New article on mass-drivers

>From the linked article:
> many asteroids may be less like a single rock and more like a loose
> conglomeration of bodies embedded in dust. Subjected to a nuclear
> explosion, such a "flying gravel pile" might separate. So we would
> find we had only succeeded in converting one single disaster into
> many separate ones. Sometimes Hollywood dramas speak of pulverizing
> an asteroid such that all of its pieces would "burn harmlessly in
> the atmosphere". But an entire sky alit with the blazes of entering
> debris would touch off surface fires of incomprehensible scale.

I would think that you could burn up an a fair amount of stuff in the
atmosphere before it gets to be a problem, even compared to the amount
that causes trouble when it enters the atmosphere in one lump. Have
you found or done anything quantitative to say how much a threat could
be reduced by having part of it burn in the atmosphere, or how much of
the debris might miss the earth entirely if an asteroid were
pulverized a plausible length of time before impact? Is the Nature
article available online?

> one can immediately discard the notion of manufacturing the parts
> for these space settlements here on Earth and then launching them
> into orbit on a rocket. With habitat masses ranging from 4 to 10
> million tons, this was clearly unfeasible for any plausible rocket
> system, regardless how improved over those currently in use.

> This meant such space settlements (and solar power stations, if
> desired on a scale large enough to make a global difference) had to
> be constructed from materials already in space.

I certainly favor using materials already in space. But as phrased,
it doesn't follow: it neglects the possibility that non-rocket launch
systems (mass drivers, skyhooks, or whatever else) might make it
feasible to launch materials for the first settlements from the
surface of the earth.

--- In spacesettlers@yahoogroups.com, "Combs, Mike" wrote:
>
> If anyone's interested, I've added a new article onto my Space
Settlement webpage at: