The gravity tractor method is feasible if the threatening asteroid is detected early enough and at a sufficient distance from Earth. Based on calculations, it’s theorized that a 20 ton spacecraft could sufficiently deflect a typical 200 meter in diameter asteroid if given a lead time of 20 years. Deflecting a larger asteroid would require a spacecraft of greater mass or more lead time.
Whatever methods are employed to divert the trajectory of asteroids, early detection and better understanding of the objects are critical. That’s why there is great interest in funding increased efforts to explore known Near-Earth Orbit objects and search for presently undetected NEO objects.
That's kind of what I suspected.
We currently have nothing with the power to move large asteroids a sufficient distance anywhere near the earth, and no propulsion systems which could get way out (say, orbit of Mars) to take the long slow approach.
I think the price estimate of a few hundreds of millions of dollars are realistic for startup costs rather than hardware in orbit.
Moving a 200 meter diameter asteroid is a major effort unless its done millions of miles out. Even then you would need a craft that could accelerate to the asteroid, slow down and reverse course to match orbit, and then effect a change in the asteroid's orbit. And after that, hopefully slow down enough to return to earth at less than asteroid speeds.
I don't think we have the propulsion systems for this yet. And I don't think we are going to develop and launch it for a few hundred million dollars.
But we should be working on such a system whatever the cost. A craft that could do that could do a lot of other important things as well.
And we'll just tx the crap out of people to pay for these dumb idea's, right? Of course, we'll need Al- Gore to make a "documentry" a few years in advance to sell the idea, cause a panic, and get the sheeple to wllingly give you their money.
I'm more optimistic it's within our reach. Depending on the orbital mechanics of the asteroid, it's feasible with the technology we have today.
For example, there was the Near Earth Asteroid Rendezvous (NEAR) mission that intercepted Asteroid 433 Eros in February, 2000 and orbited the asteroid for a year before being commanded to attempt a controlled descent to the surface of Eros. The Deep Impact mission sent a spacecraft on a flyby of Comet Tempel 1 and released an impactor object crashing into the comet in July, 2005. NASA's Stardust mission intercepted Comet Wild-2 and returned samples back to Earth in January, 2006.
An asteroid that makes a close approach to Earth and is destined to strike the Earth many years later on a return orbit could be a prime candidate for a gravity tractor mission to launch for a rendezvous on the first pass of the asteroid.