8 ms·

After reading the article, it’s fun to just sort of riff from first principles to guess where things are headed. I think there are two types of hiding: silence

After reading the article, it’s fun to just sort of riff from first principles to guess where things are headed. I think there are two types of hiding: silence and camouflage. Silence is where you reduce the signal you emit and reflect. Camouflage is where you mask it with something else. Hiding a gold bar in a basement is camouflage (by this definition). Making your sub reflect sonar to look like a whale is camouflage. Making your sub reflect nothing is silence. Long term, I think silence is a losing strategy for the hider. You can hide with silence in the ocean because it’s so big. But as sensors become more sensitive, the ocean gets “smaller”. I think you run into basic physical limitations on silence well before you do on detection. Like the article suggested, I think the days of quieter propulsion and better propulsion detection being a big part of the game are numbered. I can see camouflage going on longer. Seems like the second stage of the game. What happens when you have 10,000 vehicles emitting all sorts of signatures you can’t disambiguate, and 50 of those are nuclear subs? Or worse, a million objects including civilian UUVs and marine life? That’s essentially the same as non-identification. It’s like using facial identification against a military to find the general, but everyone can change their face at will.

MrSkelter 2y ago
Americas obsession with nuclear propulsion is a large part of the problem. You can’t switch a nuclear power plant off. It’s always making noise and vibrating. These these subs are always noisier than electric units which can be totally off and totally silent, emitting nothing. It’s politics that demands the glamour of a huge nuclear fleet. For stealth nuclear power which makes noise constantly and is nuts radiation is an inferior choice.
adolph 2y ago
> Long term, I think silence is a losing strategy for the hider. You can hide with silence in the ocean because it’s so big. This would also apply to low observability strategies for the atmosphere, no? Perhaps lower observable atmospheric vehicles in general, autonomous or not, would mitigate mass freak-outs like NJ.
- HPsquared 2y ago
  The sky has a very dark background though when it's clear out and you're looking up. Whereas the ocean is more "messy" and noisy.
taneq 2y ago
Reflecting nothing can be as bad as reflecting a big bright 'ping'. Once you get to a certain level of stealth you have to essentially camouflage against an 'empty' background or you become a conspicuous absence. Edit: I'm thinking more about visual camouflage here, though - maybe for sound underwater there's no point at which being quieter becomes a liability?
late2part 2y ago
Pretending to be a whale doesn't seem like a sound principle to me. Subs don't follow the migratory paths of whales, as far as I know. Now, we just look for whales that are out of place and send a drone out to check. Maybe you're right though, that overwhelming the signal pattern, similar to how SDI/Star Wars was deemed moot.
- magicalhippo 2y ago
  Reminds me of that old joke about then-modern stealth fighters having the radar cross section of a bird, with a reply stating that if they saw a bird going at mach 0.8 they'd fire some missiles at it.
  - ben_w 2y ago
    I have a vague memory that nobody knew how high some birds flew until military radar got good enough to see them. They sent up an interceptor aircraft to check out what was flying up there, rather than missiles. https://en.wikipedia.org/wiki/List_of_birds_by_flight_heights https://en.wikipedia.org/wiki/List_of_birds_by_flight_height...
taeric 2y ago
This feels off, though. We may be at the point where it is hard to keep any particular thing quiet, sure. But we are also at the point where it is rather easy to park a ton of things around that are very easy to keep quiet until we want a lot of noise. That is, if you are going to first principals, I have to ask why you don't have a ton of unmanned drones down there. Literally remove the need to move somewhere for the people on board.
- lazide 2y ago
  Communicating with the drones is nearly impossible.
  - taeric 2y ago
    Missed this thread, apologies. I would take "nearly impossible" to be akin to "very expensive." Which is not to say that any of the difficulties just flat go away. But you don't necessarily need long range communication. I now realize the other thread is taking my point to be that this is trivially doable. That was also not my intent. My point was simply that "reducing to first principals" is a bit silly if you are going to maintain the requirement that you have a big enough vehicle to sustain a crew. Even a minimal crew imposes some massive design constraints that you don't necessarily have if you reduce the problem down. (In general, oddly, I meant my comment mostly as a criticism of "first principals" thinking on this. Too many of those analyses bring in base assumptions that are often invisible to the people arm chairing it.)
    - travisjungroth 2y ago
      > Missed this thread, apologies. I would take "nearly impossible" to be akin to "very expensive." I’m certainly no expert, but I don’t think that’s the case here. Radio waves don’t penetrate water that far. Communicating with an untethered vehicle deep underwater is impossible. At the surface, trivial.
      - taeric 2y ago
rokhayakebe 2y ago
Why not have thousands of sea drones that send fake signals.
simonsarris 2y ago
> But as sensors become more sensitive, the ocean gets “smaller”. is it not still possible to have 1 submarine and 9000 really annoying "noisemakers"? Smoke is a kind of camouflage. A constant smokescreen of sonar waves probably won't be fun for the whales...
- pfdietz 2y ago
  The more sensitive detectors are, the more subject they are to spoofing, I'd think, since less noise is needed to look real.
- michaelmrose 2y ago
  If they are especially noisy wouldn't that make them incredibly easy to track identify and then disregard in addition to being so expensive that your country can't even afford to have healthcare?
- Terr_ 2y ago
  There's another sub-distinction (hah) I'd like to make: Smoke versus decoys. So instead of 9000 devices to blanket the area with noise so that the movements of the real submarine are hard to discern, you could have 90 decoys which are localized, and the real sub is "hiding in plain sight." In other words, the difference between obscuring "where" versus "which one."
willvarfar 2y ago
How much of the detection is detecting the affect a large object moving (or holding a stationary position in a current) has on water (displacing it, wake etc) vs the object itself? This is like spotting soldiers wearing camouflage by following their muddy footprints?
ben_w 2y ago
If I had to guess, it would be gravity sensors that render submarines obsolete. Can't hide mass.
- Retric 2y ago
  Subs float in the water column by having the same mass as the water they displace.
  - variadix 2y ago
    The same density _overall_ but locally the density varies. Maybe there’s some way to use this for detection but I don’t see it.
    - deleted 2y ago
      [deleted]
    - ben_w 2y ago
      Aye. Dipole and similar gross asymmetries. I don't know about all the potential noise sources and how well any of them could be compensated for, but the raw sensory capacity of the best systems is at least enough to be worth considering the question.
- nickff 2y ago
  Submarines have roughly neutral buoyancy when submerged; how will you detect the mass?
- connicpu 2y ago
  When a sub is submerged, by definition it is buoyant and therefore has the same average density as the surrounding water. Unless your gravity sensor is so sensitive it can detect the different densities on a per-cubic meter basis (or smaller).
- dingnuts 2y ago
  just convert it from space and into time, duh. can't weigh time
danielmarkbruce 2y ago
Except, having 1000 subs in Chinese waters (just as an example) doesn't help you. The point isn't just to evade being blown up, or which is the sub with weapons, it's also to evade detecting you were ever there or are there.
- ethbr1 2y ago
  Of submarine missions, only one of them (special operations support) requires complete secrecy. Subs with SLB/CMs or attack subs are perfectly fine with being known-in-AO but untargetable. Which mirrors air, where MALDs/EW are a critical part of any mission in hostile airspace.
  - danielmarkbruce 2y ago
    Yup, agree: > The point isn't just to evade being blown up Should have read "The point isn't always..."
AtlasBarfed 2y ago
Yes I think decoy drones will be critical to extending the useful lifespan of submarines, and perimeter drone defense critical to deep water. But I think the Ukraine war has shown that shallow water navies are totally vulnerable to drones. So the purported numerical advantage of the current Chinese navy is basically worthless. If course it is debatable if our deep water Navy can withstand missile guidance tech from the 1970s.

MrSkelter 2y ago

Americas obsession with nuclear propulsion is a large part of the problem. You can’t switch a nuclear power plant off. It’s always making noise and vibrating. These these subs are always noisier than electric units which can be totally off and totally silent, emitting nothing. It’s politics that demands the glamour of a huge nuclear fleet. For stealth nuclear power which makes noise constantly and is nuts radiation is an inferior choice.

adolph 2y ago

> Long term, I think silence is a losing strategy for the hider. You can hide with silence in the ocean because it’s so big. This would also apply to low observability strategies for the atmosphere, no? Perhaps lower observable atmospheric vehicles in general, autonomous or not, would mitigate mass freak-outs like NJ.

HPsquared 2y ago
The sky has a very dark background though when it's clear out and you're looking up. Whereas the ocean is more "messy" and noisy.

taneq 2y ago

Reflecting nothing can be as bad as reflecting a big bright 'ping'. Once you get to a certain level of stealth you have to essentially camouflage against an 'empty' background or you become a conspicuous absence. Edit: I'm thinking more about visual camouflage here, though - maybe for sound underwater there's no point at which being quieter becomes a liability?

late2part 2y ago

Pretending to be a whale doesn't seem like a sound principle to me. Subs don't follow the migratory paths of whales, as far as I know. Now, we just look for whales that are out of place and send a drone out to check. Maybe you're right though, that overwhelming the signal pattern, similar to how SDI/Star Wars was deemed moot.

magicalhippo 2y ago
Reminds me of that old joke about then-modern stealth fighters having the radar cross section of a bird, with a reply stating that if they saw a bird going at mach 0.8 they'd fire some missiles at it.
- ben_w 2y ago
  I have a vague memory that nobody knew how high some birds flew until military radar got good enough to see them. They sent up an interceptor aircraft to check out what was flying up there, rather than missiles. https://en.wikipedia.org/wiki/List_of_birds_by_flight_heights https://en.wikipedia.org/wiki/List_of_birds_by_flight_height...

taeric 2y ago

This feels off, though. We may be at the point where it is hard to keep any particular thing quiet, sure. But we are also at the point where it is rather easy to park a ton of things around that are very easy to keep quiet until we want a lot of noise. That is, if you are going to first principals, I have to ask why you don't have a ton of unmanned drones down there. Literally remove the need to move somewhere for the people on board.

lazide 2y ago
Communicating with the drones is nearly impossible.
- taeric 2y ago
  Missed this thread, apologies. I would take "nearly impossible" to be akin to "very expensive." Which is not to say that any of the difficulties just flat go away. But you don't necessarily need long range communication. I now realize the other thread is taking my point to be that this is trivially doable. That was also not my intent. My point was simply that "reducing to first principals" is a bit silly if you are going to maintain the requirement that you have a big enough vehicle to sustain a crew. Even a minimal crew imposes some massive design constraints that you don't necessarily have if you reduce the problem down. (In general, oddly, I meant my comment mostly as a criticism of "first principals" thinking on this. Too many of those analyses bring in base assumptions that are often invisible to the people arm chairing it.)
  - travisjungroth 2y ago
    > Missed this thread, apologies. I would take "nearly impossible" to be akin to "very expensive." I’m certainly no expert, but I don’t think that’s the case here. Radio waves don’t penetrate water that far. Communicating with an untethered vehicle deep underwater is impossible. At the surface, trivial.
    - taeric 2y ago

rokhayakebe 2y ago

Why not have thousands of sea drones that send fake signals.

simonsarris 2y ago

> But as sensors become more sensitive, the ocean gets “smaller”. is it not still possible to have 1 submarine and 9000 really annoying "noisemakers"? Smoke is a kind of camouflage. A constant smokescreen of sonar waves probably won't be fun for the whales...

pfdietz 2y ago
The more sensitive detectors are, the more subject they are to spoofing, I'd think, since less noise is needed to look real.
michaelmrose 2y ago
If they are especially noisy wouldn't that make them incredibly easy to track identify and then disregard in addition to being so expensive that your country can't even afford to have healthcare?
Terr_ 2y ago
There's another sub-distinction (hah) I'd like to make: Smoke versus decoys. So instead of 9000 devices to blanket the area with noise so that the movements of the real submarine are hard to discern, you could have 90 decoys which are localized, and the real sub is "hiding in plain sight." In other words, the difference between obscuring "where" versus "which one."

willvarfar 2y ago

How much of the detection is detecting the affect a large object moving (or holding a stationary position in a current) has on water (displacing it, wake etc) vs the object itself? This is like spotting soldiers wearing camouflage by following their muddy footprints?

ben_w 2y ago

If I had to guess, it would be gravity sensors that render submarines obsolete. Can't hide mass.

Retric 2y ago
Subs float in the water column by having the same mass as the water they displace.
- variadix 2y ago
  The same density _overall_ but locally the density varies. Maybe there’s some way to use this for detection but I don’t see it.
  - deleted 2y ago
    [deleted]
  - ben_w 2y ago
    Aye. Dipole and similar gross asymmetries. I don't know about all the potential noise sources and how well any of them could be compensated for, but the raw sensory capacity of the best systems is at least enough to be worth considering the question.
nickff 2y ago
Submarines have roughly neutral buoyancy when submerged; how will you detect the mass?
connicpu 2y ago
When a sub is submerged, by definition it is buoyant and therefore has the same average density as the surrounding water. Unless your gravity sensor is so sensitive it can detect the different densities on a per-cubic meter basis (or smaller).
dingnuts 2y ago
just convert it from space and into time, duh. can't weigh time

danielmarkbruce 2y ago

Except, having 1000 subs in Chinese waters (just as an example) doesn't help you. The point isn't just to evade being blown up, or which is the sub with weapons, it's also to evade detecting you were ever there or are there.

ethbr1 2y ago
Of submarine missions, only one of them (special operations support) requires complete secrecy. Subs with SLB/CMs or attack subs are perfectly fine with being known-in-AO but untargetable. Which mirrors air, where MALDs/EW are a critical part of any mission in hostile airspace.
- danielmarkbruce 2y ago
  Yup, agree: > The point isn't just to evade being blown up Should have read "The point isn't always..."

AtlasBarfed 2y ago

Yes I think decoy drones will be critical to extending the useful lifespan of submarines, and perimeter drone defense critical to deep water. But I think the Ukraine war has shown that shallow water navies are totally vulnerable to drones. So the purported numerical advantage of the current Chinese navy is basically worthless. If course it is debatable if our deep water Navy can withstand missile guidance tech from the 1970s.