[HN Gopher] New nuclear deflection simulations advance planetary... ___________________________________________________________________ New nuclear deflection simulations advance planetary defense against asteroids Author : ulrischa Score : 212 points Date : 2023-12-21 07:42 UTC (15 hours ago) (HTM) web link (www.llnl.gov) (TXT) w3m dump (www.llnl.gov) | mnky9800n wrote: | Well that seems like a fun job. | keyle wrote: | I was just thinking the same! Shooting rocks in space! If only | someone made a game about this, 44 years ago :) | Semaphor wrote: | And the picture is a woman looking very pleased and "yes, I | always wanted to throw nuclear bombs at asteroids, and there's | nothing you can do about it!" :D | spenczar5 wrote: | I was at the Planetary Defense Conference when Dr Burkey | presented this work. The previous talk had been on a detailed | hydrodynamics simulation which measured characteristics of | rubble-pile asteroids, run on a supercomputer. | | 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. | Vecr wrote: | I think one of the most important tasks for planetary defense is | detecting comets and asteroids early. That's why I think | continued funding of the SpaceX ultra-heavy lift booster is a | good idea, not for any reason related to the moon or mars, but | for the ability to ride-share cheaper and heavier space-based | survey telescopes. | spenczar5 wrote: | Honestly, with LSST coming online in the next few months, and | NEO Surveyor on the way in the next decade, I think we are | pretty set already for observational instruments. The big gap | that I see is in software. | | (I work on asteroid detection for planetary defense | professionally) | 93po wrote: | We've seemingly looked at so little of the universe though? | Wouldn't more instruments be a good thing? | preisschild wrote: | Time to unpack Gnomon and Sundial (10 Gigatons of TNT equivalent) | the8472 wrote: | Those are cooler in allcaps. | sgt101 wrote: | If I were scratching up a way of doing this I think I would | rather have 500 or 1000 smaller devices to use... | arethuza wrote: | A Gnomon device would probably be a few hundred tons and a | Sundial a few thousand tons - hence the delivery mechanism for | the latter on Teller's blackboard apparently being "backyard": | | https://blog.nuclearsecrecy.com/2012/09/12/in-search-of-a-bi... | HPsquared wrote: | All well and good until a Bond villain gets control of the | system. | | (Edit: although this is very unlikely, I guess) | M95D wrote: | Unlikely like the uranium centrifuges in Iran? | Aransentin wrote: | > very unlikely | | 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. | HPsquared wrote: | As long as it's possible, the insane ones might do it. We | cannot allow an asteroid gap! | totally_human wrote: | I imagine it would be possible to construct the system to | substantially reduce the risk, even reduce it to "cosmic rays | cause bit-flips which launch nukes" levels of risk. It's not | like military nuclear command-and-control, you don't need one | person who can push the button at any time. If we spot an | asteroid, we'll have some time to deal with it. The system | would presumably need to be constructed, which would take a | few days even if everything was in storage on standby. Then, | to activate it, you could have something like the US nuclear | weapons' PAL, but instead of the codes being in the hands of | one person, you spread them out. Just before launch it's | activated with something analogous to the ICANN key ceremony: | a bunch of well-regarded astronomers, rocket scientists, and | aerospace engineers use their section of the Earth Asteroid | Defence Key, and they press the metaphorical button together. | skeaker wrote: | A system like this would require so many people at each step | that I don't think one insane actor could do something like | this even if they were the president. | michaelmrose wrote: | It's not obvious that such a system would be useful for that | at all. The effects on the trajectory would be hard to | predict. It would be useful at all because any meaningful | change in trajectory hundreds of millions of miles away from | impact results in a miss. | | 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. | picadores wrote: | He who resides above us in station, beyond the gravity well, we | shall hail a god. Hail Armstrong, mighty wielder of tungsten | rod and rock! We praise you and tremble in thy shadow every 90 | minutes. | ganzuul wrote: | Non-nuclear hafnium isotopes could make for a much cooler gamma | ray laser. | | https://en.wikipedia.org/wiki/Hafnium_controversy | zucker42 wrote: | The yearly odds of a "Bond villian" becoming U.S. president | seem a lot higher than the risk of a catastrophic asteroid to | me. | nicoboo wrote: | We all have the biggest movie in mind and we know the unfortunate | situation our heroe is facing right now, makes us all doomed. | | 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. | neonsunset wrote: | Huh, why is there a technology unlock message from Stellaris in | my HN feed? :) | iAMkenough wrote: | Like some defense projects, I predict we'll outsource it to a | private party, pay them public tax subsidies, and fail to hold | them accountable when they go against our public defense | interests. | M95D wrote: | In case of an asteroid, our interests are also theirs. OK, | let's say they go against our interests. What are they going to | do next? Move to Mars?? | bratbag wrote: | Their interest is to convince themselves that it won't be | needed in their lifetime, and to hell with anyone else after | they are dead. | leoedin wrote: | This seems like the biggest failure point. Humans are | basically unable to prepare for major but rare events (eg | the pandemic response). Day to day politicing always wins, | and when the problem is suddenly on top of us we've got | nothing. | | 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. | spenczar5 wrote: | 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 wrote: | How do you prevent the asteroid from flying erratically like a | balloon with the air rushing out? | wcoenen wrote: | A 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 wrote: | If on the other hand it IS balloon-like and hollow then | let's just let it crash into earth and pop. | peteradio wrote: | Indeed, perhaps there will be some way to detect latex | based asteroids in the future and avoid any unnecessary | nuclear deployment. | dylan604 wrote: | We 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 wrote: | In a vacuum? | reed1234 wrote: | My guess is the jet doesn't last that long | XorNot wrote: | You 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 wrote: | well, 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 wrote: | I 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 wrote: | The air doesn't need anything "else" to push against. It | pushes against itself and the balloon. Conservation of | momentum will cause propulsion. | verisimi wrote: | Thank you. | | I'm looking up 'Conservation of momentum': https://www.ph | ysicsclassroom.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? | spookie wrote: | Same way a rocket does. That is, don't treat it as if | there's a need for a second object. The release of air is | applying a force in whatever the balloon still has in the | direction of travel, even though it's going on the other | direction. | | Hope that makes sense | cmrx64 wrote: | The air molecule collided with the inside of the balloon, | and escaped out the opening. | spookie wrote: | Your explanation is much clearer than what I said, so | yeah, this | burnished wrote: | You can also see this by using newton's third law (equal | and opposite reactions). The air is accelerating and the | only other thing for it to act on is the balloon in equal | and opposite fashion. | | 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. | alach11 wrote: | Imagine 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. | spywaregorilla wrote: | hypothetically, 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 wrote: | don't forget our moon, too | spywaregorilla wrote: | probability of hitting the moon with a random velocity in | space is comfortably roundable to 0% provided you | randomize decently far awaay | luqtas wrote: | so as the occurrence of life *-* | ClumsyPilot wrote: | Do you own real-estate on the moon? | wkat4242 wrote: | Yeah blowing it to bits sounds like the worst thing to do. It's | like turning a bullet into a shotgun blast. | Cthulhu_ wrote: | Which 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 wrote: | Well, 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 wrote: | Waves don't cancel out, they pass through each other. | hutzlibu wrote: | Ordinary 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 wrote: | I think you're imagining two towering waves crashing into | each other. But in fact tsunamis only pile up like that | when they enter shallow water. In the open ocean a | tsunami is a wide area (~100km) of slightly raised (~1m) | water. If two overlapped it would just be raised twice as | high, which wouldn't cause much turbulence. | jasonwatkinspdx wrote: | Burning up in the atmosphere is still a concern. In the | Cretaceous-Paleogene, aka the day the dinosaurs died, most | of the damage was done by matter ejected on suborbital | trajectories by the impact falling back into and | superheating the atmosphere. | adolph wrote: | I wonder if Stevenson was thinking about that event when | writing Seveneves: | | _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._ | | https://en.wikipedia.org/wiki/Seveneves | sgt101 wrote: | I think that the bits hitting the atmosphere might heat the | planet up a large amount. This might be bad. | peteradio wrote: | Unless its really cold out then we might not mind the | extra heat. Depends if its summer or winter I suppose. | sgt101 wrote: | heh... you know I hadn't thought of that. | toast0 wrote: | Depends when you do it, I'd think. If it's on final approach, | yeah most of the bits still hit the earth, so maybe not | great. | | 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. | southernplaces7 wrote: | If the asteroid is far enough away, blowing it apart, even | partially, would change all trajectories to almost certainly | miss the absurdly tiny target that is the earth from a | distance of tens or hundreds of millions of miles away. | | 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. | lr1970 wrote: | > 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 wrote: | Unless it's spinning at 100rpm the rotation would have very | little impact, the whole x-ray-heatup-boiloff cycle is under | a second. | sigmoid10 wrote: | The 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 wrote: | The impacted side might outgas for years. | picadores wrote: | Every 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 | darkerside wrote: | So if the universe threw a perfect spiral at us, we'd be | fucked | s3rv3rsi7e wrote: | No because the vector can also change in magnitude. Even | if the spiral was perfectly aligned to impact the perfect | center of the Earth we could change the magnitude of the | object by nuking either pole to either slow it down or | speed it up. Enough energy on any pole could make it miss | regardless of the orientation. | jamesmontalvo3 wrote: | Perfectly chaotic rotation might be worse. If it was a | spiral then you could hit it at a pole. I think most | things rotate about a semi-fixed axis (not totally fixed, | often propagating over time) | shagie wrote: | If you can make the asteroid cross Earth's orbit 430 | seconds sooner _or later_ that 's an Earth diameter. | | Two approaches to getting that number... | | https://www.wolframalpha.com/input?i=diameter+of+earth+%2 | F+%... | | https://www.wolframalpha.com/input?i=%28430+seconds+*+ear | th+... | | 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. | cnlevy wrote: | In that case, detonate the bomb above its axis of rotation. | Unless the rotation axis is precessing as well... | sandworm101 wrote: | Given the dimensions involved, the billions of miles, _any_ | deflection would create a miss. If we are certain that an | asteroid is actually going to hit earth many years /decades | out, then even a microscopic nudge in any direction would | shift the closest approach by an earth-width. So precise aim | might not be as important as getting the bomb out there asap. | The earlier it is done, the less push is necessary to | generate a miss. Of course, this is premised on us having | near-perfect knowledge of the initial trajectory. | mrangle wrote: | Heaven forbid their calculations aren't confident given | that large distance, and the theoretical nudge instead | generates a hit. | j4yav wrote: | Why would we be nudging ones that are going to miss? | pdabbadabba wrote: | If we mistakenly think it will hit because "their | calculations aren't confident given that large distance." | Arrath wrote: | Presumably the same distance that gives the calculations | uncertainty allows time to adopt a wait and see approach, | refine the data and calculations and then make a decision | based off of stronger inputs and still avert disaster if | necessary? | Terr_ wrote: | A chilling tale, but step back and look at the odds: Not | only does it rely on a significant original | measurement/prediction error, but it also assumes _the | exact wrong nudge_ will occur that happens to compound | that error. | | 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. | rmbyrro wrote: | Detecting an asteroid years or decades in advance in the | first place would be an extremely difficult task, I | believe. | datameta wrote: | As I understand it we are tracking certain asteroids that | we predict have a chance of impacting on the following | encounter with earth depending on what the outcome is of | passing through a per-basis volume called a "keyhole". So | it isn't that we detect them when they are a decade out | on a direct trajectory. | throwaway4aday wrote: | Those are the ones we know about. If you think about the | problem, it really is a very difficult one to solve. | We're attempting to find and track tiny objects that | could be anywhere in an absolutely massive volume of | space using almost entirely ground based equipment that | is hobbled by competing demands, atmospheric distortion | and a very inconveniently nearby star that halves the | observation time and makes it really hard to find objects | on that side of our orbit. For all the fancy animated | maps of the many asteroids we have located there are | likely still a very large number of other asteroids we | don't know about yet and may not find out about until | after the fact. | MetaWhirledPeas wrote: | > Think of a rocket with thrust but no stabilization. Cool | idea but very hard to make practical. | | 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? | classified wrote: | This is very reassuring. Because next time Bruce Willis won't | be around to blast the asteroid to bits. | Aardwolf wrote: | Would 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 wrote: | Probably much harder to pull off + generate that thrust + | carry enough fuel to generate that thrust for rocks > some | small mass? Just guessing | TheCapeGreek wrote: | I'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 wrote: | I 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 wrote: | Or, combine the ideas Project Orion style (https://en.wikip | edia.org/wiki/Project_Orion_(nuclear_propuls...) | IlliOnato wrote: | This 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! | adolph wrote: | Could a similar effect be had by painting half asteroid | surface with a lower-than-surface-albedo material like | vanta-black? Not certain which would be harder.... | IlliOnato wrote: | I guess if an asteroid is has high albedo already, a dark | paint would be better for this purpose then dark. What | you want is to make sure that some parts reflect much | more light than other parts. | | 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. | swader999 wrote: | It depends, many asteroids are quite porous, maybe it would | burrow into or through it. | hermitcrab wrote: | An asteroid could weigh millions of tons. For even a tiny | deflection I think you would need quite a few tons of | propellant. It would be quite a challenge getting that onto | the surface of the asteroid. | kyleyeats wrote: | It's the Yarkovsky effect: | https://en.wikipedia.org/wiki/Yarkovsky_effect | AnimalMuppet wrote: | It'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 wrote: | So you don't see any similarities? | gosub100 wrote: | very 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 wrote: | So 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 wrote: | How do they ensure the asteroid doesn't rotate instead? Or | maybe despite rotation enough energy is directed toward a | deflection. | ganzuul wrote: | If it rotates it has has poles. Hit it from the pole and the | entire thing is stabilized. | nine_k wrote: | I 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 wrote: | Given 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 wrote: | If 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 wrote: | In 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 wrote: | I 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 wrote: | My understanding is that it's nothing to do with momentum | and everything to do with mass. | hermitcrab wrote: | momentum = mass x velocity | brokencode wrote: | How can you be so confidently wrong? Clearly researchers | at Lawrence Livermore think it's a viable approach, or | they wouldn't bother with developing detailed | simulations. Why do you think you know more than those | researchers? | alright2565 wrote: | I'd strongly suggest playing some KSP to get intuition about | orbital mechanics. A warning though: you'll never be able to | enjoy space movies and shows, since they almost never present | orbital mechanics correctly. | | 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_Redirectio | n_Te... | Mawr wrote: | > A warning though: you'll never be able to enjoy space | movies and shows, since they almost never present orbital | mechanics correctly. | | Recommendation: The Expanse (TV) | MeImCounting wrote: | Yeah the expanse gets plenty of the newtonian orbital | mechanics physics right but totally gloss over other | important parts of space travel such as: how do you deal | with the thermal buildup-space is a nearly perfect | insulator. Wheres the radiators? They are regularly | moving at speeds that would have a small but additive | relativistic effect. Wheres the belters/other spacers who | live several hundreds of earth years but not nearly as | many from their perspective. Not to mention the pure | impossibility of the Epstein drive. The Epstein drive is | probably the most glaring example of human clarketech in | the whole story. Anyways I love the Expanse but the books | were better anyway | mech422 wrote: | I 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 wrote: | I 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. | stouset wrote: | > I 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? | | 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. | kleene_op wrote: | Not only is it essential for the defense of our planet, but it | will be very important economically. Being able to capture | asteroids within the moon's orbit to be able to mine them will | propel humanity forward. | | After energy, material will be the most pressing issue. | jojobas wrote: | I'd say it's a far cry. Nudging an asteroid at 10m/s a couple | of months out might be enough to miss the Earth, to capture it | in a lunar orbit you need two orders of magnitude more at the | very least. | pavel_lishin wrote: | Couldn't you play some games with orbital mechanics, and use | the Earth-Moon system to capture the asteroid as it goes by? | You don't have to expend all the delta-v to move it into an | Earth or Moon orbit - you just have to put enough there to | aim it at one spot, and let gravity do the rest. | lolc wrote: | We want the damn things to pass by. If we try to capture | them we have to maneuver their trajectory very very close! | I have no idea of astrophysics but due to their high speed | the distance where they'd be in orbit would likely be below | the surface of the earth! The orbital speed at the earth's | surface is only 7.9 km/s[1] which is rather slow for an | asteroid this close to the sun. | | 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. | | [1] https://en.wikipedia.org/wiki/Orbital_speed | jojobas wrote: | That's not how it works. You may save some energy by | gravity assists, but you're not getting a factor of even | 10. | yyyfb wrote: | Could we use this against the moon to move our orbit around the | sun just a tad outwards, to counteract global warming effects | yyyfbisagenius1 wrote: | Excellent idea! | | 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. | yyyfbisagenius1 wrote: | Although, now that I think about it some more, you'd probably | want to be very certain of all the math before you turn a | nontrivial amount of the Moon's surface into liquid molten | rock belching out superheated gas. It would be a bummer if | you, for example, were to accelerate the Moon into falling | into the Earth (again). | sebzim4500 wrote: | There is basically nothing we could do to Earth that would | make it less habitable than Mars is. | | If we had the capability of terraforming Mars, it would be | trivial to fix climate change here on Earth. | swader999 wrote: | Have you read the conjecture/conspiracy theory that Mars | was nuked to oblivion in the distant past? This is good | entertainment: https://youtu.be/q9Nuy7mFIsE?feature=shared | bobsmooth wrote: | It's easier to just mine huge blocks of ice from Halley's Comet | and use that to cool the Earth. | CalRobert wrote: | A veritable annihilatrix | h2odragon wrote: | Nono, we need to wrap the planet in paper. That will shield us | from solar radiation as well as incoming rocks. And sequester | carbon. | | 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 | jmkni wrote: | Let's nuke the moon to solve Global Warming lol | | love it | swader999 wrote: | I'd be voting for a warmer planet if that was on the table. 2/3 | of the land mass is outside the tropics as it is and cold kills | more than heat. | dkbrk wrote: | There's nothing wrong with refining models, but it's a bit | besides the point. At a 1995 Planetary Defense workshop Edward | Teller proposed the development of a 1Gt device for that purpose. | Fusion bombs are actually quite straightforward to scale by | adding more stages, so it wouldn't be terribly more difficult to | produce a 10Gt device instead. What the model tells you is how | large a device you need, but all that's needed is a conservative | model that tells you the minimum size you need, and then you can | add a generous margin of safety on top of that. The goal is to | stop the asteroid hitting Earth, there's nothing wrong with | deflecting it "too much". | | 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. | andyjohnson0 wrote: | > But right now we have exactly zero such devices prepared. | | Who would build/host/control such a weapon? | coldtea wrote: | Not sure, but it would be deployed by a ragtag team of oil | rig miners... | jltsiren wrote: | Whoever is capable of solving the real challenge of | delivering the warhead. | | 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. | ragebol wrote: | > The goal is to stop the asteroid hitting Earth, there's | nothing wrong with deflecting it "too much". | | 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. | OscarCunningham wrote: | Space is mostly empty, a random orbit is very unlikely to hit | anything. | lupusreal wrote: | Hitting Earth later is better than now. If nothing else it | buys time for a new plan. And if it did wipe out a Moon base | with dozens of people, at least it wasn't a city with | millions... | zemvpferreira wrote: | Pardon the glibness but I feel humanity will survive longer | without an asteroid-deflecting technology than if we own 1Gt | nuclear devices. | | If that's the scale required, I propose ignoring the | possibility. | Gare wrote: | Tsar bomba was 100 Mt design, about 50 Mt test. Not much of a | difference, you're going to be toast anyway (multiple | "smaller" warheads are more economical and harder to | intercept anyways). | lupusreal wrote: | That's 5x larger than the Krakatoa explosion; huge but not | alone big enough to exterminate humanity. | | 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. | perihelions wrote: | We should consider ignoring asteroid-deflection itself as a | possibility. The scale of an asteroid impact, deliberately | instigated by deflection as an act of war, is far larger than | what humanity's capable of with nuclear weapons alone. | leoedin wrote: | Surely anyone on earth who has the technical ability to | deflect an asteroid precisely to hit one part of the | planet, would also have the technical ability to just bomb | that part of the planet directly - with much lower risk of | accidentally hitting the wrong part? | perihelions wrote: | The scale of asteroid impacts is much larger than nuclear | war. An actor could take out an entire continent at once, | or end human civilization globally. | | It's not _easy_ , but it's something like a 3-4 order of | magnitude multiplier if you figure out how to do it. | biorach wrote: | We already have hundreds (thousands?) of Mt devices. A | handful of Gt devices is not going to change anything as | regards humanity's threat to itself. | | In fact I believe that anything over the low tens of Mt is | considered impractical for military use. | 93po wrote: | Yeah I don't think anyone, even the craziest of dictators, | want to take over a country and then have to deal with a | giant smoldering radioactive hole in the ground the size of | rhode island. | mrangle wrote: | Good point, especially when referenced to he low chance of | the strategy working. | krisoft wrote: | > The goal is to stop the asteroid hitting Earth, there's | nothing wrong with deflecting it "too much". | | Unless of course you don't deflect it but break it up into | chunks where some of the chunks are still heading towards us. | ganzuul wrote: | 100 gigaton, then | | 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 | cookingmyserver wrote: | Which is why you would use waves of consecutive detonations | consisting of more and more (smaller) nukes. Think of a cone | pointed towards the asteroid. The tip would be the first | initial large nuke. Because of the mass and velocity of the | asteroid, it is unlikely that the fragments would spread out | all that much. You are right that there would likely be | fragments that still have an orbit that would lead to | collision. After the first explosion you would detonate 5 | more nukes spread out evenly to further perturb and break | down the asteroid remnants. You would repeat this many times. | Each time the nukes could be smaller as the mass of the | asteroid remnants would be getting smaller and smaller making | the force of the nukes more effective against them. This | would probably only be suitable for ruble pile asteroids, but | I would imagine those are the hardest to use ablation with, | so it may still be appropriate to use more destructive | methods. | | 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. | elzbardico wrote: | Hate to derail a bit from the discussion you're starting, but | let's always keep in mind that Teller would propose a 1GT for | frying bacon if you let him. | lupusreal wrote: | How do you negotiate who gets to use their bomb for this? Whoever | does it basically gets a free nuclear test that the other nuclear | powers would probably be jealous of, but those same nuclear | powers might also worry that their own bomb test, if they were | permitted one test as compensation, might not go off without a | hitch. They might therefore wish for there to be no nuclear | detonations at all, to avoid the risk of being embarrassed. | Furthermore there's also the issue of launch vehicle; some | nuclear powers are more experienced with deep space missions than | others, but fitting one country's bomb to another rocket may not | be politically possible. America, maybe China, Russia or India | could do it. The UK or France putting a nuke on an ESA rocket | seems questionable. Pakistan and the other nuclear powers | probably lack the requisite launch vehicle entirely but might | publicly assert that the whole thing is a sham to violate the | test / space weaponization bans. | soundarana wrote: | > _Whoever does it basically gets a free nuclear test that the | other nuclear powers would probably be jealous_ | | 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. | dotnet00 wrote: | Russia already pulled out of the nuclear test ban treaty, they | have no leverage over the West getting "a free nuclear test" | anymore, and anyway, all that the country doing the launch | needs to do is show the trajectory estimation data. | | 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). | cpursley wrote: | I'm worried about a Dark Forest strike than an asteroid. But glad | to see progress. | sgt101 wrote: | If these are your worries you live a blessed life! Remember | that your (and my) ancestors lived in fear of too much rain, | not enough rain, raiders, pestilence and the local overlord | getting upset about something. | alex_suzuki wrote: | I feel it's mandatory to mention ,,The Three-Body Problem" by | Cixin Liu here. What an amazing read. | cpursley wrote: | 3rd book in the series, incredible piece of writing. | jackcviers3 wrote: | The problem with the dark forest hypothesis is that there's | already no way to hide from the techinically advanced malignant | actors that could execute a Dark Forest strike in the first | place. | | 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. | cpursley wrote: | Yeah, I agree - the solution would seem to focus on spreading | out. | getwiththeprog wrote: | Published in The Planetary Science Journal | | 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. | nipponese wrote: | I was lucky enough to tour LLNL this year and saw a short | presentation from this group and of course I asked them about the | likelihood of an extinction-event asteroid hitting Earth. | | 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. | tetris11 wrote: | (lazy comment, but:) I'm sure we'll nip this one in the bud | like we have with all other planetary crises we've encountered. | | 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. | | 1: https://en.wikipedia.org/wiki/101955_Bennu | sigmoid10 wrote: | >an asteroid big enough to destroy an areas the size of Texas, | that WILL hit Earth in about 140 years | | 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. | | https://neo.ssa.esa.int/risk-list | ourmandave wrote: | From their About Page... | | _Mission Focus Areas | | Crafting broad-ranging solutions with immediate impact._ | | Might want to have the PR dept take a look at that wording. | picadores wrote: | How high are the chances of the asteroid disintegrating? As in | frozzen snowball with peebles? | JoeDaDude wrote: | I once met some people involved in Planetary Defense. One of them | launched a crowdfunding campaign to fund development of his | concept, the Hypervelocity Asteroid Intercept Vehicle. The | crowdfunding campaign only raised some 4% of the needed funs. | Nobody wanted to pay to save the Earth! | | https://www.indiegogo.com/projects/help-defend-earth-against... | XzAeRosho wrote: | TBH it's difficult to take serious any campaign running through | these crowdfunding platforms. My "scam alert" sirens start to | go off any time I see these kind of links. | JoeDaDude wrote: | I don't know this for a fact, but I suspect the Principal | Investigator was sold a bunch of baloney from the crowdsource | outfit. They do take a large portion of the funding, after | all. The PI had already been through Phase I and Phase II of | NASA funding and likely went to crowdfunding because he lost | Phase III. | | https://www.nasa.gov/general/an-innovative-solution-to- | nasas... | IlliOnato wrote: | Just to illustrate the level of the nudges involved. The most | dangerous currently known asteroid is Bennu, with 24 September | 2182 as the most likely date of hitting Earth. To do so, Bennu | must pass through a gravitational "keyhole" on 25 September 2135. | That keyhole is about 5 km wide. (To compare, the asteroid itself | is about 0.5 km wide). It's like deflecting a projectile that | shoots at a 5 km target from the distance of a couple hundred | million km. | swader999 wrote: | A test is worth a thousand words. Let's repurpose the arsenals. | dingaling wrote: | Most of the arsenal nowadays is fairly low-yield compared to | the heyday of the 1960s. | | The largest deployed US weapon was the B41 with a yield of at | least 25MT. The closest contemporary is the B83 at 1.2MT. | cookingmyserver wrote: | Glad to see this researched more. It has become popular in pop | culture science to bring up the "myth" of using nukes to | stop/deflect asteroids. Apparently, their incorrect use in a few | movies discounts them ever being used. Even "science | communicators" have participated in evangelizing the | ineffectiveness of nukes, never realizing you don't have to land | on the asteroid and drill a nuke into its core to use it | effectively. | | 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. | mrangle wrote: | The more surviveable option is probably to consider asteroid | impacts to be an unstoppable larger part of the evolutionary | cycle, however terrifying. Rather than risk destroying ourselves | via mishandling low-probability countermeasures. Spraying sun | blocking aerosol into the atmosphere to lower temps probably | falls into the same category. | michaelmrose wrote: | Given we already have nuclear weapons the probable risk of | developing such measures is logically meaningless. It's not | like we are giving nasa armed ICBMs ready to fire at a moments | notice. We are merely exploring a new use for existing hardware | which could be deployed in a reasonable time frame. | | 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. | reset2023 wrote: | Finally, someone working on something for the common good. | egberts1 wrote: | Mmmm, majority of vector thrush is heat-based atmospheric | pressure wave. | | 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. ___________________________________________________________________ (page generated 2023-12-21 23:00 UTC)