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>
>
> >> >> On Mon, 07 Jun 2010 23:04:47 -0700, Mycelium
>
> >> wrote:
> >> >>
> >> >>Imagine attaching a rocket to a pile of gravel.
>
> >> > If it is large enough to have conglomerated gravitationally to begin
> >> >with, then it is large enough to tug everything along, even if you
> >> >segregate it a bit. If it is more solid than that... then... it is
> >> >more solid than that, and you lose again.
>
> >> Escape velocity from a loose collection of mass a km in diameter is
> >> going to be very low. You're the math whiz, so figure it out. Gravity
> >> is a pretty weak force. The gravitational atraction between two
> >> bowling balls almost in contact is very difficult to measure. You
> >> could literally disassemble some aggregate asteroids by hand, tossing
> >> rocks away at more than escape velocity.
>
> >> And what are you going to do about rotation? Most of these things are
> >> spinning.
>
> >> There are lots of problems associated with attaching a rocket to an
> >> asteroid. A serious one is the requirement to match velocities first.
> >> A nuke just needs to fly past and get within a few hundred meters for
> >> a few microseconds.
>
> >I think you have the distance wrong. A few km may be more like it.
> >You only need to apply enough to the material to boil off some on the
> >one
> >side. In space there is nothing much to take the energy away besides
> >boiling off material.
>
> >> John
>
> Ken, if the rock is only a few kilometers across, you want to be rather
> close (Say 10 to 100 meters) to use as much of the yield as possible.
> Being kilometers away would waste most of the available energy.
It doesn't matter if we waste 99.999% of the energy, just so long as the remaining 0.001% causes the thing to miss the earth. The goal is not to destroy the object, just to protect the earth.
An atomic bomb as a huge amount of energy. We only need to add a little to the object to make it miss.