XPost: sci.astro, sci.physics   
   From: ram@zedat.fu-berlin.de   
      
   Jan Panteltje  wrote or quoted:   
   >So that makes me wonder if a spacecraft with just a permanent magnet   
   >that you can move to give you a force in the direction you want to go   
      
     A permanent magnet has a fixed magnetic dipole moment m.   
      
     It would feel a net force F = grad( m B ) in an inhomogeneous   
     magnetic field B.   
      
   |Electromagnetic acceleration of permanent magnets 04078 (arxiv.org)   
   |by SN Dolya · 2015   
      
     from there:   
      
   |The force of the magnetic dipole interaction Fz with the gradient of the   
   |magnetic field can be written as follows:   
   |Fz = m*dBz/dz, (1)   
   |where m - the magnetic moment per mass unit, dBz /dz - the magnetic field   
   |gradient.   
      
     However, in nature there are no fields that can be used to accelerate   
     a spacecraft this way, so one would have to generate such fields.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)