spacetoday.net: "Gravity tractor" could deflect asteroids

Posted: Sat, Nov 12, 2005, 9:29 AM ET (1429 GMT)
Gravity tractor illustration (D. Durda/B612 Foundation)

The miniscule but sustained gravitational attraction between a spacecraft and an asteroid could be sufficient over time to deflect that asteroid from an Earth-threatening trajectory, according to research by two NASA astronauts. In a paper published in the current issue of the journal Nature, astronauts Ed Lu and Stanley Love described how a 20-ton spacecraft, hovering over the surface of an asteroid, would gradually deflect the asteroid's trajectory over time because of the faint gravitational force imparted on the asteroid by the spacecraft. Such a system could deflect a 200-meter asteroid from an Earth-crossing trajectory in about a year, provided there was advance warning of about 20 years. This approach is considered better than attempting to use nuclear weapons to deflect asteroids, as recent research has indicated that many asteroids may be loosely-bound agglomerations of rock, and could shatter from the force of an explosion.