WetGeek It's comforting to believe that nothing large is expected to hit Earth for 100 years, and let's hope the researchers are right about that.
NASA believes that we have identified about 50% of the NEO's large enough to have a significant impact, say cause damage on the level of the Tunguska event. NASA doesn't track smaller meteors like the one that caused the Arizona crater, and 50% isn't 100%, but it beats a blank,
WetGeek In 100 years, we'll probably have moved this process beyond a proof of concept.
NASA is looking at a number of different tools.
Kinetic deflection is the idea of deflecting a moving curling stone with a fast BB. In theory it will work, because even a miniscule change in the target asteroid's orbit will mean that it will be a flyby rather than a hit. But as we all know from wasting our youth in pool halls, angles are hard to predict and to execute.
Kinetic deflection is not designed to deal with large NEO's, like the one that wiped out the dinosaurs, estimated at about 7.5 miles in diameter. No way could be launch anything heavy enough to deflect an NEO that large. NASA is looking at other tools (using nuclear weapons or landing something with an engine, for example) for the large NEO's.
Whether any of it will work is anybody's guess, but NEO's are hardly the greatest threat to the planet. Humans are as likely as not to have rendered the earth uninhabitable long before an NEO gets us.