SUBSIM Radio Room Forums - View Single Post - Should we start a topic on basic tactics?

ET2SN · 11-02-17, 04:14 AM

So, what is situational awareness?
For the purposes of this post, I'm limiting this topic to submarines.
For most of the time you are limited to one type of sensor, sonar. There are no windows to look out of because below 50 feet there is nothing to see.
Sonar provides you with three or four basics. The sound from another contact, ie something is out there, the direction that sound is coming from, and the contact's Blade Count. If the contact is loud enough your sonar crew and their equipment can also take that sound apart and isolate the frequencies its made of.
Blade Count (or Turn Count) is a freebie as long as you're confident in what type of ship is making the sound. If you know the Blade Count and the ship type (or "class") you can derive the speed the contact is travelling. You also get one more freebie, and its always the first sonar screen you should check, your sound velocity profile. If you have a strong layer, make note of where the boundry is in case you'll need it later.

So let's take a minute to look at what these sounds represent. Ships make noise. There are machines constantly running inside the hull- motors, generators, the main engine, laundry machines, you name it. Those sounds radiate from the hull into the ocean. Different ship classes produce different frequencies of noise. Most ships also use one or more propellers (from now on, we'll call them Screws) to move the ship along its way. The screws generate their own noise as they rotate. As long as we know how many blades are on a screw we can calculate how many RPMs that screw is turning and from that we can make a very good guess at how fast the ship is travelling. Its worth noting that the lower the frequency of the sound, the better it travels through water. This is why you'll always detect the 50 or 60 hertz tone in narrow band first. BTW, 50 and 60 hertz aren't magic. They are based on standards for generating electrical power. Some countries like the US use 60 hertz as a standard while most of Europe uses a 50 hertz standard.

OK, enough of that, let's get back to being aware. We're on a sub so we don't have a lot of information to use. All we have is sound coming from a direction.
We can make a pretty good guess what's causing that sound and how fast its moving. We can also focus on the direction and how that direction changes over time.
These are the basic fundimentals of TMA, or Target Motion Analysis. One thing you absolutly have to understand is that TMA is NOT the same thing as looking at the radar display in a fighter jet or helo. Radar is NOW and its accurate while TMA is a prediction over time. Say it out loud so I'll feel better, "TMA is a prediction over time". TMA is NEVER going to be as accurate as a radar locked onto its target. TMA is based on the assumtions you make. You need to factor in Time to make sure those assumptions aren't falling apart. The first assumtion you have to make is a big one. The target is moving at a constant speed and travelling on a constant course. Do me a favor and read those last two sentances again, this seems to be something that causes a lot of confusion or gets ignored.
You can change your speed and direction to see how it effects your solution, in fact you'll want to do this to refine your solution. If your target changes speed or direction, your solution is now garbage and you have to go back to "square one" with your solution and start over.
Your next assumption is that your target is travelling towards you. You don't know his course for certain, yet, but its safe to assume that if you picked him up at long distance and you're still tracking his sound, he's closing towards you. The only time you can't make this assumption is if you deploy your towed array and all of a sudden you get a nice, bright trace or spike in your broadband display. In other words, deploy the Toad and deploy the Toad early.

So, before this drifts into too much detail, what else is important when it comes to staying aware? While you assume your target is sticking with the first assumption, realize that targets WILL change course and speed at some point. These changes are known as a "zig" and its up to you to be able to spot one. If your sonar uses a "waterfall" display in broadband, learn how to spot the zig on it. You can create some simple missions of a single contact travelling towards you that turns or changes speed at a known point in time. Be aware that you should drop a solution after the contact passes its closest point of approach. Once that contact is moving away the calculations will change but those calculations will screw up your current solution. Be aware that sonar has its advantages but it also puts blinders on you because you're forced to look into the present and future using old data. You also have other sensors but they come with a risk of detection. Learn when to use them and what their maximum effective ranges are.

11-02-17, 04:14 AM	#10
ET2SN ET2/SS Join Date: Oct 2017 Posts: 2,526 Downloads: 58 Uploads: 0	So, what is situational awareness? For the purposes of this post, I'm limiting this topic to submarines. For most of the time you are limited to one type of sensor, sonar. There are no windows to look out of because below 50 feet there is nothing to see. Sonar provides you with three or four basics. The sound from another contact, ie something is out there, the direction that sound is coming from, and the contact's Blade Count. If the contact is loud enough your sonar crew and their equipment can also take that sound apart and isolate the frequencies its made of. Blade Count (or Turn Count) is a freebie as long as you're confident in what type of ship is making the sound. If you know the Blade Count and the ship type (or "class") you can derive the speed the contact is travelling. You also get one more freebie, and its always the first sonar screen you should check, your sound velocity profile. If you have a strong layer, make note of where the boundry is in case you'll need it later. So let's take a minute to look at what these sounds represent. Ships make noise. There are machines constantly running inside the hull- motors, generators, the main engine, laundry machines, you name it. Those sounds radiate from the hull into the ocean. Different ship classes produce different frequencies of noise. Most ships also use one or more propellers (from now on, we'll call them Screws) to move the ship along its way. The screws generate their own noise as they rotate. As long as we know how many blades are on a screw we can calculate how many RPMs that screw is turning and from that we can make a very good guess at how fast the ship is travelling. Its worth noting that the lower the frequency of the sound, the better it travels through water. This is why you'll always detect the 50 or 60 hertz tone in narrow band first. BTW, 50 and 60 hertz aren't magic. They are based on standards for generating electrical power. Some countries like the US use 60 hertz as a standard while most of Europe uses a 50 hertz standard. OK, enough of that, let's get back to being aware. We're on a sub so we don't have a lot of information to use. All we have is sound coming from a direction. We can make a pretty good guess what's causing that sound and how fast its moving. We can also focus on the direction and how that direction changes over time. These are the basic fundimentals of TMA, or Target Motion Analysis. One thing you absolutly have to understand is that TMA is NOT the same thing as looking at the radar display in a fighter jet or helo. Radar is NOW and its accurate while TMA is a prediction over time. Say it out loud so I'll feel better, "TMA is a prediction over time". TMA is NEVER going to be as accurate as a radar locked onto its target. TMA is based on the assumtions you make. You need to factor in Time to make sure those assumptions aren't falling apart. The first assumtion you have to make is a big one. The target is moving at a constant speed and travelling on a constant course. Do me a favor and read those last two sentances again, this seems to be something that causes a lot of confusion or gets ignored. You can change your speed and direction to see how it effects your solution, in fact you'll want to do this to refine your solution. If your target changes speed or direction, your solution is now garbage and you have to go back to "square one" with your solution and start over. Your next assumption is that your target is travelling towards you. You don't know his course for certain, yet, but its safe to assume that if you picked him up at long distance and you're still tracking his sound, he's closing towards you. The only time you can't make this assumption is if you deploy your towed array and all of a sudden you get a nice, bright trace or spike in your broadband display. In other words, deploy the Toad and deploy the Toad early. So, before this drifts into too much detail, what else is important when it comes to staying aware? While you assume your target is sticking with the first assumption, realize that targets WILL change course and speed at some point. These changes are known as a "zig" and its up to you to be able to spot one. If your sonar uses a "waterfall" display in broadband, learn how to spot the zig on it. You can create some simple missions of a single contact travelling towards you that turns or changes speed at a known point in time. Be aware that you should drop a solution after the contact passes its closest point of approach. Once that contact is moving away the calculations will change but those calculations will screw up your current solution. Be aware that sonar has its advantages but it also puts blinders on you because you're forced to look into the present and future using old data. You also have other sensors but they come with a risk of detection. Learn when to use them and what their maximum effective ranges are.