Directing dangerous objects to Sun

[Yuri B.]

I have never heard about a plan of cosmic objects endangering Earth to be directed towards the Sun in order to get rid of them. It is unfeasable ? "Sun wind" blowing from the star is stronger than its gravitation ?

 

[mfb]

The solar system is big - millions of objects orbit the sun all the time without collisions. There is no need to hit the sun, that would be a waste of fuel. Solar wind is not an issue, but you have to "brake" the objects significantly to hit the sun.

 

[Yuri B.]

I meant asteroids endangering the Earth against which many sorts of weaponry are discussed (and probably designed and build).

 

[Ophiolite]

I meant asteroids endangering the Earth against which many sorts of weaponry are discussed (and probably designed and build).

As mfb has noted the change in delta V, the velocity of the asteroid or comet, necessary to have it hit the sun is considerable and certainly much more (by perhaps two orders of magnitude or more) than the gentle nudge required to deflect it from an impact with the Earth.

 

[Drakkith]

I have never heard about a plan of cosmic objects endangering Earth to be directed towards the Sun in order to get rid of them. It is unfeasable ? "Sun wind" blowing from the star is stronger than its gravitation ?

Gravity does not suck stuff in like you might imagine. It takes a lot of fuel to counter the orbital velocity of an object and make it fall into the Sun. It actually takes less fuel to push something out of the solar system because we are already moving with a significant velocity.

 

[mfb]

To add some numbers: Assume that our deflection takes place 5 years before the asteroid would hit Earth centrally.

1) If you just want to avoid the collision, rhe required velocity change has to change its path by about 10000km after 5 years, or 0.06m/s. The asteroid would come very close to earth, but miss it. The final orbit would still cross the orbit of earth, so the object could become dangerous at some point in the future (probably millenia or more) again.
2) If you want to change the orbit so much that it does not even come close to earth, you have to move it by ~1 million km in 5 years, or 6m/s.
3) If you want to shoot it out of our solar system, you have to change its velocity by roughly 10000m/s.
4) If you want to drop it into sun, you have to change its velocity by roughly 30000m/s.

While there are cheaper ways to do (3) and (4), they require much more time and very good planning. (1) and (2) are way easier. If we just have 1 year in advance, the numbers for (1) and (2) have to be multiplied by 5, but they are still orders of magnitude below the others.

 

[Yuri B.]

So, it is all not so simple as I thought. Thank you !