[extropy-chat] Pluto New Horizons launch -getting ready

[spike]

________________________________________
From: extropy-chat-bounces at lists.extropy.org
[mailto:extropy-chat-bounces at lists.extropy.org] On Behalf Of Russell Wallace
...

>That doesn't sound right. Consider extreme cases: taking a 1 meter
projectile with a mass of 1 ton, suppose the velocity were 0.5c; then the
crater depth would be far more than a few meters...


Ja of course with an example that extreme, all bets are off.  A 1 ton
projectile going 0.5c would shatter the planet, forming a second asteroid
belt.  (I think.  I need to do the calcs on that, but I suspect it would
punch clean thru like a bullet thru an apple, taking a bunch of stuff along
with it as it leaves the solar system.  Or that particular material would be
left behind with a few megatons of material from the other side of the earth
blasted into space.  Or I don't know: would it fuse a bunch of material to
iron in an endothermic nuclear reaction that would absorb most of the
energy?  Amara et.al. what would happen if a ton of stuff hit the earth at
.5c?  Surely it would be a bad hair day for humanity and the rest of
animalty.)


> Or suppose it were made of aerogel, then the diameter would be
substantially reduced...



Ja, I don't think the models deal with anything as fluffy as aerogel.  {8-]


>I'm wondering whether the above conclusions are approximately correct
within a certain range of density and velocity, or whether there are effects
the simulation in question didn't take into account, or what...


I think so.  We were offered a number of decommissioned nuclear missiles to
propose nonmilitary applications.  The notion was to see what happens if we
made a tungsten cylinder, approximately 80 mm diameter and a couple meters
long, hurl it half an earth radius aloft, then let it come back down and
punch a hole in the ground.  We did the computer models on it and found it
doesn't go all that deep, so we looked at rocket boosting the terminal
velocity.  We found that it didn't go any deeper.  That was kinda cool for
me, because it caused me to realize why the moon looks the way it does.

We never did do the experiment.  The notion was to make our money back by
selling video of the impact or by sponsoring a contest to see who could
guess the impact site.  Most of the profit scenarios involved gambling of
some sort, which the company didn't like, the bunny huggers didn't like the
notion of vaporizing a quarter ton of tungsten, the no-nukes crowd didn't
like our using the decommissioned missiles as playthings, the usual nervous
nellies didn't like the idea of this enormous spear possibly going off
course and accidentally punching a hole reactor of the Springfield nuclear
power plant, or the Vatican, the local elementary school, that kinda stuff.
{8^D 


>(I read somewhere that all impact craters are roughly the same shape,
diameter something like 20 times the depth, with the dimensions being
proportional to the cube root of energy; but I don't have a reference to
hand, and don't know whether the statement is true or not.)

- Russell


Cool, thanks Russell.  One must be careful of overapplying the simple rules.
The simplifications I described should be used only for a long pointy
projectile, even tho I used it to theorize that any kind of anchor or cable
one tried to drop on Pluto at 14 km/sec would be toast.  I still think
nothing would survive impact at those speeds, but the hydrodynamic impact
relationships were for long pointy things.

spike