XPost: sci.physics, sci.space.tech   
   From: gareth.harris@nobody.nowhere.invalid   
      
   John Schoenfeld wrote:   
      
   > Timo Nieminen  wrote in message news:<   
   ine.LNX.4.50.0307110958020.29738-100000@kolmogorov.physics.uq.edu.au>...   
   >   
   >>On Thu, 10 Jul 2003, George Kinley wrote:   
   >>   
   >>   
   >>>if there is no Atmosphere, where do rockets that go in Space get thrust from   
   >>   
   >>Stand on a skateboard on a smooth flat surface, with a bag of rocks. Throw   
   >>the rocks in one direction, and you'll go in the other direction (except   
   >>for the inconvenient effects of friction - use bigger rocks and you should   
   >>see an effect). The rocket works exactly the same way. Throw mass away in   
   >>one direction, and you go in the other direction. "Conservation of   
   >>momentum" is what it's all about.   
   >   
   >   
   > The direction of the rockets acceleration is irrespective of the   
   > direction of mass explusion. I could build a rocket that expels its   
   > mass upwards and it would still accelerate upwards.   
      
   How? Won't that break conservation of momentum?   
      
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