SPACE.com -- New Cosmic Defense Idea: Fight Asteroids with Asteroids: " New Cosmic Defense Idea: Fight Asteroids with Asteroids

By Robert Roy Britt
Senior Science Writer
posted: 20 June 2006
06:06 am ET


In a Space Age version of fighting fire with fire, French scientists have suggested using one asteroid to destroy another rather than letting Earth get pummeled.
The offbeat plan is intentionally incomplete and would allow the planet to be showered by fragments. But it might be better than a civilization-ending whack.
No asteroids are presently known to be on collision courses with Earth. But existing holes in the ground suggest that inevitably one will eventually be found. There is no firm plan for how to deflect or destroy an incoming asteroid, though scientists have pondered firing rockets at them, moving them gently with solar sails, or nudging them with nuclear explosions.
Lock and load
The new idea is to capture a relatively small asteroid�perhaps 100 feet (30 meters) wide�by sending a robot to it.

Lagrange points exist in any two-body system. Find out how they work.


The robot would heave material from the asteroid's surface into space, and the reaction force would gradually direct the asteroid to a Lagrange point, one of a handful of nodes along Earth's orbit where the gravity of Earth and the Sun balance out. Scientists know that objects can be kept stable at a Lagrange point with little or no energy.
The captured rocky weapon would be held there, traveling around the Sun ahead of or behind the Earth, held until needed.
Then, if a large asteroid threatens to hit us, the small one is moved into its path, using the same heaving technique. The rocks collide, and the big one is broken into somewhat less harmfull bits.
The collision disperses"