• Content Count

  • Joined

  • Last visited

Community Reputation

1,371 Excellent


About K^2

  • Rank
    Particle Theory ABD

Recent Profile Visitors

The recent visitors block is disabled and is not being shown to other users.

  1. I'm just going to preemptively start working on an escape plan, because I know I'd be on the hit list. So add that to the whiteboard budget.
  2. You need something separate for storage, but MHD generator can generate power from solar wind. Solar panel will give you way more power, though.
  3. Sans reproduction, animal cells have inherently limited shelf life due to thermodynamics, chemistry, and background radiation (take your pick). Something is guaranteed to go wrong if you try to keep it up for astronomically significant times with overwhelming majority of neurons within the brain. Ability of neurons to be replaced is limited as is, but if you're going to have to recycle most if not all of them over the duration of the flight, keeping the brain in sleep is not an option. Without information updating as you replace neurons one by one, you'd be doing a hard wipe. And this is assuming you managed to get them to regenerate in the first place. So you could think to keep the brain in a slow dreaming state, allowing it to repair not just the cells, but also the information. And here we run into additional limitations of how the brain works, where we lose synapses over time as part of design. This is how we learn and how a lot of our memory works as well. If you allow that to keep happening, over astronomically significant time you'll end up with a senile old brain at destination at best, no matter how good your repair efforts are. And if you start repairing synapses, we're back to hard wipe scenario. This is why we have cryogenics as an idea. Keeping the brain at very nearly absolute zero would prevent any of these things from happening. Even effects of radiation will be limited. Albeit, you'll have to deal with accumulated radiation damage upon arrival somehow. Of course, all of the standard problems of cryogenics follow, not least of which are very strictly limited by thermodynamics. Alternatively, you could change how brain ages and repairs itself, as well as how it manages to hold on to information while retaining plasticity to learn new things. We'd have to do this if we want to attain anything like immortality, but we'd be literally redesigning human mind from ground up. Not only are we nowhere near even imagining where to start, but it also brings us into the depth of transhumanism of which it's very hard to even speculate. Unless we figure out FTL, people who will spread through the stars will not be human in any sense we think of it now. That's if we don't wipe ourselves out first.
  4. I've not! I was actually unaware of that sharp drop in the speed of sound at SLD. I fully expected density to vary, and I would anticipate significant lensing because of it. However, so long as the scales involved are much greater than distances between ships, the sound should still propagate just as if it departed from false source. Same deal with bottom bounces, so long as there is sufficient depth. SLD throws the wrench into this, however. It's at just the "wrong" kind of depth, which is comparable or less than distance between the emitters, to interfere with phase array approach. Intuitively, I'd expect this to still work, considering three cases. Sub is in surface duct, and won't get anything useful from its sonars anyways due to all the reflections. Sub is in the shadow zone, and doesn't get anything useful. Or sub has direct path, and should see the false sources without any problems. What could be wrecking it is if some of the emitters are in the shadow, allowing the sub to get a bearing on true sources. I can't possibly do this in my head or even on paper, though. I might need to write a simulation to actually test this. I've been meaning to play around with DX12 RT API, and this could be an interesting use case for it. I'll see what I can come up with. Thanks for pointing it out! I had no idea sharp temperature drop on top of steady density increase produces such an interesting speed of sound curve.
  5. A sonar system that only shows you false targets without showing you real ones seems properly disabled. But if you want to split hairs on terminology, I won't argue the point. Lets call it, "Creating decoys using hardware more commonly used for jamming." And the only limitations I'm setting is that subs don't talk to each other, and subs have a reason to rely on the sonar. You've provided me with the later in your previous two paragraphs, and I think we agree that subs communicating with each other would reveal them. So that's a real world scenario where this is useful. It might be that the sonar signature masking systems are good enough to where you wouldn't want to bother with this. I have no idea what the state of the art on these is. In that case, *shrug*. If there is no reason to jam, there is no reason to jam better. Can't argue with that.
  6. Again, I don't honestly care about the specifics. If you can communicate to the sub from pretty much anything above surface, our entire discussion of sonar is irrelevant. We either assume there's a reason why such communication is impossible (ECM, destruction of other assets, etc.) or we don't bother with jamming, decoys, or any other means of throwing torpedoes off course. A sub that can receive a signal from anywhere else will know exact relative location of all relevant targets in the modern world, and the torpedoes can engage on inertial alone until they are in magnetic range. There is no way to fight that with any form of countermeasures available to the fleet short of taking out the sub before it's in range. Which is why these are two separate discussions. If you insist that communication will always be possible, then countermeasures are useless, and sub will only use its sonar to look for other subs. If your position is that this is the only way it can be, then our discussion of jamming or anything else the fleet might do is meaningless. In order to talk about jamming strategies, we have to be talking in context of the sub relying on them, which precludes communication with outside sources. Again, if you think that's unrealistic, that's fine. But it's a separate discussion. Typically, when you have a body that's mostly spherical, but not quite, the sensible thing is to decompose the bits that aren't into spherical harmonics. J2 is one of the relevant terms. You can see a bit more discussion about it in this Wikipedia article, for example. Indeed, most of the numerical models used have been developed for Earth's satellites and ICBMs, so that's the context in which I've learned classical perturbation theory as well. But all of the physics is essentially the same when applied to objects comprising the rings. It's because of their choice of the coordinate system. You can see that they have a special term for drag in the Z direction. The reason for this is quite obvious if you picture this from perspective of an object passing through the rings. The amount of drag will be almost zero for an object passing through along the motion of the objects within. But any object moving perpendicular to the rings will experience significantly more drag. All orbital elements are taken with respect to some datum. The choice is somewhat arbitrary, but the moment you break the symmetry, some choices end up much more convenient than others. When dealing with a ring system, taking plane of the ring as part of your datum just makes sense. Unfortunately, that particular paper doesn't really make a distinction, because they essentially restrict the discussion to equatorial rings. The math, however, is exactly the same. So long as you chose Z axis, such that drag in that direction is significantly higher, the inclination will tend to zero in that particular frame of reference. In other words, inclination tends to zero with respect to plane motion in which provides least resistance. Id est, the plane of prevalent motion in that particular band. If you're still uncertain, the crucial bit here is that drag has nothing to do with orientation of the planet. We're talking about drag with respect to environment of the ring, which is governed by initial orbital plane of the debris. You can tilt planet's axis relative to that any which way, and it doesn't change the math. The only place where planet's orientation starts to play a role is in precession as per eqs 19, 20.
  7. Receiving what? We've already talked about it. If you have any source of information besides the subs in the area, you aren't even going to use your sonar to hunt surface targets. You have more reliable information, be it from surface ships' radars, aircraft, or satellite. Sonar is useless, and discussing jamming is pointless. If all you have to receive additional data from are other subs, I don't care if you want to insist that you can only receive on towed antenna, or suggest jury rigging the transmitters to send through it. The bottom line is that if you want to have subs share sonar data, you will give their presence away, regardless of which antenna you want to receive with and/or transmit with. Please, keep track of your own argument. If you want to drag radio into discussion, remember why you're doing it. Keeping in mind that majority of large moons are going to be in equatorial plane, making such rings far more likely. But yes, we could have ended up with a planet with inclined rings, and we didn't get any. As rare as they might be, some systems out there definitely have them. Also, I'd like to point out that the ring instability argument is absolute hogwash. Rings are very nearly circular, because anything in elliptical orbits will collide with each other. And the only effect on a circular orbit of the tidal forces from the planet is precession, which will be roughly uniform for the entire ring due to self-interaction of the objects comprising the ring (drag). So if you have multiple rings at different radii and inclinations, their relative orientation will change over time, but there is no force bringing rings to alignment with equator. Anyone who studied classical perturbation theory should know that. So again, there is absolutely nothing in orbital mechanics that would prevent stable inclined rings from remaining for a very long time once they are created. Even though initial formation of such rings is far less likely than these in equatorial plane. The second paper you've linked [this one] covers all of that. Specifically, the only non-periodic effect on inclination is dampening with respect to the plane of prevalent motion. (eq 13) In other words, inclination of particles tends to zero with respect to plane of the ring, not equator. Meaning the rings flatten, but remain otherwise stable in terms of inclination. The orientation of that plane drifts due to planet not being spherical. (eq 19, 20) This tells you that over time, the rings will precess around the planet. Note the R/a term, which tells you that different rings will precess at different rates. However, the damping forces discussed above, will keep each ring group intact. So even if you had just one plane in which rings were originally created, if they were spread over large enough distance, eventually they'll break down into multiple rings at different orientations, but common inclination angle. Could be quite an interesting sight.
  8. You are conflating several things again. Lets split them up neatly into two scenarios. First, sub can receive messages from outside world. These can include locations of ships in enemy fleet. If fleet ECM aren't sufficient to prevent these, that's it, that's the end of discussion. The sub flat out doesn't need to use its sonar to look for surface targets and can engage them completely blind using satellite data. Now, lets suppose that you are cut off from communications from the surface for whatever reason, and you have to rely on sonars of the subs to hunt the surface ships. Jamming strategy is in place. Can communication between subs be used to cut through jamming? In theory yes, but anything you can use sub-to-sub is too short ranged and low rate. You can use the towable antenna to get a much stronger, higher rate signal across, that should be sufficient to link several subs together. But that signal is omnidirectional. The moment you start using towable antenna to send the signal, it will light up every console of the enemy fleet with unidentified contacts. That is how towable antenna gives you away. This isn't a strict requirements. However, most of the moons of a gas giant are going to form from the protoplanetary disk. Because of that, they share an inclination. The rings are formed either from leftovers of the same protoplanetary disk, or due to destruction of the moons. Moons can be destroyed either through collision or by entering planet's Roche limit. In either case, most of the debris ends up in the same plane as the protoplanetary disk used to be in. Of course, moons can, and often enough do, end up orbiting in completely different plains. This can be due to captures or various gravitational interactions. In either case, if one of these moons becomes destroyed, it can form a ring matching inclination of its original orbit. This would then allow for multiple ring systems with different inclinations orbiting the same planet. I'm not aware of any examples, but there is no reason why it can't happen.
  9. Both. You want to jam passive and active sonar that may be employed by the sub or incoming torpedoes. The problem with jammers is that even if they can mask everything else, the source of jamming signal is too strong to hide in its own noise. You can always target source of such strong interference. The goal, therefore, is to present strong source points that don't correspond to physical locations of the ships. You get your all-masking noise, and anyone trying to target the source of the noise will hit nothing but empty space. (A dense grid can produce uniform, omnidirectional noise with nothing to target, but then your ocean surface is basically blanketed with ships, so that makes it kind of pointless. XD With discrete points, you have to have "hotspots" of noise, but they don't have to match locations of ships.) You might also be able to use it for your own detection. The pattern of the jamming noise is known to the source. You can actually use it as active sonar - in theory. I'd have to run numbers to see what the signal-to-noise is going to be like, and whether you can actually use it to look for subs while you're blinding them. Again, the advantage here is that you have a fleet that uses surface communication to network their jammers and sonars. But yeah, your ability to look for enemy subs is going to be greatly reduced at a minimum, and leaving you blind at the worst. Whether the advantages are worth it might depend on the situation. Can I guarantee detection within periscope range? *shrug* I'll have to run the numbers. That's definitely a good point. ELF won't be enough to break the above jamming strategy. You do actually need fairly high bitrate. The towable antenna would work, but it gives away subs. Not exact location, but presence for sure. I can see a group switching tactics the moment they spot multiple subs using surface communications. But yeah, if the sub is receiving anything from the surface, your game of hiding ships is basically up anyways. During cold war, when satellites had limited coverage, it was a different game. Today, any military that can hope to take on a supercarrier is going to know where every single one is at any given minute with sub-meter precision, and ELF has enough data rate to convey that for sure. Even though the sub can't get a GPS reading while submerged, the modern INS is precise enough to keep it within the sort of drift that will still let it put torpedoes within magnetic sensor range of a carrier without needing to see it. So unless you can prevent the sub from receiving data, decoys, jammers, and anything else you might try to throw off the sub is useless. If you allow it within torpedo range, you'll get hit. And here we'd have to talk about ECM and counter-ECM available, and I'd have to admit that I have no clue who has the edge. So... That definitely is a possibility. Jammers and decoys are still used. So it seems like there'd be some room for it. But they might be fallbacks for situations where everything else breaks down. With kinetic kill ICBMs, we might end up with no need for ship-hunting subs at all in the future. Any tactic, no matter how clever, can be superseded by another that just works better and is cheaper to implement.
  10. Not at all, that's the whole point. Yes, I do need very precise locations of the jammers relative to each other. That would require additional hardware on the relevant ships. I'd go with VHF/UHF interferometers for that. They have wavelength comparable to acoustic, which ought to make positioning juuust right. Variations in water density will "move" false targets around, but it's the same effect that it has on sub's acoustics. That is, if you have density changes in the water, the target can always appear at the slightly wrong bearing than it really is due to refraction. That effect will be unchanged. With all of that in mind, I don't need to know where the sub is. The acoustic wave produced by the jammers is almost exactly identical to the wave produced by a single emitter if it was at false source' location. That's how holography works. Again, I can write out the exact numerical decomposition of the target waveform into waveforms that have to be produced by individual jammers. This is just mathematics. This means that regardless of where the sub is located, the sound will appear to come from a location selected by the system. One that does not correspond to location of any ship in the group. Now, the grid is discrete, and there are only so many ships you can have the jammers running on. That does create limitations. There can be additional "shadows" showing up in random spots, appearing as additional sources of interference. These are almost guaranteed not to correspond to locations of real ships either, but they are hard to minimize without having a periodic grid of ships. Second problem is that viewed from different angles, the false source location might be slightly different. If you had an entire grid of subs in communication, they would be able to use this to filter out the false locations and resolve true sources of jamming. But that's fundamentally impossible for the subs without revealing their location. As I've mentioned before, if you had that sort of linking capability, just feed locations of ships to subs from the satellite. This method explicitly produces a false target for the sub regardless of where the sub is located and is mathematically impossible to resolve to true sources of jamming for a single sub.
  11. Latest incident puts question on Soyuz rocket, not the ship. Ship performed phenomenally, bringing the crew down safely despite failure happening at just about the worst possible moment. Granted, if the ruptured tank had actually blown, we could have had much sadder news, but like I said, it was a very bad timing for failure. All in all, safety of the ship is not questioned by ongoing investigation. Just that of the rocket. Given that, there is no reason not to send up MS-11 unmanned. Its a big expense and an even bigger financial risk if the rocket fails again, but leaving ISS unmanned is a greater risk. I think Roscosmos and NASA should bite the bullet and send MS-11 unmanned before MS-09 is due to return. If it makes it, jettison MS-09 and extend mission of the current crew. If it doesn't, have the crew come back down on 9, and take a risk with unoccupied ISS. It's not a great option, but it's the best one all around. The only other viable alternative is just to abandon ISS and hope it's still there when investigation concludes or Dragon and/or Starliner are ready for a manned mission. That's strictly worse than taking a chance with an unmanned launch right now. P.S. Strictly opinion.
  12. That's like saying, I need to know where the eyes are going to be located to produce holographic image in front of the screen, hovering where no physical object exists. Yet a hologram certainly works, I hope you're not going to deny it. A phased array produces a signal that matches any desired pattern of waves, including these that match perfectly with any non-existent source within the area spanned by array, to within error permitted by density of an array. A carrier group has sufficient density to fool a single sub, regardless of where it is locating, to perceive false sources only and be blind to true sources of interference. This is fairly heavy math on top of very basic wave physics, and this has been known for well over a hundred years. I'm telling you that I can reproduce the exact sound that would be coming from an object at desired location, projected in all directions, with nothing at that location. This is tried and tested tech. You are telling me it's not good enough, because you believe in some magical ability of the sonar to know that there is nothing there, despite the actual sound wave reaching it being absolutely identical. I have read it. I'm sorry if my response wasn't sufficiently clear. We're talking about two completely different scenarios here. 1) I want to mask the fleet, hiding it entirely. I employ noise-canceling with an active array. You want to cut through it. You're looking for very specific, repetitive sound of an engine, impeller, or any other periodic noise, really, that you can lock onto. Given a slow scan of the beam, you'll eventually succeed, no matter how good my noise-canceling is. This is what I mean when you're looking for specific target in otherwise quiet background. 2) I want to mask locations of individual ships within a group, without giving you anything concrete to lock onto, under assumptions that you already know where the group is overall. I deploy jammers instead of noise-canceling, and network them to produce patches of high intensity in areas where no ship is located. You do not have a pattern to lock onto, because noise is inherently non-periodic. Any known sources of sounds coming from ships are greatly overwhelmed by omnidirectional background of noise. And yes, even if you have a beam, you will pick up a lot of noise from all directions when jammers are used. I hope you at least know that much. The reason you can still normally lock onto a jammer is because the beam will generally cut back some of the noise from directions other than directly from jammer. So while being jammed, what a sonar sees is noise and patches of more noise. Hence use of an array of jammers to create false sources of high intensity. So as you scan your beam, you'll see noise everywhere, with patches of it, that you believe to be jammers, at some locations within the group. These, however, do not correspond to any physical target. At this point you've already exhausted ability to steer the beam and to filter the signal, and they produce absolutely nothing. Short of employing active sonar, you're not going to get anything useful in this scenario. You don't understand the things you are claiming are relevant. I'm sure you know the specs. But if you don't understand how a phased array produces a signal, what kind of signal it can produce, and how specifically any number of beams can be produced from a single array starting at any point within the array, then I'm sorry to say that you don't understand how the sonar works either. Because a modern sonar is a phased array attached to a dome and any number of additional resonators with lots of additional processing on top. I don't know the specs of the dome. I don't know the arrangement of pickups or their relevant resonances. I don't know the software suit that goes on top of it. But none of that changes how it works. Only the quality of the signal you get and how narrow a beam you could make. And I'm telling you that an ideal device, with perfect reception, and beam as tight as physical dimensions of the dome can possibly allow, is insufficient to cut through this. So yes, that makes any technical details of an actual physical sonar, which will perform worse than this idealized sonar, absolutely irrelevant. It can't perform better because math. And if it performs worse, my argument is only stronger. If you feel that's good enough reason for you to smugly dismiss the whole argument, I won't stop you.
  13. Yeah, and delay lines are precisely what allowed you to select a phase adjustment to signal received at each pickup, which lets you exclude everything but the beam you're interested in. It's like having a lens in front of the light detector, and rather than moving light detector, you change thickness of the lens to look in different directions. Interferometer telescopes work in exactly the same way, and they aren't classified. The advantage of working with sound or radio frequencies is that you can throw away the delay lines, record the signal with phase information intact, and then do any phase shifts you need in software. And that really gets us back to a phased array, with the difference that you need to correct for sonar dome shape, while giving you the signal strength of the full dome, rather than that of the array. I know you're probably read-in, so you can't talk about details regardless, but it's the kind of secret that isn't. At least, in broad strokes. I'm sure there are plenty of reasons to keep the details classified. I see where you're going with this, but still no. If you tune this to a bearing of a true source, you won't get any signal that's distinct from background noise, because you'll be getting noise from all the other sources hitting your pickups at just the right timings to travel down these delay lines and cancel out the actual signal from the source you're staring at. I could probably come up with a way to punch through this if we were looking for something very specific, like engine noise, while several sources produce fake engine noise, trying to project it to a false location. Alternatively, if there were at least a few subs that shared their raw acoustics data in real time, you could probably resolve true sources. But if we're staring at a bunch of jammers, your signal processing is already busy filtering out the noise, so you can try and locate sources of jamming signal. So the only place where the sonar's going to give you a signal that's distinct from background noise is if your beam is pointing at the false source. Looking at a true source will give you the same kind of noise as pointing in any other direction.
  14. It will not. If you learn the physics of how it "looks" in a specific direction, you will know that it picks up the waves coming down from all directions, but only ones that come from specific bearing interfere constructively, producing signal only from that direction. This is true if your sources are not coherent, which is the case for any natural source or uncoordinated jammers. If you have multiple synchronized, coherent sources, this no longer works. And I can produce a false source at a bearing I chose relative to your passive sonar, at location where no real source exists. Again, wave optics. My background is ten years of quantum physics. That is explicitly physics and mathematics behind wave propagation. I don't know exact engineering that goes into acoustic pickups on a sub, because I'm not a naval engineer. I certainly don't know anything about operation procedures. But I don't need to. I know how to construct an incoming sound wave that is indistinguishable from the wave reaching the sonar from a specified direction where no real source is located. And if the incoming waveform is identical there are no means to distinguish the source. You cannot get information that's not there, no matter how sophisticated the hardware. It's not magic, after all. I can write out the equations, including a mathematical model of a perfect passive sonar, that has ability to select sources by bearing. And I can show that even this perfect, ideal, mathematically precise sonar will be fooled, let alone any actual physical implementation that will do worse. I just don't know if it makes any sense for me to write out equations that are going to involve Fourier transforms and convolutions, or if it's going to bounce right off.
  15. A phased array produces a hologram. It's omnidirectional. Just because typical usage is steerable beam, you shouldn't think that's the only thing you can do with it. And while angular resolution depends on how many grid points you have, a carrier group has enough coverage to create false source(s) of interference that do not correspond to locations of real ships. It's fairly straight forward to decompose the desired "image" seen from perspective of any sub into individual sources. If you don't understand how that works, I strongly encourage you to learn a bit of wave optics before you continue arguing the point. Especially, if you plan to start with "Um, no." The objective isn't to mask your fleet from passive acoustics, so discussion of how involved it is is meaningless. We're talking about jamming. Throwing so much acoustic interference, that passive or active sonar are absolutely useless. You can have a human or a computer listening, and they'll get bugger all useful with absolutely any jamming method. Nor are we trying to hide a general location of a carrier group. If your navy doesn't know where enemy's carriers are at all times, you've already lost this war. The only downside of jamming is giving away location of the jamming source, making the jammer itself an easy target. An array of jammers can produce false sources preventing this from happening without the enemy sub getting close enough to be immediately detected and engaged. If torpedo aimed at a source of interference passes close enough to actual jammer ship by chance, yes, it will be able to hit it. If it doesn't, it will try to chase the false signal and most likely not hit anything. Alternatively, you can engage active sonar on torpedo early, and hope to pass close enough to something for jamming to not matter. Then you'll hit a random ship, but you give advanced warning to the fleet to use countermeasures. To summarize, without jammers, sub can target specific ship, such as the carrier proper, on passives, and have torpedo engage active sonar when it's too late for target to engage countermeasures. With uncoordinated jammers, each jammer makes an excellent target and can be picked out one by one. With networked jammers, you lob a torpedo, and hope that it passes close enough to something to target it, which will be a random ship in the fleet. Does it provide perfect protection? No. It's a carrier group, and some of the ships are basically there to take hits, because a target that big and that important is not going to be hidden in the modern world. You job is to make hunter sub's job as tough as possible, to give your hunters an advantage, or to force enemy sub to reveal itself early. Networked jamming can potentially achieve all three, while not tying your hands on employing pretty much every other method as well, including decoys. It is a pure advantage over not doing this.