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Rolling horizontal lines in SpaceX first stage viewing the second ignition

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bknight:
I have watched many of the SpaceX videos of the second stage igniting.  I noticed again today that when the engine ignites there are rolling horizontal line in the first stage video of the event.  Why does this occur?

JayUtah:
My first thought was that it's a standing(ish) wave effect produced when the second stage plume interacts with the open top of the first stage.  That kind of effect will be highly sensitive to plume density.

But then the effect does seem suspiciously aligned with the video frame, making me think it could also be some kind of video artifact.

cjameshuff:

--- Quote from: JayUtah on May 04, 2021, 06:24:49 PM ---My first thought was that it's a standing(ish) wave effect produced when the second stage plume interacts with the open top of the first stage.  That kind of effect will be highly sensitive to plume density.

But then the effect does seem suspiciously aligned with the video frame, making me think it could also be some kind of video artifact.

--- End quote ---

It might be both, exhaust resonating in the open top of the booster with some visible effect to its brightness/opacity at a frequency close to the frame rate.

Zakalwe:
Its probably vibration from the exhaust plume impinging on the first stage uppers. The frequency probably matches the frame rate of the rolling shutter in the camera sensor. I suspect that it's similar to the rolling shutter effect you get with fast moving objects such as propellers.

https://youtube.com/watch?v=dNVtMmLlnoE

bknight:
To all, thanks for the info.

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