[phh]

Thanks that's interesting. The article says 0.5mm/s of change is enough to miss the earth, but how much time ahead do we need to find the asteroid? (Assuming we launch the day we find the asteroid, which is politically-wise unlikely but well)

[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?