Marrying asteroid defense and asteroid mining

--- In spacesettlers@yahoogroups.com, "ANTIcarrot"
wrote:
>
> As a point of note here: If we're going to send a big heavy 'bruce
willis'
> style space ship to 'save the world' I say do the job properly and
use a few
> hundred well placed nukes. In fact use nukes anyway. They're much
more fun
> than mirrors.
>

one of the theories ive heard bantered about is using a series of
nukes to vaporize a large part of the surface without actually
impacting the asteroid. since the shockwave (what there is of it) of
a "high altitude" explosion would be spread over a large portion of
the asteroid, it would not cause it to break up. the heat, radiation
and the little shockwave that did occur, would vaporize the entire
surface regolth
>
> > 1) [the mirror's orbital path] would be extremely complex.
> > 2) all but the smaller asteroids would have a gravity of their own
>
> Very true. However a big enough mirror to do the job woudl be a
functional
> solar sail; and would have to constantly manouver against it's own
thrust
> anyway. An asteroid small enough that we have even a hope of moving
(in a
> dooms day scenario) will probably not impose significantly worse
problems on
> the solar mirror/sail's 'skipper' than everything else. I think.
>
> > perhaps i misunderstood what you wrote,
>
> Not what I wrote.
>
> > a better way would be to have a hundred mirrors on a frame
>
> I can see no point in the frame, other than as a psychological
crutch of
> some kind. Or possibly a cash-cow for whoever had to build it. The
kind of
> mini-mirror I described was deliberately independent of all the
others
> specifically so that no single failure of a component woudl bring
down the
> entire system. And because we coudl design and build such systems
today. In
> fact several proposed space telescopes use such frame-less
techniques. If it
> works for spotting planets I see no reason for a frame in this case.
>
> > the problem is that the heat would dissipate in to the rock and
space
> > very quickly.
>
> That's a problem for any mirror based approach.
>
> > that depends on how far away the sun is. it would also have to
> > overcome the greater momentum of the rock vapor
>
> I remain rather skeptical that any kind of mirror could produce
very large
> or useful ISPs. Without a rocket bell to shape it, the expanding
gasses
> would mostly go sideways rather than 'upwards'.
>
> > i dont think the
> > wearing away of the grates would be so bad.
>
> Depends on how long they last VS how long you need them for. For a
few
> months thrusting (existing applications) it's pointless. For more
than that
> (like a trip to mars say) you'd need replacement gratings, as
they're the
> part that wears out first.
>
> > all elements that are found on earth, are found in the asteroids.
>
> Yep. You'll also find water up there. I wouldn't recomend drinking
it or
> using it to fill up the radiator on your space-car though.
>
> > would require a refinery, but since its going to be mining the
> > asteroid for the mass driver anyway, i dont think it would be that
> > great a problem.
>
> As others have pointed out, mass drivers eat anything. Ion engines
are a lot