Fraunhofer studies probe impacts to deflect asteroids

There are hundreds of near-Earth asteroids hurtling through space that are a potential danger to our planet. One way of dealing with the problem is to deflect them with a space probe deliberately set on a collision course.
To see how effective such a collision would be, Frank Schäfer of the Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach-Institut, EMI in Freiburg, Germany is looking at what asteroids are made of and how this affects a deflection impact.
It may seem odd to use a space probe the size of a washing machine to fend off an asteroid that weighs in at a couple of hundred tons, but then, a few ounces of lead are enough to bring down an elephant. It’s a matter of putting enough energy behind the bullet. In this case, the bullet is a spacecraft, but even moving at orbital velocity the effect wouldn’t do much to an asteroid large enough to pose a danger to Earth. However, it doesn’t have to, if the impact is properly timed.
“In actual fact, the impact of a space probe would change the speed of the asteroid by just a few centimeters per second. But that’s enough to deflect its course to a significant degree over a longer period. So if we want to stop an asteroid on collision course with the Earth from hitting us, we’ll need to fire at it many years ahead of time,” says Schäfer.