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

[Aghanim]

If only Armaggedon have more scientific accuracy and all that critics stuff..... it have one of the best soundtracks ever in the movie history according to me

But to me, to stop an asteroid you need some nuke and a lot of it. Build a nice huge kinetic impactor using Orion drive, the technology is proven and if peoples want to chose between their extinction and some fallout you know it... Orion drive is the only proven tech that can lift several 20000 tons out of Earth surface, if only that test ban treaty doesn't stop it

[thunderstar]

bruce willis

[lajoswinkler]

I don't know why is everyone so focused on Armageddon. It was a ****ty blockbuster hundred times less accurate than Deep Impact, in both the scientific and other terms.

[Svenie45]

Was this a movie?

[NASAFanboy]

I don't know why is everyone so focused on Armageddon. It was a ****ty blockbuster hundred times less accurate than Deep Impact, in both the scientific and other terms.

True that.

Nuking it might not be a good idea. You saw what happened in Deep Impact. The rock split in two, and kept going, which forced the team to only go for one.

Why not landing probes on the side facing Earth, and have them drill into the rock while ejecting the dust and dirt at Earth, which would act like a propulsion system, forcing the rock to slow itself. Hell, why not slowly send it to lunar orbit, and mine it from there?

[Nuke]

idk, a 30 year stream of cold war surplus nukes plus whatever else we managed to produce might make an earth sized dent in its trajectory, and probibly solve nuclear disarmament and energy problems in the process. probibly need to retrofit a lower stage to existing mirv missiles, and upgrade the warheads with a maneuvering unit of some sorts.

then again if you cant move it with nuclear ablation, you could probibly use nuclear ablation to smash another more manageable object into it.

[brdavis]

Aww, so the spray painting is a no go.

Actually, spray painting it is probably the best (or second best) solution.

I've not read all of this (sorry), but thought I'd throw my two cents in - I'm teaching this stuff in my 100-level astro class on Wednesday, so… I've got some background.

First, the damage is done by the kinetic energy deposited upon impact. That doesn't matter if it comes in as one chunk, or one billion - the energy deposited is the same. So "gravelizing" it doesn't help - even if you vaporized it and the gas was what was hitting the Earth, you haven't made the mass go away… so breaking it up doesn't help.

Worse, a single impact superheats one point on the Earth's surface, but a lot of that energy is radiated back into space (because the impact zone is so hot, this outward radiation is efficient. But if you are hit be the same mass spread out, the impact temperatures are lower (same energy, larger area), so it's less efficient at radiating. Net result? Turning it to gravel makes the problem far worse, not better. Think "atmosphere on half the planet glowing horizon to horizon for several minutes to tens of minutes at the same temperature as the Sun". Bar-b-que anyone?

Worse still, the asteroids we have good data on have in general low density; less than rock. So most of them (larger ones, anyway, 100's of meters to kilometers and up) are probably more like gravitational bound gravel piles. If you don't want them to fragment, you probably need to be very gently with your pushes. Surprisingly, a stand-off nuke can do this: the blast in space is essentially a very high-intensity radiation front (in the gamma region without an atmosphere to interact with). When that radiation hits the surface, it flash heats and spalls the surface on the side facing the detonation. Those spalling debris push uniformly on the asteroid as a whole, so it's like a giant catchers mitt. If you are careful (not too close, not too far), and the asteroid isn't too weak, this might work… barely.

Note that using a nuke to deflect a smaller object (smaller asteroid) unto a collision course does get you more bang for the buck - you are using a small delta-v to direct an already large momentum onto a collision course, taking advantage of that pre-existing momentum. But… you are likely hitting a gravel pile with a bullet (or another gravel pile) - see hemispheric bar-b-que above.

Second… and really as KSP players we should know this… if you want to miss a rendezvous, you don't thrust sideways, you thrust prograde or retrograde… either one… to change the semi-major axis, and the orbital period. All you have to do is delay the impactor by 4 minutes. That's it. At an orbital velocity of 30 [km/sec], Earth moves its own radius in about 4 minutes. So if the impactor is headed straight at us, all we have to do is slow it down slightly or speed it up (yep, adding to its kinetic energy is just as effective here). By a tiny bit. Let's say you change the orbital period as a near-Earth asteroid by 10 seconds (one part in 3.1 million… I don't think the maneuver nodes will let you do tuning this fine ). That means it will be perhaps 10 seconds "late" for it's Earth-orbit-crossing on the first orbit, but 20 seconds late on the next one, and 30 seconds late on the third… if you had a lead time of 30 years, that's more than sufficient.

As to actual mechanisms… look 'em up. Asteroid deflection strategies have a long history in the technical literature… and yes, one of the better ways (as in low-mass, low tech, quick to implement) is the Yarkovsky effect. It's not direct "light pressure" on an asteroid (look it up on Wiki, it has to do with the rotation of the asteroid as well as the albedo and surface heating), but it is a significant effect for asteroids in certain size ranges. And it doesn't take a lot of "paint" - try chalk dust wrapped around a stick of dynamite. Approach trajectory on the surface, expand the dust curtain before impact so it coats a large spot on the surface, and let Yarkovsky do the driving. Ironically you probably don't know how the orbit will change… but if it's on an impact trajectory, you don't really care. Any change in the orbital parameters will result in an impact becoming a miss… in, out, faster, slower. So for a validated impactor, just make any change to the orbit possible… essentially, it can't get worse.

A "gravity tug" (spaceship that hovers near an asteroid, very very slowly changing the asteroids orbit due to gravitational interactions) is another possibility… if you can keep a 'tug' working for years or decades. A solar sail (or, better yet, a mirror gravitational bound to the asteroid, but reflecting light onto the surface and strongly heating one point) is another one, but requires control over long periods of time. Nukes you need to detonate at the right standoff, and hope the asteroid is strong enough to take the "push". Mass drivers sitting on the surface are great, year-after-year throwing stuff away in a single direction… but are working mechanical nightmares that have to mine the surface ("Dear Jeb, welcome to your decade-long maintenance job… PS, if you fail everybody dies, but we have a great retirement package").

Chalk dust may not be as sexy as Bruce Willis… but it will get the job done

Incidentally all this depends on size and lead time - the longer the lead time, the better off (more options) you are. If all you have is a single orbital period, we're probably in very very deep trouble. But if you find things a long time in advance, very simple solutions start becoming practical. For small objects (on the order of 10 meters to perhaps 100 meters) moving everyone out of the way on the ground below is probably the best bet (again, assuming you know they are coming). Above 100 meters into the 1-10 kilometer range, it's time to do some very serious mitigation. Above 10 kilometers, roughly speaking, start planning end of the world parties, maybe to watch the select 100-400 land on Mars (Phobos would be better, but probably not long-term). Above 10 kilometer… well, I'm not going to worry about it

As for "moving asteroids is too hard, let's move the Earth out of the way"… um, what are you thinking? No. No no no no NO.

Sorry for the tl;dr

--

Brian Davis

[czokletmuss]

For small objects (on the order of 10 meters to perhaps 100 meters) moving everyone out of the way on the ground below is probably the best bet (again, assuming you know they are coming). Above 100 meters into the 1-10 kilometer range, it's time to do some very serious mitigation. Above 10 kilometers, roughly speaking, start planning end of the world parties, maybe to watch the select 100-400 land on Mars (Phobos would be better, but probably not long-term). Above 10 kilometer… well, I'm not going to worry about it

Well, OP is talking about 250km rock coming from the deep space (outside of our system), so... Apocalypse BBQ anyone?

[Sochin]

Look this isnt Armagedeon or Deep Impact this is reality. You are not trying to avoid a meteorite but a small planet which is a vastly different kettle of fish. We have nothing to avoid this, and nothing that would help us in a 30 year run up. Our only hope is if Jupitor or Saturn caught the object. You do not want the moon taking the hit as this would vastly affect our orbit, poles (stability), seasons and would throw up considerable debrie that would more than likely get trapped around us or worse hit us.

[Sochin]

And another thing, the way Skywatch and its replacement programmes is at the moment I doubt we would see it comming untill its far too late.

[brdavis]

Look this isnt Armagedeon or Deep Impact this is reality.

Well, not exactly .

There are going to be dang few 250 [km] objects coming in from anywhere. So, the premise itself isn't very realistic (and the discussion it generated is interesting). In the last 3 billion years, there's little evidence for impactors an order of magnitude less than this. The reality is this isn't a realistic situation.

You do not want the moon taking the hit as this would vastly affect our orbit, poles (stability), seasons and would throw up considerable debrie that would more than likely get trapped around us or worse hit us.

Actually, let's run the numbers. Assume the 250 [km] diameter object has a density of 3000 [kg/m^3] (high, but not bad). The mass would then be 2.45e+19 [kg]… the Moon is 7.34e+22 [kg] - about 3,000 times more massive. If the interstellar interloper was on a head-on collision course with the Moon, the impact velocity would be at best (highest) around 74 [km/sec] (42.2 for Vesc at 1 [AU] + 30 for Earth's orbital velocity + 1 for the Moon's orbital velocity relative to Earth). So, let's see, delta-v for the Moon post-impact you can get through momentum conservation: it would be around 24.7 [m/s]. So you would reduce the Moon's orbital velocity, at best, by about 2%. You're not de-orbiting it. You're barely changing it's orbit at all. If it was in a circular orbit 384,400 [km] in radius before, the new semi-major axis is 366,829 [km], and the new period would be just 93% of the old one… if it took 27.3 days to orbit before, it would take 25.4 after the impact.

It wouldn't affect our orbit at all. Nor our seasons. It would throw up one heck of an ejecta cloud, and it wouldn't even remain in the Moon's orbit around the Earth (ejecta velocities would be more than sufficient to put it on Earth-crossing trajectories). But considering the tiny tiny size of the Earth relative to the volume the debris would be spread through, it might not be fatal (but it would make for a very interesting next few of million years as the ejecta is re-accreted on the Earth and Moon).

[Kilmeister]

http://news.discovery.com/space/asteroids-meteors-meteorites/top-10-asteroid-deflection-130130.htm

I'm thinking the last slide is the answer.

[jwenting]

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.

Actually, nuclear warheads have been getting smaller and smaller for a long time, as they got more accurate.

The typical one in the US arsenal is the B61 gravity bomb with a selectable yield between about 1KT and 500KT. The larger ones like the B83 are or have all been decommissioned.

There are I think still 1MT warheads on the few remaining Minuteman missiles, but good luck getting one of those 50 year old beasts to launch (I seriously doubt even the USAF thinks more than a fraction of them will leave their silos if lit off).

The Soviets and Chinese have bigger nukes in the several MT range, but they're not going to help. They're going to see a strategic opportunity when the US diverts its arsenal to fending off asteroids.

[PakledHostage]

I'm thinking the last slide is the answer.

If by that you mean the one below, then I agree wholeheartedly. Let's hurl Ron Ford at it...

[Kilmeister]

If by that you mean the one below, then I agree wholeheartedly. Let's hurl Ron Ford at it...

Lol

I think that's too much rock for him to smoke, but worth a shot!

[czokletmuss]

If by that you mean the one below, then I agree wholeheartedly. Let's hurl Ron Ford at it...

Holy crap, the asteroid is already here!