From: henry@spsystems.net   
      
   In article <41E480FD.4C596FDF@frontiernet.net>,   
   Joann Evans   wrote:   
   >   While we're at it, I note that the Delta IV exhaust was a pretty   
   >easily seen orange-ish color, as opposed to the virtually invisible   
   >(save for shock diamonds) exhaust of an SSME or RL-10 (as seen on   
   >DC-X/A) at launch. Is this because Delta runs more hydrogen-rich, or is   
   >it something else?   
      
   You could see the DC-X plumes briefly when it changed throttle settings,   
   perhaps due to impurities in the LH2.  But I think the accepted   
   explanation for the Delta IV plumes is that they contain crud from the   
   ablatively-cooled nozzle.   
   --   
   "Think outside the box -- the box isn't our friend."    |   Henry Spencer   
                                   -- George Herbert       | henry@spsystems.net   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)