Yuan Class AIP & Kilo Submarine Thread
- Thread starter Jeff Head
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Well, I would say it's the first time that we've seen two openings for what could be towed arrays above the waterline.
(Considering towed array openings can very much be below the waterline as well)
For submarines with two towed arrays they're often of different lengths and one would typically be a "thick" line and one would be a "thin" line covering different frequencies with different apertures, and my understanding is some are better for different depths (thick lines generally not suitable for shallower depths).
That said the specific roles are a bit beyond me, but it is generally well accepted that two towed arrays are the current gold standard for submarine towed array sensor fits.
plawolf
Lieutenant General
With two towed array lines, you can also use the separation between them and the small time difference between them picking up the same signal to add significantly more data points to use to analyse the signal.
You can also use weights and buoyancy devices in the arrays to increase the separation and angles of the arrays to give yourself significantly more data points, but I am not sure if subs do that.
You can also use weights and buoyancy devices in the arrays to increase the separation and angles of the arrays to give yourself significantly more data points, but I am not sure if subs do that.
yes, more capable towed array system was always way more likely of an explanation than VLS to me.
The extra length could be anything.
If this is a mini-nuke (which I have my doubts), it's self explanatory.
If it's another conventional sub, you would need more space for more powerful Stirling engine, computation and LFP battery storage.
The extra length could be anything.
If this is a mini-nuke (which I have my doubts), it's self explanatory.
If it's another conventional sub, you would need more space for more powerful Stirling engine, computation and LFP battery storage.
TL;DR: optimisation of array for better signal processing due to limited computing power of a submarine.
Explanation for those wo don't know what this means or are unsure of their understanding:
Quantum mechanics applies to all scales. We simply don't have a model that describes it outside of realm of fundamental particles.
Particle/wave duality that we know empirically and are completely confused by intuitively from particle physics applies to macroscale and in a way that is much more intuitive but not very helpful for building quantifiable models.
Acoustic pressure (sound) waves are also "particles" that is physical objects that interact with other objects according to statistical/probabilistic rules. This means (among other things) that objects can interact with each other depending on how similar they are - a "lock and key" principle. For example protons interact well with neutrons or electrons forming different atoms but not with quarks or molecules - there they become either ineffective or destructive in their interaction.
Sonar operates on the principle of wave mechanics and waves being physical objects have physical magnitudes. Short wave is literally short. Long wave is literally long. Lock and key means that short keys fit in short locks and long keys fit in long ones.
This translates to the principles of antenna design. Antennae have to be matched to the physical characteristics of a wave to be the best receptor of signal. For long waves - that is waves of low frequencies - a long antenna is best. For shorter waves - that is waves at higher frequencies - a shorter antenna is best. In this case antenna means the individual receptor and not the entire array which is a collection of receptors (receivers).
You can see that best in how radio antenna for different frequencies have different physical dimensions. A meter wave requires approximately a meter-long receiver, otherwise you can't really pick it up and part of the wave "slips by" the antenna and the signal is garbled. That is no longer the case with digital radio which transmits digital signal but in analog era it was common to need to extend the telescopic antenna in a portable radio to get better reception when tuning in because the signal was not numbers but analog copy of actual soudwave being recorded by the microphone.
Coming back to sonar: sonar is like radar - it is the device that uses transmission and reception of signal using wave mechanics to establish range and direction. The better the antenna the better the input data for calculations. And considering that noise levels of targets are going down while ranges and noise levels in the environment are going up having some of the problem solved by hardware is better than putting it all on the computers.
It is like the principle of quantum radar which ensures that you can always recognise which individual impulse is your signal no matter the distance and distortion even if you have a single echo because the quantum properties of the signal are encoded and then the filter only lets through echoes which match the quantum parameters.
Having two arrays means that you can tune your receiver to specific frequencies and energies of the wave as well as specific environments because ultimately wave is a distortion of a medium so the medium matters as much as the wave. Sonar array optimised for greater depth and open waters will be different from sonar array optimised for shallow busy waters where maneuvering is necessary.
Since increasingly submarine operations and warfare are about out-lurking your opponent having the information before your opponent is crucial.
However since submarines are submerged in water which is a horrible medium for staying interconnected with the rest of your forces (which is ironically why submarines were invented to begin with) they are necessarily limited by the amount of computing power that can be carried in a submarine.
This means that as information density increases - and it does because as range increases the area from where sound waves can originate increases geometrically, not linearly - there is less and less option for the computing power to be directed to sifting through noise. If you are using general purpose array the noise will always be there and the computer will have to process it before it can go to analysing the signal. If you are using specialised arrays you save a significant chunk of computing power meaning it can be directed to all other tasks.
To use a metaphor - you can be the best bird expert in the world but if you're watching the bird through a broken dirty lens of an old binosular you won't see much. Get a good lens and you don't need to be the expert because you can compare high fidelity image with a bird atlas on your lap.
Doppler radars are good example of that. Instead of building larger arrays and computers to separate signal from background echo noise a simple physical filter on doppler shifting of waves depending on their relative movement toward or away the receiver - which can be measured by a simple mechanism - provided a simple solution and allowed for look-down shoot-down radars which are small and light and can be carried by not only light fighters but also active-radar homing missiles that can hit reliably targets against the background of Earth while on a descending trajectory.
Hopefully this clears the problem.
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Assuming this new sub is conventional, it would be interesting to see what they are able to do with the latest tech & additional space.
Straight off the top of my head:
They can install a much larger LFP battery pack, with higher density and fast charging time than 039C. 3/4x total energy & cutting charging tech to a 1/4 of what it was before shouldn't be too difficult.
The combustion engine can become a lot more efficient. Currently generation diesel engines for trucks are over 50% in thermal efficiency.
The power modules can also be a lot more efficient. They electric motor/drive on EVs are over 90% now. No reason they can't increase it to well over 80% on submarine.
They can store more cryogenic oxygen to be used by AIP.
unless of course, they shifted to hydrogen fuel cell type of propulsion, but I think that's less likely.
The level of tech improvement in past 5 years in battery electric propulsion is so great that it would be silly not to take advantage of that.
Other improvements will be more powerful computer farms, the cooling and the noise isolation that need be installed around there.
Of course, more crew space. But I don't think the difference here will be that large, because greater automation will likely result in needing fewer sailors.
Straight off the top of my head:
They can install a much larger LFP battery pack, with higher density and fast charging time than 039C. 3/4x total energy & cutting charging tech to a 1/4 of what it was before shouldn't be too difficult.
The combustion engine can become a lot more efficient. Currently generation diesel engines for trucks are over 50% in thermal efficiency.
The power modules can also be a lot more efficient. They electric motor/drive on EVs are over 90% now. No reason they can't increase it to well over 80% on submarine.
They can store more cryogenic oxygen to be used by AIP.
unless of course, they shifted to hydrogen fuel cell type of propulsion, but I think that's less likely.
The level of tech improvement in past 5 years in battery electric propulsion is so great that it would be silly not to take advantage of that.
Other improvements will be more powerful computer farms, the cooling and the noise isolation that need be installed around there.
Of course, more crew space. But I don't think the difference here will be that large, because greater automation will likely result in needing fewer sailors.
Single towed array is like person with one ear, able to hear but not able to tell direction. Two towed arrays is like two ears able to determine direction, but not abled to tell which side of the plane of the two array, in human analog not able to tell sound from above head or below. Four towed arrays will be able to determine all directions around the axis of the sub. Sonar essetially works in the same principle of surround sound system in home cinema.
More arrays gives more elements than single array if the lengths are kept the same, which will give stronger signal, but the primary reason for more arrays is direction. If I were the navy I would prefer many shorter arrays of equivlant length than a single long array, afterall knowing enemy's presence without knowing where it comes from isn't much helpful.
More arrays gives more elements than single array if the lengths are kept the same, which will give stronger signal, but the primary reason for more arrays is direction. If I were the navy I would prefer many shorter arrays of equivlant length than a single long array, afterall knowing enemy's presence without knowing where it comes from isn't much helpful.
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What is this nonsense?
As you were writing this did it ever occur to you to verify how submarines were able to use single towed arrays for locating targets for almost half a century, ever since USS Los Angeles entered service in 1976?
Take a sheet of paper. Draw a line with points along it - this is your linear array and your hydrophones. Now draw a source of sound and depict the soundwaves as concentric circles propagating from the source. As the circles reach the linear array there is a visible delay in when each hydrophone registers the signal. That delay allows the computer to calculate the position of the source.
As you will see with sufficiently long array there are only two cases where a linear array can't determine direction. Those two cases are axial symmetries - left or right and up or down - when the spherical wavefront propagates with the same speed toward each end of the array. There is no single mathematical solution. But there is a practical one.
To remain undefined the source would have to be exactly in the middle of the array and stay there. As soon as the source shifts its position relative to the array there is a delay on the hydrophones. As soon as the hydrophone position shifts relative to the source there's a delay. All the sub needs is to speed up or slow down a little or change direction.
Here your argument would likely be that it still doesn't resolve for location above or below the array. Except it does.
Sound propagates in water at 1,5km/s which is a delay of 0,1 millisecond per 15cm. Humans are capable of tracking tenths of a second with some precision and are aware of passage of time measured in the hundreths but are not able to track it. For a machine tenth of a millisecond is trivial. So all you need to do is move your array at an angle downwards or upwards. This requires a change of depth of as little as 50m at a slow pace to register some delay on an array that is hundreds of meters long. Similarly if the source changes depth that will register on an array.
Furthermore sound in water propagates with different speed depending on depth:
Those differences are minimal but sufficient for a machine calculating delays on a long towed array. The sub simply dives deeper and compares the results.
But ultimately the main reason why it is not a problem is the time that sonar requires for measurement. Sonar - and in particular passive sonar - is not precise, especially at extreme distances. Therefore detecting targets requires a completely different amount of time for a submarine than it does for an aircraft. Submarines detect and identify targets over hours, not seconds or minutes. You never see that in a movie because it would make for one hell of a boring movie.
It is extremely unlikely that two sources mirror each other's course for such long time at extreme distances - which is only when towed arrays are used. If it's a closer distance then the towed array is retracted regardless of whether the direction is known or not and the sub switches to using bow array or flank arrays. Those are planar and not linear and have no problems detecting position in space.
And that's entirely besides the modern engineering solution of having the array consist of clusters of hydrophones arranged asymmetrically and electronically gated so that received signal can be filtered depending on extremely minimal delays across 10-20 cm of relative distance between hydrophones. The filtering is cyclical turning the hydrophones off and on in sequence and that is enough to establish general direction.
And no, sonar doesn't work on the same principle as surround sound system in home cinema because the "r" in sonar stands for ranging. Sonar is short for "sound navigation and ranging". If you think surround sound has "ranging" you need to see a psychiatrist. Take a seat right next to the people who brought proof that 5g gave them covid.