Talk about timing. Just hours before a small asteroid exploded above Russia last February, two California universities issued a press release proposing a way to deflect or destroy such rocky invaders long before they reach Earth: Zap them with a giant ray-gun.
Scientists have toyed with several ideas for deflecting killer asteroids: blasting them with nuclear bombs, attaching rocket engines to them, using a nearby spacecraft as a "gravitational tug," and even painting sections white or black to change the way they reflect solar energy.
DE-STAR (Directed Energy System for Targeting of Asteroids and exploRation) is the latest entry in the field. It would use lasers in Earth orbit to vaporize or deflect asteroids while they’re still tens of millions of miles away.
“We looked at a modest worst-case scenario,” says University of California-Santa Barbara physicist Philip Lubin, one of the two project leaders. “We picked a 500-meter asteroid moving at 30 kilometers per second because if it hit us, it could cause massive destruction. With a year’s warning, we wanted to be able to completely vaporize the asteroid. That was our challenge.”
To meet that goal, Lubin and Gary Hughes of California Polytechnic State University in San Luis Obispo designed a system that would use an array of solar-powered lasers several miles across to deliver a concentrated beam of energy to a small spot on an asteroid’s surface, heating it to about 6,000 degrees Fahrenheit. With enough lead time, that could obliterate the entire asteroid.
You wouldn’t even need to destroy the asteroid completely to protect Earth from harm, Lubin says. Vaporized rock spewing into space would act like a powerful rocket engine, pushing the asteroid to a safe course.
While the full-scale planetary defense system would be far larger than anything ever built in space before, it could start with something smaller than the sail on a tallship. “Even with a 10-meter system, you could take down space debris pretty effectively,” says Lubin. And a system the size of a couple of football fields could nudge most asteroids into new orbits.
Because a DE-STAR unit would be wide but thin, like a thick tarp, it could be folded to fit in a standard rocket payload fairing. Much of the development work would be in devising techniques to assemble multiple modules in orbit, align them with the Sun, and maintain precise pointing as they track an incoming asteroid.
The system would not, however, require major advances in laser technology, Lubin says. Lasers already tested in the laboratory could provide adequate performance today, and both power output and cost are expected to improve in the next few years. “It wouldn’t require any fundamental breakthroughs,” Lubin says. “It would be hard to do, but we could do it.” With enough funding, he estimates, a small system could be deployed in a few years, and a football field-size array could be operating in a decade-and-a-half, offering some protection from all but the biggest asteroids.