http://news.bbc.co.uk/2/hi/science/nature/8230138.stm

British plan to tackle asteroids

A team of British scientists are developing plans for a spacecraft that could stop large asteroids from destroying the Earth.

The 10 tonne “gravity tractor” would deflect any orbiting rocks years before any potential collision could happen.

The device, which would rely on the force of gravity, is being developed by Stevenage space company, EADS Atrium.

However the idea is still in its early stages and the company admits a prototype has not yet been made.

NASA’s Near Earth Object Programme reports on its website that it has recorded 1068 known “Potentially Hazardous Asteroids”, however there are thousands more estimated to be present in space.

Dr Ralph Cordey, who is EADS Astrium’s head of exploration and business told the BBC that the concept of a tug was actually first mooted by two Nasa astronauts, Edward Lu and Stanley Love, a few years ago.

He said: “Frankly I thought it was crackers. I thought it would never work.”

But he said after reconsidering the idea and focusing on specific engineering issues, including the size of the spacecraft, and long-term propulsion methods, it was considered by the team to be potentially feasible.

The tractor would intercept the asteroid from just 48 metres away and exert a small gravitational force on it, pulling the rock towards it. The pair would then embark on a different orbit, away from the Earth.

It could possibly be powered using solar panels.

However the device would have to be launched at least 15 years before any predicted collision and would need a team to monitor it from the ground during this time.

Dr Cordey said the company had worked with a number of space authorities on other methods of protecting the Earth from asteroids but this one would be able to target a wider range.

He said: “We have done quite a lot of design work on this with the European Space Agency and we believe this would work just as well on a big solid iron asteroid as well as other types.”

But the high cost implications mean that before the device could be made, it would have to be commissioned by a government or a group of governments working together.

10 tons does NOT a lot of gravity make..  They would be better served lofting that much fuel and an engine.

And a honking big, multi megaton nuke to blast the thing into teeny pieces.

It seems to me that it would be like waving a tissue at a Frieghtliner coming toward you.
Given enough time and space you could make a difference, but it would hardly be practical.  Most Near Earth Objects just aren’t discovered that far out. 
As Robin said, they would be better served by lifting something that provides some form of positive thrust to the object and actually effecting the change in a moderate amount of time/space.  (Of course, I tend to like the nukes idea too…)

gray - 01 September 2009 10:35 AM

And a honking big, multi megaton nuke to blast the thing into teeny pieces.

That’s exactly what you don’t want. You’ll increase the risk, as you have changed a single object into multiple impactors. Extending the chances that one of these will hit inhabited areas.

LaMa - 01 September 2009 03:32 PM

gray - 01 September 2009 10:35 AM

And a honking big, multi megaton nuke to blast the thing into teeny pieces.

That’s exactly what you don’t want. You’ll increase the risk, as you have changed a single object into multiple impactors. Extending the chances that one of these will hit inhabited areas.

So, in essence, what you are saying is that a giant, outer space version of dodge ball with hot rocks is NOT a good idea?

DavePrime - 01 September 2009 02:55 PM

It seems to me that it would be like waving a tissue at a Frieghtliner coming toward you.
Given enough time and space you could make a difference, but it would hardly be practical.  Most Near Earth Objects just aren’t discovered that far out. 
As Robin said, they would be better served by lifting something that provides some form of positive thrust to the object and actually effecting the change in a moderate amount of time/space.  (Of course, I tend to like the nukes idea too…)

Large impactors actually are likely to be discovered years in advance. And the smaller ones which you don’t, are usually discovered only hours or at best 1 to 3 days before closest approach. To late to do anything about those whatever way…

It takes only very small orbital shifts to move the orbit of a NEO such that it will no longer meet Earth at the predicted impact point. As scientific studies show, the idea of such a gravity tug is actually a viable idea (unlike the nuke, see my earlier reply).

One other way to move the asteroid’s orbit a tiny bit, is by painting half of it white. Solar radiation force then will do the rest. You’ll need a heck a lot of paint though… 

CarmenSense - 01 September 2009 03:35 PM

LaMa - 01 September 2009 03:32 PM

gray - 01 September 2009 10:35 AM

And a honking big, multi megaton nuke to blast the thing into teeny pieces.

That’s exactly what you don’t want. You’ll increase the risk, as you have changed a single object into multiple impactors. Extending the chances that one of these will hit inhabited areas.

So, in essence, what you are saying is that a giant, outer space version of dodge ball with hot rocks is NOT a good idea?

The proper analogue, is trying to shoot a rabbit with either one bullet or buckshot.

Nuking an asteroid into several fragments is creating the buckshot load, increasing impact risk.

LaMa - 01 September 2009 03:38 PM

It takes only very small orbital shifts to move the orbit of a NEO such that it will no longer meet Earth at the predicted impact point.

Well, shoot.  I wish I would have known that before June so I could have deflected him before he impacted this point of Earth.

LaMa - 01 September 2009 03:32 PM

gray - 01 September 2009 10:35 AM

And a honking big, multi megaton nuke to blast the thing into teeny pieces.

That’s exactly what you don’t want. You’ll increase the risk, as you have changed a single object into multiple impactors. Extending the chances that one of these will hit inhabited areas.

Most of which will be immensely smaller than the original and would likely burn up in the atmosphere instead of hitting earth.  Or if they hit earth would not likely cause near the amount of damage the original would have.

gray - 01 September 2009 04:45 PM

LaMa - 01 September 2009 03:32 PM

gray - 01 September 2009 10:35 AM

And a honking big, multi megaton nuke to blast the thing into teeny pieces.

That’s exactly what you don’t want. You’ll increase the risk, as you have changed a single object into multiple impactors. Extending the chances that one of these will hit inhabited areas.

Most of which will be immensely smaller than the original and would likely burn up in the atmosphere instead of hitting earth.  Or if they hit earth would not likely cause near the amount of damage the original would have.

No….... but the multiple re-entries will most likely heat the atmosphere MUCH more than the single impact. So much so that an atmospheric “firestorm” or area of flash ignition is greatly increased.  i personally would rather die in the impact than in being flash-broiled up to several hundred (thousand?) miles away from the impact(s).

Tah - 01 September 2009 04:33 PM

LaMa - 01 September 2009 03:38 PM

It takes only very small orbital shifts to move the orbit of a NEO such that it will no longer meet Earth at the predicted impact point.

Well, shoot.  I wish I would have known that before June so I could have deflected him before he impacted this point of Earth.

That is why my golf game was off next to Tah, he was affecting the gravitational field in the vicinity.