[maxerickson]

I'm assuming that the first notice of the asteroid changing trajectory will be well before the trajectory is Washington DC. So presumably there is something changing the trajectory. Vaporize that thing. Now the trajectory is not Washington DC and the threat is empty.

[jessaustin]

How about this scenario? There is an asteroid in the solar system we've already directed on such a trajectory. Using the thrust capability that we installed to accomplish that, we're happy to redirect the asteroid, if our demands are met.