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According to Wikipedia the single engine on the 2nd stage is a YF-20 series engine.

What is causing the faint yellow light on the side of the nozzle where there is a tube wrapped around it?

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above: Screen captures from this YouTube vide Arrow is added indicate the "blob" in question.

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above: Screen captures from this other YouTube vide Similar type of shot. This is the previous launch of Tiangong-2. Seems to be heavily colorized?

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  • $\begingroup$ Looks like the joint between the thrust chamber and nozzle extension glowing with heat. But no reference, alas. $\endgroup$ – Organic Marble Oct 17 '16 at 11:00
  • $\begingroup$ @OrganicMarble In the video (link below screenshot) between 05:55 and 06:05 it seems to be moving around fairly quickly, like exhaust is coming out. (another spot at the extreme right edge of the frame) I don't think hot spots on the nozzle would migrate so rapidly. $\endgroup$ – uhoh Oct 17 '16 at 11:15
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    $\begingroup$ Ah. Not able to watch video at this time, was going by the stills you posted. $\endgroup$ – Organic Marble Oct 17 '16 at 11:19
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    $\begingroup$ In your second screen shot, the vernier at the left of the frame seems to be burning continuously, so I'm guessing that exhaust-plume interaction between the main engine and the verniers is causing exhaust gas to recirculate up around the nozzle, scorching the metal and liberating some material that burns yellow. $\endgroup$ – Russell Borogove Oct 17 '16 at 19:25
  • $\begingroup$ @RussellBorogove I'd be happy to accept an answer that advances that theory, it seems quite plausible. $\endgroup$ – uhoh Oct 5 '18 at 15:05

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