Asteroid Impacts

[Ian]

If an asteroid is ever discovered does anyone think that it could be blown up with antimatter? There's a lot of concern about near earth asteroids. Please reply.

 

[Seismosaurus]

If an asteroid is ever discovered does anyone think that it could be blown up with antimatter? There's a lot of concern about near earth asteroids. Please reply.

Antimatter wouldn't be the way to go. Right now it would take pretty much the combined industrial might of the planet to produce enough antimatter to equal a good sized hand grenade.

You might be able to make a big enough nuke... but there are all sorts of parctical problems with blowing up asteroids anyway, the primary one being that if you do it wrong you end up with a million or so pieces coming at you instead of one big one - essentially the astronomical version of a cluster bomb.

What you really want to do is deflect the asteroid's course. You can do that with a bomb, assuming the asteroid isn't porous so that it just absorbs the benergy. But there are methods that are potentially better, though harder to implement. Using a giant mirror to focus sunlight onto the 'roid and letting the vapour act as a rocket, for instance.

If we're to have any chance at all of deflecting a good sized asteroid, you'd want an absolute minimum of ten years warning. Preferably twenty or more.

 

[MRC_Hans]

Blowing it to bits is not such a bad idea, if the bits are small enough. Rocks of brick-size and below will burn up in Earths atmosphere, and even much greater bits will have a terminal velocity (due to air resistance) of a few hundred mph. -- Thats bad if you happen to get hit by it, but there will be no widespread damage by energy release.

On way to deflect it would be to place a rocket engine on it. Only a minute deflection is needed to make it miss Earth.

Hans

 

[Yahweh]

Blowing it to bits is not such a bad idea, if the bits are small enough. Rocks of brick-size and below will burn up in Earths atmosphere, and even much greater bits will have a terminal velocity (due to air resistance) of a few hundred mph. -- Thats bad if you happen to get hit by it, but there will be no widespread damage by energy release.

I dont usually take the time to think of such things as asteroid rapturing the earth, but I have taken enough thought to consider that a hit by a cannonball doesnt do as much damage as that same cannonball in the form of a shotgun blast...

 

[EvilYeti]

Blowing it to bits is not such a bad idea, if the bits are small enough. Rocks of brick-size and below will burn up in Earths atmosphere, and even much greater bits will have a terminal velocity (due to air resistance) of a few hundred mph. -- Thats bad if you happen to get hit by it, but there will be no widespread damage by energy release.

Thats not quite true, the sheer net mass of material would literally set the atmosphere itself on fire. Rember we are talking about millions of cubic meters of debris. The firestorms would be devastating. Smaller asteroids could be safely broken up; but the really big ones (several kilometers wide) will devastate regardless of how many pieces its in when it hits.

My idea to knock the asteriod off course is to build thousands of simple guided missles that contain a small fissile payload in the tip. The fission reaction would be set off by the impact of the rocket on the surface of the asteroid (the relative speed of the collision should be enough to induce critical mass). This would have the effect of blasting off some mass while also slowing the approach slightly. By using hundreds, thousands, whatever of these things it would not be an issue if a few malfunctioned.

 

[wollery]

Re: Re: Asteroid Impacts

Using a giant mirror to focus sunlight onto the 'roid and letting the vapour act as a rocket, for instance.

Wouldn't work with an asteroid as they're just made of rock, although it would be ideal for a comet!

 

[neutrino_cannon]

Re: Re: Re: Asteroid Impacts

Wouldn't work with an asteroid as they're just made of rock, although it would be ideal for a comet!

Why not? It's space, there's no way that theheat can be dissapated throught conduction or convection, and I certainly can't radiate away faster than you can throw it at the asteroid with a ten square mile mylar mirror. Eventually the rock will start to vaporize, and presto, solar powered rock-vapour plume.

You're right, it would work better with comets, but aside from causing all the events in Genisis, what have comets ever done to us? (Velikovsky)

 

[Soapy Sam]

Drilling rigs up in the Grand banks have a problem with icebergs.
Unlike a ship, a rig can't dodge much.
They could bomb the icebergs, but it's easier to put a big rope arond them and nudge them off any collision course while still miles away. A few degrees is all it takes.

Pretty much the same is true of asteroids.

So the answer is vigilance. Watch them, track them and spot the dodgy ones decades ahead, so there's time to apply a gentle shove.

 

[ceptimus]

Comets are a big problem. With long period comets, we rarely get more than a few months warning of their approach - you just can't detect them when they are several years away.

So although we might be able to something about an asteroid, it is very unlikely we could do anything useful at all about an approaching comet.

IMO the main reason you hear all this stuff about protecting against asteroids at the moment is that nuclear bomb scientists and engineers wish to continue their lucrative employment.

How would we deliver the bombs to the asteroid anyway? Right now, we have no launch vehicles that could do the job - even if the space shuttle were operative, it can only get to low Earth orbit. The last vehicle that we had with the necessary oomph (the Saturn 5 moonrocket) doesn't exist anymore, and in a brilliant bit of spring-cleaning, NASA destroyed the plans for it, so we couldn't build a new one real quick, even in an emergency.

But, as I said, the main disadvantage with 'space guard' is that it cannot, even in theory, provide us with a defence against comets, and we are probably more likely to be hit by a comet than a near earth object.

 

[Yahweh]

So although we might be able to something about an asteroid, it is very unlikely we could do anything useful at all about an approaching comet.

Very large baseball mit...

 

[MRC_Hans]

Thats not quite true, the sheer net mass of material would literally set the atmosphere itself on fire. Rember we are talking about millions of cubic meters of debris. The firestorms would be devastating. Smaller asteroids could be safely broken up; but the really big ones (several kilometers wide) will devastate regardless of how many pieces its in when it hits.

*snip*

I don't think anybody knows the true answer, but I disagree with your assessment. First of all, the atmosphere is not combustible, so nothing can "set the atmosphere itself on fire". I'm sure a million ton of pepples, rocks, and boulders would make not only a fantastic firework, but also a LOT of damage, but the point is that each impact would just be a hole in the ground (and everything else that had the ill fortune to be in the way) while a whole asteorid would not be slowed down much by passing the atmosphere. Instead it would impact the surface of the Earth with a sped of many miled per second and release the equivalent energy of thousands of H-bombs.

As for the bullet/shot comparison: remember that we are somewhat protected by our atmosphere. If you were behind even a wall of wooden planks, a blast of shot would be better than a cannonball.

But without question, deflection would be best of all.

Hans

 

[Seismosaurus]

Re: Re: Re: Asteroid Impacts

Wouldn't work with an asteroid as they're just made of rock...

Surely you aren't suggesting that rock cannot be vapourised?

Or perhaps you are underestimating the size of the mirror I'm talking about...

 

[ceptimus]

In the news today

A potential asteroid impact on 21 March 2014 has been given a Torino hazard rating of 1, defined as ‘an event meriting careful monitoring’. The newly discovered 1.2 km wide asteroid, known to scientists as 2003 QQ47, has a mass of around 2 600 billion kg, and would deliver around 350 000 MT of energy in an impact with Earth. Currently, the overall probability of this asteroid impacting Earth is 1 in 909 000.

 

[Deetee]

In the news today

A potential asteroid impact on 21 March 2014 has been given a Torino hazard rating of 1, defined as ‘an event meriting careful monitoring’. The newly discovered 1.2 km wide asteroid, known to scientists as 2003 QQ47, has a mass of around 2 600 billion kg, and would deliver around 350 000 MT of energy in an impact with Earth. Currently, the overall probability of this asteroid impacting Earth is 1 in 909 000.

So the chance of it impacting on earth is 15 times greater than my chances of winning the national lottery here in UK.

On the radio this morning, it was explained that if it hits, it would destroy an area the size of France, to which one person listening texted in "Destroy France? - bring it on!"

 

[Ziggurat]

I don't think anybody knows the true answer, but I disagree with your assessment. First of all, the atmosphere is not combustible, so nothing can "set the atmosphere itself on fire".

I don't really think that's what he meant. If the energy is all absorbed in the atmosphere, it will not "combust", but it can reach temeratures hot enough to set fire to everything under it, and also generate enormous shock waves. The issue is that whether you have a single piece or lots of small pieces, the energy has to be absorbed. If the total mass is big enough, absorbing that energy in the atmosphere isn't going to save you - the heat generated is still going to fry everything under it, and send shockwaves that can level a HUGE area. That's pretty much exactly what happened with Tunguska, where something (maybe a comet) hit the atmosphere and disintegrated around 8 km above the ground. If that happened above a populated area, that would have been VERY bad news. In other words, the atmosphere provides very little protection once the total mass is large enough, whether or not it's broken up into small pieces. When you're talking about asteroids that can take out a whole country, for example, the little thin layer of atmosphere is pretty much meaningless.

 

[daver]

IMO the main reason you hear all this stuff about protecting against asteroids at the moment is that nuclear bomb scientists and engineers wish to continue their lucrative employment.

How would we deliver the bombs to the asteroid anyway?

This won't do much to invalidate your nuclear scientist welfare scenario, but the only vessel we have that is even close to on the drawing boards that could reach the asteroid in time with enough oomph to do something about it is an Orion drive--essentially a big metal plate with battle-ship-sized springs on one side holding up the crew module, and cannon along the edges to fire nuclear bombs to explode on the other side. The blast from the explosions impacts the pusher plate and pushes the whole thing through space at high acceleration and high Isp.

If the asteroid is a solid piece of rock, you could use your nukes to nudge the asteroid off course. If it wasn't, you might have to do something silly like send four Orions (one for a spare) and a big net out. The Orions use the net to contain the pieces of the asteroid while they try to nudge it in a useful direction.

However, this asteroid is a big mother. I'm not sure that five years is enough time to alter the orbit sufficiently (that's assuming five years to build the Orions and rendezvous with the asteroid).

The last vehicle that we had with the necessary oomph (the Saturn 5 moonrocket) doesn't exist anymore, and in a brilliant bit of spring-cleaning, NASA destroyed the plans for it, so we couldn't build a new one real quick, even in an emergency.

That's not quite accurate. The plans still exist, but the production notes and the engineers who built it by and large don't. Frankly, having the plans wouldn't help much--it'd be cheaper and faster to design it from scratch. The main problem would be trying to prevent some idiot from trying to get every last second of Isp from the motors, and instead build them simple and robust.

The Saturn V is still hopelessly inadequate for the job. You need nukes, and lots of them. If you have a few centuries, you could make do with a few cans of spray paint, but for this one, at least, you don't have that option.

But, as I said, the main disadvantage with 'space guard' is that it cannot, even in theory, provide us with a defence against comets, and we are probably more likely to be hit by a comet than a near earth object. [/B]

Given a hundred years advance warning, we could do something about a comet.