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Space Science

Paintball Pellets As a Tool To Deflect Asteroids 153

SternisheFan sends this quote from an article at MIT's Technology Review: "In the event that a giant asteroid is headed toward Earth, you’d better hope that it’s blindingly white. A pale asteroid would reflect sunlight — and over time, this bouncing of photons off its surface could create enough of a force to push the asteroid off its course. How might one encourage such a deflection? The answer, according to an MIT graduate student: with a volley or two of space-launched paintballs. Sung Wook Paek, a graduate student in MIT’s Department of Aeronautics and Astronautics, says if timed just right, pellets full of paint powder, launched in two rounds from a spacecraft at relatively close distance, would cover the front and back of an asteroid, more than doubling its reflectivity, or albedo. The initial force from the pellets would bump an asteroid off course; over time, the sun’s photons would deflect the asteroid even more."
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Paintball Pellets As a Tool To Deflect Asteroids

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  • Too tenuous (Score:5, Funny)

    by hessian ( 467078 ) on Saturday October 27, 2012 @05:59PM (#41792081) Homepage Journal

    That's a long shot plan right there.

    I think sending Bruce Willis with a thermonuclear device and a boatload of family drama might work even better.

    • It certainly would, for turning the equivalent of an FMJ round into a shotgun shell. My vote is for a big-ass chemical thruster, those still have the greatest specific impulse we can muster on short notice.

      • Re:Too tenuous (Score:4, Informative)

        by Dr_Barnowl ( 709838 ) on Saturday October 27, 2012 @06:32PM (#41792287)

        Rockets have *terrible* specific impulse, around 450s for a complex bi-propellant liquid rocket, and 250s for the stable, reliable solid rockets.

        Ion engines have specific impulse up in the thousands to tens of thousands of seconds.

        Rockets have a lot more thrust per unit of engine mass, but getting enough propellent up there to give an asteroid sufficient delta-V would be all but impossible - for every big-ass rocket, you'd need a 10x bigger assed rocket to get it there in the first place.

        • Re:Too tenuous (Score:5, Interesting)

          by Dekker3D ( 989692 ) on Saturday October 27, 2012 @06:56PM (#41792455)

          You could avoid half the delta-V by not slowing down-... just have the rocket speed up to max speed and slam into the asteroid. Calculate the engine size and fuel amount to be okay for the range you need it at, then make a few rockets to stand ready for various ranges. Crumple zones would let all the impact go into pushing, rather than shattering the thing. Even use some kind of internal room full of tiny airbags if you must. One-way valves (with a tiny air-hole for letting them deflate on impact and not burst prematurely) on all of them, inflate them the usual way or use a small amount of rocket exhaust that you cool down somehow. Simple, really.

          • just have the rocket speed up to max speed and slam into the asteroid.

            But that "max speed" would not be very high. Rockets only make sense if you need a LOT of thrust in a very short period of time (say, to get off a planet's surface). But if we are going to deflect an asteroid we will need to do it when it is still months or years away from hitting the Earth. Which means you will have months or years (rather than minutes) to get up to speed. So an ion engine would make more sense. They provide little thrust, but they can keep it up for a very long time. For a given amo

            • But if we are going to deflect an asteroid we will need to do it when it is still months or years away from hitting the Earth.

              If you leave it until the PHA (Potentially Hazardous Asteroid) is a few hours travel from Earth, then you're going to need large forces and you've got no time for a plan 'B'. If you get it wrong, millions or billions will die.

              Most PHAs are going to be in an orbit with approximately the same period as the Earth (they can have different phase, inclination, argument of perihelion and

      • by toastar ( 573882 )
        Chemical Thrusters don't have high specific impulses, They have high thrust. If you want a specific impulse engine you'd use an ion thruster or a even a nerva.
        The issue with any type of engine is first you have to arrest the asteroid's spin.
        • You could also some sort of a mass driver, only firing it when it's pointing in an appropriate direction.

      • My vote is to shoot moon rock at it from said moon.

        As far as I can see, the only thing that is slightly hard to do, is getting enough energy on the moon (which would have to be produced or transported there).

        Of course, we would also have to build a catapult that is able to launch moon rock precisely enough.
        And a mining facility.
        Then again, we'd pretty much want to do comparable things anyway (for multiple reasons).

        • Workable for an idea. And with a little attention to detail, you could use it multiple times.

          The precision of aim would have to be high. For a 100m asteroid in the nearest 10'th of it's orbit ... I make it between 5 microradians and 100 nanoradians.

          What is the likelihood of particles that miss the target coming back on their orbit to impact Earth (or the gun) a year later?


          • by sjames ( 1099 )

            I would suggest many smaller projectiles. It matters less if one misses that way and if it comes back around, it can burn up with little damage.

      • impulse we can muster on short notice.

        That last term is the important one. Is your "short term" a day, a week, a month, a year, a decade, or a century. Only the last couple of those are noticeably different from "instantaneous" in my working environment.

    • by Anonymous Coward on Saturday October 27, 2012 @06:26PM (#41792261)

      Spaceballs ?

    • It would be better to give this to the Mythbusters crew. They seem to be particularly adept at blowing things up. The myth would be, "Humanity can be saved from an impending asteroid collision". It would suck if it gets busted.

      Or now that we can make Higgs' Bosons in CERN, can't we shoot Higgs' Bosons at the asteroid, or something? Or if we untangle Superstring Theory, can't we just shove the asteroid into another unseen dimension?

      Please be creative with your answers, Hollywood is monitoring this thre

      • If you're talking hollywood physycs... with enough warning, could we just build an epic-huge rocket on earth and alter the planet's orbit enough for the asteroid to miss.
        • That one's actually been done already: []

          The year is 1982, and the film opens with the launch of the JX-1 Hayabusa spaceship into outer space. The ship, originally sent to collect data on Saturn, has its course diverted to investigate the mysterious star Gorath, reported as being 6000 times the size of the Earth. It is feared that the star's path could come dangerously close to Earth. The JX-1 reaches locates Gorath and it's much smaller than earth but with 6000 times the gravity.

          The United Nations band together to discover a solution to the problem, and decide that their only solutions are to either destroy Gorath or move the planet out of the way. Back on Earth, the UN decides on the plan to move the Earth out of the way of Gorath, the South Pole Operation. The plan is to have atomic energy channeled through huge atomic furnaces 500 meters below the surface, then fed though enormous pipes called thrusters which will all fire in unison. But for this to work they will need an area 600 kilometers producing an atomic force equal to that of 6,600,000,000 megatons to move the Earth 400,000 kilometers way from Gorath.

          That sounds like a great plan doesn't it? But there's always a catch . . .

          The atomic engines are completed and fired up, moving the earth out of the way of Gorath. But the heat from the engines awakens and frees a giant monster walrus, called Maguma, that attacks the South Pole base.

          So, your idea was good enough for a movie. If you have any other ideas, please send them to Japan or Hollywood. The world needs to be saved with better science fiction than they have to offer.

    • Re:Too tenuous (Score:5, Insightful)

      by paiute ( 550198 ) on Saturday October 27, 2012 @06:57PM (#41792461)

      That's a long shot plan right there.

      I think sending Bruce Willis with a thermonuclear device and a boatload of family drama might work even better.

      Modded funny but is actually insightful. What would happen is that the chance of the giant asteroid actually hitting the earth will start out less than certain, so the large expense of sending a mission to deflect it far from earth using a gentle push would result in debate and delay. Then the odds of impact will increase, but the expense of the mission will still be high. We will piss and moan, and a loud minority of self-anointed space experts who begin to say that the rock is actually going to miss, that it is all a liberal/conservative/alien conspiracy, that there is really no asteroid, etc. will get a lot of press. Finally the thing will be visible from earth and the shit will hit the fan but by then it will be too late to use mild persuasion, and we will have to send up whoever passes for Bruce Willis with a crapload of nukes. We will blow it into chunks, maybe even into gravel whose kinetic energy strips away the atmosphere.

      • That's what would happen in America. Half the voters wouldn't want to send a nuke anyway, believing that God will protect mankind. While America is still debating, China will blow it up instead. They have a space program and nuclear weapons, and a semi-dictatorial government can get things done a lot faster in a crisis.
        • by TheLink ( 130905 )
          You really think those sociopaths controlling the USA won't take action for their own sakes? Their lifestyle would be severely degraded if a large enough asteroid hits the earth.

          Action has been taken without the voter consent plenty of times.
    • by slick7 ( 1703596 )

      That's a long shot plan right there.

      I think sending Bruce Willis with a thermonuclear device and a boatload of family drama might work even better.

      Paint ball, 357 magnum, rail gun, asteroid; see the ever increasing progression of feeble stupidity?

  • with enough advance warning would simply landing a rocket on the asteroid and having it provide a constant thrust be enough to have the asteroid miss ?

    at a great distance it would take very little course adjustment which could be provided by a very low thrust.

    the obvious complication being if it's tumbling. even then it seems that such a scheme would still work as the rocket could align itself under guidance or using the stars and provide force at the proper time.

    not sure why this is never mentioned as an

    • How much thrust would you be able to generate for long periods of time, and where does the energy come from ? Huge solar panels ?
    • It's been mentioned quite often... probably why it's no longer considered news

    • by tnk1 ( 899206 )

      Painting the asteroid, assuming there was a good way of doing it, is probably more reasonable than building an engine to do it. The rocket engine would be more complicated and need to be lifted off Earth and make it to the asteroid in operable condition, whereas all you need to do with the paint is disperse enough of it to thinly cover the asteroid.

      There is also the possibility that if you believed that the underlying material of the asteroid was lighter or would outgas, you could set off explosions to dis

    • by Arker ( 91948 ) on Saturday October 27, 2012 @06:53PM (#41792419) Homepage

      Actually 'landing' on it would be a huge problem. An asteroid is not typically one large smooth rock, after all. And it will definitely be 'tumbling' in relation to you as well. So it would be a very difficult docking maneuver on an uncertain surface. And remember these things arent large enough to generate enough gravity to notice either. So it's basically all in zero-g.

      Spraying a load of paint at it would be orders of magnitutude easier, and still wouldnt exactly be easy.

    • The problem is fuel. We don't have rockets that can fire for months. We have rockets that can fire for minutes. They provide a huge amount of thrust during that time, but you would need far, far more thrust than any existing rocket can provide to move an asteroid off-course.

      A vague possibility is an ion engine of some sort. These have much lower thrust, but can run much longer off the fuel they carry. The technology still isn't very proven, though - and trying to land an engine, intact, on an asteroid, it a

    • Not as easy as it is on the drawing board. First, that rocket would have to be aligned EXACTLY with the center of gravity or all you accomplish is giving it a nice spin. Now, we don't even know for sure just what the asteroid is made of, let alone know the exact point of its COG. Many asteroids are anything but spherical, making the matter even worse. Considering how there is very little gravity acting on it, is it solid in the first place? Or composed of many smaller rocks held together by their gravity?


    • Landing on a tumbling small body is not something you 'simply' do. Doing it to apply significant thrust is even harder due to center-of-gravity issues.

      A better way to have the same effect is to use a gravity tractor approach. By hovering away from the asteroid, you can use the gravitational attraction of the spacecraft on the asteroid in the same way. Since you'd need to use low thrust engines to get a significant amount of force over a reasonable time frame, the fact that the gravity tractor limits the

      • Dawn mission could have landed on Vesta, and would have but Ceres wanted a visit too. Dawn will likely land on Ceres. These are among the most massive asteroids, and most difficult to land on. Even a theoretical stony asteroid that has so much spin imparted by impacts that its surface gravity at the equator is negative has spin poles to land on. It is really not so hard to land on an asteroid, especially if you reserve a chemical rocket for the deorbit burn. It really doesn't need much.
  • ...change the number of photons impinging on the asteroid, or increase their effect?
    • Re: (Score:3, Informative)

      by slashping ( 2674483 )
      Increasing the albedo makes the photons bounce back, which requires a bigger change in momentum than just stopping them.
    • by symbolset ( 646467 ) * on Sunday October 28, 2012 @01:18AM (#41794495) Journal

      ...change the number of photons impinging on the asteroid, or increase their effect?

      A photon has energy. When a mass absorbs a photon's energy it has two effects: the mass increases in temperature equal to the energy of the photon, and the mass is accelerated in the direction of the photon's path equal to the energy of the photon. This seems like we're using the photon's energy twice, but it isn't so because thermal energy of a mass is kinetic energy shifted into the time domain. All objects in the solar system suffer this "solar wind" effect. The closer they are to the sun the more its radiated photons push them away. Obviously, the sun is emitting a LOT of photons.

      When the mass radiates the photon again it cools and is thrust again in the direction opposite the direction of the escaping photon. Depending on the rotation of the mass and the average time a photon is held before being emitted again (albedo), this can impact the course of the object. By changing the time factor you can cool the object and impact its trajectory. This is called the Yarkovsky effect []. Dark or fast-spinning objects hold the photon's energy for so long that they are radiated in directions that are relatively random and have zero impact on course but they are hotter. Bright objects have more measurable impacts on course because the energy is released in a predictable direction that is relative to the input a vector related to the object's direction of spin but they are cooler. Believe it or not, you can use colors of paint to impact the period between absorption and emission, and use that to align the thrust opposite to the objects orbit around the sun, or in synergy with it. Our understanding of this effect has grown so great that we can tell an asteroid's mass, density, axis and rate of spin based only on its temperature and changes in its course.

      Derivatives of this feature are helpful in explaining the normal expansion of the universe (not inflation), as photons push masses on each end away. When we observe some galaxy 12 billion light years away, we're absorbing its photons and it's pushing on us ever so slightly.

      The difference can be illuminating. Radio Shack and others used to sell a heliotrope device that was a fan with reflectors on one side of the fins and black on the other. The relative difference in albedo would cause the fan to spin in any normal light.

  • For the same weight, you'll transfer a lot more KE to the asteroid with a marble.

    • The KE is only a small part. The paint will increase the albedo of the asteroid therefore the thrust from the sun.

    • by jo_ham ( 604554 )

      Is that weight under Earth gravity, weight during acceleration to the asteroid, weight during cruise, or weight while it's being fired at the surface?

    • The immediate transfer of kinetic energy is a small effect. The larger effect is a change in the albedo, particularly on a rotating asteroid, because that allows you to affect how the Yarkovsky effect is applied.

      When you change the Yarkovsky effect, it changes a force that is applied along the velocity direction, causing it to speed up or slow down: this is the most effective way to change the orbit in a way to avoid an impact. Because the force is applied for a very long period of time, it can avoid both

  • So I'd better hope the one that's headed for a near miss is black, so it doesn't curve and land on my house. It is senseless to worry about something with such infinitesimal odds, though. We should worry about the baggage retrieval system at Heathrow instead.
  • by runeghost ( 2509522 ) on Saturday October 27, 2012 @06:37PM (#41792313)

    We've known that incoming (and outgoing - the Yarkovsky effect) radiation can alter an asteroid's trajectory for ages. But such a solution needs to be implemented far in advance of any pending impact. At present, we don't know the trajectory of potential impactors, like 9942 Apophis, to sufficient precision to make a deflection strategy like this useful. While it's true the odds are exceedingly small, accidentally putting an asteroid into a dangerous orbit would be disastrous. Apollo astronaut Rusty Schweickart proposed putting a tracking beacon on Apophis in order to further refine its orbit, which would allow us to use such gentle deflection strategies as the one outlined in the article. NASA turned him down. Fortunately, the Russians are currently planning a mission to Apophis; so maybe it will end up getting deflected via a generous application of paint.

  • I'm getting into the paintball manufacturing business on Monday. Look for my Kickstarter project, peoples.

  • I'm not sure if I'm right, but my first thought was "surely the colour doesn't matter, since the momentum of the photons are transferred whether they are absorbed or reflected?". Perhaps someone with more knowledge of the relevant physics can answer.

    In any case, it seems like a very impractical proposal. Shouldn't students be given more useful topics to make studies of?
    • by jamesh ( 87723 )

      I'm not sure if I'm right, but my first thought was "surely the colour doesn't matter, since the momentum of the photons are transferred whether they are absorbed or reflected?". Perhaps someone with more knowledge of the relevant physics can answer.

      In any case, it seems like a very impractical proposal. Shouldn't students be given more useful topics to make studies of?

      I'm not a physicist, but if the overall momentum of the system is constant, and we consider the original state of the system where a photon is headed towards the asteroid, then the alternate resulting states of the system are:

      1. photon is absorbed by the asteroid.

      2. photon is reflected by the asteroid and is now moving in the opposite direction

      and state 2 must have the asteroid moving slower relative to the direction it was hit by the photon to conserve the total momentum of the system.

      Of course photons tra

  • by crovira ( 10242 ) on Saturday October 27, 2012 @06:54PM (#41792431) Homepage

    Imagine your company logo emblazoned across the surface of an asteroid.

    Not only will your company have done something great for all mankind, but mankind will be reminded of it in perpetuity.

    First we paint the whole thing white and then get computer controlled pain ball guns to splatter, like an inkjet printer, your company's logo all over the asteroid.

    Think of watching a Papa John's ad every time you look up in the sky and having to say a little prayer that you can actually enjoy a large nutritious Papa John's pizza instead of having been reduced to a smokin' crater . :-)

  • by jklovanc ( 1603149 ) on Saturday October 27, 2012 @07:09PM (#41792517)

    According to the article the paint would have to be applied 20 years before the asteroid approach. Add to that the time to get the craft to space, load up with paint and get out to the asteroid. That may take another 20 years. That may mean a 40 year lead time at launch to be remotely viable.
    Paint is not a guidance system. Sure it may be able to move the rock around but it will just be in an indefinite direction. It is just as possible to move the rock closer to earth as away. Sure it moves the rock away from earth but into a trajectory that interacts with a planet that pulls the rock back toward earth.
    Other celestial bodies.
    As other asteroids impact or come close to the "rock on question" they will alter the path. As the rock enters the Sol system planets will exert gravitational pull on the rock. The part or all 20 years of movement may be wiped out by interaction with another object.

    To me the only viable option would be to land thrusters on the rock. Use them to stop the rotation (if any), re-position to one side of the rock and apply constant thrust to alter the course. The thrusters would have to be ion based (low fuel, long duration) and probably powered by solar satellites. A solar sail could be added for additional thrust once the rotation has stopped. The issue with icy asteroids can be dealt with by limiting the thrust of the engines so as not to break the asteroid.

    If the rotation was not stopped it would require many more thrusters as they could only fire part of the time.

    This "proposal" sounds like "paint and pray".

  • by jamesh ( 87723 ) on Saturday October 27, 2012 @07:25PM (#41792679)

    The Society Of Protection of Asteroids (SOPA) will not stand for this. Anything that stands in the way of an asteroids natural path is against nature and against God.

    We're going to have to move the Earth out of the way instead... how much paint is that going to take?

  • I can't believe this would perform better pound for pound than high explosives
  • When playing Paintball in space, you will be pushed backwards by the recoil too

  • Among the many other problems already listed is whether or not paintballs will pop at 2.7 degrees kelvin.
    • by tftp ( 111690 )

      Among the many other problems already listed is whether or not paintballs will pop at 2.7 degrees kelvin.

      If you are going to apply the paint that far away from the Sun then yes, it will be a concern. Obviously, liquid paints will not work since only liquid Helium will be still liquid at that point. So you will need powder paints. The next question is how do you hold the paint there. Electric charge would be one interesting method, but will it last? Without some sort of adhesion the only force you have is

  • Paintballs, eh? The big brains who work on this think that the best thing to do is to launch an ~2-ton spacecraft with an ion engine, position it near the asteroid, and let them do their gravity tango while the spacecraft very slowly changes the orbit of the pair. If it's a nice asteroid, that orbit is one that parks it in Earth's orbit for mining operations.

    As compared to painting the asteroid, if the asteroid tumbles at all (space dust, uneven heating, evaporation, etc.) the entire plan doesn't fall apa

  • If this worked other civilizations would have used it and every once in a while we'd see a painted asteroid go flying by. Right? RIGHT GUYS!?

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