From: chakatfirepaw@gmail.com   
      
   On Fri, 21 Oct 2016 10:23:01 -0700, Mikkel Haaheim wrote:   
      
   > Le lundi 26 septembre 2016 01:19:13 UTC+2, Rick Pikul/Chakat Firepaw a   
   > écrit :   
   >   
   >> >> Nope, not false.  Your later simply shows that you still don't   
   >> >> understand how a sensor system like this would work.   
   >> >>   
   >> >> (Hint:  Think about why radar dishes move and why they can get away   
   >> >> with not constantly staring at things.)   
   >> >   
   >> > Nope, still false. You can get away with terrestrial radar scanning   
   >> > because the gaps created during military radar sweeps are generally   
   >> > not large enough to slip aircraft through, at least not at the ranges   
   >> > where you have reliable detection.   
   >>   
   >> And the gaps in an interplanetary sensors sweeps are not large enough   
   >> for ships to slip through.   
   >   
   > There are quite a few different kinds of "gaps" that stealth can take   
   > advantage of.   
      
   Given that we were talking about directional observation gaps....   
      
   > A sensor platform requires accumulation of RELIABLE signal   
   > input. Platforms acquire input through signal source strength, detector   
   > sensitivity, spatial signal accumulation (collector area), and temporal   
   > signal accumulation (exposure time). RELIABILITY is established through   
   > detection amplitude, signal duration and/or repetition, signal contrast,   
   > multiple detection sites, etc. It is NOT enough to simply detect a   
   > signal. You must also rule out false positives  (energy discharges   
   > produced by the sensor equipment, localised discharge events, routine   
   > deviations in known sources --you can't just eliminate a signal as a   
   > known target, because intensities of background sources tend to vary   
   > naturally as a product of physical activity in the deep space   
   > environment, so you end up throughing out legitimate positives as well--   
   > , unmapped natural sources, etc.   
      
   The variation of background sources are going to be known.  They also   
   aren't going to move.   
      
   > Just considering the spatio-temporal gaps... sure, a spacecraft is not   
   > going to move very far in terms of angular resolution during the   
   > duration of the gap. Unfortunately, the ratio of gap to signal means   
   > that scanning can be easily defeated by simple pulsed emissions.   
      
   You can't pulse your waste heat like that, nor can you departure burns.   
   Tying to pulse correction burns like that trades not being noticed on   
   some sweeps for have far more sweeps that can see you.   
      
   > Sure,   
   > occasional pulses might be detected, but without repeated pulses at   
   > fixed intervals, you never know if you actually have a single vessel   
   > track, or if you have numerous incidental detections of natural sources   
   > (sunlight reflecting off a smaller asteroid, etc). So, you say that you   
   > will just dedicate sensors to each possible "ping"... but this can   
   > easily be defeated by increased volume of "legitimate" transport   
   > activity.   
      
   Once a ship is known, it's trivial to track.  In fact, it is going to be   
   vitally important to track all of those ships:  Remember that each and   
   every one of them is a WMD.   
      
   What's more, any interplanetary war scenario would also mean that sensor   
   platforms are cheap and easy to deploy.  If they aren't cheap, you simply   
   won't have a space navy to fight these battles and stealth will be moot.   
      
   > Among the other gaps:   
   > signal emission vector- it doesn't do any good to have the most   
   > sensitive detectors if they are not placed in the path of the emitted   
   > energy;   
      
   Directional emission means more waste heat and an even easier detection   
   target for things in the right direction.   
      
   Furthermore, doing it involves doing things that make you more visible to   
   'semi-active' sensors that use the sun as the EM source.   
      
   > signal wavelength- sensitive detectors tend to achieve sensitivity by   
   > concentrating on specific bands of wavelength, which are useless if   
   > other bands are being emitted instead;   
      
   Given that we are generally looking for emissions from heat, you are   
   stuck with IR emissions.   
      
   > low contrast- there is A LOT of background "static" out there, so you   
   > will be virtually invisible if your emission is within the normal   
   > variation of background signal intensities... difficult with a torchship   
   > at full burn, not so difficult if you are limiting emissions to even a   
   > few dozen kW (WISE can detect as little as 50 to 100 watts, RADIATED IN   
   > THE DIRECTION OF THE DETECTOR).   
      
   Now imagine a situation where there are dozens of platforms, all better   
   than WISE and arranged so that there are some in just about any direction   
   you look.   
      
   --   
   Chakat Firepaw - Inventor and Scientist (mad)   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)