Side notes:   
      
   Having no nuclear power, it will not be detected by neutrino detectors.   
      
   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.   
      
   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.   
      
   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.   
      
   Getting rid of warm-blooded human crew would extend autonomy, but not that   
   significantly: the most energy you have to get rid of comes from the Sun. The   
   biggest contributor may be by allowing a smaller cross-section.   
   That is, until you start operating in the Kuiper Belt or the Oort Cloud.   
      
   The further you are from the Sun, the lower your acceleration and the higher   
   your autonomy.   
      
   Close enough from the Sun and the disk is big enough to be a problem: the ship   
   needs to be cone-shaped to keep in the shadow of its solar-thermal engine, and   
   at some point the cone will be too short to be practical. (Not much of the   
   black surface can    
   reasonably be lit by the Sun.)   
   But at that point, your autonomy may be too low anyway.   
      
   If you are even closer to the Sun (as in, right above its atmosphere, you are   
   better off just putting a mirror on its side: it's not as if the Other Side(s)   
   would put outward-pointing sensors even lower, right?   
   Right?   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)