[meteorite-list] New, long, Carancas article II

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Sat, 5 Apr 2008 02:23:25 -0500
Message-ID: <065101c896ed$f0494b90$8250e146_at_ATARIENGINE>

Hi,

    In this context "contained" means contained by the back
pressure envelope of the shock wave. The meteoric material
would be far enough away from the shock not be heated
very much. The shock wave at the sides is the hot stuff
from the front and it's cooling down rapidly.
    Even in the entry of a spherical object the back side is
not ablated. The melted rock on the back is running fluid
from the front, not backside material that melted. And there's
many a fine crusty meteorite whose back side is hardly touched
by melt even though it's only a few inches away from the fire
of re-entry.
    The shock wave is the boundary between material moving
faster than sound (traveling with the meteoroid) and material
not moving faster than sound (the surrounding atmosphere).
Check the Wikipedia entry (very good discussion):
http://en.wikipedia.org/wiki/Shock_wave
    "Shock waves are characterized by an abrupt, nearly
discontinuous change in the characteristics of the medium.
Across a shock there is always an extremely rapid rise in
pressure, temperature and density of the flow."
    In other words, just a little too close and you're dead
meat! Just an inch away, you're OK. The faster an object
goes, the more sharply bent back the shock wave is; as it
slows, the shock wave stands out further away, until at
the speed of sound it's at right angles to the direction of
flight. As long as the sides of object are on the "right" side
of the fiery shock wave, it's safe from being melted at least.
It's like being the heat shadow.
    Both Schultz and I calculate that the object was still
supersonic when it hit, still enclosed in a "detached"
shock wave, so the sides never ablated at any point.


Sterling K. Webb
-------------------------------------------------------
----- Original Message -----
From: <star-bits at tx.rr.com>
To: "Sterling K. Webb" <sterling_k_webb at sbcglobal.net>
Cc: <meteorite-list at meteoritecentral.com>; <meteoriteguy at yahoo.com>
Sent: Saturday, April 05, 2008 12:44 AM
Subject: Re: [meteorite-list] New, long, Carancas article II


It would seem to me that if the stone fragmented in flight and was contained
by the shock wave it would still be heated by the plasma and all the
fragments would develop crusts. There appear to be some pieces with crust,
but enought to match Schultz's theory?

---- "Sterling K. Webb" <sterling_k_webb at sbcglobal.net> wrote:

    Schultz and I both agree that a greater aerodynamic
efficiency will get a chondrite to the ground faster with
less loss of material, making an impact like Carancas
possible.

    What Schultz proposes is that the fragile material of
Carancas fragmented early on but did not "pancake" out
and cause an airburst, but was wrapped by the shock wave
around the hypersonic meteoroid into a "bullet" shape
that stayed together and kept its high speed to the ground.

.... What I proposed was that the Carancas impactor was an
elongated fragment to begin with. That is, it was a "sliver" of
asteroid that was 4 or 5 times longer than its width when it
entered the Earth's atmosphere. The results would be the
same: a faster trip to the ground in (mostly) one piece.
Received on Sat 05 Apr 2008 03:23:25 AM PDT