They're the same thing.
No they aren't.
The more stages you have, the worse the instabilities become. 3 stages is doable, but any more than that? Seriously questionable.
Three is more than sufficient to undermine your proof of concept "not enough fissiles" declaration.
Is that seriously an objection? Why on earth does it have to be accelerated across the Earth's surface? You're being really lazy here in not even thinking of any alternatives.
What the? Don't be absurd. "Bomb on the planet's surface." was exactly the problem specification. If I wanted to destroy the earth I would obviously not try to do so with a bomb on the planet's surface.
No they aren't.
Any interstellar method is a fortiori a terrestrial method as well.
Three is more than sufficient to undermine your proof of concept "not enough fissiles" declaration.
In what respect? The Tsar Bomba gives us an estimate on what the third state buys one, let's be generous roughly an order of magnitude (6mt to 60mt). The analysis I linked concluded that the existing nuclear stockpile was at least 100x too small to power an Orion, so a 10x increase is useful but not enough (and where's the plutonium for 65k stage threes coming f...
http://neo.jpl.nasa.gov/risk/2012da14.html
http://rt.com/news/paint-asteroid-earth-nasa-767/
Seems like a good opportunity to bring up existential risks. And A friendly reminder that NASA is in fact pretty damned important.
Thoughts?