Divert Asteroid, Save Earth

How to deflect asteroids and save the Earth – EurekAlert!

(David) French, a doctoral candidate in aerospace engineering at North Carolina State University, has determined a way to effectively divert asteroids and other threatening objects from impacting Earth by attaching a long tether and ballast to the incoming object. By attaching the ballast, French explains, “you change the object’s center of mass, effectively changing the object’s orbit and allowing it to pass by the Earth, rather than impacting it.”

If you doubt that the Earth is vulnerable to catastrophic asteroid impacts, you need look no further than the pitted surface of the Moon – if you believe the Moon exists.  There are over 500,000 impact craters greater than one kilometer in diameter and one crater which is over 340 kilometers in diameter on the Moon’s surface. Unlike the Moon, the Earth’s active atmosphere and the constant forces of erosion have smoothed over most historical impact sites.

It is thought that an asteroid of 200 meters in diameter strikes the Earth about once every 10,000 years and a giant rock of about 10 kilometers in diameter strikes every 100 million years.  Some scientists blame the extinction of dinosaurs on a significant impact about 65 million years ago.  So, it is a virtual certainty that Earth will be struck again.

To avert another such extinction event, French proposes attaching a very long, perhaps 1,000 to 100,000 kilometers in length, tether to the asteroid with something proportionately massive on the other end.  While this idea seems incredible, French thinks most of the others are too.

“They are all pretty far out. Other schemes include: a call for painting the asteroids in order to alter how light may influence their orbit; a plan that would guide a second asteroid into the threatening one; and of course, there are nukes. Nuclear weapons are an intriguing possibility, but have considerable political and technical obstacles. Would the rest of the world trust us to nuke an asteroid? Would we trust anyone else? And would the asteroid break into multiple asteroids, giving us more problems to solve?”

While this article doesn’t explain how a 1,000 to 100,000 kilometer tether would be constructed and what it would be made of, ribbons of super-strong carbon nanotubes, like those proposed in the construction of a space elevator, seem like the obvious candidates.  Because of the extraordinary properties of carbon nanotubes – very strong and excellent conductors – they are being developed for multiple applications, including power lines.  It is estimated that a space elevator may require a nanotube ribbon as long as 100,000 kilometers and power lines would be much shorter, of course.

Perhaps by the time a big rock heading for our Planet is detected, carbon nanotube cables can be pulled off the shelf, shuttled into space and attached to the subject asteroid.  But what “ballast” to attach to the other end of the tether?  There’s already a large man-made object in orbit which one day may serve its ultimate, unintended purpose.

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