Author Topic: Analysis of STS-131 exhaust plume images  (Read 3792 times)

Offline WilliamPardy

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Analysis of STS-131 exhaust plume images
« on: 03/04/2011 06:13 pm »
Hello.   Was there ever any discussion or official analysis of what exactly could be seen in the unique post-staging exhaust plume of STS-131?  Could any shuttle experts comment on the phenomena visible in these two photos?  There appear to be three main plumes with initially divergent paths that then re-converge somewhat, plus a fourth plume at the bottom that is thinner than the others but apparently separate.  The OMS engines were burning at this time (T+ 4 minutes), so I wonder if that fourth trail could be OMS exhaust.  Also, the second photo (MET unknown) was labelled by the photographer as the shuttle’s roll to heads up, but there seem to be no other photos of that maneuver for comparison and I’d appreciate an expert opinion.  Is it a one-of-a-kind photo?  Thanks.  Bill 

Offline Jim

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Re: Analysis of STS-131 exhaust plume images
« Reply #1 on: 03/04/2011 07:19 pm »
Can't really "count" plumes from the side.  Since the nozzles are in close proximity, they merge and there are many interactions.

Offline WilliamPardy

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Re: Analysis of STS-131 exhaust plume images
« Reply #2 on: 03/05/2011 02:03 am »
OK.  So those three main plumes are an illusion that was only coincidentally created by three engines.  I can accept that, if that's the word.  Can you give me any examples of how the plumes interact and form the illusion of separate streams, or is it too complicated?  Those illusory streams rotated rather coherently in the second image, as if visible from every angle (assuming this was indeed the roll to heads-up and not an illusion), albeit there there aren't exactly three of them visible at that point.  More like two, a fatter one and a thinner one, and the jpeg is unfortunately cruddy.

Offline ugordan

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Re: Analysis of STS-131 exhaust plume images
« Reply #3 on: 03/05/2011 09:56 am »
If other launches are any indication, i.e Atlas V exhaust pattern, Saturn V exhaust pattern, the 3 "thick" parts of the plume are not the individual exhausts of the SSMEs, but the points where those individual plumes collide in low atmospheric pressure. This creates a localized higher pressure region at those points and the plume (well, it's ice crystals at this point) appears thicker and expands further away than the "normal" SSME exhaust. There are still 3 of them because the engines have a triangular setup.

Look at a simpler effect with an Atlas V. Likewise for Saturn V which had a square engine setup this resulted in a cross-like exhaust pattern.

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