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Soyuz and Chinese capsule scorching

Posted by: JamesHughes - Mon Jul 02, 2012 9:04 am
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Soyuz and Chinese capsule scorching 
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Post Soyuz and Chinese capsule scorching   Posted on: Mon Jul 02, 2012 9:04 am
Does anyone else find it odd that the recent Soyuz and Chinese capsules look like they a have been through a furnace and are blacked and streaked, while the Dragon capsule had a few streaks but was otherwise fairly unscorched.

Is it simply down to much better heatshield tech on the Dragon?


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Post Re: Soyuz and Chinese capsule scorching   Posted on: Mon Jul 02, 2012 4:20 pm
Dragons get pretty crispy too. Don't let the publicity shots fool you.

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Post Re: Soyuz and Chinese capsule scorching   Posted on: Mon Jul 02, 2012 7:00 pm
JamesG

Yes, Dragon gets scorched as well, but there is not publicity stunts to it.

Because of the re-entry geometry/attitude it only gets scorched on one side (I assume it is the back/trailing side) where all the soot that gets ablated from the heat shield is deposited.

Dig out the post flight photos of Dragon Flight 1 and COTS 2+ - it is the same for both missions, one side is dark and dirty, the other looks almost new.

As for Soyuz an Shenzou I guess it has to do with a) a different attitude during re-entry (they don't have a lifting flight profile as far as I know) and b) the different shape of the capsule.

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Post Re: Soyuz and Chinese capsule scorching   Posted on: Mon Jul 02, 2012 8:55 pm
Nope. All ballistic capsules have the same flight dynamics. They are trimmed with the CoG off to one side and slightly back from the heatshield in order to produce the lift they need to prevent diving too deep into the atmosphere. This has the effect of exposing the "bottom" side to more heating and plasma blow by.

The post flight shots of the Dragon sitting on deck only slightly dirty are after it's been cleaned up.

Image
Backside, post cleanup.

Soyuz (and Apollo) have the same streaking but it looks "worse" because the TPS is dark and... the Russians don't care how "bad" it looks as long as it works. Doesn't matter ultimately. Gives it "character" and I think most of the heatshield and outer TPS on Dragon are consumable items that will get changed for each flight.

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Post Re: Soyuz and Chinese capsule scorching   Posted on: Tue Jul 03, 2012 6:35 pm
Sorry, I don't see how this is "cleaned" in any way. Unless you count all those scratches from the recovery operations as "cleaning" :P

You are right about the Soyuz, it uses a similar reentry profile and part of the "front side" does get less scorched than the rest, but because the Soyuz has a dark exterior to begin with I haven't noticed that before.

Here is a nice picture I found of a Soyuz post landing:
http://1.bp.blogspot.com/_mWbpIecg-10/T ... pict22.jpg

It still looks a lot worse than the backside of Dragon (even while it is still drifting in the water and nobody has "cleaned" it): http://upload.wikimedia.org/wikipedia/c ... anding.jpg

But as far as I know, Soyuz was never intended to be reusable, so I guess it really is a case of "they don't care, as long as it works" ;)

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