From: mikkelhaaheim@gmail.com   
      
   Le mercredi 21 septembre 2016 18:31:46 UTC+2, elie....@gmail.com a écrit :   
      
   > On the other hand, I have no idea how feasible a long-range gravimetric   
   detector is, and at which point it can detected all ship-sized objects in the   
   solar system (and track them to see if one is not following its orbit as it   
   should). I've vaguely    
   heard about prototype gravimetric devices used to detect masses across a wall   
   (useful for disaster relief or SWAT teams), but I doubt their range can easily   
   be extended to interplanetary range.   
   > In the far enough future, this may limit this design to smaller crafts, with   
   lower autonomy.   
      
   Negligent. Gravity is a fairly weak force, and the mass of even a relatively   
   large vessel would likely be virtually undetectable at much more than a few   
   meters, regardless of sensitivity. The masses of planets even thousands of   
   light seconds away would    
   interfere with any sensitive gravimetric readings.   
      
   >    
   > Active systems like radar or lidar could be used to detect those, but   
   technologies like featureless shapes and radar-absorbent material are already   
   available to counter those.   
      
   Distance would render radar and lidar pretty useless at distances much over   
   100 000 km, unless you are using a 35m radar dish with a multi-MW transmitter   
   source... something you would not be able to fit on any non-dedicated   
   platform. Even then, the    
   return signal might be questionable with stealth tech.   
      
   >    
   > I am not sure how much more complex it would become to adapt it to multiple   
   star systems. Good luck if your system has four stars.   
      
   Last I heard, a system with four stars would most likely have rendered any   
   additional mass into dust... thus, virtually no resources worth defending, and   
   virtually no possibility for life to evolve. Even visiting life forms would   
   probably find it    
   difficult to survive in such a system for more than a few days.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)