Deflecting an Asteroid Will Be Harder Than Scientists Thought (upi.com) 180
schwit1 shares a report from UPI: According to new asteroid collision models designed by scientists at Johns Hopkins University, deflecting a large rock headed for Earth will be harder than previously thought. Using the most up-to-date findings on rock fracturing, researchers developed computer models to more accurately simulate asteroid collisions. For the newest study, scientists decided to divide the model into two phases. Phase one modeled the immediate fracturing that happens in the wake of a collision -- the processes that play in a matter of seconds. The second phase simulated the gravitational re-accumulation process that happens over the course of several hours or days.
The first phase of the updated model showed a large asteroid is not destroyed by a much smaller asteroid. Instead, millions of cracks form throughout, the core fractures and a crater is left behind. During phase two, the fractured core exerts a strong gravitational pull on the smaller pieces of debris and shrapnel broken during the impact. Because the asteroid did not crack completely during phase one, the space rock retained significant strength. If scientists are going to develop an asteroid deflection strategy that can actually work, they need to know how much force it really takes to destroy or deflect one. The latest study -- published in the newest issue of the journal Icarus -- showed it's more force than was originally thought.
The first phase of the updated model showed a large asteroid is not destroyed by a much smaller asteroid. Instead, millions of cracks form throughout, the core fractures and a crater is left behind. During phase two, the fractured core exerts a strong gravitational pull on the smaller pieces of debris and shrapnel broken during the impact. Because the asteroid did not crack completely during phase one, the space rock retained significant strength. If scientists are going to develop an asteroid deflection strategy that can actually work, they need to know how much force it really takes to destroy or deflect one. The latest study -- published in the newest issue of the journal Icarus -- showed it's more force than was originally thought.
Play the national anthem (Score:1)
Deflection (Score:3)
I always though the goal of the blast was not to destroy the asteroid but to change its trajectory...
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I always though the goal of the blast was not to destroy the asteroid but to change its trajectory...
Seriously? How are you going to destroy a solid rock? Now put that rock in a vacuum and tell me how you figure on coupling enough energy though nothing to do this?
It's a whole lot easier to deflect something so it misses, than break it apart into harmless pieces. The actual window for things to crash into Earth is pretty small.
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One can use a gravitational tug [wikipedia.org] to "couple enough energy through nothing". It's not a panacea, but it is one method that is largely unaffected by the asteroid's internal strength.
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Useless except for objects so far away you have years and years to spare for this to exert any sort of force. While in theory gravity is dependent on M1 and M2.... if one of the masses is so large (and if you're afraid of catastrophic asteroids, you ARE only dealing with large masses) compared to the other, the effect of the smaller one is negligible. It's like saying you're going to change the axis of the world by sending a shipload of rocks from the equator to the north pole. Yes, in theory. In practice,
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Yes, in theory. In practice, you'll never measure it.
If you would sail all ships on earth close to a pole the axis would shift significantly, easy to measure.
Even an amount as tiny as provided by an ion drive will have a much more measurable effect than gravity alone given enough time.
Erm, no? It is by conversation of momentum and conversation of energy: the exact same effect/work.
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Primary option is to land powered ion engines and let them work over time.
Otherwise, with the Big Bomb approach, you detonate an asteroid radius or a bit less away and use the generated x-rays to vaporize a layer of surface over a hemisphere. This ablates into vacuum and causes a push. There's substantial modeling effort and physics known about this process since Teller & Ulam's idea.
Re:Deflection (Score:4, Interesting)
Vaporizing is completely different than shattering. For starters, the remaining asteroid remains intact, while the vaporized rock leaves at high speed as jet engine exhaust. That works great.
Don't kid yourself that the size of the fireball has anything to do with the size of the crater it would produce though. The fireball is just superheated gas expanding through cool air, long after the blast has done its damage - it takes very little energy to produce compared to trying to vaporize or displace rock. Also, to get an appreciable crater you'd need to bury the nuke deep underground so that it blasts material upwards instead of down - similarly to how most of the energy of a meteor impact is delivered well below the surface as rock is vaporized out of its path.
And burying a nuke greatly increases the odds of shattering the asteroid rather than deflecting it. And that's almost certainly a bad thing. You've just turned a predictable rifle slug impact area that could be easily evacuated, into a shotgun blast.that will pepper the Earth with nuclear-size impact blasts. Even if half the material misses the Earth entirely, the total damage would be much greater - the size of an impact crater scales with the cube root of the impact energy (in this case, mass, since all else remains roughly constant). Break an asteroid into 8 equal pieces, and now you get 8 impact craters, each still half the diameter that the original would have been. Break it into 64 pieces, and each crater would still be 1/4 the size of the original. Even if half of them missed Earth, you'd still end up doing far more total damage.
About the only reason you'd want to risk doing that is if it was a *really* large asteroid that was going to hit the ocean, generating massive tsunamis and vaporizing a huge mass water that would devastate weather patterns for potentially years to come, doing far worse secondary damage.
And if the asteroid was that big, then even a Tsar Bomba buried in it's core might not be up to shattering it.
Plus there's the slight problem that unlike rockets capable of delivering it, we don't have any Tsar Bombas just lying around in storage (so far as I know), and building one is going to take time. time we wion't necessarily have, and even if we do, every second we wait to launch brings the asteroid closer and reduces the amount of benefit an explosion of a given size can achieve.
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Burying a nuke does seem very silly. Using 1000 smaller nukes as a propulsion system is probably the best we've got. Of course, if we magically detect the problem far enough away, we could just attach a solar sail, but we don't have a good track record of identifying problem asteroids that far ahead.
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Quite.
And no need for magical detection - we just need some decent array of IR telescopes capable of seeing back-lit asteroids, that can cover enough of the sky to map out the orbits of everything of appreciable size. We've already had a few such projects get scrapped due to lack of funding - all the magic we'd need is for someone with money to take the threat seriously.
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It's not just the telescopes, though we do need a lot more of those. It takes quite a bit of effort to do the tracking. We don't have the ability to track every asteroid continuously, not even close. We typically get very temporary views of moving dots that are hard to even identify as such. Often, we don't get enough information to predict an orbit. If we do, the best we have is to hope to catch the object on a future obit on the track predicted. It's no wonder so many of the recent near-miss asteroi
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That's why the asteroid-spotting plans typically call for an array of a low-magnification, wide field of view telescopes. I believe one of the major plans calls for dozens of telescopes that re-image the entire night sky (well, at least within several degrees of the ecliptic), many times per year (possibly even weekly?), so that computer analysis could rapidly identify and track each asteroid and compute its orbit. It wouldn't be perfect, but it would get most of the big stuff we really need to be worried
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Sounds like a good plan, with the computer analysis. Good news is launch costs keep dropping.
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Awesome. I'm far more confident of such a project getting adequately funded if someone thinks there's money to be made.
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And burying a nuke greatly increases the odds of shattering the asteroid rather than deflecting it. And that's almost certainly a bad thing. You've just turned a predictable rifle slug impact area that could be easily evacuated, into a shotgun blast.that will pepper the Earth with nuclear-size impact blasts.
Even asteroids have their binding energy. So if you detonate the nuclear explosive at proper depth underground at a sufficient distance from Earth (months before the impact, at the very least), even if the asteroid as a whole initially shatters, it most likely mostly gravitationally re-coalesce into one mass with a momentum changed by the negative of the sum of momentum change of the parts that actually flew away, impacting an impulse of at least giganewtonseconds or tens of giganewtonseconds.
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evaporating parts of it?
In this case sublimation (from solid direct to gas) not evaporation. But this does not cause matter to cease to exist. There are a few problems here. On earth you have many ways to transmit heat - conduction, convection and radiation. In space you only have a single way to transmit ANY sort of energy - radiation - unless you make physical contact with something. The radiation effect of a nuclear blast is pretty much instantaneous. By the time the bomb casing and bomb core has flown apart, you're not gett
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Yes, that's it, lots of X-rays ablating the surface.
The atoms which were heated to very high temperatures leave the asteroid at high speed into vacuum and there is a reaction force and net directional impulse to the remaining asteroid. Ablate one half surface of an asteroid and it pushes in one direction. We want to keep the asteroid whole and on a trajectory to miss Earth.
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For many asteroids, a 4km chunk is a significant fraction of the whole.
For most asteroids, you won't find a 4 km chunk in them because they're smaller than 4 km.
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Even fifty megatons won't deflect a rock the size of Texas.
If there were a rock the size of Texas anywhere near the inner solar system, we'd have spotted it long ago, and there would be a bunch of people still bellyaching that it should never have been demoted from being called a full-fledged "Planet".
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So what are we trying to achieve? (Score:2)
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Just paint the entire thing. Only the side facing the sun will be repelled by photon pressure. Of course, that means you can only get a deflection (roughly) directly away from the sun - no tacking is possible, but that would likely be good enough.
Re: So what are we trying to achieve? (Score:2)
That is my take away from this. The asteroid is badly fractured, so will have to be pushed or pulled very gently. Bruce Willis and Co. just makes a gravel pile where 90% keeps on course.
Are the scientists confused? (Score:5, Informative)
Re:Are the scientists confused? (Score:4, Informative)
No, it seems like TFA is confused. The paper isn't looking at deflection really, it's looking the possibility of shattering the asteroid.
Doesn't this depend on rotation? (Score:3)
If an asteroid is not rotating, it makes sense that if fractured into pieces by a thermonuclear explosion, the pieces will tend to drift back together in one place.
So our strategy for an Earth-impacting asteroid should be: if it is rotating, blow it apart and watxch the pieces fly away; if it is not rotating, nudge its orbit with a series of small explosions.
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Or, if it's not rotating, get it started rotating, then blow it apart.
Of course, a lot depends on how long before the hypothetical impact we detect the thing. If it's not going to hit for ten years, we've got a lot of options as to how to deal with it. Ten weeks? Not so much. Ten days? Have a world-wide "En
Re:Doesn't this depend on rotation? (Score:5, Insightful)
"Ten days? Have a world-wide "End of the World" party." - Including watching the 1999 Canadian film "Last Night" [wikipedia.org]... Plot: In Toronto, a group of friends and family prepare for the end of the world, expected at midnight as the result of a calamity that is not explained, but which has been expected for several months ... In 2014, Colin McNeil of Metro News wrote "Last Night is perhaps the most upbeat end-of-the-world movie you’ll ever see." ...
Rogert Ebert's review [rogerebert.com] ... Note: On a talk show in Toronto, I [Roger Ebert] was asked to define the difference between American and Canadian films, and said I could not. Another guest was Wayne Clarkson, the former director of the Toronto Film Festival. He said he could, and cited this film. "Sandra Oh goes into a grocery story to find a bottle of wine for dinner," he said. "The store has been looted, but she finds two bottles still on the shelf. She takes them down, evaluates them, chooses one, and puts the other one politely back on the shelf. That's how you know it's a Canadian film."
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Inducing rotation might take far more energy than either of my alternatives.
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I suspect that striking slightly off-center with explosives should be more than enough to cause it to spin and to keep components separate. I think that the difficulty is getting the explosives to expand the mass thoroughly and _not_ spin unpredictably.
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You really think the angular momentum of a rotating asteroid is going to make a huge difference compared to the forces necessary to blow the thing into a bunch of pieces in the first place?
Figure, the instant the asteroid is shattered, the fact that it was rotating make no more difference, except in that the outermost pieces are traveling on their straight-line paths a bit faster and in a slightly different direction than they otherwise would have been, thanks to the addition of their original velocity arou
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Or, just detonate a series of explosions in front of or behind it. Make sure the explosions are far enough away for the blast radius to cover the entire object. The goal being to spread a smaller force over the entire object to speed it up (moving it's solar orbit out), or slow it down to make sure it is removed from Earth's orbit either way.
We already have ICBMs that carry multiple warheads. The technology should transfer. Easily. Right?
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If an asteroid is not rotating, it makes sense that if fractured into pieces by a thermonuclear explosion, the pieces will tend to drift back together in one place.
So our strategy for an Earth-impacting asteroid should be: if it is rotating, blow it apart and watxch the pieces fly away; if it is not rotating, nudge its orbit with a series of small explosions.
Thermonuclear devices are the biggest boom we've been able to create. Unfortunately, the only asteroids which our nukes would effectively be able to nudge (or shatter) are those which aren't of cataclysmic size in the first place.
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... heat up one side of the object with lasers so that the out-gassing of materials generates a subtle thrust that gradually nudge the orbit.
If the object contains enough volatiles, this could actually work.
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Given a long enough lead time the method that seems coolest to me is the gravitational tractor method.
According to my (admittedly rudimentary) calculations, an underground nuke detonation forming a crater with maximal amount of ejecta would impact at least two orders of magnitude higher total impulse compared to a gravity tractor. It would also impact this impulse in a single point in time, a long time before the encounter with Earth, compared to a gravity tractor where effect of the impacted impulse would be diminished by virtue of a major part of it happening much closer to projected impact on Earth (ther
A matter of cost. (Score:5, Funny)
link to the actual source, which does makes sense (Score:4, Informative)
https://hub.jhu.edu/2019/03/04... [jhu.edu]
Looks like the editors did not even look at it and just "aggregated" the content from some random news site that also was no capable of summarizing the hart of the matter in a subject line.
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Or, just land a rocket on the asteroid nose-first, and start pushing. Since you have virtually no gravity to deal with, Landing could probably be handled by redirected attitude jets. The big problems will just be balancing against the thrust of the engines, and transmitting the force through the entire length of the rocket to the nose.
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That would just be the start of the big problems. Where do you land? That is important because:
- if you're not at the center of mass, your rocket fuel will be spent to make the rock spin.
- if the spot you land on isn't level with the center of mass, your rocket will point in the wrong direction, and your rocket fuel will be spent to make the rock spin.
- if the spot you land on isn't flat your rocket will fall over
- if the spot you land on isn't solid, your rocket will fall over
- if the spot you land on do
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> if you're not at the center of mass, your rocket fuel will be spent to make the rock spin.
That should be "in line with" rather than "at", but in that case yes, some of it will. But unless you're more than 45 degrees from vertical, most of it will go towards deflection.
There's always a direct line between you and the center of mass, and it's easy to find it: just dangle a sensitive plumb-bob to find exactly which direction gravity is pulling in. Your rocket will need adjustable legs so that it can lan
Huh? (Score:3)
Nobody wants to deflect an asteroid with another one. That would be stupid. Instead of getting 10000 tons on our head in 1 piece it would just come down in several.
Landing a drive on the sucker is easier, if it far enough out there.
The biggest problem is error bars (Score:2)
Correct me if I'm wrong, but the true nature of the problem is that the further out we detect the object, the more uncertainty there would be about whether it will hit Earth or just be a close near miss.
But it needs to be detected far out to have time to plan, build, execute the intervention.
What if we spend the 100s of billions of dollars needed to do an intervention like ion engine course correction, or painting, and then find out as it gets closer that, well, it looks like it most
Only two conditions would make it feasible (Score:2)
AND
2) The intervention (e.g. rotation-timed ion engine push) needs to be enough of a correction to alter the trajectory by a lot more than the error bars on the trajectory estimate. So a lot of energy will need to be delivered. The math, anyone?
Use our Natural Shield, The Moon. (Score:2)
Capture in orbit around or impact it upon the Moon.
We that natural defense with significant mass and gravity.
Just look at all the craters on it, that stuff could have hit the Earth instead.
rods from god approach. (Score:2)
Regardless, they will try different
UPI BS Headline: Nothing To Do With Deflection (Score:2)
Read the crummy UPI story, and the original paper, and there is nothing in the paper or the scientist's quotes that is either about, or pertains to, deflection of asteroids, except for three sentences of the reporter bloviating about it. The reporter apparently believes, based on nothing, that asteroid deflection means "destroying the asteroid".
This paper is about how asteroids fracture and reassemble in collisions with other asteroids and thus the typical structure to be expected. It is an advance in the s
Trying to use a hammer to solve net problems (Score:2)
It seems to me you have people who have hammers, who love hammers, who want to use hammers for everything, even for buttering bread.
Who should be using a net.
Distributing lower amounts of force over a longer period of time, using a net to attach to an asteroid and ion drives to slowly alter the orbit, is a far more useful method of deflection than a short sharp shock. Getting that much energy at one point for a short duration is very very expensive in orbital mechanics, especially from earth surface, where
What about soft deflection over time? (Score:2)
The best option is to develop better technology to detect asteroids farther away (a series of monitoring satellites covering all quadrants overlapping). Once detected other methods than brute force could be applied. I've seen ideas like using solar wind/particles to move it by making one side of the object a black body (to absorb energy - and thus apply a force), to applying force directly by 'docking' with it and using rockets to nudge it off course.
The real problem isn't how to move the asteroid, the
Its all just Math (Score:2)
Re:Isn't the goal to change its course? (Score:5, Insightful)
The difference is that the birdshot has a better chance to burn up in the atmosphere without anything reaching the ground at all.
Re: Isn't the goal to change its course? (Score:1)
It makes absolutely no difference, the kinetic energy will have to go somewhere anyways - whatever it is one large piece or many smaller ones. The result will be the same as the rocks will fall around the same time (so there wonâ(TM)t be enough time to disperse the energy between each collision).
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The difference is that the birdshot has a better chance to burn up in the atmosphere without anything reaching the ground at all.
For a large enough asteroid that doesn't actually help. The same total amount of energy is dumped into the atmosphere, and we all cook. It's hard to come up with a scenario where rolling the dice on breaking up an asteroid into an unknown number of pieces of unknown size and trajectory is a win. Perhaps if a mid-sized asteroid were going to hit the ocean (and we could somehow predict it that accurately), we might take the risk of random land hits to avoid the tsunami.
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You know nothing about physics. Kill yourself.
The uneducated only become educated through the sharing of knowledge, asshole. I'm certain there are things you know nothing about (it's called being human), and yet I'm not condemning you to death for it.
Re:Isn't the goal to change its course? (Score:5, Insightful)
If a large asteroid on a collision course with Earth is fractured, that just turns it into a bunch of little asteroids that will hit Earth.
Not really. Space is big. Really big. If you break up an asteroid months, or even weeks, ahead of time, most of the fragments are going to miss earth by many thousands or even millions of kilometers.
A typical delta-v is 40,000 km/hr. So in a day, that is a million kilometers. In a month, it is 30 million km. The diameter of the earth is 12,000 km. That is about 0.02 degrees. That is not much of a deflection.
Re:Isn't the goal to change its course? (Score:4, Interesting)
There have been many, very useful analyses of the trade-offs. I've seen many in fiction and science speculative scientific analyses: I remember reading J. E. Enever's analysis in a 1966 Analog magazine article. Given how little was known about the composition of asteroids that had never struck the Earth to be analyzed, and that the article predated the discovery of the dinosaur killer asteroid, it was quite good. Asteroids are high velocity projectiles, and whether they are solid rock, reasonably metallic, or icy makes enormous difference in the results of breaking them up.
Orbital mechanics and basic geography physical chemistry haven't changed much since that period. Guidance systems have improved tremendously, and humanity has learned a great deal about sending small probes to other worlds. But changing the orbital path, or shattering, something as large as a dinosaur killer asteroid is still an incredible engineering problem.
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We're not good at detecting dangerous asteroids while they're still at any distance.
We don't have the capability to deliver any meaningful mass (hundreds of tons) to an asteroid at a sizable distance, especially if it's moving very fast relative to the Earth.
Even if we did solve those problems, it's almost always going to be better to give the whole asteroid a predictable nudge than to risk breaking it into random-sized pieces still mostly going the original direction. And the farther out the asteroid is,
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I think the point is that even if you shatter it, it pulls itself back together and brings in whatever hit it to add to the overall mass making the overall problem even worse.
Deflecting it would require a lot of sustained energy to push it in a new direction.
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Re:Two thermonuclear blasts. (Score:5, Insightful)
Go take a look at the long list of asteroids that have passed frighteningly close to Earth, that we didn't see until they were already past.
The problem is that we have a 50/50 chance that the asteroid will approach us from inside our orbit, in which case the side facing us will not be lit by the sun, rendering it nearly invisible (though the IR telescopes designed specifically for spotting asteroids by their heat signature will do better)
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Go take a look at the long list of asteroids that have passed frighteningly close to Earth, that we didn't see until they were already past.
In other words, asteroids that were too small to notice earlier...
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If size was the issue, you'd see them for just as long coming as going. The problem is light. An unlit object in space is completely black in the visible spectrum. And black also happens to be the exact shade of empty space. The result being that anything coming at you from the general direction of the sun, and thus only being lit on its far side, is completely invisible.
You start getting a slight visible crescent as the angle between the asteroid and the sun expands, but we know the Earth probably has
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>Fortunately, there's also this 1360 W/m^2 light flux near 1 AU making things significantly easier for us.
Which is only useful if we are between the asteroid and the sun. That's my point. My shining a flashlight towards you doesn't help you see anything between us, except in silhouette. And there's no background in space for a silhouette to be visible against.
Worse, we're not actually looking. Current astronomy amounts to a few hundred people looking through drinking straws at the sky - the vast maj
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You are right - I should have said the sun needs to be on the same side of the object as us, not necessarily behind us. Venus and Mercury orbit separately from Earth, so they're often at the opposite side of the sun from us, and with the sun between us, they're illuminated.
Most near -Earth asteroids never get far enough from Earth for that to work though. They wander within about +/- 60 degrees of Earth in roughly the same orbit, and while they get better lit in terms of percentage of surface area the fur
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As for my "relative close up view", picture this: If we're trying to, from Earth, see something at the L5 point, 60 degrees away in our orbit, we're trying to see something from 1 AU away, with only a sliver of visible crescent
If you want to see whatever has somehow accumulated in Earth-Sun L4/L5, or even L3, why not simply send a small probe to those specific places?
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1) because you don't want to see what's at *one* specific place - you want to see what's at *all* the specific places something might be
2) because if you're sitting at the L5 point, asteroids "orbiting" around that point could be passing you in any direction in 3D space - you'd want an omni-directional camera to avoid missing anything, and you'd still end up having a lot of things passing you closer closer to the sun so you couldn't see them. Much easier to sit with the sun at your back, and be relatively
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because you don't want to see what's at *one* specific place - you want to see what's at *all* the specific places something might be
Objects changing their relative position to Earth (i.e., objects not at L4/L5) should be already covered by telescopes on or near Earth, since they'd have to pass fairly nearby from time to time.
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Except, you're not going to find things *at* L4/L5, you're going to find things "orbitting" them on all sorts of strange paths, and not necessarily just neatly planar ones.
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I don't believe we've even begun to exhaustively characterize all possible Lagrangian orbits, though I could be wrong about that.
But for starters, every single orbit that passed near you (as seen from "above"), substantially out-of-plane. You'd need a camera with a near 180* field of view along at least 1 axis, perpendicular to the ecliptic, to be able to spot all possible orbits, while still being able to spot an asteroid from hundreds of thousands of miles away, since those halos can be large. And you'd
Re:Two thermonuclear blasts. (Score:4, Insightful)
I'm trying to figure out what you might mean, given the fact that asteroids are typically invisible to radio telescopes, and the amount of radio power you'd need to broadcast to illuminate even a tiny sliver of the night sky brightly enough to spot an asteroid from half a billion km away would be mind-boggling.
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You know, you're right! I apparently replied to the wrong comment, and then completely failed to notice.
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(like a comet would flying towards the sun does which eventually causes it to propel back out into space)
If I understand you correctly, you suggest that comets are flying directly towards sun, get decelerated by ablating gas, stop and then accelerate away like a rocket. I suppose that you imagine that at some point they stop spewing gases, but gravity still works, so they will finally come back. Just in case - this is completely wrong image. Comets are orbiting Sun and 'missing' it when they fly in, getting around Sun on tight gravity leash and flying back, still in very elongated orbit. Comet tail is way too
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The asteroid is probably mostly rock, instead of the ice that comets typically have. But, having the bombs detonate at a distance in order to repeatedly blow (puff) at the comet will speed it up or slow it down eventually. Also, to escape two dimensional thinking, moving the orbit out of the solar plane would also make it much less likely to ever come near the Earth again.
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Cant read TFA because of my ad-blocker - ads are more important than the future of the World.
Sounds like BS though, what have colliding asteroids got to do with deflecting one? Are we going to try to knock their silly heads together?
the fractured core exerts a strong gravitational pull on the smaller pieces of debris and shrapnel broken during the impact
More BS. Unless the asteroid is getting on for the size of a planet, in which case abandon all hope, the gravitational force will be very weak.
If scientists are going to develop an asteroid deflection strategy that can actually work, they need to know how much force it really takes to destroy or deflect one
WRT deflecting, I was taught at school that the force on a object multiplied by application time resulted in an increase in that object'
Re:Fractured what? (Score:4, Insightful)
Indeed. If it takes more force than originally estimated to fracture an asteroid, that's a *good* think - it makes deflecting it easier. Fracturing is one of the things most asteroid-avoidance plans want to avoid.
You only want to shatter it (and only maybe) if it's already too late to deflect it - doing so turns a rifle slug who's impact point we can predict, into a shotgun blast that'll hit all over the place, but probably some of it will miss, and more of it will burn up in the atmosphere so that individual impacts are less damaging. The overall effect is likely to be more devastating though - unless the original impact point would have been something especially bad.
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The problem is that impact doesn't scale linearly with size - the size of the crater scales with the cube-root of the blast energy - in this case the mass, since we won't be appreciably modifying the impact speed. Break an asteroid into 8 chunks, and now you have 8 impacts, each still having half the blast radius of the original. 64 chunks would each have a blast radius 1/4 the size of the original.
And while we may not be able to accurately predict the impact point months or years in advance, it gets easi
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Break an asteroid into 8 chunks, and now you have 8 impacts, each still having half the blast radius of the original
You are assuming that the 8 chunks all hit Earth. That is extremely unlikely unless you let the asteroid get very close first : within the moon's orbit say.
If you know that the asteroid is going to hit Earth, then breaking it up at eg the radius of Mars orbit will send the fragments into a cone of debris which, by the time it reaches us, will be spread over an area vastly more than the target area of Earth - even if that cone angle is quite small. Earth is a tiny target from the distance of Mars (just look
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Of course then you bring in one of the articles' findings - if the cone is too small, the asteroid will re-coallesce. And one of the big problems with shattering as a goal is that you don't significantly change the path of the center of mass - so Earth will still be right in the bullseye.
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Of course then you bring in one of the articles' findings - if the cone is too small, the asteroid will re-coallesce.
Only if nothing reaches escape velocity, which is reasonably easy to prevent. In fact, it's very difficult to arrange for anything else to happen.
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Perhaps, but I think you're underestimating how much energy is needed to move mountains. I'll run some numbers to confirm:
Lets take a modestly large asteroid, say 10km across, the lower extreme of the 10-80km size estimate for the dinosaur killer. There's an estimate 10,000 asteroids that size or larger. Maybe make it a bit bigger to make it an even 1000cubic kilometers, and we'll say it's a nice low-density icy asteroid, at around 1kg/L. So the whole thing masses about 10^15 kg
Then we'll hit it with a T
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Except projectile orbital motion always brings you back to where you began. Every single one of those fragments will return to the detonation point at the end of every orbit. And the orbital period will not have been appreciably altered by a few m/s change, so they'll all be doing so at roughly the same time.
It's similar to the problem of trying to launch something into orbit using some sort of "cannon" on the planet's surface - it can't be done, because after one orbit the object will pass back through t
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Except projectile orbital motion always brings you back to where you began. Every single one of those fragments will return to the detonation point at the end of every orbit. And the orbital period will not have been appreciably altered by a few m/s change
It will if it's at least few tens of meters per second (near 1 AU). So it's a matter of getting the ejection velocity statistically right (in the sense of imparting just enough velocity to as large mass fraction as possible). If that happens, why care about when another encounter between the fragments happens if it happens after hundreds of orbital periods or more? By that time, we'll have completely different means to solve the situation, I'm sure.
It's similar to the problem of trying to launch something into orbit using some sort of "cannon" on the planet's surface - it can't be done, because after one orbit the object will pass back through the point where the cannon was located, and impact with the surface.
It's not really similar because the movement of Earth aroun
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A 1% speed change... yeah, I guess after a year thing will have spread out enough it wouldn't be an issue. I'm sure it might re-coallesce eventually, but as you said, we should hopefully have better solutions at hand - if we haven't already mined the fragments to nothingness.
>So as to maximize the momentum change of the remaining mass.
Fair enough. Except - maximizing the momentum change isn't actually your goal. Minimizing the risk to Earth is. Unless it's a *very* last-minute operation, you've got m
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It depends on if he dies because he stays behind to make sure the bomb goes off.
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You'd obviously have to tamp the nuke, and detonate it inside the asteroid. I think there was a movie about that, something about a deep sea drilling team. This recent study actually goes directly to that: the energy required to break up a large asteroid enough to matter is just too high.
However, if the goal is to re-direct an asteroid, instead of break it into gravel, nukes are a good fuel source. "Project Orion: style propulsion is really easy if the ship deosn't need to survive. It still might not b
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As for wasting energy from the blast into space, there are approaches to mitigating that, which go all the way back to Project Orion. [blogspot.com]
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Straight ablation across one hemisphere seems like the best idea and change the orbit. Use something like the huge Spartan warhead encased in gold (for maximum x-ray creation). This was already created to heat and fracture the high Z atoms in enemy warheads and should work OK on a nickel-iron asteroid.
Best scenario would be to have years of warning, and land powered ion engines which could be controlled and chang
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I still don't understand how exploding one in space where there is no air is supposed to alter the trajectory of a hugely massive object
You explode it in a reasonable depth below the surface, so that the largest possible amount of the asteroid's mass is ejected at a speed somewhat higher than local escape speed (which is usually meters per second or so), to maximize the terminal momentum of the ejected mass. Bunker buster technology like the B61 Mod 11 bomb should be suitable; the cohesion of the asteroid's surface is unlikely going to be higher than Earth's regular soil.
Of course. All mass attracts all other mass (Score:2)
In other words, it would tend to re-assemble, but in fairness, that would take a long time if they were actually substantially separated.