[icegreentea2]

So with an end-stage interaction where you're not considering keyhole effects, you very roughly you need to accumulate an Earth diameter of position change. So Earth diameter is ~13000km, so that works out 26 billion seconds or 825 years.

So in real terms, we'd probably wanna do a but more delta V than that. At 1cm/s, you're down to 41 years for example.

[peteradio]

Doesn't this assume the asteroid is dead center targeting earth?

[lovecg]

Good point! Assuming that the asteroid sees Earth as a disk that it can hit anywhere uniformly at random and also that I can still do calculus in my head, looks like the expected radius away from the circumference is only 1/3 R?