how with current or near future tech could we stop a 2 mile diameter asteroid heading for earth with

reply to post by DJW001


I'd prefer drilling a hole about 200 meters deep, placing the bomb at the bottom of the hole and then detonating it. We don't have to send a manned mission, robots should be able to handle it.

Originally posted by JIMC5499
Any idea what the mass of a 2 mile diameter asteroid might be? (usually Iron / Nickle composition) Remember one thing, the 57 megaton energy definition is for a bomb detonated in atmosphere, where it is most efficient. Take away the shockwave and the energy output goes way down. Then consider that the only energy that reaches the asteroid is the part of the bomb's energy sphere that makes contact. At optimum (surface burst) that is only 50%. Maybe we better ask the Russkis if they had anything bigger on the drawing board.

Since you were unable to provide a source supporting your "It won't work without an atmosphere" claim, can you at least provide a source for your "usually Iron / Nickle composition" claim? I thought they usually were NOT iron/nickel but I'll gladly review any sources you have supporting your claim that's the usual composition.

Do you have any more faith in a guy from Lawrence Livermore than NASA? This guy named David Dearborn from the former has looked into this and

nextbigfuture.com...

Dearborn created simulations to examine the amount of energy and time needed to most effectively divert an asteroid and disperse its debris field in such a way as to minimize collisions with Earth.

He found that intersecting a 270-meter body asteroid with a 300 kiloton energy source at the surface could safely be done 15 days out from impact.

That article doesn't say what density/composition assumption he used for that calculation, but if you just scale that up for a 2 mile asteroid of the same composition, wouldn't it be something like 42 megatons instead of 300 kilotons?

Energy is measured in Joules, and as far as I know the the conversion formula used is that "One ton of TNT is 4.184 × 10e9 joules". TNT equivalent

If you are saying that the atmosphere factors into that conversion formula somewhere please explain how that works, because I'm not seeing atmosphere in there anywhere, or destructive capability, just energy.

The big problem is warning time.
If you only have a couple months nukes are likely the only option,

If you have a number of years warning then attaching solar sails to the asteroid would do it.

No warning means you have to change the trajectory a large number of degrees to have a miss. the closer the more you will have to change the trajectory.

Years warning allows time attach solar sails. in that case you do not have to change the trajectory just slow down the asteroid or comet enough that the earth passes before the asteroid or comet reaches it.

One thing you have to take into account with a 2 mile diameter asteroid is it needs to miss the moon also.
A 2 mile diameter asteroid hitting the moon would throw up so much rock that the earth would be in trouble as it rained in.

reply to post by Arbitrageur


The show Meteorite Men would be my reference for the composition of meteorites.

The guy from Lawrence Livermore is describing a 270 meter diameter meteor and he's using 300 KT bomb.

We are talking about a 3218 meter diameter meteor, the volume of which is 1694 times the size of the 270 meter meteor. To keep proportionality we would need a 509 MT bomb. That assumes that both bombs deliver the same energy in space that they do on Earth.

I'm not disputing the energy of the bombs, my concern is how much of that energy will be delivered to the meteor?

Originally posted by ANNED
The big problem is warning time.
If you only have a couple months nukes are likely the only option,

True

If you have a number of years warning then attaching solar sails to the asteroid would do it.

Maybe but can you post a source about this proposal? I found this one:

Other proposals

Wrapping the asteroid in a sheet of reflective plastic such as aluminized PET film as a solar sail

Is that what you're referring to? Wrapping the asteroid sounds far easier said than done, but at least if the asteroid is spinning like most are there will always be some reflection back toward the sun.

If you're talking about attaching some kind of solar sail and the asteroid is spinning like most are, wouldn't you have to stop the spinning of the asteroid first? That too may be easier said than done for a 2 mile wide asteroid. And doesn't the solar sail itself have to spin to keep it deployed? I think that's the way the solar sail works on the IKAROS. Then you would need some kind of pivot to spin the sail and you'd have to worry about friction, etc?

There sure seem to be a lot of engineering problems with the solar sail method.

Originally posted by JIMC5499
I'm not disputing the energy of the bombs, my concern is how much of that energy will be delivered to the meteor?

.What's wrong with your 50% calculation at the surface? That sounded about right to me? It seems to me like some of the energy is going into directly vaporizing the surface of the asteroid, instead of partially being used to accelerate the atmosphere in an atmospheric detonation, so I don't see what's wrong with your 50% at the surface?

Your calculation sounds about right. So we need more than 15 days for an object that large (2 miles), which I kind of already knew. That shouldn't surprise anyone.

Here's a video on the matter by Neil DeGrasse Tyson:

www.youtube.com...

For some reason I can't embed it.

reply to post by proteus33


I reccomend instead we adjust the rotational speed of the earth so that we time it up to land on China, Russia or Iran.

Originally posted by technical difficulties
Here's a video on the matter by Neil DeGrasse Tyson:
For some reason I can't embed it.

Well Jim ain't gonna like it because Tyson makes fun of his "blow the sucker up" idea, but of course I love it because he thinks the gravity tractor idea makes sense, as do I. It also has the fewest engineering problems as far as I can see, even with more complicated asteroids.
Let's see if this embed works:

Originally posted by astrogolf
reply to post by proteus33

 

I reccomend instead we adjust the rotational speed of the earth so that we time it up to land on China, Russia or Iran.

I've got friends in or from all three countries so that's not very nice, though my friend from Iran is a refugee who had to leave the country because he was persecuted there, so it's really the governments of those countries I have a problem with, but not the people. Even the UK and US governments seem to be moving more toward a police state every day with the Patriot act never expiring like it was supposed to, and the UK coming up with their version of the Patriot act, so I think the governments in lots of countries could be more benevolent than they are.

But it's interesting you mention that because I read that Carl Sagan thought we shouldn't develop asteroid deflection technology before it was really needed, because the genocidally insane leader of some country on Earth might use the deflection technology to do something along the lines of what you suggest, actually aim an asteroid at a country, rather than use it for deflection. It may be a valid concern.

Originally posted by Arbitrageur
Well Jim ain't gonna like it because Tyson makes fun of his "blow the sucker up" idea, but of course I love it because he thinks the gravity tractor idea makes sense, as do I. It also has the fewest engineering problems as far as I can see, even with more complicated asteroids.

I have no problem with the gravity tractor idea, provided it works. We need to be getting out into space and trying some of these things out. Find out what works and what doesn't. Yes, I favor the "blow the sucker up" idea, because nuclear weapons are proven tech. If it comes down to the fate of the world, do we want to bet the farm on theory or on proven technology? By all means, build some of these things, get them into space and see what works and what doesn't.