[meteorite-list] R: friction or ram pressure?

From: Francesco Moser <cojack_at_meteoritecentral.com>
Date: Sat, 25 Jan 2014 20:22:15 +0100
Message-ID: <000001cf1a02$c1e9de60$45bd9b20$_at_tiscali.it>

Thanks for your kind answer!
So we can say:
meteoroids dimensions:
 <~1cm "friction"
>~1cm ram pressure

But I have still a question... how the ablation process works on the bigger
meteoroids?
The ram pressure heats the air, the hot air heats the front surface of the
meteoroid to the fusion/sublimation temperature, right?
But is the collisional process that create oriented shape, ragmaglipts, flow
line ... or what else process??

Thanks

<x>x<x>x<x>
Francesco

-----Messaggio originale-----
Da: meteorite-list-bounces at meteoritecentral.com
[mailto:meteorite-list-bounces at meteoritecentral.com] Per conto di Chris
Peterson
Inviato: sabato 25 gennaio 2014 16:24
A: meteorite-list at meteoritecentral.com
Oggetto: Re: [meteorite-list] friction or ram pressure?

Your understanding is broadly correct, although I don't think "friction"
is quite the right word to describe the heating process for particles
smaller than about a centimeter. The mechanism of heating depends on the
particle size and on the mean free path of atmospheric molecules (and
therefore on height). For centimeter scale particles, most of the heating is
the result of creating a compressed gas zone along the leading edge. For
millimeter scale particles the heating involves collisional processes. Not
surprisingly, there's an intermediate range where both processes are
operating.

Chris

*******************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On 1/25/2014 7:54 AM, Francesco Moser wrote:
> Hi all!
> I have a question for you regarding falling stars and fireballs!
> Which is the physical process that heats a meteoroid during his travel
through the atmosphere?
> Is the friction with the air molecules or the ram pressure of the shock
wave in front of the meteoroid?
>
> I think, but maybe I'm wrong:
> for the smaller meteoroids like the one that generate the falling stars
the main process is the friction, instead for the bigger meteoroid like the
one that generate meteorite on the ground or for example for a Space Ship
like the Space Shuttle the main process is the ram pressure ... I'm right?
>
> Thanks a lot!!!
>
> <x>x<x>x<x>
> Francesco

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Received on Sat 25 Jan 2014 02:22:15 PM PST