Asteroid fallout

I'm working on a longer post that will take a few more days (and am considering doing more of that in the future); in the meantime the fallout from the asteroid in Russia is quite interesting to watch. This article from the Economist, while very wrong in places, is a good example of the slight change we may begin to see in our view of space: not just a place to explore but also a place to defend against. It is, of course, very correct in this statement:

The real problem is “city-killers”—things too small for existing surveys to see, but large enough to do serious damage.

Where it is not quite so correct:

Two things would be needed. One is a bigger system of telescopes, either on the ground or in orbit, to give notice of a threat.

More on the ground or in orbit is fine and quite helpful, but what would truly help against these is something like the proposed Sentinel mission that would be able to see asteroids as they approach us from the direction of the sun.

Also where it is not quite so correct:

Developing all this would be a technological challenge worthy of NASA’s engineers. It would keep the agency’s bureaucrats in their jobs. It would keep the money flowing to the aerospace companies. It would probably cost no more than the space station (about $100 billion).

Perhaps in theory we might need to spend billions to protect us from asteroids, but since detecting them the most important goal we can do that for hundreds of millions instead of billions. Chances are an asteroid would land in an uninhabited or sparsely inhabited area, and with a few months' or weeks' warning it would be easy enough to plan a temporary evacuation, much easier done than destroying an asteroid. Since we are only talking about city-killers, the only time it would truly matter would be when one is heading for a truly large city. Otherwise, a quick scattering to the hills after battening down the hatches followed by a return for repairs is all we would need.