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How would they check what's above them? Visual is out. Passive sonar will only detect noise sources. And pinging with active sonar loudly announces to everyone
by ethbr0 5y ago
How would they check what's above them? Visual is out. Passive sonar will only detect noise sources. And pinging with active sonar loudly announces to everyone around exactly where you are.
- toomuchtodo 5y agoMagnetic induction tomography. Detection at a distance isn't yet practical, but the physics are known (eddy current effect).
- kfarr 5y agoWhy is visual out? Cameras are cheap
- bayindirh 5y agoBut water is not always transparent or clear enough. Also there's not enough light all the time. Also pressure proofing cameras are not cheap I presume.
- ethbr0 5y agoYup. There's not much light below 100m. Certainly not down to 500m+. Which would also be 50atm+ worth of pressure.
- dylan604 5y agoAlso, nighttime
- paranoidrobot 5y agoThey have upward-looking cameras, at least on some of them. You can see it in the last Smarter Every Day video[1] where they're talking about surfacing a submarine in the arctic ocean. At several points you can see a video monitor showing an upward view of the ice. [1] https://youtu.be/XFJnWp1tAdU?t=1427 https://youtu.be/XFJnWp1tAdU?t=1427 e: to be clear, that upward looking camera isn't going to be enough to detect much beyond your own footprint. If someone is about to cross that area you'd need some other way of detecting them.
- jedc 5y agoThere’s special equipment/procedures for surfacing in the Arctic. That’s another really dangerous place to operate. (Default action in a submarine emergency is to get to the surface. That’s… NOT easy when there’s ice above you that’s potentially too thick to punch through)
- runsonrum 5y agoIsn't everything expensive for the military?
- tshaddox 5y agoIsn't it dark?
- digikata 5y agoA small tethered float with accelerometers that ascends along the path of the surfacing submarine.
- ethbr0 5y agoSubmarines typically conduct powered or semi-powered ascents. No forward motion = no steerage.
- digikata 5y agoAdd some steering and if needed power - if you’re lucky you only need to steer to the path with the energy of the vertical ascent.
- da_chicken 5y agoI think the point was that you have enough forward movement for steerage, your tethered float will always be behind you.
- digikata 5y agoThat's why I mentioned powering the float if needed ... I suppose it's more of a tethered drone at that point.
- speedybird 5y agoSurface ships are very noisy so submarines listen for other ships in the area before surfacing. They have dead zones in their sonar coverage, but can usually deal with that by turning to listen in those dead zones before surfacing. Nevertheless, there are occasional accidents.
- mpyne 5y agoSurface ships are not always noisy. This is especially a problem with supertankers if you they are head-on to you, they can be hard to hear from underwater, especially with the high level of noise from the surface around the supertanker. This was a contributing factor to a collision in the Mediterranean about a decade or so ago.
- jedc 5y agoI personally had what we called an “ass-puckering” moment for exactly this reason once. At periscope depth in fog, huge cargo ship coming at us… it was the only time in 3 years on board I (or anyone else) had to call “emergency deep”.
- dctoedt 5y ago> in fog, huge cargo ship coming at us And Iron Mike probably had the conn aboard the cargo ship .... (Source: A similar experience in the South China Sea.)
- baybal2 5y ago> And pinging with active sonar loudly announces to everyone around exactly where you are. From what I overheard in cafeterias frequented navy navy men while living in Vladivostok is that active sonar is used all the time unless deep blue waters. Navigational active sonars are nowhere near as detectable as long range military ones.
- mpyne 5y agoAny sonar useful enough to navigate at speed is going to give away your position. It's the "flashlight in the dark room" problem. Your sonar ping has to travel to an object and reflect back to the submarine. But an adversary just needs to hear the original ping to know what direction it came from, so you can be detected at a longer distance, and potentially a much longer distance, than you could reliably detect the other submarine at. That's not to say active sonar is never used, but at least with the U.S. it's not going to be continuously used, and it's going to be rare to use it if you're in a mission area. A sonar transducer that can emit a ping with directionality is sometimes useful (e.g. a fathometer to measure depth to the ocean bottom, since the crushing pressure of the depths ensures the area below you is generally clear of enemy subs), and those are used. But even there, that wouldn't be useful for navigating when otherwise blind; you use fathometers to confirm that you're approximately in the area you think you're in based on the chart readings.
- baybal2 5y ago> Any sonar useful enough to navigate at speed is going to give away your position. I mean the difference is possibly hundreds of metres to hundreds of kilometres in between navigational sonars, vs sub detection sonars.