Why do killer asteroids fascinate us?

By Phil Plait | March 8, 2009 8:00 am
Artist drawing of an asteroid entering Earth’s atmosphere

Why are we so hung up on killer rocks from space? I can think of lots of answers to that question: we’re fascinated by disaster in general, asteroid impacts are very dramatic and scary, they’re associated with dinosaurs (which are also cool), and so on.

With the near passage of the tiny asteroid 2009 DD45 the other week, the New York Times asked several scientists and science writers what they thought about this question. The answers, in the form of pretty interesting essays, are now online. The people they asked include Neil deGrasse Tyson, Don Yeomans, Seth Shostak, and Carolyn Collins Petersen… and if you follow me on Twitter, you may know C2P. At the very least you should be reading her blog, The Spacewriter’s Ramblings.

CATEGORIZED UNDER: Astronomy, DeathfromtheSkies!

Comments (127)

  1. They didn’t ask YOU?! You have a whole chapter in a best selling book about this very subject!

    Sadly the page is blocked, so I can’t see it right now. Although, one of my personal hypotheses about why we are so fascinated by this scenario is that it’s one of the few end of the world as we know it scenarios that we can actually DO something about if we actually put our minds to it.

  2. *shrug*

    I’ve always been fascinated by disasters myself. I had a wonderfully memorable plane trip where I happened to sit next to someone who was equally interested, and we talked disasters for a good while! What was funny was talking about famous plane disasters and keeping our voices down about it! :)

    So I’d have to say that people are fascinated by disasters in general.

  3. IVAN3MAN

    Er… “readinmg” her blog, Phil?

  4. Thanks for the shout-out Phil.

    Larian, I didn’t know who else they asked to answer the question they put to all of us — I got the question late Thursday and had to give them 300 words by 1o a.m. Friday. I made sure to include a link to Phil as well as others who ran with the story about 2009 DD45 — which the editors appreciated. I could have written a chapter, too! It pleased me to see a thorough discussion from Don Yeomans (clearly they gave him more space to expound)… that sort of thing is important for people to understand.

    CC

  5. IVAN3MAN

    Dr. Phil Plait:

    Why are we so hung up on killer rocks from space? I can think of lots of answers to that question: we’re fascinated by disaster in general…

    It’s probably the same reason why people have a morbid fascination of car crashes! That’s why people go to watch car racing — such as NASCAR, Indy 500, and 24 hours of Le Mans — not to see the race itself, but to see a bloody car crash!

    Yeah, I know, I’m a cynical bastard!

  6. I wish that CENTAF would allow me to go to your page CC. Sadly, the AF thinks it’s too educational (seriusly, that is the tag that it’s blocked for!).

    I wonder if they DID ask Dr. Plait, and he busted the 300 word limit with puns? :P

  7. Larian,

    So, if I changed it to “pr0n” they’d let you see it? ;)

    Seriously, that’s whacked. I wonder if it’s because I got political on one of my entries?

    CC

  8. Sundance

    @Larian

    Actually I’d say the opposite. Killer asteroids are one of the few end-of-the-world scenarios we CAN’T do anything about. Global warming we are aware of, we know what to do to slow and stop it, and we have the technology to do so. Nuclear disarmament is entirely achievable. We may not have the political will to avoid nuking ourselves or stop trashing the biosphere, but they’re entirely tractable problems none-the-less, and we can see them coming. We can also be pretty certain there are no gamma-ray-bursts or supernovae waiting to go off in our part of space any time soon. Despite scare stories about bird flu, people are probably justly confident in the ability of medical science to create new antibiotics fast enough to prevent a true wipe-out-the-whole-human-race-or-turn-us-into-trout-craving-zombies pandemic. But a big rock could thump us before we even knew it was there. Once we can detect-and-deflect, people will probably find asteroids a whole lot less interesting.

  9. Sundance, very true. I notice in the comments on the NYT site that at least one person brought up the “why don’t we nuke ‘em when they’re on the way in?” scenario. That’s, of course, an easy scenario to TALK about, but not so much from the physics end of things. If you think about it for a while (and Phil talks about this in his book), just nuking the rock doesn’t solve Problem A very neatly at all AND escalates the whole thing into Problem N^n numbers of bodies to deal with. Not pretty at all.

  10. Good points Sundance. Although, I contend that IF (and that’s a mighty big IF) we put our minds to it, we could be much better protected form any potential asteroid impact than we currently are. No one has got off their keister to REALLY do anything about it (i.e. lack of political will as with the nukes and climate change). Sure, there is the asteroid tracking project, but that’s only a small part of the picture. Didn’t Death From The Skies cover how to mitigate asteroids? Or am I confusing it with something else?

    CC, there seems to be no rhyme or reason to what they block and what they allow. Situation Normal, All Fouled Up. I had my wifes portfolio blocked because it was labeled as “Art”! :|

  11. Given enough warning, there are the gravitational tug ideas that are much neater, not to mention an ablation idea that I saw. Thse are just two off the top of my head. Neither of which are incredibly complex ideas, we just need to be able to SEE them, and then we need to refine current technology.

  12. IVAN3MAN

    Larian LeQuella:

    [T]here seems to be no rhyme or reason to what [CENTAF] block and what they allow.

    Does that include your e-mails, Larian?

  13. Depends IVAN3MAN. If you send one to my mil address, if it has attachments, some may get blocked, others may not. Again, no rhyme or reason. So far I have not seen my personal email get blocked though (at least I am still getting spam for various supposed failings in my anatomy or social life).

  14. IVAN3MAN

    @ Larian LeQuella,

    Hmm… it appears that the Freedom of Information Act does not apply to US Military Personnel, then?

    As for “spam”, I never get spam of any kind. That’s because I’m careful as to whom I divulge my e-mail address(es) to. ;-)

  15. T_U_T

    just nuking the rock doesn’t solve Problem A very neatly at all AND escalates the whole thing into Problem N^n numbers of bodies to deal with.

    Well. I am not buying this.
    100 megaton nuke is enough to smash a few kilometer sized crater into solid rock. 10 km comet composed of little more than dirty ice would be completely pulverized.

  16. @Larian LeQuella:

    Ever heard George Carlin’s favorite oxymoron?

    Military Intelligence?

    /blocking off

    J/P=?

  17. Greg in Austin

    T_U_T said,

    “100 megaton nuke is enough to smash a few kilometer sized crater into solid rock. 10 km comet composed of little more than dirty ice would be completely pulverized.”

    Do you have data to back up your claim? Please show us your calculations.

    8)

  18. Gary Ansorge

    I note that Boeing has a 25 kw solid state laser, scalable(they think) to 100 kw. Just the thing to ablate the leading edge of a tumbling rock and slow it down. Of course, that only works if we have a significant presence in space and a LOT of lead time,,,
    ,,,but it should work well for slowing our space debris.

    Interest in space rocks,,,hmmm, might be a residue of the survival instinct, in which we’re ready to jump at the slightest rustling of leaves, which might denote a predator hunting us. Oh, Wait. We killed all those critters(well, mostly).

    I think we really miss being challenged by competitors so, LOOK TO THE SKY, LUKE. The farce will get you if you don’t look out,,,

    GAry 7

  19. Why are we so hung up on killer rocks from space?

    Bruce Willis as Harry Stamper.

  20. Reed, I think Liv Tyler did a lot more for me than Bruce. ;)

    John, George Carlin was my all time favorite comedian!

    Gary, there are quite a few other companies that have a lot of Solid State Lasers that can scale upwards of 150kW if their projections are right.

  21. T_U_T

    Do you have data to back up your claim? Please show us your calculations.

    it is not my calculations. Just fidle here a little with parameters to get 100 megaton blast to see how big the crater would be.

  22. llewelly

    Sundance:

    Killer asteroids are one of the few end-of-the-world scenarios we CAN’T do anything about.

    That does not need to remain true. The physics are well understood, and we definitely have the the technology to fly a probe to anything likely to hit, assuming it is spotted. It’s just a matter of figuring out the details. Some experts have argued asteroid diversion capability could be developed and deployed in as little as 15-20 years. (In time for the second near miss of 99942 Apophis.)

    Sundance:

    Despite scare stories about bird flu, people are probably justly confident in the ability of medical science to create new antibiotics fast enough to prevent a true wipe-out-the-whole-human-race-or-turn-us-into-trout-craving-zombies pandemic.

    Antibiotics? Bird flu is a virus. Antibiotics wouldn’t help any. Bird flu requires anti-virals, vaccines, and quarantines, and most of all, preparedness for basic health care on a massive scale. In any case – no responsible scientist is expecting an end-of-the-world scenario from bird flu. A re-run of 1918 seems to be what most are projecting. That was rough, but civilization survived.

  23. José

    just nuking the rock doesn’t solve Problem A very neatly at all AND escalates the whole thing into Problem N^n numbers of bodies to deal with.

    Duh. You just have to send up even more nukes to get all the little pieces.

  24. QUASAR

    Right now, the greatest dangers to humanity are right here on Earth not out there in space!

  25. Statistically speaking within our lifetimes, I’d say you are correct QUASAR. ;) But it would be nice to be ready for that longshot. Maybe that longshot project will gat us silly hairless apes to actually work together on a global scale? I know, I need to take those rose coloured glasses off.

  26. Personally I’m not worried about asteroids. I have faith that Bruce Willis will always deflect them…. Accompanied by a killer soundtrack, of course.

  27. Sundance

    @llewelly: “Antibiotics? Bird flu is a virus. Antibiotics wouldn’t help any. Bird flu requires anti-virals, vaccines, …”

    Yes, you’re quite right, my bad, serves me right for posting while in a hurry. Still, I think my point stands, most people aren’t fascinated by the threat of a pandemic in the same was as a big rock from space because they expect medical science to be able to do something about it. Plus plagues don’t make spectacular fireworks.

    @T_U_T, blowing a big rock into lots of pieces doesn’t make the pieces vanish. Conservation of mass, old chap. Blow an asteroid to smithereens and the total mass (and hence, kinetic energy) of the smithereens is the same as for the original, intact, rock. Even if all the bits burn up in the atmosphere, they’re still depositing energy into the atmosphere by doing so, and hence heating it up – by the same amount that the Great Big Rock(tm) would have heated the atmosphere/ocean/crust. Either way, the end result is still a sizeable “boom!”

    Of course, we could develop ways to safely deflect them – and when we do we’ll stop being fascinated by them.

  28. T_U_T

    @sundance

    this is not true. Lots of the fragments would be kicked sideways and you don’t need much deltaV to miss the earth altogether.
    The center of mass of the fragment cloud would not move that much. and most probably pass through earth, but, center of mass is not a thing that can really hurt if there is no actual mass around to hit you.

  29. IVAN3MAN

    @ T_U_T

    You’re forgetting Sod’s Law, which states: The degree of failure is directly proportional to the effort made and to the need for success.

    See SNAFU.

  30. T_U_T

    The degree of failure is directly proportional to the effort made and to the need for success

    so what do you think we should do ? Just stay at home and not even try ? Well. That worked really well for the dinosaurs ;)

  31. IVAN3MAN

    @ T_U_T,

    The point that I was trying to make was that things don’t always go according to plan. You made the often proposed suggestion of firing nuclear missiles at the oncoming asteroid to vaporize all or most of it. If not completely vaporized, the resulting reduction of mass from the blast combined with the radiation blast and rocket exhaust effect from ejecta could produce positive results. However, the largest problem with using nuclear weapons* is that if the asteroid is composed of dense rock, it will break into fragments and any fragment larger than 35 m across would not burn up in the atmosphere and itself could impact Earth. Tracking of the thousands of fragments that could result would prove daunting. Furthermore, some asteroids are composed of solid iron/nickel which would be highly resistant to being blown apart, let alone being vaporized.

    Another proposed solution is a form of nuclear pulse propulsion*, which involves detonating a series of smaller nuclear devices alongside the asteroid, but far enough away as not to fracture the object. Providing this was done far enough in advance, the relatively small forces from any number of nuclear blasts could be enough to alter the object’s trajectory enough to avoid an impact. The problem with this is that most of the energy — in the form of gamma-rays — from the thermonuclear device would be wasted because it would be radiated in all directions, with most of it going into deep space instead of directly at the asteroid/comet.

    A Kinetic Impactor* is an alternative means of deflecting an asteroid, which is attempting to directly alter its momentum by sending a spacecraft to collide with the asteroid — like the Deep Impact mission on Comet 9p/Tempel in 2005, but with a heavier projectile.

    The European Space Agency is already studying the preliminary design of a space mission able to demonstrate this futuristic technology. The mission, named Don Quijote, is the first real asteroid deflection mission ever designed.

    In the case of 99942 Apophis, it has been demonstrated by ESA’s Advanced Concepts Team that deflection could be achieved by sending a simple spacecraft weighing less than one tonne to impact against the asteroid. During a trade-off study, one of the leading researchers argued that a strategy called “kinetic impactor deflection” was more efficient than others.

    Another major alternative to explosive deflection is to move the asteroid slowly over a time. A gravitational tractor* is a way to use the gravitational attraction between a seriously heavy spaceship and an asteroid to modify its trajectory to prevent it from colliding with the Earth. The spacecraft and the asteroid mutually attract one another. If the spacecraft counters the force towards the asteroid by, e.g., an ion thruster, the net effect is that the asteroid is accelerated towards the spacecraft and thus slightly deflected from its orbit. The thrusters must not point directly at the asteroid, but angled at 45 degrees, else the effect would be voided by momentum transfer between exhaust gas and the asteroid’s surface. While slow, this method has the advantage of working irrespective of the asteroid composition or spin rate — rubble pile asteroids would be difficult or impossible to deflect by means of nuclear detonations while a pushing device would be hard or inefficient to mount on a fast rotating asteroid. However, a gravity tractor would likely have to spend several years beside the asteroid to be effective.


    *Sources: Wikipedia — Asteroid Deflection Strategies (click on my name for the link); Nature; NASA; ESA. :cool:

  32. ADDENDUM: Sorry, I forgot to provide a link to the above mentioned Wikipedia article — you can click on my name now.

    Man, I need a coffee break!

  33. T_U_T

    If the asteroid is far enough, any strategy would work. Whacking the asteroid to pieces will spread the debris cloud so much that at most a few small fragments would hit earth ( if not stopped by other means ). Pushing it will also work because it has enough time to accumulate deltaV.
    An asteroid close enough to hit even if blasted to millions of pieces would hit anyway because no other means can provide so much impulse in such short time.
    In between there is a distance where pushing an asteroid would not cause it to miss but a gigaton explosion would still blast most of the asteroid mass off the course. Some fragments would hit, of course, but given choice between say one 20 km sledgehammer or say 4 x 200 m fragments I would choose the latter.

  34. T_U_T

    And, also, counter intuitively, the looser the asteroid is, the bigger hits it can sustain without breaking apart
    so, loose asteroid would not fall apart at all, iron asteroid would not fall apart either, albeit for different reasons. Only middle strength asteroids would break apart, yielding only few big fragments which can be tracked and the process repeated as necessary. The only way how an asteroid could end in thousands 35 m big fragments is if someone carefully prefragmented it on purpose.

  35. T_U_T

    moderation sucks. At least one link per comment should be allowed without need of moderation

  36. T_U_T

    just did some quick calculations and found out that just 2 gigaton explosion inside a 20 km homogenous iron asteroid would overcome its gravitational binding energy and kick almost all of its mass off the path by 2m/s so that it would miss even if blasted TWO MONTHS prior to collision.
    That is 20 km of pure iron heading for an bulls eye hit. Pretty much the worst case scenario. There is no way to achieve such last-ditch rescue by other means. In case of a smaller rocky asteroid a few years away, there would be almost certainty that no big fragment will hit earth at all. And int he unlikely case the whole thing can be repeated, this time with much less asteroid mass left.
    Also, we already have all the tech to put together a multi gigaton nuke ( just scale up the tsar bomba ) and all other technologies are not developed or tested at all.
    Simply put, I see no reason to pursue other means than nuclear except perhaps the lingering nuclear phobia left by cold war and Chernobyl. But that is obviously not a rational objection.

  37. amphiox

    T_U_T:

    If the asteroid were detected late, and we had very little time, I think we WOULD nuke it with the biggest bomb we could manufacture in time and pray for the best.

    But I think the major problem with the bomb solution is simply the inherent unpredictability. Without very detailed information on the impactor’s trajectory, spin, composition, shape, etc, we wouldn’t be able to determine with any confidence how large we have to make the bomb, where on (or near) the impactor to aim it, or what will happen after we detonate it. And if we had the time to gather the pertinent information, then we’d have enough time not to need the nuclear option.

    Situations with rubble pile asteroids simply absorbing the explosion, or iron asteroids fragmenting and shotgunning us, or deflecting successfully only to have the impactor come back and hit us again in another few years have already been discussed by others. To those I would also add the scenario of a medium sized impactor that won’t do global devastation, just widespread regional destruction. Say it’s heading for Kansas, and the U.S nukes it and deflects the orbit, but it turns out not to be enough, so it impacts Russia or China instead, or lands in the Pacific and devastates all the coastal areas. Think of the diplomatic ramifications of that.

    Now as there is no theoretical upper limit to nuke yield, we could design a nuke so big that it would guarantee deflection of any asteroid of any composition and any size, in any time frame, but the power of such a weapon would very quickly reach a level where the existential threat of possessing the bomb itself becomes greater than the threat of any potential asteroid, short of something the size of Ceres capable of sterilizing the planet to a depth of 3 or 4km.

  38. Thanks for the detailed explanations Ivan3man and amphiox… I was sort of hoping T.U.T. would go look things up so we wouldn’t have to do the homework for him/her/it. The unpredictability factor in sending a nuke to smack a plug of iron is huge. A lot of people have worked on the problem and the best they can come up with are several “best case” scenarios (that is, if everything is perfect, what I like to think of as the “spherical cow” approach) and a lot of more realistic scenarios. Ivan3Man you supplied a good summation and link — T.U.T you would be best served by reading some more about what has been discussed and rejected before you flip off the old “send up a Nuke” solution that usually works better in the movies than it probably would in reality.

  39. T_U_T

    first. I looked those things up. Really. There is simply no other way that could produce comparable amount of thrust than nuclear explosion. Either One big, or, more preferably dozens, each only a fraction of binding energy of the asteroid, so that it would hold together even if fractured.
    Most of asteroids show impact craters caused by multi megaton impacts, so, they would likely survive moderate sized nukes as well.

  40. José

    just did some quick calculations and found out that just 2 gigaton explosion inside a 20 km homogenous iron asteroid would overcome its gravitational binding energy and kick almost all of its mass off the path by 2m/s so that it would miss even if blasted TWO MONTHS prior to collision.
    Show your work! I noticed you said “inside”, as well. Do you mean alongside? Or are we back to sending up Bruce Willis to drill for oil?

  41. José

    Woops. I can’t spell blockquote. This is what I meant.

    I just did some quick calculations and found out that just 2 gigaton explosion inside a 20 km homogenous iron asteroid would overcome its gravitational binding energy and kick almost all of its mass off the path by 2m/s so that it would miss even if blasted TWO MONTHS prior to collision.

    Show your work! I noticed you said “inside”, as well. Do you mean alongside? Or are we back to sending up Bruce Willis to drill for oil?

  42. T_U_T

    simply put numbers into gravitational binding energy E = density^2 * R ^ 5 * g * 32 / 15 * PI^2 = 6.4e7*1e20* 6.67e-11 * 21 = 1e18 J << 2 gigaton = 1e19 J
    .
    quick estimation deltaV= sqrtf(2*E*Me)/Ma where E is energy of explosion, Me is the ejected mass and Ma is the mass of the asteroid. Me may be estimated by the mass of iron liquified by 1e19 J of energy. assume thermal capacity 500J/K and temperature 2000k you will get 1e13kg of molten iron, also, quick estimate, the blast would tear apart the twice the amount of material because the explosion would happen inside the asteroid,
    so, sqrtf(2*2*1e19*1e13 ) / (4/3*8000*PI*1e12)=2e16/3.2e16 = 0.8m/s ( no clue why I computed 2 the first time ).
    .
    to miss half earth diameter 63780000/0.8/86400 = 92 days
    .
    also, to fully contain the blast would require ( 2e13 / ( 4/3 PI 8000 ) ) ^1/3= 854 m so, drilling ~1km into the asteroid would be needed adding further few months time.

  43. Greg in Austin

    T_U_T said,

    “it is not my calculations. Just fidle here a little with parameters to get 100 megaton blast to see how big the crater would be.”

    That’s great. You’ve just blown a giant crater into a giant asteroid or comet. What happens to the ejecta?

    8)

  44. Greg in Austin

    T_U_T said,

    “In between there is a distance where pushing an asteroid would not cause it to miss but a gigaton explosion would still blast most of the asteroid mass off the course. Some fragments would hit, of course, but given choice between say one 20 km sledgehammer or say 4 x 200 m fragments I would choose the latter.”

    If you blow apart a 20km diameter object into 4 equal pieces, they would be 5km in diameter, not 200m. If your pieces were 200m in size, then there would now be 100 of them. So, instead of hitting one target on the earth, you’ve now caused 4 targets to get hit, or worse, 100 targets.

    Even if half of the pieces miss the earth on this orbit, how do you know they won’t hit on the next orbit?

    8)

  45. T_U_T

    That’s great. You’ve just blown a giant crater into a giant asteroid or comet. What happens to the ejecta?

    They would have enough speed to be ejected from the solar system altogether.

  46. T_U_T

    Even if half of the pieces miss the earth on this orbit, how do you know they won’t hit on the next orbit?

    If only half of the pieces would miss it would be almost worthless. The point is that almost all of the pieces would miss. Also, their trajectory would return them to the point of explosion, which would be far from earth orbit, so they would no longer cross earth orbit at all.
    And the few that would, would do it at different times so, it would buy us some time to nuke them too..

  47. IVAN3MAN

    @ T_U_T,

    According to the following transcript extract from Chapter #7: Stopping an Asteroid from Hitting Earth video (click on link), Dr. Neil deGrasse Tyson has your number:

    Actually, there are two camps out there; there’s the… [macho-man posture and voice] “let’s blow the sucker out of the sky”, there’s those fellows, we’ve met them, we know who they are, [macho-man voice] “We’ve got the nukes, let’s open the silo; take it out”.

    Now, it turns out that we, particularly Americans, are very good at blowing stuff up. We’re less good at understanding where the pieces go after it blows up! O.K. That’s just the nature… that’s just how that works. SO, if you want to blow up the asteroid and you, let’s say, you hit it with the nuke and then it splits into two, now you have to evacuate two places, on Earth, instead of just one. You know, you gotta, like, if you blow, you have to go to smithereens so they burn up in the atmosphere, but you have no guarantee of that, because we don’t guarantee of what the stuff looks like after it blows up. So…

  48. Greg in Austin

    T_U_T said,

    “They would have enough speed to be ejected from the solar system altogether.”

    That sounds unlikely. How did you determine this?

    and

    “The point is that almost all of the pieces would miss.”

    I was hoping you would show some examples of how you calculated this, including the mass of the object, the speed of the object, the mass of the projectile, the time of impact, the orbital trajectories, etc.

    Don’t get me wrong, if what you claim were as easy as you say, then that would be great. However, why do all the physicists and other scientists who actually study this for a living say right off the bat that nuclear weapons are absolutely not the right thing to use?

    8)

  49. IVAN3MAN

    ERRATUM:

    @ T_U_T,

    According to the following transcript extract from Chapter #7: Stopping an Asteroid from Hitting Earth video (click on the link), Dr. Neil deGrasse Tyson has your number:

    Actually, there are two camps out there; there’s the… [macho-man posture and voice] “let’s blow the sucker out of the sky”, there’s those fellows, we’ve met them, we know who they are, [macho-man voice] “We’ve got the nukes, let’s open the silo; take it out”.

    Now, it turns out that we, particularly Americans, are very good at blowing stuff up. We’re less good at understanding where the pieces go after it blows up! O.K. That’s just the nature… that’s just how that works. SO, if you want to blow up the asteroid and you, let’s say, you hit it with the nuke and then it splits into two, now you have to evacuate two places, on Earth, instead of just one. You know, you gotta, like, if you blow, you have to go to smithereens so they burn up in the atmosphere, but you have no guarantee of that, because we don’t guarantee of what the stuff looks like after it blows up. So…

  50. Cheyenne

    @Greg – But what else can we do? Let’s say a rogue comet suddenly comes in that caught us completely by surprise. We suddenly find out that we have 3 months to do something before impact. The only thing I know that is available to us today would be to try to launch a series of thermo-nukes at it. We can’t do the gravity tug or the nudge by laser or whatever.

    Brute smash up is the only thing we can do today as far as I know. It’s not ideal but there isn’t anything else available.

    I think we can all agree that we need to spend some more money looking out for this stuff and funding ways to deal with the next impact.

  51. IVAN3MAN

    Phil Plait, my two attempts to post a comment above with links (currently “awaiting moderation”) have both resulted in SNAFU. For some unknown reason, the system there at Discover is screwing-up the bloody URL! So, you might as well delete them.

  52. Gary Ansorge

    Three months warning is just enough time to bend over and kiss it goodbye,,,

    Gary 7

  53. IVAN3MAN

    ERRATUM II:

    @ T_U_T,

    According to the following transcript extract from Chapter #7: Stopping an Asteroid from Hitting Earth video (click on the link), Dr. Neil deGrasse Tyson has your number:

    Actually, there are two camps out there; there’s the… [*macho-man posture and voice*] “let’s blow the sucker out of the sky”, there’s those fellows, we’ve met them, we know who they are, [*macho-man voice*] “We’ve got the nukes, let’s open the silo; take it out”.

    Now, it turns out that we, particularly Americans, are very good at blowing stuff up. We’re less good at understanding where the pieces go after it blows up! O.K. That’s just the nature… that’s just how that works. SO, if you want to blow up the asteroid and you, let’s say, you hit it with the nuke and then it splits into two, now you have to evacuate two places, on Earth, instead of just one. You know, you gotta, like, if you blow, you have to go to smithereens so they burn up in the atmosphere, but you have no guarantee of that, because we don’t guarantee of what the stuff looks like after it blows up. So…

  54. T_U_T

    @greg in austin.
    Look at my first link. and insert such numbers that the result is a 2 gigaton explosion. It will compute ejecta velocities.
    The second question is tougher. You can imagine the asteroid exploding as a spherical shell of matter at nine times the escape velocity of the asteroid because the blast is order of magnitude higher than its gravitational binding energy. After several months it will so big that the cylinder that earth sweeps will be filled with only a fraction of the whole mass.
    .
    Also, I would like you to provide some links to those physicists that study the thing for their living that reject the idea right off the bat. Something more sophisticated than my back-on-the-envelope calculations that shows where I actually made a mistake. I do NOT claim I am right, I just say that I can not rejet the idea right from start by my, I freely admit, simplistic maths.

  55. T_U_T

    SO, if you want to blow up the asteroid and you, let’s say, you hit it with the nuke and then it splits into two, now you have to evacuate two places, on Earth, instead of just one.

    if the asteroid is just a few kilometers big the only place you could evacuate to is mars. And to make an asterod split into two parts so that one hits mars and the other hits earth well, with so much bad luck you you should better kill yourself right now ( not really, if you had that much bad luck, you would most likely fail and end up horribly mutilated instead of dead ;) )
    .
    Also, there is no reason to actually to blow the asteroid to pieces. Just take a look at the asteroid, take the biggest crater, and use nukes half the size. There is no way to provide comparable amount of thrust to this quick and dirty nuclear pulse propulsion

  56. Greg in Austin

    @T_U_T,

    I don’t see where in your back-of-the-envelope calculations you take into account the orbits of the planets, the trajectories of the earth and the object you want to destroy, or any of the other major factors that determine where the object is coming from, or where any pieces of it will go. You simply say that a nuke will blow the thing into pieces.

    The link you provided earlier (“Computing Effects of an Impact on Earth”) does not calculate the effects of nuking an asteroid in orbit around the sun. Nowhere in its documentation does it mention striking an object with a warhead, and nowhere does it mention the escape velocities of the solar system. So please, if you have any other data or calculations that simulate a nuclear strike on an asteroid or comet on an impact trajectory with Earth, please provide it.

    8)

  57. Greg in Austin

    Cheyenne said,

    “But what else can we do? Let’s say a rogue comet suddenly comes in that caught us completely by surprise. We suddenly find out that we have 3 months to do something before impact.”

    Actually, there have been cases recently where an asteroid was not seen until days before, or even AFTER it passed Earth. These objects were previously unknown, and came from the direction of the sun, making them nearly impossible to see. I’d say for objects 3 days-6 months away, the only thing we can do is determine the target area and evacuate.

    I’m not an expert in this field, but I have read many suggestions for moving any objects where we have enough time to do so. Solar sails, ION engines, gravity tugging, laser heating, etc. Unfortunately, all ideas for redirecting asteroids or comets are currently untested and unproven.

    I agree more money and research needs to be thrown at this, which is why we’re talking about it.

    8)

  58. amphiox

    Per my previous post, a 2 gigaton nuke such as mention by T_U_T would by itself be a bigger threat to the survival of humanity than all but the biggest asteroids.

    There is no doubt that the nuclear option is the easiest and fastest way currently available to deflect an asteroid. And it will most likely work. But there are big uncertainties involved regarding the aftermath, and the chance of catastrophic failure (scenarios whereby we end up doing even more harm than if we had done nothing at all).

    In the case of a really big asteroid with very little warning time, it’s a no-brainer that we’d be trying to nuke it. It’s not like dying twice is worse than dying once.

    But the point is, if we had to time to do it properly, we’d want to do it a controlled fashion, such that we’d know exactly where the asteroid gets deflected to. We’d want a zero chance of failure, and a zero chance of the asteroid in question ever threatening earth again, or as close to zero as we can make it. It would be a bonus if we could control the asteroid’s orbit so precisely that we could retain the option of making use of it later (ie exploration missions to it, mining it, maybe even using as a gravity tug for another bigger asteroid, etc).

    We could never do any of that with a nuke. It’s fine as an emergency stop-gap, but emergency stop-gaps are by their very nature wasteful and imprecise. Better to avoid the emergency altogether with early detection, and with early detection, I don’t see any scenario where a nuke would be the prefered choice over some other option.

  59. Greg in Austin

    T_U_T said,

    “Also, I would like you to provide some links to those physicists that study the thing for their living that reject the idea right off the bat.”

    Well, there are books by Dr. Neil deGrasse Tyson, Dr. Phil Plait, Carl Sagan, etc.
    Also, take a look in any Physics textbook for details on orbital mechanics.
    There are hundreds of links on the web that are related. One of my favorites is
    neo.jpl.nasa.gov/links/

    8)

  60. IVAN3MAN

    @ T_U_T,

    Did you watch the video of Dr. Neil deGrasse Tyson that I have provided (eventually!) via a link in my post above? He said that they have “top people” working on this problem. If you think that you can do better, then why don’t you offer them your services(?).

  61. T_U_T

    @amphiox
    this is just the nuclear paranoia I’ve been talking about. there is just NO way to accidentally trigger a multi gigaton nuke if the primary is placed only few minutes prior to the actual explosion. Just no way. If the explosive lens of the primary is not triggered in just the right way, no nuclear explosion happens at all. If the primary is ignited prior to insertion in the main part, only a few kiloton blast will happen.
    Only after activating the primary, placing it correctly inside the device, removing safety mechanisms, and triggering it with extreme precision you would get the full blast. SO, just let one country build the secondary and launch it separately. Other country to build the primary and the two parts merge only at safe distance form earth and there is no way it could harm earth other than two governments deliberately working together to commit suicide. Which is, I think, completely implausible because they wanted, they would destroy themselves even without such showdown.

  62. T_U_T

    Man, greg, as if I didn’t know about that stuff gfor years….

  63. T_U_T

    IVAN3MAN, too much words, but precious little more than his word to back it up. I at least tried to do some math to show my point. No such thing from the other side, just arguments from authority.

  64. Greg in Austin

    @T_U_T,

    You’re making the claim, you should back it up with data. Again, the only calculations you provided did not take all elements into account, and the only link you provided was to a software tool that was not designed to solve this particular problem.

    Your math up above says,

    “quick estimation deltaV= sqrtf(2*E*Me)/Ma where E is energy of explosion, Me is the ejected mass and Ma is the mass of the asteroid. Me may be estimated by the mass of iron liquified by 1e19 J of energy. assume thermal capacity 500J/K and temperature 2000k you will get 1e13kg of molten iron, also, quick estimate, the blast would tear apart the twice the amount of material because the explosion would happen inside the asteroid
    .
    to miss half earth diameter 63780000/0.8/86400 = 92 days
    .
    also, to fully contain the blast would require ( 2e13 / ( 4/3 PI 8000 ) ) ^1/3= 854 m so, drilling ~1km into the asteroid would be needed adding further few months time.”

    So, I see 2 major flaws with this method. 1) You have to drill 1km into an asteroid, which has never been done except in science fiction, and 2) you have a mass of liquid iron instead of solid iron, which will still rain down upon the planet.

    If you don’t have data to back up your claim, just say so. Do you have a computer simulation of an asteroid 20km in diameter, of a guesstimated density, on a collision course with Earth, being hit with a nuclear warhead of known energy output, at an estimated orbital distance? If not, then you are only guessing at the expected outcome.

    8)

  65. T_U_T

    @ greg. the nuke provides 10 times the binding energy, so we can assume the fragments will fly off with sqrtf(10-1)=3, say 2 times the escape velocity which for a 20 km iron ball is 30 m/s so we have 60m/s expanding sphere of debris. after 90 days it will have 60 * 90 * 86400 = 1000000km so the amount of debris hitting earth would be 0.06 % of the original mass.

    That is the first pass. Then the debris cloud would expand into a torus along the orbit of the asteroid, 30 m/s = cca 0.1 % of the asteroid speed, so the torus would have 0.2% of the orbit distance , say 5 mil km. The earth will pass each year through it, but it will take decades to actually hit a large chunk because the orbits would have different period, so it would definitely buy some time to get rid of the rest of the debris.

  66. T_U_T

    @greg, I am trying as hard as I can type.
    I have provided at least a partial estimate. The other side didn’t provide anything yet. I think it is definitely unjust to demand victory by default by you.
    And also, your objection 2 is invalid. The iron would not be only molten. It would be shock-compressed and blasted into space at the speed of sound in iron, which is in order of a few km/s, explosions simply work that way. At that speed it would miss earth completely.

  67. T_U_T

    the only valid objection is 1km drill. which is with current technology no problem at all. We dug several kilometers in deep in the ground, and there is almost no gravity, so no need to lift debris from the drill . just dig one big tunnel and place the nuke at the end of it.

  68. T_U_T

    Also, one thing. 20 km iron asteroid is pretty much the worst case scenario. The usual scenario for gravitational tractor and similar stuff is < 1km of low density rock. Multigigaton nuke would destroy such asteroid with like six orders of magnitude safety marigin. There would be nothing left, just dust and high temperature plasma cloud. Asteroid like that could be safely disposed of by just a few dozen off the shelf tactical nukes so that no explosion would exceed the gravitational binding energy of the asteroid, so it would be just kicked aside by few cm/s each hit. Without the need to build exotica like huge ion engine powered nuclear spaceship.

  69. amphiox

    T_U_T:
    I’m not talking about accidentally triggering a warhead. I’m more concerned about someone deliberately triggering the warhead, among other concerns, when I say existential threat.

    We’re talking about a 2 gigaton nuke here, right? As in 2000 megatons? 20X bigger than the 100 megaton monster the Soviet’s claimed they could make, and 200X more powerful than the average nuke in the current US arsenal.

    First off, how long is it going to take to build such a thing, with current or near-future technology? If it’s going to take more than 3 or 4 months, then it’s not going to do us any good for that hypothetical big rock with minimal warning. And we’re going to have to test it, since we’ve never built any explosive that big. I presume that the diplomacy involving the international test ban treaty and the prohibition on nuclear weapons in space can be worked around in the face of an existential threat, but even so, where on god’s green earth do you propose for the test blasts?

    So maybe we build it beforehand, before we detect any asteroid, to make sure that it’s ready to go at the moment of detection, cause you never know, we might have only a month or two of warning, after all.

    So who’s going to build it? Who’s going to keep it? Will Russia be happy with the US building a 2000 megaton nuke? Would the US be happy with Russia having one? What about the Chinese? England and France? Israel? What kind of diplomacy would we have to envision to prevent a new arms race with 2000 megaton nukes?

    How long would we have to keep these things at the ready, launch systems impervious to failure or accident, and security impervious to terrorism or theft? It might be several centuries before we actually detect a threatening asteroid. Can you guarantee that in all that time, none of the governments in possession of these bombs will ever collapse, or become unstable, or fall victim to terrorists, or become embroiled in wars with one another? That no one will ever, ever be tempted or feel compelled to use one of these weapons on earth? Our current track record for keeping and not using nuclear weapons is only a bit over 50 years right now.

    Sure, all these scenarios can be mitigated against, but you can’t eliminate the risk entirely, and at a certain point, when the bombs get big enough, then the risk-benefit ratios of having and keeping such weapons in readiness versus the potential asteriod impact starts to favor just letting the asteroid hit.

    The nuke option only makes sense if it uses entirely pre-existing delivery systems and payloads, as an emergency contingency for that late detected asteroid that’s going to impact in a couple weeks to months. At any longer time frames, if any R and D and testing and manufacturing of bombs bigger or more capable than the current arsenal is involved, then we’d be better off spending the time and resources on non-nuclear options.

  70. amphiox

    T_U_T:

    With regards to your idea of having two nations build the primary and secondary separately won’t work because there are more than two nations on earth. Which two nations would it be? US and Russia? Would China accept that? Russia and China? Would the US accept that? Or maybe every single nuclear nation gets to make one component, all of which must be present before detonation can happen? We’re talking about a weapon system we can develop, build, and deploy quickly, as an emergency measure, here, right?

    And what would prevent a third nation from trying to figure out how to build both primary and secondary either by espionage or their own independent research efforts, once they learn that it can, in fact, be done? Or a third party from attempting to steal the two devices themselves? Keep in mind that we can’t have just one. There must be several. We have to test fire at least once, and we’ll need at least one more as backup in case the first one fails.

    (Hell, what’s to stop our two partner nations from spying on each other? They’d only have to steal the plans for one device, not two.)

    And don’t tell me you’re so naive as to believe that this scenario isn’t likely (guaranteed) to happen.

    Maybe we could have the devices built under the auspices of the United Nations, or something similar? Propose for me a realistic charter for a supranational organization impervious to manipulation by its more powerful members, and guaranteed to endure for a thousand years, and then we can talk.

  71. T_U_T

    first. Russians already have 100 megaton design ( they tested it deliberately weakened to 50 mt ) and scaling up 20 times is in principle just matter of making the secondary bigger. There would be no need to test it, because we have computer simulations, and, also, there would be no need to have the device fully assembled by one country. Most likely each russia, america, china, etc. would have only 1/3 of the actual device in disassembled state, so no one could actually use it even if he wanted. Also, a big bomb is actually less efficient than separate small warheads of the same sum yield. So there would be no real payoff to build it instead of 1000 small nukes. The only way that thing could come to use is each country launches its part which travels separately to the destination, and assembles itself only just before the explosion. If one country would really want to start nuclear holocaust, it would rather disassemble its part and use the material to make smaller nukes so, the Big One is not really an aditional risk to the nukes we already have aiming at us right now.
    Just as I have said. it is all just nuclear phobia.

  72. amphiox

    And one more thing. If the last fifty years of the history of nuclear weapons has any validity, then it should take about a century at the most conservative estimate for the plans for our 2000 megaton nuke, once developed, to be freely available on the internet, and the materials required to manufacture it to become cheap and plentiful enough for any tinpot dictatorship with a reasonable cash flow to contemplate building one. Maybe two centuries before a relatively large terrorist organization could contemplate the same.

    Maybe by then we’ll have universally available worldwide SDI, and the big nations will be threatening each other with antimatter plasma weapons. Or maybe not.

  73. T_U_T

    I have to repeat myself. 2 gigaton nuke would cause far less damage than the 20000 1 megaton nukes we have already in place. There is no military reason ( if one can call blowing up yourself with your enemy reason at all ) to have nuke that big. It would actually be less dangerous than the same of material distributed multiple small nukes.

  74. T_U_T

    and the materials required to manufacture it to become cheap and plentiful enough for any tinpot dictatorship with a reasonable cash flow to contemplate building one.

    this is perhaps the most ridiculous statement in this discussion. neither deuterium nor plutonium is going to be really cheaper mass production, and we already have significant amount of it. We already have the required amount distributed in several thousand nukes around the world. Did it become so cheap and available ? No. In fact even north korea had to produce it on its own.

  75. amphiox

    T_U_T:

    You may be right, in principle, but do you really think it wise to bet the existence of the human race on an engineering principle and just a computer simulation without an empirical test? I think in that scenario we would test it, or else we’d have at least two back-ups, just in case the computer simulation turned out to be wrong, or we did not foresee one of the relevant factors that needed to be simulated.

    And the whole point of the Soviets making that 100 megaton weapon was political, not military. 10 10 megaton weapons would have been more effect and less costly, but the people they wanted to awe and scare would have been less frightened of 10 smaller weapons.

    If we design the big bomb, someone will try to build it. Maybe not right away, maybe only a few decades later, maybe only after we use it for the first time successfully on some asteroid (there’d be no after if it wasn’t successful). But again, we’re talking a timescale of several centuries here. Someone, somewhere, sometime, will want to build it. Someone, somewhere, sometime, will succeed. And someone, somewhere, sometime, will try to use it. That much is guaranteed, unless humanity genetically engineers itself into a kinder, gentler, wiser species (and exterminates the old version) during the interim.

    It is not nuclear phobia. The biggest nuclear bomb is just a shiny metal paperweight without the human with his finger on the detonator switch. It’s human nature I am concerned about.

  76. amphiox

    And if there really is nothing special or different between a 2000 megaton nuke and 2000 1 megaton nukes, then the big one is not necessary and we shouldn’t waste the resources building it. We can achieve the same effect with 2000 1 megaton nukes, and we already have that in spades.

    It would just be a question of aiming and coordinating the missiles.

  77. amphiox

    T_U_T:

    Exactly. North Korea produced its own. And succeeded. Last I heard, North Korea is NOT a particularly wealthy or technologically advanced nation.

  78. T_U_T

    sorry but this is pure phobia. Someone Somewhere. Someone somewhere to cough up that much plutonium would need huge amount of resources. So huge that only a handful countries could have even in principle, and most of them are nuclear powers already.
    Also, north korea almost starved its population to produce just ONE nuclear test and even that was failure – it produced only fizzle yield. It would never be able to have more than just a handful of small warheads because plutonium decays and needs to be produced continuously to just maintain your arsenal.

    And if there really is nothing special or different between a 2000 megaton nuke and 2000 1 megaton nukes, then the big one is not necessary and we shouldn’t waste the resources building it. We can achieve the same effect with 2000 1 megaton nukes, and we already have that in spades.

    It would just be a question of aiming and coordinating the missiles.

    Exactly.

    It would just be a question of aiming and coordinating the missiles.

  79. Greg in Austin

    @T_U_T,

    I don’t recall this being a battle, nor do I recall claiming victory. I don’t even recall saying you are wrong. For all you know, I could agree completely with what you are saying.

    I simply asked you to back up your claims with data or evidence. Which… um… let’s see… you still haven’t provided. What I’d like to see is the actual calculations of blowing up an asteroid that is heading toward earth that would actually cause less damage than the asteroid itself.

    8)

  80. T_U_T

    You got an estimate. But you behave like the only thing that would suffice is detailed highly accurate computation. This is neither fair nor reasonable. Because I obviously lack both time and knowledge to do such tour de force to prove myself. And, because it is giving an unfair advantage to the ‘let it hit” option. Why should it have the benefit of doubt over ‘let’s blast it and hope for the best’ ?

  81. Greg in Austin

    T_U_T said,

    “Because I obviously lack both time and knowledge to do such tour de force to prove myself. And, because it is giving an unfair advantage to the ‘let it hit” option. Why should it have the benefit of doubt over ‘let’s blast it and hope for the best’ ?”

    Um, perhaps because the experts in the field have said over and over again, “blasting it with a nuke is not the correct course of action.” Now, they are entitled to their opinion, as are you. However, the scientists have real data to backup their claim, where you do not. Which one are you most likely to agree with?

    Given the choice, I’d pick the one with the most accurate data.

    That being said, I sincerely think we should continue to look for ways to prevent the inevitable impact.

    8)

  82. amphiox

    The advantage of nukes is that nothing else produces as much energy and force in as short a time, and we already have them available. So back in my first post on this subject I stated my opinion that the nuclear option was the best and possibly only option we had for emergency situation of late detection and short time to impact.

    But the disadvantage of nukes is that they are overkill, applying far more energy far more quickly than would actually be needed in many cases. And the extra energy just contributes to increasing the entropy of the system, making the aftermath harder to predict. Because in the ideal scenario we wouldn’t just want to kill the offending asteroid, we’d want to control it in such a way as to ensure it will never again be a threat, and keep it as a resource we could exploit later.

    What I think is dangerous is devoting time and resources to developing and enhancing new nuclear systems not currently in existence just as a prophylaxis against the asteroid threat. Some of the things I could easily envision us trying to do in that case would include:
    1. increasing the yield of the bomb so you could get a bigger explosion with less reaction mass. This would let us launch a lighter bomb on a bigger missile, with a increase in range so we could hit the asteroid while it is farther away.
    2. increasing the efficiency with which we can manufacture the weapons-grade fissile material, so we could make more cheaper and faster, allowing us to manufacture the bomb in less time, giving us a greater window in which to plan the interception itself
    3. finding new sources of the fissile material from previously inaccessible places that we couldn’t mine from before, and making the extraction from those places economically feasible
    4. developing alternate methods of triggering the fusion reaction for the H-bomb that would require less fissile material, or even none, reducing or obviating the requirement for assembling a sufficient quantity of fissile material in the first place. (If you could find a way to start the fusion reaction without using a fission primary, you could make an H-bomb with just water.)

    All these technologies would remove technical and engineering barriers to manufacturing nuclear arms in large quantities. Developing any of these would make it easier for future rogue states and terrorist organizations to make big bombs of their own. It is this kind of research program that I refer to as eventually reaching a scale in which it starts to pose an existential threat that becomes actually greater than the asteroid threat.

    And of course such a research program takes time, which negates the primary advantage of the nuclear option, namely that it is quick and we already know how it works.

    So I’m all for developing contingency plans whereby we could quickly turn our existing nuclear arsenal into an anti-asteroid system, whether it involves coordinating a multiple missile strike, or assembling a bunch of pre-existing warheads onto a single rocket, and even building an extraterrestrial launch site, in orbit or on the moon, or at a Lagrange point if that was thought necessary to increase range or the time window of effectiveness (we could get around the treaty prohibition on nuclear arms in space by building the platform and only delivering the nukes just before use). And if we use up a significant fraction of our nukes in the effort, and don’t build more, then we even get arms reduction as a bonus.

    But as for developing a research program with the intent on relying on nukes as the primary option for all deflection scenarios, I think if we had the time and capability to do that, then we have the time and capability to do something else that is safer, more controlled, and more effective.

  83. T_U_T

    @amphiox,
    so we come to agreement at last.

  84. T_U_T

    Um, perhaps because the experts in the field have said over and over again, “blasting it with a nuke is not the correct course of action.” Now, they are entitled to their opinion, as are you. However, the scientists have real data to backup their claim, where you do not. Which one are you most likely to agree with?

    So again the information free appeal to authority stripped to the bare core of fallacy. Experts have shown you wrong so shut up. Man, I WANT to be shown wrong. Really. Show me wrong, but, show WHERE I made the mistake, and show me how to do it right next time right so I can wise up.
    No ? None of the real data the scientists ( and you too, because how else you could know about it ) have ? Just “they are experts you are not, so they are right and you wrong” ? Man, I beg you ! tell me PLEASE where I made the mistake.
    I summarize my wrong, stupid, ignorant, reasoning and you just put your finger on the first mistake.

    1. asteroids have large craters on them so they obviously can withstand at least the blast required to produce a crater of that size.

    2. Nuclear power has the highest energy density of all other means we have.

    3. the impulse provided by energy E converted to kinetic energy of working medium of mass Mw near the surface of the asteroid is sqrtf(2EMw) – VeMw where Ve is the escape velocity of the asteroid.
    If we seek to find maximum of impulse as a function of mass we get Mw = E/2Ve^2 and velocity of the working mass just 2Ve. so preferable way to kick the asteroid is to knock large mass off its surface at low velocity.

    4. so multiple subsurface bursts of nukes small enough to not to produce bigger crater than other craters on the surface will be the most effective way to push an asteroid.

    Then,
    deltaV = Enuke * number * effeciency / ( Rasteroid^4*sqrt(512/27*G*/PI^3*ro^3) ) =
    for stone 3000 kg/m^3 10km diameter and 200 * 200 kiloton nukes at 10 % efficiency deltaV = 1 m/2

    time_needed_in_days = R_earth / deltaV / seconds_in_a_day = 80 days

    Virtually no risk involved because the asteroid most likely withstood much powerful impacts, high precision because individual imprecisions of 200 nukes would average out.

    So, where I made the mistake ? Which line of reasoning is wrong ?

  85. Greg in Austin

    @T_U_T,

    Wow. Overreact much? ;)

    I never called you names, and again, I never said you were wrong. I simply asked for data. It didn’t have to be your own data. Surely some physics teachers (or even students) out there somewhere have already run the numbers. It shouldn’t be hard to find online.

    Furthermore, it is not Appeal to Authority. I didn’t say I agreed with them because they were physicists. I said I would agree with the data.

    Regarding your latest calculations, you are now stating that we could move a 10km asteroid with 200 nukes. This is a completely different problem than the one you originally stated. Originally, you said we could completely pulverize a 10km comet with a 100 megaton nuke. I still haven’t seen that data.

    8)

  86. T_U_T

    you have to be kidding me. As if nuclear explosion shockwave propagation inside solid material would be a matter of high school physics. You say, you agree with their data. Yet you don’t provide any link. Guess what ? I don’t believe you actually have any data at all. I could spend hours googling and putting together a simple model of 100 megaton blast inside 10km sphere of ice, and I would actually do it if there would be a slight chance to prove myself. But against someone who says about nuclear explosion cratering “Surely some physics teachers (or even students) out there somewhere”…. Well we humans are just not smart enough to be a match for your species.

  87. Greg in Austin

    @T_U_T,

    Um… don’t they teach physics in college where you come from? Maybe you can ask your nearest grad student.

    What claims have I made that require data?

    8)

  88. Greg in Austin

    Ok, here are some links:

    universetoday.com/2008/07/27/bad-idea-blowing-up-asteroids-with-nuclear-missiles/
    space.com/scienceastronomy/mystery_monday_040412.html
    blog.professorastronomy.com/2008/10/nuking-asteroids.html
    en.wikipedia.org/wiki/Asteroid_deflection_strategies

    (this is a PDF file)
    democrats.science.house.gov/media/File/Commdocs/hearings/2007/space/08nov/Yeomans_testimony.pdf
    In this document you can read:

    “TESTIMONY BEFORE THE HOUSE COMMITTEE ON SCIENCE AND TECHNOLOGY
    SUBCOMMITTEE ON SPACE AND AERONAUTICS
    NEAR-EARTH OBJECTS (NEOs) – STATUS OF THE SURVEY PROGRAM AND REVIEW OF NASA’S REPORT TO CONGRESS
    Donald K. Yeomans
    Manager, NEO Program Office
    Jet Propulsion Laboratory

    (pg. 5)
    What Should be Done in the Event of an identified NEO Threat? A number of existing technologies can deflect an Earth threatening asteroid – if there is time. The primary goal of the PHA survey programs is to discover them early and provide the necessary time. An asteroid that is predicted to hit Earth might require a change in its velocity of only 3 millimeters per second if this impulse were applied twenty years in advance of the impact. The key to a successful deflection is having sufficient time to carry it out, whether it is the slow, gentle drag of a gravity tractor or a more impulsive shove from an impacting spacecraft or explosive device. In either case, a verification process would be required to ensure the deflection maneuver was successful and to ensure the object’s subsequent motion would not put it on yet another Earth impacting trajectory. While suitable deflection technologies exist, none of them can be effective if we are taken by surprise. It is the aggressive survey efforts and robust planetary radars that must ensure that the vast majority of potentially hazardous objects are discovered and tracked well in advance of any Earth threatening encounters. The first three steps in any asteroid mitigation process are: Find them early, find them early, and find them early!”

    8)

  89. T_U_T

    So your counterargument to me saying that 100 megaton is three orders of magnitude more than the gravitational binding energy of the comet. is what ? A few press releases ? That’fs it ? None of them says a word that contradicts my words

  90. Greg in Austin

    @T_U_T,

    No, the links I provided back up my argument that using nukes to blow up an asteroid is a bad idea. The last link is to a pdf file from the Manager of JPL’s NEO Program, and nowhere does it suggest using nukes to deflect a threat.

    Now, if you have REAL DATA that shows otherwise, then that would be great, and I would agree with the data if was presented and correct. But so far, you have not shown us your calculations that prove a 100 megaton bomb could completely pulverize a 10km comet (that means all of its solid matter is converted to dust). Additionally, you haven’t proven that using a nuke will also move the dust out of the path of the earth.

    Until then, it is strictly your opinion.

    8)

  91. T_U_T

    putting the numbers into the equation and computing that 100 megaton is 1000 x the energy needed to send all of the comet mass off at escape velocity is not real data for you ? What is then ? Is the fact that forces involved are several orders of magnitude above maximum strength of ice, ( not even mentioning that actual comet is NOT solid block of crystalline ice ). Maybe it would be not dust, it would be more of snowflakes mixed with small pieces. But if something is kicked with a force orders of magnitude higher than forces that hold it together, it will be blasted to smithereens. Or do your require REAL DATA even for that ? What about an experiment. Take a grenade, put it up your butt, and let it explode ;)

  92. Greg in Austin

    @T_U_T,

    Nice. You can’t support your argument any other way, so you resort to infantile attacks. How uncivilized.

    8)

  93. T_U_T

    Other way than doing maths ? No. And I don’t see any reason why it should be necessary. On the other hand, you.

    1. make an argument backed by nothing than authority
    2. claim it is not an argument from authority because you don’t agree with them because they are authorities, but because of their data
    3. when I ask you, instead of giving the data, you start to claim your claims don’t need any real data to back them up.
    4. then you give few links and the “data” that caused you to agree with them turns out to be “scientist XY said nukes are bad solution” And more, he said it to a committee that could decide to stop paying any NEO search program if they had a slight suspicion that nukes they already have could be sufficient.

    In short, you have proven yourself to be completely hypocritical jerk.

    I was initially afraid you have something like a computer simulation that somehow shows that large fragments of the comet could survive in spite of the fact there was enough energy to destroy it thousand times, and only delay the utter destruction of my claims because you like playing cat and mouse with me.

    Thank you to proving my fear wrong, goodbye !

  94. T_U_T

    errata : Thank you for proving my fear wrong,

  95. Greg in Austin

    @T_U_T,

    I still haven’t seen your “maths” on hitting a comet in orbit with a 100 megaton nuclear device. If I missed it, please let me know.

    I already asked you once, but you didn’t answer: What did I claim that requires data?

    8)

  96. T_U_T

    last try.
    energy / kg of TNT is 4.184e6 J. 100 megaton nuke would produce 4.184e17 J of energy.
    gravitational binding energy is G*PI^2*16/15*density^2*radius^5 s0 for 10 km comet we have density = 500 kg/m3 R = 5000 m so we get 5.485855e14 J which is 762.6 times less than the energy of the nuke, so there is simply no way the comet could survive it

    Now, you have the maths, let’s see whether you will accept it. I predict not.

  97. T_U_T

    I didn’t say I agreed with them because they were physicists. I said I would agree with the data

    That is where you’ve made claim that requires data to support it. You say you agree with them because od the data. So, show the data right now or be called LIAR.

  98. Greg in Austin

    @T_U_T,

    Does the kinetic energy (angular momentum, etc) of the asteroid or comet factor into your equations?

    8)

  99. Greg in Austin

    Oh no! T_U_T may call me a LIAR! My whole world is going to end. ;)

    This is interesting to watch: Its a simulation of an impact onto an asteroid.
    nasaimages.org/luna/servlet/detail/NSVS~3~3~13110~113110:Asteroid-Castalia-Impact-Simulation
    Same info, different site:
    svs.gsfc.nasa.gov/vis/a000000/a000500/a000558/

    I haven’t paid to download this article, but it looks very interesting:

    Investigation of the nuclear explosion effect on asteroids
    V. Fortov, V. Kondaurov and I. Lomov

    High Energy Density Research Center of Russian Academy of Science 13/19, Izhorskaya, Moscow, 127412, Russia

    Available online 11 March 1999.

    Abstract

    Impact of an asteroid on the Earth could be catastrophic. Deflection and fragmentation of such asteroids by surface and underground nuclear explosives has been proposed. The aim of this investigation is the optimization of explosive effects by varying of the explosive depth and charge. The study is based on nonlinear thermomechanics of an elastoviscoplastic damaged medium. For numerical simulation Godunov’s type scheme on unstructured grid is used. The deflecting impulse depends on the power and depth of the charge, and the physical and strength properties of asteroid material. The process of dynamical vaporization and disintegration of asteroid material around the burst point as well as the generation of intensive jet is also investigated.
    Article Outline

    sciencedirect.com/science?_ob=ArticleURL&_udi=B6V3K-3W0FXW3-2J&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=c8c5890c0cbc3c5c235ec0c116376bd8

    8)

  100. IVAN3MAN

    I can’t believe this discussion is still going on!

    T_U_T, do you realize how much a “100 megaton nuke” weighs?

    The Russian “Tsar Bomba” had a mass of 27 tonnes! Whereas using the kinetic impact defection method against an asteroid/comet could be achieved with a projectile with a mass of just one tonne.

    Furthermore, a gravitational tractor with an equivalent mass of 27 tonnes, once deployed in space, can be used again and again, but a 100 megaton thermonuclear device can only be used once. Therefore, a gravitational tractor would be the most cost effective option than a “nuke”.
    :cool:

    Greg, I trust that you don’t mind me using the “cool” emoticon.

  101. Greg in Austin

    @IVAN3MAN,

    Not at all. I didn’t invent it. Its cool!

    8)

  102. T_U_T

    WOW. I don’t believe it. You actually wrote something of substance.
    The problem is, that, not even paying would help you with that article. I tried to download it a time ago, got only errors. The article ( and several others written all by russians ) apparently exists only in Russian original. Anyway. none of the abstracts, suggests I am wrong.
    And the simulation you linked to, is a few kiloton impact, on the surface, not 100 megaton deep inside, and also, it is also 800m asteroid, not a 10km comet which means the objects are not similar at all.

  103. Todd W.

    Just a quick logistical question: If we take one hundred 1 megaton nukes, just how long would it take to compute the proper trajectories for all of those to hit the object? On top of that, what are the calculations that would be necessary to time the launches correctly so that they all hit at exactly the same time?

    Even if we reduce it to ten 10 megaton warheads, the logistics are still pretty nasty.

    And if we go with one 100 megaton warhead, what kind of delivery vehicle is necessary to not only get the warhead away from Earth, but keep it heading in the right direction? Does such a delivery vehicle exist already? If not, how long would it take to design, engineer and build?

  104. T_U_T

    IVAN, the 100 megaton nuke scenario was only an example of almost the worst case.
    If the asteroid is small, and collision decades ahead, surely gravitational tractor is a possibility ( no, it can not be used again and again, because it expends fuel, and expends more of it per 1m/s deltaV than nuke )

    The same problem is with a kinetic impactor. 30 ton used against a comet speeding at 100 km/s will produce 50 kiloton explosion which is 20 times less. Against much slower asteroids it would be maybe just 5 kiloton. Which is really pathetic.

  105. T_U_T

    Q : If we take one hundred 1 megaton nukes, just how long would it take to compute the proper trajectories for all of those to hit the object?
    A : several miliseconds.

  106. Todd W.

    @T_U_T

    A : several miliseconds.

    Can you provide a citation for that figure? Thank you.

  107. T_U_T

    Todd, please, trajectory computations required to send something straight to an asteroid are really simplistic. No one would really bother to estimate how long would 100 of them take. Most of the time would be spent on reading input and writing results.

  108. Todd W.

    @T_U_T

    So you have no citation for your claim? Upon what do you base your conclusion that the trajectory computations are simplistic? Do you have experience calculating such trajectories, taking into consideration the Earth’s rotation, position of the moon, positions of satellites and other orbiting objects, atmospheric conditions, etc.?

  109. T_U_T

    Q : So you have no citation for your claim?
    A : No, but you can download demo java applets doing N-body simulation of trajectories http://www.cs.cmu.edu/~scandal/alg/nbody.html
    It is really no big deal, any such mission woud start at LEO so all you would need is position and velocity of the of the asteroid, orbital parameters of the probe, and work out trajectory of the warhead by numerical simulation The gravity of any other body than earth, sun, moon, and the asteroid would be negligible so you could do them really fast.

  110. IVAN3MAN

    T_U_T:

    If the asteroid is small, and collision decades ahead, surely gravitational tractor is a possibility (no, it can not be used again and again, because it expends fuel, and expends more of it per 1m/s deltaV than nuke).

    So, do you dispose of your car and buy a new one every time it runs out of gas?

  111. IVAN3MAN

    Damn it! I did not close that “blockquote” tag properly.

  112. T_U_T

    Ivan:

    So, do you dispose of your car and buy a new one every time it runs out of gas?

    my car i neither nuclear powered, neither most of its mass is fuel, neither the fuel is of comparable price to the car, and also, I don’t usually travel outside of earth gravitational well.

    Todd : my link is stuck in the moderation you will have to wait

  113. IVAN3MAN

    T_U_T:

    The same problem is with a kinetic impactor. 30 ton used against a comet speeding at 100 km/s will produce 50 kiloton explosion which is 20 times less. Against much slower asteroids it would be maybe just 5 kiloton. Which is really pathetic.

    Actually, that works out at 35,850.86 kilotons; however, the point of the kinetic impactor is not to pulverize the asteroid/comet, but to ‘nudge’ it out of the way — the feasibility of which is what ESA’s Don Quijote mission aims to determine.

  114. Greg in Austin

    T_U_T said,

    “A : No, but you can download demo java applets doing N-body simulation of trajectories (cs.cmu.edu/~scandal/alg/nbody.html)
    It is really no big deal, any such mission woud start at LEO so all you would need is position and velocity of the of the asteroid, orbital parameters of the probe, and work out trajectory of the warhead by numerical simulation The gravity of any other body than earth, sun, moon, and the asteroid would be negligible so you could do them really fast.”

    Which of those java applets did you use to determine the trajectories of 100 rockets would only take a few milliseconds to calculate?

    Wait, so we would need 100 nuclear warheads in low-earth-orbit waiting to be sent to intercept an asteroid? How many times have we sent a probe to intercept an asteroid or comet? Were those missions simplistic, like you said? And if we were going to hit one asteroid with 100 nukes, would we plan to hit the asteroid with all 100 at once, 10 at a time, 1 at a time? What happens when one nuke hits, fractures the target in two, and the next 10 fly right on thru the gap? Is calculating those course corrections 1,000 times a second trivial as well?

    This sounds way more complicated than you claim.

    8)

  115. Todd W.

    @T_U_T

    A : No, but you can download demo java applets doing N-body simulation of trajectories http://www.cs.cmu.edu/~scandal/alg/nbody.html
    It is really no big deal, any such mission woud start at LEO so all you would need is position and velocity of the of the asteroid, orbital parameters of the probe, and work out trajectory of the warhead by numerical simulation The gravity of any other body than earth, sun, moon, and the asteroid would be negligible so you could do them really fast.

    Greg already addressed this, but I have some thoughts as well.

    So, we need to start with X probes in orbit, all armed with nuclear warheads. Great, so where are these probes? Who is going to build them? Who is going to launch them? What will happen if something goes wrong with the launch? Who will control them once they are in orbit? And, more pertinent to an impending collision, just how long does it take to figure out the exact location of each of these probes for purposes of calculating the trajectory of the warheads? As I understand it, getting the precise location of a satellite is a mite on the fuzzy side.

    My other questions still stand, which Greg reiterated. Are we using 1 100-megaton nuke? 10 10-megaton nukes? 100 1-megaton nukes? If there is more than one, then I assume that they will all hit at the exact same time to avoid situations like Greg describes, in which subsequent missiles miss or do only negligible damage, at best, and at worst send debris hurtling more directly toward Earth when it may otherwise have been on course to miss the planet. So, how long does it take to calculate the timing required to hit the asteroid at the exact same moment? Certainly more than milliseconds, and I’d wager it’s a somewhat non-simple bit of math.

    So, really, your “milliseconds” claim was pulled out of thin air and has nothing to back it up. Nor does your claim that it is simple to determine.

    Perhaps I’m being a bit unfair. The calculation itself may take milliseconds on a properly robust computer, but the initial legwork of determining position of everything involved, all object speeds and directions, etc., followed by inputting everything into the calculating module, would take a wee bit more than a few milliseconds.

    And from your earlier post:

    No one would really bother to estimate how long would 100 of them take.

    Actually, I think they probably would, as it would affect the timing of every part of the process. You need to have some idea of how long it would take to figure out something requiring that level of precision so that the overall timing doesn’t get screwed.

    Some follow-up questions: what happens when the orbital probes collide with something else? What happens if someone that controls one of those probes gets a bit twitchy and decides to use them for a different purpose? What happens when the timing is off by a few seconds? Will the asteroid still pose a danger to Earth?

  116. Todd W.

    @T_U_T

    My response to your java applet post is awaiting moderation.

  117. IVAN3MAN

    T_U_T, your car may not be nuclear powered, but the proposed gravitational tractor may be — such as a Nuclear Electric Rocket. Even a conventional rocket powered gravitational tractor could be refuelled by robot ‘gas stations’.

    Writing in Nature*, physicists Edward T. Lu and Stanley G. Love of NASA’s Johnson Space Center show that a gravitational tractor is a reasonable proposition: it is robust to the asteroid’s structure and rotation rate, and a technologically feasible plan that could impart a delta-v of a few millimeters per second to an asteroid with a diameter of 200 metres over the course of several years, sufficient to prevent an Earth impact.


    *Nature 438, 177-178 (10 November 2005); doi:10.1038/438177a.

  118. ERRATUM: At my previous post above, due to a typo error and incorrect placing of decimal point, it should read: “Actually, that works out at 35.85086 kilotons…”

    Phil, when the bloody hell are we gonna get a preview/edit facility here?!

  119. T_U_T

    Actually, that works out at 35,850.86 kilotons;

    comparison. 475 kiloton warhead weights only 270 kg

    proposed gravitational tractor may be — such as a Nuclear Electric Rocket. Even a conventional rocket powered gravitational tractor could be refuelled by robot ‘gas stations’.

    comparison ISP :
    VASIMR 36 000
    nuclear pulse propulsion > 100 000

    And, also, we have several thousands nuclear warheads but no working nuclear electric rocket yet.

  120. Greg in Austin

    T_U_T said,

    “And, also, we have several thousands nuclear warheads but no working nuclear electric rocket yet.”

    How many of those warheads are attached to rockets or probes that could travel 150 million kilometers or more?

    8)

  121. IVAN3MAN

    T_U_T:

    And, also, we have several thousands nuclear warheads but no working nuclear electric rocket yet.

    According to this document, the Sun could be a source of unlimitled power for a Gravity Tractor:

    Hovering Control of a Solar Sail Gravity Tractor
    Spacecraft for Asteroid Deflection
    [PDF]

    A solar sail gravity tractor (SSGT) spacecraft is proposed as a viable option for deflecting a certain class of near-Earth asteroids (NEAs) such as highly porous rubble piles rather than solid monolithic bodies. Solar sails are large, lightweight reflectors in space that are pushed by sunlight. The SSGT spacecraft concept is based on the so-called Gravity Tractor (GT) for towing asteroids by using gravity as a towline, which was proposed by Lu and Love in the 10 November 2005 issue of Nature. It exploits the “propellantless” nature of solar sails; consequently, its probable advantage over a GT spacecraft propelled by ion engines is its longer mission life times (> 10 years) with a larger “propellantless” ΔV capability. Furthermore, it has no concern of rocket plume impingement on the asteroid surface. This paper demonstrates the practical hovering control feasibility of an SSGT spacecraft for towing NEAs. For example, a 5-year towing of asteroid Apophis using a 2500-kg SSGT spacecraft (equipped with a modest 90-m, 50-kg solar sail of a 0.03-N solar thrust with a 35-deg sun angle) and an additional 3-year coasting time will result in an orbital deflection of 30 km in 2029. A 30-km deflection is more than sufficient to move Apophis out of its 600-m keyhole.


    Click on the link to download PDF file.
    :cool:

  122. T_U_T

    Ivan. Any method of asteroid deflection is good if it can work.
    If you compare them in terms of deltaV, nothing ( except perhaps antimatter catalyzed nuclear drive, or some dusty plasma reactors ) can be a match for simply kicking the asteroid with a series of small nuclear explosions.
    If you have enough time, and need to move a small asteroid only a little, Then you can use other criteria, and, some other method may be the best one.I am all for it, but, I really don’t like the idea that the other criteria would be ‘just no nukes, PLEEEASE !’

  123. IVAN3MAN

    @ T_U_T,

    Agreed. I never stated “no nukes” ever, just as a last resort.

  124. Lee

    I asked the Question on Jiba-Jaba…”If an Asteroid was on a collision course with Earth. What would I have to do to be one of the 1 million people hand picked by the Government to be saved?”

    http://www.jiba-jaba.com/Asteroid-On-A-Collision-Course-With-Earth.aspx

    It makes me think about do I really do enough in my life to actually make a difference…

  125. Faheeeem

    Can you reply on my email, i have some astronomy help questions to ask you..

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