Timerover51
SOC-14 5K
I had this request made of me in another thread, but thought that it might be more visible here. I had noted that there was no mention of sonar anywhere in the rules.
The problem with Sonar is that there is not one single sonar system for all uses, which is the problem with the "one size fits all" of the design sequence. Sonar also developed extremely fast under the pressure of World War 2 and then the view of the US Navy of the potential threat posed by large number of high underwater speed submarines of the Soviet Union, using WW2 German technology. What was standard in 1940 was not standard in 1945, and there was a new standard in 1950 and a new standard in the 1960s, with all of the previous systems still in use, and all still having some capability. Then you had the question of Active verse Passive Sonar for military use, which is still a major issue today.
As for current systems, you have a pretty wide range, depending on what you are using it for. The cost and size ranges widely too.
1. High-end fish finding systems: Your high end fish finding systems are pretty compact, easy to learn, and run about $3000. They are good for sidescan bottom search down to 125 feet, plus considerably deeper under the bottom depth profiling and 3D imaging, aside from doing nicely at locating fish. They are good for a quick bottom target survey for wrecks and underwater logs, will do very nicely to train personnel on sidescan sonar screen monitoring and use techniques, and could readily double as shallow-water bottom mine detection.
2. Dedicated wreck and underwater object location systems. Basically, those start with a sonar fish and a laptop computer, running about $30,000 for civilian models up to the $500,000 Echo that we used in the Solomon Islands when looking for PT-109. However, that it just the start. There is this thing called "fiber-optic cable" that connected the laptop to the fish that is underwater. That, and the winch to deploy it, can start at $75,000 and go up rapidly from there. As you need to be about 75 to 100 feet from the bottom for good sidescan work, if you are in 5000 meters of water, you need 7500 meters of cable that can handle the pressure. These are ultra-high frequency sets, so the range is not that great. For direct coverage of the area beneath the fish, you need a second bottom scanning sonar on the fish.
3. High-frequency directional beam ASW systems: This basically was the standard for WW2, and it still used for attack and accurate ranging work. Typically, the sonar will be extended from a compartment in the bottom of the ship, and mechanically trained in the desired search direction. Some are basic single beam, and some are monopulse beam for greater accuracy. The range is out to 1500 to 3000 yards reliably, if lucky, to 5000 yards. Unless capable of being tilted down, it does leave a dead zone under the ship.
2. High-frequency scanning sonar ASW systems: Basically a 360 degree scanning version of the high-frequency set covered above. Basically a cylinder formed of transducers that is electronically scanned for 360 degree continuous coverage, rather than needing to be trained about to get a wider area of scanning. Again, range limited by the high-frequency.
3. Medium Frequency directional and scanning ASW systems: Going to a lower frequency means going to a larger transducer array. It can still be deployed by lowering the transducer from the bottom of the ship, but takes up a lot more room. Range is out to roughly 6000 yards or so.
4. Low frequency scanning systems: The transducer is sufficiently larger as to not allow for mechanical training, so these are are pretty much straight scanning systems. Prior to being moved to the bow of surface ships, they were described a lowering or having a small boat underneath your ship, and did increase water resistance. Range of about 12,000 yards.
5. Very Low frequency scanning sets capable of directional beams from the transducer array: The array takes up about a 10 meter or so in diameter dome at the bow of the ASW ship, or the entire bow of the submarine. It has a direct range, under the right conditions of about 20,000 yards in the surface layer, but by using directional beams, can make use of the "Bottom Bounce" for "Convergence Zone" operations. The latest systems with a deep bottom below the ship, can reportedly reach about 75 nautical miles. The scanning rate at the range is pretty low, and a large part of the ocean can hear it.
6. Variable Depth Arrays: Because of problems with the sonar beam being trapped in the warmer surface layer, the variable depth sonar was developed to get below the layer with a towed sonar fish. This was good for high- and medium-frequency sonars, and still in use by some navies. The sonar fish was sometimes also used to tow a passive sonar array.
7. Passive sonar arrays: These can range from the WW1 directional hydrophone to complex towed arrays capable of not just bearing data, but also range.
8. Helicopter and Lighter-than-Air Flyer deployed systems: These can be either high-frequency active scanning systems or passive systems or active-passive systems. First deployed in early WW2, and are still in use.
9. Not sure if it is covered, but you also have airborne magnetic detectors. The Japanese fielded one in World War 2 that was quite comparable to the one used by the US Navy. It would still be useful if converted from vacuum tube to transistor operation.
One problem with any sonar, unless you are using an extremely high-frequency one and get lucky, you still have to identify the target. In the Solomons, once we sorted out which of the targets picked up by Echo looked possible, we then still have to visually inspect them. We had some nice views of what Bob called "geology", a couple of sunken Japanese landing barges, one Japanese destroyer is serious disrepair from having both its bow and stern magazines set off by hitting US naval mines, and the PT-109. All that took time to lower the Argus camera sled and attach the "Little Herc" tethered ROV to it. Five hundred meters means about 600 meters of cable out, and you do not lower or retrieve it fast.
One other thing, the first sonars were pretty cheap to build and use. The recent ones will run around a $100 Million dollars or so to installed with the bow-mounted transducer and an very large amount of signal-processing gear, along with the sonar controls. Basically, the sonar started very cheap and very light, and rapidly got very large and very expensive. So the Tech Level Stage Effects chart really does not apply. The transducer with generate the sound waves have not changed that much at all, the big difference between the early sets and now is the switch from vacuum tubes to transistors and printed circuits, and the use of computers with screens. Essentially, Tech Levels 5, 6, and 7 cover the entire period.
The problem with Sonar is that there is not one single sonar system for all uses, which is the problem with the "one size fits all" of the design sequence. Sonar also developed extremely fast under the pressure of World War 2 and then the view of the US Navy of the potential threat posed by large number of high underwater speed submarines of the Soviet Union, using WW2 German technology. What was standard in 1940 was not standard in 1945, and there was a new standard in 1950 and a new standard in the 1960s, with all of the previous systems still in use, and all still having some capability. Then you had the question of Active verse Passive Sonar for military use, which is still a major issue today.
As for current systems, you have a pretty wide range, depending on what you are using it for. The cost and size ranges widely too.
1. High-end fish finding systems: Your high end fish finding systems are pretty compact, easy to learn, and run about $3000. They are good for sidescan bottom search down to 125 feet, plus considerably deeper under the bottom depth profiling and 3D imaging, aside from doing nicely at locating fish. They are good for a quick bottom target survey for wrecks and underwater logs, will do very nicely to train personnel on sidescan sonar screen monitoring and use techniques, and could readily double as shallow-water bottom mine detection.
2. Dedicated wreck and underwater object location systems. Basically, those start with a sonar fish and a laptop computer, running about $30,000 for civilian models up to the $500,000 Echo that we used in the Solomon Islands when looking for PT-109. However, that it just the start. There is this thing called "fiber-optic cable" that connected the laptop to the fish that is underwater. That, and the winch to deploy it, can start at $75,000 and go up rapidly from there. As you need to be about 75 to 100 feet from the bottom for good sidescan work, if you are in 5000 meters of water, you need 7500 meters of cable that can handle the pressure. These are ultra-high frequency sets, so the range is not that great. For direct coverage of the area beneath the fish, you need a second bottom scanning sonar on the fish.
3. High-frequency directional beam ASW systems: This basically was the standard for WW2, and it still used for attack and accurate ranging work. Typically, the sonar will be extended from a compartment in the bottom of the ship, and mechanically trained in the desired search direction. Some are basic single beam, and some are monopulse beam for greater accuracy. The range is out to 1500 to 3000 yards reliably, if lucky, to 5000 yards. Unless capable of being tilted down, it does leave a dead zone under the ship.
2. High-frequency scanning sonar ASW systems: Basically a 360 degree scanning version of the high-frequency set covered above. Basically a cylinder formed of transducers that is electronically scanned for 360 degree continuous coverage, rather than needing to be trained about to get a wider area of scanning. Again, range limited by the high-frequency.
3. Medium Frequency directional and scanning ASW systems: Going to a lower frequency means going to a larger transducer array. It can still be deployed by lowering the transducer from the bottom of the ship, but takes up a lot more room. Range is out to roughly 6000 yards or so.
4. Low frequency scanning systems: The transducer is sufficiently larger as to not allow for mechanical training, so these are are pretty much straight scanning systems. Prior to being moved to the bow of surface ships, they were described a lowering or having a small boat underneath your ship, and did increase water resistance. Range of about 12,000 yards.
5. Very Low frequency scanning sets capable of directional beams from the transducer array: The array takes up about a 10 meter or so in diameter dome at the bow of the ASW ship, or the entire bow of the submarine. It has a direct range, under the right conditions of about 20,000 yards in the surface layer, but by using directional beams, can make use of the "Bottom Bounce" for "Convergence Zone" operations. The latest systems with a deep bottom below the ship, can reportedly reach about 75 nautical miles. The scanning rate at the range is pretty low, and a large part of the ocean can hear it.
6. Variable Depth Arrays: Because of problems with the sonar beam being trapped in the warmer surface layer, the variable depth sonar was developed to get below the layer with a towed sonar fish. This was good for high- and medium-frequency sonars, and still in use by some navies. The sonar fish was sometimes also used to tow a passive sonar array.
7. Passive sonar arrays: These can range from the WW1 directional hydrophone to complex towed arrays capable of not just bearing data, but also range.
8. Helicopter and Lighter-than-Air Flyer deployed systems: These can be either high-frequency active scanning systems or passive systems or active-passive systems. First deployed in early WW2, and are still in use.
9. Not sure if it is covered, but you also have airborne magnetic detectors. The Japanese fielded one in World War 2 that was quite comparable to the one used by the US Navy. It would still be useful if converted from vacuum tube to transistor operation.
One problem with any sonar, unless you are using an extremely high-frequency one and get lucky, you still have to identify the target. In the Solomons, once we sorted out which of the targets picked up by Echo looked possible, we then still have to visually inspect them. We had some nice views of what Bob called "geology", a couple of sunken Japanese landing barges, one Japanese destroyer is serious disrepair from having both its bow and stern magazines set off by hitting US naval mines, and the PT-109. All that took time to lower the Argus camera sled and attach the "Little Herc" tethered ROV to it. Five hundred meters means about 600 meters of cable out, and you do not lower or retrieve it fast.
One other thing, the first sonars were pretty cheap to build and use. The recent ones will run around a $100 Million dollars or so to installed with the bow-mounted transducer and an very large amount of signal-processing gear, along with the sonar controls. Basically, the sonar started very cheap and very light, and rapidly got very large and very expensive. So the Tech Level Stage Effects chart really does not apply. The transducer with generate the sound waves have not changed that much at all, the big difference between the early sets and now is the switch from vacuum tubes to transistors and printed circuits, and the use of computers with screens. Essentially, Tech Levels 5, 6, and 7 cover the entire period.
