Those damn Vogons, just fly-tipping again!
An asteroid named Itokawa that's been identified as potentially hazardous to Earth would be difficult to destroy, according to new research analyzing dust particles collected from the ancient rock. Measuring 330 metres across, Itokawa is the first-ever asteroid to be sampled in a space mission. Japan's Aerospace Exploration …
Best of luck getting that fecker accepted down at the local council recycling centre
Me: It's a 4.2 billion year old asteroid
Council Operative: Has it come from a pre-1970s property?
Me: Well not exactly - it's primordial space matter
Council Operative: So it might have asbestos in it?
Me: It's the closing speed of 50km/s you should probably be worried about...
> it's entirely made of loose boulders and rocks
So what is needed is a bowling champion to plot exactly what path an incoming "bowling ball" would need to take to scatter all the largest rocks onto different vectors. Maybe they would all hit Earth at some point, but I suspect lots of little space rocks falling in geographically dispersed areas is better than one large one.
It depends on the timescale over which the bits enter the atmosphere. If you were to take all of the rocks and dust that enter the atmosphere in a year, stick them all in one ball, and throw them at the atmosphere in one go then you would see a very significant event. So if you can take your asteroid and turn it into a smear of rubble that enters the atmosphere over a number of weeks then the planet would barely notice.
But if you expand your asteroid into a cloud that hits all at the same time then the concentration of energy imparted to the atmosphere will mean that the event would be pretty much similar to the original asteroid hitting instead. The altitude and distribution of energy would likely vary but the amount over a short period of time would not.
I could go on thinking about different scenarios and the effect they would have, but I'm afraid I have some of the 'W' word to do.
This article doesn't say how large the boulders are. Will they just provide pretty blinkenlights as they fall from the sky or will there be a big KABOOM? At least they are good at absorbing impact, so we won't have to. I just watched a whole lot of UnchartedX on YouTube about the Younger Dryass impact, etc. I want to know if it will be necessary to start building all sorts of big and weird granite stuff for future civilizations to find after ours is wiped out?
"like using the shockwave of a close-by nuclear blast to push a rubble-pile asteroid off course without destroying it." I was under the impression that if you don't have an atmosphere you can't have a shockwave? Surely you need a medium for a wave to propagate through, which certainly isn't space.
the outgassing will act like a rocket
How much gas, how quickly, what force ? I suspect that most of the heating will be absorbed by the rubble/sand/... close to the nuke, some of it will be vaporised. So some material will be made to move but most of it very little. The result will be that it bulges for a bit but most of it will still hit us.
After a few years gravity will have pulled it all together again.
Really it looks much more like an asteroid pusher is what is needed. Fortunately we have a couple of example designs for just such a device.
The first one is to modify the Project Orion vehicle by giving it a huge network of struts at the front and using these to push against the asteroid once the vehicle is resting against it. Project Orion operated by letting off lots of nuclear fusion bombs behind it, one at a time, and using the plasma blasts from these to push it forwards.
The second trick would be to use a high temperature nuclear reactor to vaporise a reaction mass (gallium metal being one example) and use this as a rocket; if you only have a short time then lots of gallium and a fast-burn reactor is needed; if you have more time to react then a more sophisticated gallium-using ion drive unit would be more efficient.
Either way, the simplistic trick of simply blowing the rubble pile apart into a cloud is only ever going to be a last resort, and this will only work if the blast is truly titanic and manages to separate the pile into a very large and diffuse cloud.
What's wrong with nuclear weapons?
The Soviet Lake Chagan needed just a 140 kiloton weapon. Take a megaton range warhead, attach it to a penetrator, and you have an asteroid killer. You can even send two or three warheads once after each other to create a hole and then make the hole bigger. Targeting would be difficult but manageable with enought resources put into it.
I'm afraid a rubble pile with a hole in it is still a considerable mass, making a considerable amount of damage when it hits...
As others already said, you'd need to transform that rubble pile into a diffuse cloud of semi-isolated gravel so it can burn up when entering the atmosphere.
As for the resources, I'm afraid there will be quite some "why should we pay for it since it will mostly hit somebody else?" going on.
A slightly-embedded nuke will vaporize a significant bit of the meteor, which will in turn a more significant bit into ejecta. Newton will then cause the creation of said ejecta to have an equal and opposite effect of providing a significant kick to the asteroid.
Perhaps not as satisfying as going full Bruce Willis, but quite effective.
The challenge being to get the proper penetration before detonation. With a rock pile, this will always be a crap shoot, and you REALLY don't want to roll snake eyes.
The "nice" thing is that it should not be overly difficult to send a series of nukes timed an hour or so apart. Of course, adjusting the aim will be tricky, but fortunately, it will be the most tricky precisely when the later nukes are not actually needed.
Also, if we can control the direction of the push, the actual amount of the diversion that we will need will likely be much less than 8,000 miles--although again, this is not the sort of operation that befits tight design margins.
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Aiming something at the sun is not as easy as it might first seem. You'd have to push the asteroid in such a way that it loses its orbital velocity, leaving it to fall directly towards the sun. If it's left with even a slight velocity component horizontal to the radial line, you risk it missing the sun and slingshotting around and back towards you. It needs to either hit or pass close enough to the sun that the tidal forces rip it apart, and if it is ripped apart then the fragments have to be small enough that you can't be harmed by them: it becomes just another regular meteor shower like the Leonids et al.
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Regarding the "nuclear" options . . .
In order to "bury" a nuclear device in this rubble pile, presumably one would need to match "course and speed" in order to do so. Then having detonated, if the trajectory of this now radioactive mess, err, mass, was not altered sufficiently to miss Earth entirely, you can add nuclear "fallout" to the environmental horror show.
There have been plans using a small spacecraft's gravity to very slightly tug an asteroid's orbit, which over a period of years or decades would move it away from a collision course with Earth. We have to find it with a lot of warning, but we are always discovering new asteroids where the initial announcement says there's " it presents no danger in its current approach but there's a 1 in 1000 chance of impact in 2061" that's later clarified to be no chance after we nail down its orbital path more precisely. If we found one like that but found it definitely would impact Earth in 2061 we'd have enough time where even a very tiny gravitational tug would be enough to make it miss. If we need more we send a bunch of spacecraft out there to work together and present a bigger mass - just keep adding to it as the nations of the world build more spacecraft.
This strategy would work exactly the same way for a rubble pile as for a solid asteroid. The fact it is of lower density means it has less mass thus reducing the amount of warning time required.
An asteroid with a very long orbital period that was going to hit us on its next pass by Earth wouldn't give us nearly enough warning for this though.
There was a lot of flashy displaying of high-power lasers a decade or more ago, blowing up objects like a missile, etc. Including ideas of putting such high-powered lasers into fighter jets for that ultimate space cadet feeling, bullseyeing womp rats from ... how many metres, again?
I'd say a much easier way to move a space junk pile is to send a asteroid nudger, with one of those high-powered lasers and enough propellant that it can match velocity and orbit, stay in orbit and change orbit for as long as necessary. Then from a distance of a few thousand kilometres, blast the space junk pile with ablative blasts in the direction of orbit. A steady set of such laser blasts won't tear the asteroid to pieces, but it will shift the material, and the ablative blasts will change the orbit somewhat.
The great advantage of doing it bit by bit, piece by piece, is that you don't have to get it right the first time. You can do it over a few months, and apply corrections if you find you've hit a snag of sorts.
My 0.02c worth, and don't spend it all at once.
if this is a loosely bound collection of rocks, it cannot be considered as a solid object. On entering the atmosphere, it is more likely to expand as would a thrown handful of dry sand. Meteorites only reach the ground if they're a solid object of sufficient size to avoid being ablated to nothing, on the way down. . The shock wave (sonic boom) of the collection, is a different matter. That, as an aimed object might have a far better chance of causing damage.
Most commenters seem to think it as a solid or semi-solid object, like a pile of rubble on ground would be. It's nothing like that.
First, stones itself are mostly empty space (most of them would float on water) and there's a lot of empty space between them. Second: Despite volume, the pile is held together only by internal gravity which has to be *very* low, like in micro-G-class. Third: That means escape velocity is very, very low (mm/s, anyone?) and can be achieved with very low force, especially when first point is noted.
Big can of compressed air would be enough to push most of the stones above escape velocity and then there's not a pile anymore and most of the pieces have very altered trajectory.
People talking about atomic bomb are at least 5 orders of magnitude off. Unless the idea is to transform all of it to fast expanding cloud of gas: Despite the size, the mass of the pile is very low and therefore easy to vaporize.
The idea that the radioactive cloud will hit Earth is also really odd: It's not a solid object. It would expand to every direction (literally) at relativistic speeds and only a very small faction of it would hit Earth, in "barely measurable" -class.