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Part of me gets that you can't "kill" an asteroid, and that a giant rock moving towards the earth would just be turned into many smaller rocks moving towards th

by mabbo 11y ago

Part of me gets that you can't "kill" an asteroid, and that a giant rock moving towards the earth would just be turned into many smaller rocks moving towards the earth... but that said, I think this sort of thing still might be useful, and I'd love someone to explain to me otherwise. First, small rocks more easily burn up on their way down. So smashing a big rock to pieces increases the surface area enough that maybe that can make it safer for humans. Secondly, perhaps the energy hitting the big rock would 'deflect' it ever so slightly. Fire it early enough, and you can make it completely miss the earth. Thoughts?

iSnow 11y ago
Impact energy would rise with the cube of the diameter, I guess. So splitting up one large asteroid into a swarm of smaller ones is desirable. With any luck, some of the debris would even miss. The bigger problem is that that kind of missile system can be easily weaponized (China and the US have successfully tested satellite killers and the USSR maybe too), so simply enhancing ICBMs for that without international oversight is problematic.
- cocoablazing 11y ago
  That relation is equivalent to conservation of mass, and wouldn't account for any energy losses. As the asteroid is fragmented, its total cross section rises, increasing energy deposition in the atmosphere, reducing available energy for ejecta. WRT to arms-control regimes: What's the difference between an asteroid-killing BM and an ICBM? Only the warhead count. START inspectors would count such a launcher toward the cap.
workitout 11y ago
The smaller pieces might still be big enough to survive atmospheric entry. Now instead of one problem, you have many. Deflection sounds like a great idea, hit it right and send it off to a safer orbit.
- mabbo 11y ago
  More problems that are smaller may be better overall. With more total surface area, the air would absorb more of the total energy coming at us. You don't want another K-T extinction event when you could just have three cities wiped out instead.
  - workitout 11y ago
    If you can guarantee just three cities. Either way, not sure why I was downvoted for having an opinion on the matter. Also I'm wondering why HN moderators allow such downvoting which discourages well intended discussion and participation.
mapt 11y ago
You can use a nuke in multiple ways. As a deflector (launched years or decades from impact), you can nudge the impactor out of its present orbit by gently ablating one side from a distance; You can do this iteratively until the impactor's orbit changes enough to miss Earth. Decades is sufficient for some of the continuous-thrust alternatives, though, depending on scale. As a point defence weapon (launched weeks or months from impact), you can send the nuke in as close as possible and detonate in order to break up the body. Yes, this would cause lots of smaller impactors, but over some size ranges it's preferable because ablation is insufficient. If 99% of the smaller impactors miss Earth, we win... in some cases. Just breaking up a large impactor (at the very last minute, launched minutes or hours before impact) doesn't help so much if everything still hits Earth, because a planet-killer turns into hundreds of city-killers randomly spread out. On the other hand, a small impactor could be dramatically affected by a nuke, with plausible amounts of vaporization going on. There's quite a lot of risk surface in small impactors, and they would be hard to spot until very close. --- Bong Wie is working through a NIAC grant on the problem: http://www.spacesafetymagazine.com/space-hazards/asteroid-hitting-earth/innovative-hypervelocity-nuclear-interceptor-spacecraft-mitigating-impact-threat-asteroids/ http://www.spacesafetymagazine.com/space-hazards/asteroid-hi... One interim observation: a nuke which detaches from a small cratering round which hits first, digging a hole for the nuke to fit in, would multiply its effectiveness severalfold. It's a very different problem in each different size class of impactor (as well as orbital classes). 10m, 100m, 1000m, 10000m are all of concern in unique ways; each order of magnitude increase in diameter raises mass by three orders of magnitude.
- gherkin0 11y ago
  > Just breaking it up (at the very last minute, launched minutes or hours before impact) doesn't help so much if everything still hits Earth, because a planet-killer turns into hundreds of city-killers randomly spread out. Wouldn't smaller objects burn up a greater proportion of their mass in the atmosphere (due to the increase surface area) and kick up less of a dust cloud once they impact? Could hundreds of city-killers leave some areas unscathed and still populated and habitable? I think it would be a great help if a planet-killer could be downgraded to a civilization-killer or even a species-killer.

by mabbo 11y ago

iSnow 11y ago

Impact energy would rise with the cube of the diameter, I guess. So splitting up one large asteroid into a swarm of smaller ones is desirable. With any luck, some of the debris would even miss. The bigger problem is that that kind of missile system can be easily weaponized (China and the US have successfully tested satellite killers and the USSR maybe too), so simply enhancing ICBMs for that without international oversight is problematic.

cocoablazing 11y ago
That relation is equivalent to conservation of mass, and wouldn't account for any energy losses. As the asteroid is fragmented, its total cross section rises, increasing energy deposition in the atmosphere, reducing available energy for ejecta. WRT to arms-control regimes: What's the difference between an asteroid-killing BM and an ICBM? Only the warhead count. START inspectors would count such a launcher toward the cap.

workitout 11y ago

The smaller pieces might still be big enough to survive atmospheric entry. Now instead of one problem, you have many. Deflection sounds like a great idea, hit it right and send it off to a safer orbit.

mabbo 11y ago
More problems that are smaller may be better overall. With more total surface area, the air would absorb more of the total energy coming at us. You don't want another K-T extinction event when you could just have three cities wiped out instead.
- workitout 11y ago
  If you can guarantee just three cities. Either way, not sure why I was downvoted for having an opinion on the matter. Also I'm wondering why HN moderators allow such downvoting which discourages well intended discussion and participation.

mapt 11y ago

You can use a nuke in multiple ways. As a deflector (launched years or decades from impact), you can nudge the impactor out of its present orbit by gently ablating one side from a distance; You can do this iteratively until the impactor's orbit changes enough to miss Earth. Decades is sufficient for some of the continuous-thrust alternatives, though, depending on scale. As a point defence weapon (launched weeks or months from impact), you can send the nuke in as close as possible and detonate in order to break up the body. Yes, this would cause lots of smaller impactors, but over some size ranges it's preferable because ablation is insufficient. If 99% of the smaller impactors miss Earth, we win... in some cases. Just breaking up a large impactor (at the very last minute, launched minutes or hours before impact) doesn't help so much if everything still hits Earth, because a planet-killer turns into hundreds of city-killers randomly spread out. On the other hand, a small impactor could be dramatically affected by a nuke, with plausible amounts of vaporization going on. There's quite a lot of risk surface in small impactors, and they would be hard to spot until very close. --- Bong Wie is working through a NIAC grant on the problem: http://www.spacesafetymagazine.com/space-hazards/asteroid-hitting-earth/innovative-hypervelocity-nuclear-interceptor-spacecraft-mitigating-impact-threat-asteroids/ http://www.spacesafetymagazine.com/space-hazards/asteroid-hi... One interim observation: a nuke which detaches from a small cratering round which hits first, digging a hole for the nuke to fit in, would multiply its effectiveness severalfold. It's a very different problem in each different size class of impactor (as well as orbital classes). 10m, 100m, 1000m, 10000m are all of concern in unique ways; each order of magnitude increase in diameter raises mass by three orders of magnitude.

gherkin0 11y ago
> Just breaking it up (at the very last minute, launched minutes or hours before impact) doesn't help so much if everything still hits Earth, because a planet-killer turns into hundreds of city-killers randomly spread out. Wouldn't smaller objects burn up a greater proportion of their mass in the atmosphere (due to the increase surface area) and kick up less of a dust cloud once they impact? Could hundreds of city-killers leave some areas unscathed and still populated and habitable? I think it would be a great help if a planet-killer could be downgraded to a civilization-killer or even a species-killer.