Defending the Earth from meteors using lasers

[Rive]

Lasers have bigger range and can be sent to bigger distances,

Actually, even to reach LEO with high energy lasers is a problem.
There is no such limits for spacecraft s.

Attach some sort of engine on a poll and fire it up.

That's the most controllable method, but since even the deflection is the matter of energy, it's not really effective. Reverting to chemical energy seriously limits the energy what can be delivered.

Blowing it up at close range will probably make the situation worse.

Most likely it won't. Most of the fragments won't reach the surface: the shape and the structure of the bigger fragments will be more fragile so even them will cause less problem. It would require a ridiculously big asteroid to make the fragmentation meaningless/worse. So big, that it won't matter anymore...

 

[mfb]

Most likely it won't. Most of the fragments won't reach the surface: the shape and the structure of the bigger fragments will be more fragile so even them will cause less problem. It would require a ridiculously big asteroid to make the fragmentation meaningless/worse. So big, that it won't matter anymore...

A 1 km object can be deflected with enough warning time. If you blow it up into 1000 smaller 100 m objects, good luck keeping track of all that need follow-up missions.

Nuclear weapons exploding in space are lacking the shockwave that contributes to most damage in atmospheric explosions, but they would still have a large impact. Exploding them a bit below the surface can have an even larger effect by ejecting a lot of material at high speed.Evaporating an asteroid is impractical. The smallest asteroids that are of potential interest have a mass of something like 10000 tons and need something like 50 TJ to be converted to gas. If we manage to fully focus a 1 GW laser onto then, we need about a day.
Asteroids that could destroy a town have 10 to 100 times the mass. Now we need 10-100 lasers. Asteroids that can destroy a larger region have even higher masses.

 

[Rive]

A 1 km object can be deflected with enough warning time. If you blow it up into 1000 smaller 100 m objects, good luck keeping track of all that need follow-up missions.

But significant part of those 100m ones would miss Earth (depends on the distance where the main mass blown up). Also:
By wiki: 100m diameter means 3.8Mt and 1.2km wide crater. Of course, more than one of these. Several cities worth of area is blacked.
1km diameter would mean 46Gt and 13.6km crater. ~ a continent is blacked.
Quite a difference I think.

Nuclear weapons exploding in space are lacking the shockwave that contributes to most damage in atmospheric explosions, but they would still have a large impact. Exploding them a bit below the surface can have an even larger effect by ejecting a lot of material at high speed.

Depending on the material of the asteroid we have means to reach 0-30m depth. It would be a really asymmetric event on a bigger asteroide. A good push.

 

[mfb]

But significant part of those 100m ones would miss Earth (depends on the distance where the main mass blown up). Also:
By wiki: 100m diameter means 3.8Mt and 1.2km wide crater. Of course, more than one of these. Several cities worth of area is blacked.
1km diameter would mean 46Gt and 13.6km crater. ~ a continent is blacked.
Quite a difference I think.

If most fragments hit Earth (with a very late explosion), the damage wouldn't be limited to a continent. If the big asteroid hits the water, you get massive tsunamis, but not impact debris everywhere.

Anyway, deflecting it is clearly the better result.

 

[nico nico nii]

why not do this instead? use a rocket to transport multiple explosives & place them on different parts of the meteor. the different directions of multiple bombs should destroy it to small pieces, make it go many ways & miss the earth. that is, considering you have enough time to know where the meteor is going & the bombs are strong enough.

 

[mfb]

Making multiple pieces needs more energy than deflecting it in a safe way, might need a follow-up mission for fragments still hitting Earth, and it is less controllable.

 

[nikkkom]

Tracking 1000 fragments is actually not that hard, computationally speaking it's piece of cake for todays' computers.

 

[mfb]

It is not about tracking. If you randomly blow up something you don't know where the pieces will go to in advance. Afterwards you have to identify all and then do something against those too large and still on a collision course.

 

[Vanadium 50]

I don't see the advantage of taking one body that's going where you don't want it and replacing it with 1000 smaller bodies that are going where you don't want them.

 

[nikkkom]

I don't see the advantage of taking one body that's going where you don't want it and replacing it with 1000 smaller bodies that are going where you don't want them.

Not all 1000 pieces are going to hit Earth.
I do see a very large difference between a continent-buster and a city-buster or three.

 

[nico nico nii]

I don't see the advantage of taking one body that's going where you don't want it and replacing it with 1000 smaller bodies that are going where you don't want them.

I don't think 1000 small pieces can get through the atmosphere without burning out itself. While there may be some parts that get through the

I don't see the advantage of taking one body that's going where you don't want it and replacing it with 1000 smaller bodies that are going where you don't want them.

I don't think 1000 small pieces can get through the atmosphere without burning out itself. While there may be some parts that get through the atmosphere, they shouldn't be THAT big.

 

[nikkkom]

He's talking about a situation when a 1km object separates into about a thousand 100 meter objects. A 100m rock would be only slightly slowed by the atmosphere if it does not break up. If it does break up, it'll be a seriously big airburst. However you slice it, 100m object is going to cause significant destruction.

 

[Dovla]

Perhaps it's better to let some smaller pieces impact the Earth. We can study them, we might find something that we don't know and study it.

 

[mfb]

We can study them better in space. There is no need to risk whole cities for having them impact Earth.

 

[Vanadium 50]

Perhaps it's better to let some smaller pieces impact the Earth. We can study them, we might find something that we don't know and study it.

By that logic, we should take asteroids that are near misses and try and deflect them towards the earth.