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

[Robert Bradbury]

Ok Spike, that helps.

The cable idea is interesting too.  What about tossing down a grappling hook
or some rocket propelled pitons that embed themselves in the surface of the
planet.  Attach them to some spider-silk (like?) cables that have lots of
stretch to them.  You could even gang them in sequence so just as the
spacecraft reaches is 200+g deceleration limit (or the cable snaps) a
second, third, etc. cable which is unstretched kicks in to continue the
deceleration process.

Now, with regard to the hydrodynamic impact regime, I don't care if I'm
above the heat limits of whatever hits the planet.  Its fine if a large
fraction of it vaporizes upon impact (thats what happens to most, if not all
heat shields that use atmospheric deceleration.  The mass being vaporized
has to be less than the mass of fuel one would need to decelerate (or does
it depend upon the Isp of the deceleration method?).

There are two different problems.  Problem 1.  Decelerate the probe to a
speed without subjecting the hardware to greater g forces than they can
withstand.  I think to a significant extent this may depend upon the
thickness of the design.  If the probe is very flat then you don't have the
problem of non-decelerated material crushing the material which is between
it and the surface.  Problem 2.  Shield the probe from the heat generated
during the vaporization of most of the impact/heat shield.  Now, if one has
a heat shield with very low heat conductivity it is going to take some time
for it to burn away upon impact.  This gives one time to launch the probe
away from the hot zone.  So the probe either has to be landing on springs or
has to launch itself back off of the surface to sufficient height to avoid
the "hot zone" until things cool down enough (or perform a second landing
someplace away from the impact crater).  In this case one only has to carry
enough propellent to get a slight liftoff (which on Pluto I suspect isn't
very much).  The timing of all of this is presumably critical.  But even if
you convert all of the shield material into a plasma you don't do that
instantaneously.

As I think I pointed out earlier -- even when meteorites hit the Earth there
is *still* something left with an unmodified crystal structure.  Now,
whether that is true about meteorites hitting the moon I am less certain.
But meteorites are rather stupid when it comes to avoiding long residence
times within a hot plasma.  Another point to reinforce this would be that
~40 tons of the ~92 ton Columbia were recovered.  Some of them were in
*quite* intact [1].  Outside of the box thinking is what is needed here.
What about explosive airbag deployment *after* most of the deceleration has
been done but before the heat conduction begins to fry the probe (in effect
bouncing you out of the crater)?

Robert

1.
http://www.floridatoday.com/columbia/anniversary/columbiastory2201DEBRIS.htm
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