4 ms·

Are they really not detectable from space?

by uga4012 5y ago

jaywalk 5y ago
Why do you think they would be detectable from space? That doesn't make any sense.
- chinathrow 5y ago
  Why do you think that no nation states and their 3 letter agiens might have developed such technology by now? We basically know nothing about what current NRO spy sats carry, or do we?
- changoplatanero 5y ago
  There is a technique for finding nuclear submarines from space by using satellites to look for the hot water exhaust from the nuclear reactors.
  - NovemberWhiskey 5y ago
    Let me get this straight - there's a technique for detecting changes in the surface temperature of the water from a submarine that's probably hundreds of meters below the surface?
    - willvarfar 5y ago
      Yes. There are also magnetic anomaly detectors (MAD) and various wake detection approaches. Do these work all always? Probably not. But they work often enough to be researched and used. https://m.youtube.com/channel/UC9bMgCQyFNaMPsK9GtzM5dQ https://m.youtube.com/channel/UC9bMgCQyFNaMPsK9GtzM5dQ is a good starting point.
      - NovemberWhiskey 5y ago
        That's an entire YouTube channel. Where in this mess of videos can I find a reference to thermal detection of submerged submarines, please?
  - hindsightbias 5y ago
    Closed cycle steam generation plants aren't going to exhaust much. They can't filter seawater fast enough for use and you couldn't run seawater through those systems w/o messing them up. Wastewater is probably cooled before release.
    - cryptonector 5y ago
      Subs must necessarily produce heat. That heat has to go into the surrounding (usually very cold) water. This is unavoidable. Those nuclear reactors are cooled with that surrounding water, though obviously through heat exchangers.
    - postalrat 5y ago
      Wouldn't cooling something with water warm up the water?
      - hindsightbias 5y ago
        If it sat still for hours and a shallow depth, thermodynamics is thermodynamics. Very different from the idea of passing tons of seawater through a reactor and dumping it out. It's not like a jet engine flying through the sky.
- cryptonector 5y ago
  These subs are large, metallic, full of electric equipment, and heavy. They have magnetic and gravitational effects on their surroundings. They also have electromagnets to help hide their magnetic signatures. A network of very sensitive satelites with very precise clocks could be used to detect gravitational anomalies -- maybe, I'm not sure what kind of precision would be needed, or if that is achievable.
  - kragen 5y ago
    They're the same density as the water they're floating in, even though they contain some metal that is much denser.
detritus 5y ago
Using what technology? I can imagine in some future there being the means, but I find it hard to believe we have that level of tech available to the sort of packages we can aloft into orbit now.
dmos62 5y ago
They're hardly detectable from Earth.
SonicScrub 5y ago
Any detection from space would have to use an optics system to detect light bouncing off the submarine. This light could be either the naturally occurring visible light, or some form of active system (probably emitting radar waves). Unfortunately light can't penetrate very far into water, so this idea is a non-starter. Light can barely make it 200m into the ocean (meaning 100m depth for light to make a round-trip and back for detection), and subs can go as deep as 300m. Any satellite-based detection system would have to rely on catching the sub while on the surface. I'm positive this is being attempted constantly, but catching a sub at depth is an entirely different manner.
TeMPOraL 5y ago
Let's hope not - that submarines carrying nuclear weapons are undetectable is the only thing that's keeping the major powers from going to war.
jazzyjackson 5y ago
next time you're out on the open ocean check how far down into the water you can see, and then check out this graph [0] of electromagnetic radiation absorption of water: visible light is the best case scenario. there's a reason sonar is acoustic and not light based [0] http://hyperphysics.phy-astr.gsu.edu/hbase/Chemical/watabs.html http://hyperphysics.phy-astr.gsu.edu/hbase/Chemical/watabs.h...
sca4 5y ago
Lot of dismissive reactions to these questions, but there actually are non sound related signals we use to detect submarines and there is absolutely research on how to do that from space. This article is great, but just read the "Signal Processing" section if you're interested in space. https://www.aspistrategist.org.au/prospects-for-game-changers-in-submarine-detection-technology/ https://www.aspistrategist.org.au/prospects-for-game-changer...
- bambax 5y ago
  Interesting article. Also, we are now able to reconstruct a conversation by analyzing the movement of the glass on a window to the room where people are talking. It doesn't seem absolutely out of reach that we could some day detect huge underwater vessels from analyzing surface perturbations.
  - traeregan 5y ago
    > reconstruct a conversation by analyzing the movement of the glass on a window to the room where people are talking May I please have a link to more information? I wasn't able to find anything, and this is very interesting.
    - puglr 5y ago
      "reconstruct conversation glass vibration" brings up a lot of relevant results from a 2014 story from MIT. Sounds like it works in principle with any medium that can have its visible vibrations monitored (bag of chips is the main example, but they talk about other options such as plants or a glass of water).
      - bambax 5y ago
        Yes I think that's what I was referring to; I may have confused glass and chips but it seems it works with either medium. https://news.mit.edu/2014/algorithm-recovers-speech-from-vibrations-0804 https://news.mit.edu/2014/algorithm-recovers-speech-from-vib...
nradov 5y ago
The US Navy has researched the possibility of detecting shallow submarines from space since at least the 1990s by looking for subtle wake turbulence on the surface. The results are classified so we don't know if they were ever successful. It's not completely impossible, but the signal to noise ratio would be extremely low.
skinkestek 5y ago
I won't say modern submarines can or cannot be detected from space, but this should give you some ideas about what is publicly known: https://duckduckgo.com/?q=spotting%20submarines%20using%20magnetic%20fields%20&t=fpas https://duckduckgo.com/?q=spotting%20submarines%20using%20ma... This is fairly open secrets to the degree that it is secret at all so it probably also is no big secret that passive and active countermeasures are used to prevent these techniques.
cryptonector 5y ago
That's not a bad question. Subs would be detectable using magnetometers, except that they have electromagnets in them to hide their magnetometer footprint. Still, this is not perfect. Large subs have somewhat detectable gravitometric footprints that could be observed from space, indeed.
lnwlebjel 5y ago
Not sure if they are, but I do know that the US Navy funded a lot of oceanographic research into predicting and understanding bioluminescence of marine organisms for this very reason. The surface waters of the North Atlantic have massive spring blooms of phytoplankton, which are sometimes bioluminescent, and could certainly give away the presence of a large subsurface vessel, possibly from space.

Are they really not detectable from space?

jaywalk 5y ago

Why do you think they would be detectable from space? That doesn't make any sense.

chinathrow 5y ago
Why do you think that no nation states and their 3 letter agiens might have developed such technology by now? We basically know nothing about what current NRO spy sats carry, or do we?
changoplatanero 5y ago
There is a technique for finding nuclear submarines from space by using satellites to look for the hot water exhaust from the nuclear reactors.
- NovemberWhiskey 5y ago
  Let me get this straight - there's a technique for detecting changes in the surface temperature of the water from a submarine that's probably hundreds of meters below the surface?
  - willvarfar 5y ago
    Yes. There are also magnetic anomaly detectors (MAD) and various wake detection approaches. Do these work all always? Probably not. But they work often enough to be researched and used. https://m.youtube.com/channel/UC9bMgCQyFNaMPsK9GtzM5dQ https://m.youtube.com/channel/UC9bMgCQyFNaMPsK9GtzM5dQ is a good starting point.
    - NovemberWhiskey 5y ago
      That's an entire YouTube channel. Where in this mess of videos can I find a reference to thermal detection of submerged submarines, please?
- hindsightbias 5y ago
  Closed cycle steam generation plants aren't going to exhaust much. They can't filter seawater fast enough for use and you couldn't run seawater through those systems w/o messing them up. Wastewater is probably cooled before release.
  - cryptonector 5y ago
    Subs must necessarily produce heat. That heat has to go into the surrounding (usually very cold) water. This is unavoidable. Those nuclear reactors are cooled with that surrounding water, though obviously through heat exchangers.
  - postalrat 5y ago
    Wouldn't cooling something with water warm up the water?
    - hindsightbias 5y ago
      If it sat still for hours and a shallow depth, thermodynamics is thermodynamics. Very different from the idea of passing tons of seawater through a reactor and dumping it out. It's not like a jet engine flying through the sky.
cryptonector 5y ago
These subs are large, metallic, full of electric equipment, and heavy. They have magnetic and gravitational effects on their surroundings. They also have electromagnets to help hide their magnetic signatures. A network of very sensitive satelites with very precise clocks could be used to detect gravitational anomalies -- maybe, I'm not sure what kind of precision would be needed, or if that is achievable.
- kragen 5y ago
  They're the same density as the water they're floating in, even though they contain some metal that is much denser.

detritus 5y ago

Using what technology? I can imagine in some future there being the means, but I find it hard to believe we have that level of tech available to the sort of packages we can aloft into orbit now.

dmos62 5y ago

They're hardly detectable from Earth.

SonicScrub 5y ago

Any detection from space would have to use an optics system to detect light bouncing off the submarine. This light could be either the naturally occurring visible light, or some form of active system (probably emitting radar waves). Unfortunately light can't penetrate very far into water, so this idea is a non-starter. Light can barely make it 200m into the ocean (meaning 100m depth for light to make a round-trip and back for detection), and subs can go as deep as 300m. Any satellite-based detection system would have to rely on catching the sub while on the surface. I'm positive this is being attempted constantly, but catching a sub at depth is an entirely different manner.

TeMPOraL 5y ago

Let's hope not - that submarines carrying nuclear weapons are undetectable is the only thing that's keeping the major powers from going to war.

jazzyjackson 5y ago

next time you're out on the open ocean check how far down into the water you can see, and then check out this graph [0] of electromagnetic radiation absorption of water: visible light is the best case scenario. there's a reason sonar is acoustic and not light based [0] http://hyperphysics.phy-astr.gsu.edu/hbase/Chemical/watabs.html http://hyperphysics.phy-astr.gsu.edu/hbase/Chemical/watabs.h...

sca4 5y ago

Lot of dismissive reactions to these questions, but there actually are non sound related signals we use to detect submarines and there is absolutely research on how to do that from space. This article is great, but just read the "Signal Processing" section if you're interested in space. https://www.aspistrategist.org.au/prospects-for-game-changers-in-submarine-detection-technology/ https://www.aspistrategist.org.au/prospects-for-game-changer...

bambax 5y ago
Interesting article. Also, we are now able to reconstruct a conversation by analyzing the movement of the glass on a window to the room where people are talking. It doesn't seem absolutely out of reach that we could some day detect huge underwater vessels from analyzing surface perturbations.
- traeregan 5y ago
  > reconstruct a conversation by analyzing the movement of the glass on a window to the room where people are talking May I please have a link to more information? I wasn't able to find anything, and this is very interesting.
  - puglr 5y ago
    "reconstruct conversation glass vibration" brings up a lot of relevant results from a 2014 story from MIT. Sounds like it works in principle with any medium that can have its visible vibrations monitored (bag of chips is the main example, but they talk about other options such as plants or a glass of water).
    - bambax 5y ago
      Yes I think that's what I was referring to; I may have confused glass and chips but it seems it works with either medium. https://news.mit.edu/2014/algorithm-recovers-speech-from-vibrations-0804 https://news.mit.edu/2014/algorithm-recovers-speech-from-vib...

nradov 5y ago

The US Navy has researched the possibility of detecting shallow submarines from space since at least the 1990s by looking for subtle wake turbulence on the surface. The results are classified so we don't know if they were ever successful. It's not completely impossible, but the signal to noise ratio would be extremely low.

skinkestek 5y ago

I won't say modern submarines can or cannot be detected from space, but this should give you some ideas about what is publicly known: https://duckduckgo.com/?q=spotting%20submarines%20using%20magnetic%20fields%20&t=fpas https://duckduckgo.com/?q=spotting%20submarines%20using%20ma... This is fairly open secrets to the degree that it is secret at all so it probably also is no big secret that passive and active countermeasures are used to prevent these techniques.

cryptonector 5y ago

That's not a bad question. Subs would be detectable using magnetometers, except that they have electromagnets in them to hide their magnetometer footprint. Still, this is not perfect. Large subs have somewhat detectable gravitometric footprints that could be observed from space, indeed.

lnwlebjel 5y ago

Not sure if they are, but I do know that the US Navy funded a lot of oceanographic research into predicting and understanding bioluminescence of marine organisms for this very reason. The surface waters of the North Atlantic have massive spring blooms of phytoplankton, which are sometimes bioluminescent, and could certainly give away the presence of a large subsurface vessel, possibly from space.