The document says most asteroids entering the Earth’s atmosphere are small and burn up before reaching the surface. But it is the larger ones – perhaps 200m or more across – that would need to be deflected away from a collision course with the Earth.
The researchers propose several ways of doing this, the most extreme methods being to crash a spacecraft into the asteroid to knock it off course, or to set off a nuclear explosion. They say the earlier the threat is dealt with, the less drastic the course of action need be.
If protection against rogue asteroids is what it takes to fund lots of solar-system observation and exploration, what the heck. Science is full of useful information developed by people who mostly wanted to commit mayhem.
But as the computation and observation get better and better, it kinda makes you wonder when someone is going to try and use this kind of thing as a weapon. Quietly send out a mission, make a few adjustments, and darned if three or 30 years later your adversary’s capital city doesn’t get vaporized…