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

[Alejandro Dubrovsky]

On Thu, 2006-02-16 at 21:13 -0800, spike wrote:
> 5.  Imagine you are a tungsten molecule sitting in the aft end of the 1
> meter long impact lander in the above scenario.  You can see everything,
> since the impact lander is transparent to you (atoms are, after all, nearly
> all empty space, with a tiny dense wad of nucleus way inside this
> probability- wave of electrons).  You approach the planet surface at 10 km
> per second, or rather 10 millimeters per microsecond (a microsecond to an
> atom is a long time).  Like the train passenger in scenario 1, you watch the
> impact begin at time 0.  As the microseconds tick by, you study the
> interface between the spacecraft and the quickly vaporizing planetary
> surface.  This is a wild place, with solid material being blasted to plasma.
> This interface is coming toward you at a rate of 2 mm per microsecond.
> Unlike in scenario 1 above, you experience no deceleration at all.  You can
> see that the shockwave interface vaporizes everything as it passes, but the
> molecules upstream of the shock wave experience nothing at all.  Here's the
> punchline: if the spacecraft is in the hydrodynamic regime, there is nothing
> that can be done, no explosive devices, no springs, not one thing, that can
> save that aftmost molecule from experiencing that bond-shattering shockwave.
> Like the meteor that created that crater near Winslow Arizona, physical law
> dictates that the impact lander will be vaporized, completely.  The crater
> will end up being about five meters deep, with its diameter a function of
> the mass and speed of what used to be the impact lander.

Thanks for the excellent explanation, Spike.  
A query:  The incoming energy is provided by the kinetic energy of the
lander, which is proportional to its mass. The energy is going into
vaporising it, which is also proportional to its mass, but some of the
planet is getting vaporised too, and the more lander there is, the more
planet that is going to get vaporised (if I read your explanation
correctly).  Wouldn't this vaporisation energy then, at some large
enough lander mass,  be above the kinetic energy of the lander?