New nuclear deflection simulations advance planetary defense against asteroids
llnl.gov
llnl.gov
Newton’s third law kicks in: as the asteroid ejects mass in one direction, the asteroid reacts by going the opposite way. So you have altered the orbital trajectory of the asteroid, averting disaster.
The whole approach is very sensitive to the detonation height, asteroid composition and color, rotational characteristics, etc. So Burkey’s group has really made a simulation framework for modeling the right thing to do for a given asteroid.
An asteroid is not like that, even when heating one side with a nuclear bomb. The goal is to create a tiny change in its velocity vector, which still adds up to a significant trajectory change over time.
I'm looking up 'Conservation of momentum': https://www.physicsclassroom.com/class/momentum/Lesson-2/Mom...
> For a collision occurring between object 1 and object 2 in an isolated system, the total momentum of the two objects before the collision is equal to the total momentum of the two objects after the collision. That is, the momentum lost by object 1 is equal to the momentum gained by object 2.
but this seems to support what I say - there is no collision occurring in a vacuum. What is the expelled air colliding with?
Hope that makes sense
And just as an aside, IIRC conservation of momentum only applies to your standard physics objects, real objects make noises and sometimes permanently deform. This isn't usually a significant source of error but its neat to think about how if you were playing pool on a frictionless physics surface the difference between the models predictions of where the balls go and where they actually go (very very small difference) could be directly and perhaps entirely attributed to the noise they made on collision.
In a perfectly elastic collision, both momentum and kinetic energy are conserved.
As you say, many real collisions are inelastic to a significant degree. In these cases, momentum is still conserved, but the kinetic energy is converted to another form of energy.
Conservation of linear and angular momentum are fundamental and exact laws of nature resulting from translational and rotational invariance.
Conservation of energy always holds, whereas conservation of momentum has several important caveats and exceptions. Seemed worth pointing that out with an anecdote that amused me.
Hmmmm, actually can you explain a little more about 'momentum is still conserved'? In the cases that I'm pointing out momentum as a measurable property seems clearly not conserved, whereas the energy is (just transformed).
Also most of the surface on earth is water. And one big impact would create a mega tsunami. And that is magnitudes worse, than many small impacts, where the waves will then even partly cancel each other out.
So obviously deflecting is the prefered solution - but breaking up as much as possible will always result in way less damage overall to the planet - but the more impacts you have, the more likely it is, that they will also hit densly populated areas. So this decision will be highly political, as if something goes wrong and for example china gets mainly hit - the final outcome might be worse.
And the scenario in my head was many impacts in a close area - and the resulting waves then interacting with each other with turbulence.
In the near future, an unknown agent causes the Moon to shatter. As the pieces begin to collide with one another, astronomer and science popularizer "Doc" Dubois Harris calculates that Moon fragments will begin entering Earth's atmosphere, forming a white sky and blanketing the Earth within two years with what he calls a "Hard Rain" of bolides, causing the atmosphere to heat to incandescence and the oceans to boil away, rendering Earth uninhabitable for thousands of years.
If you blow up something that you're pretty sure is going to hit the earth a few orbits in the future, the bits are going to have diverse paths and hopefully many will miss or at least arrive farther in time.
On the other hand, if it happened close enough to Earth that all the little pieces, even if very tiny individually, still fall into the atmosphere, their evaporation friction would roast our world's surface for minutes to hours, terribly, causing global extinctions despite there never having been a single major impact at all.
The movie Deep Impact badly fucks that last scenario up near its end when humanity is saved by the main asteroid being completely blown apart just hours away from impact with the Earth. In reality, there'd have been no literal deep impact, but the'yd have all died anyhow, literally baked to death along with every other flammable thing on the earth's surface.
And don't forget that most asteroids are spinning over its own center-of-mass. The thrust generated by evaporating rocks on one of its sides will be changing direction as the asteroid spins around. Think of a rocket with thrust but no stabilization. Cool idea but very hard to make practical.
Also at least we cant have a ice-ball earth due to impact-winter.https://en.wikipedia.org/wiki/Snowball_Earth
Two approaches to getting that number...
https://www.wolframalpha.com/input?i=diameter+of+earth+%2F+%...
https://www.wolframalpha.com/input?i=%28430+seconds+*+earth+...
Granted, you'd probably like more than a diameter... but we're talking about it getting there a few minutes faster and it would be a miss.
In contrast, the vast majority of possible nudges will be neutral or beneficial, since the Earth is a very small target compared to the rest of space.
Given that the asteroid was heading directly at Earth prior to disruption, wouldn't any change in trajectory be welcome, even if it's chaotic?
It sounds a bit more precise to execute than the nuclear detonation, but it also sounds like you would have much better control over it this way than with nuclear detonation?
- Huge amounts of thrust required = likely multiple rocket engines
- That means huge amounts of mass and equipment
- Then the huge amounts of fuel required for all of those
Meanwhile with the nuke you can get away with much lower mass and "just" have to worry about making the bombs and detonating them at the right distance.
We invented nukes before we went to the moon, after all.
Of course as you say, if the nukes do it even cheaper, makes sense. Perhaps a bit risky to be launching them though! (sensible risk for a sure-hit asteroid, not for deflecting low-probability ones)
Of all the approaches I've read about the coolest in my mind is to paint a large part of the asteroid surface with high-albedo paint, thus using Yarkovsky effect to alter the orbit. This however requires a lot of paint!
However, I don't think you need vanta-black for this. You hit diminishing returns on a thing like this; so something like common soot would do just fine.
Most asteroids are rather dark, though.
To have enough of an effect, you have to do your thing while it's quite a ways away.
That means you have to go pretty fast to get out to it before it gets too close to you.
You can blow up a bomb while the ship has a large difference in velocity with the asteroid.
You cannot attach a rocket engine when you're traveling 1000m/s past what you're trying to attach it to.
So if you take Earth to be your stationary velocity, you need to slow down, stop, and accelerate backwards to catch up to the asteroid's velocity.
Acceleration/deceleration requires fuel, or specifically mass.
More mass at the same acceleration requires even more fuel.
So either you send up a bomb to hit the asteroid with a glancing blow, or you launch a very complicated bit of machinery atop a very very large ship, have it do its delta-V stuff, delicately land on the surface, not so delicately drill in and and anchor to an unpredictable surface, and then start burning the even more fuel that you carried along (at a cost of yet more fuel). All while hoping desperately that no bit of sand or gravel gets into something and sticks it in place while setting things up.
I'm liking the bomb approach. I imagine you'd even make use of the speed of impact rather than paying for it. You're essentially installing a rocket engine on the asteroid this way anyway, using its mass as propulsion mass, and you can even send up multiple redundant attempts because you've supposedly calculated the trajectory so precisely that it's enough to add some force in pretty much any direction. (Or the rest of the swarm could disarm themselves when they detect the first successful hit.)
This idea is using incoming photons to heat the body to the point where it vaporizes part of the surface. The emitted atoms have momentum.
"Clearly" their "bother" to develop simulations and conclusions is 100% downstream from government funding to make interesting noise. That doesn't mean that they are wrong. What it does mean is that its nonsense to couch a counter-argument to criticsim in an appeal to authority.
Because surely you have some kind of knowledge to draw on other than a gut feeling if you are going to say professional researches working in the field are wrong, no?
But in any case, the comparison with a hypersonic missile here can't be made:
1. hypersonic missiles have a guidance system, while asteroids do not. If an asteroid is moving in a certain direction, it will continue to do so until acted upon by an external force.
2. hypersonic missiles operate in the atmosphere, while asteroids do not. The speed of sound is entirely irrelevant to asteroids.
3. because of these two things, it is not hard to intercept an asteroid.
Given the difference in velocity (and F=mv^2), it may even be possible to deflect an asteroid by impacting it with an inert lump. This was actually tested in the DART mission[1], where a 610kg object impacted an asteroid at 6km/s and significantly changed its orbit.
[1]: https://en.wikipedia.org/wiki/Double_Asteroid_Redirection_Te...
Recommendation: The Expanse (TV)
Suppose over one second you can be hit the earth with with either 1 30 gigaton weapon, 3 10 gigaton nuclear bombs. 3,000 100MT weapons, or 3 million 10 KT weapons etc. All of those suck in ways that are hard to comprehend.
Hmm - I guess not! According to [1] it would take less then a ton of TNT to accelerate 1 million tonnes (eg like asteroid 12932-zephyr) to 0.1 m/s...So its probably a good thing I'm not responsible for these things!
Thanks to everyone for their help!
Presumably that depends a lot on the composition of the asteroid, e.g. whether it is mostly metallic or a pile of loose rubble.
Normally when a single bit of sand hits the atmosphere it dissipates energy in every direction. So you a tiny fast moving glowing dot radiating energy in every direction. However you can’t dissipate energy when you’re right next to another particle at the same temperature. Thus energy from each bit of sad can basically only go in 2 directions down or up and you’re not transferring energy through the entire thing before a crust of plasma followed by ~10km wide ball of sand hits the surface.
Hell it could be a ball of water that size and the same basic effect kicks in.
Spread a 10km wide ball of material into a 1,000 km wide diffuse cloud and you are basically slapping the earth with 1,000 km wide disk with an average width of ~17 cm (maximum width ~1m) going 10’s of thousands of km/h. Again things don’t go well, you may be shifting how many minutes various people survive but it’s not actually addressing the issue.
Energy.
A large enough meteor impacting the Earth at speeds high enough to cause an extinction-level event has a lot of kinetic energy.
Intuitively it seems like the troublesome part is the meteor hitting the Earth and causing earthquakes, tsunamis, and clouds of ash and debris as a result. And those things are really bad. But they’re a consequence of that mountain of kinetic energy.
So you break the asteroid up into a cloud of dust. Fantastic! No more crater, no more big boom. But you still have a giant ball of kinetic energy headed right at you, and that energy is just going to dump into the atmosphere. And boil it.
Of course that’s even assuming we totally vaporize the thing. More likely is instead of one multi-mile asteroid we have a bunch of giant chunks that will spread death and destruction all across the side of the planet unlucky enough to be facing it… before boiling the atmosphere anyway.
P.S. I you fragmented an asteriod - would at least _some_ of the pieces tend to change heading/speed enough so they miss earth?
That's how you turn a fission bomb into a fusion bomb. If you just put LiD in a fission bomb, it doesn't squeeze hard enough. If you focus the x-rays from a fission bomb onto an ablation drive, it does squeeze hard enough and you 1000x+ the yield with fusion. Which is why fusion bombs look like metal peanuts.
Conveniently, this means we are also really good at designing x-ray reflectors and lenses that focus the primary output of a nuclear bomb for the purposes of building ablation drives. Depending on just how good, we could probably persuade an asteroid pusher to be far more unidirectional than one typically pictures from a "bomb," if we set it off some distance away and focused the x-rays in the direction of the asteroid.
Far away in time doesn’t even need to mean far away in space, since many of the objects of concern are orbiting the Sun along with us. They may even have multiple close passes before being perturbed enough to become a threat.
Also, the masses involved don’t have to be huge. Two rocks intersecting in space are likely to be doing so with very different velocities. Kinetic energy is mass times velocity squared, so velocity rapidly overtakes mass as the dominant factor.
For comparison the asteroid that killed the dinosaurs was 10 to 15 kilometers wide. Since volume goes with the cube of the diameter, it follows that that asteroid was about one million times larger than the asteroids being studied here. The largest nuke ever tested was 50 MT, and the Soviets intentionally dialed it down from its designed 100 MT yield. Even that one would have been just a pinprick for the dinosaur-killer asteroid.
Sounds similar to the ablation ("outwards firing rocket engine") theory for how the secondary gets compressed in a thermonuclear bomb. Pretty cool.
There have already been papers on deflection via the ablation of an asteroid via nuclear detonation, so the idea is not new. However, it looks like with the knowledge gained with the DART mission this research will enable better modeling.
Putting Deuterium and Tritium (well, LiD which becomes D+T) in the middle of a fission bomb doesn't squeeze it hard/long enough to boost the yield of the fission bomb 1000x. Focusing the x-rays from a fission bomb onto a uranium "pusher" and driving it forward with the reaction force of vaporizing uranium does squeeze hard enough to generate fusion yield far in excess of the fission primary.
If this sounds vaguely familiar, you might be thinking of the Hohlraum at the NIF that recently made the press for getting more energy out than was deposited in. That strategy doesn't scale into a power plant but it does a brilliant job of simulating fusion bombs, which is why the DOE / NNSA can pursue it with so much money.
But right now we have exactly zero such devices prepared. Existing nuclear devices are about 3 orders of magnitude too small, and none of them are set up for a launch into an intercept. That's where the focus should be -- getting something, anything, of roughly the right order of magnitude that would provide a credible response to a detected inbound asteroid.
Who would build/host/control such a weapon?
Extrapolating from the existing high-yield bombs, the mass of a 1-gigaton warhead could be something like 200 tons. The Starship would probably be large enough to launch it into orbit, if you integrate the warhead in the upper stage and discard the lower stage. Then you would need 10+ refueling flights before you can launch it towards the asteroid.
A 10-gigaton bomb would need a rocket 10x bigger than the Starship. Or you would have to build it in the orbit.
Extrapolating from that a 10 Gt device should weigh around negative 25 thousand tons.
You wouldn't need the starship to launch it, just attach it to the HMS Invincible and it would spontaneously float upwards into space.
I'm not sure sure about that. With orbital dynamics being complicated, I'm pretty sure you want to push it to a known orbit. Otherwise, it might hit a body (planet/moon/asteroid) we have some base/colony on by that time.
Or it will hit Earth in it's next orbit.
If that's the scale required, I propose ignoring the possibility.
The most dangerous nukes are actually the smallest, since politicians may convince themselves that just a few small nukes is permissible, resulting in a rapid escalation that sees every major city showered with megaton h-bombs, destroying civilization and sending humanity into a poisoned dark age.
If it seems implausible that politicians might use tactical nukes, ask what those nukes were created for. The US made many thousands of them to be used against a conventional Soviet ground invasion of West Germany; lobbing small nukes at tank columns. Escalation from a conventional war to a nuclear war was a common assumption in the military planning of the late cold war. But sides anticipated it and were prepared to perform that escalation themselves.
It's not easy, but it's something like a 3-4 order of magnitude multiplier if you figure out how to do it.
In fact I believe that anything over the low tens of Mt is considered impractical for military use.
Agreed, a big device doesn't really alter the balance of power, which is why both the Americans and Soviets abandoned the path of bigger and bigger devices by 1962, leaving lots of engineering possibilities on the table to instead focus on miniaturization.
Unless of course you don't deflect it but break it up into chunks where some of the chunks are still heading towards us.
Oh, lets just glass a side of the moon like a fresnel and zap the asteroids like an ant under a magnifying glass. I call it project Disco Moon
There are two goals with this: (1) break down or deflect any large chunks to prevent damage related to ground impacts. (2) cause enough change to the orbits of the asteroid remnants such that any subsequent collision with earth would be spread out over time to prevent overheating of the atmosphere via clouds of debris.
The best solution is always to have the asteroid remain as intact as possible, but for certain asteroid types and scenarios, it may just have to be good enough especially as a backup.
If you had to design a really big ablation drive to push a really big asteroid, who would you call? Prof. Ablation Drive? Or some other guy? (Yeah, he's not with us anymore, but you know what I mean.)
After energy, material will be the most pressing issue.
Even if we found a favorable candidate it'd still be the difference between shooting at a mortar shell to change the direction away from you to avoid the shell hitting you, and shooting at the shell to get the shell to pass close to you. The later action has a much worse risk profile.
https://iopscience.iop.org/journal/2632-3338
It is nice to see new fields of science, it shows the scale of where science could go.
Their answer shocked me: They are already tracking an asteroid big enough to destroy an areas the size of Texas, that WILL hit Earth in about 140 years.
Equally as shocking: we will need to launch our planetary defense solution with 30-40 years lead time to deflect the asteroid in time.
Also: likely they were talking about Bennu[0], which is about 500m in diameter and is frequently quoted as devastating an area the size of Texas.
There is no such thing. 101955 BENNU currently tops the special risk-list of potentially dangerous asteroids, with the latest estimate giving an impact probability of 0.037% in the year 2182. The only other candidate on that list has a probability that is even lower and and a timeframe of many centuries.
If Russia/China/US/France/... want to do a test, they do it. There is nothing to negotiate and no one to beg for permission.
France did nuclear tests in 1996 despite massive international outrage and pressure.
The only countries truly capable of something like this within the next couple of decades would be the US or China anyway. So only their opinion really matters and both of them would likely just complain for appearances but not actually seriously oppose the action.
Anyone else doing the complaining is just looking for any excuse to pull out of the test ban treaty and should just be threatened with heavy sanctions if they do (as they would, even without a dangerous asteroid bearing down on Earth).
https://blog.nuclearsecrecy.com/2012/09/12/in-search-of-a-bi...
(Edit: although this is very unlikely, I guess)
Actually, what are the chances of this system – if it existed – is used to move an asteroid into the path of the Earth and killing everybody within the next 100 years? (This would include scenarios like "the US president or industrialist who builds it randomly goes insane"). 1%? 0.1%? If the risk of an asteroid hitting the earth is lower than that we should clearly not build such capability.
Also such systems and missions are the results of thousands of people working together not the pres pulling up a web interface and clippy asking "So it looks like you'd like to deflect an asteroid today!" Much like jump starting the apocalypse with global nuclear war can't be effected by pressing a red button somewhere.
She started with something like “That was cute, wasn’t it? I am going to talk about our simulation of every photon during a nuclear detonation.” It was awesome.
More seriously, interestingly, those analysis would require early detection and therefore investments on such approach, which might not be always the case. The article was interesting and I hope we won't be prototyping soon.
We all know that, long term, earth's biosphere is doomed (for human habitation) and the goal is to start over with a terraformed Blue Mars. Of course.
So projects like nuking our moon are a wonderful way to start practicing those bigger-picture geo-engineering projects without ... you know ... practicing on this little oxygen-rich wet rock we're all presently tethered to.
If we had the capability of terraforming Mars, it would be trivial to fix climate change here on Earth.
Then we can use the energy from relocating the Moon to correct the earth's axial tilt.
I've got a plan in motion: https://snafuhall.com/p/earthwrap.html
love it
How much of that vector got reduced when operating in near vacuum?
So it becomes more a game on how fragmented the asteroid can become upon a nuclear detonation ... in near-vacuum condition.
The largest deployed US weapon was the B41 with a yield of at least 25MT. The closest contemporary is the B83 at 1.2MT.
https://www.indiegogo.com/projects/help-defend-earth-against...
https://www.nasa.gov/general/an-innovative-solution-to-nasas...
https://en.wikipedia.org/wiki/Partial_Nuclear_Test_Ban_Treat...
Mission Focus Areas
Crafting broad-ranging solutions with immediate impact.
Might want to have the PR dept take a look at that wording.
We also aren't liable to experiment on any mountain sized rocks and accidentally steer it into our path. We can absolutely experiment with manageable sized rocks. The only meaningful risk other than wasting our money is dealing with something that is within the margin of error and turning a near miss into a hit.
As this risk is inherently a small subset of the probable hits its hard to imagine how this risk could possibly be larger than its superset.
The remaining risk would be in an accident during a test run involving a live nuke. It's not obvious that such a test would be advantageous to conduct on balance nor needed.
If your civilization is technically advanced enough to be a potential threat to such an actor, the highly energetic actions you are undertaking for interstellar travel will be visible to all of space via radio and infrared telescopes. Given that it will be economically infeasible to launch all of the payloads required to produce interstellar spaceships from within the gravity well of a planet, the orbital infrastructure required itself will lkely be visible as a periodic dimming of the planet's sun. It too, will give off infrared radiation detectable by a far-off technically advanced malignant actor.
There is no hiding in space. Your only hope for species and evolutionary survival in a dark forest is to aggressively disperse to uninhabited target systems. However, this also increases the likelihood that one of those systems will go rogue and eliminate the other ones it knows about.
Given this, the best strategy seems to be first avoidance of contact, then diplomacy, then detente, and finally alliance and assimilation in a Dark Forest universe. The allied powers can ensure that any bad actors that attempt elimination strikes are outnumbered and eliminated themselves.
On top of that, space is infinitely large. There are an enormous amount of finite resources within a planetary solar system which are way more energetically economic to exploit than ones in other systems. Once a civilization is forced to expand for survival beyond its local system, it is likewise economically cheaper to avoid warfare to claim one particular planetary system for its resources than to fight an interstellar war that risks the annihilation of the conflict participants' civilizations. There are literally an infinite number of systems to choose from.
There's no reason to destroy other competitors when the resources you are competing for are infinite. In such a scenario, which our universe seems to be an example, the only reason for conflict is malignant choice.
The prisoner's dilemma between two or more civilizations presented in the series would never need to occur.
The philosophy behind Three Body is just terribly cynical and illogical in the face of what we know of the existing universe. It makes for a great story, but the type of aggression posited in technical species doesn't provide an evolutionary advantage.
It should be noted that the entire Dark Forest philosophy presented in the book came from an unstable, traumatized, suicidal, xenophobic, nihilistic genius. Not the sort of person who you want forming the zeitgeist for existing in a much larger ecosystem of other civilizations.
If you accept the premise, then the series is great. But the premise assumptions are fundamentally flawed.
(I work on asteroid detection for planetary defense professionally)
Cool. I am a software engineer with nearly 40 years professional experience. I wondered if volunteering to work on an open source software related to planetary defense might be an interesting retirement project.
I think the best we can hope for (apart from not having an asteroid heading our way at all) is that we'll have sufficient notice that something can be done. If we had a couple of years notice, there's a reasonable chance the deadline would be motivation enough to get something built.