Why are submarines so hard to detect even with modern equipment?
In: Engineering
Once you’re a few hundred feet under water radio (and thus any radar type thing) doesn’t work. Optical doesn’t work either. The only thing that works is sound.
The big problem is sound really doesn’t travel that well, and there is a lot of space in the ocean and a lot of things that make noise. You can’t just get a super good microphone, that won’t pick them up, you’ll just hear the animals nearby really well.
Think of it like this, I’m going to get 5 people, with nice loud trucks and blasting the radio 24×7, so loud anyone within a mile of them can hear it. You try to find them, you can have 10,000 people searching and all the tech you dream up. But my 5 guys are going to random spots in North America and they get head starts, you have to search 9.5 million square miles, your 10,000 guys can listen to 40,000 sq miles of land at a time, and my guys will be heard in 20 sq mi of land at a time. So you can search 0.4% of the land area with the 10,000 guys, and I can only be heard in 0.0002% of the land. There is essentially zero chance any of your guys can find me.
The ocean is a whole lot bigger, and you need very high end tech to hear something that is designed to be quiet from a mile. Also, you don’t have 10,000 ships to search with. It is really really hard to find them.
_~~Cobb~~ COB, I was just teaching_ seaman _Beaumont here the intricacies of modern sonar.._ Yeah, I ain’t Cheif of the Boat, Im Sheena, Queen of the jungle.
So, there are two types of sonar. One is active. You send out GIANT acoustical pings like a whale or dolphin use for echolocation and they bounce off another submarine, or ships, or rocks or schools of fish. Give you a very clear picture of what’s underwater. Now, whether or not it’s a loud reverberating CLONG like in Red October, Ill leave to an actual submariner, but the problem with active sonar is… well, its loud. It gives away YOUR position as much as the bad guys, so we’re not gonna talk about it here.
Passive sonar is just listening to sounds transmitted through the water. Problem is, the sea is _extremely loud_. And noises, particularly low-frequency ones, travel quite a long way. So if you are lucky to pick the sound of noise out of the clutter of the surface waves, the squid and fish and methane bubbling out of volcanic vents, it could be a ship or submarine that is very very far away (_Including one waaaay out of Pearl!_). So lots of computer processing is needed.
On the other hand, naval surface ships to some degree, but submarines as a matter of course, have been designed for the past 80 years specifically to be as quiet as possible. Anything that can vibrate, cavitate, or make any noise is isolated from the outer skin of the hull by an air gap or rubber padding or both. The hulls of submarines are streamlined and smooth, possibly coated with sound-absorbing/dampening rubberish material, and designed to sleekly open a gap in the water ahead of them and let the water merge back together behind it. Stealthy like.
Nuclear submarines have a lot of motors and pumps and stuff that have to run continuously, so they’re actually quite noisy (the tradeoff is they don’t need fuel for decades). When they talk about a diesel submarine sneaking up and killing a carrier say, what they mean is a Deisel electric submarine, running on its batteries and electric motors only. The diesel engine is off and is only used out of battle to recharge its batteries.
Because if you try and “ping” everyone in the neighborhood knows where you are. So its much safer to try and listen for the noise the crew themselves make. And why don’t bases in the coast try find everyone because then they reveal where the are and some submarines are armed with guided missiles that are design to destroy bases
It’s a complicated topic that takes a fair amount of training to comprehend and utilize, but the key point is that the sound a submarine makes simply doesn’t reach the detectors.
* Submarines are designed to be quiet. The details of these design features is classified.
* Detection ranges in naval warfare are great enough that they are typically rounded to thousand-yard increments.
* Any detector needs to overcome its self-noise, noise from sealife, and other ocean noises (like waves) and pick out and identify the specific noise of the Submarine.
* Sound doesn’t travel linearly in the ocean. Due to changes in temperature, pressure, and salinity, sound waves will refract in their path through the ocean, which means that the sound waves simply won’t reach certain areas regardless of how good the detector is.
What makes you think they are hard to detect first off? I personally tracked a Russian Victor III at over 100 miles passively from onboard the USS Leyte Gulf. What can cause hardships:
1. The detecting unit doesn’t know ASW. Its a different type of warfare and the ship is married to the mission. It has to be practiced and that is not done these days.
2. Water is fucky. It can make sound bend based on pressure, temperature and salinity. Attenuation. Spreading. Snell’s Law. There’s a lot of sciencey shit that complicates things.
3. Active (ping), passive (listen), sonobuoys (active and passive), SOSUS, SURTASS, Submarines, MAD, LIDAR….each has its use case and challenges.
4. There are also differences between submarines in terms of modern quieting and application of stealth. Some countries have them strictly for coastal defense. Some never get underway and are only there on paper. The quietest sub operated by a dickbutt will get found faster than a relic sub operated by someone skilled. MOST countries land solidly in the dickbutt category as their submarines never get underway.
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