Stopping asteroid impacts

Discussion in 'Physics & Math' started by Bowser, Mar 20, 2019.

  1. Bowser Namaste Valued Senior Member

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    if an asteroid were to hit the earth tomorrow, could you stop it?
     
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  3. sculptor Valued Senior Member

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  5. sideshowbob Sorry, wrong number. Valued Senior Member

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    Well, the earth would stop it.
     
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  7. kx000 Valued Senior Member

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    I could, but can I? That's whole 'nother can of worms.
     
  8. Write4U Valued Senior Member

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    That's about the size of it. Back to the age when worms ruled the earth........

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  9. Baldeee Valued Senior Member

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    I think from a grammatical point of view, your use of the past indicative suggests that we answer from a point of view of the asteroid having already hit the earth, by which time it is impossible to stop it from having happened.

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    If you meant to ask whether we could stop an asteroid on a collision course (i.e. yet to happen) and due to strike tomorrow then the answer is pretty much no, I think, given the short timeframe involved.
    If an asteroid is still some considerable distance away I guess you could nudge its trajectory so it misses, but the earlier you do that the better.
    I'm sure that if an asteroid is close enough to hit us tomorrow then I would think this is too close, and it would take too much energy to nudge it in that manner.
    Your best bet at that distance would be to destroy it as much as possible, break it into tiny chunks that would disintegrate in the atmosphere.
    Although this is still fraught with danger, and even a smallish chunk could cause chaos on impact.
    That said, it would depend on the size of the asteroid, although the term itself suggests something of significant proportion (cf. meteor).
     
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  10. Yazata Valued Senior Member

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    Me personally? Of course not.

    Could anyone stop it? Not with one day's notice. With existing technology, probably not even with much more warning. (Baldeee has addressed that one.)

    I see this as a physics question. Why is it in philosophy?

    Did you mean to ask 'Would we stop it if we could?'

    That's more of a psychological question than a philosophical one, a measure of alienation, I guess.

    My answer would be , 'Yes, of course I would stop it if I could'.
     
  11. DaveC426913 Valued Senior Member

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    Took the words outta my mouth.
     
  12. DaveC426913 Valued Senior Member

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    One lady stopped an asteroid with her hip.
    I think it's the only recorded case in history.
     
  13. TheFrogger Banned Valued Senior Member

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    Yes. I would send a team of oil-drillers to plant a nuclear device within said asteroid, and detonate it.
     
  14. Yazata Valued Senior Member

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    Bruce Willis might not be available.

    NASA announced today that SpaceX is the winning bidder to launch NASA's 'Double Asteroid Redirection Test' (DART) mission. This one proposes to crash a spacecraft at very high relative velocity into a very small (150 meter) asteroid to see how much they can deflect its orbit by kinetic energy alone. It's one of several schemes that NASA is working on to protect Earth from asteroid collision. (Nuclear explosions is doubtless another. Not to break an asteroid in half like in the movie, but to use the force of an explosion near its surface to deflect its trajectory.)

    While this DART object is obviously a very small asteroid, they are the ones statistically most likely to hit our planet. And you don't have to change the velocity of the asteroid very much if you can hit it far enough away. Planets are tiny things in the vastness of space. Even a tiny asteroid velocity change might be the difference between hitting and missing the Earth.

    https://www.nasa.gov/press-release/...s-contract-for-asteroid-redirect-test-mission

    https://www.nasa.gov/planetarydefense/dart

    Hey, you can all laugh, but when the world needs protection from a marauding asteroid, everyone on Earth's gonna be demanding "Where's NASA?"
     
  15. James R Just this guy, you know? Staff Member

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    I went to a talk a few years ago by a guy who is an expert on these things. It's really no laughing matter.

    His suggestion was to use a "risk rating", defined as the estimated probability of an event occurring, multiplied by the estimated loss of human lives if such an event were to occur.

    Every American has an estimated 1 in 114 lifetime chance of dying in a car crash. In comparison, Americans have about a 1 in 9800 chance of dying in a plane crash. That means that your annual chance of dying in a car crash, if we take the average lifespan to be 70 years, is 1/(114 x 70)=0.000125. In America (in 2015), 35000 people died in fatal car crashes. So, the annual "risk rating" for dying in car crash could be calculated as 0.000125*35000=4.39. In the same year, there were 27 US airline accidents, none of which had any fatalities. But let's imagine there is 1 major fatal plane crash per year, for the sake of argument, and it kills 300 people, on average. Then, the annual risk rating for dying in such a plane crash would come in at 1/(9800 x 70) x 300=0.000437. Clearly, on this measure, plane travel is a lot less risky than car travel (about 10000 times less risky!).

    Now consider an extinction-level asteroid impact, like the one that killed the dinosaurs. Suppose that such an impact happens once every 100 million years, but it kills 100 million Americans if it occurs. Then the annual risk rating comes out as 1, on the same scale used for the car and plane crashes. That is, the risk rating is a little less than for car crashes, but far greater than for plane crashes.

    This is not a risk we can afford to be complacent about. Think about the efforts put into car and (especially) air safety, which is why the risk rating for airline crashes has gone down so dramatically over the time that airliners have been in operation. In comparison, relatively little effort has so far been put into reducing the risk of an extinction-level meteor impact.
     
    Last edited: Apr 12, 2019
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  16. sculptor Valued Senior Member

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  17. Yazata Valued Senior Member

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    The more I think about it, the more questions I have about using nuclear explosions to deflect asteroids.

    We all think of nuclear explosions in terms of blast effects. But blast effects seem to me to be a function of what the explosion is doing to the surrounding atmosphere and what that energized atmosphere in turn is doing to structures in the vicinity. But in space there isn't any atmosphere to transmit mechanical force. You would merely have the vaporized fragments of the bomb itself, which might not have very much mass or change the asteroid's velocity by very much. So a nuclear explosion detonating in space near an asteroid might just expose the asteroid to lots of radiation at various frequencies without changing its velocity to any useful degree.

    In terms of mechanical force, a high-velocity kinetic impactor like DART might work just as well. Essentially shooting the asteroid with a bullet. With an operational as opposed to test version, you would presumably want to multiply the mass of the impactor.

    I'm not sure how much force a nuclear bomb resting on the surface of an asteroid would impart either. I guess that the goal there would be to make the asteroid eject mass in a desired direction so as to serve as a de-facto reaction engine. That suggests that drilling (paging Bruce Willis!) and burying the nuclear bomb a short distance under the surface might be the best option. Deep enough that a significant mass is propelled into space. But not so deep that the blast is muffled by the surrounding rock, like in an underground nuclear test.

    In its infinite wisdom, the United States has empirical experience with using nuclear explosions for purposes of excavation and earth moving here on Earth. Shot Storax Sedan in 1962 succeeded in throwing 11 million tons of dirt into the air using a 100 kiloton nuclear device. (Ya gotta love the old 1950's-1960's wild and crazy engineering schemes. It's what put men on the Moon.) I suppose that there would have to be lots of calculations in order to maximize the size and velocity of the ejected mass and hence to maximize the reaction force on the rest of the asteroid.

    https://en.wikipedia.org/wiki/Sedan_(nuclear_test)

    This is the Sedan crater at the Nevada Test site.

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    Last edited: Apr 12, 2019
  18. Sarkus Hippomonstrosesquippedalo phobe Valued Senior Member

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    Surely NASA know the maths, and the law of conservation of momentum, which would put a maximum limit to the ability they're testing? And surely earth-based testing can determine, roughly, how much energy and momentum would be lost in the impact? So why on earth would they spend USD hundreds of millions on something that is not exactly going to reveal anything new?
     
  19. Yazata Valued Senior Member

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    Dunno. (They don't confide in me.) I might go see what's being posted about it on the NSF discussion board. Lots of NASA and SpaceX people post there and they have threads on every space mission.

    (Edit: they do have a thread on it, started today, but nothing new there.)

    I can speculate though. They probably have lots of back-of-the-envelope calculations as to what they might expect. But models and real-life can be two different things.

    And I'm guessing that a lot of their interest is in perfecting the technology, guidance and propulsion. If you want to fire a gun accurately, you need to practice at the range. Hitting a tiny 150 meter asteroid some 11 million kilometers away at those high relative velocities probably needs perfecting too. A grazing strike wouldn't work. They want to adjust the direction it's moving in a desired way.

    It will be a small velocity change in any case. They say a fraction of 1%.

    They're the f-ing government! Spending US dollars is their job!
     
    Last edited: Apr 12, 2019
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  20. RainbowSingularity Valued Senior Member

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    i imagine a hydrogen bomb traveling at 50,000 kilometers per hour would probably stop a 1 kilometer wide asteroid.
    though if the calculations were a little off and it detonated after the asteroid went past it might complicate things a little.

    unless that is spending it on the poor for housing & health care
    in which case they seem to be trying to force a camel through the eye of a needle
     
  21. Sarkus Hippomonstrosesquippedalo phobe Valued Senior Member

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    But isn't the point about this scenario that should it ever arise we're not exactly going to rely on one person firing a gun at a range... we're going to lay waste to the targets, and probably everything in the vicinity as well.

    Nah, it's just an ego mission. Would be ironic if the test actually resulted in the target changing velocity such that it ended up on a collision course with earth! :/
    But there are walls to build! There are billionnaires to give tax cuts to!

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  22. Janus58 Valued Senior Member

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    The problem with this solution is that the Earth is still absorbing the KE of the asteroid. You may have avoided ground impact, but you are exchanging that for pumping a a lot of heat into the atmosphere. This was the problem I had with the ending of the movie "Deep Impact". At the very last minute, the comet is exploded and its fragments " harmlessly" burn up in the atmosphere. "Harmless" if you don't consider the effect of that much energy being added to the atmosphere and its effects on weather patterns and the climate.
     
  23. DaveC426913 Valued Senior Member

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    True, though it may fall shy of an Extinction Level Event. That'd still be a win.

    Like the difference between being hit by a bullet and hit by a sheet of bristol board (albeit one moving at 3K ft/s).
     

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