From Wired:
Any number of undiscovered near-Earth objects could one day careen into the Earth, and there is a lot of talk here at the American Geophysical Union meeting about tracking them. So far, though, only one discovered object has seemed even mildly likely to hit our planet.That asteroid is Apophis, a 900-foot asteroid. Calculations released on Christmas Eve 2004 appeared to show that there was a greater than 2 percent chance the asteroid would hit the Earth in 2029. The asteroid appeared ready to give the Earth its closest shave since astronomers began looking for such things. It was judged a 4 on the Torino Impact Hazard Scale for a short time, the highest rating any near-Earth object has received.
As it turned out, more precise observations brought the risk of collision down to just 1 in 250,000, but the scare sparked greater interest and study in the fields of asteroid detection and defense.
While the risk remains small, this might provide a test of Eric’s hypothesis, though it appears there are distributional consequences (and hence diplomatic obstacles) to asteroid deflection just as there are for climate change.
(Links via Instapundit)
JaimeInTexas (Jam) says:
I will fight for my survival regardless if it benefit someone else.
Whether others do anything about an asteroid on a collision course with Earth is irrelevant. These uS should do all we can, including amending the Consitution, to face the catastrophe. Now, if the impact is somewhere other than in North America ... JaimeInTexas (Jam)(Quote)
JaimeInTexas (Jam) says:
I will fight for my survival regardless if it benefit someone else.
Whether others do anything about an asteroid on a collision course with Earth is irrelevant. These uS should do all we can, including amending the Consitution, to face the catastrophe. Now, if the impact is somewhere other than in North America ... JaimeInTexas (Jam)(Quote)
Allan Walstad says:
It seems as though one or more nukes would do the job, providing a finite nudge that would not gradually sweep the impact location across the Earth. I find it hard to take “diplomatic obstacles” seriously. You send off a space mission with nukes and save the world. Who’s going to do anything about it?
Please refresh my memory regarding Eric’s hypothesis. Allan Walstad(Quote)
Rusty Bill says:
The differences between a potential asteroid impact and climate change are obvious... one is a catastrophic event that is mathematically predictable, the other is a long-term natural phenomena that hasn’t resulted in extinction yet (and won’t, unless you believe falsified data).
As for deflecting an incoming asteroid, I think ion thrusters (given sufficient lead time) would be more useful — and safer — than nuclear detonations. I’d rather push the thing out of the way than turn it into a shotgun blast.
ObRef: Lucifer’s Hammer by Niven & Pournelle (Wikipedia link)
(Edit: gotta lern how to spel) Rusty Bill(Quote)
International Law is an Asteroid Suicide Pact « The View From LL2 says:
Ken Arromdee says:
http://volokh.com/2009/12/03/asteroidgate/
He suggests that if the world was imperiled by an asteroid instead of by global warming, we would and should ignore “astronomy skeptics” and not give them the credence we do for global warming, even if there was a Climategate-like scandal.
Problems include:
– the misconduct he describes for asteroidgate doesn’t cover all the misconduct in climategate
– asteroids are easy to observe and it’s hard to fudge asteroid data
– asteroids are routinely observed by amateurs who have never published in peer-reviewed journals about the asteroid, and their observations are welcomed
– it’s hard to fudge the date of an asteroid strike; anyone who claims catastrophe by a certain date, which doesn’t happen, would lose credibility. They can’t push the catastrophe date forward like for global warming.
– stopping an asteroid would not cataclysmically alter the economy or our lives. Furthermore, stopping the asteroid is mostly a one-time expense, not a demand that we cripple our economy forever.
– there aren’t all that many people whose ideology just happens to demand the same things we’d also need to do to stop an asteroid
And finally... we are in a certain amount of danger from asteroids (though not from a specific asteroid), and we are not spending any money to prevent impacts, which seems to contradict his thesis anyway. Ken Arromdee(Quote)
Soronel Haetir says:
Ken,
Um, I would say there are plenty of space nuts with such an ideology. Soronel Haetir(Quote)
Allan Walstad says:
Ken Arromdee: Thanks for the refresher! I remember, it was one of two “analogies” to climategate offered by Eric Posner, both of which were pretty well debunked as such by the commenters.
Rusty Bill:
I was talking about using nukes to push the thing out of the way, not blast it to pieces. To the extent that the explosion did generate debris, some of which entered the Earth’s atmosphere, it would not likely cause much or any damage. Allan Walstad(Quote)
sureyoubet says:
The time for talk was over in 2004. sureyoubet(Quote)
Dylan says:
How do nukes push an asteroid around in a vacuum? Hit it with lots of particles, sure, and heat up whatever side you’re in contact with, but a hard push doesn’t seem likely. Dylan(Quote)
pmorem says:
One more item for Ken’s list:
Nations that do not want to participate in preventing an impact can free-ride without dereailing the action.
Asteroid impacts are a very different kind of collective action problem in that it only takes one actor, rather than all acting together. pmorem(Quote)
Michael McNeil says:
I was talking about using nukes to push the thing out of the way, not blast it to pieces. To the extent that the explosion did generate debris, some of which entered the Earth’s atmosphere, it would not likely cause much or any damage.
I think that’s very wrong. Since many asteroids appear to be little more than rubble piles, very loosely held together by self-gravitation, even a light push could likely produce a number of large, rocky fragments that, as a “shotgun” blast impacting the Earth, could indeed do far more damage than a single “bullet” would.
As to the ion rocket idea proposed above, I like the ”gravity tractor” concept, where a fairly massive spacecraft would simply hover near the asteroid (likely utilizing an ion rocket, to be sure) whereupon its gravity would then pull (rather than push) the asteroid out of its collision course with Earth — meanwhile applying no direct force that could cause a rubble-pile asteroid to shatter into numerous fragments.
Obref: Larry Niven’s A World Out of Time Michael McNeil(Quote)
ptt says:
I’m surprised no one has suggested the obvious. Repeal California’s term limitations and leave Ahnuld in office until 2029.
He’ll take care of the asteroid. ptt(Quote)
Ken Arromdee says:
There aren’t enough to matter in any political endeavor, and the ones who exist get ignored–unlike supporters of anti-AGW measures who just happen to want us to get rid of cars anyway. Ken Arromdee(Quote)
Allan Walstad says:
Naturally, one assumes the nature of the particular asteroid would be investigated prior to any attempt to deflect it. If it is, say, a carbonaceous chondrite, then one simply explodes the nuke farther off. Remember, you don’t get a blast wave in space. A nuke at the right distance heats the surface, vaporizes rock/volatiles as the case may be, which in expanding produce the right amount of force. Come to think of it, if the asteroid is really icy, more like an old comet, then positioning a large reflector so as to heat up one side will do the same trick Just depends on what we’re dealing with, which I assume we’d try to find out first.
I’m not wedded to nukes, but the idea that some test ban treaty or international suspicions should be allowed to stand in the way of an effective deflecting method is just absurd. Allan Walstad(Quote)
Rusty Bill says:
Absolutely no argument there. If it comes to a choice of “violating” a treaty or surviving, I’ll choose survival first, then argue about the treaty later — if there is a later... Rusty Bill(Quote)
Tweets that mention The Volokh Conspiracy » Blog Archive » AsteroidGate — For Real? -- Topsy.com says:
Allan Walstad says:
Rusty: Fair enough. Allan Walstad(Quote)
AsteroidGate — For Real? | Liberal Whoppers says:
JK says:
Based on your extensive experience shooting nukes at asteroids?
Seriously, based on these comments I have no doubt that there would be the same group of amateur experts spouting any line that sounds basically plausible if unexamined in an asteroid situation as with AWG. That said I think we need to wait and do more research regarding AWG before we wreck our economy, but that’s completely different than loons claiming that it’s all a big hoax. JK(Quote)
LarryA says:
It all depends on how early you hit it. If you blow up an asteroid far enough away that the majority of pellets miss, you’ve solved the problem permanently. And you can do it with existing technology. (Although not with ICBMs, like in the movies.) LarryA(Quote)
Allan Walstad says:
Based on a fair knowledge of physics and astronomy, bachelor’s in the former, PhD in the latter. The orbits of icy asteroids are indeed affected by solar heating causing evaporation and gas pressure force–sort of a rocket or thruster effect. The release of energy in a nuclear device would vaporize surface material and cause a large version of such a thrust. We have nukes, we have the propulsion technology to get them there. I don’t think there’s any doubt that a small asteroid’s trajectory could be deflected in this way. Of course, the specifics would depend on the combined expertise of many people.
As far as debris not causing damage, again, anybody who knows anything about astronomy knows that small meteoritic material enters the Earth’s atmosphere everyday, being vaporized in the atmosphere or, if a small remnant reaches the ground, it would have to hit you right on the head to hurt you. Larger rocks could pose a damage to individuals and buildings, but not produce the sort of explosions that would cause destruction over a large area. You wouldn’t want your deflection effort to break the asteroid into just a few large pieces that all end up hitting the Earth, of course. Allan Walstad(Quote)
Michael McNeil says:
The orbits of icy asteroids…
A goodly number of asteroids are not icy; a significant number are fragments chipped off asteroids like Vesta which melted while young (as a result of radioactive decay of isotopes of elements like aluminum), and hence are composed of an iron alloy core surrounded by a rocky crust much like big terrestrial planets like Earth. Fragments spalled off them will thus be either rocky or iron-y.
A gravity tractor will work on any kind of asteroid, nor are the ion rockets allowing it to hover near its intended drag target for extended periods of time particularly risky technology. Michael McNeil(Quote)
iawai says:
Why is a forced solution assumed? Can’t a voluntarily funded “asteroid deflection project” work, and let the crank scientists be wrong and be shunned for not supporting an eventual successful deflection?
If you see a problem, spend your resources to fix it, rather than spending them on forcing others to fund it. Maybe some people want Earth to be hit by an asteroid, maybe some think we need solar sails, maybe some think we need to scope it out for life before blowing it into chunks. There are so many permutations, options, viewpoints, and outcomes that trying to find a politically forced solution seems like a Sisyphean task, all the while ignoring the aggression necessary to implement any such solution. iawai(Quote)
lgm says:
Comparing asteroid-gate to global warming science — there was a preliminary projection that the asteroid might hit the earth. This was significant to warrant more careful measurements. Said measurements show that there was no danger. Case closed. Global warming science starts the same way — preliminary projections and measurements show there might be a problem. But this time more careful measurements and more detailed theory confirm the problem.
As for redirecting the asteroid with a nuke, one would have to understand conservation of momentum. If you break an asteroid into pieces, the average of the velocities of the pieces will be the velocity of the original. If there are lots of pieces, that means some should hit the earth. lgm(Quote)
Allan Walstad says:
Right. You would probably set off the nuke closer to one made of more refractory materials to insure sufficient vaporization of surface material and resulting gas pressure to deflect it. No doubt it’s possible that the process will result in a few errant boulders that might still strike the Earth, but the catastrophic impact will have been averted. Nukes and propulsion systems to deliver them are available. As soon as you’re finished developing the means to deliver a gravitationally significant mass to the vicinity of an asteroid and hold it in position for an extended period, I’ve got no complaint with using it. Just don’t send me the bill, ok?
You may be certain that I understand conservation of momentum, lgm. The point of using a nuke is not to break the asteroid into pieces. Rather, by setting it off at the right distance from the asteroid, you vaporize the surface material on one side and the gas pressure from the high-temperature vapor is what deflects the asteroid. It’s sort of like giving the asteroid its own rocket engine for a brief period. Allan Walstad(Quote)
Adam J says:
Michael McNeil– obviously breaking the asteroid into multiple asteroids that hit us would be far less effective then simply diverting the asteroid, however it would be less catastrophic then then it hitting the earth as a single asteroid. An asteroid broken into smaller asteroids before hitting the atmosphere would result in more surface area being exposed to the atmosphere and far more of the asteroid’s mass would be vaporized before hitting the ground. Adam J(Quote)
Mikee says:
In asteroid deflection, the third world nations would have no call to demand payment through international diplomatic means from the richer nations of the world for “asteroid remediation” before the damage to their countries occurred. And after it occurred, if it did, the remediation would likely not be performed by giving local dictators vast amounts of money to squander as they see fit.
So this is another asteroid impact versus climate change analogy where the asteroid issue is different than climate change issues. Mikee(Quote)
Michael McNeil says:
An asteroid broken into smaller asteroids before hitting the atmosphere would result in more surface area being exposed to the atmosphere and far more of the asteroid’s mass would be vaporized before hitting the ground.
As the 1908 Tunguska event vividly illustrates, an asteroid fragment that fails to physically reach the ground, due to being vaporized en route through the atmosphere, can still have a tremendously devastating effect. Anybody want to have a “shotgun” of multiple Tunguskas striking the Earth all at once? Michael McNeil(Quote)
Michael McNeil says:
As soon as you’re finished developing the means to deliver a gravitationally significant mass to the vicinity of an asteroid and hold it in position for an extended period, I’ve got no complaint with using it. Just don’t send me the bill, ok?
As Edward T. Lu and Stanley G. Love (both with NASA Johnson Space Center, Houston) point out in “Gravitational tractor for towing asteroids” (Nature, Vol. 438, No. 7065 (10 November 2005), pp. 177–178), a “20-tonne gravitational tractor hovering for one year can deflect a typical asteroid of about 200 m diameter given a lead time of roughly 20 years.” As they note, a longer hovering time or a larger tractor mass would reduce the required lead time proportionately. Moreover, as they say:
“The thrust and total fuel requirements of our mission example would be well within the capability of proposed 100-kilowatt nuclear-electric propulsion systems, using about 4 tonnes of fuel to accomplish the typical 15 km s^-1 rendezvous and about 400 kg for the actual deflection. For a given spacecraft mass, the fuel required for the deflection scales linearly with the asteroid mass.
“Deflecting a larger asteroid would require a heavier spacecraft, more time spent hovering, or more lead time. However, in the special case in which an asteroid has a close Earth approach, followed by a later return and impact, the change in velocity needed to prevent the impact can be many orders of magnitude smaller if applied before the close approach.”
Does anyone seriously believe that delivering a 20-tonne spacecraft to the asteroid belt would be so expensive (especially compared with the destruction an asteroidal impact could impart on the Earth) that it would be impractical or inordinately costly? Michael McNeil(Quote)
Michael McNeil says:
The Cassini (orbiter + Titan probe + en route propellants) mission to Saturn (located far beyond the asteroid belt), as delivered to space by its booster and launched in 1997, had a mass of 5,600 kg, which is more than a quarter the size of the 20-tonne gravity tractor discussed above. Michael McNeil(Quote)
John A. Fleming says:
An uncertainty of nukes is that most asteroids have some sort of rotation. Depending on the orientation of the rotation vector to the velocity vector, and the rotation rate, a nuke will be less effective than otherwise first calculated. This means that in order to calculate the number of nukes, the first thing to do is determine the orbit, rotation, and composition in detail. The fastest way to do this is a single flyby imaging craft. These are simple to build and launch. It’s not clear if we have the industrial capacity to make such a craft in less than a year, and then it will take several years for a flyby. The flyby craft can also have a penetrator sub-payload that it images impacting the surface.
The nukes then take longer to arrive, because they will be on a rendezvous trajectory.
If we really don’t have the time, the first flyby craft establishes the detail data that the flyby/intercept nukes need. Each nuke spacecraft will also have an imaging and/or radar payload to track the asteroid. Timing becomes much more critical if the nukes are on a flyby trajectory.
What makes a gravity tractor a better proposition, if we’ve got the time, is it’s semi-independence of composition and rotation. So maybe we can’t launch a 10 kiloton tractor, but we can launch and fly multiple 3 kiloton tractors. Launch as many as we need, plus some.
And finally, these are not missions to the asteroid belt. They are Apollo/Amor asteroids, and trajectories to them can roughly be considered to have transfer delta-vees similar to going to Venus or Mars. Much depends on the angles between the orbit planes. John A. Fleming(Quote)
Michael McNeil says:
So maybe we can’t launch a 10 kiloton tractor…
As noted above, 20 tonnes (20,000 kg) is sufficient is most realistic cases, no 10 kilotonnes (10,000,000 kg) or even 3 kilotonnes (3,000,000 kg) required. Michael McNeil(Quote)
John A. Fleming says:
A metric kiloton = 1000 tons = 1,000 * 1,000 kg. You’re right, my stupid mistake, that’s an example of why multi-tasking increases the opportunities for defects. It should read:
“So maybe we can’t launch a 20 tonne tractor, but we can launch and fly multiple 5 tonne tractors.” John A. Fleming(Quote)
Allan Walstad says:
John A. Fleming:
Nukes exist. The necessary chemical propulsion systems exist and we have a lot of experience with them. It is quite clear that this technology can deflect a small asteroid. Why should resources be devoted to developing unproven technology to meet a so-far non-existent threat, when we have the basic technology to do the job right now, if the threat materializes?
In fact, the vaporization of surface material and resultant impulse would surely take place on a short timescale compared to the rotation rate. Even if that were not the case, it would be easy to position the nuke along the axis of rotation. A nudge in almost any direction, applied at the right time, will work. Allan Walstad(Quote)
Michael McNeil says:
Why should resources be devoted to developing unproven technology to meet a so-far non-existent threat, when we have the basic technology to do the job right now, if the threat materializes?
In the first place, a working nuclear-electric drive would be a great engine for propelling space expeditions, so it would be highly worthwhile developing that technology anyway. Secondly, as far as its being “unproven technology” is concerned, are you really asserting there’s some question as to whether it would work? Lastly, as noted before, nuclear detonations are likely to shatter some kinds of asteroids, increasing the danger of their colliding with Earth, thus a careful survey of a proposed target would have to be made before one would dare apply that existing technology to that task. Michael McNeil(Quote)
Allan Walstad says:
Fascinating. This really does sound remarkably similar to the AGW proponents’ claim that we should be doing all the stuff to avert global warming because we should be doing all that stuff anyway. No sale on that. But more to the point at hand, if you and your friends want to chip in your own money to develop nuclear-electric space propulsions, by all means go ahead. What’s “highly worthwhile” is different to different people. If we needed that technology to save us all from certain catastrophe, that would be one thing–but, apparently, we don’t.
In principle, no. In practice, sure. Given unlimited time (not to mention money) to iron out the kinks, no doubt the technology can be developed. Given a finite window of opportunity, I’d reach for proven technology.
As claimed, or suggested, or speculated before. I don’t know where you get this “shattering” from. We are not detonating a nuke inside the asteroid, and there is no blast wave in space. What you get is a large amount of radiation that heats some of the surface, causing an impulse due to gas pressure. This impulse is in ONE direction. The bulk of the asteroid is deflected. If a few rocks are left behind, on precisely the same orbit as before the mission (so that they will hit the Earth), they are not going to cause damage remotely like the asteroid impact would have–if any at all. Allan Walstad(Quote)
Michael McNeil says:
I don’t know where you get this “shattering” from. We are not detonating a nuke inside the asteroid, and there is no blast wave in space. What you get is a large amount of radiation that heats some of the surface, causing an impulse due to gas pressure. This impulse is in ONE direction. The bulk of the asteroid is deflected. If a few rocks are left behind, on precisely the same orbit as before the mission (so that they will hit the Earth), they are not going to cause damage remotely like the asteroid impact would have — if any at all.
There is no atmospheric “wave” in a nuclear explosion in space, but there certainly is a considerable amount of material shooting at very high speed in all directions, and the portion that intercepts the asteroid is going to apply a sudden pressure upon it, in addition to simple radiated heat (and the heat itself applies a sudden impulse, as you admit). “Rubble-pile” asteroids, which as noted before are very loosely bound by self-gravitation, may well be disrupted into their constituent fragments (some of which can be very solid — rock or iron — asteroids in their own right, and quite sizable) which if they were to impact the Earth could do an enormous amount of damage to it and us. Michael McNeil(Quote)
Allan Walstad says:
Depends on what you mean by “considerable.” The exploding uranium is only, what, a couple dozen kilograms? Even the rest need not add up to more than a few hundred or thousand. You are setting it off at some distance from the asteroid surface, so no, there really is not a lot of material from the nuke striking the surface. The overwhelming effect is heat from radiation. The distance used would depend on the type of asteroid I’m sure. The impulse is in ONE direction. Even if the asteroid is so loosely held together that it breaks up, there is no reason to expect any significant amount of large debris to continue on a collision course. You can (and surely would) use several nukes, where you can start with one far off and see what it does, then move in. Substantial fragments can easily be further deflected by additional blasts. Small fragments are not going to do much damage. We have nukes. We have the systems to get them there. It’s late. I’m done here. Allan Walstad(Quote)
John A. Fleming says:
Allan Walstad:
Umm, not quite. Nudging an asteroid out of harm’s way is done by applying delta-vee parallel to its velocity vector. It takes much more energy to change the orbit plane. It takes much less energy to hurry or retard an object along its current path, so that it just misses our Earth with acceptable probability.
Here’s the scenario. We set up in trail, just behind the asteroid, and blow the nuke, to nudge the asteroid with an additional 1 mm/s of velocity. Unfortunately, small asteroids are not spherical, so some of the vaporization and outgassing caused by the baryon, lepton, and photon radiation does not go into along-track delta-vee. Instead, it goes into cross-track delta-vee and rotation changes. In addition, the outgassing is not instantaneous. Instead, it starts out small, quickly rises, and then decays over some minutes, depending on composition. Hence my statement still stands: it will take more nukes than you first think.
Another complication: we don’t want the asteroid to prematurely break up, so the first nuke will be relatively distant, so that we can calibrate the effect. That means a companion satellite to observe from a safe distance.
Hopefully by now you’re realizing we won’t be sending a single spacecraft, but a flotilla, spaced at regular intervals. We have a saying in the space business: you can have a spacecraft fast, cheap, or reliable. Pick only two. If we have to move an asteroid, it’s going to be a bloody expensive and difficult campaign no matter the delta-vee method. And that’s if we can keep at bay the pernicious meddling of all the planetery tinhorn wannabes and in-the-ways. It’s not the science, technology, and operational expertise that’s questionable: where are we going to get the leadership for such an enterprise? John A. Fleming(Quote)