Armageddon?

Question

Okay so we know an asteroid is to hit Earth. (no math is needed) And it is of great mass we will say. So if it were headed on path to hit Earth. Could we divert the asteroid by simply flying a rocket next to the asteroid in order to disrupt the path of the asteroid? Now the physics says that there is an attractive force between any two objects. So by flying a rocket it would attract the asteroid and possibly move it by some small degree to not hit Earth. Now I am saying would an asteroid heading for Earth be able to be diverted by a rocket. Cause with such great distance away and just a small change in path and small target, it could easily miss the planet.

Now if this is possible, then the movie and all that other stuff is false that you must send someone out there to blow it up. Input please.

Answer 1

The same force of gravity will be exerted on the rocket and the asteroid. So the rocket must resist this force of attraction for a sufficient period of time to divert the asteroid.
The energy required to divert an asteroid can be calculated as follows:
m = mass of asteroid
v = velocity of asteroid in earthward direction
R = radius of earth
d = distance of asteroid from earth

Let θ be the angle of diversion =~ R/d
u = velocity component perpendicular to v after diversion
= vR/d
Imparted energy = m/2 *(vR/d)^2

Typically m ~ 100,000 kg
v ~ 10,000 m/s
d ~ 500,000 km
R ~= 6400 km

E ~ 1 GJ
This is approximately the energy released in a small nuclear bomb. If the rocket has to exert that kind of energy, they might as well blow it up.

Answer 2

The situation and solution presented in the movie "Armageddon" were preposterous - you could learn better science from a Roadrunner cartoon. A more realistic threat is an object of 1 km more or less, whose orbit is known. In such a case, we may have years of advance warning, and be able to divert it by means of a series of small deflections. I think I have seen something similar to your gravitational deflection idea, though I don't know if it would be practical - the gravitational force of anything we could send up would be very small, and there are probably more effective things we could do with the mass. In the case of an incoming rock discovered days before impact, there's probably nothing to be done - we just aren't capable of generating anywhere near enough force with any of our technologies.

Answer 3

Haha.

There are lots of 'ideas" on how to save the world from an asteroid.

As for your rocket idea:

The attractive force of the rocket would be negligable and would likely fail to overcome the inertia of the asteroid. For that idea to have a chance of working, the asteroid would have to be spotted so far out into space, that conventional rockets couldn't reach it for a very long time.

In one fo the "Asteroid doom" type movies, they said that only about 3% of the sky can be watched for asteroids due to current technology constraints (telescopes can only magnafy so much of the night sky).

If you're a Stargate SG1 fan, they did an episode about this that was kind of interesting.

Answer 4

Movies are made to entertain, and not to represent science rigorously. You might want to consider the mass of a dangerous asteroid (say 10 km in diameter with a density of 3000 kg/m^3 which is moving at 20000 km/hr. As they say in the old county "Das a who' load of momentum". Do you think a rocket would do much with that?

Answer 5

I heard that NASA keeps track of all objects that could hit the earth, out to those so distant it would take about 30 years to hit the earth. They categorize them by probability of hitting the earth . They are all down in the parts per million or billion.

Answer 6

Maybe you could blast it with a nuclear bomb if one was available and enough time was available. These things are never seen because they would be new to the solar system comming right at the target. So, not much time from the first sighting to the impact.