Re: Blowing up an asteroid
- From: Willie.Mookie@xxxxxxxxx
- Date: Fri, 22 Aug 2008 18:35:02 -0700 (PDT)
On Aug 22, 8:46 pm, "Martha Adams" <mh...@xxxxxxxxxxx> wrote:
<Willie.Moo...@xxxxxxxxx> wrote in message
news:b9738092-9aaa-463f-a9a9-5d58ee45ba24@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Aug 22, 3:21 pm, Ian Parker <ianpark...@xxxxxxxxx> wrote:
In view of all you have said about SSP I am a little surprised that
you advocate a nuclear solution.
Its the most cost effective solution for this application. It also
makes non-threatening use of our inventory of fissile materials. I
cannot think of anything more beneficial to humanity than to put all
<big snip here to make space for comment below>
point 1/40,000 the area of the mirror (the limit) gives you 2.6 KW/cm2
that's the absolute limit with perfect optics and everything - 1.366
kW/m2 turns into 1.366 kW/cm2 at 10,000 to 1 - 2.732 kW/cm2 at 20,000
to 1 and 5.462 kW/cm2 at 40,000 to 1.
- NOT sufficient to produce deflagration and thrust without some sort
of rocket device. The simplest rocket device is an electric motor
that powers a rotary flinger/grinder/digger - rocket. this is also
known as a centrifugal catapault.
===========================================
Response concerning important core point.
Which is, it depends upon what's in the asteroid,
If you want to boil water or burn wood all you need is 400 to 1. If
you want to make a rocket out of burning wood or boiling water, you
need a nozzle. If you want to cause deflagration where the particles
become ballistic and fly off in straight lines - preserving momenta
and whatnot - which is what you need for rocket action - then, you
need to heat them at far higher rates, and temperatures. These
temperatures are so high, the differences of what you start out with
are immaterial - the variation is in the noise level..
On the other end of the spectrum, electric motors turning mechanical
devices like centrifugal flingers - just need a rotor housing with a
hole in it - and can chew up anything in their mawl - use maraging
steel throughout and grinding wheels. If you get them spinning fast
enough thrust can be pretty good, but exhaust speed sucks.
if
water or palladium metals or what all,
right - there are differences in the heat of fusion, specific heat,
and heat of vaporization, freezing point, boiling point and all of
that. But take the easiest to vaporize stuff and calculate that
number. Now take the hardest to vaporize stuff and calculate that
number. Now look at those numbers the total energy per kg. Now figure
out the energy of a kg of ANYTHING moving at 20,000 m/s or 40,000 ms/
- and you'll have a number 400 MJ/kg to 1,600 MJ/kg - bigger than any
of the previous two. Multiply that big number by a factor of 2 or 3 -
4,800 MJ tops - to get efficient directionality - and you'll see it
doesn't matter if you want to detonate the easy stuff off the hard
stuff on the surface with a laser or a shaped bomb at these speeds..
but guiding it
into a lunar orbit seems to make immense business
sense.
Yes.without threatening the Earth.
Because, it's accessible there. Which in this
ongoing 'blow it up!' context, had got lost.
Well, blowing it up, as I said, involves a lot more energy and doesn't
get rid of the problem. Because the same orbital mechanics that
deposited all that stuff there, will likely redeposit it, unless you
have several times SOLAR escape velocity. We were calculating energy
for a measly 0.52 km/sec - andyou'd need hyperbolic excess over that.
But if it were say 1 km/sec - you'd increase your energy needs by 4 -
but damn, you're not changing the orbit of all that stuff relative to
the sun very much. So, all the parts have the same center of mass,
and its in the same orbit - even if all the pieces are flying out
faster than their mutual atraction. But, the orbit of all those
pieces doesn't change much. 1 km/sec this way, 1 km/sec that way and
so forth. They still form a band orbiting the sun, that is likely to
get swept back up and reform the satellite. and may not even be a
ball of debris bigger than the entire Earth. That is, you might go
from 250 km to say 2,500 km - above and below the ecliptic and 2,500
sunward and starward - and maybe 100,000 km along the orbit. BUT THE
CENTER OF MASS IS STILL THE SAME. So, the debris will still hit
Earth, if the asteroid was!!! IT DOESN'T GET RID OF THE PROBLEM It
just turns the bullet into a shotgun blast. A big piece of shrapnel
into a lot of tiny pieces of shrapnel.
Guiding the bullet's center of mass to a different location - makes
more sense. Deflecting it to another nearby body, the moon, better
still, its not ot there any more and it didn't take much energy.
Deflecting it to a convenient orbit around another body - even more
for busines reasons.
This is in fact, a whole new province of orbital
exploration. *What's out there* that we could bring
in to near by and orbit it here, thus saving huge
amounts of resource and time?
yep.
There's a key point needs attention, that the orbit
the asteroid is brought into wants to be a *stable*
orbit. I read within the past year or two, that
stable lunar orbits were hard to do but that some
researcher had found a class of them.
There are stable points in the Earth moon system called Lagrange
points.
So the problem
just got a little harder, but its possible yield is
greatly improved.
yes.
Titeotwawki -- mha [sci.space.policy 2008 Aug 22]
.
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- Re: Blowing up an asteroid
- From: Martha Adams
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