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Back off, asteroids–We’ve got nukes

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MIAMI—To avoid Armageddon, we may have to invoke Armageddon. You know, the Bruce Willis version.

That’s the opinion of David Dearborn, anyway, who says we may need to tap our nuclear arsenal if a life-threatening asteroid suddenly comes into view. Dearborn, a research physicist at Lawrence Livermore National Laboratory, laid out the nuclear case in a talk here Tuesday at the semiannual meeting of the American Astronomical Society.

Dearborn’s research on nuking asteroids is a fairly natural outgrowth of his other work, which has involved weapons development and testing, as well as three-dimensional modeling of astrophysical processes. He has run numerical simulations of how a nuclear detonation either near or on the surface of a threatening near-Earth object could divert or fragment it, and has found that with a little bit of lead time the weapons could do the job rather well.

Unlike the asteroids themselves, whose makeup and physical properties are not always well understood, nukes have been well characterized through testing. "We know what the nuclear part is going to do," Dearborn said. Gentler diversion schemes such as tugging the object onto a safer path tend to run into problems, he argued, because asteroids are such a diverse class of objects, and some might not hold together if grabbed in some way. "What’s their structure? Rock or rubble?" Dearborn asked rhetorically. "The answer is yes."

A directed-energy weapon could do the job, Dearborn said, but not in the state that the technology is in today. A laser such as that at the National Ignition Facility, a nuclear fusion experiment at Lawrence Livermore, could adjust a typical asteroid’s course enough to avoid a collision—changing its velocity by about one centimeter per second—but doing so would take about 6,000 years. "I’m not saying that our children’s children won’t know a lot more than we do, and I certainly hope that they do," Dearborn said, but laser technology isn’t up to the job just yet. A non-nuclear blast—or a simple ramming mission—could also work, but those approaches would require numerous launches to match the power of a single nuclear device.

So what would a nuclear warhead actually do to an asteroid? It depends on how much time humankind had to deal with the threat. With a decades-long heads-up, a velocity shift of only a fraction of a centimeter per second would be needed, Dearborn said. In that case a detonation near—but not on—an asteroid would give it a sufficient nudge while leaving the object mostly intact. With less time to address the inbound impactor, a direct detonation would be needed. The downside is that some of the fragments might still hit Earth, although they would at least be reduced in size compared to the original object. Dearborn has simulated a last-ditch effort to destroy a 270-meter asteroid similar to Apophis, which has a very small chance (about 1 in 233,000) of striking Earth in 2036. With a detonation even 15 days before impact—"about the closest you’d want to do this," Dearborn said—only a few percent of debris would remain on course to hit Earth. But all simulations make some assumptions about the composition of the asteroid—when Dearborn ran other models assuming an asteroid with a core the strength of granite, he found that even a nuclear blast could still leave a dangerous solid core. If humankind had 30 years to deal with the problem, then, the best thing to do would be to launch a characterization mission to the asteroid, Dearborn said.

Of course, nuclear weapons make many people uneasy in any context, and not everyone is on board with the nuclear approach to asteroid deflection. But Dearborn maintained that the radiation from a detonation in deep space, where the radiation environment is already intense, would have no effect on life on Earth. "You wouldn’t even be able to measure the difference in radioactivity," he said.

With any luck, all of Dearborn’s modeling will remain an academic pursuit that never gets put to the test. "You shouldn’t feel tremendous worry," Dearborn said, noting that impactors capable of regional destruction only come around on an average timescale of tens of thousands of years. And whereas an asteroid of that class could flatten everything from Los Angeles to Sacramento, a global killer only comes around every million years or so, Dearborn said. Perhaps most reassuring of all, Congressionally mandated programs have already catalogued what appears to be the vast majority of the largest objects, none of which pose a significant risk in the foreseeable future. But plenty of people are working on mitigation schemes—far-fetched though some of them may sound—just in case the sci-fi scenario of Armageddon becomes reality.

Photo of Meteor Crater in Arizona: NASA

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  1. 1. hotblack 5:41 pm 05/26/2010

    Unfortunately, to be far enough out to meet an asteroid in time, would require either an incredibly quick threat assessment and response time, or rather a hell of a lot of nukes floating in a defense sphere with at an incredible radius & millions of points in between, out in space.

    The detonation concept is brilliant. Instead of a giant rock the size of texas hitting us, it’d be a giant rock the size of texas with a crater on one side, and a giant fallout cloud from a nuclear attack. …or even if we were somehow successful at "blowing it up", we’d have what, two giant rocks, half the size of texas, with the same mass, hitting us simultaneously. Yes, I predict success.

    The best option, as far as I can tell, is to continue thinking that asteroids won’t hit us because we’re Gods sole reason for the universes existence.

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  2. 2. sethdayal 7:21 pm 05/26/2010

    Sorry no can do. We are retiring the space shuttles to save $3 billion a year from our $600 billion military budget.

    That’s what happens when 99% of our politicians are attorneys.

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  3. 3. Chuck Darwin 7:59 pm 05/26/2010

    @hotblack–I seriously doubt Dearborn or anyone else is talking about using a nuke to deflect a "giant asteroid the size of Texas." Texas is a little over 1200 km wide (and about the same tall). Ceres, by far the most massive asteroid, is only 950 km in diameter. No Solar object anywhere near that size has a possible Earth-intersecting orbit. One nuke (or several) wouldn’t begin to affect an object that size, and nobody is suggesting it could. They’re talking about objects in the 10 km range. And I would venture to guess that when a nuclear scientist and astrophysicist like Dearborn does the math and publicly says a nuke could work, he has more cred than some anonymous blog commentor blowing smoke out of his ***.

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  4. 4. jtdwyer 8:25 pm 05/26/2010

    Chuck Darwin – You stated:

    "And I would venture to guess that when a nuclear scientist and astrophysicist like Dearborn does the math and publicly says a nuke could work…"

    - then all other accredited and qualified scientists should be unanimous in their agreement with Dearborn, correct? Nobody is beyond question, and scientific issues are sometimes settled by factual data rather than political standing – otherwise there would be no scientific progress.

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  5. 5. Unksoldr 11:16 pm 05/26/2010

    The best option, as far as I can tell, is to continue thinking that asteroids won’t hit us because we’re Gods sole reason for the universes existence.

    LOL stupid people read SA too.

    Link to this
  6. 6. hotblack 2:39 am 05/27/2010

    A shame, you started out well enough, but then ended citing "cred". People gullible enough to be impressed by "cred" are just as foolish as the next anonymous commentator talking out their ***.

    And that was sarcasm at the end there, Unk.

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  7. 7. Iahmad 4:48 am 05/27/2010

    Fantastic; America can threaten heavens also after terrorising the earth with its nukes and other weapons of mass murder.

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  8. 8. jaqcp 10:59 am 05/27/2010

    "The best option, as far as I can tell, is to continue thinking that asteroids won’t hit us because we’re Gods sole reason for the universes existence."

    Though I am confident hotblack was trying to be sarcastic, he/she has accurately quantified the Christian position (which I do share). The entire purpose of all creation was to build a home for mankind. Were it not for man, there would be no creation. God will destroy it himself when Man’s purpose on this Earth is finished, so there is no need to fear random extinction.

    However, there is no reason to believe that smaller, city-leveling meteors may not pose a credible threat between now and the "planned obsolescence" of planet Earth. Thus, Even ardent Christians and Creationists should see the value of this research.

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  9. 9. waferhead 2:31 pm 05/29/2010

    Actually, the basic design research on what’s needed to move even the largest asteroids was done decades ago…
    Unfortunately the project was killed.

    http://www.oriondrive.com/

    Perhaps it needs another look as a planetary defense project?

    Link to this
  10. 10. jack.123 11:02 pm 05/29/2010

    The key word here is to be ready.A bury your head in the sand attitude simply won’t cut it with an asteroid problem.you simply can’t wish them away as some seem to think so,and it would appear that some these people are in congress considering that they just cut the funds to hunt for these kind of objects,which in fact was a very small amount money when you think about what a huge risk even a small asteroid would be.The money for an on going search would be a wise investment in mankind’s future.If anybody thinks otherwise they need only look at the dinosaurs,O thats right there aren’t of them left to look at,because an asteroid they didn’t see coming took them out.Of course they only had brains the size of peas,and couldn’t prevent their extinction.Once an Earth crossing asteroid is found,then use the the minimum amount of force necessary to get the job done at the greatest distance away as possible to deflect or destroy it should be done.If that means a nuke then we must plan on the safest way we can to deploy one.Just saying no to using one when it is needed and allowing an impact,unless it is very small would be one of the stupidest things congress has ever done.Let’s hope this isn’t the case.

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  11. 11. mj111 5:20 am 06/2/2010

    Maybe 1000 nukes detonating against the asteroid might obliterate it or make it less threatening. It would be a big win for nuclear disarmament.

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  12. 12. blakley52 7:14 pm 06/3/2010

    "and a giant fallout cloud from a nuclear attack. …" Huh? Please tell me how a fallout cloud from a nuclear blast <insert HUGE distance here> would have enough mass,and enough velocity to burn through a rather dense atmosphere.

    Mention nuclear and people just go ape****. Why? If it works it works. It’s a bit disturbing that there seems to be an anti-science trend going on in America (and probably the world). Pick religous zealot of choice…"science is bad, knowledge is bad, if god wanted us to know all of this stuff we would not be bothered with all that pesky learning". I’ll stop now. I am getting scared.

    Jim

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