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# Physics/Saturn carried nuke to destroy an asteroid

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Question
Hi! I read that a 700 megaton fusion bomb could be the maximum a Saturn rocket could carry to orbit. So my question is that would 700 megatons be enough to destroy these four asteroids assuming the nuke makes a direct hit?
1. The Apophis asteroid.
2. 1 kilometer iron asteroid
3. 1 kilometer rock asteroid (density of 3 tons per m^3)
4. The ''dinokiller'' asteroid

Answer
A 700 MT bomb has never been made.  Not something even 10% of that capability has.  However, I have no idea where you got that number...there are so many factors affecting nuclear weapon design that if anyone tells you the maximum size weapon that a Saturn rocket could carry then they're absolutely making the number up.

First, you would never bother with destroying these asteroids.  That would break them into pieces, some of which might still hit the Earth, assuming that you're writing yourself a Hollywood movie script on par with "Armageddon."  (I liked the drama in the movie, and took the science to be about on par with "The Avengers.")  You would steer them away from their trajectory just a tiny fraction of a tiny bit, and they'd fly right by.  The Earth is going at 30 km PER SECOND.  At that speed the Earth travels its own diameter in just 3.5 minutes.  The distances of asteroid trajectories are also huge, so just a tiny nudge in speed and/or angle would do it.  But given that a weapon of the size you mention has enough energy to deposit about 2 Joules per gram to the ENTIRE asteroid in even the biggest case (the last one) and the violently focused nature of a nuclear weapon, it definitely has enough energy and the punch to fragment even that monster into pieces.  Of course, if you're in a movie and your asteroid is "the size of Texas," then it won't work.  But at that energy it would be able to (conservatively applying factors for momentum change) impart enough velocity change that you'd only need to get your bomb out to about 15 lunar distances to slow the asteroid down enough to miss entirely.  Since most of that stuff of that size is known (and the smaller ones, no question, way easier), you could knock it off its orbit during a close pass years in advance.   Especially Apophis, it's nowhere near the size of the others, and we know its orbit well.

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#### Dr. Stephen O. Nelson

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I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.

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I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

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Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.

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