It sounds like the script for a Hollywood film: a giant meteorite from outer space heading straight for the Earth and threatening the destruction of mankind.
Researchers say we can expect an asteroid to collide with Earth every few hundred years. The European research project NEOShield was set up to protect our planet from just such a catastrophe, with teams of researchers working to develop concepts designed to help avert these sorts of impacts and to alter asteroids’ orbits as they race toward Earth. Research scientists from Fraunhofer EMI in Freiburg are among those contributing to the work on the asteroid impact avoidance system.
»One solution would be to launch a relatively solid space probe designed to hit the asteroid at high speed,« says Professor Alan Harris from the German Aerospace Center’s Institute of Planetary Research as he explains the basic concept. »Asteroids are typically made of porous materials, so the first step is to build up a basic understanding of what happens when materials like that are hit by a foreign object,« says Dr. Frank Schäfer, head of the spacecraft technology group at Fraunhofer EMI.
To do this, he and his team use a light gas gun – one of the fastest accelerator facilities in the world. Within the gun’s approximately one-and-a-half-meter barrel, millimeter-sized pellets are accelerated to speeds of almost 10km per second. That equates to a speed of around 36,000 kilometers per hour.
The Fraunhofer scientists use what is known as a target chamber to bombard stone blocks used to approximate asteroids with a high-velocity mini projectile. The aim is to analyze with as much precision as possible how the material reacts. High-speed cameras document the experiment by taking up to 30,000 pictures per second. As in the crash testing of vehicles, the Fraunhofer researchers are interested in quantifying the force of the collision. Data are adjusted to account for actual scale and are imported continuously into computer simulations.
In the long term, NEOShield project leader Professor Harris would like to see the defense techniques that are the subject of this research tested in international space missions: »This kind of test mission is bound to throw up a few surprises, and will teach us a great deal.«
Incidentally, Harris reckons that averting an oncoming asteroid from its collision course by means of a huge explosion – just like in a Hollywood film – could in fact be an option in an emergency. Time would have to be pressing though, or the object concerned at least a kilometer in diameter.