More on deflecting asteroids

Copied from an article in the New York Times.

By LIA MILLER
Published: December 9, 2007

In 1908, an asteroid is thought to have entered the earth’s atmosphere and exploded over a Siberian forest, leveling some 800 square miles of trees in what is known as the Tunguska Event. If we knew today that another asteroid were on a path to intersect with our planet, what could we do?

Massimiliano Vasile, a lecturer in aerospace engineering at the University of Glasgow, recently concluded a two-year study comparing nine asteroid-deflection methods, rating them for efficiency, complexity and launch readiness.

The best method, called “mirror bees,” entails sending a group of small satellites equipped with mirrors 30 to 100 feet wide into space to “swarm” around an asteroid and trail it, Vasile explains. The mirrors would be tilted to reflect sunlight onto the asteroid, vaporizing one spot and releasing a stream of gases that would slowly move it off course. Vasile says this method is especially appealing because it could be scaled easily: 25 to 5,000 satellites could be used, depending on the size of the rock.

The losing ideas — satellites equipped with lasers; detonating a nuclear explosion; pushing the asteroid with a spacecraft, to name a few — might still have their place. Vasile says improved technologies could make others appealing in the future. (In March, NASA released a report on “near Earth objects” that deemed the nuclear-explosion method the most effective.)
Michael Gaffey, professor of space studies at the University of North Dakota, says the risk of dying from an asteroid strike is about 1 in 2 million. The problem is that the consequences are tremendous; a half-mile-wide asteroid or larger, of which there are more than 700 that come close to Earth’s orbit, could have an impact equal to 60 billion tons of TNT. While it is not likely to happen, you still want to be prepared. “You don’t panic, you don’t have to run around screaming and waving your hands,” Gaffey says. “But you do need to devote resources to it.