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In watching the SpaceX SES-12 launch last night, I noticed what looked like the fairing of the rocket glowing a bit a while after launch. This was most obvious in the SpaceX video SES-12 Mission about T+01:30 to T+01:50. My first thought was this likely was just a reflection off the bottom of the fairing of the bright rocket exhaust during the night launch, but it seemed more steady and all the way around the fairing's circumference than what I would have anticipated just from reflected exhaust glow.

So, my question is whether this perceived glow was actually aerodynamic heating of the fairing (and not reflected light), and if so, what typical maximum temperature does the fairing achieve during launch?

screen shot of YouTube SES-12 Mission

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    $\begingroup$ The bottom end of the fairing is probably the part of the launcher that's the least subject to atmospheric heating. It would definitely not be hot enough to glow at mach 1.6. It's reflected exhaust light. $\endgroup$
    – Russell Borogove
    Commented Jun 4, 2018 at 15:10
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    $\begingroup$ Looking at this image (bottom right) I'd say, yes, they do get hot. twitter.com/SpaceX/status/1002268835175518208 The distribution looks like it happened while the fairing was closed and not on their way down. $\endgroup$
    – asdfex
    Commented Jun 4, 2018 at 17:30
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    $\begingroup$ ... But I agree that what you see in the video is reflected light from the exhaust. $\endgroup$
    – asdfex
    Commented Jun 4, 2018 at 17:36

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Most probably it is only a reflection from engine flames. Why it cannot be because of heat. The reason behind that is that the part glowing in the picture is the place that has the least aerodynamic interaction. In this video, you can see that the part of the fairing you're asking about is exposed to least aerodynamic pressure. As we can see, it would not heat enough to glow, it just a reflection of engine flames.

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    $\begingroup$ Ah! I think you are right. The "bottom" of the fairing flares out and has line of sight to the expanded plume at 26 km altitude. Since it's white with a diffuse/matte surface it will "glow" in the reflected light. Thanks! $\endgroup$
    – uhoh
    Commented Jul 6, 2020 at 10:10
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There’s some information available about heating later in the flight.

First, an answer to another question provides evidence that fairings are released when the heating drops to 1135W/m2.

There’s also visual evidence at about 3:38 into the SES-12 flight. Just after the fairing separates, it’s visible on the webcast in an IR view:

enter image description here

That blob in the mid left is the fairing. From the color, it’s significantly higher temperature that the engine parts on the right: it’s been heated.

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    $\begingroup$ Might it be heated by (or reflecting the heat of) the exhaust? $\endgroup$
    – jkavalik
    Commented Jun 5, 2018 at 5:32
  • $\begingroup$ temporary -1 until you attempt to address "my question is whether this perceived glow was actually aerodynamic heating of the fairing" with at least a tentative "yes" or "no". Do you think the fairing could survive being red hot in visible light? $\endgroup$
    – uhoh
    Commented Jul 4, 2019 at 2:06

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