[ExI] Asteroid on track for possible Mars hit

spike spike66 at att.net
Sun Dec 23 17:13:38 UTC 2007

> -----Original Message-----
> From: extropy-chat-bounces at lists.extropy.org [mailto:extropy-chat-
> bounces at lists.extropy.org] On Behalf Of Samantha Atkins
> >
> > Ja, but it isn't clear to me what would cause the thing to
> > fragment.  The
> > surface heats up and boils away violently.  I suppose individual
> > fragments
> > could come flying off, but I don't see that as a major problem.
> Doesn't it depend quite a lot on the composition of the mass?...

Dr. Graps might be able to answer this.  

>  Given that the vast majority of meteors break up to some degree in
> atmosphere I would think there is some worry of breakup from a high
> yield fusion explosion near it...

Hmmm, these are two very different things.  After doing a few BOTECs, I
convinced myself that it would be impractical to try to match the velocity
of an incoming rock: to get out to it, then stop, turn around etc, would
required way more delta Vee than can be practically carried.  (Perhaps 30
km/sec, which is crazy hard to do, don't know if it has ever been done.) It
might be worth a trade study of 30 km/sec delta Vee with a relatively small
fission device as Gene suggested, or 10 km/sec carrying the biggest boomer
we can make.  The payload capacity of a rocket heading to 30 is less than 1
percent of the payload capacity of one heading to 10.  

So that means exploding the device, (which needs to be truly enormous) as
the object and the nuke pass at very high speeds.  What I don't know is how
much time it takes for a nuclear explosion to develop, or to convert most of
the energy from the fusion device into photons.  Is anyone here up to speed
on that, or know how to estimate it?  Does that reaction develop in a
millisecond?  10? 

>   I would think this is even more
> likely the less uniformly dense the object is and partially depending
> on its primary composition.  A comet would be the most fragile of all. -

Ja, a sometimes comet is described as a dirty snowball (Sagan).  I can
imagine a scenario where a nuclear flash causes some of the photons to
penetrate the surface and vaporizes the ice below the surface, pushing the
material above it (on the nuke side) spaceward.  That would only apply to a
translucent object like an icy comet, methinks, so if the object is a rock,
I don't see that it would break up, or if so, why or how.

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