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

[WestAir]

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.

The problem isn't our willpower to do anything, it's our capability of doing something. If we discover, tonight, that a 3km sized rock will hit Earth in 6 weeks (a VERY believable time-frame, considering the usual time-frame we discover certain asteroids), I'm sure the Presidents of Russia, China, and the US, along with our allies in both NATO and the UN will approve any measure to stop it with a blank check of trillions of dollars.

The bleak problem is there is absolutely nothing we can do with the worlds resources to stop an impact event. We can design and build those rockets, but we certainly couldn't build enough or even find the right window of opportunity before an impact. We'll die with the ICBM's on the launch pad.

But at least we tried, right?

[lajoswinkler]

Isn't 6 weeks a bit too short for such a large lump? Its brightness should be enough to detect it at least a year before impact if it's coming from the direction away from the Sun.

Unfortunately even 10 years is not enough. We might have a fighting chance if we discover it a quarter of century before ELE.

6 weeks is not enough for building basic shelters for a small number of people. I think we can easily predict the total collapse of global economy if that happens. Hardly anybody would want to work anymore and law and order would cease to exist. Lots of people would be killed even before the big day and all that scares me more than the impact itself.

[Klingon Admiral]

And even if, human civilization (or at least the human species) could quite possibly survive an 3km asteroid impact.

[MBobrik]

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.

sorry to rain some gamma photons on your parade but the radiation pressure effects are just too weak to make a difference.

for example :

Golevka is a small object, measuring 0.6 × 1.4 km. The radar observations revealed that it has a very strange, angular shape that looks different depending on the direction. In 2003 the Yarkovsky effect was first observed at work by high-precision radar observations of Golevka.[2] Between 1991 and 2003, the small force of the Yarkovsky Effect caused a shift of 15 kilometers (9.4 miles) from what would be expected based on only gravitational interactions.[2] This helped evaluate the asteroid's bulk density (2.7 ± 0.5 g/cm³) and mass (2.10×1011 kg).

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15 km trajectory change over 12 years. That is pathetic at best. Even if you painted the asteroid all white and cranked the effect up by an order of magnitude you would need over 500 years to make it miss ! And that is just an ~1 km asteroid. if we are threatened by an 15 km one, just like the one that did the dinos in, its surface ( and thus radiation pressure ) will go up 15^2 times, but its mass 15 ^3 times, so the net effect will be 15 x less. so now we are talking about 7500 years needed to make it miss...

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Not to mention the fact that the amount of paint needed to cover the ~650 square kilometers of its surface would be far heavier than all the 13 K nukes we've got, put together.

Edited September 30, 2013 by MBobrik

[MBobrik]

Unfortunately even 10 years is not enough. We might have a fighting chance if we discover it a quarter of century before ELE.

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I think 10 years would me more than enough to mass produce say several dozens of Ariane 5 rockets and start lobbing the nukes.

[Klingon Admiral]

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I think 10 years would me more than enough to mass produce say several dozens of Ariane 5 rockets and start lobbing the nukes.

Instead of launching the warheads torwards the asteroid, we should build an Orion drive in orbit and launch the Orion drive torwards the asteroid, a directed kinetic impact should be much more effective than a explosion.

[Mr Shifty]

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I think 10 years would me more than enough to mass produce say several dozens of Ariane 5 rockets and start lobbing the nukes.

1) You'd need the warheads to be at the asteroid ASAP. The closer it gets, the harder it is to deflect. Hohmann transfers to Saturn take 7 years; to Jupiter 2.7 years. You can't take 10 years to build rockets; you need to launch yesterday.

2) Ariane 5 has a max capacity of about 10.5t to GTO. Large yield (10-15 Mt) warheads run about 10t in weight, just for the warhead -- not including delivery vehicle. So Ariane 5 has no capability to deliver warheads to interplanetary space. In fact, there are no rockets currently in use that could do so.

[Anton P. Nym]

A sufficiently fast object would contain more energy than even the largest of nukes.

The trick, of course, is to get something moving that fast... which may (likely will) take more energy than released by even the largest of nukes. For a sense of scale, the Saturn V rocket stack as a whole "only" had the same amount of energy as a small-ish tactical nuke.

The energy's gotta come from somewhere, and so far the biggest (literal) bang per buck or ton we can get comes from Our Friend the Atom.

-- Steve

[MBobrik]

we should build an Orion drive in orbit and launch the Orion drive torwards the asteroid, a directed kinetic impact should be much more effective than a explosion.

totally wrong. the orion drive is just detonating nukes to push an object. and if you push another object first, which subsequently collides with the asteroid, it is bound to be less efficient than to apply the same kick directly to the asteroid itself.

[lajoswinkler]

Aww, so the spray painting is a no go.

I still think we'd be doomed even with 10 years of time before impact.

[MBobrik]

1) You'd need the warheads to be at the asteroid ASAP. The closer it gets, the harder it is to deflect. Hohmann transfers to Saturn take 7 years; to Jupiter 2.7 years. You can't take 10 years to build rockets; you need to launch yesterday.

10 year time = ~ 0.02 m/s dV needed

5 year time = ~ 0.04 m/s dV needed

2 year time = ~0.1 m/s dV needed

and so on

and so on. so when we spend first 4 years manufacturing launchers, building the ( nuclear powered ) interplanetary stage in orbit and hauling nukes, and 4 years flying the contraption to the asteroid, the dV required is still achievable

2) Ariane 5 has a max capacity of about 10.5t to GTO. Large yield (10-15 Mt) warheads run about 10t in weight, just for the warhead -- not including delivery vehicle. So Ariane 5 has no capability to deliver warheads to interplanetary space. In fact, there are no rockets currently in use that could do so.

the W87 warhead weights 270 kg max. and we can strip all the reentry and targeting related stuff from it so it will be more like 250 kg and its yield is 300 kt so 10.5/0.25 = 42 warheads per one Ariane 5. that is a lot of nukes.

not to mention the fact that the Ariane does not need to fly the nukes all the way to GTO. It will fly to LEO where the interceptor will be assembled. so that is more like 84 nukes per 1 Ariane 5

Edited September 30, 2013 by MBobrik

[Klingon Admiral]

the W87 warhead weights 270 kg max. and we can strip all the reentry and targeting related stuff from it so it will be more like 250 kg and its yield is 300 kt so 10.5/0.25 = 42 warheads per one Ariane 5. that is a lot of nukes.

But we should take into consideration that only maybe 40% or something of the yield will be usable, the rest will simply miss the asteroid.

[nuclearpower13]

Theoretically we could. The history channel show "The Universe" did an episode on this in which they described several methods that we could use currently to prevent an impact event with earth.

1. The Gravity Tractor: Considering most of the asteroids that present a threat to earth are very small much smaller than the asteroid Eros. A space craft with enough mass put in a relatively close orbit around the sun near the orbit of said asteroid. The gravity of the space craft could slowly tug the asteroid to a small orbit change that would prevent the asteroid from impacting the earth.

2. Above Surface Nuclear denotation: Now I know this sounds like the solution from the famous Micheal Bay file Armageddon but hear me out. Now we launch a nuclear weapon into space on a collision course with the asteroid. Before the bomb hits the surface the weapon is detonated 100-500 ft above the asteroid. The immense amounts of heat generated by the explosion would vaporize surface material (Water Ice, Frozen Methane, rock and etc.) and the thrust generated by the vaporization of said material could propel the asteroid in a different direction and move it into a different orbit.

3. Surface Impact: Now this is quite simple. You could launch anything that has a small mass at the asteroid at a high velocity and the impact won't split the asteroid into many pieces due to a small mass. But the eject a that is ejected from the asteroid will again create thrust and propel the asteroid in a different direction and change the orbit.

[Klingon Admiral]

3. Surface Impact: Now this is quite simple. You could launch anything that has a small mass at the asteroid at a high velocity and the impact won't split the asteroid into many pieces due to a small mass. But the eject a that is ejected from the asteroid will again create thrust and propel the asteroid in a different direction and change the orbit.

Not necessarily the eject, conservation of momentum is the magic word.

[Technical Ben]

The Moon.

[i'm pedantic like that. ]

[Brotoro]

If the object is really large and we have short notice: We are screwed.

If the object is really large and we have long notice: Probably can't shift its orbit in time...so build colonies off of Earth.

If the object is small and we have short notice: We'll have to take the hit, probably. And, no, an ocean impact is not necessarily preferable because you could kill more people with tsunamis that would die in a land impact.

If the object is small and we have long notice: Many options...the longer lead time, the better. If the object is not fragile, nearby nuclear explosions can ablate the surface of the rock and shift its orbit in relatively short time. If the object is a "rubble pile" asteroid, nukes would just turn it into lots of smaller pieces to hit us...not good...so we would need to shift it with the small gravitational attraction of a ship station keeping near the asteroid.

Very small objects can be deflected with laser batteries (assuming we bother to build them ahead of time)... And because of the very short notice you get on tiny objects, other methods wouldn't suffice.

[Technical Ben]

The atmosphere.

[i'm still being pedantic... sorry! ]

[Brotoro]

I don't mind people being pedantic...I just don't understand what you're attempting to be pedantic about.

[Keldor]

Breaking an asteroid into small pieces would generally improve the situation for a very simple reason: the atmosphere will absorb much more of the enery from the fragments. The reason is simple. Drag is proportional (more or less) to surface area, and by breaking up the asteroid, you increase the surface area. Make the pieces small enough, and they will end up impacting the ground at around terminal velocity.

The question then is how much energy the atmosphere is capable of absorbing before turning into an oven and baking us all. From what I've read, the big extinction events are not caused so much by the impact as by the dust kicked up into the air. This suggests to me that for a reasonable sized impact - certainly for anything small enough to actually be blown up - that dispersing the energy into the atmosphere would be the best option.

Mind you, if you broke it into fairly big pieces, then instead of say one 3 km asteroid, you could end up with 20 1 km sized ones, which would not be an improvement, since they are still big enough to retain most of their energy through the atmosphere, and since blast radius is proportional to the cube root of yield, the overall area directly destroyed would be much greater.

Anyway, nukes would be the best way to try to redirect an asteroid, since they have the highest ISP by far of any reaction we're capable of creating. The larger yield ones would be best, since the key to making a more powerful nuke is not so much making them bigger as getting the plutonium compressed as much as possible in the first microseconds of the explosion. This gives rise to things like two stage nuclear warheads, where you effectively have a small nuclear explosion just to compress the second stage of plutonium, thereby giving a much more powerful overall explosion.

During the 1950s, when the nuclear arms race was focused on yield, you had monsters like the Soviet Tsar Bomba, which theoretically had a yield of up to 100 megatons, though the version that was actually tested had been modified to reduce fallout, and "only" had a yield of 50-60 megatons.

More modern construction techniques have reduced the weight of bombs, with the highest effeciency at around 5 megatons TNT/ton bomb weight. Back of the napkin calculations tell me that oxigen+hydrogen rocket fuel has 3-4 times the energy density as TNT, so a nuke should produce on the order of (assuming 50% of the energy hitting the asteroid) an ISP on the order of 250,000,000s.

For launch systems, the Saturn V would have about what it takes to launch a high yield nuke to the asteroid. They built 15 of them in just 6 years, for the cost of a single launch being about 1 billion of todays dollars, but if you were to turn the whole global economy into making them (and if you knew of a massive asteroid coming at the earth, you would!), I dare say you could produce upward of 1000 per year, or perhaps even considerably more with mass production.

Given a large amount of head time, you could definitely deflect an asteroid of significant size. The real problem would be calculating the orbit of said asteroid accurately enough to know it was going to hit you. If you get that wrong, then at best, you just wasted an unimaginable amount of resources. At worst, you could deflect the asteroid from an orbit that just misses into one that actually hits the earth.

[Spica]

Assuming the potential impactor is a comet, I would launch a HUGE space-based laser and fire it at one of the poles of the comet so it will outgass in that direction, letting the comet push itself, or you could use a giant parabolic mirror. That reduces the total amount of stuff you need to launch (I.E. Nukes) to only the laser or the giant mirror.

Spica

[Klingon Admiral]

Anyway, nukes would be the best way to try to redirect an asteroid, since they have the highest ISP by far of any reaction we're capable of creating. The larger yield ones would be best, since the key to making a more powerful nuke is not so much making them bigger as getting the plutonium compressed as much as possible in the first microseconds of the explosion. This gives rise to things like two stage nuclear warheads, where you effectively have a small nuclear explosion just to compress the second stage of plutonium, thereby giving a much more powerful overall explosion.

Aren't the most powerful nukes fusion bombs, which use a traditional fission nuke only to provide the energy to start the nuclear fusion? The Tsar was one of these.

[Technical Ben]

I don't mind people being pedantic...I just don't understand what you're attempting to be pedantic about.

That in all honesty the solar system around us is better at clearing our "local neighborhood" (the technical term?) than we are.

Jupiter. Is another example of a large planet that actually "clears up" wandering rocks. But we also have the atmosphere and the moon as well. Why take note of these? As any action we take is possibly insignificant in relation. Not that we should not try, or should not take notice, but that we should look at how things already work to prevent, or does not create, such events. Our current setup of planets is rather stable. It's not like were being thrown planet killers every 5 mins.

Statistical analyses of how many events in the past, do not help us know how many events in the future will happen, if the current mechanism is progressive. We already know the "early bombardment" period is past. Are we past the "planet killer" period?

[andrewas]

Yes, Jupiter, the moon and various other bodies tend to perturb objects that would otherwise hit Earth. This conversation is about the exceptional body that is on the perfect trajectory to actually hit us. Jupiter deflecting 99% of all asteroids does us no good if the one that gets through is massive enough.

Also, theres no natural end to the 'planet killer' period - we'll never run out of asteroids large enough to cause major damage. Sooner or later one of them will hit us. Hypothetically, if we got into asteroid mining in a big way, we could locate and control all threatening asteroids as part of the mining process. But, right now, it doesn't look like we'll ever bother with anything off Earth again, so we're going to have to stop one of them on relatively short notice or go extinct. And even in the best case, where off-world industry generates the infrastructure to easily detect and redirect and threatening asteroid, there's always the slim chance of something coming in from the Oort cloud on an impact trajectory. Consider C/2013 A1, which came from nowhere and will pass very close to Mars. Its estimated to be about 4Km across and will pass at 56Km/s - a similar rock on an impact trajectory with Earth would kill everything on the planet.

[Technical Ben]

While no doubt true, it's still and assumption that is being used to get to that conclusion, not an observation/tested claim. At least as far as I can tell. Which "begs the question" as to why people are pursuing the resources to put together to build such things.

Discussion of a hypothetical is one thing. Asking for application to it, is another. I'm all for applying safety measures for car seats, we can make observations of those things, and can be certain we are driving cars that may crash. I'm not sure we can be certain an investment in asteroid killers will ever be needed, or even succeed in paying off.

Going to space for excitement, exploration and knowledge do pay off though, we can be certain of that.

[Keldor]

Aren't the most powerful nukes fusion bombs, which use a traditional fission nuke only to provide the energy to start the nuclear fusion? The Tsar was one of these.

Fusion bomb is actually sort of a misleading name for large thermonuclear bombs (thermonuclear is also misleading, since you want to minimize heat for as long as possible to allow the fissile materials to compress further). In actuality, they use both fission and fusion, each complementing the other.

Generally, the purpose of the fusion component (tritium and lithium-6 deuteride ) is to release a large quantity of neutrons, which serve to accelerate the fission of the various uranium and plutonium components of the bomb. (It's a bit more complicated than that, if you want to read up on it, check here). The fission usually releases the majority of the energy.