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# Cutting asteroid in sections to save earth

Cutting an Astroid in half (or more sections) to prevent earth collision.
 (+5, -3) [vote for, against]

If the (solid) asteroid is on a collision courese with the earth then we can then send a spacecraft to intercept it. By using carbon nanotubes, we will have a very small very strong wire. Have the spacecraft consist of 3 parts, a left, right and center. The left and right parts will keep the wire taut and the center part will be a wedge. Considering the incredibly small cross section, we sould be able to cut solid asteroids in half or more sections (like a wire cheese cutter) then the wedge could sligtly alter the orbit. This can be repeted many times to make a much smaller mass hit the earth or possiblty not hitting the earth at all.
 — SolarDon, Feb 27 2012

Giant cable saw http://www.smit.com...page.asp?pageid=148
If it worked on a submarine, why not an asteroid? [Alterother, Feb 28 2012]

[normzone, Feb 29 2012]

An asteroid already sliced up http://www.tarlani..../Asteroid-Vesta.jpg
[ldischler, Feb 29 2012]

Massive diamond wire saw... the saw... not the diamonds. http://fzskystone.e...ndstone-Quarry.html
[2 fries shy of a happy meal, Nov 20 2017]

I vote for putting the pieces around the Earth to make rings like Saturn.
 — FlyingToaster, Feb 27 2012

 I'm not 100% convinced. As far as I know, we can't make a long wire of carbon nanotubes and, if we could, would they cut rock like a cheese wire?

 Would it make sense energetically? If the asteroid is basically rock, its surface energy will be something like 1-10J/m^2. So, you wouldn't need a great deal of energy to cut it.

 But, having cut it, you still need to deflect the halves (or quarters, eighths...). Why not just put all the energy into deflecting the intact asteroid?

Also, congratulations on your first post!
 — MaxwellBuchanan, Feb 27 2012

 I suppose if the relative velocity of the wire and the asteroid is great enough it might do something to it, but a well-aimed rock would make more sense.

 Very halfbaked in an interesting fashion.

Saturn rings? I think our satellites might dislike that. Now, maybe if the asteroid were made of cream cheese perhaps and we had a giant bagel...
 — RayfordSteele, Feb 27 2012

One advantage to a sliced/blown apart asteroid is the larger surface area to volume, resulting in greater atmospheric friction during descent (especially slices, which would tumble more in the atmosphere). That being said, until we can actually produce kilometer long monomolecular tubes (as opposed to polymolecular yarns), I doubt this is feasible.
 — MechE, Feb 28 2012

//Why not just put all the energy into deflecting the intact asteroid?// Because if you do that you'll have to redo all your calculations for the entire asteroid belt. Supposing its orbital dynamics to be sensitively dependent on initial conditions, there might now be another asteroid on a collision course. This idea has the advantage of neutralizing the asteroid without budging its center of mass.
 — mouseposture, Feb 28 2012

 [SolarDon] joined us in the fall of 2010, has annoed on a whopping four ideas since then, and this is the first idea from the account.

Welcome! Have you been spending all this time sawing rocks?
 — normzone, Feb 28 2012

 //        if we could, would they cut rock like a cheese wire?   //

 Doubtful. The key to a blade made for cutting very hard things like stone or metal is abrasiveness, not strength. The cutting discs I use on my 4 1/2" angle grinder are so flimsy that you can snap them in half with your fingers, but they will slice through half an inch of steel in a few seconds if used properly (which is why welders sometimes call them 'speed wheels').

 For this application, the best solution would probably resemble the saw used to slice up the Kursk , only built to a currently impossible scale.

A very ambitious inaugural post.
 — Alterother, Feb 28 2012

 [Alt] - you're dead right, with the only exception that a highspeed cutting disc is actually very rigid due to centrifugal forces when spun at 12000 rpm or so. The cutting effectiveness is due to the interface speed : cutting penetration speed ratio.

 ... It could also be argued that stone and other brittle materials are more efficiently fractured rather than cut, which is why most asteroid destruction ideas involve using explosives of one kind or another.

Cue [7th] to talk about brisance and other such interesting things.
 — Custardguts, Feb 28 2012

Most... no, all ideas that I have seen seem to be based on deflection of some kind. But if the pieces are separated so that they hit one after the other, i.e. not much deflection, but a small change in velocity relative to each other so that they hit with several hours difference, maybe the individual impacts would be reduced to acceptable levels.
 — Ling, Feb 28 2012

But the same amount of mass will still be impacting the Earth in what amounts to, geologically speaking, the blink of an eye.
 — Alterother, Feb 28 2012

No, read [MechE]'s anno, above. More of the energy gets dissipated in atmosphere, less at ground (or sea) level. And as [Ling] pointed out, spread out over time as well. Might make a difference for some range of asteroid-masses. Plus, as [mouseposture] noted above, it satisfies the principle of "primum non nocere."
 — mouseposture, Feb 28 2012

[Alterother] Putting it that way, yes, of course. However, if each impact was separated by several hours, then the impact point would be different as the Earth rotated. Also, it goes without saying that if a 1 mile diameter asteroid is divided into two, then it probably wouldn't make much difference. But a series of smaller pieces which are separated by time wouldn't need much energy to separate them, and the force to separate them could push on one to push another.
 — Ling, Feb 28 2012

Okay, that's cool.
 — Alterother, Feb 28 2012

 Even if it all burned up, a dinosaur killer in atmosphere is going to create a significant temeprature rise (the energy goes somewhere). What it won't do is scatter the tonnes and tonnes of material (water/crust for an ocean strike, crust for a land strike) into the atmosphere, eliminating the nuclear winter effect.

While you would still get massive storms from the air displacement and heating, you would be able to grow crops next summer, a major advantage in terms of human survivability.
 — MechE, Feb 28 2012

 Once cut, you could set off a small charge between the two asteroids and cause their paths to diverge.

 I assert that the amount of explosive needed for this would be much less than would be needed if it were simply placed on the asteroid surface and detonated.

 I like the word "tought" as well: components of "tough" and "taut" with overtones of "taught" in the sense of "schooled".

Plus if ther is one incoming rock there is probably more, especially if it is an initial war effort by an alien race. The wire ships could spool out some fresh wire and be ready in place for subsequent rocks.
 — bungston, Feb 28 2012

 //I assert that the amount of explosive needed for this would be much less than would be needed if it were simply placed on the asteroid surface and detonated.//

I assert that this assertion is incorrect. What matters is momentum transfer. Even with a surface detonation (assuming placement in a slight pit or depression), the vast majority of the momentum is going to be transferred to the asteroid, either by particulate thrust directly away, particulate impacting the surface, or particulate bouncing off the surface. If the explosive is placed directly between two sections, you would see a slight gain from particulate bouncing off the surface, but that is about it. Definitely not "much less".
 — MechE, Feb 28 2012

Though it pains me to say, this conflict of assertions calls for mediation by the Borg. Perhaps, if we're lucky, [MikeD] will drop by and save us from 500 words of mockery and thinly- veiled scorn salted with self-congratulatory overtones.
 — Alterother, Feb 28 2012

How're you going to fasten this very small, very strong wire to your spacecraft? At the moment of collision I can see parts of your spacecraft being neatly sliced apart while the asteroid continues upon its merry way like a rampaging toddler with a strand of spaghetti stuck to his forehead.
 — AusCan531, Feb 28 2012

 You're doing this all wrong, you know.

 The asteroid is small, fast-moving, far away and in a hostile environment. In contrast the earth is big, stationary (well, relatively), close at hand and in a comfortable working environment.

Therefore, it would make far more sense to bisect the earth and move the two halves apart a little. We can then thumb our noses at the asteroid as it passes through the gap, and pull the two halves back together again.
 — MaxwellBuchanan, Feb 28 2012

I propose we call this the Moses Manoeuvre.
 — Ling, Feb 28 2012

Seconded.
 — Alterother, Feb 29 2012

 Would it consume any less energy if we tunneled through the earth and let it pass through in that manner? I understand it would be a curved tunnel, due to rotationary influences.

While I wholeheartedly endorse the Moses Maneuver (although I think the British / Canadian spelling is FAR cooler) there might be people on the edges of the cut who would be upset. The tunnel should minimize this.
 — normzone, Feb 29 2012

//[maneuver] I think the British / Canadian spelling is FAR cooler// oh it is... right up to the point where you actually have to spell it.
 — FlyingToaster, Feb 29 2012

Carbon nanotube magic. And how would cutting it into pizza wedges change the orbit? It wouldn't change anything at all, the orbit or the lethality, as most asteroids are rubble piles to begin with.
 — ldischler, Feb 29 2012

 // there might be people on the edges of the cut who would be upset//

 Au contraire. Can you imagine anything more spectacular than being able to stand on the edge of a 13,000 kilometer cliff, waving to your friends a few hundred metres away on the other side, and waiting for an million-ton asteroid to go past at several kilometres per second?

 The event would be a complete sell-out, and any country fortunate enough to lie on the bisection line would be able to sell tickets for astronomical prices.

As a bonus, all sorts of waste could be dumped over the edge just before the two halves are brought back together. In this way, the nuclear industry could completely clear its backlog of used fuel rods, and the hosting country could charge for the privilege.
 — MaxwellBuchanan, Feb 29 2012

//astronomical// The price would inevitably be astronomical, even if it were low.
 — mouseposture, Feb 29 2012

 Back up to the original idea: I'm thinking that if your solid asteroid has any rotation at all--which it likely will--you can use that.

You'd need to slice it from pole to pole--into east and west hemis, not north and south--and keep it from splitting until you were ready. Letting the two halves separate at the right time would cause them to go out from the trajectory, no explosives needed.
 — baconbrain, Feb 29 2012

Isn't there a formal system for naming asteroids? Would you have to start appending a suffix to the end of the name for the left / right halves when you split it?
 — normzone, Feb 29 2012

Using the asteroid's natural rotation against a stationary cutting implement presents three new issues (I'm not going to call them problems yet). The first is the matter of starting the cut; the asteroid is not going to be perfectly round, which means the cutting edge will be in and out of contact with the asteroid's surface until all of the protrusions have been trenched. Anyone familiar with industrial cutting or machining will tell you that this is the second- worst punishment that can be inflicted upon a stationary cutting implement (the absolute worst being lateral torsion). Secondly, the rate of cutting will decrease dramatically as the implement nears the core, both because the rotation is relatively slower there than on the surface, and because the area in contact will be focused on a small region of the implement, which will lead to excessive heat build-up and uneven wear. Finally, since the cutting implement itself remains stationary and therefore is not ejecting the waste material from the kerf, removal of material will require an altogether separate mechanism to prevent material build- up and subsequent jamming.
 — Alterother, Feb 29 2012

I think rotation is going to be present in almost all cases. I think I've read at least three different references to that (if something comes into view and it isn't rotating, it is most likely a spacecraft).
 — baconbrain, Feb 29 2012

I think you're right. Last anno edited to reflect such (and for minor clarification).
 — Alterother, Feb 29 2012

 So why a wire? Why not a cutting torch?A heat laser set on the right tangent, (is that the right word?) should remove the ejecta as spin brings the scree to be vaporized. Low lying areas would remain in shadow longer so irregularities would even out over time, and a slower spinning core wouldn't matter one whit as long as the angle of the laser rotated perpendicular-wise to compensate.

I also think that asteroid cross-section atmospheric discus skipping would be a hoot.
 — 2 fries shy of a happy meal, Feb 29 2012

 // Why not a cutting torch? //

 Why not a cutting torch? It sounds feasible to me, but I know next-to-nothing about laser. All of the energetic cutting implements I'm familiar with only operate in an atmosphere (with the possible exception of the particle- beam cutter I saw demonstrated at a trade show).

 // I also think that asteroid cross-section atmospheric discus skipping would be a hoot. //

It would be the greatest singular bookmaking event of all time, shirley.
 — Alterother, Feb 29 2012

If you cut an asteroid in half, do you get two hemiroids?
 — MaxwellBuchanan, Feb 29 2012

Only if they're in orbit around Uranus.
 — AusCan531, Feb 29 2012

Tshh boom.
 — MaxwellBuchanan, Feb 29 2012

 //bookmaking event of all time////around Uranus//

 That's the thing. You've got to get just the right angle off of Earth in order to ricochet Murcury, then sling-shot the sun in order to skip off Mars if you want any chance of getting all the way to a bounce all the way to Pluto.

 I don't care what anybody says it is so still a planet.You don't just down-grade a planet.

 No you don't.

 You just chalk one up to experience and give it honorary status. It then becomes unique, and a challenge. Perhaps the criteria could be met to one day to elevate it from its current state. It could be our asteroid catcher, slowly building in mass until eons from now we've made a planet where one would not have existed otherwise.You don't know.

Could happen.
 — 2 fries shy of a happy meal, Feb 29 2012

If enough asteroids can be impacted on Pluto, it'll eventually meet the current criteria for planethood.
 — MaxwellBuchanan, Feb 29 2012

The whole idea is of course predicated on having a kilometer (or two) long piece of carbon nanotube. I like Alterother's idea about a cutting torch however the event would probably happens so fast (probably a least a few thousand miles per hour), that the heat would not have time to make any difference. Iin terms of kerf, remember that this wire would literally only be about 6 carbon atoms in diameter. At these scales, there would be plenty or room for the kerf. Thanks from multiple people for mentioning the rotation. This would alleviate the need for the wedge, since once it was separated, the torque would couse the pieces to fly apart.
 — SolarDon, Mar 01 2012

: ]
is this thing on...?
 — 2 fries shy of a happy meal, Mar 01 2012

The laser-torch wasn't [The Alterother]'s idea; full credit goes to his good friend [2fries].
 — Alterother, Mar 01 2012

 Large wire saw cutting stone like cheese. [link]

Ooh, I wonder if there are any asteroid geodes floating around out there.
 — 2 fries shy of a happy meal, Nov 20 2017

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