How to save the Earth from asteroid Armageddon (Bruce Willis optional)
Despite the lack of a current threat, there are a number of techniques for impact mitigation that have been proposed. Some are ingenious while others are more than a little impractical! NASA’s verdict is that our only feasible option at the moment would be to nuke the asteroid. Here’s the lowdown on some of the more interesting techniques that have been proposed.
Use a ‘tractor beam’:
A ‘gravity tractor’ is a spacecraft that positions itself near to an asteroid to create a constant gravitational force upon it in an attempt to change the asteroid’s orbit, and so avert disaster. Termed a ’slow-push-pull gravity tractor’, it could be very effective for small asteroids that are decades away from impact. However, this method is impractical because it needs a mission lead time of over ten years.
Hit it really hard:
The ‘kinetic impact’ strategy crashes an enormous spaceship into the asteroid at colossal speed (over 11,000 miles per hour!) Such an impact should change the asteroid’s velocity and orbit and so save the world. Kinetic impact could protect the Earth from moderately sized asteroids (several hundred metres to 1km in diameter). The kinetic method is relatively robust, and has even been tested in space as part of NASA’s deep impact mission in 2006. However, hitting small asteroids at high speed could be rather tricky and a warning time of forty years would be needed to deflect an asteroid of 1km diameter.
Nuclear explosions have been proposed to eliminate asteroid threats by destruction or by knocking it off course. A ‘standoff’ or ‘impact burst’ would heat the asteroid’s surface on one side, forcing it to travel in the opposite direction. This is the preferred nuclear method, as there would be no need to fly alongside the asteroid at a low speed and the asteroid’s composition doesn’t matter. Alternatively, a surface or near-surface explosion could be attempted, but it would be technically more difficult to hit an asteroid dead-on. However, this could be the only means to prevent an impact from a large asteroid (greater than 1km in diameter).