Nuclear Detonation In Space

[10fingers]

I'm sure you have all seen the various shows about how we would try to ward off an impending collision of the Earth with a meteorite/comet. In some of these scenarios they propose hitting it with a nuclear weapon to either destroy it or knock it off course.
I was just thinking about this and it occurred to me that most of a nuclear weapons blasts effects are caused by the superheating of the atmosphere with the resulting expansion and shock wave. Well, in space you have no atmosphere so I would think that the effects of a nuclear blast would be greatly minimized. So how are you going to move it? It seems to me that the only thing you would do is warm the thing up a bit.
In the movie Armageddon (totally inane movie),they placed the nukes below the surface which would have more of an effect but I think in reality would be totally impossible.

[Hirudinea]

If you exploded the nuke of the surface of the rock the energy from the explosion and the "kick" from the ejection of vapourized rock would cause a change in the rocks course (or smash it apart), or at lease I think it would, mabye we can ask the USAF if we can borrow a couple Minutemen and give it a try? :D

[Frunk]

A nuke in space would cause an EM radiation burst, from gamma rays to infrared.
It would be a fart in the wind compared to the radiation output of the sun and probably wouldn't harm the Earth.

If detonated on an asteroid, it could vaporize parts of the rock, but shockwaves can't propagate in vacuum. The asteroid would be somewhat deflected due to conservation of energy.

[Skean Dhu]

There is also nothing on the otherside of the bomb, what I mean is when it explodes on the surface of the asteroid there is zero tamping, not even air to provide minimal resistance. So nearly all of the effects are going to be bounced off of the object rather than projected through it.

At the very least a nuclear bunker-buster would have to be used in order to get a respectable result.

[Ygarl]

Unfortunately, there is a more serious problem.

Some sources theorise that the energy to move a Carbonaceous Chondrite-style or icy body (i.e. comet) via nuclear explosion may instead fracture the bodies. Even more alarmingly, several imaged asteroids have turned out to be binary, trinary, or even just heaps of rubble gravitationally attracted to each other.

I don't need to spell out the effects of sending a nuke to an asteroid to change its course, only to find that it's 2 or 3 or 100 bodies in close contact...

Some may not realise that breaking a mid-sized asteroid into 2 parts is actually more dangerous than having it in one part. The effects of one 2 kilometre asteroid vs. two 1 kilometre asteroids (or even worse - five 400 meter ones!) is far worse locally and regionally and is just as bad globally overall.

A 1km asteroid would cause over 15psi overpressure 100 miles away, and heat effects capable of igniting grass! Having 2 some 100 km apart doesn't bear thinking about. It is roughly equal to a 60000 MEGAton bomb. Almost as scary - a 180m one like one found last week would impact with the effect of a 300 megaton bomb.

Kinda makes ANFO and Nitro look pathetic...

While using nukes to change the course of an asteroid is theoretically possible, it would have to be very carefully checked out beforehand. Turning a 3km asteroid into - say - a pile of 35 1km asteroids separated in space over 400 or 500 km in space is definitely not a good idea. That would be the equivalent of dropping a 60Gigaton bomb every 10 or 15 km every 2 seconds for 2 minutes in a chain 500km long.... approximately the size of the entire UK from north to south, or the entire Eastern Seaboard.

Perhaps an ion rocket engine which would run for several weeks, or a solar sail would be a better idea. These are some ideas being currently considered if needed.

Armageddon was ridiculous as a scientific movie. Deep Impact was far better, and had a better story anyway. At least it was vaguely realistic...

[Hirudinea]

If you want to look more into using a nuke to move an astroid you could look up "Project Orion" on Wikipedia, it was an idea to use nuclear bombs to drive a spacecraft through space, in theory it could get the ship up to 2% the speed of light (and it was a big friggin' ship), the project was well researched so I'm sure some of the principles could be applied to diverting an astroid.

[Gerbil]

On a sidenote, an improved design of Orion, Project Daedalus, would theoretically have reached 12% of light speed:

http://en.wikipedia.org/wiki/Project_Daedalus

[shooter3]

Using a grid patern covering one face of the asteroid, 150feet from the surface, (maybe on poles?), fired at the same time, would cause some ablation of the surface. Being uniform over the whole face would impart some acceleration in that direction. Even if the asteroid broke up, the material would be pushed out of the way (assuming it was aimed correctly). Solar sails may work and the orbiting mas idea may also, but this is the FORUM!!! I want to blast it out of the sky!!

[in_flames]

I think the main problem of nuke-ing an asteroid would be that fact that the asteroid is now radioactive so anything that still hits would send fine radioactive dust everywhere on impact.

[Hirudinea]

On a sidenote, an improved design of Orion, Project Daedalus, would theoretically have reached 12% of light speed

Yea I know, but the nice thing about Orion is that we have the technology this very minute to build it, Daedalus would require some advances in fusion technology.

[Jacks Complete]

I doubt the tiny amount of radioactivity would mean much after it was buried in the mantle by the flying rocks. Heck, it's plenty warm down there due to radioactivity anyway!

The best thing to do would be a giant net or something akin to a solar sail. Simply wrap it in that to keep it together, then allow the change in momentum of the sunlight hitting it to push it onto a different course. Failing that, a powerful rocket backed up by an ion drive (or even a neat trick with an ion drive that lasered or ion beamed the surface and used the rock itself as propellant) would shift it just fine.

You would want to slow it as far as possible, so it falls into the sun.

If we had really, really good telescopes that could pick out comets and big rocks on funny trajectories in other solar systems, we could seek intelligent life easily. A total absence of these bodies would indicate that the species there had decided to sweep house to avoid losing a planet worth of people.

As it is, we don't even spot half the risks until they are past us!