NASA plans 'Armageddon' spacecraft to blast asteroid

Not to rain on anyone's parade, but wouldn't constructing this spaceship be considered a weapon system by some less than friendly governments?

And wouldn't nuking a large asteroid just turn it into a lot of tiny bits of an asteroid, and all those bits would hit the Earth and them hitting the atmopshere would heat the planet with friction and we'd all die anyway?

Or am I crazy?

Zoombie said:

Not to rain on anyone's parade, but wouldn't constructing this spaceship be considered a weapon system by some less than friendly governments?

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Depends. Warheads that are capable of reentry need a lot of shielding to not simply burn up in the atmosphere which would be totally wasted on missiles not intended to reentry at all, so nukes designed for intercepting asteroids out in space wouldn't work for shooting targets down on earth. Of course, if you're paranoid about that, you wouldn't what nukes are put on that vehicle, but then, you don't know what's being send up in every rocket that launches from cape canaveral anyway.

And wouldn't nuking a large asteroid just turn it into a lot of tiny bits of an asteroid, and all those bits would hit the Earth and them hitting the atmopshere would heat the planet with friction and we'd all die anyway?

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The heat is pretty much insignificant, what's dangerous is the impact of a large, dense asteroid on earth. If big enough it could possibly break the crust where it hits which is seriously bad.
But anyway, the best way to deflect an asteroid is to just slow it down a little bit, as early as possible. In orbital terms, the earth is a very small, very very fast moving target, so changing the velocity of an asteroid by a few thousandth m/s will make it pass the earth. (if it had otherwise hit us. Of course the earlier you hit the harder it is to predict so you might actually cause it to hit)
If you detonate a nuke close to the asteroid, or even better let it impact and bury a bit, it will vaporize some of the rock, causing a big jet of plasma, vaporized rock and rubble of various sizes to blow of in the direction the nuke came from. Basically you just turned part of the rock and the nuke into an improvised rocket engine. The ejecta will be much faster than the original asteroid and thus pass in front of the earth (and likely years before the actual asteroid) and the remainder will be slowed down and pass behind the earth. The best way is to use several smaller nukes as to not make the asteroid break up
into several pieces before it's slowed down to a save speed.
You'd have to use nukes to slow down each of those pieces individually.

It'd be much better to just mount an ion drive on an asteroid actually, but a lot more expensive and complicated to do.

This assumes some sideways collision which is most likely, a head-on scenario would be far worse. Since you can't just slow the rock down a little bit to make it pass behind the earth, you need to either slow it down enough for the earth to move sideways (which means slowing it down a LOT since the orbit doesn't seem all that circular if you're measuring distances in kilometres not AUs.
Or you need to push it sideways. You still don't need to make it go fast if you hit it early on (Say, ten years before impact, 0,1 m/s (3,6 km/h) will make it move more than twice the earth's diamtere to the side. Still accelerating something massing a few million tons that fast is still a challenge.

Lhun said:

Depends. Warheads that are capable of reentry need a lot of shielding to not simply burn up in the atmosphere which would be totally wasted on missiles not intended to reentry at all, so nukes designed for intercepting asteroids out in space wouldn't work for shooting targets down on earth. Of course, if you're paranoid about that, you wouldn't what nukes are put on that vehicle, but then, you don't know what's being send up in every rocket that launches from cape canaveral anyway.

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It's my understanding that the contents and general design (such as whether it something contains nuclear fuel) of non-military launches ARE generally known and available (though perhaps with a little digging), and there are groups that DO protest the launch of anything with nuclear fuel in it. This is usually used for long-term electricity generation in probes going to the far reaches of the Solar System where solar cell panels won't generate enough electricity. I recall a documentary on one such probe, they had it on a truck going to the Cape, and they said the exact route was kept secret to foil possible nuke protestors. But they certainly don't put nuclear fuel on most launches.

Here's a relevant article:
http://www.space.com/missionlaunches/pluto_hearing_050329.html

Yeah. Well my comment was mostly intended to illustrate that if any government should make an issue out of that it won't be due to real military reasons since there's any number of better targets to pick to be paranoid about.
Oh, and given the opportunity i would like to voice my opinion that people protesting satellites with radioactive payloads because it's taking radioactivity into the solar system are fuckin' stupid. Worrying about contamination after a crash upon starting is legitimate, but because of "environmental reasons?" dear gods, the only thing worse was that woman trying to sue because a science mission was scheduled to shoot at a comet that was holy to her or something.

On a slight tangent -- I was talking to someone about how it would be cool if we could get rid of nuclear waste by finding a way to take it off the Earth safely, then drop it into the sun. She responded, "But what would that do to the sun?"



I tried to explain how you could probably drop the entire solar system into the sun and pretty much all it would do is give it some extra fuel and extend its life by a few days or some such, and therefore a couple of tons of spent fuel rods weren't likely to push it into a supernova. But this is the lack of science education among the general population a project like this asteroid punter would have to deal with if ever it became truly advisable to build one.

NASA

NASA is Armageddon. You have to take a stupid pill before you can work there. We already have the technology to deflect any asteroid out there, if we know it's coming soon enough. And we can do it without blowing anything up.

We sure as heck can't be stupid enough to blow up a 1,000 foot wide asteroid, can we?

We need to disband NASA now, and start a real space agency.

ChunkyC said:

On a slight tangent -- I was talking to someone about how it would be cool if we could get rid of nuclear waste by finding a way to take it off the Earth safely, then drop it into the sun. She responded, "But what would that do to the sun?"

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Jamesaritchie said:

We sure as heck can't be stupid enough to blow up a 1,000 foot wide asteroid, can we?

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What's the fun of a localized debris field?

Jamesaritchie said:

NASA is Armageddon. You have to take a stupid pill before you can work there. We already have the technology to deflect any asteroid out there, if we know it's coming soon enough. And we can do it without blowing anything up.

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Please don't tease, show us a few details...

Jamesaritchie said:

We sure as heck can't be stupid enough to blow up a 1,000 foot wide asteroid, can we?

We need to disband NASA now, and start a real space agency.

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Ben, always excited by the prospect of technical info...

Zoombie said:

Not to rain on anyone's parade, but wouldn't constructing this spaceship be considered a weapon system by some less than friendly governments?

And wouldn't nuking a large asteroid just turn it into a lot of tiny bits of an asteroid, and all those bits would hit the Earth and them hitting the atmopshere would heat the planet with friction and we'd all die anyway?

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You got a problem with this?

caw

Lhun said:

The heat is pretty much insignificant,

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Not true. Figures I've seen indicate that a very large bolide impact, similar to the K-T boundary event of 65 million years ago, would generate heat sufficient to warm the earth's atmosphere, worldwide, several hundred degrees (and at those figures, it don't matter none which major temp scale you use). As Ghostbuster Egon said about crossing the streams: "It would be bad."

caw

Given one large rock, half the size of Manhattan, on a slanting (45°) trajectory through the atmosphere of Earth produces: brief, local, thermal heating around the object as it passes through the atmosphere (probably insignificant overall), and an immense amount of thermal energy upon impact, not to mention all the ejecta from the crater.

Given the same large rock on the same trajectory, converted to gravel by a nuclear bomb prior to entering the atmosphere. There is an insignificant reduction in overall mass, but it's spread around more (maybe). There is similar, brief, local thermal heating around each of the particles, but because there is significantly more surface area, there is significantly more heating. If the particles are small enough there would be virtually no impact with the surface, and therefore no craters and no ejecta.

But in both cases, the same kinetic energy is present. And it is converted to the same amount of thermal energy. Egon is right: It would be bad.

The best hope is to deflect the object so that it misses the atmosphere entirely.

Pthom said:

But in both cases, the same kinetic energy is present. And it is converted to the same amount of thermal energy. Egon is right: It would be bad.

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Which is why it was so ridiculous in the movie Armageddon when they busted the asteroid up inside the moon's orbit. 99.9% of the asteroid's mass was still going to hit the Earth. (friken stoopid movie)

/tangent off. Carry on

blacbird said:

Not true. Figures I've seen indicate that a very large bolide impact, similar to the K-T boundary event of 65 million years ago, would generate heat sufficient to warm the earth's atmosphere, worldwide, several hundred degrees (and at those figures, it don't matter none which major temp scale you use). As Ghostbuster Egon said about crossing the streams: "It would be bad."

caw

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Hm, i'd like to see those figures too. I'll just make a few back of the envelope calculations:
rough mass of earth's atmosphere: 5*10^18 kg
78% nitrogen, so i'll just go with the specific heat capacity of nitrogen:
roughly 30 J/mol K
One mol of nitrogen (N2) are 28g. So the earths atmosphere in my rough model consists of about 175*10^18 mol. For heating the atmosphere by 1K we need 525*10^19 joule.

Let's go with a 300K temperature increase, i don't think any less could reasonably be called "several hundred degrees".
So we arrive at a figure of 1575*10^21 joule for heating the atmosphere by 300 K.
The typical impact velocity for an asteroid is 17km/s. Comets hit much faster but are too small to be interesting here.
So, v=17000 m/s, E= 144,5*10^6 m/s * m
So to get our calculated energy we need an asteroid with a mass of 3.6 * 10^13 kg. Asteroids vary in density, usually somewhere around 2-4 g/cm^3.
So at 3, we need 1.2*10^10 m^3. That's more than a one kilometer cube.
Also, not much of that kinetic energy will actually go into heating the atmosphere at once, most will liquify and deform the rock where it hits, slowly being radiated over a longer timespan as the rock cools down again. Or/and it will vaporize ocean water which has a much higher heat capacity than air. So to actually heat the atmosphere up by 300K you need a much bigger asteroid still. You can play around with this calculator http://www.lpl.arizona.edu/impacteffects/ to see diferent impact effects, but the heating of the atmosphere is not really important since any impact providing enough heat for a substantial global warming will cause far greater damage due to simple kinetic impact.

The trick is not to blow it up. The trick is to find it so early, or on an earlier pass around the sun so that you can defelct it with the least energy possible. Gravity tugs would work--small spacecraft moved in close in front of the object and matched to velocity. The tiny response to the gravity well of the tug will provide added velocity over the long run and the asteroid will miss when it comes back for the strike. The more kilometers away you can start the process thegreater the effect on the asteroid.

Push comes to shove you use nuclear bombs as attitudinal rockets and don't bother to try to break the dang thing up, just nudge it out of "the window".

Regards,
Scott

Gravity tugs are my first choice. Second is land some sort of solar powered rock thrower on the surface. Throw some of its mass away in any direction and the rest will move. Any change in its motion should generate a miss.

Lhun said:

Hm, i'd like to see those figures too. I'll just make a few back of the envelope calculations:
rough mass of earth's atmosphere: 5*10^18 kg
78% nitrogen, so i'll just go with the specific heat capacity of nitrogen:
roughly 30 J/mol K
One mol of nitrogen (N2) are 28g. So the earths atmosphere in my rough model consists of about 175*10^18 mol. For heating the atmosphere by 1K we need 525*10^19 joule.

Let's go with a 300K temperature increase, i don't think any less could reasonably be called "several hundred degrees".
So we arrive at a figure of 1575*10^21 joule for heating the atmosphere by 300 K.
The typical impact velocity for an asteroid is 17km/s. Comets hit much faster but are too small to be interesting here.
So, v=17000 m/s, E= 144,5*10^6 m/s * m
So to get our calculated energy we need an asteroid with a mass of 3.6 * 10^13 kg. Asteroids vary in density, usually somewhere around 2-4 g/cm^3.
So at 3, we need 1.2*10^10 m^3. That's more than a one kilometer cube.
Also, not much of that kinetic energy will actually go into heating the atmosphere at once, most will liquify and deform the rock where it hits, slowly being radiated over a longer timespan as the rock cools down again. Or/and it will vaporize ocean water which has a much higher heat capacity than air. So to actually heat the atmosphere up by 300K you need a much bigger asteroid still. You can play around with this calculator http://www.lpl.arizona.edu/impacteffects/ to see diferent impact effects, but the heating of the atmosphere is not really important since any impact providing enough heat for a substantial global warming will cause far greater damage due to simple kinetic impact.

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This is why I don't write science fiction. Ninja Bunny + major scientific evaluations = exploding head. I mean, I could reason that multiple, smaller targets hitting earth would not necessarily be better than one big one, and I could tell ya it'd be bad for the atmosphere, but I sure as hell couldn't explain it like THAT. I'd be like... "um, there's gonna be more holes in the ground, and uh, the sky might look fun while it's raining asteroid debris."