Re: 100 megaton bombs atop Saturn V rockets

From: John Schilling (schillin_at_spock.usc.edu)
Date: 07/13/04 

Date: 13 Jul 2004 15:50:05 -0700

henry@spsystems.net (Henry Spencer) writes:

>In article <slrnceoqmg.gn6.andrew.gray@compsoc.dur.ac.uk>,
>Andrew Gray <andrew.gray@dunelm.org.uk> wrote:
>>That aside, *has* it been shown it's the "wrong kind of solution"? Other
>>methods have certainly been suggested, but I'm not aware of where the
>>consensus lies on deflection methods (though there are clear downsides
>>to the nuclear-bomb method).

>If you have to do something on short notice, deflection is about the only
>option, and nuclear bombs are about the only way to quickly put really
>large amounts of energy into deflection. Avoid letting anti-military
>paranoia blind you to these facts.

>There are likely to be better ways to deal with asteroids and short-period
>comets, because given enough advance warning, their orbits can be altered
>in less violent ways. However, we may not have the option for long-period
>comets, because we simply don't see them more than a year or so out. And
>of course, we don't *yet* have the near-Earth asteroids and short-period
>comets mapped well enough to be sure we'd have plenty of warning for them.

Is it even possible to map those well enough to have decades of warning
with enough precision to warrant and plan for a diversion effort? If
you can't pin down the CEP to an Earth radius or so, any attempt at
diversion is as likely to cause an impact as prevent one. And even with
arbitrarily good data, computers, and models, there's a chaotic element
to perturbation effects on asteroid orbits that will prevent you from
predicting the trajectory to within 1 Re arbitrarily far into the future.

I haven't seen any good analysis as to what the practical limit is likely
to be in that regard. The lesser problem of predicting orbits to within
~10 Re, so that ~0.01 probability impactors can be identified for further
study, yes, but the question of whether one can then actually say, "We've
now undertaken further study of asteroid XYZ-123 and determined that yes,
it would be a Good Thing to nudge it by 1 Re thataway", reliably, twenty
years in advance, has not to the best of my knowledge been rigorously
addressed.

Have you seen anything in that regard?

>The big question marks for deflection with nuclear bombs are how best to
>turn a massive soft-X-ray flash (which is what you get out of a nuclear
>bomb in vacuum) into propulsion, and how well the object will hold up to a
>fairly sudden shove. Even quite a loose object may be okay for *one*
>shove if you can deliver the force to more or less an entire hemisphere,
>e.g. with an explosion at some distance blowing off a surface layer.
>A more localized shove, or multiple shoves, may be practical only for
>objects with significant structural strength.

Or for multiple shoves seperated in time by intervals sufficient for the
gravitationally bound fragments to coalesce. 

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