones, should they be in a range and position to threaten the sub.

 

[My2Cents]

The missile body seems to have quite similar dimensions as well. The important bit is of course that it's warhead has an increased payload of 20kg compared to 12 kg of it's parent. The reduced speed is most likey due to, as you said underwater performance, but range would also have been an important consideration. Despite the 'sationary' underwater launch it seems to have a range of roughly 20km, making the No-Escape zone against rotary ASW assets even with subsonic speed quite large. Due to the nature of the target the IRIST-T seeker might be indeed somewhat of an sensor overkill.

The missile gets cuing for the general range and direction, but still needs to search for and identify the target on its own, there are hints in the article that was also a factor for the reduced speed. A high performance seeker may not be overkill at all, but instead an absolute necessity for making the design work.

 

[Firn]

The missile gets cuing for the general range and direction, but still needs to search for and identify the target on its own, there are hints in the article that was also a factor for the reduced speed. A high performance seeker may not be overkill at all, but instead an absolute necessity for making the design work.

IDAS has the [nomedia="http://www.youtube.com/watch?v=IZVqUeA1FhQ&feature=related"]Spike missiles - YouTube[/nomedia] and would have with the seeker of [nomedia="http://www.youtube.com/watch?v=VrC9qEFtjPE&feature=related"]IRIS-T air to air missile of F16 FIGHTING FALCON - YouTube[/nomedia] one of the most high-performing sensors in production. In the end it is designed to shoot down modern fighter jets.

A far more cheaper and less complex seeker like the ones found on ATGM like the Spike should handle relative slow targets like choppers, not speaking of ships and land targets. Cuing could be achieved by passive and active sonar or radar, depending on METT-T, while the lock-on will be achieved by CCD/IIR.

 

[My2Cents]

IDAS has the Spike missiles - YouTube and would have with the seeker of IRIS-T air to air missile of F16 FIGHTING FALCON - YouTube one of the most high-performing sensors in production. In the end it is designed to shoot down modern fighter jets.

A far more cheaper and less complex seeker like the ones found on ATGM like the Spike should handle relative slow targets like choppers, not speaking of ships and land targets. Cuing could be achieved by passive and active sonar or radar, depending on METT-T, while the lock-on will be achieved by CCD/IIR.

• The Spike has a much shorter range (8km vs. 20km). To lock-on to a target at the longer range the IDAS would need a seeker 6.5x more sensitive than the Spike’s to achieve equal performance. It is simple physics.
• IDAS has to be able search for its target, Spike does not. This allows Spike to have a narrower field of view of view and even less sensitive seeker. If Spike cannot lock-on you don’t fire and wait for a better image. IDAS is already in flight so the shot is wasted.
• In all but the Plus version Spike requires a lock-on before firing, not afterwards. The Plus version relies on a bi-directional fiber optic link to provide steering commands until the missile lock-on is achieved. The IDAS fiber optic link is apparently only for confirming the target after lock-on because of concerns that the line will be severed is the sub is forced to maneuver, this is apparently not considered a problem with the Spike Plus.
• Tracking a helicopter with active sonar?
• Radar, that will work. Of course you are at periscope depth to deploy it (<18m) and very vulnerable, but at that depth and with the data input there are higher performance weapons that can be vertically launched, and have the ability to engage aircraft as well has helicopters. The launch will be much more obvious, but since you are giving away your position with the radar anywhere, that is not much of a loss and gives you more time to evade.

The system operating requirements are very different, hence the differences in seeker performance required.

 

[Firn]

I think we are not quite on same page. This will be my last post about the specific issue, as I don't think a further debate won't be anymore fruitful:

The Spike has a much shorter range (8km vs. 20km). To lock-on to a target at the longer range the IDAS would need a seeker 6.5x more sensitive than the Spike’s to achieve equal performance. It is simple physics.

It is all but simple physics, as one has to first comprehend the whole system to understand why Diehl is considering not only the 'high-performance and all aspect seeker' of IRIS-T.

Diehl initially considered using the IRST seeker for IDAS, however, this high performance and all aspect seeker may not be the only option, and other seekers might be considered to pick up the target, provided with passive cuing from by the submarine sonar. The submarine can acquire ASW helicopter when submerged, by localizing the ripple effect created by the rotor downwash.

I posted the video of the Spike to showcase it's basic interplay. In IDAS case even with a not so high performing seeker the missile will be cued with enough accuracy through the two-way optical link to acquire and lock autonomously on to the target. The crew can manage the fire-and-forget missile during it's flight.

According to Diehl, the accuracy of such cuing system is adequate to provide bearing and range, bringing the missile seeker to autonomously acquire the target with high level of confidence. The fiber optical link would then be used by the crew to verify the target, confirm the intercept and perform battle damage assessment.

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IDAS has to be able search for its target, Spike does not. This allows Spike to have a narrower field of view of view and even less sensitive seeker. If Spike cannot lock-on you don’t fire and wait for a better image. IDAS is already in flight so the shot is wasted.

Once again the Spike missile was just a showcase, as the video was readily available. And once again according to Diehl, 'the accuracy of such cuing system is adequate to provide bearing and range, bringing the [not so high performing] missile seeker to autonomously acquire the target with high level of confidence.

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In all but the Plus version Spike requires a lock-on before firing, not afterwards. The Plus version relies on a bi-directional fiber optic link to provide steering commands until the missile lock-on is achieved. The IDAS fiber optic link is apparently only for confirming the target after lock-on because of concerns that the line will be severed is the sub is forced to maneuver, this is apparently not considered a problem with the Spike Plus.

The optical link of IDAS is of course bi-directional, it would not make much sense otherwise, wouldn't it?

During the total duration of its employment until the impact on the target there is a bi-di-rectional data connection between submarine and missile via an optical fiber link.

See the Source

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Tracking a helicopter with active sonar?

Please read again what I wrote:

...handle relative slow targets like choppers, not speaking of ships and land targets. Cuing could be achieved by passive and active sonar or radar, depending on METT-T, while the lock-on will be achieved by CCD/IIR.

I guess it should be clear that in this case the active sonar could be used to cue the missile to a relative slow (or still) target like a ship. Needless to repeat again that of course the cuing by passive sonar will by far the prefered modus operandi.

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Radar, that will work. Of course you are at periscope depth to deploy it (<18m) and very vulnerable, but at that depth and with the data input there are higher performance weapons that can be vertically launched, and have the ability to engage aircraft as well has helicopters. The launch will be much more obvious, but since you are giving away your position with the radar anywhere, that is not much of a loss and gives you more time to evade. [/list]

This would be use d) in an environment which contains no big threat to the submarine but is more of a cloak-and-dagger mission against unprepared (civilian/military) targets. It should be a very rare case indeed.

 

[the road runner]

Not sure were to post this, after seeing James Cameron dive in a sub to the bottom of the Mariana's trench i was amazed at the depths he reached.Of note was how the sub was built in Sydney,Australia by Ron Allum.The Plastic/foam surrounds of the sub are an Australian design.

James Cameron’s giant dive for mankind - Environment - Macleans.ca

It is remarkable to see the depths(10,989 meters) this sub went to.Its just mind boggling.Talk about a Lab rat in a sprite can.

Has any news come to light on the path Australia will take for its future subs?
Just curious is all.Am seeing alot of conflicting write ups, on Collins replacement

Regards

 

[exPrivate]

Sorry, I haven`t read the thread very carefully, but I wonder what is the actual depth where some sub clases operate. Almost every material on the web that I came across was sth like "over 300 m", and its only fun, nth more...

 

[Cadredave]

Sorry, I haven`t read the thread very carefully, but I wonder what is the actual depth where some sub clases operate. Almost every material on the web that I came across was sth like "over 300 m", and its only fun, nth more...

Thats a capability and most capabilities are classified secrete for a vey good reason hence you will not find the actual depth anywhere on the web, thats why its something generic like over 300m etc.

 

[gf0012-aust]

Sorry, I haven`t read the thread very carefully, but I wonder what is the actual depth where some sub clases operate. Almost every material on the web that I came across was sth like "over 300 m", and its only fun, nth more...

the reason is that actual depth is classified.

eg it impacts upon how people design sensors, weapons systems, etc....

it also lets enemy engineers start to be able to make design calculations etc if they know actual depth limits. eg innovations in design, steel used, features etc...

thats why estimates are always "broad" - its basic opsec

 

[exPrivate]

Thank you both! I supposed it`s the total classification of any info considering the subs. Still I remember just one place about Astute class where the depth was sth like "around 500 m". Just for the sake of variety I suppose.

 

[PO2GRV]

this one is a general question about submarine communication. Is it possible for assets to communicate with a submarine when that submarine is below periscope depth?

I worked as a maintainer in the TACAMO program for 5 years so I know how the Mighty Mercury has to deploy the antennae and fly doughnuts in the air to transmit to the boomers, but I wasn't certain if that specific type of communication was limited to those boats for security reasons or depth or emergency or what have you.

where I'm going with this is whether or not maritime patrol aircraft like the P3 or P8 or similar platform can communicate with a submarine if needed in an emergency if that submarine doesn't know it is trying to be contacted

 

[PCShogun]

Sorry, I haven`t read the thread very carefully, but I wonder what is the actual depth where some sub clases operate. Almost every material on the web that I came across was sth like "over 300 m", and its only fun, nth more...

Just to give you an idea HOW SECRET that information is: My father was in the navy for 23+ years, retiring CWO3 (Chief warrant Officer). I have asked him that question periodically for over 40 years and he STILL gives me, his own son, the same answer, "In excess of 300 feet".

Read enough material and you will get a much better idea of just how far down these subs can really go. It is amazing. They no longer use the Steinke Hood to escape a submarine at depth, now they use the SEIE (or Submarine Escape Immersion Equipment) this works up to 600 feet down, and modern subs go down further than that.

 

[exPrivate]

That`s a jolly good point, PCShogun!

 

[EXSSBN2005]

this one is a general question about submarine communication. Is it possible for assets to communicate with a submarine when that submarine is below periscope depth?

I worked as a maintainer in the TACAMO program for 5 years so I know how the Mighty Mercury has to deploy the antennae and fly doughnuts in the air to transmit to the boomers, but I wasn't certain if that specific type of communication was limited to those boats for security reasons or depth or emergency or what have you.

where I'm going with this is whether or not maritime patrol aircraft like the P3 or P8 or similar platform can communicate with a submarine if needed in an emergency if that submarine doesn't know it is trying to be contacted

We recieved strat messages telling us to come up in short letter bursts (on VLS) that were coded to individual subs. They make bouys/sonor pods that can transmit sounds other than pings and could be set to sink to sub depth asking it to come up and what not, but I'm not sure the sub would be comming up unless they heard that the plane was in trouble.

[ame="http://en.wikipedia.org/wiki/Very_low_frequency"]Very low frequency - Wikipedia, the free encyclopedia[/ame]