I would say that a way to avoid being crushed or blown up by a giant rock may be in the interst of some governments.
Space tractor is go!

says, "This is nuts!"

Well it is by far the more common practise to spend the proverbial motherlode in short term, when the situation is dire. 15 years might be a bit far in the future to get people to grasp the severity of such a situation, should it arise.

But it is cool that we have a concept and the power to save our own planet. In my eyes that is a civilisatory milestone.

The problem with 15 years is that you cannot predict asteroid paths with any kind of certainty this far into the future. So the issue will be like: should we commit ourselves to an spending equivalent of second Iraq war in to avert a 0.5% chance of collision?

Why spend all this time trying to make a highly dense, non-reusable ship just to destroy one of hundreds of asteroids? Wouldn't it just be easier to make a high-orbit missile satellite that will hit the stuff away from the earth? Really, it only takes about 500 pounds of C4 to do the job, and the satellite will still be reusable...

500lbs of C4? Firecracker on an elephant, a dead elephant.

This makes very little sense to me. Can someone please explain why this is better than simply applying direct thrust to the asteroid? Station keeping means continously thrusting to maintain altitude from the asteroid. The exhaust of that thrust will hit the asteroid and accumulate or reflect. either way the transfer of momentum is opposite the vector of the gravitational tug. There would seem to be little effect if this is how it will be done. Would it not be better to simply gently nudge the asteroid by attaching the tug to the asteroid and expending the fuel to apply a direct thrust?

Instead of such outlandish concepts, I propose that we hollow out and reinforce many underground salt caverns where we will allow for a hand picked selection of the finest attractive women and men of high value to ride out the aftermath of the catastrophe, and we will fill it with plants to eat and many animals to raise and SLAUGHTER! ... but seriously we need a moon colony or space elevator to get 10 tons of anything out of the earth's gravity well, not to mention alot more telescopes to see and predict asteroids 16 years from impact.

This Nantional Geographic article talks about this in greater detail and explains why landing a craf on the asteroid or blowing it up might not be a good way to go:
http://news.nationalgeographic.com/news/2005/11/1109_051109_asteroid_tug.html

Wouldn't it be funny if:

1. IT worked really well....

2. But by working so well, the new trajectory of foreign object pulled against another LARGER one, sending it here faster than the 15 year advanced notice required.

Now that, would be funny... but in a really dark and depressing sort of way.

Have you seen network television? I'm not sure we're worth saving...

500 pounds of C-4 explosive is the equivalent of 670 pounds of TNT.

Somehow I don't think a .335 ton explosion is going to do much to a large asteroid. (By contrast, it took between 13,000 and 18,000 tons to destroy Hiroshima in WW2)

@LordCore: the only advantage to the "Gravity Tractor" approach is that it will work even if the asteroid is rotating, even at very high speed.

ITs Torchwood!!!

Seems it would be better with current technology to use nukes on an incoming body. Launch say a smart missile; it docks with the Asteroid ( this can be as many missiles needed). You all know the x.y,z axis and trajectory. Plant one blow it and see what happens; plant more if and when needed to change the path towards earth. The explosion will vaporize matter and act as a steering jet..

Surely the best use for using this concept is to guide space rocks into orbit around Earth so that we can mine them and build space cities without having to haul megatons of material off planet! We need to move into space and leave earth for the plants and animals!

@lunapilot - "We need to move into space and leave earth for the plants and animals!"

Well, then...what do you propose that we eat??
Besides, living in tin cans is not the best situation for humans. It may work for a while, but ultimately, we need large open areas that we can live in (without a chance of being sucked into a vacuum if a leak happens).

Does Anybody Remember the Video Game ASTEROIDS??? Why not shoot the damn things now, and push them further into space and let some other alien life form on another planet worry about them??? Or let's move Jupiter in the way of Asteroids!!! Or, Or, Or....

Blowing up an asteroid, if possible would result in a lot of somewhat smaller impacts. Using gravity instead of direct thrust makes no sense for reasons already stated.

What's needed is a hydrogen fusion rocket engine that could use the gasify the asteroid's own material to use as reaction mass.

Personally, I prefer the "Mass Ejector" model, though I think for it to work, the rotation of the 'roid would have to be slowed or stopped by placing reaction motors first. Then the Mass Ejector could work full time rather than intermittently when the gun comes around to face in the direction the thrust is required.

Well I say we hook it up with one of our 302s and set the autopilot to open a 10 sec long Hyperspace window so it may just go through the earth undetected... (='_'=)

I think we need for an asteroid to hit. Just think of all the morons we could eliminate! Politicians, Investment Bankers, Corporate CEOs, MBas , Attorneys, all the professions that have ruined this country...we could start all over!

Lets just send self replicating nano-machines to populate and coat the asteroid. They can mine the asteroid, eject ore pellets to a stable L5 position and in doing so, alter the orbit of the "waste" asteroid to impact the Next threat (be it asteroid or alien)

Earlier I said it only takes about 500 pounds of C4 to get rid of an asteroid problem.

You guys must understand that these things are hundreds of thousands of miles away... We just need a tiny push to get it out of our area... You didn't actually think I meant blow it into tiny pieces, did you?

@Neotyguy40

MV²
-----
2

The velocity is particularly important in this case.

It'll cost many billions of dollars in what will likely be an international cooperation to save our planet, from rocks from space, as well as save the planet from ourselves (for example, reverse global warming due to atmospheric pollution). Aside from science fiction, we have the technology now -- but at this point in the Great Recession that President G. W. Bush created in his anti-science, pro-war funding policies, do we have the money, the will, or the time? Tax-free anarchists -- like the millions of radical right wingnuts back in America -- say we shouldn't do anything because it will involve public funding. They said they will violently protest any attempt to save ourselves, as they view all of this as a conspiracy of leftist, liberal, socialist scientists, engineers and environmentalists. If we try to save the planet in any way, they said they will make sure that we fail by any means, They say that if the Earth is destroyed, it's God's Will, and so, we should do nothing to defy the Word of God. They said, "the private sector free markets" and the Bible, can save us from destruction, and that America, can "go it alone." Last I checked, almost half of the U.S. Congress is composed of these wingnuts selfishly opposing health care on ideological grounds, so can anyone believe they give a damn about the lives of anyone else on this Earth? They don't even care for their own lives in the future, since they beleive they are guaranteed a one-way ticket to heaven, based on their mythological, "Rapture" belief, and they also beleive they are "the last generation"... so not surprisingly, they don't care to invest in the future. They believe the world's going to experience an apocalyptic armageddon. So they said they will help make this prophesy come true, as to prove their obedience to God's Will. You try and save the world from anything, I guarantee that when these wingnuts mass together as like-minded peers, they will do their damnedest to stop you, for their own political, tax-financial and religious reasons, and they will resort to bullying, shouting down, and threaten assault rifle violence in the name of the second amendment, if need be, to get their point across, that they want nothing done.

why instead of pushing the asteroid, we push earth it self? it might sound crazy but if they have the technology to move the asteroid then maybe pushing the earth forward "within it's orbit "is possible too. benefits are what ever we going to use will be right here on earth so we dont take the chance of sending something so far that we can't even repair or reuse 2.we know all the details about earth as far as its weight,speed, next exact location so why miss with unknown, what if that asteroid is made of so unknown heavy material that has it's own mega gravity power and swallow our little toy

why instead of pushing the asteroid, we push earth it self? it might sound crazy but if they have the technology to move the asteroid then maybe pushing the earth forward "within it's orbit "is possible too. benefits are what ever we going to use will be right here on earth so we dont take the chance of sending something so far that we can't even repair or reuse 2.we know all the details about earth as far as its weight,speed, next exact location so why miss with unknown, what if that asteroid is made of so unknown heavy material that has it's own mega gravity power and swallow our little toy

sorry everyone for the repeat. i don't know how it happen

Did you know Torchwood is an Anagramm for Doctor Who... but anyways, this sound promosing

@Anonymous

I'm sorry, I don't understand what that means.

If your saying it couldn't work, then just get a bigger explosive! About 2 tons of nitroglycerin could change the path by at least 1/100 of a degree... I just don't think it would take much to blast an asteroid just slightly. It would be much cheaper too then making an entire space shuttle with extremely dense material and fuel.

15 years? The further out we can detect the object the easier it is to move it to a (hopefully) safe position. If a Asteroid has a couple hundred million miles to travel before it hits us even the kick of a small baby would alter its course, maybe even enough to make a difference (No, I am not saying shooting babies at the asteroid is a good idea!). Personally I would launch a string of nukes at the thing, each one exploding within a calculated proximity to the asteroid, to move it in the direction we want. Check out Project Orion to understand the concept better.

neotyguy,
"About 2 tons of nitroglycerin could change the path by at least 1/100 of a degree"????

Are you trying to "sound smart"?? Where do you come up with these ridiculous demolition figures? These forums are for people interested in reading intelligent responses. You have no idea what you are talking about.

Hey, lay off awdyet, Neo has a good point. The amount of highly dense material that's needed would costs billions for a single asteroid.

By the way, these aren't forums... They are comments, which means that he can discuss it however he wants.

He is just giving an example, a 1 km long asteroid over 100,000 miles away could be pushed really easily, even with that many explosives. You must remember that this is all in space and is happening really slowly. He isn't talking about blowing it to ashes (if he is then he is WAY off).

It only takes a very fractional change of direction to get it out of the path. They could run the ship into the asteroid and it will most likely work. Let alone a few tons of explosives.

@Neotyguy

You also must remember that they can put MUCH more explosives into a missile. 2 tons may be more then enough, but I think they will use more if it comes to that.

This won't work, Michael Bay showed the way... just in his own way. We have all those (H-)bombs just sitting here rotting/decaying away(literally). And everyone seems to know we more than enough to blow up the Earth(let alone a 'little' asteroid) several times over even after reducing the stockpile(s) on both sides after the Cold War. So? Why not use them and send them ahead to blast these bullying space rocks away(better they blow up (well)away from Earth than on it), plus their already paid for and like I began with their already there a plenty. While as last ditch close range offensive is impossiblly hopeless at stopping anything(most still existing nukes(missles) are trained on each other rather than to the heavens) bigger than say a boxcar. Blasting it repeatively would change the course of the offending Rock from space.
Take heart that I wrote this in jest(partly) to many things.