[AR] Re: kinetic ICBMs (was Re: Nothing to do with rockets.)
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Wed, 6 Oct 2021 16:13:51 -0400 (EDT)
On Tue, 5 Oct 2021, roxanna Mason wrote:
It is thought to have been about a 45m object, 400,000t...
I read one theory that the impactor came to a halt somewhere deep and
outside the edge of the crater rim and was why the drilling operation
never hit anything...
Alas, this comes from the same mistaken analogies as Barringer's idea that
the meteorite had weighed circa 100Mt -- thinking of a meteor impact as
similar to a car crash or a bullet hit. Even at a measly 12km/s :-), the
impact energy greatly exceeds what's required to vaporize the entire
meteor, and that is what happened to most of it.
As soon as it contacted something heavy and solid, i.e. the ground, so
much energy was released that almost everything in the immediate vicinity
of the contact was converted into very hot gas. The result was basically
an explosion, not a great big bullet impact. Hence a 1200m crater from a
comparatively tiny impactor, and *no* major surviving impactor mass -- not
under the crater, not off to one side, not anywhere. Even the bits and
pieces strewn around the vicinity are fragments that came off during
descent, not pieces of the impacting mass itself.
(None of this was understood in Barringer's day; indeed, much of it was
first suggested during studies of Meteor Crater done shortly before
Barringer's death, with confirming evidence accumulating slowly over the
following several decades. Gene Shoemaker's work on Meteor Crater in the
early 60s finally settled the basic outline; the only-12km/s rethinking of
the impact velocity is less than 20 years old.)
Anyway, back to rockets, right?
Not *entirely* irrelevant to rockets, because the same principles of how
hypervelocity impacts behave are relevant to issues like space debris.
But yes, it's time to wrap this up.
Henry
Other related posts: