Chinese propose method for deflecting asteroid Apophis
August 22, 2011 by Bob Yirka
Orientation of the sail cone and clock angles. Image: arXiv:1108.3183v1 [astro-ph.IM]
(PhysOrg.com) -- Chinese scientist Shengping Gong and associates at Tsinghua University in Beijin have proposed an alternative method of deflecting the asteroid Apophis to ensure that it does not strike the earth. They believe that rather than just blowing it up ala the European Space Agencys Don Quijote project, a better approach would be to use a solar sail, as described in their paper on the preprint server arXiv, to slowly nudge the asteroid off its trajectory just enough to keep it from bothering us here on Earth.
Apophis is approximately 880 feet in diameter and weighs an estimated 46 million tons. If it were to strike the earth, it would most certainly cause damage for thousands of miles around the epicenter, but wouldnt spell doom for the planet as a whole.
First discovered in 2004 by Roy Tucker, David Tholen and Fabrizio Bernardi at the Kitt Peak National Observatory, Apophis was after initial study, thought to have a possibility of hitting the earth; then after further study, it appeared that an impact was unlikely. Then later it was noted that when Apophis makes a close approach in 2029, there is a possibility that it could pass through what is known as a keyhole (a small gravitational zone near enough a planet to alter the course of an object) near our planet that could cause the next pass, in 2036, to hit us. Because of the dizzying number of variables involved in such a scenario, however, there appears to be differing views as to the probability of that actually happening. There also seems to be some disagreement as to the origin of its name; some suggest that Apophis comes from the ancient Egyptian deity, enemy of the uncreator Ra, Apep. Others suggest its simply a nod to the character Apophis on the television show Stargate SG-1.
In either case, Gong et al, propose using a space vehicle propelled by a solar sail that would move in a retrograde (opposite) orbit relative to Apophis fast enough so that when the collision occurred (like two cars running head on into each other on a freeway) the vessel would strike the asteroid moving at a relative speed of some 55 miles per second, enough they say, to push the offending asteroid off its current path.
The problem is, as the Chinese group readily admit, is in being precise enough in aiming the vessel. With all the variables at play (including the years it would have to travel) it would seem an almost impossible task. Nonetheless, the team seems undaunted, suggesting that such a vehicle could be built and launched in the time frame available.
More information: Utilization of H-reversal Trajectory of Solar Sail for Asteroid Deflection, Shengping Gong, Junfeng Li, Xiangyuan Zeng, arXiv:1108.3183v1 [astro-ph.IM] http://arxiv.org/abs/1108.3183
Abstract
Near Earth Asteroids have a possibility of impacting with the Earth and always have a thread on the Earth. This paper proposes a way of changing the trajectory of the asteroid to avoid the impaction. Solar sail evolving in a H-reversal trajectory is utilized for asteroid deflection. Firstly, the dynamics of solar sail and the characteristics of the H-reversal trajectory are analyzed. Then, the attitude of the solar sail is optimized to guide the sail to impact with the object asteroid along a H-reversal trajectory. The impact velocity depends on two important parameters: the minimum solar distance along the trajectory and lightness number. A larger lightness number and a smaller solar distance lead to a higher impact velocity. Finally, the deflection capability of a solar sail impacting with the asteroid along the H-reversal is discussed. The results show that a 10 kg solar sail with a lead-time of one year can move Apophis out of a 600-m keyhole area in 2029 to eliminate the possibility of its resonant return in 2036.
Via ArXiv blog
© 2011 PhysOrg.com
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Aug 22, 2011
Rank: 1 / 5 (6)
btw, why are we going to carefully ram an asteroid when an explosive charge achieves a more certain outcome?
Aug 22, 2011
Rank: 3.2 / 5 (10)
Aug 22, 2011
Rank: 2.3 / 5 (3)
Aug 22, 2011
Rank: 4 / 5 (4)
Aug 22, 2011
Rank: 3 / 5 (1)
I wonder if simply blasting off a clean spot on one side might be enough. If you open up a fresh patch on one side of the surface, then the sun should do the rest, as it passes through parihelion. The fresh spot should outgas much more than the dirty old suface elsewhere.
Aug 22, 2011
Rank: 4.9 / 5 (8)
It not only shows some foresight but it doesn't even matter whether it works or not, it will still lead to a lot of advances and further our knowledge.
Aug 22, 2011
Rank: 3.7 / 5 (3)
Aug 22, 2011
Rank: 3.7 / 5 (3)
Aug 22, 2011
Rank: 3.8 / 5 (5)
For example? What did we mess up?
Seriously, do you really want to wait until we find an asteroid that has a high chance of hitting us and then try to deflect it using methods that have never been tried before? I'd rather have a test case.
Come to think of it: Can't we make it a little friendly competition?
First the chinese are taking a shot at it with their solar sail and then ESA takes a more literal shot at it and we see which technique works best? That would certainly be interesting.
Aug 22, 2011
Rank: 4.7 / 5 (15)
Aug 22, 2011
Rank: 1.7 / 5 (3)
Aug 22, 2011
Rank: 4.8 / 5 (5)
You have to understand the current state of things. Apophis will pass extremely close to earth in 2029, but will miss by about 4000 miles. It will come very close again in 2036. How close? Depends on a lot of factors, pressure of sunlight, spin, how much drag Earth's atmosphere causes in 2029 (yes, it is very thin at that altitude, but...), and so on.
So there is a very small window, that if Apophis passes through in 2029, it will hit in 2036. The problem is not so much that we don't know where Apophis will be at its nearest point, but that we don't know where the window will be.
The three sensible approaches are 1) be ready to hit it if we figure it went through the window, 2) hit it hard enough in 2029 or before to insure that it misses the window, 3) get lots better data. Obviously the last one should be combined with one of the others.
Aug 22, 2011
Rank: 1 / 5 (7)
it won't be like the movie armageddon, no one is landing on the asteroid. they will propel themselves into the asteroid by hitting it head on. the combined speed of the asteroid and the nuke missiles which will be designed as bunker busters with depleted uranium breaching heads, will bury these things deep enough for them to begin exploding the asteroid from the inside out.
a 50 megaton nukes is going to do quite a bit of fragmenting to the asteroid. the remaining pieces will not pose as serious a threat as their increased surface area results in many of them exploding in the atmosphere rather than hitting the surface or the ocean.
Aug 22, 2011
Rank: 1 / 5 (3)
That would totally defeat the purpose. The solar sail design by Gong et al seems to be to increase the impact velocity of the interceptor, not to land safely. I think their idea is to knock it off course by hitting it hard enough, rather than blowing it into a million little pieces. I'm with Jeddy on this. Best to drop a bunker buster in and see where the pieces go. This should be a good test, even for a bigger asteroid, to see what our nukes will do.
Aug 22, 2011
Rank: 2 / 5 (2)
Aug 22, 2011
Rank: 4 / 5 (9)
And many others will cause planet wide bombardment.. and no second chance to move the cloud out of the way.. Great idea..
Aug 22, 2011
Rank: 1.8 / 5 (5)
Aug 22, 2011
Rank: 1.7 / 5 (6)
I'm with the nukes. Let's blow it up. And send a satellite after the bombs with a camera and make it a pay-per-view event.
Aug 22, 2011
Rank: 2.8 / 5 (5)
Aug 22, 2011
Rank: 3.8 / 5 (5)
This would let you get some close-ups of Apophis ahead of time to be able to tell exactly what it's made of and how to deal with it.
Aug 22, 2011
Rank: 1.3 / 5 (3)
Aug 22, 2011
Rank: 5 / 5 (11)
As for detonating a nuke near the asteroid rather than inside it, that would do almost nothing to it. The amount of physical force from a nuke in space is minimal even at short distances. Most of the energy from a nuke is in the form of light. If you've ever seen video of tests here on Earth, the initial flash will peel paint, but won't damage metal under the paint. The physical damage doesn't come until the air pressure shock wave. There would be no such shock wave in space. You might make one side of the asteroid smoke, but it would be inconsequential for the asteroid.
Aug 22, 2011
Rank: 5 / 5 (5)
"Luke, what's wrong? Why have you turned off your targeting computer?"
Aug 22, 2011
Rank: 5 / 5 (7)
"It keeps saying 'A problem has been detected and your system has been shutdown to prevent damage.' I thought you said we converted to Linux!"
Aug 22, 2011
Rank: 1.5 / 5 (2)
NASA's space nagivation is incredibly perfect.
The analogy they use for sending the Spirit and Opportunity landers to mars and actually landing successfully in the target zone was that it was like taking a basketball and shooting from San Francisco to New York and hitting nothing but net.
I figure detonating a 50 megaton nuclear device will only change Apophis velocity by about 0.5m/s, even if 100% of the yield went into net thrust...
If done early enough, this could allow the object to totally miss, but you also have to consider future encounters...
0.1m/s and for 25 years would change it's position on the closest encounter by 78,840km or over 12 earth radii...
Aug 22, 2011
Rank: 5 / 5 (6)
www.bio.aps.anl.g...ard.html
Aug 22, 2011
Rank: 4 / 5 (4)
Aug 22, 2011
Rank: 1 / 5 (1)
Your maths and pocket calculators (super computers)are not up to the task.
In 2029 pocket calculators and maths may have advanced enough to track the object to your satisfaction. Place a sender on the object in 2029. See if a 'skip stone' scenario presents a possibility for 2036.
'Skip stone' mechanics only depends on how much confidence you have placed in your maths, pocket calculators and sender.
Regardless of outcome, we will see how much confidence was placed where and for what.
Aug 22, 2011
Rank: 5 / 5 (10)
(I expect I'll get loads of 1's now... bring it on)
Aug 22, 2011
Rank: 1 / 5 (1)
" I expect..." - malapropism
At the expense of my shame I'll disappoint your expectations.
Eventually, I get over my shame, and you will get over being traumatized for people not meeting your expectations.
Aug 22, 2011
Rank: 1.4 / 5 (9)
Now the Chinese Farmers think they know better.
They better concentrate on fixing the milk and
leave the orbital calculations to the big boys.
See you in 2060 guys. ~ after the Great China Crash.
Please stay away from asteroid before
you screw up the milk again.
JH
Aug 23, 2011
Rank: not rated yet
Who doesn't know that the character Apophis also got his name from the same Egyptian God? Infact, they have named the character so, to create the illusion of that he actually _is_ the egyptian god himself.
Aug 23, 2011
Rank: 1 / 5 (1)
One problem is that the 'more certain outcome' of explosive impact creates many many more bodies capable of possibly more damage over a wider area. Thank the forces that be that the Pleiades comet remnants are basically tiny chunks of ice!
Aug 23, 2011
Rank: 5 / 5 (2)
Aug 23, 2011
Rank: 1 / 5 (1)
We could also use it to anchor a space elevator...
Aug 23, 2011
Rank: 1 / 5 (2)
Aug 23, 2011
Rank: 5 / 5 (1)
Aug 23, 2011
Rank: 1 / 5 (1)
I have a feeling that Russia is in cahoots with Mars by the report card for the first 15 attempts.
Aug 23, 2011
Rank: 5 / 5 (6)
I think my head might explode or short circuit like the androids on "I Mudd", faced with the liar's paradox, from that comment.
http://en.wikiped.../I,_Mudd
I'd really like to give you a 1, but I am forced to agree with your comment that you deserve a 1, and therefore must give you a, give you a, give a, you, give, give, give.....Ahhhhhhh!
Aug 23, 2011
Rank: 5 / 5 (3)
Aug 23, 2011
Rank: 1 / 5 (1)
Personally, I think it should be bagged (think Kevlar fishing net) several days before first approach, but now it's too late to mount the mission, if it shreds. If it doesn't shred, the bag provides a handle for later solar sails.
Aug 24, 2011
Rank: 5 / 5 (1)
Lets get to harvesting asteroids already. Quit talking about blowing it up, lets build stuff with it! Thanks for saying what I was thinking Malapropism
Aug 24, 2011
Rank: 5 / 5 (1)
Apophis is almost certainly a solid rocky object. To say that it would be affected by the Roche limit is like saying that a boulder of similar size and composition here on the surface of the Earth should also fall apart. Obviously this does not happen, despite boulders on the surface being much closer to the center of gravity. There are plenty of solid rocky objects here on Earth that do not fall apart under gravity.
Your idea is nonsense.
Aug 24, 2011
Rank: 3 / 5 (2)
Aug 24, 2011
Rank: 5 / 5 (1)
Yes. And while we're at it let's add some fretwork and paint it pink. (to be clear: the answer is 'no')
Even if it were yes then using a nuke does not mean you pulverize somethnig. It might just break into a lof of pieces (or just two) and keep on its way.
A nuke could be used on the surface to give it a nudge - but that's about the extent of use a nuke would be. The disadvantage is that a nuke is not a very controllable way of changing its course, and in that respect we want good control (which both an impactor and the chinese idea give)
Aug 24, 2011
Rank: 5 / 5 (1)
Anyway. As ap just said, "a nuke could be used on the surface to give it a nudge". But I think it would be good to try it anyway to better understand what it would do. We should be careful about it, probably better to hit an asteroid that isn't careening toward the planet. But still an experiment that we should do to see what we can resort to in a worst case scenario.
For all the "space junk" and scary tiny little rock litter talk. Nonsense. Again. Space is really really big. I know I've linked this before, but...
www.youtube.com/w...-gs0WoUw
Aug 24, 2011
Rank: 4 / 5 (1)
If we can do it, I like the idea of chucking asteroids at asteroids so that we're throwing several tons at the incoming rather than puny probes.
Aug 24, 2011
Rank: 4.5 / 5 (2)
We landed a spacecraft on an asteroid way back in 2001. Google Eros. And, I believe, the Chinese have done it more recently.
Aug 24, 2011
Rank: 5 / 5 (1)
Aug 24, 2011
Rank: 5 / 5 (2)
Universe Today had this kinda related article yesterday:
http://www.univer...re-88384
Aug 24, 2011
Rank: 5 / 5 (2)
Thanks for the link (I was about to add it). The discussion seems quite relevant (and detailed) for this NEO topic. Do check it out.
Aug 24, 2011
Rank: 5 / 5 (2)
Aug 25, 2011
Rank: 5 / 5 (2)
Great link. It is papers like this that make me really wish I were a grad student instead of a working stiff. How cool would it be to spend several months calculating how to capture a 10 meter chunk of the 4.5 billion year old left overs from the formation of the solar system?
On second thought maybe cool is the wrong word? Sign me up all the same.
Aug 25, 2011
Rank: 5 / 5 (2)
We have.
List of craft that have done flybys, impacts and taken samples can be found here:
http://en.wikiped..._targets
The Rosetta probe is currently on the way to orbit a comet:
http://en.wikiped...craft%29
Aug 25, 2011
Rank: not rated yet
Aug 25, 2011
Rank: 5 / 5 (1)
Dawn(Vesta): http://en.wikiped...craft%29
NEAR Shoemaker(Eros): http://en.wikiped...hoemaker
These missions are "very tricky" but they have been accomplished.
Aug 25, 2011
Rank: 3 / 5 (1)
Aug 25, 2011
Rank: 5 / 5 (4)
Why would they want to get rid of their biggest customer??
Aug 26, 2011
Rank: 5 / 5 (4)
And their biggest debtor. Not much chance of getting all that money back if you destroy your debtor
It would be foolish of them to smash an asteroid into what is effectively their property until the US pays off its debt - which seems unlikely to ever happen.
Aug 27, 2011
Rank: not rated yet
ideally, one could find a similar size object moving in a similar direction to earth as the one we are afraid of and just test out a thermonuclear explosion that we denotate directly upon the front surface of the object with a bunker buster. and or with one directly in front of the object, or perhaps to a direction at an angle to the asteroid to steer it away from its current course.
maybe 2 nukes should be sent .one to blow it up, the next to redirect its ( and the pieces of it course. ) the second nuke could be redirected based on the results of the first.
the data from a test like this would be enormously useful. especially if we used 100 megaton thermonuclear devices.
Aug 27, 2011
Rank: not rated yet
Movies anyone?
Aug 27, 2011
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Aug 28, 2011
Rank: not rated yet
LOL! I'd call Hollywood and have someone re-write the script.
Aug 28, 2011
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Aug 28, 2011
Rank: not rated yet
Blowing it up is a bad idea, as the rubble trajectories will be unpredictable (and therefore potentially even more dangerous). Nukes could "nudge" it, but who really wants the resulting radioactive cloud(s) raining down? And trying to launch, land, fuel, and deploy heavy lift rockets to it is so logistically impracticable as to be impossible.
Therefore, the most practicable solution offered in this thread is to toss Mel Gibson at it.
Of course I don't literally mean we should toss Mel Gibson himself (as beneficial as this at first seems), but rather we should toss stuff at it. Lots and lots of relatively low mass stuff, over time. Preferably, reaction mass (conventional explosives).
Just mass produce a bunch of rockets and launch them at it regularly.
The gravity is low enough that even conventional explosives should (in relatively short order) blow enough mass away (at escape velocities) to effect a sufficient change of momentum.
Aug 28, 2011
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What happens if we blow it to pieces on it's way back out to the outer solar system after it passes us?
Aug 28, 2011
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Aug 28, 2011
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Aug 29, 2011
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Just sayin' what? That you like to play video games? That certainly has given you the skills and insights to be the savior of humanity. Well done.
Aug 30, 2011
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Oct 09, 2011
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Oct 10, 2011
Rank: not rated yet
Maybe I'm missing something in your comments, but I'm getting the sense that you're saying they don't teach anything about restrograde orbits, when it's well known that you have to use a retrograde orbit to send a spacecraft toward the inner planets of our solar system...
Oct 21, 2011
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Oct 21, 2011
Rank: not rated yet
http://news.disco...ids.html
If the explosion of an interceptor nuke will be too small, the asteroid will reform under its mutual gravity again. In general, I'm against such socialistic attempts to affect the asteroid path, until the uncertainty level in determination of their exact path is a much lower, than the effect of various methods of asteroid deflection.
We shouldn't forget, these plans are enforced with limited number of people, who are primarily interested in development of military rocket technology and the fight against asteroids is just an evasion for their activities.
Oct 21, 2011
Rank: not rated yet
So? The point would not be to blow it up (besides: we don't have nukes that can blow up anything that is larger than 100 meters in diameter, anyways)
The point would be to deflect it. If it reforms (on a slightly altered path because of the added impulse of the nuke blast) then that wouldn't matter. Actually that would be very good since it would mean that there would not be a wide swath of 'shrapnel' that could contain large enough objects to reach the Eart's surface or take out a bunch of sattelites.
What in the world does any of this has to do with the attribute 'socialistic'?
Oct 21, 2011
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http://www.space....eat.html
Oct 21, 2011
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You, sir, are a very confused indvidual.
Oct 21, 2011
Rank: not rated yet
http://en.wikiped...e_Treaty
So, when Russians failed with this plan, they announced the managed mission to Mars, which would use the nuclear engine, again. It's all just about expansion of nuclear arms race into cosmic space - but the people, who don't understand the political motivations of these proclamation will still believe, the China and Russia just want to save the world.Such response just indicates the lack of arguments from your side..
Oct 21, 2011
Rank: 5 / 5 (1)
Even if some risk would exist here, then the uncertainty in Apophis path is much higher, than the uncertainty of the methods, which China wants to use for Apophis deflection. In another words, there is high probability, whatever well minded action of Chinese will just make the things a much worse. If we want test various methods of asteroid destruction/deflection, then we shouldn't use a potentially dangerous asteroid for such game, or we could all become a hostage of some limited group of people, who are out of public control.
Oct 21, 2011
Rank: 1 / 5 (1)
Oct 21, 2011
Rank: 5 / 5 (1)
@Zephyr said:
Comment worthy of a ten! And then...
Proving ap's comment. Or maybe it should be delusional rather than confused. But hey, at least you picked a world saving piece of pseudo science rather than just your aether that isn't. I agree with you though. The research into cold fusion should probably include launching Rossi into the vacuum at Apophis.
Oct 21, 2011
Rank: not rated yet
The small, but nonzero value is still infinitely-times more valuable, than the pure dumb zero. The mainstream research of cold fusion simply sucks and we just ask, who is responsible for it - and deduce the consequences. How much money (not to say about life environment destruction) we are potentially losing with ignorance of cold fusion research each day? Who will pay for it?
Do you believe, you lost your home during financial crisis because of high oil price and speculations of billionaires? Maybe we forget all these "poor innocent" physicists, who are effectively blocking any research of oil fuel substitutes. We should call the things with their true names.
Oct 21, 2011
Rank: not rated yet
http://www.space....day.html
Oct 21, 2011
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