XPost: sci.electronics.design, sci.physics, sci.space.policy   
      
   In sci.physics Robert Clark  wrote:   
      
      
      
   > It's analogous to ion drive in that it ionizes a gas then uses electric   
   > fields to direct the charged gas molecules backwards to provide thrust.   
   >   
   > For ion space drives you want the propellant to accelerate to high speed to   
   > achieve high exhaust velocity. This means you can achieve high speed for the   
   > spacecraft with a small amount of propellant according to the rocket   
   > equation. This requires though a high amount of power to generate those high   
   > exhaust speeds.   
   >   
   > For the corresponding air vehicle propulsion you don't want the air   
   > accelerated speeds to be high because you would be going at slow speed for   
   > the vehicle or just hovering. This can generate higher thrust with a reduced   
   > exhaust velocity.   
      
   The power required to fly by aircraft is the same no matter the motive   
   source.   
      
   A small 4 place aircraft typically has about a 140 kW engine, a small   
   2 place helicopter double that.   
      
   --   
   Jim Pennino   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)