From: larryg@u.washington.edu   
      
   Most studies of O'Neill type colonies assume that we would get the   
   millions   
   of tons of material from the moon via a catapult.  However, there are some   
   Near Earth Asteroids where the return dV to the earth-moon space is   
   astonishingly small.  For Nereus, 1982 DB, it is about 60 m/s, or 135 mph.   
   This opens the possibility of bringing back enormous payloads   
   on the order of 100,000 tons at a time relatively cheaply.   
      
   For example, a small mass driver with a specific impulse of 200 (approx.   
   2000 m/sec) would need to expend only 3000 tons of material to move it   
   to the earth-moon space.   
      
   However, I don't know enough orbital mechanics to know if we would need   
   short impulses for part of the return as I believe it uses lunar gravity   
   assist.  So does anyone know if the low-g acceleration of a small mass   
   driver would be sufficient, or do we also need higher gee thrust for   
   part of the mission?   
      
      -- Larry Gales   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)