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Comment by tastyfreeze | Hacker News Reader

It is absolutely amazing that deflecting an asteroid is something we can even test. Depending on the size of the flung off boulders it may be preferable to the larger asteroid impacting. However, I suspect that when a potential impactor is considered for deflection it will be big enough that cast off pieces could still pose a threat.

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Due to the chaotic nature of orbital mechanics, small changes in initial conditions become large observable differences in behavior over time. It's also helpful that there is essentially no turbulence in space so every observation over time results in more and more precise estimates for the true orbital parameters of the body under observation.

If the size of the flung-off objects is proportional to the size of the asteroid that may be the case, but it's also possible it's mainly proportional to the force of the deflecting impact. Regardless between a potential extinction-level impact and hundreds, even thousands, of smaller, "Hiroshima-sized" impacts, the latter would still be massively preferable. Statistically the majority would hit the ocean and do little to nothing as well.

> Depending on the size of the flung off boulders it may be preferable to the larger asteroid impacting.

In nearly all cases, breaking an earth impacting asteroid into smaller pieces, many of which will burn up or have less bad impacts, is better unless of course the asteroid would have missed the Earth but some of the smaller pieces hit.

This thread has changed my mind on subject. I'd delete the above but Hn doesn't show a delete button.

I wonder if they used a nuclear warhead instead of a slug, would there be less material ejected due to maybe the rock being vaporized?

does a nuke do the same damage in space, in a vacuum, with zero gravity, and no oxygen and other factors? would it do anything to a rock that's essentially as dense as earths core adjusting for size?

I think it'd be a cool test for them to do though.

My guess is that the rapidly-expanding vapor and debris cloud produced by the explosion is likely to dislodge and eject more material than would result from a passive impactor capable of producing the same deflection. To get the same deflection, you need the same impulse, and in both cases, the impulse is applied as a sudden shock, but if you are using a passive impactor, all the energy is directed in the direction you want the change of the asteroid's momentum to be - so you need less energy overall?

Perhaps the nuke could be made sufficiently large enough where all of the asteroid material would be consumed in vaporization vs a portion deflected?

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