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Gravity Tractor Could Deflect Asteroids

ScuttleMonkey posted about 6 years ago | from the massive-undertakings dept.

NASA 372

Hugh Pickens writes "A new study at the Jet Propulsion Labs shows that weak gravitational pull of a "gravity tractor" could deflect an Earth-threatening asteroid if it was deployed when the asteroid was at least one orbit away from potential impact with Earth. First a spacecraft would be crashed directly into the asteroid, similar to the Deep Impact mission that impacted a comet in 2005. This would provide a big change of direction, but in a less controllable fashion that could push the path of the asteroid into a dangerous keyhole. But then a second spacecraft, the gravity tractor, would come into play, hovering about 150 meters away from the asteroid, to exert a gentle gravitational force, changing the asteroid's velocity by only 0.22 microns per second each day. Over a long enough time, that could steer it away from the keyhole. In the simulation, a simple control system kept the spacecraft in position, and a transponder on the asteroid helped monitor its position and thus determine its trajectory more precisely than would be possible otherwise. 'The gravity tractor is a wimp, but it's a precise wimp,' said astronaut Jack Schweickart. 'It can make very small, precise changes in orbit, and that's what you need to avoid a keyhole.'"

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Gravity Tractor = Anna Nicole ? (-1, Troll)

karvind (833059) | about 6 years ago | (#24468843)

Or 1/3rd US population ?

Re:Gravity Tractor = Anna Nicole ? (1)

negRo_slim (636783) | about 6 years ago | (#24468887)

Or 1/3rd US population ?

Yes take 1/3rd of the US population and put them on early warning duties. It sounds as this has some pretty hefty notification requirements to be an effective scheme.

I hrad that .... (0)

Anonymous Coward | about 6 years ago | (#24468847)

John Deere got the contract beating out Cat.

If I buy a gravity tractor... (4, Funny)

faloi (738831) | about 6 years ago | (#24468855)

Do I get a nifty green hat to wear while I'm on it?

Re:If I buy a gravity tractor... (2, Funny)

flyingsquid (813711) | about 6 years ago | (#24468919)

If it's a John Deere brand gravity tractor, yes you do!

If they ever do this... (2, Insightful)

DoofusOfDeath (636671) | about 6 years ago | (#24468881)

I hope their simulations use doubles, not floats!

Re:If they ever do this... (2, Insightful)

Z_A_Commando (991404) | about 6 years ago | (#24469007)

Actually, I would rather they use a consistent measurement for distance at all times. No more use of meters and feet in the same device!

Re:If they ever do this... (5, Funny)

gplus (985592) | about 6 years ago | (#24469251)

I agree. They should use furlongs and fathoms.

Re:If they ever do this... (4, Funny)

Tophe (853490) | about 6 years ago | (#24469859)

or Smoots [wikipedia.org] :D

Re:If they ever do this... (4, Informative)

4D6963 (933028) | about 6 years ago | (#24469113)

I hope their simulations use doubles, not floats!

I know you're joking but for just the speed values if they used time increments in the order of the second then the speed differences would be in the order of e-18, which is too small for a double's mantissa. I'd rather go with long doubles, or better (I think you can achieve something like that by using a number to store the closest representable value and another one to represent the tiny difference from what it should be).

Re:If they ever do this... (2, Interesting)

jandrese (485) | about 6 years ago | (#24469445)

Isn't the whole point of floating point that you store the exponent separately so you don't run into that problem (at least not as fast)?

Re:If they ever do this... (4, Insightful)

HairyCanary (688865) | about 6 years ago | (#24469495)

Why do they have to be limited to the precision of built-in data types? If dc can support unlimited precision calculations, the JPL can probably figure out too.

Re:If they ever do this... (0)

Anonymous Coward | about 6 years ago | (#24469739)

Are you talking about 64 double precision defined in IEEE 754?

If you are, then your 11-bit mantissa will be +/- 308 (or 1022 base 2). But even a float (32 bit single precision) should have no problem with a 8 bit mantissa giving a maximum mantissa of +/- 38 (base 10).

How about we move this rock instead? (2, Interesting)

Anonymous Coward | about 6 years ago | (#24468889)

In a sense, you could apply the same approach, except try to modify earth's orbit, which might actually be easier...

Re:How about we move this rock instead? (4, Insightful)

4D6963 (933028) | about 6 years ago | (#24469183)

In a sense, you could apply the same approach, except try to modify earth's orbit, which might actually be easier...

You realise of course that the Earth is pretty much a trillion times heavier than a mankind-threatening asteroid, right? And what would you want to modify Earth's orbit for anyways?

Re:How about we move this rock instead? (1)

x1n933k (966581) | about 6 years ago | (#24469637)

I'd like to modify it to get a little closer to the sun. I'm tired of these cold Quebec winters.

[J]

Re:How about we move this rock instead? (1)

Drakin020 (980931) | about 6 years ago | (#24469191)

For starters, why would you want to change the earth's orbit?

On top of that, if you change the earth's orbit then you change the impact risks of other asteroids.

Perhaps if things started getting a tad hot, you could always push the earth a tad away from the sun to cool things off, and likewise when things get a bit cold, but again I'd think that modifying the earth's orbit might not be the best idea.

Re:How about we move this rock instead? (1)

sm62704 (957197) | about 6 years ago | (#24469379)

In Larry Niven's A World Out of Time [wikipedia.org] they do indeed move the Earth out to Jupiter's orbit, making it a satellite of that planet.

It would be a lot easier to move a mountain than an entire world, and moving a world would undoubtedly lead to ecological destruction.

Harder... (0)

Anonymous Coward | about 6 years ago | (#24468899)

Harder...harder...too hard!

Armageddon 2 (5, Funny)

FlyingSquidStudios (1031284) | about 6 years ago | (#24468905)

Bruce Willis hovers over an asteroid for two action-packed hours!

Re:Armageddon 2 (0)

DeadManCoding (961283) | about 6 years ago | (#24468993)

Bruce Willis can't be in the second one, he died in a nuclear blast in the first one! Besides, you'll upset Liv Tyler you insensitive clod!

Re:Armageddon 2 (4, Funny)

FlyingSquidStudios (1031284) | about 6 years ago | (#24469211)

You THINK he died, but he actually hid in a refrigerator. He got the tip from his friend Harrison Ford.

Re:Armageddon 2 (1)

Aphoxema (1088507) | about 6 years ago | (#24469235)

He didn't get destroyed, he got mutated and is now Super Gravity Willis.

Re:Armageddon 2 (1)

MooseMuffin (799896) | about 6 years ago | (#24469429)

On the bright side, the GP has never seen armageddon. So while you may have corrected him, I think he's winning overall.

Man.. (1)

drewsup (990717) | about 6 years ago | (#24468927)

Can you imagine how much the tires go for on a gravity tracter? Those things have gotta be be Ginormous!

Preliminary testing. (5, Funny)

kwabbles (259554) | about 6 years ago | (#24468977)

Will be done by holding monthly Gravity Tractor Pulls at the local fairgrounds, with free beer.

Re:Preliminary testing. (4, Funny)

pauljlucas (529435) | about 6 years ago | (#24469201)

Will be done by holding monthly Gravity Tractor Pulls at the local fairgrounds, with free beer.

But it'll take a while until all testing is completed because they'd only do testing on Sunday, Sunday, Sunday!

Units units units (0)

Anonymous Coward | about 6 years ago | (#24468997)

0.22 microns per second per day?

What kind of lame units are those?

How about 2.5 x 10-12 m/s^2

Re:Units units units (0)

Anonymous Coward | about 6 years ago | (#24469749)

How about (the average Slashdotter waist size) / (the time it takes for somebody to bring up "40 rods to the hogshead")^2? Those are units that everybody can understand.

WMDs found (-1, Troll)

Anonymous Coward | about 6 years ago | (#24469065)

Considering how hard it is to steer it out of the 'keyhole', how hard is it to steer it into the 'keyhole'.

Armageddon 2:
Bruce Willis has a 'training' montage that is him eating lots of food to improve the amount of gravity he has, then hovering near the asteroid while the skinny under-fed terrorist fights to keep it on target.
Moral of the story: eat more or the terrorists win. brought to you by the ag-business and heart doctors.
Geeks will point out that they could just add metal to the ship to add weight for the extra gravity.

Sounds overly complex (1)

sunking2 (521698) | about 6 years ago | (#24469085)

If the first spacecraft moves it significantly why not just keep throwing those at it. If you are planning on moving this thing by the micron then the first can't be all that innacurate because you'd never be able to nudge out any drastic error. Just keep throwing the firt at it until we're OK.

Re:Sounds overly complex (2)

oyenstikker (536040) | about 6 years ago | (#24469249)

Wouldn't it be easier (and more effective) to have something land on it once, latch on, and fire rocket boosters to move it rather than to drive next to it for a long time?

Re:Sounds overly complex (2, Interesting)

zippthorne (748122) | about 6 years ago | (#24469551)

You are presuming that landing is possible. The object in question might be a loosly-conglomerated gravitationally bound pile of rocks and dust.

Re:Sounds overly complex (2, Informative)

Chyeld (713439) | about 6 years ago | (#24469643)

Even if the asteroid is solid, and there is some 'miracle' way of anchoring the rocket to the asteroid: Landing and pushing requires the assumption that the center of gravity and the shape of the asteroid is such that you can position the rocket push in a productive manner and not just cause the rock to pinwheel or split in two.

Re:Sounds overly complex (2, Interesting)

zippthorne (748122) | about 6 years ago | (#24469885)

True, however in the case of a gravity tug, your maximum useful thrust is limited by the gravitational interaction, which is limited by how close you can get. Landing takes one of the variables away, and trades it for the ones you mentioned. If it's solid, your maximum effective thrust can be very high, even if you can only use it a shorter percent of the time.

In specific cases, landers probably would be more effective. But gravity tugs are a much better general solution, and mass-production favors general solutions.

Re:Sounds overly complex (1)

ag3ntugly (636404) | about 6 years ago | (#24469583)

Or, have a craft land, and use an ion thruster, which would require much less fuel than a rocket, but would be enough to push it off course if you had time.

Re:Sounds overly complex (0)

Anonymous Coward | about 6 years ago | (#24469657)

Arthur C. Clarke's book, "The Hammer of God," deals with this very concept. It's fiction, of course, but with a large enough rocket, it could work. As in the book, rotation of the asteroid could prevent the rocket from firing when it has come off axis or turns from the intended vector -- to that end, I suppose the "formation flight" operation proposed in the OP eliminates this problem.

Re:Sounds overly complex (1)

Chyeld (713439) | about 6 years ago | (#24469559)

Because it'd be highly unlikely that the asteroid is a perfect sphere. And since it's likely to be some weirdly shaped object with a wildly offset center of gravity, thowing things at it isn't a particularly effective means of control. Especially if you only have a limited number of things to throw at it.

At best, you hit it spot on and it moves the direction you want.

More than likely, you hit it off center and instead of budging it you've just caused it to pinwheel. Which has the added effect of causing it to act like a gyroscope and resist further alterations to it's vector. The more things you throw at it, the more likely the second option occurs rather than the first.

A gravity tractor on the other hand, works regardless of the shape of the asteroid.

Re:Sounds overly complex (1)

Convector (897502) | about 6 years ago | (#24469655)

Or throw something even bigger at it. Like say, the entire Earth. That thing's huge. That would definitely knock the asteroid off course.

and now ... (1)

nategoose (1004564) | about 6 years ago | (#24469091)

Que the space rednecks.

Re:and now ... (2, Funny)

Anonymous Coward | about 6 years ago | (#24469317)

After they've lined up, what then?

Re:and now ... (1)

sm62704 (957197) | about 6 years ago | (#24469439)

"'m a space cowboy, bet you weren't ready for that! I'm a space cowboy, you know, you know where it's at, yeah yeah yeah yeah." -Steve Miller

Re:and now ... (1)

lilomar (1072448) | about 6 years ago | (#24469779)

"Some people call me a space cowboy. Some call me the gangster of love. Some people call me Maurice. Cause I speak of the properties of love." - Also Steve Miller

Keyhole - Is that a standard term? (2, Interesting)

fotoguzzi (230256) | about 6 years ago | (#24469109)

Could someone with the proper knowledge submit a Wikipedia article for keyhole? The word is used in the summary three times and seven times in tfa. I guess the term is here to stay.

Thank you.

Darn (2, Funny)

corychristison (951993) | about 6 years ago | (#24469119)

... and I thought it would be more like this [wikia.com] .

Coaxing vs Pushing (3, Insightful)

flaming error (1041742) | about 6 years ago | (#24469153)

How is gently pulling the asteroid with a weak gravity string more efficient than just landing the same "tractor" on the asteroid and pushing it gently but directly?

Re:Coaxing vs Pushing (4, Insightful)

Dr. Eggman (932300) | about 6 years ago | (#24469239)

maintaining an object near the asteroid would require less energy than actively pushing it away. Not to mention the possibility of asteroids that aren't solid enough to support something on its surface pushing it.

Re:Coaxing vs Pushing (3, Interesting)

MyLongNickName (822545) | about 6 years ago | (#24469485)

expending all of the energy carried by the probe

You have to obey the laws of physics. There is no way you will expend less energy holding your position than using all of your fuel to build up speed and crash into the sucker.

In fact, if there is any elasticity in the collision, it it far more efficient to crash. And this does not take into account the fuel you will waste simply by having to angle your exhaust to not hit the asteroid.

Now, the down sides to crashing are that you cannot accurately know just how much you will move the meteorite. You cannot make midcourse adjustments as you learn more about its trajectory, and as you mention, not all asteroids will be landable. Soft surface or rocky surace, and you will have wasted the lander.

Re:Coaxing vs Pushing (1)

Cornflake917 (515940) | about 6 years ago | (#24469767)

You have to obey the laws of physics. There is no way you will expend less energy holding your position than using all of your fuel to build up speed and crash into the sucker.

I think the GP means that it takes less energy to maintain position above an asteroid then to attach it to an asteroid and then have some sort of propulsion system push it off it's original course.

Re:Coaxing vs Pushing (1)

Facegarden (967477) | about 6 years ago | (#24469597)

I'm not sure that's true.... It seems to me that if the two objects are just hangin out in space, any force exerted, gravitational or otherwise, would require energy from the tractor craft to maintain. If there is a constant pull between the tractor and the asteroid, that should take just as much energy to maintain as pulling it with a cable would (or pushing it, which isn't as good for the analogy, but more realistic).

Remember, for every action there is an equal and opposite reaction, even if it's something spooky like gravity.
-Taylor

Re:Coaxing vs Pushing (3, Interesting)

Zocalo (252965) | about 6 years ago | (#24469339)

The tractor possesses mass, and therefore has a constant gravitational effect upon the asteroid (and visa versa) and the only fuel it needs to expend are the minuscule amounts necessary to keep it tracking the asteroid. The simulation shows that, given enough time, the cumulative effect of the gravitational tug can exceed that of expending all of the energy carried by the probe, whether kinetic (impact) or potential (engine burn). It's kind of like an ion engine; it's slower at first but over time it's going to leave a traditional chemical based rocket eating its space dust.

Re:Coaxing vs Pushing (2, Insightful)

MyLongNickName (822545) | about 6 years ago | (#24469649)

The simulation shows that, given enough time, the cumulative effect of the gravitational tug can exceed that of expending all of the energy carried by the probe,

So, basically, you are somehow getting more energy out of the system than you put in. This is basically the definition of a perpetual motion machine.

Ion engines give better long-term acceleration than chemical engines because they can spit the exhaust out faster, not because there is some magical reason that slow acceleration is more efficient than fast acceleration.

Ramming the ship into the asteroid is more efficient, but has the problem of potentially busting up chunks of the asteroid, imprecise measurements, and the inability to monitor and make adjustments as the asteroid is moved.

Re:Coaxing vs Pushing (2, Insightful)

caywen (942955) | about 6 years ago | (#24469899)

Doesn't the tractor have to expend energy to maintain a fixed distance from the asteroid? Also, wouldn't the tractor gain more benefit from maintaining as small a distance from the asteroid as possible to maximize its gravitation effect? In that case, the amount of energy it would have to expend would be proportional to inverse distance squared to maintain that distance, right? Is that really less energy than landing on the thing and using one of those ion propulsion engines? Or, perhaps the benefit is in the logistics. Perhaps landing safely on the thing is much harder than maintaining a fixed distance. If that's the case, I would get it. Sorry, I didn't do any real math, this is just a from the hip question.

Re:Coaxing vs Pushing (0)

Anonymous Coward | about 6 years ago | (#24469343)

On top of that the asteroid can spin and if you want to push it in just one direction you have narrow windows.

Re:Coaxing vs Pushing (0)

Anonymous Coward | about 6 years ago | (#24469459)

I would say its easier to make adjustments if you're not on the surface pushing directly. Simply change the position you're holding over the asteroid and change the direction of pull.

Also if you land and push directly you'd have to push directly through the CG or you're going to start to spin the thing. The gravity tractor on the other hand always pulls on the CG.

Re:Coaxing vs Pushing (0)

Anonymous Coward | about 6 years ago | (#24469587)

It's much easier to pull than push when you need it to go in a certain direction. Note that when pulling by gravity, it doesn't matter which way the asteroid is pointing.

If you were to try to push the asteroid while attached to it, you'd much more likely just spin the thing.

Re:Coaxing vs Pushing (1)

LSD-OBS (183415) | about 6 years ago | (#24469667)

Thank you for saving me the time of having to remind people of Newton's Second. I'm fairly amazed that this isn't by now completely obvious to people.

Re:Coaxing vs Pushing (1)

LSD-OBS (183415) | about 6 years ago | (#24469685)

Whoops, retract that, I had this figured out last week at the pub -- it's because of the objects's spin that you need to use a gravitational tether. Damn you, alcohol-impaired hippocampus!

Re:Coaxing vs Pushing (1)

CastrTroy (595695) | about 6 years ago | (#24469683)

I imagine it's much easier to stay a certain distance from the asteroid and maintain altitude then to land on the asteroid and risk crashing, or something getting damaged in the process. If you stay above the asteroid, you don't have to worry about finding a suitable landing location.

Re:Coaxing vs Pushing (1)

Ummite (195748) | about 6 years ago | (#24469715)

I was exactly asking myself a similar question. My main concern was if the tractor has a gravitational impact on the asteroid, the same apply for the asteroid to the tractor, and they should collide. So the tractor has to repulse itself from the asteroid. Probably if the tractor is far enough from the asteroid, any propulsor would eject matter behind the asteroid, so the force used to keep away from the asteroid would not repulse back the asteroid on the path it should not go. But, why this energy is lower than the energy that could be used if the tractor is landed on the opposite side and "pushed" the asteroid away, I really don't know. Probably the fact that landing such tractor is a lot more risky than simply being on a parallel path.

Re:Coaxing vs Pushing (1)

Red Flayer (890720) | about 6 years ago | (#24469829)

Spin.

Most asteroids spin, and thus using a thruster will, in the long run, be negated by the spin of the asteroid. Unless the thrusters are timed to coincide with the spin, etc -- and that's assuming there are no problems with landing (well, attaching, really) to the asteroid.

Using gravity would, almost definitely, be more precise than trying to use thrusters -- and so we could avoid the possibility of massive failure (by, say, kicking the asteroid into a different keyhole, or by causing the asteroid to break apart).

nukes (0)

Anonymous Coward | about 6 years ago | (#24469155)

and what do we do when they mess up the calculations and we turn a near miss into an impact.

For a backup plan please use nukes.

Re:nukes (1)

eclectro (227083) | about 6 years ago | (#24469309)

I agree. As a backup plan, we need to be ready to ram a nuke in the keyhole.

Re:nukes (1)

1729 (581437) | about 6 years ago | (#24469361)

Nukes are better suited for the primary plan:

https://e-reports-ext.llnl.gov/pdf/343984.pdf [llnl.gov]

However, simply blowing up the asteroid at the last minute (Armageddon-style) won't help much.

Re:nukes (1)

halsver (885120) | about 6 years ago | (#24469897)

Would one or more nuclear explosions affect the orbit of a dinosaur-killer very much? Steering by explosion if you will.

that's what you need to avoid a keyhole (0)

Anonymous Coward | about 6 years ago | (#24469171)

or to hit one.

Um, dumb question time (3, Insightful)

smooth wombat (796938) | about 6 years ago | (#24469199)

If all they're trying to do is move the orbit of the asteroid by a fraction or a millimeter per second, wouldn't it be easier to just, you know, harpoon the asteroid and use ion engines to gently pull on it rather than trying to keep a second spacecraft hovering over the non-smoking crater of the first spacecraft? Or, if harpooning isn't viable (cue 'Whalers on the Moon'), just have the spacecraft rest on the asteroid's surface and, using ion engines again, push on the thing.

Can someone more well versed in orbital mechanics and the motion of bodies in space please provide some information as to why these are not viable options.

Re:Um, dumb question time (5, Insightful)

Colonel Korn (1258968) | about 6 years ago | (#24469389)

If all they're trying to do is move the orbit of the asteroid by a fraction or a millimeter per second, wouldn't it be easier to just, you know, harpoon the asteroid and use ion engines to gently pull on it rather than trying to keep a second spacecraft hovering over the non-smoking crater of the first spacecraft? Or, if harpooning isn't viable (cue 'Whalers on the Moon'), just have the spacecraft rest on the asteroid's surface and, using ion engines again, push on the thing.

Can someone more well versed in orbital mechanics and the motion of bodies in space please provide some information as to why these are not viable options.

Orbital mechanics aren't the problem with your suggestion. Consider getting a craft to gently land on an asteroid. That's probably equivalent in difficulty to having a craft maintain its position 150 meters from the asteroid, as suggested in TFA. Already the lander has had about as much complexity as the "hoverer."

Now consider that the object must pull or push the asteroid along a very specific and consistent trajectory to safely move it out of danger. Remember that the asteroid is certainly spinning about two axes, so an object stuck to the surface would not be able to simply face in one direction and push. The craft hanging out 150 meters from the asteroid ignores the spinning and does its job, while the craft on the surface of the asteroid has to either push really hard every once in awhile, when its trajectory happens to be lined up well, or it has to constantly push and angle its exhaust while continuously calculating the correct direction to maneuver the spinning object correctly. Or it could cease the asteroid's rotation, which itself is a difficult problem.

Re:Um, dumb question time (0)

Anonymous Coward | about 6 years ago | (#24469515)

I agree with you, however they better make sure the surface of the asteroid relative to the asteroid doesn't vary by more than a couple hundred meters - it would suck to have a "mountain" on that asteroid swat the hoverer as the mountain swung by.

Re:Um, dumb question time (3, Insightful)

the_other_chewey (1119125) | about 6 years ago | (#24469421)

Or, if harpooning isn't viable (cue 'Whalers on the Moon'), just have the spacecraft rest on the asteroid's surface and, using ion engines again, push on the thing.

One word: Rotation.

If you put an engine on the asteroid, you cannot use it about half of the time (very roughly, probably way less)
because it would be pushing in the wrong direction.
Hovering decouples your applied force from the rotational movements of the asteroid, so as long as you manage
to hold your position on the right side of the asteroid, the force is applied constantly.

So a gravity tractor can apply the same delta-v faster than a "ground based" solution.

Re:Um, dumb question time (2, Funny)

verbamour (1308787) | about 6 years ago | (#24469527)

It's not orbital mechanics, but asteroid mechanics that come into play. An asteroid may be a loose gravel pile, so an engine placed on the surface may dig in, or even push all the way through. Gravity traction is a very low-stress way to impart momentum.

I'm not a rocket scientist, but my hot girlfriend's little sister is...

Keyhole? (1)

Sockatume (732728) | about 6 years ago | (#24469247)

I'm glad I already read this story and understand the metaphor, because the summary is rather unintentionally surreal otherwise.

Re:Keyhole? (1)

pilgrim23 (716938) | about 6 years ago | (#24469479)

Keyhole was the code name of the KH series of spy satellites.

As to the concept itself: what of the Enviornmental Impact statement (if it hits)? What of its carbon footprint (If it hits)?

Also, as I recall, the last body that could have posed an issue was discovered on its way AWAY from Earth after its close encounter. There are so many of these in orbits never before tracked that our first clue of a problem may be after a rock lands where India used to be...

How does this scale? (0)

Anonymous Coward | about 6 years ago | (#24469259)

As I understand it, they used a hypothetical asteroid measuring ~140 meters in diameter. The Apophis asteroid measures ~1000 ft in diameter. As I understand it the mass scales as well so, outside of launching something exponentially heavier, how does this solution scale?

Not that I don't believe in NASA, I am actually applying for a job at JPL this fall.

Confirmation? (1)

Wiarumas (919682) | about 6 years ago | (#24469261)

From TFA: "...it would exert a gentle gravitational force, changing the asteroid's velocity by only 0.22 microns per second each day. But over a long enough time, that could steer it away from the keyhole..."

So... would there be confirmation that this plan is working when attempting it? Honestly, with a miniscule (and possibly undetectable) amount of 0.22 microns and such a large amount at stake (olbiteration), I would want to know if Plan A is working and if Plan B should start.

How to not get splattered (2, Interesting)

Jhan (542783) | about 6 years ago | (#24469263)

TFA spells it out very nicely. Get there one orbit early (a year or a little longer) then gently tug. Of course that's for a small asteroid, for a dinosaur killer maybe five years. If you wait until the object is a few weeks away you are toast. Cindered toast. The entire "nuclear might" of the planet launched at the intruder will do diddley squat, Bruce Willis or no Bruce Willis. That's why NEAR should get lots more funding.

Obligatory Hitchhiker's Guide to the Galaxy quote (2, Funny)

Yvan256 (722131) | about 6 years ago | (#24469491)

Barman: Do you really think the world's about to end?
Ford: Yes, in just over 3 minutes and 5 seconds.
Barman: Well, isn't there anything we can do?
Ford: No. Nothing.
Barman: I thought we were supposed to lie down, put a paper bag over our head or something...?
Ford: Yes, if you like.
Barman: Will that help?
Ford: No. Excuse me, I've got to go.
Barman: Ah, well. Last orders please!

OT: Orbit@Home is now NASA-funded (5, Interesting)

Burz (138833) | about 6 years ago | (#24469269)

Its probably a good time to remind people that the distributed computing project to search for dangerous NEOs [psi.edu] is soon to get under way. Test workunits have already been sent out and the news is that they ran very well.

pint sized (1)

rubycodez (864176) | about 6 years ago | (#24469295)

That's a very small asteroid they're modeling, wake me up when they can do something about the mile-wide ones

a few megatons TNT of impact energy won't do much on most of the earth's surface, likely hit nothing important

I hate to accuse JPL of forgetting something... (0)

Jane Q. Public (1010737) | about 6 years ago | (#24469305)

but apparently they did.

In order for the "gravitational tractor" (GT) to keep pulling the object out of its current path, the GT would have to be ejecting reaction mass toward the object it was supposed to be pulling... thus pushing it away. Unless it was MUCH larger than the object it is supposed to be pulling, in which case it could eject mass to either side. Which seems unlikely.

Perhaps there is some small angle it can thrust at that does not impact the object while still pulling it away... but that seems like an even more unlikely balancing act.

Re:I hate to accuse JPL of forgetting something... (4, Informative)

trongey (21550) | about 6 years ago | (#24469701)

Who modded the parent "insightful". The answer is pretty simple, and is even illustrated in the article. The picture shows a craft with three thrusters all angled away from the asteroid. The resulting thrust is a vector normal to the target. Sure, it sacrifices efficiency, but it works.

Exhaust is not a pencil beam. (1)

zippthorne (748122) | about 6 years ago | (#24469773)

And depending on the distance (though further away poses problems for the gravity-part) the object can subtend a small portion of the exhaust "pattern."

Further, directly above is not the only option. Halo orbits of a single body require constant thrust to maintain, which is actually quite ideal for the situation at hand: allowing the gravity tug to get closer to the center of mass (cos(phi)/r^2 is better than 1/r^2 when you can have a smaller r) and keep the body out of the way of the preferred thrust direction.

Re:I hate to accuse JPL of forgetting something... (0)

Anonymous Coward | about 6 years ago | (#24469781)

Two propulsion engines at an angle of say 15 degrees, each pointing 7.5 degrees away from the asteroid. You do lose some fuel efficiency that way, but at least this problem does not occur.

As simple as that.

And landing or harpooning is usually not an option, because asteroids tend to:
1) rotate
2) break apart during transit through our solar system (especially if they pass by close to the outer planets)

Re:I hate to accuse JPL of forgetting something... (1)

ag3ntugly (636404) | about 6 years ago | (#24469831)

If it has several small thrusters, each pointing out not directly at the object, but say at 45 degree angles to the object in a conical sort of fashion, each applying the same force, with the tractor at the point and the object inside the cone, the forces applied by the thrusters (my physics teacher would be proud that i remembered all this business about vectors) will add up to an overall force on the tractor directly away from the object, while not applying an opposing force on the object.

Re:I hate to accuse JPL of forgetting something... (1)

Wavebreak (1256876) | about 6 years ago | (#24469837)

The scenario you're describing is so mind-numbingly trivial to avoid that even I could do the math involved.

You stand at the bridge of space travel... (1)

CFBMoo1 (157453) | about 6 years ago | (#24469341)

What is your name?

Joe Q. Scientist.

What is your mission?

To capture an asteroid.

What units of measure were used in the mission?

English... no metric!

*KABOOM!*

Bah. Just Nuke It. (1)

aquatone282 (905179) | about 6 years ago | (#24469375)

I wanna watch from my front yard at night while drinking cold beer with my neighbors.

Re:Bah. Just Nuke It. (0)

Anonymous Coward | about 6 years ago | (#24469607)

Ah Nukes, the redneck answer to all questions regarding earth crossing asteroids AND rouge terrorists/nation states.

Bad idea (1)

Yvan256 (722131) | about 6 years ago | (#24469425)

Next thing you know, bugs from Klendathu will throw rocks at us too.

Tell me more! (1)

Technopaladin (858154) | about 6 years ago | (#24469819)

hated the movie
But the book was good. I am a 15 second bomb, I am 14 second Bomb...

Screw the asteroids tracking systems (3, Funny)

Yvan256 (722131) | about 6 years ago | (#24469521)

We should be watching to see if the dolphins leave the Earth by their own means.

I've got another way (1)

Sodki (621717) | about 6 years ago | (#24469523)

It can make very small, precise changes in orbit, and that's what you need to avoid a keyhole. Actually, to avoid a keyhole, you just have to get drunk.

Sounds like... (1)

acedotcom (998378) | about 6 years ago | (#24469535)

Armageddon 2: Space Farmers

Hypothetical Question (1)

arizwebfoot (1228544) | about 6 years ago | (#24469599)

So . . . the tractor pulls the asteroid into a new orbit, causing it to slam into another asteroid of equal size, causing them to to split into eight equally large pieces for whose trajectory is now altered to collide with the earth.

Time to buy a lot of shares at the Tractor Supply Store.

Opportunity to Weaponize (2, Insightful)

garnkelflax (1306647) | about 6 years ago | (#24469611)

If it can be guided away from the keyhole, could it not also be guided towards? I think this presents a wonderful opportunity for extortion. If I only had the resources I would shave my head, get a cool chair, and become adept at holding my pinky to the corner of my mouth in an evil fashion.

Microns... (1)

tjstork (137384) | about 6 years ago | (#24469731)

A micron is a unit of length, not velocity. Do they mean microns per second?

Nice, but lets keep it real. (4, Insightful)

Lord Apathy (584315) | about 6 years ago | (#24469833)

Gravity Tractor? You know I love these sky high fantasy ideas to deflect asteroids as much as anyone else but shouldn't we be concentrating on what is real? If an asteroid does threaten Earth in the next few years we will use nuclear demolitions on it. We will not use a gravity tractor, laser beams, or giant snow balls. Nor will we attach plasma engines or mass drivers to it. We will use nuclear demolitions because that is, simply, all we have.

We will not send a robot to do it nor will we send some type of futuristic space ship driven by plasma/ion engines. It will be a manned ship with old style chemical rockets right out of the '60. Why? Because we have over 60 years experience with them and they will get the job done. We'll send men and not a robot because the mission is to important to have place in the hands on questionable technology. A robot breaks down and the mission is over. With men at least you have some hope they can fix it. Yes, it will probably be one way but the pilots will know that. They will go anyway.

Yes, we will break it up in to smaller pieces because that is best. Don't give me that shotgun crap about it scattering the damage over a wider area. We will think of that and cover it. If we let a huge honking rock ride in the atmosphere will not even slow it down. It will punch through it like it isn't even there. Worse is it will punch through the crust to the mantel causing shockwaves all around the planet.

We wont' use one nuke. We will blowup the big one then we will blow up the smaller ones into smaller pieces. We will do this until the chunks are small enough that the atmosphere will handle. With smaller chunks there is more surface area for the atmosphere to work on. Most importantly the smaller chunks will not "crack the crust" as one fat ass one would.

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