If I had a place to stand...

[Sabine]

Thought I'd share something I saw on TV the other night.

It was a program about what would happen if we spotted some kind of large Killer Asteroid^TM on a collision course for Earth, ala Armageddon.

Given ten years lead time, which I as a complete lay person find somewhat unrealistic, the program claimed that it would be possible to affect the Earth's orbit enough to miss the asteroid. The theory was that we would (somehow) use another massive object to deflect the Earth.

As the program explained, there is an "ion drive" (sorry, it was in German and I don't know the English term) that uses water to create thrust (somehow, this was illustrated with a line drawing of ice being sucked into a machine and some dots flying out the other end). We would set this kind of drive up on Ceres, an asteroid with tons of ice, and use it to propel Ceres toward Earth. With the right trajectory, making Ceres pass close enough to earth would be enough to deflect our orbit enough to let the Killer Asteroid^TM fly right by us.

The whole thing seemed kinda questionable, but intrigued me. Would something like this even be possible? Could we influence the Earth's orbit like that? Or is this a totally crackpot idea?

[gwiz]

Ceres is a very large object by asteroid standards and it would need a lot of added velocity to bring it to the vicinity of the earth. It has got to be many orders of magnitude easier to just deflect the asteroid.

[Jason Thompson]

So, in order to avoid a collision with an asteroid we send up a propulsion system onto another asteroid to send that one towards Earth in order to deflect Earth from the path of the killer asteroid? If we can do that why would we risk sending another asteroid close to Earth? Why not simply use the ion drive to deflect the killer asteroid in the first place?

[echnaton]

Nov 25, 2009 13:31:11 GMT -4 Jason Thompson said:

Why not simply use the ion drive to deflect the killer asteroid in the first place?

Because from what the OP said, the scheme relies on the presence of water ice on Ceres for use in some way as a propellant.

It is still rather far fetched to think we could build, deliver, and control such a system in the time from discovery of some killer asteroid to its impact. Not to mention the unknown effects of shifting the earth orbit. Or worse, what if we caused Ceres to hit earth? The scenario goes from global disaster to global annihilation.

But if someone did try this, would it be better for a Ceres swing by to give us a longer or shorter year. After a calendar adjustment, we would either live to be a ripe old age or follow The Who's advice and die before we get old.

[Sabine]

Excellent question. I thought of that too, but the reasoning was that just getting to the Killer Asteroid would take too much time, Ceres is closer. Remember, they asssumed we would notice this object ten years before it hit Earth. Also, would we be able to say for certain if the Killer Asteroid had enough ice to power this magical water-powered drive? The program made it sound like Ceres was especially icy as asteroids go.

[gillianren]

You know, it would be smarter to just deflect the asteroid. Moving the Earth's orbit would have all kinds of horrible possible side effects. I can't even begin to imagine.

But ten years' lead time doesn't sound that improbable to me.

[Sabine]

Must've posted at the same time as echnaton.

Are there really that many people looking around the solar system for objects that might hit us in ten years? I always kind of assumed something like that would totally take us by surprise.

As for changes to the Earth's orbit, it was shown to become less elongated, allegedly resulting in "just half a degree rise in temperatures", which was glossed over as if it were nothing.

[echnaton]

Are there really that many people looking around the solar system for objects that might hit us in ten years? I always kind of assumed something like that would totally take us by surprise.

There certainly are many amateur astronomers looking for asteroids in the sky every night. Our local public research telescope is staffed almost every night. I have no idea if one could be seen 10 years before it hit us. Or even if a prediction of a earth strike could be made with sufficient accuracy 10 years into the future. I am pretty sure it would cause a mild hysteria among the earth disaster crowd and some politicians would rally around the cause regardless of the science. There is always a group that want's to have a impending disaster to exploit so they can fix it. Some of them are called hoax believers.

[Ginnie]

Nov 25, 2009 12:23:03 GMT -4 Sabine said:

Thought I'd share something I saw on TV the other night.

It was a program about what would happen if we spotted some kind of large Killer Asteroid^TM on a collision course for Earth, ala Armageddon.

Given ten years lead time, which I as a complete lay person find somewhat unrealistic, the program claimed that it would be possible to affect the Earth's orbit enough to miss the asteroid. The theory was that we would (somehow) use another massive object to deflect the Earth.

As the program explained, there is an "ion drive" (sorry, it was in German and I don't know the English term) that uses water to create thrust (somehow, this was illustrated with a line drawing of ice being sucked into a machine and some dots flying out the other end). We would set this kind of drive up on Ceres, an asteroid with tons of ice, and use it to propel Ceres toward Earth. With the right trajectory, making Ceres pass close enough to earth would be enough to deflect our orbit enough to let the Killer Asteroid^TM fly right by us.

The whole thing seemed kinda questionable, but intrigued me. Would something like this even be possible? Could we influence the Earth's orbit like that? Or is this a totally crackpot idea?

I don't know if its that crackpot.
In Phil Plait's book "Death From the Skies" he goes over many different ways to avoid collision with an asteroid. I think altering the asteroids orbit (either hitting it with something, or better yet getting something close to it to affect its orbit) would be easier than changing earth's orbit.
I think he mentions changing earths orbit like getting earth further out from the sun when it starts going supernova etc. I forget how he says we could possibly do this because I don't have the book handy. I do recomend the book though - basically it describes all the ways we can meet our end from objects in space - asteroids, comets, stars, black holes... and how we can try to avoid our destruction.

[Al Johnston]

As Gillian said, you really, really, really don't want to change Earth's orbit: the side effects don't bear thinking about.

Planet moving is surprisingly common in SF, but with a decade's notice, deflecting the asteroid would be the only sensible option.

[gwiz]

Nov 25, 2009 14:05:05 GMT -4 Sabine said:

Excellent question. I thought of that too, but the reasoning was that just getting to the Killer Asteroid would take too much time, Ceres is closer. Remember, they asssumed we would notice this object ten years before it hit Earth. Also, would we be able to say for certain if the Killer Asteroid had enough ice to power this magical water-powered drive? The program made it sound like Ceres was especially icy as asteroids go.

If you've got a propulsion system that can shift Ceres, you can use it for high-energy trajectories around the solar system so time isn't an issue. You can use it to go and get ice from Ceres - a tiny fraction of that needed to shift Ceres itself - and take it to the asteroid.