Scientists to nudge asteroid off course as practice for protecting Earth | Hacker News Reader

Scientists to nudge asteroid off course as practice for protecting Earth

independent.co.uk

143 pointshliyan64 comments

But wait. What if it's not just an asteroid... https://en.wikipedia.org/wiki/The_Dig

Understood that scientists would be able to break asteroid into pieces using many ways. I guess what they could take advantage of this asteroid is to put a drone or some sensor material on asteroid so that it would help space scientists for space research. Its almost like unmanned space mission, just put a drone-sensor on asteroid. It goes with the asteroid and sends down information which might be helpful. Any space scientists here in hackernews? What do you say? Would it be possible and beneficial?

I'm not sure there is a huge amount to be learned from asteroids unless we plan on bringing stuff back with us. We are certainly going to try to do that, and we have also landed a thing on a comet obviously which will teach us much more.

What's the whole thing about drilling a hole and dropping a nuke to split the asteroid up? I mean, I liked the Aerosmith song from that movie (Armageddon) but doesn't that actually seem like a sensible idea for a bigger rock?

Looks like some experts agree w me: http://www.space.com/21333-asteroid-nuke-spacecraft-mission....

Mankind never had to drill a hole in zero gravity, so I don't think we have such a tool in the first place. Besides, even if we had something like that, I imagine they would be rather heavy. Hauling it all the way to the asteroid will take a lot of fuel and money.

Could a very strong laser potentially work for this?

I would imagine a simple drill bit would do the trick - that action isn't dependent on gravity, and in an enclosed area (the bore) the simple action of the screw should do it. The real trick would be making sure the ejecta doesn't hang around. For small particulates you could use a static field, but larger masses would be harder.

But how are you going to press against the ground without gravity? If you don't press firmly, the drill bit will just scratch the surface instead of boring in. You don't have gravity, and you can't use suction cups (no air!), and I'm skeptical if you can grab on something and hold on to that. (It will require a lot of robotic engineering, and what if the surface is filled with loose gravel?)

Maybe you could fire a rocket in the opposite direction the whole time, but that increases fuel requirement even further.

Any landing on a such a low gravity object object would require some form of anchoring, which you can use to to get the drill started. The Philae lander (was designed to) use its impact velocity to drive ice screws into the surface, before fireing a harpoon. Presumably such a harpoon could give sufficient leverage to get run a drill.

Of course, if you followed the landing, you know that things didn't quiet go as planned, and Philae bounced a few times (and almost escaped the gravity), so this is definitely a difficult problem, but I suspect that once you have a lander that can anchor itself enought to not bounce, you could probably anchor yourself enough to drill.

I was thinking abut this, and it seems to me that the Third Law problem only exists when you're starting the drilling (pressing down) and removing the drill (pulling up). During the actual drilling procedure, there should be a force from the action of the drill bit digging into the rock, and from the stuff being bored away from the drill. Shouldn't there be an equilibrium point where the pressure you're exerting on the drill (pushing you up) matches the force of the drill pulling you down? I feel [1] that higher torque speeds would impact this.

[1] "I feel," "It seems," etc. - I don't have the maths or the physics to back this up beyond intuition and a hasty free body diagram sketch, which admittedly seems to work well-ish for most problems in classical mechanical physics.

Basically, if there's nothing stopping you from spinning then the drill will spin you but with the bit stationary. The fixture holding the drill needs to be secured somehow so that the motor in the drill spins the bit against the surface. On Earth, this is commonly achieved using your feet and friction.

Exactly. There are so many problems with drilling/mining asteroids, its going to be one of the most enormous challenges ever undertaken.

The drill doesn't pull you down. The equilibrium is achieved by (roughly speaking) (the force that the drill bit pushes the ground) = (the force that the ground pushes the drill up) = (the force that you push the drill down) = (the force that the drill pushes you up) = (the force that the Earth pulls you down).

The Earth's gravity on your body enables all this force; without it you need to invent some other way of pushing down the drill.

You need leverage to drill. You have to push down a bit on whatever you are drilling into, which will push you away from it. So, until you drill in enough to get leverage on the target, you've got to either counteract this force, or keep extending your drill arm as you drift away.

If you can deflect with a simple impact, it's always going to be the most reliable.

If you look at the numerous things that went wrong with the Philae lander...

https://en.wikipedia.org/wiki/Philae_%28spacecraft%29

you wouldn't want any of that to happen on a life-or-death mission. Also... a landing either requires enormous amounts of fuel or between months and years of manoeuvring time.

It works for small <10m astroids, but for anything bigger than that, its own gravity will pull the segments back together after the explosion since they do not reach escape velocity, and nothing will have changed due to conservation of momentum. A better method is to detonate an astroid up to 100m away so it heats up the surface. The heat will blow off small particles at more than escape velocity, so by conservation of momentum the astroid will be pushed in the opposite direction.

Hey, that's a really cool idea! Using an asteroid as its own propellant.

Yeah! Has anyone actually investigated this or written about it??

https://en.wikipedia.org/wiki/Asteroid_impact_avoidance#Hist... - Project Icarus is almost 50 years old. There was a paper about laser ablation 2 years ago. Lot of literature on many different collision avoidance strategies.

There was a talk this year at LLNL showcasing a few methods, each with high resolution mesh-based simulations. Hopefully that's enough information so you can find the slides online.

Can you explain why the nuke option wouldn't work? It seems to me that most of Earth's protection against asteroids is them burning up in the Earth's atmosphere.

Let's assume that you did blow up an asteroid, and the constituent parts loosely reassembled. Wouldn't they they break apart again as soon as they started to experience the turbulent effects of the Earth's atmosphere? And once they did, the surface area to mass ratio of the asteroid matter would be an order of magnitude or higher, pretty much guaranteeing all of the mini-asteroid parts would burn up.

No doubt I'm wrong. I'm a programmer, not a physicist or an astronomer. So I'm seeking to get 'educated' more than I am to argue with you.

Something the size of a dinosaur killer is going to cause a devastating shockwave at the surface, even if you manage to break it into small parts. Plus, breaking it into many small parts of known trajectory, with a very small standard deviation in size, is going to be a much more difficult problem than nudging one big part. Once the no-doubt irregularly-shaped chunks start interacting and banging into each other, all bets about impact sites are going to be off. You'd much rather miss the planet entirely instead of running the risk of a larger-than-average chunk hitting New York or Beijing.

On top of that, nudging it out of a collision trajectory is going to require a lot less energy than disintegrating it, particularly if you can arrange to do the nudge a long way off. What's easier, pushing a runaway shopping cart so it doesn't bang into your car, or tearing the cart into parts small enough that they don't do any damage when they hit?

Neal Stephenson's latest novel, Seveneves has some discussion of this (on a much larger scale, granted).

Another issue that is usually the first objection is that receiving a thousand highly radioactive rocks at very high velocity is a very efficient way for us humans to die in large numbers. Just one radioactive meteor would cause a lot of damage and be very difficult to seal off, but a thousand?

I think you're a bit confused by nuclear scare-mongering. Large fusion H-bombs put out stuff all radiation. And radiation isn't very deadly anyway.

Why would mass only a bit larger than 10m in diameter have so much gravitational pull?

Are there really asteroids so big that a nuke could not even chip off a small fraction at escape velocity? If ablative impulse could cause enough of a course change to miss earth, then why would detonative propulsion not do that job even better?

DOE NNSA SSGF 2015: NNSA Activities in Planetary Defense: https://www.youtube.com/watch?v=AeBxuwXC6GA

There is another very similar video, maybe of the same slides with a inset of the speaker, but I can't find it atm.

There are some situations in which this might work, but many other where it wouldn't. The asteroid would have to be small enough that the bomb could fragment it sufficiently, we'd also have to be able to hit it early enough and fragment it enough that most of the fragments would miss the earth. If the asteroid was above the fragmentation capability of the warhead, or if it was detected late enough that the fragments would mostly still hit the earth then it wouldn't help.

Bear in mind that if most of the fragments still hit earth, the net energy delivery would still be about the same. This could actually be worse for the planet as a whole than a single hit. Finally, whether such a bomb could be effective would also depend on the structure of the asteroid or comet. This is due to the bugsplat effect, army slang for the fact that when a bomb hits a building or vehicle, the energy seems to be expended very asymmetrically. If you crush a bug with your boot, one part of the exoskeleton will weaken before the others and the insides get sprayed out in that direction. Similarly, if a bomb hits a vehicle often the majority of the explosive effect tends to get directed primarily in one direction. There are cases of people close to one side of a vehicle surviving unharmed, while people much further away in other directions get incinerated or hit by fragments. Similarly if the internal structure of the asteroid is asymmetrical, you could end up with material on one side of the asteroid (perhaps made up of already loose boulder material and dust) being thoroughly fragmented while larger more dense parts of it on the other surviving. Instead of many similarly sized fragments, you might well end up with a large percentage of the object remaining intact and all you did was scrub off looser material.

I'm sure this will not affect gravity paths somewhat as a butterfly effect.

Nope. Everything involved is way too small to do something like that. Worst case scenario is we get a shooting star.

Not true. Due to the butterfly effect, even tiny changes to a system will totally change the output given enough time. Simulations of the orbits of the planets turn out totally different after billions of years if the measurements of planets are changed by even an inch.

I get your point, but this thing is many, many orders of magnitude smaller than a planet.

If it did, why would there be any reason to expect that the average influence would be more bad than good?

Sure. It will be about equivalent. 99.9999999% chance of doing nothing, half the rest is good, the other part bad.

So do satellites and spacecraft, but we still choose to send them out. What's different about nudging an asteroid?

Butterfly effect only has meaning in a closed system simulation context, where we can find a small difference in initial condition which triggers major changes in later simulation. When talking about real life, it is meaningless, because we can not "rerun" life to check the result after minor change.

Wouldn't it be funny if they nudge it off its current course, onto a collision course with us?

No, actually not that funny.

The article states it wouldn't do any harm to Earth if it hit, and a planet is a pretty hard target to hit even intentionally.

What would be ironic given that quote from the article is if we nudged it into the path of a larger asteroid and that collision sent the larger, dangerous asteroid into our path. Perhaps the larger asteroid fragments in a way to increase the probability of a collision with the fragments.

Don't get me wrong... I do agree with you that all of these scenarios are extremely unlikely (space is really big) and I do think the experiment is worth doing. But still, there are failure modes and unintended consequence opportunities that should at least be thought about a bit, even if a very little bit.

In this case, wouldn't any risk of a butterfly effect causing an asteroid to hit us be offset by the chance of a butterfly effect accidentally deflecting an asteriod off of a colission course.

European or African butterflies?

European and laden.

> But still, there are failure modes and unintended consequence opportunities that should at least be thought about a bit, even if a very little bit.

I think it's highly likely that the people responsible for these projects will realize this. Do you disagree?

Given the limited knowledge we have about space, how accurate are the assumptions that no harm will be done? We are still figuring out water on Mars and that is quite near to Earth.

"Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space."

- Douglas Adams

Chances of anything striking anything as a result of human intervention are quite slim. Effectively nil.

I would be pleasantly surprised if NASA could nudge an asteroid massive enough to pose a threat to human life on Earth.

If we can nudge it into a collision course, surely we can nudge it out of one.

That would be hilarious, to a sufficiently distant civilization after a respectable amount of time. Maybe there's some kind of award they give out to planets that self-destruct. But instead of the Darwin award, it's called the Fermi award.

It's on the same sort of humorous level as something Douglas Adams might write.

It's not actually large enough to pose a threat (according to the article), so even if that happened, we'd be ok.

Or onto a collision course with a different inhabited planet. Who interprets it as an act of war.

This whole comments section is making me want to read some scifi about this. Anybody have any recommendations?

Mix Starship Troopers with The Forever War.

https://en.wikipedia.org/wiki/Nemesis_Games

There's some rock throwing in this latest book in the Expanse series. You'd want to read the earlier books beforehand though. (They are worth reading anyway.)

Arthur C. Clarke's 'The Hammer of God'

There is some super nice rock throwing in this book: https://en.wikipedia.org/wiki/Prador_Moon

https://en.wikipedia.org/wiki/Building_Harlequin%27s_Moon

suspended animation interspersed with patiently building a habitable environment out of asteroids & comets.

Neal Stephenson's 2015 speculative fiction novel 'Seveneves.'

The last book of https://en.wikipedia.org/wiki/Michael_F._Flynn#Firestar_seri... is all about deflecting asteroids, IIRC.

Starship Troopers covered it pretty well

"Thirty years before the First Interstellar War, a meteorite from Klendathu System was deviated from its star during the Operation Fedmil, the first contact in Klendathu. Thirty years later, the meteorite reached and hit Earth, destroying Buenos Aires, capital of Argentina, killing over 8.7 Million, and wounding a further 12.5 million."

"However, the United Citizen Federation claimed that the Arachnid launching a "Bug Meteor" by Bug Plasma from the Klendathu system towards Earth and destroyed the city of Buenos Aires."

My thoughts exactly.

Actually it's funny, just not to us.

Well NASA recently made a statement that there's no significant asteroid going to hit Earth for centuries to come thus shunning growing rumours by conspiracy theorist about Planet X. SO why are they spending dollars on such a scenario (specially when NASA's budget has been reduced recently)? It could rather be spent on say human mission to Mars ETC which are near term possibilities.

Because Nasa can only see about 10% of the entire sky. Meaning, they can't see the other 90% probability that it might hit some day.

Because it is cool to do so. And it could confirm some data.

Actually, what would be a good reason NOT to do it ?

Let's say a mass-extinction causing space object hits Earth every 100 million years (https://en.wikipedia.org/wiki/Extinction_event) . That gives us a 1e-8 chance of all 7e9 people being wiped out in one year. That's an average of 700 people killed every year if it were spread out in time.

Definitely a serious risk even if not the most pressing right now. It is however more dangerous than terrorism in America, and plenty of money is being spent on that!

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