[meteorite-list] Space station moves to avoid debris

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Sun, 4 Feb 2007 20:20:28 -0600
Message-ID: <007b01c748cc$34c2d320$22e68c46_at_ATARIENGINE>

Hi, Impact Fans,

    Well, in previous energy calculations, I forgot to divide
by two; oh, well, it's only a numerical coefficient. You can
always put it in later... Such calculations are an idealization
of the real process of degrading kinetic energy, a kind of
summation of the process.
    The case of a bullet and a meteoroid of the same energy
are mechanically quite different: the bullet is a high mass,
low velocity case; the meteoroid is a low mass, high velocity
case (at least the ones we've been talking about).
    In space, a bullet would behave almost exactly like it
does down on Earth. On Earth, the meteoroid would just
be a short streak of fire as it burned up in 2 feet of travel.
    The energy per unit mass of the bullet is very low; the
same quantity in the meteoroid is very high. The paintflake
weighs 1.0 gm, travels at 10 km/sec. E = 50,000 joules (or
50,000 joules/gm). The rifle bullet is 100 gm, travels at
1 km/sec. E = 50,000 joules (or 500 joules/gm). Despite
having the same energy, the paintflake is, in one way, a
hundred times more "energetic."
    Identical energies, vastly different energy densities.
Here's what happens...
    The bullet strikes the window of the shuttle. Slicing time
down in tiny bits, the point of the bullet strikes the perspex
at speed; a small cluster of metallic molecules try to occupy
the same space as a cluster of glassy polymers. The puzzled
kinetic energy is "released in all directions," chiefly by electric
and Van Der Waals forces.
    The crystalline structure of the metal does not allow
movement of the atoms but they transfer energy along the
bonds; in the macro world, a shock wave moves backwards
through the bullet, likely slower than the local speed of sound.
This energy is not great enough to break the metallic bonds
and allow the bullet atoms to escape each other and carry
the energy in all directions, and all the atoms further back
in the bullet are still moving forward.
    Over on the glassy side, the energy is more than sufficient
to break the molecular bonds along the much weaker crystalline
planes of the window material; on the macro scale, it cracks.
(The fact that the much more massive window is made of weaker
material is crucial. If the window were a 3" slab of steel armour,
the bullet would be the one to say 'uncle,' deforming, breaking,
some fragments flying in "all directions," the rest melting.) In the
glass or perspex, fragments will spall off its backside, flying in
"all directions," as the crystal structure is broken, the process
continuing until the bullet wins the argument about whose atoms
get to occupy the disputed space.
    Now, the paintflake...
    Despite the energy of the paint atoms, the mass of the window
is more than sufficient to bring them to a dead standstill by the
interaction of the aforementioned electric and Van Der Waals
forces in the glass AND the glass's inertia. In the flake, the energy
has all routes open. Molecular bonds are broken but the energy
they release only makes things worse. The atoms of the light
weight flakes continue on to the target without impediment,
piling on into the mess at high speed.
    Very quickly, the kinetic energy is distributed among the paint
molecules, and then their components, individual atoms that leave
their mates, electrons that leave their atoms. The process is heat,
its product is plasma, tight and compressed. It expands in all
directions, freely everywhere except where the window happens
to be in the way. The window craters, or breaks, depending on
the total energy release.
    In both cases, the energy is released "in all directions" but
only by being "attached" to pieces of matter and only where
matter is present. The energy is entirely carried by this matter
UNTIL the matter is excited enough to spit out photons in the
attempt to get rid of the nasty stuff. The photons don't get far;
they run into other pieces of matter, churning the tight mass
into a uniform high-energy state: plasma.
    Only the "plasma" situation is completely omni-directional,
so it seems that bullet event is directional; there's not enough
energy to randomize the motion of the atoms in the bullet. If
the bullet had the same energy density as the paintflake, the
events of the impact would likely be the same. Assuming a
thick (massy but weak) window, the bullet would transform
into plasma at the point of contact, THEN blow out the entire
crew cabin of the shuttle (10,000 times more energy than
that little paintflake).
    The actual paintflake that hit the shuttle window was likely
0.10 gram (or less), not 1.0 gram, so it only "damaged" the
window. Lucky.
    The chief difference is whether the energy event is big
enough to convert the matter carrying the energy from the
solid state, however fractured and fragmented, into the old
"atom free-for-all" extremely dissociated state of plasma.
It's whether you reach that phase transition that distinguishes
the two kinds of events.


Sterling K. Webb
--------------------------------------------------------------
----- Original Message -----
From: <lebofsky at lpl.arizona.edu>
To: "Sterling K. Webb" <sterling_k_webb at sbcglobal.net>
Cc: <meteorite-list at meteoritecentral.com>
Sent: Sunday, February 04, 2007 6:14 AM
Subject: Re: [meteorite-list] Space station moves to avoid debris


Hi Sterling:

I am not a munitions expert, but I think it would be more appropriate to
compare the meteoroid with a speeding bullet. The TNT energy is released
in all directions while a bullet's (or meteoroid's) energy is directional
(at the target). I have seen what the window of the Shuttle looks like
after it has been hit by a paintflake. It looked like a beebee gun had
been using the window for target practice.:

http://www.biblehelp.org/ufo4.htm

Larry

On Sat, February 3, 2007 5:55 pm, Sterling K. Webb wrote:
> Hi, Rob, Darren, List,
>
>
> One gram traveling at 1000 m/sec, when stopped
> abruptly, releases its kinetic energy, which is 1000 joules [kg x
> (m/s)^2].
> The combustion energy of
> TNT is 4600 joules per gram, so that energy release
> is the equivalent is 217 milligrams of TNT. Doesn't sound like that much,
> does it?
>
> In the USA, the legal limit for fireworks is 50
> milligrams of pyrotechnic material. [Code of Federal Regulations, Title
> 16,
> Volume 2, Section 1500.85].
> This is the traditional M-50, or perhaps the "cherry
> bomb." Since pyrotechnics are weaker than TNT, imagine four to eight
> "cherry bombs" concentrated
> on one tiny spot...
>
> Of course, today's "cherry bombs" are not as
> good as yesterday's (pre-regulation) "cherry bombs," but as a child, I
> fractured the brass casing (3" x 12") of a shell for 37mm anti-aircraft
> cannon with ONE "cherry bomb." No better fun for an nine-year-old
> than a bagful of small high explosives and a bunch of old cannon shells,
> is
> there?
>
> How thick are the walls of your space station?
> Your space suit? Your visor? That hose you're
> breathing through? Or any of the thousands of things you need to stay
> alive?
>
> If that gram is coming in from beyond the
> Earth's gravity, you could close on it at almost
> 20 km/sec, the equivalent is about 85 grams of
> TNT. Disastrous.
>
>
> If the orbit of a piece of rubble is not oriented
> with your orbit, but at an angle to it, you and the object are "crossing"
> at some vector product of your velocities. This is the most serious and
> likely hazard.
>
> If you were in an equatorial orbit and the rubble
> was in a polar orbit and you had a geometrically "perfect" collision, the
> impact velocity would be 1.414 times the orbital velocity, with each gram
> carrying the equivalent of 27.3 grams of TNT in kinetic energy. Known in
> the trade as the Chop Suey Special.
>
>
>
> Sterling K. Webb
> -------------------------------------------------------------
> ----- Original Message -----
> From: "Rob McCafferty" <rob_mccafferty at yahoo.com>
> To: "Gerald Flaherty" <grf2 at verizon.net>;
> <meteorite-list at meteoritecentral.com>
> Sent: Saturday, February 03, 2007 2:16 PM
> Subject: Re: [meteorite-list] Space station moves to avoid debris
>
>
>
>
> --- Gerald Flaherty <grf2 at verizon.net> wrote:
>
>
> but a centimeter sized particle traveling at
>> those speeds?? Help.
>> Jerry Flaherty
>>
>
> What Darren said is how I understand it too. As for
> 1cm particles, nah This shield is designed to protect
> against micrometeorids travelling at a relative speed of 20km/s. It'll not
> protect you from big stuff though I suppose the relative speeds of orbital
> debris is likely travelling much slower.
>
> Even so, wouldn't fancy their chances against a pea
> sized bit of weather sat even if it ONLY had a collision speed of 1000m/s
>
> Rob McC
>
>
Received on Sun 04 Feb 2007 09:20:28 PM PST