From: gherbert@gw.retro.com   
      
   David Given   wrote:   
   >Does anyone have any references to Cassini's main engine technology?   
      
   Yes, it's a pair of Aerojet (formerly Marquardt) R-4D rocket motors.   
   Google "cassini r-4d" and you get a bunch of good results.   
      
   >I read a report on the SOI burn recently; 600m/s dV, with a continuous   
   >attitude change throughout, after having sat idle in poor storage   
   >conditions for seven years.   
   >   
   >So, how does it work? What sort of propellants does it use? Hypergolic, I   
   >presume, but hypergolic propellants aren't very stable and the very long   
   >shelf life requires stability. Is the engine itself steerable or were they   
   >using the thruster system to change attitude during the burn? (For that   
   >matter, what *is* the thruster system? Cold gas?) What's the total dV   
   >capacity and thrust?   
   >   
   >I can't seem to find any references on the 'net, which is surprising...   
      
   The R-4D burns Nitrogen Tetroxide and MMH or Hydrazine, with a thrust   
   of about 100 lbf, Isp of about 312 seconds.  It weighs around 4 kg.   
      
   Tetroxide and hydrazine store very nicely.  Many very long duration   
   spacecraft have used them.   
      
   The R-4D was developed in and first used for attitude control   
   thrusters for the Apollo Service Module and Lunar Module spacecraft.   
   Variants are still used today for orbital insertion of GEO sats and   
   various other applications, including Cassini.   
      
      
   -george william herbert   
   gherbert@retro.com   
      
   --- SoupGate-Win32 v1.05   
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