ICER

I've been hanging out at Wikipedia lately. and caught up in a discussion about how to prevent a asteroid for impacting earth. And thought it would be a interesting discussion in this forum. Most of their ideas are pretty creative. But hardly feasible.

What ideas do you have?


http://en.wikipedia.org/wiki/Asteroi...ion_strategies

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Prevent it? I don't think so. About all you can do is go outside and grin, as you watch it come closer and closer and closer and____________________

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Slavakion

Build a wormhole and teleport that sucker into the sun. (Hey, it could happen... maybe)

If we had plenty of advance notice (and the requisite technology), we could launch tactical missiles at it to divert it away from us.

The_Jazz

The tactical missle would probably work as long as the object was an asteroid and you didn't break it apart when you detonated the warhead. The real problem comes if the object is a comet. From what I understand, the consensus on a potential comet strike is "bend over and kiss your ass goodbye" since a thermonuclear explosion would most likely either shatter it or just be absorbed by the ice/snow/fluff. If we had say 5 years warning, I think that we have the technology to at least try the detonation theory since we could haul a warhead up pretty easily on either an Atlas or a Russian lifting body and then mate it with a solid fuel booster of some sort to sling it out. It would be incredibly dangerous since we're talking about moving a pretty significant amount of plutonium (a lot more than the 14 oz that the Pluto mission had on board), and if something went wrong that part of the Earth is uninhabitable for the next 100,000 year. Then again, it might be a moot point with a large enough comet or asteroid strike. But if whatever it is happens to be 5 days away, well, start working on the flexibility in your back so that you'll be able to reach your ass.

Then again, you could just send Bruce Willis and Ben Affleck out on a modified space shuttle with an Aerosmith soundtrack and have them save the world at the last minute. That's what I'd do.

TheOtherDave™

Realistically, I think our fate lies in early detection more than any other factor.
Also, the slow deflection method sounds most practical to me.

The idea of using thermonuclear detonation to destroy an inbound asteroid seems too risky. IMO, you run the risk of fracturing a 5km asteroid into two 2.5km asteroids, without substantially altering the course of either.

Why not fly a spacecraft out to the incoming rock, land on it and use solar sails and / or a series of solid-fuel booster to alter the course of the asteroid?

asaris

Yes, but fracturing an asteroid would increase its surface area, increasing the amount of disintegration as it enters the atmosphere, right?

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The_Jazz

Yes it would, but you would have to somehow make sure that all of the pieces that were going to enter the atmosphere were going to be small enough to either burn up completely or burn down to a small enough size that they would do less damage. You're also running the risk that by shattering them, you're leaving major flaws within the pieces that could cause them to explode in midair, causing as much or even more damage than an actual strike. Remember that thermonuclear weapons being used in an offensive role are set to detonate several miles up to maximize the damage over a wider area.

There are a couple of problems here, but none that are necessarily insurmountable. First, a solar sail would be the preferred method, but you'd probably need to have it completely deployed several years in advance and it would most likely require human flight out to the object to make sure that it is attached correctly since we most likely won't have a very good look at the object, given the time necessary. That's the least likely to cause the object to shatter, but we definitely don't have the technology right now.

As for a solid fuel boster, we still have the same problem with having the requirement of a manned mission to the object, but you also run the risk that the booster will cause the object to shatter or to move in an unforeen way because of balance issues. By definition, you can't turn off solid fuel vehicles, although you could use a series of them to make a number of small corrections. Regardless, it's a difficult and dangerous way to accomplish the task. I still think that if such an object is found tonight and scheduled to hit 5 years from now, the most effective way to either destroy or deflect it is a warhead(s). But I'm not a rocket scientist, nor do I play one on TV.

Toaster126

Wikipedia is so cool.

Also, reading the linked article give us this gem.

"NASA reported that a soccer field-sized asteroid missed earth by about 75,000 miles June 2002. This is approximately 1/3 the distance from Earth to the Moon, a very narrow miss in astronomical terms."

I hadn't heard about that.

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The_Jazz

There's also an asteroid that's due for at the very least a near miss in about 2021 or so. Last I heard they hadn't charted its orbit well enough to be able to tell if it would hit or miss. The good news is that there are at least a few people out there looking for things like this. It's going to happen sooner or later, although those are astronomical terms and could mean another 150,000 years as easily as not.

ICER

What if we don't actually hit the asteroid. just detonate a few megatons nuke near it. wouldn't the force of the blast move it to a different trajectory?

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The_Jazz

If there are no inherent flaws in the rock, then yes, that would work just fine, assuming that you detonated close enough with enough force.

The inherent problem with that idea is that the rock may not be able to withstand the shockwave and could shatter. Remember that these pebbles have been bouncing around for 4 billion years, and the impacts are going to cause cracks and faults. If you set off a warhead too close, you could just end up shattering the whole thing but not pushing it into a new orbit since the force intended to move it ended up being absorbed in the fracture process. That means that instead of 1 large body hitting, you've got hundreds or thousands of small to medium sized bodies. The small ones would probably only cause local damage, but the medium sized ones can pack a big wallop. The Great Crater in AZ was caused by a boxcar-sized rock that impacted and left a hole a mile across and spread large debris 20 miles. If you have 20 of those hitting around the world, the destruction could actually be greater than what would have happened if the single body had impacted. Not that it would matter since human civilization would pretty much be over under either circumstances.

The real problem is that we don't have a good way of gauging what flaws are inherent to any large body. What looks like a solid rock could actually be a collection of gravel held together by their own gravity. From millions of miles away, it's awful hard to tell which it is. The size and distance of the explosion are going to need to be determined by what it is that's on track to impact. The missile option is our best bet, but it's by no means 100% sure of removing the threat.

However, you should probably be more concerned about being outside during a thunderstorm than the earth being hit by an asteroid. The odds are much better for the lightening.

TheOtherDave™

Yes, fracturing a large body into several dozen smaller bodies will greatly increase surface area.
With a high surface area - to - mass ratio, it is likely that a smaller body (say about 10 meters long) will burn up as it descends through the Earth's atmosphere.

BUT it is a calculated risk to blow up a large body at close range..

If the inbound fragments are larger than about 100 meters, you're going to have very serious problems when they strike the earth's surface.
If they hit land, you would probably see replays of the 1908 Tunguska event (LINK).
If they strike off-shore, you could very well see massive tsunamis.

A direct hit from a 2.5km asteroid would be sufficient to wipe us off the map. So if nuclear weapons were employed to break a large asteroid up, IMO they ought to be employed at the earliest opportunity, not the last minute (as seen in Armageddon )

Good point about the downside of the SRB proposal... in retrospect, I should have proposed a more controllable output of thrust. God forbid, the rock could start to spin 'round like a gyroscope and still come straight at us.

The_Jazz

This isn't entire correct. The Tunguska event was technically not a "strike" since there was no crater or impact site. The prevailing theory is that a comet fragment entered the atmosphere but exploded midflight, causing a shockwave that caused extensive damage across large parts of the Russian Empire. The destruction zone was, if memory serves, roughly 200km across. As an aside, the pattern of destruction was used by scientists in the 40's and 50's when they were designing nuclear weapons in order to find the maximum destructive potential of a given yield of a device.

Regardless, anything larger than say 100m across would be very, very bad. Anything over 50m and it's only bad for the people within a few hundred miles. So, if you live in Chicago, Memphis or Kansas City, don't root for an asteriod to take out Saint Louis, no matter how much you hate the Cardinals.

NoSoup

If I remember Correctly, if we were able to detect an object that was on a trajectory to smash into earth a minimum of three years in advance, we could literally just paint it white and the trajectory would be so different that it would miss earth by a substantial gap.

As far as current technology goes, I would imagine our best bet at attempting to change a comet/asteroid's path would have to involve lasers, since we just don't have the technology to intercept the object while it is still suffeciently far from earch. Sending nukes would be another option, but an unpredictable one.

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The_Jazz

I'm not sure where you're getting your information, but this isn't very likely. Photons don't impart any momentum when they strike an object, and solar particles aren't going to be affected by an object's albedo (amount of light that it reflects. If you installed a solar sail, you could change the orbit enough in 3 years assuming a small enough object, but we're back to the installation problem, which is also there for the painting idea. Sorry, this just wouldn't work, unless I've missed a part of the process.


To the best of my knowledge, no one has orbital lasers right now, although that was what was suggested as part of the Reagan "Star Wars" project. It is certainly possible to orbit a large laser, but the mechanics of it would be difficult given that the laser will be orbiting the earth while firing at an object hundreds of thousands of miles away (at least). There's also been no credible test that I know of about the disipation of energy of this kind of distance. I imagine that there would be some loss of focus over such a great distance. However, most, if not all of these could be overcome, given enough time. Three years MIGHT be enough time, but it were my project, I would want at least 5 to get everything tested and orbited. You'd probably want several firings to move the object enough to get it moved enough, so power might be a problem too, depending on what you intend to use.