November 9, 2005

“Gravity Tractors” could outwit killer asteroids

By Paul Majendie

LONDON (Reuters) - No need to send Bruce Willis into space
with a nuclear bomb -- the best way to deal with a killer
asteroid hurtling toward Earth could be a "gravity tractor."

Two NASA astronauts, gently mocking the solution offered in
the Hollywood blockbuster "Armageddon," have come up with a
deceptively simple plan to pull asteroids off course.

Edward Lu and Stanley Love have proposed that a rocket be
launched into space, effectively to act as a giant magnet.

Landing on an asteroid, which is no more than a spinning
pile of rubble, is very difficult to achieve.

Instead, the gravity tractor would travel alongside the
asteroid and gradually pull it off course, using nothing more
than the gravitational pull between the two bodies.

"This saves you from having to land on the asteroid and
then trying to stabilize yourself on a flying pile of rock and
debris which is spinning all the time," Love told Reuters after
their plan was published on Wednesday in the science journal

Lu and Love calculated that, with sufficient warning, a
20-ton gravity tractor could safely deflect an asteroid 200
meters across in about a year of towing.

"By using gravity as your tow line, you can sidle up to an
asteroid. Maintain it for a year and that should give it enough
nudge to miss the earth 20 years later," Love added.

The clock is ticking on the chance to put their plan into

An asteroid is due to pass close to earth on Friday, April
13, 2029. But the chances of impact are put at comfortingly
long odds of 5,560 to one.

"We know enough about this asteroid to know it is a
potential threat but we still have a few more years to watch
this thing and get a better handle on what it is going to do,"
Love said.

"No panic. I am not losing any sleep over it. But we have
to make a decision by 2013 on whether we have to send a mission
to detect it," he added. "Detection and deflection go hand in

In the movie "Armageddon," a doomsday asteroid is on a
collision course with Earth and the only way to knock it off
course is to drill into its surface and detonate a nuclear

Bruce Willis springs to the rescue as the countdown begins
on life as we know it.

For Love, it was no more than an enjoyable night out.

"It is a great movie and a lot of fun -- but check your
brain at the door. Most of what they show about asteroids and
space ships is pure Hollywood," he said.