In the current level of technology, what would stop a impact event?

[AngelLestat]

Like some of you mentioned, it depends on time to launch the mission, asteroid mass, composition and time to impact.

What I mean? If we found an asteroid that comes back every 20 years, but the next time that will pass near sun it would be in 10 years, but it would not hit, only the next time after 30 years will hit earth. Then if it has a mass of gilly "maybe" we can have a little chance to save us.

And I am being very optimist, taking a really good plan with all world economic put in there for the first encouter and a high technologie progress for the next encounter.

But if we need to stop it just in the first encounter. Then we are doom, even if we had the technologie advances of 70 years ahead from now.

The amount of mass that we are talking about is huge.. The kinetic energy that carrys is incredible.

The amount of energy in a nuke is nothing in comparison, and the efficiency of thrust in the right direction that you can get from the nuke is 0,1 to 10%. To increase efficiency you need to do a previus explotion to make a crater, then the crater would serve like nozzle for the next nuclear devices.

Some of you said nuclear pulse, that maybe would be a better solution, but still is not enought.

You have limit nuclear fuel, how many energy you need to move (gilly) 1.2420512×10^17 kg, lets said that you need 1 x 10^-10m/s of delta V to avoid the next encounter in 30 years, then with 10 tons of nuclear fuel over the asteroid with a nuclear pulse engine that has an ISP of 10000, you can get roughly approximate 1 x 10^-14 m/s in dV? correct me if I am wrong.. I am not totally sure about the dV requisites to avoid earth in a timelapse of 30 years.

So any fuel that you can carry to the asteroid it would not help much. You need to use the same mass of the asteroid like reaction mass. For that reason know the asteroid composition is also very important.

I always remember a book of arthur C clarke "light of other days", one of the aspects of the book talk about a huge asteroid that would hit the earth in 500 years from that time with not previous pass.

In the book the people knew than even estimating techonologies advances in 500 years it would not be possible to divert it.

That novel really open my eyes about the energy levels that huge objects can carry. I guess if we were in the same problem, maybe a solution would be try to move the earth instead in those 500 years.

Edited September 27, 2013 by AngelLestat

[SargeRho]

For a large body, anchor a solar sail on it, or have a solar reflector fly next to it, heating one side. If it moves by as little as 2cm, its trajectory will no longer hit Earth.

[Randox]

If you can solve the issues of Nukes being heavy, and that you would need to embed them in the asteroid to make them truly effective (I think, seeing as a vacuum leaves to medium for the concussive force to act through), then fragmentation should be extremly effective. Sure, you might still have pieces large enough to make impact through our atmosphere, but unless the asteroid was so massive that it's gravity could hold the debris together in a group, then the pieces will drift away over time. Earth is not that big, so I would think that even given just a year from detonation, the pieces should miss quite nicely. It would be like someone shooting at you with a shotgun from 1km away (with buckshot). The debris you will be hit with, and even the chance of being hit at all, goes way down. And if you options are 'get hit with a gigantic asteroid' or 'get hit with the collective half of said gigantic asteroid', the latter is still your better option, because your getting hit with less, and increasing the effectiveness of the earths atmosphere as a device to incinerate incoming objects (even if every pieces hits you, there will still be a more favorable ratio of asteroid converted to dust just by breaking it apart).

I actually like the idea of heating up one side to make the asteroid generate some thrust of it's own. Just saying, fragmentation makes things better, not worse (I am also considering that a bunch of pieces wiping out several major population centers is still favorable to one big piece causing an extinction level event).

[Joshington]

Just call Bruce Willis, he'll take care of it.

[AngelLestat]

If you can solve the issues of Nukes being heavy, and that you would need to embed them in the asteroid to make them truly effective (I think, seeing as a vacuum leaves to medium for the concussive force to act through), then fragmentation should be extremly effective. Sure, you might still have pieces large enough to make impact through our atmosphere, but unless the asteroid was so massive that it's gravity could hold the debris together in a group, then the pieces will drift away over time. Earth is not that big, so I would think that even given just a year from detonation, the pieces should miss quite nicely. It would be like someone shooting at you with a shotgun from 1km away (with buckshot). The debris you will be hit with, and even the chance of being hit at all, goes way down. And if you options are 'get hit with a gigantic asteroid' or 'get hit with the collective half of said gigantic asteroid', the latter is still your better option, because your getting hit with less, and increasing the effectiveness of the earths atmosphere as a device to incinerate incoming objects (even if every pieces hits you, there will still be a more favorable ratio of asteroid converted to dust just by breaking it apart).

I actually like the idea of heating up one side to make the asteroid generate some thrust of it's own. Just saying, fragmentation makes things better, not worse (I am also considering that a bunch of pieces wiping out several major population centers is still favorable to one big piece causing an extinction level event).

You are wrong.

First, you cant fragment something some big like Gilly, and even if you do, the fragments would joint again, and even if they dont, now you have several asteroid to divert, becouse it does not matter if you have small fragments than vaporize in the atmosphere, the energy is the same.

The meteor that fall in russia vaporize at 23 km altitude. But the damage to the town was equal notice.

Tunguska meteor also vaporize in the atmosphere, but it calcined 2154km2 of area, and this was only by a meteor of 80m diameter.

Of course in a hollywood movies is more entertaining to solve any problem with explosions.

But this is not the case.

[Idobox]

The largest active nuclear weapon in the Us is the b83, weighing 1100kg for 1.2Mt maximum yield. That's about 5e15J.

If we're looking at something the size of Gilly, with a mass of 1e17kg, it could radically alter it. The escape velocity is only 35m/s, debris would not coalesce.

If a single b83 bomb collides with the target, buries itself a few meters deep, and explode ejecting let's say 10t of rocks with a 10% efficiency, you now have a projectile of 1e4kg with 5e14J of kinetic energy, which means a velocity of roughly 300km/s, and a momentum of 3e9 kg.m/s. If the target weighs 1e17kg (similar to Gilly), it gives a deltaV of 3e-8 m/s, so it would take a very large number of nukes to move a Gilly sized object.

It would work wonders on smaller objects though.

Now, painting. Assuming the object is pitch black, and you paint it white, and it around Earth orbit, so getting about 1kW/m² of sunlight.

Let's take Gilly again, it weighs about 1e17kg, and has a surface area of 2e9m² and a radius of 13000m, so a cross section surface of 5e8m². The paint would give at most a thrust of surface*intensity/c, in this case about 1.7kN.

deltaV would be equal to thrust * time / mass, so over 10 years, 5e-6 m/s.

If the paint weighs 1g/m² (roughly 1µm thick), you would need 2000t of paint.

If you had 2000t of nukes, and managed to use them like I calculated, you would get a deltaV of 6e-5m/s.

Personally, I would trust the nukes, even if you use less optimistic figures than me, because they are a mature technology. Spray painting an asteroid is something we don't know how to do.

And if you split the rock, it will be even easier to push the remainders away.

[lajoswinkler]

How does the radiation pressure change with the albedo of the surface impacted by it? Shouldn't the plan be to lower the albedo, i.e. darkening the body, so that the photons are absorbed and thus transfer the momentum more efficiently?

I actually thought of soot or perhaps carbon black which are very similar chemicals. They cling to surfaces because of their particle shape, and they're easy to disperse.

The density of such carbon is ~2g/cm3, but the bulk material, with all the air inside will be at 0.5 g/cm3 if highly compressed.

I don't know if anyone actually thought of that before. I might contact NASA over this, lol.

[Kryten]

Asteroids and especially comets tend to be very low-albedo already.

[lajoswinkler]

True, but only the darkest comets reach close to lamp black. Asteroids are mostly nothing special regarding the albedo.

Comets might be bombed to expose a different surface which would allow more or less outgassing which would change their course.

[rasheed]

Easy. blow an asteroid to like, 15000 tiny fragments though it doesn't be easy

[lajoswinkler]

Obviously nobody reads these threads. You can't blow an asteroid to pieces unless it's very small, and then it's simply not worth the trouble.

There is no weapon on Earth capable of disintegrating a rock the size of a mountain. Nuclear weapons might look amazing, but that's because of their luminosity and air pressure effects. They don't have the needed energy unless you drill a hole in the asteroid and detonate it there. Drilling holes in asteroid is not going to happen. It's pure Hollywood.

[Anton P. Nym]

If a single b83 bomb collides with the target, buries itself a few meters deep, and explode ejecting let's say 10t of rocks with a 10% efficiency, you now have a projectile of 1e4kg with 5e14J of kinetic energy, which means a velocity of roughly 300km/s, and a momentum of 3e9 kg.m/s. If the target weighs 1e17kg (similar to Gilly), it gives a deltaV of 3e-8 m/s, so it would take a very large number of nukes to move a Gilly sized object.

That's why I went with a variant of the ORION propellant charge instead of a weapon. ORION used shaped charges to direct roughly 50% of the yield at its propellant mass; what comes out is a cigar-shaped plume of ultra-hot plasma that strikes the pusher plate at (depending upon design) 20-30km/s. The momentum transfers to the pusher plate, which on crewed vessels (or uncrewed if the payload is fragile enough) is mounted on shock absorbers. These were required to reduce the impulse on a 4000T vessel from a lethal 100g down to 2g.

If you substitute the asteroid in for the pusher plate, well, you wouldn't see multiple-g of acceleration but you'd get much greater efficiency than a repurposed warhead. You'd still need hundreds, detonated over a period of hours at least, to do the job on a dino-killer sized rock, though, unless you got it really early. (Fortunately, ORIONs were designed to carry 800-1000 charges, though most would have to be used to get the ship to the target and back.)

-- Steve

[JakeGrey]

Obviously nobody reads these threads. You can't blow an asteroid to pieces unless it's very small, and then it's simply not worth the trouble.

There is no weapon on Earth capable of disintegrating a rock the size of a mountain. Nuclear weapons might look amazing, but that's because of their luminosity and air pressure effects. They don't have the needed energy unless you drill a hole in the asteroid and detonate it there. Drilling holes in asteroid is not going to happen. It's pure Hollywood.

How about punching a hole in the asteroid by kinetic energy, then? A hardened kinetic penetrator (and that's the most Freudian phrase I've typed in... well, ever!) combined with a rocket motor could probably do the trick.

[Mr Shifty]

How about punching a hole in the asteroid by kinetic energy, then? A hardened kinetic penetrator (and that's the most Freudian phrase I've typed in... well, ever!) combined with a rocket motor could probably do the trick.

Using Gilly again as an example, it is 26 kilometers in diameter. The largest rocket ever built, the Saturn V, is 110 meters tall. If you look at this figure of Gilly from the KSP wiki:

A Saturn V would take up about one pixel in that image. You aren't going to be drilling into the asteroid.

[WestAir]

The problem is we don't have any deterrent for an impact event. We have nothing that would stop a life-ending asteroid.

What about gravity tugging? We'd need warning decades in advance - when it's possible we may only spot the asteroid years in advance. What about nuclear deterrence? Besides the fact that a nuclear barrage will not stop an asteroid large enough to cause an extinction event, we don't have nuclear arsenal capable of leaving Earths SOI. We'd need to build loads of the largest rockets ever built to hit a target moving 6000 times its speed, and we'd need that capability installed and operational yesterday.

In short, if we ever came across an extinction-causing asteroid, we're ****ed.

[lajoswinkler]

OK, so I've talked to a friend of mine who's a lot more educated in physics than I am. Basically, the higher the albedo, the greater the pressure light induces to a surface. Therefore if you have a very dark body, you should increase its albedo, and if you have a very bright body, you should decrease its albedo to get the greatest delta p, and consequently, delta v.

As most if not every asteroid out there is quite dark, the potential solution would be to spray paint it with something bright. Perhaps very fine SiO2 or TiO2, though the latter would be far more expensive.

Edited September 29, 2013 by lajoswinkler

[Vaebn]

The image of Gilly certainly puts into perspective. However, here's another cool image:

I don't know how big Gilly actually is, but I stretched it's image so that it was 26000 pixels, wide, then made a 390 pixel hole in it.

A 390 pixel hole, simulates the crater made by the Sedan test in 1962. http://en.wikipedia.org/wiki/Sedan_(nuclear_test)

Keep in mind, that was the result of a 100 kiloton warhead, but an 1 megaton warhead would be considered today pretty average.

Keep also in mind that the dinosaur killer asteroid is though to have been about 13km in diameter, so talking about 26km is quite generous. 26km, means that something the size of Phobos (which is the bigger one of the two martian moons) is coming towards us.

Now that might not look much, however... it is actually visible. You have actually altered geography by doing that in a picture containing the entire thing. I actually find that pretty impressive.

In the Sedan test, 11 million t of soil were displaced. 11 MILLION t of rock and dirty rose vs the earth's gravity and fell again someplace which is not the crater. Now, it's almost impossible to find the speed this happened, but on Phobos, any of those that exceeded 11m/s would never return to it. Frankly, I am rather sure that all of it was much, much speedier than that (a jumping cat is speedier than that), so being ultra conservative, I wouldn't be surprised to learn that 10 million tones of material wouldn't return to the asteroid ever again.

At that point, all that rock is acting like a propellant, and the entire thing is just a fancy mass drive, nuke doing the driving.

And that's just the effect of 1 nuke. Obviously if we are talking about an extinction event, we ought to have no qualms to use, you know, ALL the nukes.

So imagine that hole, targeted 200, or 2000, or 20000 times. (2000 explosions ejecting, say, 50 million tonnes of, material each due to larger warheads would equal 50 billion tonnes of "propellant" ejected... right?) Imagine, nuke, after nuke, after nuke, slamming at near the same spot, each one creating a huge plume of material to space.

And that's what I mean with "nuke it until it goes away". Project Orion gives the right visual, but the numbers in wikipedia are VERY wrong to go by! Our nukes are a lot more powerful than that. Project Orion had to be survivable and not have the ship go boom, or even have the pusher plate ablate after hundreds of explosions. It was pushed only by a tiny amount of material which the nuke vaporized in its own container. In this case, we'd have no reason not to go balls to the wall, "we must move this NAO".

Now, there are some details regarding how fast that exhaust is (it only has to be faster than 11m/s to impart some change), but by plugging those numbers to one of those delta-v calculators and taking into account:

.

you are talking like we had to stop it completely. In fact we have to change its trajectory only by a very small fraction of % to make it miss. For example dV needed to make an asteroid that is 10 years away miss is approximately 0.02 m/s

I am sure that you'll find that we aren't nearly as powerless as a species!

Edited September 29, 2013 by Vaebn

[lajoswinkler]

So imagine that hole, targeted 200, or 2000, or 20000 times.

And this is where the idea falls apart.

[Vaebn]

You don't *have* to target the hole...

If the asteroid rotates, you can target any spot you like as long as it pushes at the right direction.

If the asteroid doesn't, you can target the hole to make a bigger hole, or anything else reasonably nearby.

I only said that to keep a certain mental aesthetic of a rock having a single designated "nuclear engine point".

You can of course just rain freely down on it without any sort of hole hitting obligation, as long as all explosions eject, ejecta the right way.

Edited September 30, 2013 by Vaebn

[lajoswinkler]

Even if you live to see ELE, you will not live to see even 100 bombs being launched. Such effort is so incredibly huge. I do not think the humanity can do it.

[WestAir]

[Let's nuke the asteroid!]

The ultimate problem is that we don't have nuclear arsenal capable of leaving Earths SOI. The idea looks great in power-point, but neither Russia nor the US can modify 20,000 nukes (or even just one) with SOI-leaving capabilities within any reasonable time-frame to be a worthwhile solution. They'd need to design, construct, and launch the largest ICBM rockets mankind has ever built, and they'd need to construct and build the infrastructure to do it.

We need all of that ready to go right now - not "when we realize an asteroid is coming." It's far too late at that point.

[Comrade Jenkens]

And this is where the idea falls apart.

As a species we have plenty of nukes. That's not particularly unfeasible.

Wikipedia: there are now some 4,100 active nuclear warheads and some 17,000 total nuclear warheads in the world in 2013

[lajoswinkler]

I have at least a quadrillion atoms of hydrogen in my left fist. It doesn't mean I can punch nuclear explosions around.

As westair said, we simply can't do anything with those bombs. It would be an incredible success if we could send one 1MT bomb beyond Moon.

Thousands of nukes sent beyond Jupiter? Come on, don't make me laugh.

We're going to die like rats on a sinking boat if something huge falls down from the outer regions of Solar system.

[Comrade Jenkens]

I'm pretty sure that people wouldn't say "hey theres a huge asteroid coming to wipe out all life on earth, lets not bother making any rockets to stop it"

If once was detected approaching that dangerous then unlimited funds would be thrown at the project.

[Klingon Admiral]

Using nukes against an asteroid is nothing short of insane, as there are a couple of alternative approaches already mentioned that would not result in disaster if the rocket carrying the probe failed during launch. We could even go for good, old kinetic deflection, just slam something very fast into this big, bad asteroid and watch as the chunk of rock alters it trajectory. A sufficiently fast object would contain more energy than even the largest of nukes.