Comment »Posted on Monday 20 April 2009 at 6:11 pm by Jacob Aron
In Space & Astronomy, Yes, But When?

Fans of late 90′s disaster flicks will remember that 1998 saw the release of not one but two films about Near Earth Objects. Both Deep Impact and Armageddon featured massive space rocks on a collision course with Earth, and in both cases the day was saved by blowing them up with nuclear weapons.

Back in the real world, David French of North Carolina State University has come up with an unusual alternative. Instead of breaking out the nukes, aerospace engineer French has suggested using a big rope and some weights to save the planet from destruction.

It’s an idea that probably won’t be picked up by Hollywood any time soon, but it would work. By using an asteroid-tether-ballast system you change the object’s centre of mass, which according to Newton’s laws will in turn change its orbit. The space rock flies by, completely missing Earth, and Bruce Willis doesn’t even have to get out of bed. It’s a bit like attaching a tennis ball to a football – the change in centre of mass would mean even David Beckham would find it hard to score a goal/destroy the planet.

Would such a scheme be practical though? One thing’s clear: we’d need a lot of rope. French estimates using a tether of between 1,000 kilometres to 100,000 kilometres – the latter of which you could wrap around the Earth two and a half times!

Maybe it’s not such a good idea then, but when you compare it to other options it doesn’t seem so far fetched. Alternative proposals for Earth defence include painting the asteroid to alter the effect of sunlight on its orbit, and a cosmic game of snooker which uses one asteroid to knock another off course. As for the nuclear weapons used in the films, French thinks they come with just too many problems:

“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?”

Looks like the tether and ballast wins out then – if we can work out how to build one. Perhaps the same technology could be used to make a space elevator? Oh, and if you’re still up for a game of Asteroids – enjoy.


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