Asteroid Deflection
The average distance between asteroids in the Asteroid Belt is 600,000 miles.
In order to deflect a threatening asteroid by the right amount in the right direction, would require very accurate information, not only about its present course, but about its future course. I don’t think we have the ability to accurately predict the course of any asteroid or comet 10 or 20 years down the road. There are perhaps dozens or hundreds of bodies that may have a gravitational influence upon a given asteroid during that journey. If we begin deflecting it, that may introduce even more unknowns into the equation. IIRC, we currently must make occasional course corrections on our interplanetary spacecraft to compensate for the effects of unknown gravitational perturbations.
It might be possible, in our ignorance, to actually deflect what would otherwise have been a harmless close pass into a collision with Earth.
Before undertaking the task of deflecting asteroids, I think we must first implement a system of detectors far enough out to give us a little extra lead time, but not so far out that we would be beyond them. I’d say that about 1.4AU should be about right. Since virtually all threats would be at or near the orbital plane, I suggest perhaps a dozen detectors equally spaced out at about 1.4AU. That would also be a good location from which to launch interceptors.
Unless and until we can accurately predict the course of an asteroid or comet some 10-20 years ahead of time, we may be stuck with more forceful, and faster methods of asteroid deflection than gravitational tugs.
I see no advantage to performing a trajectory correction maneuver at perihelion. The further from coincidence that an evasive maneuver is performed, the smaller the input of energy required. Many asteroids are “piles of rock” conglomerates, loosely held together by a very weak gravitational bond. It would take very little to shatter one of those rock piles, and the result could be deadly. Therefore, the “orion” concept would be not only impractical, but potentially dangerous.
While that is true, there may be an overriding consideration. Depending on the orbit of the asteroid, the difference in orbital velocity between perihelion and aphelion may only be 15%. While this may give you the most “bang for your buck” (% deviation) at that point (perihelion), it won't necessarily provide the most total deviation to the orbit. IOW, if you back up halfway around the orbit and apply the deviation force there, at aphelion, by the time the asteroid has reach perihelion, it will already have deviated (over the course of 1/2 orbit), more than the same amount of force could deviate the orbit at perihelion.
Example. 3361 Orpheus with an orbit of q=.819, Q=1.60 a=1.21 P=1.33
That gives us an orbit of 7.5995AU or 706,754,674.5 miles.
Suppose we impart a deviation (perpendicular to the orbital plane) of .1 degrees at aphelion. By the time the orbit reached perihelion, it would already be deflected by 610,865 miles, IF it was a straight line. Orbital mechanics doesn't work that way. The actual deviation would be 305,432.5 miles in the opposite direction at perihelion. Still, that would be a big head start on deflection, compared to beginning the same deflection at perihelion. The 15% or so that you gained by deflecting at perihelion, would be overshadowed by the overall deflection started at aphelion.
The average distance between asteroids in the Asteroid Belt is 600,000 miles.
In order to deflect a threatening asteroid by the right amount in the right direction, would require very accurate information, not only about its present course, but about its future course. I don’t think we have the ability to accurately predict the course of any asteroid or comet 10 or 20 years down the road. There are perhaps dozens or hundreds of bodies that may have a gravitational influence upon a given asteroid during that journey. If we begin deflecting it, that may introduce even more unknowns into the equation. IIRC, we currently must make occasional course corrections on our interplanetary spacecraft to compensate for the effects of unknown gravitational perturbations.
It might be possible, in our ignorance, to actually deflect what would otherwise have been a harmless close pass into a collision with Earth.
Before undertaking the task of deflecting asteroids, I think we must first implement a system of detectors far enough out to give us a little extra lead time, but not so far out that we would be beyond them. I’d say that about 1.4AU should be about right. Since virtually all threats would be at or near the orbital plane, I suggest perhaps a dozen detectors equally spaced out at about 1.4AU. That would also be a good location from which to launch interceptors.
Unless and until we can accurately predict the course of an asteroid or comet some 10-20 years ahead of time, we may be stuck with more forceful, and faster methods of asteroid deflection than gravitational tugs.
I see no advantage to performing a trajectory correction maneuver at perihelion. The further from coincidence that an evasive maneuver is performed, the smaller the input of energy required. Many asteroids are “piles of rock” conglomerates, loosely held together by a very weak gravitational bond. It would take very little to shatter one of those rock piles, and the result could be deadly. Therefore, the “orion” concept would be not only impractical, but potentially dangerous.
While that is true, there may be an overriding consideration. Depending on the orbit of the asteroid, the difference in orbital velocity between perihelion and aphelion may only be 15%. While this may give you the most “bang for your buck” (% deviation) at that point (perihelion), it won't necessarily provide the most total deviation to the orbit. IOW, if you back up halfway around the orbit and apply the deviation force there, at aphelion, by the time the asteroid has reach perihelion, it will already have deviated (over the course of 1/2 orbit), more than the same amount of force could deviate the orbit at perihelion.
Example. 3361 Orpheus with an orbit of q=.819, Q=1.60 a=1.21 P=1.33
That gives us an orbit of 7.5995AU or 706,754,674.5 miles.
Suppose we impart a deviation (perpendicular to the orbital plane) of .1 degrees at aphelion. By the time the orbit reached perihelion, it would already be deflected by 610,865 miles, IF it was a straight line. Orbital mechanics doesn't work that way. The actual deviation would be 305,432.5 miles in the opposite direction at perihelion. Still, that would be a big head start on deflection, compared to beginning the same deflection at perihelion. The 15% or so that you gained by deflecting at perihelion, would be overshadowed by the overall deflection started at aphelion.
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