Asteroid 2011 AG5 Will Definitely Miss Earth

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Devoneaux:

So instead of nuclear force, why not just kinetic? Launch a massive object into space and use big giant rockets to rapidly propel the object at the meteorite?

Pretty much this. For an asteroid to impact the Earth it needs to pass through a narrow keyhole region. Ramming a satellite into it (as has been done before) early on would be enough to nudge it onto a safer trajectory. No need for explosives.

Devoneaux:

McMullen:

Devoneaux:

Would exploding the nuke in front of it be enough to alter it's course?

If not buried in the asteroid, it probably wouldn't make any measurable difference. The concussive force of a nuclear weapon is due to a rapidly expanding, because superheated, atmosphere. In space, there is no atmosphere, and so there is no concussive force, and all you get is a really bright light. This does actually generate force on the atmosphere, both through a phenomenon called radiation pressure (I'm not sure how it works, you'll need to ask a physicist or look it up), and also by vaporizing the upper millimeter or so of the asteroid's surface and causing it to expand. Still, this force is absurdly small compared to the kinetic energy of the asteroid.

You might actually alter the trajectory of the rock with a strategically placed subsurface detonation or maybe even a surface detonation, which would vaporize a bigger portion of the surface near ground zero, and the expanding vapor would act like a short-lived rocket engine. However, if it's already on its final approach towards Earth, the rock may not be deflected enough. An attempt at deflection would have to be made early, and where it might end up later on would be uncertain. Suppose for example the asteroid is expected to splash down in the Pacific. Would it be better to let it hit the ocean, or try a deflection attempt and risk diverting it not to space, but to a densely populated continent? Who makes that decision, and who answers for the billions of lives lost if a mistake is made?

That Hyena Bloke:

Devoneaux:

Would exploding the nuke in front of it be enough to alter it's course?

For a 140m long asteroid? Maybe, but keep in mind that nukes behave differently in space and they really aren't designed for this sort of thing. You also have to keep in mind that these objects aren't just floating along, they're being pulled by gravity. It might be better for us to invent a new type of weapon designed specifically for deflecting near earth objects, I believe there's currently a lot of research going on about that.

So instead of nuclear force, why not just kinetic? Launch a massive object into space and use big giant rockets to rapidly propel the object at the meteorite?

You should submit this line of questions to What If at xkcd. I'd like to see a quantitative treatment of it.

The best current plan I've heard of does involve a kinetic impactor, perhaps in combination with a precisely timed nuclear detonation. The problem is that asteroids are dangerous because they already carry kinetic energy in amounts that can exceed the combined yield of the world's nuclear stockpiles. The energy of the deflecting impactor would have to be enormous in order to significantly alter the rock's course, and it would have to come from fuel, or the gravity of other planets. The rocket would have to be huge, since the more fuel you take, the more you have to burn to lift it.

It's possible, if you do it early enough, but pulling it off would be very difficult.

at 450 feet its not even worth worrying about, with our luck it will probably just explode in the atmosphere giving some near by town a pebble shower

2fish:
Well the Mayan calendar was all about the end of the world ...I mean it was all over the news how could you miss it? :P

People interpreted it as the end of the world. That does not mean it was about the end of the world.

Devoneaux:
So instead of nuclear force, why not just kinetic? Launch a massive object into space and use big giant rockets to rapidly propel the object at the meteorite?

You're on the right track, but depending on the size of the object and the speed, it would have considerable kinetic energy in of itself. For a safe deviation given a reasonable intercept point (remember, that we can locate an object FAR sooner than we can reach it) would either require a very large object (which is difficult o get out of the atmosphere) and or traveling at a relatively high rate of speed.

You do have the right idea, it's just the capability to do it accurately and with a large enough margin isn't terribly practical given current tech.

When all else fails, go to Neil DeGrasse Tyson.

The whole interview is magnificent, but skip to 50:00 for the Apophis question.

DaxStrife:
Pardon me, but:
"Asteroid 2011 AG5 Will Definitely Miss Earth"
...then just below that:
"[sic] ...has a lower chance of hitting earth."

You do know those are two separate things right? "No chance" isn't the same as "lower chance."

I was gonna say... Looks like ya beat me to it.

I guess 28 years away isn't too bad even if it does hit the Earth. As some have said, it isn't likely it would cause global extinction and technology has improved drastically over the last 20 years so a future 20+ years of progress could lead to some form of salvation being created. Even if all else does fail and the world is screwed, I'll be in my 40's at that time so I'd have reached the point in my life where things get a little repetitive and I'd be able to say I'd have had a life well lived, so no biggie.

Callex:
Ramming a satellite into it (as has been done before) early on would be enough to nudge it onto a safer trajectory. No need for explosives.

Wait, what? When did this happen?

iblis666:
at 450 feet its not even worth worrying about, with our luck it will probably just explode in the atmosphere giving some near by town a pebble shower

Air bursts can actually be very dangerous! Because of the kinetic energy an asteroid this big would have, it would go off like a nuclear weapon. Back in the early 1900's a 300ft meteor was believed to have exploded over Russia in what is known as the Tunguska Event - flattening 2000 square kilometres of forest!

McMullen:

Wait, what? When did this happen?

It was done in 2005 by the aptly named 'Deep Impact' satellite. They smashed a mass into a comet to analyse the material in its interior. While it was only a small payload, it still slightly altered the comet's momentum. You'd need to scale it up a fair amount, but we certainly have the technology to put an object on a collision course with an asteroid.

http://en.wikipedia.org/wiki/Deep_Impact_(spacecraft)

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