11 ms·
So, this research is extremely cool. The way nuclear deflection works is not how you think. You probably don’t blast the rock to bits. Instead, Burkey’s model u
by spenczar5 3y ago
So, this research is extremely cool. The way nuclear deflection works is not how you think. You probably don’t blast the rock to bits. Instead, Burkey’s model uses a bomb tunes to produce a crazy amount of x-ray radiation which heats up one side of the asteroid. You heat it up so much that the rock liquifies, then bubbles, and outgasses - and forms a propulsive engine, right on the surface, shooting out gaseous ultra-hot rock.
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.
- noman-land 3y agoHow do you prevent the asteroid from flying erratically like a balloon with the air rushing out?
- wcoenen 3y agoA balloon does that because it has very low mass and moment of inertia, compared to the thrust provided by the escaping air. 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.
- jonplackett 3y agoIf on the other hand it IS balloon-like and hollow then let’s just let it crash into earth and pop.
- peteradio 3y agoIndeed, perhaps there will be some way to detect latex based asteroids in the future and avoid any unnecessary nuclear deployment.
- deleted 3y ago[deleted]
- dylan604 3y agoWe just need to build a spaced based array of microphones (comsaphones???) to listen for the high pitched squeal or the pfffft sounds as the air is rushing out the opening.
- hermitcrab 3y agoIn a vacuum?
- dylan604 3y agoReally? C'mon. Walk this thread back up, and see if you can find where it went off the reality rails. Then, see if your comment fits with the seriousness of the thread.
- hermitcrab 3y agoI prefer humour to be based on plausible physics. ;0P
- dylan604 3y agothank goodness you're not the one in charge of comedy for the rest of us
- peteradio 3y agoYa if you go up a few I see it really goes off the rails here: https://news.ycombinator.com/item?id=38722192 https://news.ycombinator.com/item?id=38722192
- dylan604 3y agoso a latex asteroid is an acceptable concept in your world? or was the humor in it too witty for you to grasp?
- reed1234 3y agoMy guess is the jet doesn’t last that long
- XorNot 3y agoYou don't - but it doesn't apply. The size of the "engine" compared to the mass of the asteroid is enormous. A balloon has a relatively large engine compared to it's mass, and the engine is flexible - i.e. if you stiffened where the air comes out, the balloon would fly much more predictably.
- southernplaces7 3y agowell, because an average asteroid in the solar system is nothing at all like a balloon. Or maybe you're confusing comets and asteroids, though it doesn't matter anyhow because your notion doesn't apply in either case and I can't at all see why it should.
- verisimi 3y agoI don't think a balloon would fly erratically if the air was released in space or a vacuum. As far as I can understand it, the air would rush to equilibrium in all directions - the balloon would deflate rapidly - but the air 'movement' would not move the balloon, as in a vacuum there is nothing to push against. Any erratic movement would be due to the elastic of the balloon returning to its resting state. I think you would also get movement in earth based vacuum chambers due to gravity.
- dumah 3y agoThe air doesn’t need anything “else” to push against. It pushes against itself and the balloon. Conservation of momentum will cause propulsion.
- verisimi 3y agoThank you. I'm looking up 'Conservation of momentum': https://www.physicsclassroom.com/class/momentum/Lesson-2/Momentum-Conservation-Principle 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?
- alach11 3y agoImagine your sitting on a office chair with wheels. If you're holding a large weight and suddenly throw it forward, the chair will roll backwards. This would happen in a vacuum too.
- verisimi 3y agoThis is a nice way to express it, imo. I also think it's possible to interpret what happens differently. A balloon or something in space doesn't have anything to move against, whereas the chair's wheels are on the floor. When you move the weight in an environment without anything to respond to, ie in suspension in a vacuum, there is no opposite to respond or work against. Both seem possible to me - that a chair+person-with-weight is capable of generating it's own momentum and that nothing happens in space, in a vacuum.
- spywaregorilla 3y agohypothetically, even if this is how it worked, that would still be fine, because literally any direction other than the one directly targeting the earth is going to be a non issue. the probability of randomly nudging and hitting anything of consequence is basically zero.
- luqtas 3y agodon't forget our moon, too
- spywaregorilla 3y agoprobability of hitting the moon with a random velocity in space is comfortably roundable to 0% provided you randomize decently far awaay
- luqtas 3y agoso as the occurrence of life *-*
- ClumsyPilot 3y agoDo you own real-estate on the moon?
- hnburnsy 3y agoRead Seven Eves, we dont want a crumbling moon raining down on the earth.
- hnburnsy 3y agoDo we actively track that now?
- wkat4242 3y agoYeah blowing it to bits sounds like the worst thing to do. It's like turning a bullet into a shotgun blast.
- Cthulhu_ 3y agoWhich might be fine if the bits are small enough that they would burn up in the atmosphere, but that's making a lot of assumptions.
- hutzlibu 3y agoWell, but the basic assumption is, the more surface of the asteroid is exposed, the more will burn up in the sky. And that is pretty solid physic and should be valid. 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.
- OscarCunningham 3y agoWaves don't cancel out, they pass through each other.
- hutzlibu 3y agoOrdinary waves travelling through the ocean, mostly yes. But when 2 Tsunamis crash into each other, you can bet, that there is lots of turbulence and energy lost and they wont have the same height afterwards.
- OscarCunningham 3y ago
- lr1970 3y ago> 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. 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.
- jojobas 3y agoUnless it's spinning at 100rpm the rotation would have very little impact, the whole x-ray-heatup-boiloff cycle is under a second.
- sigmoid10 3y agoThe paper only simulated it up to 10 microseconds. But they also only used a simplified 2D toy model. They acknowledge that a realistic simulation will need to factor in a ton of other things, including rotation of the asteroid.
- hnuser123456 3y agoThe impacted side might outgas for years.
- picadores 3y agoEvery tumble has a "slow" pole, where the outgasing would form a vector, nearly almost away from earth. Also at least we cant have a ice-ball earth due to impact-winter.https://en.wikipedia.org/wiki/Snowball_Earth https://en.wikipedia.org/wiki/Snowball_Earth
- darkerside 3y agoSo if the universe threw a perfect spiral at us, we'd be fucked
- classified 3y agoThis is very reassuring. Because next time Bruce Willis won't be around to blast the asteroid to bits.
- AlgorithmicTime 3y ago[dead]
- Aardwolf 3y agoWould it then also work to fly a small rocket engine to the asteroid, attach to the asteroid, and turn on the engine to divert the asteroid? 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?
- vlovich123 3y agoProbably much harder to pull off + generate that thrust + carry enough fuel to generate that thrust for rocks > some small mass? Just guessing
- TheCapeGreek 3y agoI'd imagine it sounds simpler but is actually much harder. - 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.
- Aardwolf 3y agoI don't know, if maybe not that much thrust is required in some scenarios, perhaps a tiny alteration of course can already be enough to avoid hitting Earth 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)
- biomcgary 3y agoOr, combine the ideas Project Orion style (https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...)
- IlliOnato 3y agoThis is definitely one of the possible approaches, which is being studied too. As other commenters mentioned, this would be much harder technically and much more expensive than "nuking", but in some particular scenarios (I think when an asteroid is very loose and easy to break into large parts) this approach has some advantages. 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!
- kyleyeats 3y agoIt's the Yarkovsky effect: https://en.wikipedia.org/wiki/Yarkovsky_effect https://en.wikipedia.org/wiki/Yarkovsky_effect
- AnimalMuppet 3y agoIt's not the Yarkovsky effect. The Yarkovsky effect is where a body emits photons (which have momentum, and therefore change the momentum of the emitting body). 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.
- kyleyeats 3y agoSo you don't see any similarities?
- gosub100 3y agovery tangential similarity that photons have momentum, and so impart a force on massive object. But it's also confusing compared to this, because photons are heating the substance (which actually would impart an opposing momentum), to "boil" it, to use kinetic forces to push in the desired direction. I appreciate the link but I don't think the effects are that similar.
- kyleyeats 3y agoSo if an orbit brought an asteroid close enough to a star to have this effect on the surface of an asteroid, you would consider it an entirely different phenomenon?
- mc32 3y agoHow do they ensure the asteroid doesn’t rotate instead? Or maybe despite rotation enough energy is directed toward a deflection.
- ganzuul 3y agoIf it rotates it has has poles. Hit it from the pole and the entire thing is stabilized.
- nine_k 3y agoI suppose that making an impact may still make sense for larger and softer asteroids (not solid metal): a blast a few meters deep would evaporate and eject more matter than a surface blast.
- mrangle 3y agoGiven the speed of the rock, it's difficult to conceive of how this theoretical action would even marginally change the course of an asteroid large enough to be worried about. It'd be like blowing on a hypersonic missile that is larger than a building.
- pavel_lishin 3y agoIf you blow on that missile while it's far enough away, it'll deflect its course enough that by the time it would have hit, it'll miss.
- ac2u 3y agoIn the same way that when you point a laserpen at the night sky, and then twist your wrist ever so slightly to the right, it's now pointing at another point 1000s of lightyears from the first. As long as you attempt the procedure early enough you have a chance.
- mrangle 3y agoI get space. What I'm saying is that, assuming we can even hit it, any such rock is moving with too much momentum to be able to change its course. Given any tech that we have. It's easy to underestimate the energy represented by a large asteroid.
- ac2u 3y agoMy understanding is that it's nothing to do with momentum and everything to do with mass.
- hermitcrab 3y agomomentum = mass x velocity
- ac2u 3y agosure but what has momentum got to do with adjusting the trajectory in this situation?
- mech422 3y agoI don't understand the whole 'we don't want to break up a loose conglomeration of rock'. I'd actually think breaking an asteroid up into multiple pieces that can be 'eaten' by the atmosphere would be easier/safer? The atmosphere does a good job of destroying smaller stuff. Breaking stuff up and letting it burn up seems much more feasible then trying to calculate the exact method to hit an asteroid without fragmenting it and still generate outgassing/thrust ?
- hermitcrab 3y agoI guess it depends on how big the pieces are. If you break a very large asteroid in 3, still large, pieces that might not be an improvement. A nuclear weapon exploding in a vaccum is likely to be a lot less destructive than one exploding in the atmosphere.
- Retric 3y agoEnough energy is going to be dumped into the atmosphere either way it doesn’t make much difference. Further, even fist sized fragments are going to penetrate deep into the atmosphere so all options are effectively ground level detonations. 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.
- mech422 3y agoGiven multi-kilometer asteroids like mentioned above, I'm starting to think neither method (fragment/push) sounds viable. The amounts of energy required just seem off the scale? Maybe pushing (multiple?) smaller but still massive enough to have decent kinetic energy into its path would be more feasible. Sorta like pool balls bouncing off each other..I generally end up missing the pocket (earth) when that happens :-)
- Retric 3y agoThe trick is early interception. Push something 10 years early and 0.1 m/s = ~30,000 km. Wait until 1 month out and you need to shove it 100x as fast.
- credit_guy 3y agoJust to set the expectations: the size of the asteroids they considered was around 100 to 200 meters. The nuke they envisioned was a 1 megaton one, which is basically the yield of the largest active nuke in the US inventory (B83 = 1.2 megatons). 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.
- ipdashc 3y ago> Instead, Burkey’s model uses a bomb tunes to produce a crazy amount of x-ray radiation which heats up one side of the asteroid. You heat it up so much that the rock liquifies, then bubbles, and outgasses - and forms a propulsive engine, right on the surface, shooting out gaseous ultra-hot rock. Sounds similar to the ablation ("outwards firing rocket engine") theory for how the secondary gets compressed in a thermonuclear bomb. Pretty cool.