Re: Throwing theories gets us there
> As for lead time NASA claims it needs 5yrs
Well, remove at least one year for the solution to actually work (slowly deflecting the asteroid), that gives us just about the time to build rockets able to go beyond our moon's orbit (probably more than a couple of them), and whip out an untested prototype.
Problem is, most ideas about deflecting an asteroid are pretty complicated, requiring technology we've never even tried before: Paint an asteroid? How do you paint in vacuum a gravity-less surface covered in gravel and dust? Most certainly requires some new and unheard-of technology? Mass driver? Sure, how many functioning at that scale have we ever built so far, and I'm not even going to go into the problems of installing and operating one on a distant asteroid. It would take some trial and error, and that's only after we have sent a probe to examine the offending asteroid thoroughly, and gathered a perfectly clear understanding of what it is made of and how it is internally structured (which might take most of a year all on itself).
My point is if we had already managed to do a successful test run on some random asteroid, we could pretend we might potentially be able to repeat that feat in case of emergency. But right now the chances of success are slim, at best: New experimental, untried technology, fixed, very short deadlines, everything happening (hopefully) very far from earth, there is really nothing helping us here...