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More than the threat of nuclear war, we should worry more about asteroids destroying the Earth. For the first time we could save ourselves from that happening.

Take all the nuclear missiles of the world and modify them for interstellar travel. How big and how close approximately could we move an asteroid to save the Earth?

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    $\begingroup$ Are you absolutely sure you mean 'interstellar'? Most large object passing near Earth are from within our own solar system. $\endgroup$ – user535733 Feb 13 '18 at 18:58
  • $\begingroup$ @user535733 What word would you use? It would be good to meet anything inside or outside our solar system that threatens Earth. $\endgroup$ – Muze the good Troll. Feb 13 '18 at 19:01
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    $\begingroup$ I think you need to ask the question of if a nuke can even move an asteroid. Actually I think we have. worldbuilding.stackexchange.com/questions/46452/… sound right? $\endgroup$ – Twelfth Feb 13 '18 at 19:01
  • $\begingroup$ @Muze - There's a lot of scenario's that could come about here and you'll need to set some definitions. A solid iron asteroid will hold up better and I suspect move a bit more, but there's a decent chance you'll start it rapidly spinning instead of altering course. If it's a gravel asteroid (IE not solid) then there are other considerations. Define asteroid in your question. Second portion...history.nasa.gov/conghand/nuclear.htm we are not entirely sure what a nuke in space actually does outside of knowing its far different than a nuke in an atmosphere $\endgroup$ – Twelfth Feb 13 '18 at 19:09
  • $\begingroup$ @Twelfth feel free to edit it to be a better question. I will grateful for the help. With 15,000 nuclear missiles we could have many scenarios. $\endgroup$ – Muze the good Troll. Feb 13 '18 at 19:15
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I'm still not 100% sure on whether or not a nuke in space would actually move an asteroid. It would definitely irradiate it, but would it move it?

The basis of my assertion is from this link here https://history.nasa.gov/conghand/nuclear.htm

When a nuclear weapon is detonated close to the Earth's surface the density of the air is sufficient to attenuate nuclear radiation (neutrons and gamma rays) to such a degree that the effects of these radiations are generally less important than the effects of blast and thermal radiation.

Short version is the blast and thermal (heat) released in an atmosphere is due to the presence of an atmosphere...the radiation of the blast interacts with the air and causes the extreme heat and concussive wave. Guess what doesn't exist in space?

If a nuclear weapon is exploded in a vacuum-i. e., in space-the complexion of weapon effects changes drastically:

First, in the absence of an atmosphere, blast disappears completely.

Second, thermal radiation, as usually defined, also disappears. There is no longer any air for the blast wave to heat and much higher frequency radiation is emitted from the weapon itself.

This is to say that a nuke in space generates a huge amount of radiation, but no concussive blast or heat (these 2 aspects are because of the nuke's interaction with the atmosphere). No atmosphere, no blast, no effects outside of extreme radiation. Potential that the radiation is enough energy to move the asteroid?...but our information on the subject is lacking and I believe is likely orders of magnitude less than the energy required to divert the asteroid.

As a side note - Gravity is likely the best method of moving these asteroids. Since the distance/time is so great, simply shadowing the asteroid with a large mass (a transport ship) might be enough to redirect the asteroid. Transport and asteroid interact (gravity) bring the two close together. Transport ship uses thrusters at an angle to move itself further away from the asteroid...repeat this for 50 years and the impact on the asteroids trajectory is significant.

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  • $\begingroup$ I did not know this. Can't say I ever wrote a nuke exploding in space before, but the idea that it won't actually explode in a vacuum never occurred to me. Thanks for saving me from the embarrassment going forward. $\endgroup$ – OhkaBaka Feb 13 '18 at 22:22
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    $\begingroup$ @OhkaBaka - there's another question on world building that answers a nuke in space detonation well. Short form is it's a single flash (strobe light that flashes once?)...however it's all high frequency waves (gamma ray range if I recall correctly) so it fries most things capable of detecting the flash without some heavy radiation shielding. $\endgroup$ – Twelfth Feb 13 '18 at 22:51
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To begin with, you would have to assume that the asteroid would be indestructible if it was to be hit with the concussive blast of a nuclear warhead. It would also have a different effect in space than on earth. With no elements or chemicals to fuel, an explosive reaction with, at the very least would not produce anything more than just radiation. However, if you did get a planet-sized asteroid that did not feel the effects of gravity, nor was it in orbit to anything, then if you applied the force of a nuclear bomb to a side of this planet-sized asteroid you could potentially move it. However, you would have to add the necessary elements to the reaction to cause a blast or figure out some other way to simulate this reaction.

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