How to detect and destory a nuclear submarine with shrouded propeller configuration

HMS Vanguard and Triomphant submarine collided in the Atlantic Ocean earlier this months. Such a rare event however hinted how stealthy they are that both could not detect each other on their sonar even just before collision. Both strategic missile submarines are the most advanced in their own country and have advanced sonar systems.


HMS Vanguard



Triomphant

I am pretty sure both submarines did not turn on their active sonars to protect themselves, as this would reveal their own locations. Passive sonar seems useless against submarines with shrouded propeller configuration and modern anechoic tile. Current submarines with such technologies are the Royal Navy Trafalgar-class, the US Navy Seawolf-class, the French Navy Le Triomphant class, and the Russian Navy Borei class. Other new submarines like the Virginia class are likely to be using similar technologies.

If countries with the most advanced sonar technologies can not detect these submarines, PLAN is most likely unable to detect them either. Since all other classes are strategic missile submarines they are less relevant in the event of a non-nuclear conflict, so the question goes to the USN Seawolf-class and USN Virginia class, and maybe some other new submarines. I am not sure whether they are detectable by active sonars or other devices. How much is the difference in capabilities between active and passive sonars? How could these submarines be detectd and defeated before they pose a threat?


USN Seawolf-class (SSN 21)



USS Virginia (SSN-774)

Re: How to detect and destory a nuclear submarine with shrouded propeller configurati

Why don't they just say is was a simple accident? They're simply trying to hide the embarrassment especially it sounds coming from the French side. Stealth or how advanced the technology had nothing to do with it. Unless they're covering-up the true damage, it sounds like a non-catastrophic bump. Which means they were at a slow speed that didn't do much damage. Which also means the slow speed made them less detectable and the advanced technology over other subs really had nothing to do with it. If you read some of these articles, they make it sound like subs have their active sonars on all the time.

Re: How to detect and destory a nuclear submarine with shrouded propeller configurati

Why don't they just say is was a simple accident?

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Exactly. That is all that happened. We were not on board so we don't know what sort of conditions were set as far as the use of sonar is concerned.

If you read some accounts they try to mix in the dangers of nuclear power and weapons in such a collision. In actuality there was very little danger.

Re: How to detect and destory a nuclear submarine with shrouded propeller configurati

Well the world is certainly having its share of bad luck, like that collision of a Russian satellite against an Iridium satellite. The odds are astronomical and yet it happened.

Anechoic tiles somehow lowers generated sound, but their main purpose is to absorb sound from active sonar.

I agree with Mace here. There is a bit of a media spin here to make it look like there is some virtue in it aka the subs must be so quiet they cant' detect each other.

Re: How to detect and destory a nuclear submarine with shrouded propeller configurati

It seems to me that the navies of the world would have figured out by now: keep your sensors on! The INS Eliat was hit off Lebanon largely because it didn't have its radars active, the Kitty Hawk was (possibly) embarassed in the sub surfacing incident because the task force apparently wasn't using much sonar, there's other incidents that I know have happened that are similar but I can't think of right now...and now this.

So let's get down to a more interesting discussion: how do you find and kill these ultra-stealthy subs? I for one have always thought that it might be possible to find water that had been heated to above normal temperatures by cooling the reactor with infrared technology of some kind.

Re: How to detect and destory a nuclear submarine with shrouded propeller configurati

The problem of finding is this. There are different levels of sound in the ocean. What you are looking is the level of background noise in the ocean. This is especially worst in the littorals and in areas that are heavily trafficked.

The idea is this. If your noise level is low enough, it will not be above the background noise but within or underneath it. When that is reached, even if the sound can be detected, how do you differentiate it from the hundreds or thousands of other sounds in the ocean? And do it in 30 seconds. If you got a car in the middle of the desert, you can hear its sound miles away. Put the same car in the middle of a traffic intersection and it totally disappears from the thousands of background noises. Think of trying to pick out the sound of a Toyota Prius in a busy intersection.

The old ways of looking at a scope won't work. The best help you can get is put a server farm on the ship or sub. That way, you can take a sound signature, match it to the thousands of sound signatures you have on the database, taking account using calculations of water differences in temperature, salinity and acidity, three factors that also affect sound transmission. The job is like spotting a face through a camera then having to match the face through an ID database.

Chances are the two subs that collided may have heard each other's sounds, but may not have identified the sounds quickly enough or perhaps even thought the sounds were not from a sub at all.

Also remember that passive sonars can't detect mines, which are totally quiet. You need active sonars to detect them, and that gives you away.

Subs are going to get stealthier, and I don't mean just with sound. Notice some subs now have a wedge look in them, like in the Gotland class, the Type 212 and 214 class, the Soryu class. This reminds me of planform alignment, and potentially it can reduce diffusion of echoes like it does with radar. This can reduce the subs signature from active sonars. Plus, if the sub is on the surface, the design will also further reduce the radar signature, and subs don't pop up on radar as easily as ships do already. To improve the radar stealthiness of the fin, for example, the base has to be thicker on the bottom so looking from the front, the sides of the fin would slope like a triangle pointing to the top. If there is a way to put the fin back to the hull that would even be better. An X tail on the back would also reduce the radar signature.

Re: How to detect and destory a nuclear submarine with shrouded propeller configurati

A couple of points. The prop is not the sole source of a sub's sound signature. There are various mechanical components such as pumps that lend a unique signature to each submarine ( and surface ship ).
Two, we don't know what the watch standers on these two subs were doing, or not doing, at the time of the collision. Neither may not have been manned up as they would be at action stations, so anything could have slipped by.

Re: How to detect and destory a nuclear submarine with shrouded propeller configurati

Finn McCool said:

It seems to me that the navies of the world would have figured out by now: keep your sensors on! The INS Eliat was hit off Lebanon largely because it didn't have its radars active, the Kitty Hawk was (possibly) embarassed in the sub surfacing incident because the task force apparently wasn't using much sonar, there's other incidents that I know have happened that are similar but I can't think of right now...and now this.

So let's get down to a more interesting discussion: how do you find and kill these ultra-stealthy subs? I for one have always thought that it might be possible to find water that had been heated to above normal temperatures by cooling the reactor with infrared technology of some kind.

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Subs have an infrared signature that is detectable. There is also a magnetic signature and in some cases a surface disturbance detectable by certain satellites. None of this is a slam dunk, but it does give the P-8 some information about where to expend their fuel.

Re: How to detect and destory a nuclear submarine with shrouded propeller configurati

Submarines often use demagnetized steel and there are demagnetization facilities where subs undergo routine treatment. Titanium of course, is non magnetic, and the Russians had a few subs built with it, terribly expensive.

Re: How to detect and destory a nuclear submarine with shrouded propeller configurati

crobato said:

Submarines often use demagnetized steel and there are demagnetization facilities where subs undergo routine treatment. Titanium of course, is non magnetic, and the Russians had a few subs built with it, terribly expensive.

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In general, a steel hulled sub, which is all but a small handful or Russian Sierra class boats, are detectable with MAD gear. Degaussing and other methods can reduce but do not eliminate a submarine's magnetic field. It can achieve some immunity from magnetic mines but not from MAD gear. In practice, when delivering a torpedo on a submarine from an aircraft, the MAD sensor is used as the final check on your datum. You fly directly over where you think the sub is and if the MAD gear registers you drop your torpedos. The P-8, since it flies very high, will have to operate differently.