[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.
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