From: adam.w.krajewski@gmail.com   
      
   Huh, that's the topic I am interested also, because my warship will weigh   
   something like these 30000 tonnes, + the tug ship, that will carry all   
   antimatter for IS trip.   
   By what I have researches already, there is not much about the mass ratios   
   needed for travel (other than on Atomic Rockets), but they would surely be   
   horrible, which is not seens on Avatar's ISV.    
   About the drive, I have a problem, because even the Beamed Core AM Rocket   
   looses quite a lot of energy in some weird particles that don't interact with   
   our matter a lot, or to gamma rays. So, I think one must use all these gamma   
   rays by enclosing the    
   reaction in a lead pellet or something like that. Anyway, this is all   
   hypotetical, and it would be nice if someone more competent would answer to   
   you.    
   Although, I think that it's possible to make constant - thrust rocket, using   
   mix of antiparticles, some heavier metals as a propellant and also throw in   
   some hydrogen. But, talking about heavy propellant, it will probably increase   
   the thrust at the    
   expense of exhaust velocity. So, smaller Isp? But if you have higher   
   acceleration due to thrust, can you scale the engine so that it becomes same   
   as it would be in engine without heavy propellant?    
   Dang, that's too hard for me.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)