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Comment by dr_zoidberg | Hacker News Reader

You're not wrong. Possibly the biggest issue would be how can you quickly launch one of these without triggering WW3.

Another issue I'm thinking is that I don't know the state of the art of meteor/bolide trajectory estimation (it's apparently very poor), so you'd probably need to fire a bunch of these (or a very large one) along an (uncertain) path hoping for it to affect the impactor.

So this is just more of the same problem: how do you fire a barrage of nuclear missiles over a region to stop an impactor in such a way that you're not mistaken for a madman starting nuclear war?

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This discussion is all wrong - nuking an approaching asteroid is like shooting an approaching freight train - it's too late to stop.

The asteroid needs to be pushed with a nuke, or another method, while it's still in deep space, months or years before it would strike. It would be many times beyong the orbit of the moon, millions of kilometers.

ICBMs are for ground targets, their "reach" is a thousand kilometers or so, they have no navigation or tsrgeting for space.

Instead a spacecraft like Rosetta would to be equipped with a nuke and launched on a normal space rocket like Falcon 9 or Ariane or Soyuz. We only need to produce a couple of them in case of launch failure, we don't need thousands of them like we have ICBMs. The launch would not look anything like an ICBM launch, it does not come back to earth.

It depends on the asteroid size.

Afik, there's a very abrupt limit on the size of an asteroid where if it's larger it will "touch" the ground and if it's smaller, it airbursts.

So if we could split the asteroid in 10, maybe we go from "completely destroy everything within a 100 miles radius" to 10 Chelyabinsk events.

For asteroids that can be detected with lots of time, yes, deflecting them with time is totally the way to go. As the discussion was with bolides, I assumed we were talking in an "impending danger, no time to act" framework.

In this context 'Lost of time' means years in advance, so you can finetune it's orbit.

'Impeding danger' means weeks or days at a minimum, so you have to use a nuke. It would be near moon's orbit.

If it's a bolide, it's in the atmosphere, moving faster than any missile. Its like trying to stop a bullet after it intered you epidemis - you already lost.

I understand that bolides would be the biggest danger right now, as they are small enough to be practically undetectable, but may be large enough to level a city. Are there any measures we can take against them? [0]

[0] I'm aware one of our best bets here would be a proper survey and sensitive enough telescopes/satellites actively looking for these kind of objects. And that there are some projects and programs along these lines already. It'd seem there's some more work to be done in that area though.

Yeah that's a real problem, or several. Not even sure which would be the hardest to solve...

Am I wrong to wonder if a nuke would even do it either? I mean it's a ~solid rock that's capaple of surviving a pretty good beating from the atmosphere. What's a nuke going to do exactly? Are we hoping for redirection, or destruction or?

As I understand it, redirection is our best hope. Destruction via nukes would only work for comparatively small rocks. There is a fairly comprehensive write-up of the various options on Wikipedia:

https://en.wikipedia.org/wiki/Asteroid_impact_avoidance

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