Re: Centaur-Clouds

From: Gerhard HOLTKAMP (
Date: Tue Oct 20 2009 - 17:39:02 UTC

  • Next message: Greg Roberts: "Re: Centaur-Clouds"

    After two days of deliberations I finally think I know exactly what it was 
    that I've seen with the fabulous Centaur pass on Sunday evening.
    The clouds (and also the concentric rings) must have been produced by the 
    hydrazine thrusters rather than the actual firing of the Centaur engine 
    because this engine burns liquid hydrogen and oxygen which would leave pure 
    water vapor (and unless it condenses would not be seen). 
    Just before the escape trajectory burn some attitude maneuvers would be done 
    by the Centaur to get into the right attitude for the burn. This must have 
    caused the first bright cloud which remained near the position of the DMSP 
    F18 satellite. The actual firing did not produce a visible cloud but after 
    that firing some more attitude maneuvers were done to get into the right 
    venting attitude. This caused the fresh cloud which was now at the new 
    (escape trajectory) position. Having looked at it with 10x50 binoculars I 
    definitely saw a red dot (the engine was still hot from the firing) and 
    clouds did not emerge continuously but as *puffs of smoke*. 
    There was a brief pause of cloud generation after the new attitude maneuver 
    and the cloud just expanded and became weaker but then the venting started 
    and caused a continuous cloud generation and the cloud grew brighter again.
    I wouldn't mind if they launch more Atlas Centaur rockets perfoming such 
    Gerhard HOLTKAMP
    Darmstadt, Germany 
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