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.
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.
Hmmmm...I hadn't thought about up-time of the spacecraft. Twenty years is a long time to keep something running continuously with no maintenance in a very hostile environment.
The best case performance of the thing would require that the engine thrust equals the amount of force to be exerted on the asteroid, but unless the distance between the craft and the asteroid is large or the craft uses a pair of engines firing at extremely shallow angles relative to the asteroid (which would be extremely inefficient) I would think the ejecta from the engines would push on the asteroid in such fashion as to work against the desired motion.
Why not just have a spacecraft slowly land on the asteroid, fasten itself, and then use thrusters to push the thing directly?
20 year lead time? Huh? Orbital mechanics can't predict where the rocks will be in 20 years with enough accuracy to determine if they need to be moved. That sounds crazy.
What could be more obvious than that "a sufficient mass" would be most economically available from a small body with low gravity?Or that the acquisition of that mass would require less energy, as the original trajectory of said mass was closer to that of the asteroid you are trying to deflect?
Or that a piece of the threat asteroid itself would fill that bill better than anything else?