NASA astronauts devise asteroid collision plan

Two NASA astronauts have figured out a way to create a real-life version of a Star Wars "tractor beam" to keep an asteroid from crashing into the Earth.

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Simply by hovering nearby for perhaps a year, the astronauts say, the spacecraft's own gravity could minutely slow the asteroid's progress or speed it up, a process that 10 or 20 years later would cause the rogue rock to miss &to=http://english.pravda.ru/science/19/94/378/14269_aliens.html' target=_blank>Earth by a comfortable margin.

"The beauty of this idea is that it's incredibly simple," astrophysicist-astronaut Edward Lu said. Because momentum doesn't dissipate in space, with enough time only a small early nudge is needed to cause a major orbital change, reports San Francisco Chronicle.

According to Science News, as envisioned by Ed Lu and Stan Love of NASA's Johnson Space Center in Houston, the gravitational tractor would hover some tens of meters from a spinning &to=http://english.pravda.ru/science/19/94/379/16037_asteroid.html' target=_blank>asteroid. Only the force of gravity would connect the two.

Careful control of the tractor's thrusters would keep the craft close to the asteroid as it slowly pulled the rock off its collision course. Given enough lead time, it would take just a year for a 20-ton spacecraft to drag a 200-meter-wide asteroid weighing about 60 million tons away from Earth's path, Lu and Love calculate in the Nov. 10 Nature. Towing would have to begin at least 20 years before the projected collision.

A 200-m-wide asteroid could cause significant Earth damage, and many asteroids are much larger. A bigger asteroid would require a heavier tractor to draw it off course.

A tractor would circumvent many of the problems posed by other asteroid-eradication methods. Bruce Willis to the contrary, no scientist has recently suggested nuking an asteroid, notes Love. That's because many asteroids are now known to be porous, loosely bound agglomerations of rubble. O.Ch.

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