Defending the Earth from meteors using lasers

[Dovla]

Hello all. I am new here.

I have an idea about defending the Earth from meteors using laser beams. I thought about using chemical lasers to burn the meteors.

The first phase is that we use gas lasers if possible to create plasma by heating the gas and to use that plasma beam to strike at the meteor before it enters the lower atmosphere. The end result of this would be that the meteor would be burned. Now the second phase.

For this idea, we would need many chemical lasers in many areas. But some would be located on satellites. Those on the satellites would target the far-Earth side of the meteor so that both sides would simultaneously burn.

On this forum there are many professional physicists so I am interested to see what they think about this, looking at it from physics perspective.

 

[rootone]

Conceptually the idea is not impossible.
The trouble is that lasers powerful enough to accomplish this would require a power source equivalent to hundreds of nuclear power stations.

 

[.Scott]

Your idea would be a lot more interesting if it came with a cost proposal.

 

[Dovla]

Conceptually the idea is not impossible.
The trouble is that lasers powerful enough to accomplish this would require a power source equivalent to hundreds of nuclear power stations.

If we advance enough, we might be able to store energy. I know we will not be able to keep it forever, but we might be able to make the energy circulate and we might be able to harvest solar energy using panels and store them or use nuclear energy.

 

[Dovla]

Your idea would be a lot more interesting if it came with a cost proposal.

I think it is more important to save the Earth than to save money.

 

[.Scott]

I think it is more important to save the Earth than to save money.

That would be especially important if your method was the only one available.

 

[Dovla]

Is it possible to turn gas in the laser into plasma by heating?

 

[rootone]

On a small scale yes.
https://www.slashgear.com/super-powerful-laser-creates-plasma-hotter-than-the-sun-22384846/
but even that requires hundreds of trillions of watts.

 

[Dovla]

On a small scale yes.
https://www.slashgear.com/super-powerful-laser-creates-plasma-hotter-than-the-sun-22384846/

So the problem is all about obtaining and storing energy?

 

[gleem]

I found an estimate for the energy needed to vaporize one cu. meter of Earth's crust about 10 Gjoules and it might be significantly greater. So far the best military laser is about 150 KW.

 

[Vanadium 50]

On this forum there are many professional physicists so I am interested to see what they think about this

It doesn't seem that way to me. It seems to me that having them point out problems is making you unhappy.

 

[BenAS]

I think it is more important to save the Earth than to save money.

That's not really how we do things here on earth.

 

[Dovla]

It doesn't seem that way to me. It seems to me that having them point out problems is making you unhappy.

You are thinking wrong. I want to discuss this with everyone,

 

[rootone]

So the problem is all about obtaining and storing energy?

Producing that amount of energy and releasing it more or less instantly is definitely a big problem in itself.
It also has secondary consequences in that unless the conductors used to carry the current are supercooled they will probably vaporize themselves.
Supercoooling thousands of tons of electrical conductors requires even more energy if it can be done at all.
Then you have the problem of the atmosphere; a fair amount of your hyperlaser energy will used up in ionising the air before it gets to the target.

 

[phyzguy]

I think it is more important to save the Earth than to save money.

Try comparing the cost of your proposal to the cost of simply nudging the asteroid out of the way so that it misses the Earth. If you start soon enough, only a very small push is sufficient to make it miss the Earth.

 

[Dovla]

Try comparing the cost of your proposal to the cost of simply nudging the asteroid out of the way so that it misses the Earth. If you start soon enough, only a very small push is sufficient to make it miss the Earth.

What if the asteroid is big enough that nuclear bombs cannot save us?

 

[elusiveshame]

What if the asteroid is big enough that nuclear bombs cannot save us?

If it's that big, we should have sufficient time in spotting it and giving it a nudge. Nuclear explosives could cause issues with debris

 

[nikkkom]

Hello all. I am new here.

I have an idea about defending the Earth from meteors using laser beams. I thought about using chemical lasers to burn the meteors.

The first phase is that we use gas lasers if possible to create plasma by heating the gas and to use that plasma beam to strike at the meteor before it enters the lower atmosphere. The end result of this would be that the meteor would be burned. Now the second phase.

For this idea, we would need many chemical lasers in many areas. But some would be located on satellites. Those on the satellites would target the far-Earth side of the meteor so that both sides would simultaneously burn.

"Small" asteroids (say, below 50m) are not dangerous enough to bother - they can do only localized damage, not regional or global scale.

Asteroids larger than that are too massive to nudge away with laser evaporation (with today's technology).

Technology is going to progress, but ALL technology is going to progress, not only laser tech. With the possibility of heavier payloads being sent to incoming asteroids, and better guidance, it's more practical to send multiple multi-megaton nukes than building multi-terawatt lasers. (Also, for one, I object to anyone *having* multi-terawatt laser in Earth orbit!)

 

[DrClaude]

I have an idea about defending the Earth from meteors using laser beams. I thought about using chemical lasers to burn the meteors.

The first phase is that we use gas lasers if possible to create plasma by heating the gas and to use that plasma beam to strike at the meteor before it enters the lower atmosphere. The end result of this would be that the meteor would be burned. Now the second phase.

For this idea, we would need many chemical lasers in many areas. But some would be located on satellites. Those on the satellites would target the far-Earth side of the meteor so that both sides would simultaneously burn.

You seem to think that "burning" meteors (whatever that means) would make them simply vanish. What you will probably get is something coming at Earth with even more energy than it started with.

 

[rootone]

(Also, for one, I object to anyone *having* multi-terawatt laser in Earth orbit!)

Yeah that sure could be a problem if it was deployed for regular warfare purposes.
Vaporizing an incoming large meteor is on the same scale as vaporizing a city.
Then again it might make fantastic projects like lightsail probes to other nearby stars realisible.

 

[Dovla]

Technology is going to progress, but ALL technology is going to progress, not only laser tech. With the possibility of heavier payloads being sent to incoming asteroids, and better guidance, it's more practical to send multiple multi-megaton nukes than building multi-terawatt lasers. (Also, for one, I object to anyone *having* multi-terawatt laser in Earth orbit!)

Nuclear bombs can pollute our athmosphere, and nuclear bombs can't be used outside of Earth's athmosphere.

 

[DrClaude]

nuclear bombs can't be used outside of Earth's athmosphere.

Why is that?

 

[Dovla]

Why is that?

Rocket that travels into space will deplete its oxygen reserves so we won't be able to send it that far away. Lasers have bigger range and can be sent to bigger distances, we just need energy. With lasers, we can strike meteors when it is farther away thus preventing any unneccesary debris.

 

[elusiveshame]

Is it impossible to add an oxygen tank JUST for the reaction? I'm no rocket scientist, but I can't see that being an obstacle that will prevent creating a nuclear explosion.

 

[phyzguy]

You have many misconceptions in this post:

Rocket that travels into space will deplete its oxygen reserves so we won't be able to send it that far away.

We have sent rockets beyond Pluto. How far away do you want to send them? Also, why do you think rockets need oxygen reserves? Automated probes typically don't use fuel containing oxygen in deep space.

Lasers have bigger range and can be sent to bigger distances, we just need energy. With lasers, we can strike meteors when it is farther away thus preventing any unneccesary debris.

Lasers are subject to the inverse square law, so the further away you aim it, the less intense it is. This does not apply to a bomb, assuming you hit the target.
Also, why are you so fixated on blowing the thing up? The right answer is to modify the orbit slightly so that the asteroid will miss the Earth. This takes much less energy and is much more feasible.

 

[Khashishi]

You don't have to destroy the asteroid to defend the Earth. You just have to deflect it. So, a laser could perhaps vaporize some material on one side of the asteroid, causing a reaction force that nudges the asteroid slightly in the other direction.

Lensing by the atmosphere will create some aiming difficulties for Earth based lasers.

 

[nikkkom]

You don't have to destroy the asteroid to defend the Earth. You just have to deflect it. So, a laser could perhaps vaporize some material on one side of the asteroid, causing a reaction force that nudges the asteroid slightly in the other direction.

BTW, the nuke can be used in a similar way. It can be detonated not on/under asteroid surface, but above it. This would evaporate top regolith layer. With careful selection of detonation point, you can tailor the "push" to your needs.

 

[Khashishi]

Directed Energy Planetary Defense.
http://www.deepspace.ucsb.edu/wp-co...efense-SPIE-Aug-2013-Lubin-8876-101-final.pdf

 

[Dovla]

Ok. I just wanted to hear your thoughts on this idea.

 

[rbelli1]

Also, why are you so fixated on blowing the thing up? The right answer is to modify the orbit slightly so that the asteroid will miss the Earth. This takes much less energy and is much more feasible.

What you will probably get is something coming at Earth with even more energy than it started with.

Blowing it up at close range will probably make the situation worse. Blowing it up at a great distance may help as the trajectories of the resultant bodies will change as long as you get a sufficiently large explosion. If too small it will just coalesce again under gravity. Changing its course seems the better option. Attach some sort of engine on a poll and fire it up. The good news is that the technology and capability already exist for that option.

BoB

 

[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.