Shuttle/satellite re-entry temperature, simple question!

  • Thread starter elegysix
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  • #26
cjl
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Fair enough. I probably should have caught that myself. They are still a 30-year old technology that are very damage-prone, expensive and time-consuming to repair and maintain, and are not nearly reliable enough for any industry other than space flight (for example, airlines). New materials are needed for sure, though I doubt you would disagree with that.
Oh, absolutely. Honestly, in the absence of better analysis tools, I think ablatives are the best current option, as they can handle much higher heat loads with much less cost and fragility than the reusable options. None of the current methods are what I would describe as great though.

And yet out of all the factors you mentioned, the bottom line comes down to speed, temperature and the time spent at those conditions. Heating rate is determined by the velocity (effectively the convection coefficient) and the temperature of the boundary layer (itself a function of velocity and other smaller factors).
Well, that and one more factor: atmospheric density. Velocity and density pretty much determine your heating rate for any given shape.

As for the rest of what you said, I absolutely agree. Fortunately, computerized methods are improving and computers are getting faster, but we're still a long way from a truly good understanding of what is happening and how to model it accurately.
 
  • #27
boneh3ad
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Well, that and one more factor: atmospheric density. Velocity and density pretty much determine your heating rate for any given shape.
A valid point. That is why peak heating doesn't occur at the fastest portion of the entry (as I am sure you are aware but other people may not). If I recall, it typically occurs at a fairly low Mach number compared to the Mach 36 or whatever it is at which the shuttle typically enters.

As for the rest of what you said, I absolutely agree. Fortunately, computerized methods are improving and computers are getting faster, but we're still a long way from a truly good understanding of what is happening and how to model it accurately.
Even DNS can't really touch a lot of these questions yet due simply to computational limits. This stuff doesn't even attack the portion of the problem that addresses boundary layer stability and surface chemistry.

Of course the real question is whether or not elegysix is sufficiently confused yet.
 
  • #28
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Haha, no - i'm not confused. I've learned a few things from this thread, the most important being that the physics of this system is not well understood. :D
 
  • #29
russ_watters
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Haha, no - i'm not confused. I've learned a few things from this thread, the most important being that the physics of this system is not well understood. :D
Ehh, I'd say it's pretty well understood, it's just complicated: the issue with your OP is that it really isn't a simple question and no amount of understanding is ever going to make it simple. Turns out rocket science really is rocket science!
 

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