Chinese cruise and anti-ship missiles

Noisy aircraft carrier propeller

Fact 1: Giant carrier propeller generates huge amount of energy.



Fact 2: A SOSUS-like system can "detect acoustic power of less than a watt at ranges of several hundred kilometers." The carrier propeller is generating an unimaginably greater amount of energy "than a watt." For comparison, the light bulb in your room is probably 100 watts. 100 watts cannot spin a carrier propeller.



"SOSUS systems consisted of bottom mounted hydrophone arrays connected by underwater cables to facilities ashore. The individual arrays were installed primarily on continental slopes and seamounts at locations optimized for undistorted long range acoustic propagation. The combination of location within the ocean and the sensitivity of arrays allowed the system to detect acoustic power of less than a watt at ranges of several hundred kilometers."

Fact 3: Using the data from a SOSUS-like system, the location of an aircraft carrier can be determined through acoustic location. "Multiple passive sonars can be used for range localization by triangulation or correlation, directly."



"Sonar

SONAR (SOund Navigation And Ranging) — or sonar — is a technique that uses sound propagation under water (or occasionally in air) to navigate, communicate or to detect other vessels. There are two kinds of sonar — active and passive. A single active sonar can localize in range and bearing as well as measuring radial speed. However, a single passive sonar can only localize in bearing directly, though target motion analysis can be used to localize in range, given time. Multiple passive sonars can be used for range localization by triangulation or correlation, directly."

Final step: Transmit the data for the location of the carrier to China's ASBMs. ASBMs will be raining down on the carrier group. [Just remember, the tracking technology works both ways. If China builds an aircraft carrier, the U.S. can easily track it with SOSUS. This is simply physics.]

Optimizing SOSUS-like system

Just like in SOSUS, China's hydrophones will be located near the continental shelf. "The individual arrays were installed primarily on continental slopes and seamounts at locations optimized for undistorted long range acoustic propagation." (see )

Fact 1: Location of China's hydrophones are already roughly 350 Km out to sea (e.g. equivalent to 210 miles; if you use nautical miles then the distance is pushed out a little further).



"The continental shelf between China and Japan is 325 nautical miles in width at maximum, 167 nautical miles at minimum and 216 nautical miles in average, ..."

Fact 2: SOSUS-like system can "detect acoustic power of less than a watt at ranges of several hundred kilometers."

Putting facts (1) + (2) together, this means that if a carrier propeller generated less than a watt of acoustic energy then China's SOSUS-like system can detect an aircraft carrier out to 650 Km or more.

Math: Hydrophones are located 350 Km from coast on continental shelf + several hundred kilometers (e.g. 300 Km or more) = ballpark 650 Km range.

Fact 3: Giant carrier propellers generate an enormous amount of acoustic energy as they spin and push a 100,000 ton aircraft carrier through the water. An extremely conservative detection range of the carrier's propellers is at least 950Km or roughly 1,000 Km.

Hydrophones can detect the acoustic energy of giant carrier propellers at distances far in excess of a mere "several hundred kilometers." Despite the incredibly noisy carrier propellers, we'll be extremely conservative and add a mere 300 Km to the hydrophones' existing detection range. In reality, the hydrophones' detection range will be far in excess of 300 Km because the acoustic energy level jumped from "less than a watt" to "something really huge."

Fact 4: The acoustic data from the hydrophones are "undistorted." SOSUS-like hydrophones are intentionally placed at "seamounts at locations optimized for undistorted long range acoustic propagation." (see )

Fact 5: Combine the acoustic data from China's SOSUS-like system and use "acoustic location" and triangulation to determine location of carrier (see ).

Final step: Transmit the data for the location of the carrier to China's ASBMs. ASBMs will be raining down on the carrier group.


[Note: A quick comment on the level of the carrier propellers' acoustic energy. I use a description like "something really huge" because I don't know the exact figure. Also, the figure will change depending on the speed of rotation of the propeller.

Knowing that a Nimitz carrier has two reactors that can each generate up to 190 MW doesn't get me very far. What proportion is used for onboard electrical use and what proportion is directed to the four bronze propellers? Does anyone also happen to know the "loss" rate in mechanical energy transmission? Just like the powertrain in your car, energy is wasted in the transmission system and driveshaft.

Next, does anyone know what proportion of the propeller's energy is consumed by productive kinetic energy conversion and what proportion is converted into acoustic energy? I don't know the answer to that question either.

Finally, I don't think that it's important to become obsessed over what I consider to be an unimportant minor detail. Take one look at the wake of an aircraft carrier and you can tell that a "really huge" amount of acoustic energy is helping to make those bubbles. Common sense should indicate that China can probably locate the aircraft carrier a lot further than 1,000 Km.]

Avoid thermoclines



Take a look at the picture of the continental shelf. Arrays of hydrophones can be placed in water that is no deeper than 100m to avoid thermoclines. Or, if you're willing to spend the money, a country can place arrays of hydrophones at different depths along the continental slope. This approach would be similar to the placement of hydrophones at different depths by a group of U.S. destroyers with their towed array detectors.

To repeat, water that is 100m or less form essentially one layer. Arrays of hydrophones in 100m or less can avoid a thermocline and easily detect the sound of an aircraft carrier propeller.

I never claimed that it was easy. However, the physics is pretty straightforward. China has the sicentists, technology, money, and computer processing power to utilize a 49 year-old technology to find a "really huge" carrier propeller acoustic source. Why is that a big deal? It's a lot easier than building a sophisticated Aegis-class destroyer, which is NOT a 49 year-old technology.



"Waves mix the water near the surface layer and distribute heat to deeper water, such that the temperature may be relatively uniform for up to 100 m (300 ft), depending on wave strength and the existence of surface turbulence caused by currents. Below this mixed layer, however, the temperature remains relatively stable over day/night cycles. The temperature of the deep ocean drops gradually with depth."


"Graph showing a tropical ocean thermocline (depth vs. temperature). Note the rapid change between 100 and 200 meters."

Using SOSUS for tracking and targeting

For those of you who don't have your minds stuck in the Dark Ages, this is very simple.

49 years ago, the United States built passive sonar detectors to find Soviet submarines. The United States placed the detectors at the appropriate thermocline suitable for submarines. Using triangulation, the United States was able to determine the location of Soviet subs.

Today, China has a different use for passive sonar detectors. China wants to find the location of U.S. carriers and destroyers. China's task is immensely easier because 100,000 ton aircraft carriers are noisy as hell and nothing like extremely quiet nuclear powered submarines. China will place her hydrophones in the appropriate thermocline for surface ships.

Using the same principles of trigonometry that all of us learned in high school, China can triangulate and determine the position of U.S. carriers. You may not like the result, but too bad.



"SOSUS, an acronym for SOund SUrveillance System, was a chain of underwater listening posts located for the most part across the northern Atlantic Ocean near Greenland, Iceland and the United Kingdom -- the so-called GIUK gap. It is operated by the US Navy originally with the purpose of tracking Soviet submarines, which would have had to pass through the gap in order to attack shipping in the Atlantic. A selection of sites in other locations in the Atlantic and Pacific Ocean have also had SOSUS stations installed.

SOSUS development was started by the Committee for Undersea Warfare in 1949, a panel formed by the U.S. Navy in order to further research into anti-submarine warfare. At the time the main concern was snorkeling diesel submarines, and the panel quickly decided that the solution was to use low-frequency sound detectors which would be able to hear the sound of their engines from hundreds of kilometres. Each site would consist of several detectors, allowing them to triangulate the position of the submarine. They recommended that $10 million be spent annually to develop such systems."

Propellers emit a broad range of acoustic frequencies

Propellers emit a wide range of noise levels over a spectrum. Noise data for the propellers of a Nimitz U.S. aircraft carrier is not available. The next best analog is a giant cruise ship. In the following article, you will learn that a cruise ship's propellers emit a broad range of frequencies and the spectrum changes depending on the speed or rpm (i.e. rotation per minute) of the propeller blades.



The paragraphs cannot be copied. Please read "3. Spectral Representation, 4. Volendam Signature, 5. Dominant Signature Components, and 6. Perspective" on pages 3 and 4.

A quick summary is that the large propellers of a cruise ship emit noise frequencies in a wide spectrum. The composition of high, mid, and low frequencies change depending on propeller speed. A Nimitz carrier propeller blades will behave similarly and emit a spectrum of high, mid, and low frequencies.

Here is the bottom line.


Using 49 year-old hydrophones, the United States could detect the tiny acoustic energy (e.g. look at the tiny wake) of a submarine and triangulate its location.



Using modern advanced hydrophones with far greater sensitivity, 49 years of technological improvements, and incomparable computer-processing power to identify the signal, someone is making the claim that this HUMONGOUS acoustic energy source cannot be detected within 300 Km to 600 Km of the modern advanced hydrophones and that triangulation is not possible. I think he's nuts.

Conservative range via SOSUS-tracking of China's ASBM is 935.2 Km

China's continental shelf varies. We will place the hydrophones as far out as possible. "The continental shelf between China and Japan is 325 nautical miles in width at maximum."

1 nautical mile = 1.852 kilometers

325 nautical miles x 1.852 Km/nautical mile = 601.9 Km

Low frequency sonar is effective out to 200 miles or 333.3 Km.

Total range of hydrophones is 601.9 Km + 333.3 Km = 935.2 Km

935.2 Km is pretty close to 1,000 Km. The range of 935.2 Km is an effective deterrent for China's ASBM.

Thanks Martian for the very detailed presentation of the type of weapons and detection method that China had against possible attack or threat from enemy's from the sea.

However I am wondering, unless China is actively seeking for the carrier battle group, the method as stated might be difficult to locate the battle group, the ocean is a massive place to be.

The ASBM had a range of around 2km and had been tested (at least from available data and the photo that you have shown) to be effective. However what we are seeing was a stationary target on ground, how effective it is when it was to be used against moving target. A carrier in the ocean is like a speck of dust. The carrier is not just moving in a straight line, it could move in at least 2 dimensions. Plus the water is not also calm and non moving, so the adding the current and the updown, it would provide a third dimensions movement.

If you look at the map on post #120, you will notice that the U.S. has a listening post in the middle of the Atlantic Ocean. Similarly, China can sprinkle additional listening posts throughout the Pacific Ocean by placing them on natural formations (e.g. near islands) or constructing artificial structures.

As I understand it, triangulation should provide a precise three-dimensional coordinate. Let's use a bath tub as an analogy for an ocean. You have a rubber ducky floating on the choppy waters of your bath tub (e.g. push the water with your hand to create some choppiness).

Now place three listening stations in different parts of your bath tub. You know the precise location of your own listening stations. Let's pretend that the rubber ducky is splashing the water like mad with its imaginary feet.

Take a string and connect one of your listening stations to the noisy rubber ducky. Take a second string and repeat the exercise. You should have the precise three-dimensional coordinate of the rubber ducky. The third listening post serves as redundancy and it may help to increase the accuracy in pinpointing the rubber ducky. In general, the more listening stations that you have, the more precisely you can locate the rubber ducky.

Back to the real-world example. Swap rubber ducky for aircraft carrier and bath tub for ocean. You should have the precise three-dimensional location of the aircraft carrier.

The problem is that one can obscure the location by operating close to shipping lanes, but far enough to avoid being visually spotted by civilian ships. This will create false contacts on a hydrophone. If you send satellites to look at such locations, one can hide from them by ducking into cloud cover or weather fronts and courses can be changed since such systems are in known orbits, are predictable, and their sensing capabilities known. To further aid such a deception, deceptive lighting is used at night so that the obvious "blacked out warship" is instead thought to be a merchant or cruise liner.

On the ESM count, surface search radar identical to commercial ones are used. Turn count masking is used by the ships. Aircraft maintenance on the CV and other helo equipped ships is limited to prevent transmissions. So you may have contacts, but you can't tell if the ship is military or a civilian.

Additionally, don't think the Americans will leave such posts alone; the Americans might choose to level such installations with aircraft or cruise missiles quite easily. Or, they can send special forces to neutralize such locations. Or, they can send submarines to cut your hydrophone lines. In fact, such installations will probably be the first targets destroyed in any war, as you want to blind your enemy's early warning system, followed by his command and control systems.

Pointblank said:

The problem is that one can obscure the location by operating close to shipping lanes, but far enough to avoid being visually spotted by civilian ships. This will create false contacts on a hydrophone. If you send satellites to look at such locations, one can hide from them by ducking into cloud cover or weather fronts and courses can be changed since such systems are in known orbits, are predictable, and their sensing capabilities known. To further aid such a deception, deceptive lighting is used at night so that the obvious "blacked out warship" is instead thought to be a merchant or cruise liner.

On the ESM count, surface search radar identical to commercial ones are used. Turn count masking is used by the ships. Aircraft maintenance on the CV and other helo equipped ships is limited to prevent transmissions. So you may have contacts, but you can't tell if the ship is military or a civilian.

Additionally, don't think the Americans will leave such posts alone; the Americans might choose to level such installations with aircraft or cruise missiles quite easily. Or, they can send special forces to neutralize such locations. Or, they can send submarines to cut your hydrophone lines. In fact, such installations will probably be the first targets destroyed in any war, as you want to blind your enemy's early warning system, followed by his command and control systems.

Click to expand...

In a real crisis betwen USA and china, i dont think you will find much commercial shipping in a war zone. Chances are in fact, you wont find any. Both contenders will order civilian ships away.

another thing: how does the USN know where are the chinese hydrophones?