Air Bags for Planetary Defense

Gallowglass writes "The Canadian paper, the National Post, is reporting on a plan to divert asteroids headed towards Earth. According to the story, the proposer, a Dr. Hermann Burchard, suggests deploying an inflatable mylar bag a few kilometers in size, and using it to push the projectile aside. An air bag for earth? The deployment mechanism isn't detailed in the story."

Comments

Ahh

[Anonymous DWord]

So that's why Chretien's retiring.

Further research.....

[Anonymous Coward]

...shows that smaller asteroids may experience neck injuries or even death from the fast deploying air-bags.

Nobody abolished Newton's laws...

[WetCat]

So if this air bag hit the asteroid - the misery weight of that air bag against asteroid weight send that air bag with all constructions in it flying with very high speed, while asteroid will fly with almost unchanged path...

--
Newton laws are guarded by Newton Police
(City of Newton, KS)...

Re:Nobody abolished Newton's laws...

[mcfiddish]

The article wasn't clear on how the air bag will apply pressure to the asteroid. Maybe a slow, controlled leak?

Re:Nobody abolished Newton's laws...

[darkwiz]

I think the idea would be to make some attempt to match it's speed, then contact and start the engines firing to push it off course.

Rather than think of it like a car's air bag, think about it as a way to spread out the pressure along the surface of the object. A rocket on the surface of a comet or loosely bound asteroid may just disintegrate the parts, yielding little benefit.

Which is more comfortable to sleep on: a pillow or the blunt end of a pencil?

Re:Nobody abolished Newton's laws...

[billbaggins]

I think the idea is to catch it far enough away that an "almost unchanged" path is changed just enough to miss the earth. After all You may think it's a long way down the street to the chemist's, but that's peanuts to space - the earth is actually a pretty small target, and a relatively small deflection, applied far enough out, would be enough to make a potentially deadly rock go whizzing right by.

Re:Nobody abolished Newton's laws...

[jerryasher]

The air bag is subterfuge. NASA is really planning on creating a blamange and letting the Brits eat the damn thing. I saw a documentary on this a long time ago.

Re:Nobody abolished Newton's laws...

[Chris Burke]

I guess it depends on whether it is a rocket-propelled pencil or not. :)

I've heard worse ideas

[drinkypoo]

If the asteroid is small enough you could even use the airbag to skip it off the atmosphere. I have a hard time envisioning some airbag attached to a rocket motor doing much to a larger one in time.

Re:I've heard worse ideas

[geoswan]

If the asteroid is small enough you could even use the airbag to skip it off the atmosphere.

Let me see if I understand what you are suggesting here. We launch a rocket with a big balloon on board. The rocket rendevouses with the asteroid, matches trajectories, lands, and the balloon is deployed. Have I got this right so far?

Then, when the asteroid is about to enter the Earth's atmosphere, the balloon causes it, instead, to bounce off?

Do you know how fast NEO would strike the Earth? I looked this up this summer, when 2002 NT7, the 2 kilometer rock caused a scare when it was thought there was a remote chance it might strike Earth in 2019. It would have struck the Earth at 28 kilometers per second. The NEO that would have struck at the slowest velocity was still 5 kilometers per second.

I don't believe your balloon would survive an impact with the upper atmosphere at 5 km / second, even if it didn't have multiple tons of asteroid behind it.

The Tunguska event of 1908 was caused by the impact of an NEO of about 50 metres in diameter. It caused an airburst equivalent to 16 million tons of TNT. Would an asteroid that size be worth trying to divert, if we detected it with plenty of lead time?

A rock that size would mass something like 40,000 tons.

safety first

[cheebie]

Does this mean children under the age of twelve shouldn't be allowed in the front seat of planet earth?

I had to read the article twice

[3ryon]

to try and figure out how an airbag is supposed to do anything to deflect an asteroid. I eventually inferred that the airbag is like a catcher's mit, connected to huge rockets.

The article could have been titled, "Huge rockets could deflect an asteroid" ....duh.

I think I would still prefer nukes....they're just so much more macho.

Re:I had to read the article twice

[Sabalon]

The idea is not to bounce it off the airbag. The idea is to use the ship/rocket to push the astroid and the catchers mit to gently hold the astroid while pushing it.

Think of it this way. Someone using a lot of force pushing you away with a pin point hurts. Someone using the same amount of force pushing you away with a pillow is much nicer.

Airbag? I believe this is the wrong word.

[redhotchil]

Using the word "Airbag" for this idea definitely gives people the wrong idea. An airbag is used usually to reduce the impact of a fast moving object. In the case it is used as a deflection mechanism. Perhaps the word deflection ballon would be a better combination word?

Just a thought.

Re:Airbag? I believe this is the wrong word.

[El]

More like a big baseball mitt, actually.

Easily misunderstood

[El]

The problem the author is trying to solve is: How do you get a grip on an asteroid for long enough for your rocket motors to change it's path without causing the asteroid to break up. He's suggesting using a giant pillow between engine and asteroid to destribute the force.

This is the wrong problem, in my opion; he assumes you've got massive amount of rocket fuel to wast. What we really need to do is figure out how to take some of the mass of the asteroid and accelerate it, using this as the reactant to change the path. Sort of like installing a rail gun on the asteroid, and firing off bits of asteriod like b-b's to get the asteroid to move in the opposite direction.

Re:Easily misunderstood

[Christopher Thomas]

What we really need to do is figure out how to take some of the mass of the asteroid and accelerate it, using this as the reactant to change the path. Sort of like installing a rail gun on the asteroid, and firing off bits of asteriod like b-b's to get the asteroid to move in the opposite direction.

Or haul a bigarsed ion drive over to it, and use charged silica vapour as the reaction mass. Bring spare ionization screens...

I'm still in the "nuke it" camp, myself.

Re:Easily misunderstood

[Christopher Thomas]

Why not just shatter the asteroid? Seems like that would take less energy than either your or his sugesstion. Let the atmosphere do the work, just break it up is chunks that are small enough to ablate down to non-threatning pieces.

The problem is that most asteroids large enough to be a problem would cause serious problems even raining down into the atmosphere as gravel. Large volcanic eruptions mess up our climate quite nicely; vapourizing a few billion tonnes of rock on re-entry would have much the same effect.

What you really have to do is fragment the asteroid with enough force that the pieces all have local escape velocity [from the asteroid], and do it far enough back in its orbit that most of the pieces miss Earth [the hard part, as we'd need months to years of advance notice].

This is still probably the most practical way of dealing with an Earth-threatening asteroid.

Re:Easily misunderstood

[istartedi]

You have to be really careful about that. Do it wrong, and you send thousands of white-hot rocks down into the middle of California in the middle of July. Oops! Just kindled all the redwood forests.

If the asteroid is big enough, you could even heat the atmosphere and/or spread enough space dust around to influence the weather in wierd ways. That's not as bad as sending a 1000-foot wave around the Pacific rim, but it's still less than optimal.

That said, it would be nice if we had enough lead-time to send up something that could pulverize it into little chunks and disperse them widely enough to create a nice annual meteor shower.

The question you have to ask for all this is: How long would it take us to turn a planet-killer into lots of little pebbles and scatter them widely enough?

Also, how much energy would that take, and where would it come from? I wager the answer is "a lot" and "from nothing we have right now".

I think the most practical answer for the time being is going to be "nuke it". Of course that won't turn it into pebbles, but hopefully the chunks will split wide enough to miss us.

Lead time is everything. We really need as much effort as possible going into detection so we can get as much lead-time as possible. 50 years lead time and we can mine the thing. 5 days lead time and we are the next dinosaurs.

Re:Easily misunderstood

[PleaseDontBeTaken]

Isn't that really the same problem? If you are bringing your own power, in whatever form, you have a finite amount of energy you can expend in whatever combination you want to change the momentum of the asteroid. Your solution sounds slightly better because after the first shot, the remaining asteroid would have ever so-slightly less mass. But when you consider the problem of mounting a rail gun on some asteroid in a stable fashion...well, the combination of rockets and the super-pillow sounds a lot easier, which counts for a lot when you are a million miles from the nearest astro-workshop and the clock is ticking.

Of course if you can use external sources of energy, like solar energy (i.e. the solar sail) or asteroid itself, then you really solve one problem. But whatever your solution, if it is really to solve the problem, it also needs to have a rate of work sufficient to deflect the trajectory in the time you have remaining. If the asteroid is big enough to matter, let's hope we have lots of leadtime.

Re:Easily misunderstood

[Bingo Foo]

Back when "Armageddon" was stinking up theaters nation-wide, I did a calculation in Mathematica using parameters given in the movie, e.g. "Half the distance to the moon," and "the size of Texas," etc., always giving that lovable band of roughnecks the benefit of the doubt and erring in their favor. For example I assumed that the asteroid had the density of water, that splitting the asteriod cost no energy, but separating the halves would require them to escape each other's gravity and just barely miss the Earth.

If I remember right, the feat they achieved would require the nuclear device they implanted to yield well over 10^40 Joules. More advance notice would lower this number greatly.

Re:Easily misunderstood

[MindStalker]

Water is denser than a lot of rocks. Either way check your calculations again. Not sure if I have a complete grasp on how man joules that 10^40 is, but 10^32 is the daily output of the sun. I have a hardtime beliving it would require more than this. Were you perhaps looking at the need for the 2 halfs to be accelerated instananiously or was it acceleration over time of the blast. Don't know if that makes a difference. Just think somethings gotta be wrong.

Re:Easily misunderstood

[Christopher Thomas]

everything comes back you know. nuking a asteroid heading towards earth is bound to have debris falling our way, and radioactive ones too.

It's far better to have 1% of the asteroid's debris cone hitting Earth than having the whole thing come raining down on us.

The environmental impact of any residual radioactivity from the nuke used to fragment it is far, far less than the environmental impact of the original strike (in the absence of interference), and probably even of the few chunks that still hit Earth.

Re:Easily misunderstood

[Bingo Foo]

I was assuming a delta impulse that pushed apart the two halves so that they would be separated by a distance equal to the diameter of the earth by the time they had traveled half of the lunar orbital radius. The biggest problem was the high speed of the asteroid (given in the film, I forget what it is) and the improbably short distance they gave, "half the distance to the moon." If you think about it, the problem amounts to instantaneously accelerating two rocks, each half of "the size of texas" to tens of thousands of miles an hour orthogonal to their path, so that it will miss the Earth in time.

The actual energy value I forget, but you're right that it would compare to something big like the sun's output. I think the only lesson learned is that we ought to have a plan worked out far in advance of ever using it.

Re:Easily misunderstood

[Christopher Thomas]

Aren't we talking about almost negligible gravitational forces from the asteroid itself? If escape velocity from the asteroid itself were an issue, I'd think we were screwed no matter what at that point, that thing would be really huge. :)

The escape velocity from asteroids is small (though non-negligeable). However, you're trying to impart it to a billion tonnes of rock. This makes the energy required significant.

Still quite do-able. My back-of-the-envelope numbers say the equivalent of a few kT is required (plus whatever is needed to actually shatter the rock, times whatever inefficiency factor you assume for force transmission).

Re:Easily misunderstood

[geoswan]

It's not that hard to mount a rail gun on an asteroid. Everything is basically floating, so you just have a drilling head on your mass accelerator (mechanically or magnetically accelerated buckets are less dependent upon asteroid composition than a railgun is).

And what if asteroids are just piles of rubble? If we are going to change its trajectory, aren't we going to have to pour in a huge amount of kinetic energy? Won't each bucketload of debris you fling off with your mass-driver send an asteroid-quake through your rock, or berg? A couple of years of asteroid quakes may shake your asteroid apart, so instead of having a pile of rubble, you have an uncontrollable cloud of rubble. What if it isn't a pile of rubble, what if it is an iron-nickel rock, but it has fault lines? Could enough asteroid-quakes totally fracture the asteroid into several chunks?

Push the nose against the asteroid and start chewing out bits to feed to your mass accelerator. Smaller accelerators on the side for attitude adjustment.

I wonder if you aren't glossing over several problems?

All asteroids that have come close enough for us to take a look at have been spinning. It is hard to imagine that they wouldn't be spinning. Were you planning to kill the asteroid's spin before you tried guiding it anywhwere? And how did you plan to do that?

Earth's escape velocity is 11 kilometre per second. But the escape velocity of an asteroid? Phobos is about the same size as an extinction class asteroid. Its escape velocity is about ten metres a second. This link says that is 26 miles per hour. Asteroid 2002 NT7, which caused a scare six weeks ago, will approach Earth in 2019 is 2 kilometers in diameter. If its density was the same as Phobos, and I have done my math right, its escape velocity would be just 2 meters per second.

IANAP, but it seems to me that nuclear charges would be the best approach. IANAP, but I wonder whether an arrangement of nuclear charges arranged across one hemisphere, and exploded more of less simultaneously, would be a better approach.

We discussed shaped charge anti-tank warheads on slashdot a couple of weeks ago. In the shaped charge warhead the shape of the explosive charge is calculated so it focuses around the non-explosive slug it is meant to accelerate.

I've wondered whether the explosive charges would have to be in contact with the surface of the asteroid to be effective. If that wouldn't be necessary then there could be a considerable saving in rocket fuel, because you wouldn't need to match velocities upon arrival. Our existing ICBMs have their MIRV buses. We would need to lift the MIRV buses to LEO, and assemble boosters, in order to send them to intercept the asteroid. So we wouldn't have to develop new technology, like Orion rockets, ion rockets, mass drivers solar sails, or giant air cushion.

Unfortunately I think it would be necessary for the charge to be in contact with the asteroid.

Re:Easily misunderstood

[geoswan]

Back when "Armageddon" was stinking up theaters nation-wide ...

And what a stinker it was too. One of the groaners that bugged me about it was -- the un-named rock is spinning, right? So, suppose you know -- somehow -- that you could split it into two hemispheres? You are going to have to time the explosion just right, so the two hemispheres blow off normal to the Earth-striking trajectory.

Light the fuse at the wrong moment and all you manage to do was arrange for Earth to be struck twice, at two places, a second or two apart.

Re:Kids, try this at home!

[aardvarkjoe]

Mr. idiotnot:

Thank you for your contribution. Now please prepare a report on why, exactly, incoming asteroids would be hot enough to glow. Be prepared to show whether or not that will be relevant at the time that the plastic hits the asteroid.

Thank you,

Your Fifth-Grade science teacher.

Nukes.

[El]

Nukes would tend to uncontrolably break the object up into smaller pieces; chances are some of these pieces would still strike Earth, even if the original object was going to miss. Granted, I'd rather be hit by a few 100 meter rocks than 1 big 1000 meter rock, but it's still not a satisfactory solution. Now, if you could split the object in a controllable fashion, like a diamond cutter splitting a diamond, it would be useful. Problem is, we know very little about the internal makeup of asteroids, never having been inside one.

Moon

[suss]

...but will the Moon get a passenger airbag?

Re:Kids, try this at home!

[El]

Asteroid's are NOT hot. They're out in space, they tend to be a few degrees above absolute zero (ok, so there is some solar heating of the surface). By the time that sucker heats due to friction in the atmosphere, it's WAY to late to deflect it!

speed issue?

[wirelessbuzzers]

Most asteroids approach at speeds of several kilometers per second. To catch them without popping, the airbag would have to fly out into space, turn around, match speeds with the asteroid, deploy (possibly not in that order) and then fire its rockets the other way to deflect it.

Wouldn't it be easier just to land on it? Or nuke it?

Also on CNN

[unsinged int]

Link from my rejected story. Grr.

Still need a detection meathod

[jonman_d]

All this talk about HOW to deflect an asteriod is wonderful, but I think many people forget that we actually have to SEE the damned thing first. Last I checked we were only monitoring a very, very, very tiny amount of the sky, and NASA's budget is still being attacked by the politicians.

You can't defend against something that you don't know is there. And I'm also willing to bet that thing thing would take some time to be deployed, so we'd probably need to see the asteriod pretty early.

Defence plans are great, but what we really need is to be watching more of the sky.

Re:Still need a detection meathod

[thogard]

How long was it between inital spoting of NY40 and the time it could be seen by a low cost telscope? If it was going to hit, there would have been nothing we could do and some of us wouldn't have a net connection right now. I've personaly been point out to bible thumpers that NY40 might have been a warning from god to prepair and like noah, we can preapir.

Defense first, then offense--

[vandelais]

Goodbye Saddam!
(just kidding, he's my neighbor)

(Air)bag?

[Devil's BSD]

Assuming it's made of air and mylar, it would burst. There is about zero pressure in space. That's why astronauts have to have spacesuits, and those spacesuits are thick and expensive as h3ll. Knowing how relatively weak mylar is, the "air"bag would burst before entered space, due to the immense pressure difference.

Really, is this important?

[JeanBaptiste]

Movies aside, killer asteroids rank WAY down there on my list of worries. Lets see, what has a better chance of killing me:
1. Basement Stairs
2. Lightning
3. Bees
4. Falling coconuts (look it up, it really happens)
5. Brain embolism
6. CowboyNeal

Re:Really, is this important?

[WIAKywbfatw]

The funny thing is, if you ran this as a /. poll at least 5% of voters would choose the CowboyNeal option.

On that basis alone, you could argue that CowboyNeal should be permanently incarcerated, as he's demonstrably a menace to society.

Angle?

[Tablizer]

I can only envision this working if the rock is coming it at an angle. If it is more or less strait on, then deflection would have to be almost 90 degrees. Not very likely.

Unless, the idea is to push it toward the oceans. But larger asteroids will make a mess for all regardless of where it hits.

Re:Angle?

[Gorobei]

Unless, the idea is to push it toward the oceans.

Have you ever throw a rock in a pond? The last place you want an asteroid to hit is in an ocean! Think big waves hitting the shores (which is where most people in the world live.) For a non-trivial, non-planet-killer, you want it to hit in the middle of a big landmass (e.g. middle of the USA, middle of Asia, middle of Australia, etc.) Almost zero population in all those places, still a lot of loss of life, but way less than slapping it down in the middle of the Atlantic or Pacific!

Answers previously posted story

[mc6809e]

Science: Most Beautiful Experiment in Physics

Answer: Airbags for Planetary Defence

A Comedy of Engineering

[Mulletproof]

Let's ignore the physics of a 100,000 ton rock hitting a mylar balloon for the moment. I'm more interested in how they're going to get this gas into space. I realize it can be compressed, but 3 cubic kilometers worth? Has anybody done the math here?! The only way I can see this doing a bit of good (and not really even that) is that the asteroid might be nudged off course when the bag ruptures with all it's atmosphere in a shockwave sorta thing. But then, you might as well send 50 nukes up after it... Hell, the engineering there would probably be a lot simpler... I guess, the balloon would have a certain amount elastisity to it before it bursts, giving it some impact resistance as the mylar absorbs the shock, but I have to wonder... Why even bother?

Re:A Comedy of Engineering

[ColaMan]

All you need is enough gas to apply enough force to the inside of the bag to keep it inflated against the near vacuum of space (oh, and against your rock when you finally hit it).

eg: a 0.1 psi pressure difference would be more than enough, considering the amount of square inches on the surface of a cubic mile bag. A cubic meter of liquified gas expands to many,many,many cubic meters of gas when you're talking an 0.1psi pressure differential between your container and the Outside.

Notice my excellent mixture of SI and Imperial units? That's apparently very important and nearly a mandantory requirement in space R&D ;-)

Re:A Comedy of Engineering

[zenyu]

I'm more interested in how they're going to get this gas into space. I realize it can be compressed, but 3 cubic kilometers worth?

There is very little air pressure in space, so you don't need a lot of pressure for the ballon to inflate. You do need to keep enough pressure in it so your rocket doesn't push through the ballon and hit the asteroid. Getting a big rocket to the asteroid is beyond what we could do by next year say. (By "we" I mean Russia since they still have some big rockets, but not that big, it would have to be an international thing with the US sending up supplies, Russia supplying the big fuel tanks and engines, and Europe and Japan footing the bill.)

One advantage of crashing into this thing with a big airbag before doing a 20-30 second big burn is that the momentum of the rocket would be fully transfered to the comet as more of a translation than a rotation. Plus landing on the comet in a place were it would just translate and not rotate would be difficult.

It doesn't really rule out the nuclear option either. Since you only get to do that once you'd try this first, then check if you moved it enough. If not an H-Bomb isn't so heavy, you'd have brought one along. Now you just land on the comet and set it off. Hopefully enough of it is vaporized quickly enough to push the remaining fragments off the they collision path to Earth.

Not that it will matter, we're not looking out the front windshield. Hopefully the first one to hit us in modern times won't be the big one. But I bet if Sydney disappeared one day, we'd arrest all the usual suspects and suspend free-speech immediately. Oh, and maybe do something after the an election cycle, or two.

Nukes for asteroid deflection

[XNormal]

I once did some back-of-the-envelope calculations about deflecting asteroids with a physicist friend of mine.

Our presumed target was a 1 mile dinosaur killer that is about to hit Earth in a few months and we want to impart enough kinetic energy to change its trajectory so that by the time it reaches Earth it will miss it by a few thousand miles of safety margin.

Well, it turns out that it takes so much energy that even the biggest thermonuclear devices barely have enough energy to do it, even assuming we could convert it efficiently to kinetic energy.

A nuke going off in space is just a big flash. No real blast. You need some working mass to convert it to kinetic energy. Using the mass of the asteroid itself is dangerous because you don't want it to break into multiple fragments.

Here our calculations probably become much less accurate because we took some shortcuts and made some assumptions that may be way off, but the result we got is that we needed to send some tens of thousands of tonnes of working mass (e.g. water) along with the nuke to convert its energy to momentum with reasonable efficiency.

Needless to say, this is beyond our current launching capabilities.

Re:Nukes for asteroid deflection

[io333]

Here our calculations probably become much less accurate because we took some shortcuts and made some assumptions that may be way off, but the result we got is that we needed to send some tens of thousands of tonnes of working mass (e.g. water) along with the nuke to convert its energy to momentum with reasonable efficiency.

Needless to say, this is beyond our current launching capabilities.

With the Orion it is not. I have a feeling that if there were a dinasaur killer on the way, an atomic powered launch vehicle would be be more politically correct.

Re:Nukes for asteroid deflection

[Odin's Raven]

A nuke going off in space is just a big flash. No real blast. You need some working mass to convert it to kinetic energy. Using the mass of the asteroid itself is dangerous because you don't want it to break into multiple fragments.

Stuff and nonsense. Obviously, you haven't been keeping up with asteriod demolition research.

I did some back-of-the-Blockbusters-receipt calculations, and came to the conclusion that one can safely split an asteroid the size of Texas into two equal halves using a nuke, with each half passing harmlessly on either side of the Earth. (Admittedly, you have to detonate the nuke at least four hours before impact for this to work.)

The key, of course, is that you have to drill a hole into the asteroid and put the nuke inside. This will amplify the force of the explosion sufficiently to split it in half. Mind you, the hole will have to be at least 800 feet deep to make effective use of the explosive force.

Generally speaking, NASA is not the best training grounds for deep hole-drilling technique. (Yes, there was that minor problem with the "meters vs feet" whoopsy, but that's not formal training.) Do your recruiting in the oil industry, since they've had a lot of experience with drilling. I think it's well-established that anyone can become an astronaut with about a week's worth of training, whereas there's just no way you can figure out how to drill a hole without a lifetime's worth of study.

Hint:Harry S. Stamper is widely acknowledged as the world's foremost core driller. I'd start with him.

Re:Nukes for asteroid deflection

[bwindle2]

And what is wrong with breaking it up? Say you hit the asteroid with the biggest nuke we've got, wouldn't it either a) break it up into smaller pieces that would then hit the atmosphere and burn up, or b) shatter like a clay-pigon and the pieces would miss the Earth?

Re:Nukes for asteroid deflection

[XNormal]

The superheated rock/iron vapour flying off is the reaction mass that supplies most of the deflection.

It will also send fantastic shockwaves into the asteroid and break it into pieces, some of which will hit Earth. That's why I said that using the mass of the asteroid itself as reaction mass is dangerous.

Air Bags

[evilviper]

Air Bags for Planetary Defense

Yes, I've always thought congress should do something about the risk of asteroids.

Oh, wait...

liability?

[dirvish]

What happens when the US messes up the asteroid bouncing project and they send the asteroid directly into France?

Mylar?

[3Suns]

Why use mylar airbags when we've got plenty of used-up old conservatives lying around? Lets' throw Rush Limbaugh out there to protect us from asteroids...

done and done

[prockcore]

Good thing Earth already has a built in air bag, it's called "the atmosphere".

Re:Anyone for asteroid insurance?

[dragons_flight]

The idea for doing a calculation like this is

(Expected Probability of Dying from Impactor of mass M) = (Frequency of impactor of mass M)*(Percent of People expected to Die in Impact)*(Average Human Lifetime)

For major extinction events (like that which killed the dinosaurs), reasonable numbers are: 1/300,000,000yrs*100%*70yrs = 1/4,300,000.

So in some sense you have a 1 in 4.3 million chance of dying the way the dinosaurs did.

Of course that event was rare, but suppose you are a pessimist and think 60 million people (1%) will die from a rock of a size that hits Earth every 50,000 yrs, then this gives a 1 in 70,000 chance of dying in this sort of event.

The idea is to do a sum over the entire range of impactor sizes with some presumed frequency of impact and percentage of people killed, but because these quantities are highly uncertain, you can essentially claim values that will lead to virtually any result you want.

In any case, you should realize that the probability of dying by impact is mostly determined by the rate of major impacts, which given 2000 years of recorded history, are probably rare enough that one isn't going to jump on us even if it takes a century to figure what we would do about a asteroid on a collision course.

Side pocket

[Citizen of Earth]

suggests deploying an inflatable mylar bag a few kilometers in size, and using it to push the projectile aside

No, what we should do is build a giant pool-cue stick and knock another asteroid into the first asteroid, deflecting it into the side pocket.

Re:Kids, try this at home!

[Billly Gates]

The moon is 200 degreesF in the sun and -200F in the shade. If the incoming asteroid is facing the sun then it can get up to 200F assuming its not spinning at a fast rate. I do not know how strong mylex is at that maximum temperature but I assume the scientist took this into consideration. I think the previous poster was refering to the tails he see's in commets as they head towards the sun. Of course anything thats water based above 32F is going to create a trail. Its not glowing hot into it gets close to the sun.

I think the most important issue is how to stop the rock flying towards earth at such an incredible speed. This will not work as a standard catchers mit because it would blow right through it like it wasn't there. However if the asteriod is detected early enough I suppose you could use the ballon utilizing the moon's and earth's gravitation force to closely match the speed of the asteriod and then catch it and slow it down gradually with the rockets or steer its direction. To me that would take a looong time since asteroids can travel up to 28,000 miles per hour and the fastest rockets today can only go up to 7,000 miles per hour. You would have to do many, many revolutions around the Earth and Moon to even get close to the matching speed and then use the rockets to move ahead of the asteroid and then slow it down enough to catch it. It would take years to construct and test this idea. I wonder if it would be cheaper and easier to just send nuclear rockets to detonate at the asteriods surface to steer its course. I am aware it would not destroy the asteroid but steering it may be the only solution with todays technology.

Heat, inflation, etc

[forkboy]

Not for nothin' but wouldn't the heat of the asteroid (from passing through atmospheric re-entry) smoke a hole in this airbag before it had a chance to absorb much force from it?

And what would they plan on inflating it with? Part of the protection of an airbag is the force of it inflating as your momentum carries you forward. It's an azide compound that generates a bunch of nitrogen gas that rapidly inflates it. It would be a hell of a chemical reaction to generate enough gas to fill a several km wide cushion. Maybe I should think of it more as one of those airbags the fire dept. uses to keep jumpers from smacking pavement?

Tests.

[DarkHelmet]

Tests on Crash Dummies show that Airbags save lives.

Therefore, an Airbag for the planet earth will save the lives of 6 billion dummies :)

I can move the earth with a big lever

[thogard]

1) F=ma
2) ????
3) Profit!

whats the airbag going to push aginst?

More great science from Okie State!
Its sad but I spent some time there till i figured out I could leave....

Re:What about...

[Chris Burke]

Reflection does matter. Conservation of Momentum and all.

Re:asteroid approaching - gimme funding proposal #

[foniksonik]

funny, cause I just watched Apollo 13 again and they repeated repeatedly the fact that the reentry vehicle had to approach the earth on a very specific vector or else they would burn up or bounce off the atmosphere... most likely meteors have the same approach and entry window as man-made detritus.

In the end of course it only takes one large asteroid to do it right and kill us all...

carpe diem I guess...
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What we really need...

[Arcturax]

Is a huge board with a nail in it!

We just have to be careful that we don't build a board with a nail that is so big, we destroy ourselves!

Slight adjustment

[Arcturax]

Insert "Pusher robot" above "Basement Stairs".

Or should that be the "Shover robot?"

Re:Energy shields!

[Arcturax]

If we could make an energy shield today, the military would have them now most likely. Hey, maybe they do but only in those secret bases like you find in Fallout.

But seriously, they ARE working on them. They just haven't figured it out yet as far was we, the public, know.

Dueling Airbags

[lildogie]

As any Batman reader knows, a mad scientist bent on planetary vengeance could use the same pillow/sail technology to push an asteroid _into_ earth's path.

The proverbial sword cuts both ways.

deployment mechanism?

[digidave]

And exactly how do they intend on getting a giant steering wheel into space?

Bungie cords, of course.

[Mulletproof]

As long as we're talking improbable ideas, I suggest we fire an orion booster equipped with a several mile long bungie cord. No, no... i know what your thinking-- Another hair-brained ballon scheme, but wait! Our chief problem is landing the booster safely on the 'roid. Fixed rockets will kill as much intercept velocity as possible and upon the astroids flyby of the booster will fire* several kilometer long bungie cords that will anchor* themselves onto the astroids surface. The lines will hopefully soak up enough of the velocity as to impart some of it to the booster, being jettisoned before the full snap back occurs (or the line(s) simply break). The booster should then be able to edge up to the 'roid, place itself and blow it off course.

*Engineering uncertain, use your imagination, sport

Hell, if he can get funding for balloons, I should get funding for this! ;)

Hmm, a little late if you ask me....

[wdavies]

Given I submitted this three days ago:

2002-08-28 19:40:21 Asteroids and The Giant Airbag (articles,news) (rejected)

However, here's the link to the New Scienctist Article that got the scoop.

Re:Kids, try this at home!

[aardvarkjoe]

I'm fairly certain that the original poster was referring to the fact that meteors are glowing hot when they hit the earth -- and I was trying to point out that the reason for that is air friction, which isn't relevant, since if the asteroid is inside the earth's atmosphere, it's already Too Late. I just thought it rather silly that he was playing armchair scientist, and missed something that basic.

Of course, you are correct about the temperature extremes that it will be subjected to; I'm sure that a standard mylar balloon wouldn't hold up for it. However, I'm sure that they can come up something that would work.

You Could Just Speed the Asteroid Up

[Uggy]

It's not like the earth is just sitting there waiting for something to hit it. If you detect a collision course, both speeding up the asteroid or slowing it down might mean the difference of several hundred thousand miles. Remember the earth is moving in orbit around the sun, so speeding up the asteroid by just a tad might make all the difference.

Like others have mentioned, what is really needed is to have a earlier forcast of where the things are headed. What's Deep Blue doing these days? Couldn't it see God's chess moves several thousand iterations into the future?

Inflatable Technology

[Robotech_Master]

Was I the only one who thought of Sluggy Freelance's Dr. Schlock and his futuristic "inflatable technology"?

Maybe there's something to that, after all...

1 chance in 10,000

[geoswan]

Life on earth can cope with two .25km wide asteroids much better than one .5km wide one. As the parts get smaller, it becomes a trivial problem. The earth gets hit every single day.

A number of respondents have said more or less the same thing -- that Earth is struck by small space rubble every day, with no apparent adverse effects. I have trouble with this idea.

But first, to be pedantic. If you split a .5 km berg into .25 km pieces, you get eight pieces, not two pieces. Volume increases as the cube of the radius -- you know, height, width, depth...

Here is a link I found in an earlier slashdot discussion to an article classifying the destruction from different sizes of impacting rocks. This passage discusses the difference in destructive effect of a rock large enough to pierce through the atmosphere, and strike the surface, and those smaller or less solid bergs that fragment in an airburst.

The total area of destruction is not, however, necessarily greater than in the case of atmospheric disruption of somewhat smaller objects, because much of the energy of the impactor is absorbed by the ground during crater formation. Thus the effects of small crater-forming events are still chiefly local.

This suggests to me that 8 x 100 megaton airbursts would be worse than one 8,000 megaton groundburst.

The article says a 10 meter rock releases a blast equivalent of 100 kiloton of TNT -- about 6 or 7 x Hiroshima. The 1908 Tunguska event, the airburst of a berg about 50 meters in diameter, released the blast effect of a 16 million tons of TNT. The fireball to seen to streak across Pennsylvania this summer was less than a meter in diameter.

A 500 meter rock, massing something like 4*10^7 tons, would not wipe the Earth of life. Nor would being struck by by 40*10^7 tons of rubble. I contend it would be a mistake to shrug off either one as trivial however.

Here is a final quote:

...Indeed, during our lifetime, there is a small but non-zero chance (very roughly 1 in 10,000) that the Earth will be struck by an object large enough to destroy food crops on a global scale and possibly end civilization as we know it (Shoemaker and others 1990).

Re:1 chance in 10,000

[geoswan]

Here is another quote suggesting that the effect of airbursts are not trivial. The dust generated is more disruptive than the impact itself, if there was an impact. So, breaking the rock into pieces small enough they don't penetrate all the way to the surface may be worse than doing nothing...

What is the range of impactor sizes that might lead to ... global catastrophe? ... the most frequently discussed estimate of the threshold impactor diameter for globally catstrphic effects was about 2 km. ... Of the various enviromental effects of a large impact, Toon [Brian Toon of NASA Ames] believes that the greatest harm would be done by the sub-micrometer dust launced into the stratosphere. The very fine dust has a long residence time, and global climate modeling studies by Covey and others (1990) imply significant drops in global temperature that would threaten agriculture worldwide.