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

[Russell Wallace]

On 2/18/06, spike <spike66 at comcast.net> wrote:
>
> 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.)


Not that bad! I see Amara's used an estimating program to get some data,
thanks Amara - a couple orders of magnitude need to be added to that, since
the entered speed was 15,000 km/s rather than 150,000, but the energy still
comes out in the ballpark of 20 gigatons TNT equivalent. Not something you'd
want to stand around watching, but not a mass extinction event either.

(I suspect the field of craters is an artifact of the program being designed
to handle things like the Tunguska impact. A relativistic projectile would
certainly turn into plasma as soon as it hit atmosphere; I'm guessing there
wouldn't be time for the plasma to disperse much, though, and would stay in
a reasonably concentrated beam, making a single crater.)

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


Spoilsports :P That sounds fun! Though AFAIK such a weapon would be of
doubtful utility, since a solid slug needs to score a direct hit to kill the
target, and it'd be hard to guide it accurately with the plasma sheath
blinding it while it was ploughing through the atmosphere.

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.
>

Definitely - you wrote a good explanation of why soft landing on a solid
surface at 14 km/s is a nonstarter.

You could try aerobraking, but that's a tricky maneuver and there's the
question of whether there'll still be enough atmosphere not yet frozen out
by the time the probe gets there. A flyby was the best option for this
mission, given the time and budget constraints.

- Russell
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