Nine Hundred Asteroids in Near-Earth Orbits 149
SEWilco writes: "This Discovery.com item points out a new estimate of 900 asteroids in orbits closer than Mars. Cornell University's William Bottke did a new study of The Spacewatch Project's small-object search. This estimate says that we've found 40% of the nearby asteroids. Well, I'm glad that we've started looking before a disaster, unlike 'Rendezvous With Rama'." Or "Lucifer's Hammer."
Re:Off topic: how come gas giants? (Score:3)
Wouldn't we expect that the greater mass of the large planets, and consequently greater gravity, would compress all their matter into denser (solid) forms?
Whilst it's still an open question thanks to the huge pressures inside Jupiter, it is theorised that Jupiter does have a solid core surrounded by a layer of liquid metallic hydrogen - see this page [nasa.gov] for some more information. Since Jupiter is so large the gravity at its outer edges isn't enough to overcome centripetal forces and cause the entire planet to collapse to a solid core.
And a related question: our solar system has solid and gaseous planets; is there any fundamental eason that there couldn't be liquid planets, or is that just how it happens to fall in this particular uncharted backwater of the unfashionable end of the western spiral arm?
Well, there aren't that many liquid elements at the temperatures present in the Solar System - the material that formed it would have been mainly simple elements that were either gaseous or solid at those kinds of temperatures. IIRC some of the outer moons have liquid ammonia and methane on their surfaces, but in terms of overal quantity these substances remain rare.
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Jon E. Erikson
Re:Off topic: how come gas giants? (Score:1)
Re:Strategies.. (Score:1)
King Arthur? Are you mad?
--Emmett
No Hope (Score:1)
Of course we will never find them all. (Score:2)
Aliens are always black or white in movies (Score:1)
Why can't they show a more realistic alien?????
Re:Heaven's Armoury (Score:1)
Re:Armageddon shows how it could be done (Score:1)
Re:Heaven's Armoury (Score:1)
But if the effort of snagging an asteroid from the Belt, then I suppose you could construct an artificial one with some moon dust and the water on Mars. Yeah. Sure.
Looking for potential collisions (Score:1)
At one time, they even delayed a launch around 3 months to stay clear of some objects out there in space. They weren't really going to come very close, but then I can understand how they didn't want to take the risk with that kind of hardware.
Indirect evidence (Score:1)
Hopefully we'll make that grade soon.
Looks Like They wanted to Copy My website (Score:5)
Delivering a dose of harsh reality to the world for the last 2 years
The important thing about the asteroid threat is that it's one of the few dangers to the human races that
(a) Can Kill us All
(b) We Understand
(c) We have a remote chance of avoiding using modern technology
But Fundamental to this all is the fact that we need to get as much wartning as possible - that's why we should be spending more money on telescopes and serach programs.
In fact - we're so underfunded that I've been seduced away from my job of 'saving the world' to go and work at myplay.com.....
So you know which Music serivce provider to blame when armageddon comes calling.
Speaking of Tracking Things (Score:2)
Using the latest equipment stationed in orbit around the world, scientists barraged humanity with radio and X-Rays mapping out large infestations of so called "dead" spots. Using Open GL 3D CAD programs, they then mapped out and ruled out areas that were electromagnetically shielded naturally. The results were then run through a beowulf cluster, and parsed against hospital records for incumbent lead poisoning.
(Note: Only those idiots who are dense (aka lead headed) fall under this census. Airheads require space density measurement equipment, scheduled to come online in two years.)
The results of these tests were astounding, to say the least. Of the Billion or so idiots who were cataloged, a random selection was made to track these idiots through interferometry. (Judging by the interference they caused with others, and their discussions) These results were then sided against web hits, and so called "Pirst Fost" or first post messages.
Looking at the data, Cowboy Neil was actually dumbfounded to see that, in a 3 dimensional internet, around 900 of these Idiots could be found orbiting slashdot.org at an extremely high rate of speed. Impact collisions, and therefore the spread of such idiocy was extremely high, due to morons missing the "pull up" signal from more intelligent data packets.
krystal_blade.
Re:Wow (Score:1)
Re:Deflecting asteroids (Score:1)
Re:Krakatoa (Score:1)
I refered to the last major climatic catastrophe which good research implicates a similar but larger Krakatoa event in the ninth century. Dendrochronolists have narrowed this down to between 832 and 836 based on tree ring sizes. This has also been backed up by higher than average levels of sulphur dioxide in the atmosphere as detected using ice cores drilled by from both the Artic and Antartic surveys. Krakatoa is implcated by geological survey showing a darker band in the strata of the area. Estimated to have been layed down between 1000 and 2000 years ago.
Re:Deflecting asteroids (Score:3)
Why worry? It's not like there are any dinosaurs around anyway...
Re:Off topic: how come gas giants? (Score:2)
And a related question: our solar system has solid and gaseous planets; is there any fundamental eason that there couldn't be liquid planets, or is that just how it happens to fall in this particular uncharted backwater of the unfashionable end of the western spiralx?
Well, there aren't that many karma elements at the temperatures present in the Slashcode System - the material that formed it would have been mainly simple slasjbots that were either gaseous or solid at those kinds of temperatures. IIRC some of the karma whores have liquid ammonia and methane on their surfaces, but in terms of overal quality these substances remain rare.
Re:Wow (Score:1)
BTW, if any one is tempted to pick up the book, do so. It's excellent. Do yourself a favor, though, and pretend that the rest of the series doesn't exist. They were tacked on long after the fact and are LAME.
Re:Armageddon shows how it could be done (Score:1)
Clarke's books have too many plots. (Was Re: Wow) (Score:1)
No, that's Fountains of Paradise. (That's the one that's about the orbital tether.)
But seriously, Clarke did do an asteroid impact novel, Hammer of God, which wasn't nearly as good as Niven & Pournelle's Lucifer's Hammer, which in turn wasn't as good as Footfall, which included rocks as weapons, but not done as well as in Heinlein's The Moon is a Harsh Mistress.
tc>
Re:Tracking asteriods (Score:1)
Da Pimp be trackin' YO asteroid, honey!
You wanna be a karma whore?
Fine, but don't forget...
Tracking asteriods (Score:4)
Re:Enough of the speciest postings! (Score:1)
Wow (Score:1)
I'm curious though, why should we believe that scientists/astronomers can track _every_ asteroid in a near-earth orbit, when they can't even track _every_ piece of space debris in orbit around earth now?
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Re:Aliens are always black or white in movies (Score:1)
Just like the movie!! (Score:2)
I liked the article's illustration. (Score:1)
Re:SETI@Home asteroid prediction (Score:1)
Solving that N-body problem once is probably not to intensive as you mention. Throw in some statistical deviations on velocity, mass, etc. and then you would need to run that simulation over and over and over and over.
Look at the bright side (Score:4)
BTW, somebody want to buy a 2 KVA generator? Only 6 months old, hardly used. Comes with 200 gallons of petrol. Can optionally throw in a solar panel and radiation proof undies...
Re:Of course we will never find them all. (Score:1)
Re:Heaven's Armoury (Score:1)
Re:And then what.... (Score:1)
Who said we need to shoot it down? Or even break it up? Trying to destroy it would just cause more problems than it solves.
Of course, everything I'm proposing may well be impossible. 'Nuff said.What's wrong with launching a missile which is designed to rendezvous with the rock and just push it out of the way? It wouldn't take much of a nudge if you caught it far enough away from Lunar orbit, a few tenths of a degree would do the job easily. Even inside Lunar orbit, a matter of a degree or two could get it to 'skip' off the atmosphere.
Lets bring em in closer (Score:1)
Of course conversely, altering the path and being a little off does have some nasty side effects. (Eliminating civilization instead of preserving it)
Re:Krakatoa (Score:1)
Re: More importantly (Score:2)
More importantly, the asteroids would be more VALUABLE to reach than the moon. Actually the moon is relatively easy to reach, there just isn't much there to make it worth visiting.
The real trick, as outlined in The Case for Mars [amazon.com], is to establish a Mars waypoint. That opens up the entire asteroid belt for mining. Due to unpleasant technical details (see the book, IANAE [engineer]), it's apparently much, much easier and cheaper to mine asteroids from a Mars base than directly from Earth. Apparently even considering the vast mineral resources of the asteroids, once you get it all back to Earth, if you don't have a Mars waypoint you'll have spent more than you could profit.
None of which is particularly relevant to the main topic, of course...
Re:Tracking asteriods (Score:2)
The article suggests that it is difficult to track the asteriods and see if there is a chance they could hit Earth. Isn't this something that could be done SETI@home style ? I'd much rather be looking for asteriods that could kill millions of people than looking for aliens.
I think the main problem that the article refers to is that there are various issues related to chaos theory that mean we just can't track the orbits so far into the future.
For one thing, the measurements we get aren't accurate enough. Also there are tiny outside influences that add given enough time. These would include gravity from other objects, maybe small collisions and so on. Most of these influences can't be taken into account because we don't know about them, or the effect is just too small. No matter how accurate the original prediction is, the orbit would change over time.
Compare it with trying to predict the exact weather in every part of the Earth a year from now. It can't be done unless you know the state of every molecule on Earth to an infinitely small measure, and even this doesn't take into account the influences form outside the planet.
We have to track it, but it can't be done in the long term with computers because we simply can't get accurate enough starting data.
Test with statistics (Score:2)
Cheers,
Ben
Re:Lets bring em in closer (Score:1)
It is sad but true (Score:2)
This is almost a certainty if it came from the day-side. (A few years ago a pair of mountains did this and were spotted heading *away* from us - they had actually come closer than the moon.)
And even if we did, how quickly could we put together a mission to divert an asteroid? Even if we did, would it work?
If you try to nudge an asteroid with a nuclear bomb and instead shatter it, what would have possibly wiped out a city could cause significant damage across an entire hemisphere instead.
And don't count on insurance. This would be classified as an "act of God" and insurance companies will not be liable unless you purchased special insurance for it.
Cheers,
Ben
Re:Tracking asteriods (Score:1)
Re:Clarke's books have too many plots. (Was Re: Wo (Score:1)
For rocks as weapons, see also Niven & Pournelle's The Mote in God's Eye...
There's a moment in the final conference when they notice that every large and small feature on the alien homeworld is either circular or a fragment of a cricle....Re:Deflecting asteroids (Score:1)
I think a healthey sense of urgency is entirely justifiable.
Nemesis - Buy This Book (Score:2)
Re:redundant? (Score:1)
Computer games develop real world skills. (Score:1)
Re:Clarke's books have too many plots. (Was Re: Wo (Score:1)
"Sure", he said. "They fought at least one war with asteroids. Just look at the surface of Mote Prime, all torn by overlapping circular craters. It must have damned near wiped out the planet. It scared the survivors so much they moved all the asteroids out to where they couldn't be used that way again--"
Of course what you'd really like to do is move the big rocks in, closer to the primary, where you'd have to add energy, and away from obvious gravity assist targets.
I suppose you could dump them all into the primary, but I'd hate to give up all those resources....
tc>
orbiting asteroids (Score:1)
it would be interesting if we could put an incoming asteroid in orbit around earth instead of blasting it onto a different course.
Probably damn near impossible, but interesting.
Idiot moderator (Score:1)
Idiots.
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"Where, where is the town? Now, it's nothing but flowers!"
Re:Deflecting asteroids (Score:1)
Wouldn't it be a good idea then to ship some water into orbit now, just in case. I suspect it is a good idea, but governments don't like spending money on things that aren't certain to happen. But then certaintanty has some form of timescale which may be longer than a term of office!
IMO that targetting these would be quite difficult. I think that nukes down here use GPS for targetting, this means that the GPS satellites are point the wrong way, so the nukes would need some NASA software upgrades or something.
No point worrying though, shit happens and it always will.
Re:Wow (Score:1)
Primarily because Clarke was lumbered with a co-writer. I have read few co-written books that really worked. Good Omens by Pratchett and Gaiman is a notable exception.
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"Where, where is the town? Now, it's nothing but flowers!"
Re:Wow (Score:1)
Last I read, the number of items tracked (debris and other), was somewhere in the range of 40,000 pieces. Granted, flecks of paint aren't likely to cause a catastrophic impact to Earth, but my point is we can't track all the items in orbit around Earth & tracking items further out has got to be even more difficult.
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Sure there are dinosaurs. (Score:1)
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Re:Deflecting asteroids (Score:2)
If the object is small enough, simmply crashing a satelite into it could be enoug.. otherwise landing a probe on it's surface, with a small rocket engine to give it a gentle push could do the trick. Attaching a solar sail onto it was a similar, even cheaper solution proposed somewhere, but I don't remember where I read it.
Ofcourse in the case of a real dinosaur killer, a comet, we are screwed, because by the time you see it, it's going to hit in only a few months. (or a few million years if you can measure it's trajectory accurately enough to know it's not going to hit for another few of it's orbits)
Re:Heaven's Armoury (Score:2)
It would be MUCH easier just to strap a nuke on the back of some mad man and smuggle him into the country.
You can't rule out the fact that the rulers of the saddestic country are human. I hope morality would oppose them causing distruction on such a scale (I believe this is what kept the cold war cold.) If the morality of the leader isn't enough, I doubt any group of citizenship (not even Iraq) would stand for mass distruction on such a scale. When you talk about killing millions of people the pety arguements of a couple of countries just doesn't seem important anymore.
We should be so lucky... (Score:2)
The people of Earth were actually pretty lucky in those books. Humanity survived in both -- pretty well in Rama, not as well in Hammer. But they survived. It wouldn't take too big an asteroid to kill us all, so don't go kidding yourself that those books describe worst-case scenarios. They don't.
--Jim
Re:Deflecting asteroids (Score:2)
We're all here because the chance of anything large hitting us is so remote that no extinction class impact events have happened in MANY millions of years. We can take our time about finding these, maybe a few centuries before we should really consider ourselves tardy.
As for the prospects of deflecting an orbiting body, it's much more likely that we'll have decades of forewarning rather than months for a regular Earth crossing orbit. That should give us more time to plan and more opportunity to act early. We might not have much warning for a cometary impact but unless it's an old one it should be easy to spot and maybe easier to deflect through heating.
As for other deflection schemes, there seem to be several viable alternatives. The solar sail option sounds promising and NASA is about to test the technology. Using anything up there you can find as drive mass for the nuke also seems like something you would consider. With all those earth crossing bodies it might be possible in a few decates to rendevous with one at closest approach to the threat and mine some mass for use as projectile matter for your nuke. It isn't so far fetched when you consider that NEAR is in orbit around such an asteroid.
Given the likely forewarning (not the Hollywood timescale) a NEAR like scouting missions to the threat and other objects followed by a flotilla of missions intended to deflect the threat seems like the most likely scenario.
I doubt we'll ever see this type of mission for thousands or even millions of years. We should probably be more worried about smaller more frequent climate threatening objects, and we should be able to do more about those although they are harder to spot. I guess they're not as sexy as big Earth busters but they're still extremely threatening and vastly more likely to happen. These might be frequent enough to merit a sense of urgency in searching for them.
Re:Krakatoa (Score:1)
Re:Asteroids kill more people than plane crashes (Score:1)
A 1/10th of a degree (Score:1)
1st it would be very difficult to accurately predict an asteroid outside of Earth's orbit.
2nd it would have to be a very large missile to reach said rock
3rd it would take a lot of fuel to move said rock even the 1/10th of a degree you are talking about
We are talking about a asteroid that is HUGE by most of our terrestrial references. We are talking the size of a good size building. It takes a lot of energy to overcome its momentum. Imaging trying to deflect a 6 story office building dropping on you, even if by a tenth of a degree or so.
With the uncertainities in the universe we would have to be VERY careful. Even assuming you have the fuel and means to push it, how would you be certain you deflected it the right direction?
900! good golly! (Score:1)
OTOH,imagine a Beowulf Custer of those babies! if we can get them all moving in sync, we'd have a shield for our planet, courtesy of 900 hunks of ice/rock!
The difference between "spacejunk" and NEO objects (Score:1)
Re:Off topic: how come gas giants? (Score:1)
Well, the current status [psi.edu] of the theory is that it still seems the best one. You might be thinking of the early 1997 research which is mentioned near the bottom.
Re:Looks Like They wanted to Copy My website (Score:2)
Re:Wow (Score:1)
Re:Looks Like They wanted to Copy My website (Score:1)
-Biohazard
not like Rama at all (Score:1)
Re:not like Rama at all (Score:1)
Re:Heaven's Armoury (Score:1)
I think you underestimate the danger these rocks represent. You wouldn't deflect these things onto a city or country, they are continent busters, Earth crushers. These are the kind of objects you cannot get safe from. If one hit the USA there would be no living creatures left on the continent and probably no humans alive anywhere a short time later.
You are also right that smaller rocks represent a danger too, the big question is will it be easier to deflect such a rock at Earth than to use other unconventional weapons. How easy will it be in future to go up there paint a rock black and nudge it at the Earth, perhaps to hit a city of your choice in a few years time.
Re:Krakatoa (Score:1)
Re:Heaven's Armoury (Score:1)
Actually, that is not completely accurate. Unless the Earth was *completely* obliterated, there will continue to be at least some form of life. There are bacteria that are capable of surviving in sulfurous pools, etc, etc. Who knows, the Earth might eventually be repopulated by creatures that evolved from them.
Re:Off topic: how come gas giants? (Score:1)
From what I've read this is because those planets were to far from the sun, and its gravity, so most of the gas from which our solar system was formed got pulled towards the outer planets. The direct result is a relatively small 'solid' planet with an huge amount of gas surrounding it.
As for the liquid planets; there were such planets; take the earth in the beginning. One giant ball of lava which finally cooled down on the surface.
Re:Wow (Score:1)
Re:Moderation in this news item.(Offtopic) (Score:1)
Just because it's not likely to happen at any given moment doesn't mean you shouldn't do something to prepare. It's like saying that there's no sense in having death and dismemberment insurance because it's so unlikely you'll ever be unexpectedly killed or severely injured. Yeah, maybe the chance is only 1 in 100 million, but that's no excuse for not being prepared when the roulette wheel lands on your number.
Since now is the first time in our history when this kind of disaster is concievably preventable given some preparation, would should begin preparing.
Re:Strategies.. (Score:1)
Actually, if you're a member of "the world was always the way I see it now and should always remain the waiy it is now" movement, we should move a bunch of asteroids up around geosynchronous orbit. We'll have to move them to eclipsing positions to shade the Earth when The Authorities decide we're getting "too warm", crash one to make clouds when we're "way too warm", and put mirrors on them to give us more sun when we're "too cool". After all, The Authorities and their experts are always right. And how well is your toilet flushing?
Whaddaya mean? (Score:1)
Re:Wow (Score:1)
Sorry, that was just a brain fart. But I totally agree with you on the rest of the series. Stay away!
Moderation in this news item.(Offtopic) (Score:1)
All of the paranoid, but well-written arguments, "oh we going to die any second from an asteroid and there is nothing we can do about it." posts have all been modded up to like 5. Whereas a rational well-written argument like this one above is left at one.
Now I understand, when moderating that one is inclined to simply mod up posts that one agrees with but no one moderating is not a paranoid nerd?
I for one think that the large amount of time between events is substantial enough to warrent non-paranoia over being killed by asteroids. However my paranoia that this is some American political consipiracy to drum up more support for a space based missle defense system.. is seeming less paranoid.
Re:Off topic: how come gas giants? (Score:1)
For example, if you take a planet made of water with an avarage surface temperature of 50 degrees celcius, the surface would still boil and evaporate near the equator, and be frozen solid near the poles, while at a certain depth below the surface, the pressure would make it solid etc.
It is not surprising that the gas giants are mostly made of lighter elements and molecules, as they are far more abundant in our solar system than heavier materials.
A small gas ball would probably not have enought gravity to become a 'planet', and just exist in the form of a sparse gas cloud, eventually captured by larger concentrations of mass.
Re:Tracking asteriods (Score:2)
If you follow the IAU Circulars [harvard.edu] on comets, for example, you'll see that an awful lot of reports are from .25m telescopes and binoculars.
It's also important to remember the SL-9 lesson [stsci.edu]: Comets do hit planets. If another one hits earth, it'll get ugly.
tc>
The First Might Be in 2022 (Score:3)
At least according to this article [spaceref.com] on spaceref.com [spaceref.com] which states that the eartch approaching asteroid 2000 BF19 has a small probability of impacting Earth. And this press release [spaceref.com] would seem to counteract the claims made here, since NASA states they have cut their estimate of the total number of large asteriods in the Solar System in half.
Perhaps trusting statistical analysis is the problem? Whats the saying "There are lies, damn lies, and statistics"?
Re:It is sad but true (Score:2)
With bombs, damage doesn't linearly scale with size. That is one of the reasons that huge thermonuclear weapons fell out of favor. You can cause more damage with ten 1MT bombs than you can with one 10MT bomb.
Re:Tracking asteriods (Score:4)
What's needed are more dedicated telescopes (luckily, for tracking asteroids, these don't have to be the huge mega-telescopes, small ones (in comparison) work just fine), more funding, and more staff.
Currently, automated dedicated asteroid finding telescopes are responsible for the largest amount of newly discovered asteroids and comets (as opposed to Amateur astronomers, who tend to discover these things). However, there are just so many huge rocks flying around our Solar System that pass near the Earth from time to time that these automated searches would have to be only the major catcher of asteroids, but they would have to totally dominate the discoveries (in other words, they would have to be responsible for many times the current total rate of asteroid discoveries).
SETI@Home asteroid prediction (Score:3)
I believe the problem with long-range asteroid prediction is not computational power. The N-body problem with only a few dozen good-sized gravity wells in the system is easily simulated with a desktop machine. The problem is the accuracy of our measurements. The magnitude of the error term dominates the significant result pretty quickly as you extrapolate measurements centuries into the future.
What are we to make of the lack of public response to the problem of protecting against meteor collisions? With--what?--3 movies two summers ago about major collisions (okay, one was about a comet, which I don't think anyone would survive), still no one has much of a reaction. I don't know whether to revive my faith in humanity, since those execrable had so little effect on the national consciousness, or to leave it dead, because we never wake up and try to save ourselves until it's too late.
hmmm (Score:3)
bring em on (Score:2)
Armageddon shows how it could be done (Score:2)
Re: More importantly (Score:2)
Re:Krakatoa (Score:2)
Krakatoa is a caldera, about every 1000 years is its term. Yellowstone is another caldera due now with the consequences you, everybody with any sense and I fear. The place has risen 8 metres in the last century. Geologically this is scary.
Re:Looking for potential collisions (Score:3)
Re:Looks Like They wanted to Copy My website (Score:2)
Heaven's Armoury (Score:2)
Strategies.. (Score:2)
As far as I know, should we be hit by something a few KM across, the devastation would be immense. Even after the initial impact had settled, there are likely to be worldwide temperature falls of a couple of degrees.
I heard of some research done on tree rings that suggests that there was a similar global climatic catastrophe around the middle of the ninth century. This produced frosts in summer in temperate regions for a few years. Lord knows how cold it git in winter. This was caused by Krakatoa, but estimates suggest that an impact by one of these asteroids at about 6KM across would produce similar results. Here is a link to the NASA page [nasa.gov] covering this topic.
The last major climatic event (being Krakatoa going bang) in the dark ages was probably responsible for the death of King Arthur.
Re:Wow (Score:3)
Objects in Earth orbit that could cause damage to a satellite or space station can be as small as a speck of dust. Asteroids that could cause serious damage in case they hit the earth are dozens of meters or more in size. It's not easy to track them becasuse there is a lot of sky to cover, but it is feasible.
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Asteroids kill more people than plane crashes (Score:3)
So, we can say that the mean is 1000 people/years. This is more than plane crashes (which is about 500 people/year).
40% a little bit to positive? (Score:3)
But I really wonder; if you don't know how many are out there how can you tell that you cought 40% allready ?
Re:Heaven's Armoury (Score:2)
Re:Deflecting asteroids (Score:3)
What's wrong with many small pieces coming into the atmosphere?
The reason that a big asteroid makes it through the atmosphere is that there's so little surface area. It's like saying that a large block of ice takes 1 day to melt, while a similar block smashed into pieces takes 2 hours. Since the surface area is higher, there's:
a) A higher chance that the pieces burn up in the atmosphere (this happens all the time).
b) Less damage since the resulting pieces don't have the same amount of kinetic energy (Would you rather be hit by a car going 20 MPH, or a bicycle going 20MPH?). There have been numerous stories of meteors falling out of the sky and punching a hole in a roof of a building with no other damage. Surely you'd rather pay to fix everyone's roof than have all life on Earth wiped out.
Krakatoa (Score:2)
The last major climatic event (being Krakatoa going bang) in the dark ages was probably responsible for the death of King Arthur.
Eh? What are you talking about with the dark ages? Krakatoa started being active in May 1883, with the final explosive eruption of Krakatoa taking place on August 27 1883. The force was equivalent to that of a 100 megaton bomb, some 5000 times more powerful than the Hiroshima nuke.
There's more information on it here [nasa.gov] at NASA.
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Jon E. Erikson
Deflecting asteroids (Score:5)
It looks like the only technology that could possibly pack enough energy to deflect an object with such momentum is a nuclear bomb. Isn't it ironic that the same technology that brought us the possibility of destroying life on planet Earth could also save it?
A few years ago I did a few back-of-the-envelope calculations to see what would be required to deflect an object a few kilometers in size. Naturally, the delta-V you need to deliver depends on how early you can catch it. If it's still very far you need just a little nudge to ensure it won't collide. It also depends on what margin for error you want to tolerate i.e. how far from Earth do you want it to pass.
It looks like some of the bigger H-bombs have the energy to do it. The problem is how to convert it efficiently to kinetic energy. If you blow up a nuclear bomb in space all you get is a fantastic flash. The relatively small mass of the device itself evaporates and disperses into the vacuum in a matter of milliseconds. You need mass to convert this energy into motion. Using the mass of the asteroid itself is dangerous - if you blow up your bomb too close to the object it could break into many fragments with different orbits. Many of them could still hit the Earth. Splitting it neatly in half Armageddon-style is not very likely
So you need to bring your own reaction mass. The bomb will be accompanied by some big tanks of water. I don't remember the calculations, but you need quite a lot of reaction mass. It appeared to be more than what current launch vehicles can handle.
Have a nice day.
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