How To Save the World From Asteroid Impact: Plastic Wrap


Remember a competition we reported on back in April called “Move An Asteroid”? It was an international technical paper competition looking for unique and innovative concepts for how to deflect an asteroid or comet that might be on a collision course for Earth. The winners have been announced and first prize went to Australian PhD student Mary D’Souza who came up with quite a novel concept: wrap the asteroid with reflective sheeting. Such a coating may increase the asteroid’s reflectivity, enabling deflection by solar radiation pressure.

The asteroid in question, known as Apophis, will pass close to Earth in 2029. Although the 207 meter- wide Apophis is not expected to impact Earth, its current trajectory has it approaching Earth no closer than 29,470 km (18,300 miles), which is well inside the orbit of the moon. This, in conjuction with the 100th anniversary of the Tunguska explosion, was the impetus behind the competition.

D’Souza’s paper was titled “A Body Solar Sail Concept for the Deflection of 99942 Apophis.” Her concept involves using a satellite orbiting Apophis to wrap it with ribbons of reflective Mylar sheeting. Covering just half of the asteroid would change its surface from dull to reflective, possibly enough to allow solar pressure to change the asteroid’s trajectory.

“What happens then is light from the sun shines on the body [of the asteroid] so more of it is reflected … and it actually acts to move it away from the sun and the earth,” said D’Souza, a student at University of Queensland’s School of Engineering.

The competition was sponsored by the Space Generation Advisory Council, a group representing youth perspectives on space exploration to the United Nations and national space programs. SGAC said they received submissions to the competition from all over the world. “It is great to see such an interest in this topic from young people all over the world. Hopefully with competitions like this, SGAC can further increase the involvement of youth in this important field of current space research,” said Alex Karl, Co-Chairperson of the SGAC.

By winning the competition, D’Souza will travel to Glasgow at the end of September to present her plan at the International Astronautical Congress.

Second place was awarded to Andrew Bacon of the Department of Electronic and Electrical Engineering at the University of Bath for his paper entitled “The Use of Electromechanical Resonators for the Mitigation of Earth Threatening Asteroids and Comets.” Bacon’s concept involves the use of electromechanical resonators to build up waves within an asteroid or comet that would break it up. He will also present his plan at the IAC.

Sources: Space Generation press release, The Register

43 Replies to “How To Save the World From Asteroid Impact: Plastic Wrap”

  1. How about bombs with freezing agent attached which wouldnt explode but freeze the asteroid. Then if whatever force were to be applied to said asteroid it would shatter into a million peices.

  2. Actually, a solar sail would do pretty much the same thing as wrapping it in shiny fabric. Both work by radiation pressure.

    An alternative tactic could be to effectively paint the asteroid black, which would make use of the Yarkovski effect (which naturally tends to dominate over radiation pressure for objects that size). Same concept, different effect.

  3. How would one ensure that the push is in the right direction? It would quite the downer to realise that it gets closer to Earth, once the wrapping’s done.

  4. The only technology we have right now, and will have in the near future, would be fusion bombs.

    Not sure why people are trying so hard to figure out something different.

  5. I wonder how much fuel is required to capture an asteroid 200 meters in size going 30.728 KM/s. I mean slow it down to a complete stop.


  6. If we can deflect it, presumably where we want, why not nudge into a more ‘user friendly’ orbit? Say an orbit around the sun that is close to earths orbit, but not TOO close. Then we could mine or inhabit it. At least we could visit it on flyby to put some scientific instruments on it. Cjeck out the solar system, maybe the Oort cloud. Or how about sending politicians, lawyers and bureaucrats and other ne’re-do-wells on the trip of a lifetime? Seed the universe with life.

  7. @ Sili

    Well, if the asteroid *is* going to hit the Earth moving it anywhere would probably move it off target so I guess it shouldn’t matter where it gets pushed. I guess… As long as the pushing starts with enough of a time margin we should be OK.


  8. @ Joe

    First of all the question is incorrectly posed. For one thing we would need to decide to stop the asteroid in relation to what. Second, an asteroid’s size doesn’t necessarily define its mass. And third, which fuel? For this exercise I’m going to assume we are talking about Apophis which has roughly this size and has the mas of 2.1e10kg and for fuel I’ll take regular gasoline. Imparting a speed delta of around 31000000m/s to an object like this takes (mv^2)/2= (2.1e10*31000000^2)/2 which is around 10^25Joules. According to Wikipedia regular gasoline has an energy content of 34.8MJ/litre ( which gives something like 2.9e17 litres of gasoline. So that’s your answer (if the math is right, I’m a bit tired right now). Someone else will have to translate it in something more imaginable, like compare it to the size of the Earth or all the water in all the oceans but it sounds like a *lot* of gasoline.

    Kind regards,

  9. Perhaps Tunguska was actually a natural gas explosion caused by abiotic oil seeping out of the ground.

    By volume the ratio is 2(O2)-1(CH4)

    1 megaton = 4.184×10^15 Joules

    5-15% methane in air is considered explosive

    Energy released by methane = 802 Kj/mol = 802×10^3 J/mol

    20.92 |TJ| / 802 |Kj/mol| =2.608×10^10 mols of CH4

    5.217×10^10 mols of O2

    Oxygen in air is 20%, and assuming that 5-15% ratio displaces only the nitrogen.

    2.608×10^11 mols of air molecules is involved.

    If that is uniformly spread out, then assuming 41.4 mol/m^3 for dry air

    You end up with an explosion requiring approximately 6.301×10^9 m^3 of air/fuel mixture at STP. That’s a cube of about 1.847 kilometers in all directions in order to give you 5 megatons of energy from this reaction.

    Tunguska was an area of 2000 km^2 = 2×10^9 m^2

    So the amount of methane/air mixture in such an explosion would have been about 3.15 meters high off of the ground (save for all the imprecision in my assumptions)….anyhow, that seems reasonable for the damage done.

    (doesn’t it make sense that 1625 metric tons of methane gas needs to be combusted to yield 5 megatons energy equivalent of TNT?)

  10. Adam, your assumed speed for apohis is too large. mean velocity is 31km/s = 31000m/s. The required energy is according to above formula ~1×10^19 J which is 2,8×10^11 liters of gas.

    A shuttle external fuel tank has a storage space of 554m^3 LO2 and 1515m^3 LH2, roughly 2000m^3 altogether = 2 Million liters uncompressed liquid (our gasoline), so it would take 140 thousand external shuttle fuel tanks full of gasoline.

    According to wikipedia, a modern refinery ‘requires’ ~ 4 liters crude oil for 1 liter engine gasoline. The US consumes ~ 20 million barrel oil daily = ~ 3.2 billon liters oil daily, that makes 800 million liters gasoline. That means 350days of US gasoline production would be needed.

  11. But of course the those figures are plain theroy, no machine can harvest the full potential of chemical energy carriers. the yield by combustion is very poor, the rest is just wasted. and in space, there would’t be any adequate machine to transform the energy of gasoline into an impulse.

  12. Why are you guys talking about this stuff? How much of a chemical explosive it’ll take to move an asteroid really has a distant relationship to the article at hand.

  13. DuddleyFuddle wrote:

    “Or how about sending politicians, lawyers and bureaucrats and other ne’re-do-wells on the trip of a lifetime? Seed the universe with life.”

    I like this idea! The hot air alone should move the asteroid out of harm’s way. (OK, I know, it won’t work in a vacuum.)

    On the other hand, intelligent aliens might not like the idea of Earthlings dumping their garbage in their space.

  14. I think everyone is forgetting the most important point. This is an opportunity to send astrosnauts/cosmonauts to an asteroid that is presenting itself for easy access.

    Fly a spacecraft (Orion?) to the asteroid, plant laser mirrors, seismomitors and take samples from the body.

    If Apophis does hit the resonance keyhole, just put a small engine or solar sail on it and you would never have to worry about it again.

    It would be a great dress rehersal for a really big threat.

  15. Solar sails and other methods – see
    ( )
    Painting the NEO white or sliver…
    “with such a reflector it is hard to steer — it can only apply a force directly away from the sun, which is the least helpful direction” (it would still work, give enough lead-time and some clever calcuations on timing)
    In any case, congratulations to Mary and the other competitors.

  16. “I like this idea! The hot air alone should move the asteroid out of harm’s way. (OK, I know, it won’t work in a vacuum.)”

    I agree. But for greatest satisfaction, maybe we should ship them all there, but when they get there we use a railgun to shoot them all off one by one at extraordinary velocities in metal tubes. Into Jupiter. And as the asteroid soars out of the solar system, it will carry news of our new utopia to extraterrestrial civilizations along with instructions on how to accomplish the same feat.

  17. The only technology we have right now, and will have in the near future, would be fusion bombs.

    Not sure why people are trying so hard to figure out something different.

    Because nuking an asteroid might not work as intended. With nukes you get very different results with relatively small changes in the initial conditions (like how solid the asteroid is, where your bomb explodes, on impact, above the surface, after penetrating, etc.), and you may even cause more havoc than you would if you just let the asteroid hit the planet.

    The safest way to deflect asteroids seems to be to push them gently out of the way. Of course, this would only work if you had the time and knew fairly well its orbit with years to spare. Which is why places such as Arecibo are of paramount importance.

  18. Forget plastic wrap. We should use the universe’s largest roll of duct tape.

    Because as well all know…

    Duct tape solves every problem, big or small!

  19. Wrapping an asteriod with reflective material may sound like a good plan (they needed a contest to figure that out? hmm…), but in the long run it may not be as effective as sticking some sails to it. Wouldn’t the solar energy/radiation/wind affect the asteriod even without the reflective coating.

    A question: what would be the difference to a nuke detonated a distance from an asteriod, so the explosion wouldn’t damage the asteriod much-to detonating one on the surface of said asteriod?

  20. hey why not go the whole hog and use bubble wrap?? it would cushion the blow if if the asteroid didnt move enough and did crash into us 🙂

  21. @ntoskrnl

    Oops! I didn’t realize that point was a decimal point and I didn’t check that piece of the Apophis data myself. Anyway it sound’s like a lot less volume than I would expect. Thanks.


  22. @Andrew

    “Why are you guys talking about this stuff?”

    Well, the question was asked so why not try to answer it? Perhaps this is not the kind of knowledge our civilization really needs most of all for the moment but it is a nice little trivial exercise.

  23. At 207m diameter, would it have enough gravity to allow a craft to get into an orbit? And a close enough orbit to reliably wrap the plastic? I’m sure I did this physics in high school & I’m sure she did the calcs…..

  24. How about putting monitering cameras onto asteroids then after they come back to Earth from going on there incredible journeys we could retreave info about other objects out there.

    With blowing an asteroid up you would have to get the pieces away from each other so they dont constitute the same big one that wouldnt disintergreat on contacting our atmosphere.

  25. What about adding an artificial sattelite or “moon” to the asteroid? Gravity could then perhaps change the path of the new system – eventually assisted by some engines?
    (this is only a “blind shot”, without any calculations)

  26. I really like all the ideas so far. Working in the right direction, but need to point out a few things.
    No amount of gasoline will work in space, without something to oxidize the area it burns in, and then you need to create a combustion chamber for working it; in other words… it is about as efficient as using a dozen mice.

    Sails are a great idea, but remember you are in space. Sails will do a better job of putting the asteroid into a rotation along the angular axis. Think of a really large sail on a boat without a keel. It will flip right over. In space, you are lacking the keel… so you need a solution for it as well. Adding another opposite of the first doesn’t work as well as you might think either… but along those lines is something which could work.

    The idea of wrapping the asteroid in reflective material isn’t bad; if there is time for it to work, it’s simplicity really scores big points from the engineering crowd.

  27. @Brian

    If I understood this correctly, a distant explosion would simply hit the asteroid with a huge amount of radiation, probably causing the vaporization of a relatively thin coat of surface material and maybe pushing it a little bit in the opposite direction. A very little bit. There wouldn’t be the shockwave there is on Earth due to the lack of atmosphere, so the devastation associated to it wouldn’t happen. I don’t think one such explosion can disrupt an asteroid, even if it is just a rubble pile like Itokawa… unless it’s a potent blast and/or a close one. The closer you get your explosion, the larger its effects, I believe. In any case, unless your asteroid is pretty small, the kick would be quite small.

    A superficial blast would vaporise a considerable amount of material, possibly giving a strong push to small asteroids, but having little effect in larger ones’ orbits. But it would also cause a serious seismic activity and the probability of disruption would get much higher.

    We don’t want that. We want the energy we apply being used to change the asteroid’s orbit, not to break it apart, because having several big asteroidal chunks coming our way is hardly any better than having just one. We’ve seen what can happen when you have a broken small body hit a planet when Shoemaker-Levy 9 slammed into Jupiter. Not a nice sight.

    If I understood this correctly. I’m not sure I did. I think I have the right general idea, but some of the details may be off.

  28. @Drew

    In principle, you can orbit anything, if your mass is significantly lower than the one of the thing you’re orbiting and your velocity and distance are the right ones. If you’re a particle of dust, you may be able to orbit an astronaut, for instance.

    Still, you don’t have to go round and round the asteroid to wrap it up. You can do it using the same principle used in throwing nets: weights along the extremities of your wrapper can be used as projectiles, fired in such a way that when the central part hits the asteroid it’ll wrap on its own momentum.

  29. Hmm . . . I wonder if the SGAC would have awarded PhD student Mary D’Souza the travel prize if she were, let’s say, a 16 year young high school “C” average student with exactly the same novel presentation. By the way, the math doesn’t support D’Souza’s reflective sheet fancy.

  30. ^ Agreed – for any spacecraft of significant size it’s probably easier to use a harpoon or similar device to anchor to the asteroid rather than wasting fuel trying to establish an orbit.

    Just match relative velocities, slide up beside it like you were going to do a flyby, and then firmly connect a cable from ship to rock.

  31. @Tyler

    When you have connected the cable from the ship to the rock and since you have matched relative velocity, why not use the ship’s thrusters to pull on the anchored cable and change the direction of the asteroid.


  32. Er, there’s no such thing as a “fusion” bomb. Thermonuclear bombs use fusion, yes, but the primary release of energy is from fission. Fusion merely speeds up fission the process.

    Nobody has been able to sustain a fusion reaction.

  33. I like Markus’ comment.

    By the time Apophis passes close to Earth in 2029 we should have the ability to engineer a way for it to go into orbit around the Earth/Moon system.

    What a wonderful opportunity!

  34. Cable teathers don’t work the same in space, as they do on Earth. Even if we could create a cable strong enough, the mass and angular momentum of the asteroid would pull the vehicle back and send it crashing into the asteroid, dragging it along flying behind it or tear the vehicle apart (like pulling the bumper off of a car). At best, it would put the asteroid in a sort of “flat spin” but wouldn’t change its direction.

  35. I like the idea of trying to capture it and putting it to use. Since it’ll be between us and the moon and we want to push it farther away, why not nudge it into a lunar orbit? If that’s not feasible, then a nudge that’ll bring it within slingshot range of other planets for a later capture? NASA could sponsor similar contests (with actual prizes) and maybe get lots of ideas that could be used in tandem for greater efficacy? I see a huge opportunity here, not a missile target.


  36. To much focus on how to deflect the asteroid!

    Instead try to slow down or speed up earths speed by 1 meters/hour or maybe even 0.1 meters/hour
    In time distends felled behind will be enough to avoid impact by asteroid.

    So when speed/slowed down enough Slow/speed it back up the same way, by then earth will be moved from the asteroids path and we wont feel the smallest change in earths orbit.

    But is it possible?
    I don’t know maybe with some precise nuclear explosion

  37. To much focus on how to deflect the asteroid!

    Instead try to slow down/speed up earths by 1 meters/hour or maybe even 0.1 meters/hour
    In time distends felled behind/gained will be enough to avoid impact by asteroid.

    So when slowed down/speed up enough, Speed it up/slow it down back the same way,
    by then earth will be moved from the asteroids path, and we won’t feel the smallest change in earths orbit.

    But is it possible?
    I don’t know maybe with some precise nuclear explosion

  38. Boy, I sure hope their numbers are right! 21 years in the future seems like a long way off to predict an orbit with that kind of accuracy. And, even if they’re only slightly off, this article could take on a whole new significance.

  39. I say we aim it at the Moon as the first step towards terraforming it. The impact would be the first of many to create tectonic activity inside the core. It would also plant needed volatiles at the impact site and spread a tenuous atmosphere, assuming Apophis has significant quantities of CHON.

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