Re:SES-10 Mission
by david-given on Thursday March 30, 2017 @06:51PM
(#13999626)
My heart attack moment was during the launch when I started seeing flame flickering around the tops of the engines... and then I thought to look at the altitude indicator, and realised they were at about 10km, and it was just the plume expanding as the atmospheric pressure dropped.
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The flames around the top of the engines is normal, it's the exhaust from the turbo pumps feeding the main engines.
Check this page, the Merlin uses an open cycle, where fuel/oxidizer used to fuel the pumps is just dumped overboard.
https://en.wikipedia.org/wiki/Gas-generator_cycle
This picture clearly shows both exhausts: https://en.wikipedia.org/wiki/Merlin_(rocket_engine_family)#...
#/media/File:SpaceX_Testing_Merlin_1D_Engine_In_Texas.jpg){kind=link}
Yeah, it's normal, and it usually ends up getting sucked backward, presumably due to the turbulent airflow in the space between the end of the vehicle and the engine nozzles:
Echostar: https://youtu.be/zEfEBJfD_RE?t=18m23s
For some reason that effect was much more pronounced during this flight (at least in the video) than in previous launches that I watched. Maybe it was because of the camera angle looking more at the side of the rocket when usually you are looking more at the bottom.
I got extremely worried when I saw that happen too. I didn't even think to look at the altitude indicator.