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Space China Earth

Chinese Researchers Propose Asteroid Deflection Mission 198

Posted by Soulskill
from the bruce-willis-need-not-apply dept.
wisebabo writes "Researchers in China have proposed sending a solar sail-driven probe to hit the asteroid Apophis to make sure it has no chance of going through a 'keyhole' near earth in 2029. If it goes through the keyhole, then it will hit the earth seven years later. The reason why they need to use a solar sail is because they want the very small probe (~10kg) to hit the asteroid in the opposite direction, a retrograde orbit which would otherwise require an insane amount of fuel (after being put on an escape trajectory, it would need to first cancel out the earth's orbital momentum and then basically speed up to a likewise high velocity in the opposite direction). They are doing this to hit the asteroid at a very high impact speed. While Apophis may not literally be capable of wiping us out (it 'only' weighs 46 million kilograms), it might be able to wreck our civilization." Read on for the rest of wisebabo's thoughts.
wisebabo continues, "Rather than putting the fate of our species into the hands of an untried technology (no solar sail has yet imparted substantial delta-V to its spacecraft) may I suggest an alternative? By using Jupiter as a gravity assist, we could send a much heavier probe to hit it at comparable speeds. For example, the Juno spacecraft, recently launched to the gas giant weighs almost 8000kgs. Jupiter could sling a spacecraft around so as to completely cancel its orbital momentum (with no fuel expenditure!). Then it will fall directly towards the sun and, if guided correctly, could hit Apophis broadside. Considering it will be falling from a height of several hundred million miles, it would pack quite a wallop. Admittedly, the impact will be on the side rather than head-on, but that should be okay since all we have to do is assure that Apophis doesn't pass through the keyhole, which is only 600m wide. Don't get me wrong, I hope solar sails become widely used for the (slow, cheap) transport of cargoes in the solar system. It's just that I wouldn't base the defense of earth on them."
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Chinese Researchers Propose Asteroid Deflection Mission

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  • Mass != weight (Score:3, Insightful)

    by ABoerma (941672) on Friday August 19, 2011 @10:50AM (#37142558)

    > (it 'only' weighs 46 million kilograms)

    No it doesnâ(TM)t. Kilograms are a unit of mass, not of weight.

    • by Anonymous Coward

      > (it 'only' weighs 46 million kilograms)

      No it doesn't. Kilograms are a unit of mass, not of weight.

      Yes, this also made me very amused:

      Considering it will be falling from a height of several hundred million miles ...

      • by smelch (1988698) on Friday August 19, 2011 @11:00AM (#37142672)
        Does falling only apply to movement toward the Earth now? Can you not fall on the moon? Can the earth not fall toward the sun? Can a probe not fall toward the sun and hit an asteroid?

        Can you not say that however high something is is its distance along the normal of the object you are measuring relative to?

        It may have amused you, but I think it's correct usage for both words.
        • by melikamp (631205)
          Also, Falling is the opposite of Springing.
    • by Trepidity (597)

      Sure, but in informal writing by earthlings, kg as a unit of weight pretty clearly is taken to mean "the weight that a 1 kg object would have at sea-level earth gravity".

      • Sure, but in informal writing by earthlings, kg as a unit of weight pretty clearly is taken to mean "the weight that a 1 kg object would have at sea-level earth gravity"

        Maybe they calculated the actual weight the object will have in 2036, when it'll be at sea level..

        • by Zalbik (308903)

          Maybe they calculated the actual weight the object will have in 2036, when it'll be at sea level.

          What? And you're saying this number is coincidentally exactly the same as it's mass?!?

          I think I'm gonna go hide under a rock in 2036.

          • by geekoid (135745)

            If you step on a scale at sea level, your weight will be 80Kg*. If you to then go into space, your mass would be... 80Kg.

            *for this example, natch.

  • Apophis (Score:5, Funny)

    by multipartmixed (163409) on Friday August 19, 2011 @10:50AM (#37142562) Homepage

    While Apophis may not literally be capable of wiping us out (it 'only' weighs 46 million kilograms), it might be able to wreck our civilization."

    Don't worry. Teal'c will take care of Apophis.

  • Pretzels (Score:5, Insightful)

    by Anonymous Coward on Friday August 19, 2011 @10:51AM (#37142564)

    Well I hear lots of organizations and governments have made plans to deflect an asteroid with a missile should one threaten to hit Earth. I think it wouldn't be a bad think to practice a little on asteroids that are passing close but not threatening us. I think we'd want to be ready for when a real danger shows up.

    • by gbjbaanb (229885)

      we could practice on it while its way out there. If we miss, we'd have many chances to try again.

      But of course, we'll just ignore it due to budgetary concerns until its a real danger and then it'll be too late to do anything other than send Bruce Willis - and he'll be far too old by then!

    • I think it wouldn't be a bad thing to practice a little on asteroids that are passing close but not threatening us.

      yeah and supposed they had a little "oops" in their practice run and deflected it the WRONG WAY?

      • by yotto (590067)

        Then we be glad we tested it on a little asteroid, kick back, and watch an awesome meteor shower?

        • the man said --

          I think it wouldn't be a bad thing to practice a little on asteroids that are passing close but not threatening us.

          Practice a little, not practice on little asteroids. That little oops is going to cause all seven billion of us to have a REAL BAD DAY (tm).

      • by dissy (172727)

        yeah and supposed they had a little "oops" in their practice run and deflected it the WRONG WAY?

        Then instead of being no where near earth, it will be slightly less no where near earth.

        For an asteroid already heading towards Jupiter or the Sun, there is nothing at all we could do to overcome the gravity pulling it to cause it to veer off towards Earth or anything.

        Practice makes perfect, and waiting until we need it to even make the first attempt is a recipe for failure.

  • by JanneM (7445)

    How out doing both? Even if one fails the other would succeed, and you'd test both technologies in a real-world setting. We're talking fairly cheap missions, relatively speaking, and they could almost be worth it just for the incidental research data if you let some of their mass be instruments and communications equipment.

    • Also, why not hit it with a big Big BIG nuke when it happens to be in the keyhole? Even a few cm/s delta-V would give great distance in 7 year's scale. Or am I wrong?
  • Pointless (Score:3, Informative)

    by agentgonzo (1026204) on Friday August 19, 2011 @10:52AM (#37142588)
    It's basically been confirmed that it's not going to hit the Earth: http://en.wikipedia.org/wiki/99942_Apophis#History_of_impact_estimates [wikipedia.org], http://en.wikipedia.org/wiki/File:Apophis_pass_zoom.svg [wikipedia.org], but then this is China we're talking about so they probably don't believe the rest of the world's measurements.
    • and china state tv will just show clips from movies or tv shows to show this off.

    • by omnichad (1198475)

      It's just a cover. They actually plan to redirect it TOWARD an earth-impact trajectory, unless we pay a hefty ransom. Say, one MILLION dollars?

      • Hopefully they still accept T-bonds

      • by AmiMoJo (196126)

        You are probably closer to the truth than you realise. It was no coincidence that shortly after China shot down a satellite with a ground launched missile the US decided to had to demonstrate the same thing on some random bit of space debris. If China can prove they have the ability to change the trajectory of an asteroid away from the earth then they can surely direct one towards it, basically an orbital bombardment mass driver.

        Space is looking like the new battleground where the US and China are going to

    • by Asic Eng (193332)
      Well, it still could have value as a proof of concept. Just in case we need it in the future.
  • http://en.wikipedia.org/wiki/99942_Apophis [wikipedia.org]

            2.7×10^10 kg

    How difficult is it to copy paste?

  • by Anonymous Coward

    "Apophis pushed through 'keyhole' in space by solar sail. Seven year countdown begins."

    • Frighteningly enough, I can see this happening. It would almost be better to plot the sail's trajectory to screw with its trajectory if it passes THROUGH the keyhole, and glide by harmlessly if Apophis MISSES the keyhole. By all means get the hardware into position to avert disaster... but if it looks like disaster isn't likely to happen, for the love of ${deity} don't go screwing with it and risk making things worse just for the sake of Doing Something.

      It's kind of like theoretical weather-control experime

      • by arth1 (260657)

        With risk calculations, you have to multiply the risk percentage with the damage factor.
        A 1% risk of 1 billion people dying is a much greater hazard than a 50% risk of 10 million people dying. If you had the chance to turn the former risk into the latter, you'd be a fool or a gambler (but, I repeat myself) not to take it.

  • Since we still don't even know that it will hit that keyhole (the last stat I saw was 1:250,000 chance), what are the chances that instead of a direct hit, we'll just make a glancing blow that ultimately nudges it through the keyhole?

    This mission seems to make more sense if there's a 100% chance it will hit the keyhole, because then there's no way to make it worse, but I'd like to see some statistics on the chances of making the situation worse (or on completely missing it and doing nothing at all)

    At the ve

    • by sqlrob (173498)

      They've already done the mission with another asteroid. Haven't you seen the broadcasts on the Chinese news?

    • by Nyeerrmm (940927) on Friday August 19, 2011 @12:18PM (#37143728)

      The problem is that the only way to be 100% sure (or even 10% sure) of an impact risk is to send something out there to track it with proper radio science measurements.

      Generally the approach any mission should take is not to prevent an impact, which implies that you will have something approaching good knowledge of whether or not it would pass through a keyhole, but rather to reduce the probability of impact. Because the center of the distribution from your knowledge (largely gaussian) is going to be offset from the keyhole, you need to nudge the asteroid further in that same direction to move it out past a 5-sigma or 6-sigma or 7-sigma ellipse, whatever your desired goal is.

      The annoying truth about dealing with anything in deep space is that its all probabilistic. You never really know where anything is, and you always have to quote your certainty values.

  • Chinese (Score:4, Interesting)

    by immakiku (777365) on Friday August 19, 2011 @11:01AM (#37142684)
    I think it's interesting that in most doomsday asteroid scenarios, the US is the one to launch a mission to save the earth. Granted, part of that is because Hollywood wrote those scenarios, but generally the rest of the world doesn't think twice when watching those movies because US is the de facto leader in most things. I think this is a telling inflection point in the history of nations.
    • Re:Chinese (Score:5, Insightful)

      by Nidi62 (1525137) on Friday August 19, 2011 @11:25AM (#37143010)
      It's probably because, at least until recently, the US would be the country that would be best able to absorb the brunt of the costs associated with a mission such as this. Also, US-affiliated technology would have to play some sort of role regardless. But really, should a scenario like this actually occur, I would expect that most countries would contribute in some way.
      • It seems like it would be a huge financial drain. Someone would be profiting, that's for sure.

    • ... in gravity assists (which as I pointed out in my submission) could make the mission much cheaper and less risky.

      Since they don't have any experience with gravity assists and (no-one) has any real experience with solar sails, I figure they just picked the one that sounded more sexy. If they actually had a long track record of deep space missions (they've only gotten to the moon whereas the U.S. is on its way to PLUTO), they wouldn't go this route. So I think the inflection point is still a ways off.

      • Since they don't have any experience with gravity assists and (no-one) has any real experience with solar sails, I figure they just picked the one that sounded more sexy.

        Indeed. Every time one of these 'fear the yellow peril' stories is posted, folks seem to forget that China (like Russia over the last twenty odd years) has a very long list of Sexy And Ambitious Plans they're going to accomplish Real Soon Now - and a very short (read:practically non existent) of thing's they've actually accomplished.

      • Pluto? Is that some sort of moon?
    • by metacell (523607)

      But China seems determined to take over that position.

    • by JanneM (7445)

      "[â¦.]but generally the rest of the world doesn't think twice when watching those movies[...]"

      Why do you assume that?

      I mean, unless you speak the language and participate in the local conversation you're not likely to pick up anything about how people react and what they think, right?

      • by immakiku (777365)
        Yea uh... I am Chinese. I watched those doomsday movies with my Chinese relatives. And I read about general sentiment regarding these movies online.
  • See? The end of the epoch *is* the end of life! Screw the Aztecs...

    • by Elbart (1233584)
      You might want to check the numbers again. 2029 + 7 = ?
      • by omnichad (1198475)

        It's one year early. Our mission to the moon started a 2^32 second timer, counting down to our demise - we were deemed a threat once we began manned space exploration to the moon.

      • by geekoid (135745)

        2030.... think about it...

  • by Ken_g6 (775014) on Friday August 19, 2011 @11:01AM (#37142694) Homepage

    I worry that an impact, rather than moving the entire asteroid, could shatter it and make it much more likely that one small (but still potentially dangerous) part would go through the keyhole.

    • by cbhacking (979169)

      I wouldn't even bother commenting except somebody modded this up, but... really?

      A) A solar sail space craft has negligible mass. Seriously, light pressure isn't very strong. If you want any decent acceleration you need a ludicrous area-to-mass ratio. Against an asteroid this size, there's not going to be much concentrated impact.

      B) Space is mostly empty, but there's a lot of little stuff floating around, and a large asteroid will have hit some of it before. They're not *that* fragile. I mean, it's literally

      • by Ken_g6 (775014)

        B) Space is mostly empty, but there's a lot of little stuff floating around, and a large asteroid will have hit some of it before. They're not *that* fragile. I mean, it's literally a big rock. Go find yourself a nice boulder and throw paper airplanes at it until it breaks - that's about the level of what's being proposed here.

        Not all asteroids are created equal. Sure, some are like boulders, but others are rubble piles [wikipedia.org], held together only by weak gravity. If a solid asteroid is like a boulder, imagine a rubble pile like a set of pool balls racked on a pool table. Sure, throwing a paper airplane at that isn't likely to send a ball flying off either, but it's far more likely than hitting a boulder.

        C) Even if some small piece does fly off, it's not necessarily a risk. Many, many tons of material hit the earth (or at least its atmosphere) every year. Most people call them "shooting stars".

        But those are tiny chips. An impact is far more likely to knock a chunk off a rubble pile than chip a ball or boulder.

        I'm not sayin

  • So they figured out that generalized multi-body problem, then, I guess? There are so many variables and errors in our best calculations that a mission like that is probably just as likely to doom us as it is to save us. We'd probably end up pushing it right into Los Angeles. (Wait, that could be a good thing...)
  • Right before they finish building this project...

    "Project cancelled."
    "Incan civilization completes wonder: Asteroid Defense Satellite"

    Or maybe it would be more appropriate for SMAC instead of Civ...

  • How about not concerning yourself with impacting it at high speed, but simply landing on it and then activating the solar sale? Twenty-nine years of drag from that would certainly deflect it from its orbit.

    If the solar sale provided enough delta-v to accelerate a ram, in less than a year, to a speed high enough to deflect the rock, it would necessarily be powerful enough to directly maneuver the rock.
  • by sidyan (110067) on Friday August 19, 2011 @12:04PM (#37143546)

    Juno's [wikipedia.org] mass is listed as 3625kg, or almost 8000 pounds, not almost 8 metric tons.

    As for the energy obtained from "falling several hundred million miles": that would be exactly the same energy it took to get that far "up" in the first place (not saying that there's no energy to steal from Jupiter, but it's a pretty hair-brained plan, imho, not in the least because such a trajectory would probably take the better part of a decade to complete).

    • I'm assuming you're right about the conversion error, I just plucked the 8000kg figure off the first web site that I got off Google (I'm the submitter). Still 8000 LBS. is a lot more than the Chinese probe's 10 kgs.

      As far as the energy calculations go, using a (large) gravitational body to change the velocity (speed AND direction) allows the transfer of momentum (energy) from Jupiter to and from the spacecraft. By causing the spacecraft to "lose" its forward momentum relative to the sun, Jupiter can rob i

  • by Ukab the Great (87152) on Friday August 19, 2011 @12:42PM (#37144082)

    We can't let mankind's job of destroying itself be outsourced to illegal alien asteroids that can be payed practically nothing.

  • is not familiar with the phrase 'First, do no harm".
  • Yes, all the stuff I get from China is so reliable that I'd trust it not to deflect the asteroid in the wrong direction, into Earth. China's military is so accountable to reasonable, compassionate authorities that they'd never risk hurting people just to demonstrate their strength and spread around some military/industrial money. After all, the Chinese space programme has so much experience doing hard things no others have ever tried, let alone accomplished. This project couldn't possibly be just a reckless

  • is that China can hold the rest of the world hostage once they are able to nudge the largest WMD ever either towards or away from the Earth. ;-b

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