From: mikkelhaaheim@gmail.com   
      
   Le dimanche 24 juillet 2016 00:51:19 UTC+2, nu...@bid.nes a écrit :   
      
   >   I've been lurking this thread, and have noticed lots of unstated   
   assumptions by all participants.   
      
   Agreed. OTOH, I think it is hard to avoid that. I generally try to be as   
   precise as I can, but often I just don't have the time.    
      
   >    
   >   It might help to state exactly what we're trying to stealth, what we're   
   trying to stealth it *from*, and then we can start talking about the   
   characteristics of the environment that might help or hinder our stealthing   
   efforts *for that particular case*   
   .   
      
   Part of the problem, here, is that stealth is a fluid concept. There are no   
   absolutes. Strategists analyse the current situation, try to anticipate   
   advances, and then look for whatever they can to leverage the environment to   
   their favour.   
   My usual explanation is that stealth is less about not being seen than it is   
   about not being noticed. You take advantage of what you can. When conditions   
   change, stealth changes with it.   
      
      
      
      
   >    
   > > >You can't see through clouds like Superman's X-Ray vision    
   > >    
   > > You can with IR.   
   >    
   >   Yes, if it's available, and if there isn't a chemical fog in the way that   
   absorbs or diffuses IR beyond reliability or emits masking IR of its own.   
   Producing such "smokescreens" in space is far more difficult than in   
   atmosphere but certainly not    
   necessarily impossible or infeasible on the inherently massive economic scale   
   of interplanetary or interstellar warfare.   
      
   ...and there are always means to defeat the condition.   
      
      
   >    
   > > >  and scan the bottom of the sea .    
   > >    
   > > You have a point there. OTOH, stealth only works underwater because nations   
   > > still WANT it to work underwater. Sonar is extremely effective in water...   
   > > but it gives your position away.   
   >    
   >   Active sonar does, yes. Passive sonar doesn't which is a better analog of   
   the typical systems suggested for space warfare detection.   
      
   OTOH, there is often not enough signal for passive sonar. Scandinavian subs,   
   for example, are currently virtually undetectable using passive sonar. Also,   
   passive sonar tends to require a LOT of manoeuvering and time in order to get   
   a firing solution (a    
   3D fix), which makes it somewhat easier to detect you, even if you are not   
   going active.   
      
      
   >    
   > > This is not a problem, however, if the sound generators are deployed   
   > > throughout the oceans en mass... but EVERYONE will be able to hear the   
   > > reflections. Nothing in the oceans would ever by stealthy again.   
   >    
   >   Until the easily-located "illuminators" are destroyed, which will be a   
   priority for all sides.   
      
   Quite true... unless they are well defended. As I said, stealth works because   
   navies WANT stealth to work. If navies did NOT want stealth to work, they   
   would put up such a network, establish multiple levels of redundancy, and   
   establish strong defenses    
   for the transmitters. But this would be a significant investment, and...   
   navies WANT stealth to work.   
      
   >    
   >   Passive sonar imaging on small scales (arrays a few meters square, range a   
   few dozen meters, resolution a few centimeters) has been demonstrated in the   
   public domain. The "illumination" is ambient ocean noise.   
      
   I Don't doubt it. I have read a few Cog Sci papers about the blind   
   subconsciously using ambiant echolocation to navigate through rooms and busy   
   streetsides, and the naval applications of sch research are obvious. However,   
   if you want better range, you    
   will need reliable sources with fixed positions.   
      
   >    
   >   I have absolutely no doubt that all major military maritime players have   
   already deployed large networked passive arrays that can track pretty much any   
   object that might be a threat anywhere in Earth's oceans, if all were linked   
   together (eliminating    
   hiding behind seamounts, thermal layers, etc.). The hoary old SF cliche of   
   aliens having submarine bases is just flat-out impossible now, barring   
   collusion from the humans in charge of the part monitoring the alien base's   
   location.   
      
   I have no doubt that such arrays are much more extensive than anyone imagines;   
   however, we know from joint military excercises that such arrays do not exist   
   everywhere. The US is in the best position to establish such arrays, given its   
   wealth of natural    
   resources and its unequaled access to the oceans... and yet the US often is   
   unable to detect the opposition subs (notably scandinavian deisel subs that   
   can park themselves within yards from an aircraft carrier without being   
   noticed... after THAT    
   particular event, the US asked Sweden if we could borrow their sub to try to   
   work out how to detect it --this was about 3 or 4 years ago).   
      
   >    
   >   Using that information is a different matter in submarine warfare- the   
   collated, analyzed data has to be securely accessible by the subs. You can't   
   use comms lasers as you can with spacecraft.   
      
   Quite correct. ELF is the currently preferred option, but that takes a lot of   
   time. Sonic tranmission is an option, but you have to deal with the big bull's   
   eye you have painted.   
      
   >    
   >   Notice that if we used submarines for shipping rather than surface ships,   
   the commercial carriers would have had to develop this capacity if only for   
   traffic control.   
      
   Or establish tightly regulated traffic lanes, which is far more likely.   
      
   >    
   >   In space it's actually easier unless warships don't have to limit   
   themselves to things like Hohmann trajectories, but that's way beyond the   
   "current tech" goalpost that keeps being referred to.   
   >    
   >   If they do, the volume of space that must be kept under constant   
   *detailed* surveillance for planetary defense becomes much smaller. The same   
   applies to intership engagements within the Hill spheres of astronomical   
   bodies.   
   >    
      
   >    
   >   Our current air-tracking network coverage is driven mostly by commercial   
   limits; we install only the minimum required to keep the risks of losing track   
   of a plane to an insurance-acceptable minimum. Military expenditures for   
   similar tasks tend to be    
   more lavish because more is at stake.   
      
   ...and militaries don't think that such networks are worth the investment.   
   Every commercial plane that can go missing is a potential missile.   
      
      
      
   >   Losing an airliner or two per year is a few-dozen-millions-of-dollars risk   
   airline insurers accept.   
   >    
   >   Losing a *planet* even once is not an equally-acceptable risk, so space   
   warfare sensor capabilities will necessarily be much more elaborate than   
   anything so far discussed.   
      
      
   [continued in next message]   
      
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