Slashdot Mirror
Why Meteoroids Explode Before Hitting the Earth (qz.com)
According to a new study from Purdue University, scientists have figured out why meteoroids explode before hitting the Earth. "The research, published in the December issue of the journal Meteoritics & Planetary Science, shows that as meteoroids plunge, the high-pressure air they push against find its way into the objects' pores and cracks, forcing their bodies apart from the inside," reports Quartz. "The result is a kind of detonation that looks like an explosion." From the report: To explain the astrophysics, researchers focused their work on a widely viewed February 2013 meteoroid explosion place over Chelyabinsk, Russia, a city of 1.1 million north of the Kazakhstan border. Researchers ran a computer program that allowed for them to simulate what happened to the meteoroid in the atmosphere. "Our simulations reveal a previously unrecognized process in which the penetration of high-pressure air into the body of the meteoroid greatly enhances the deformation and facilitates the breakup of meteoroids similar to the size of Chelyabinsk," the study states. The researchers added that while the air pressure is effective at breaking apart small meteoroids, larger ones would likely withstand the force as they come to Earth.
>> Why Meteoroids Explode Before Hitting the Earth
I'm not saying it's Missile Command, but it's Missile Command.
https://www.youtube.com/watch?v=nokIGklnBGY
There is more to the study then meets the eye. This will lead to knowing how to build kinetic weapons for kt/mt range drops with out the fuss and muss of fallout.
So, aliens are basically bombarding us with meteoroids armed with the old "pull my finger" gag. The gall of them! Can't we build a space wall to keep these stinking meteoroids out?
"Memo to the engineering team on the dark side of the moon, building the blimps that will be used to conquer the Earth:"
"Avoid pores and cracks in the outer skin of the weapon. These could lead to premature explosion, which would be a major bummer for the Führer,"
"-- Donald Zuckerberg, Reich Minister of Armaments and War Production."
Schroedinger's Brexit: The UK is both in and out of the EU at the same time!
I swear I read "Why Metroids Explode Before Hitting the Earth"
Something about the OP doesn't make sense.
And no, not the fact that there isn't much in the way of "high-pressure air" at the outermost fringes of our atmosphere...
The part which seems a little odd is to suggest that altering the apparent pressure [i.e. by the velocity of entry] can in some way "force" air into the cracks within a meteorite/meteorid to induce some form of break-up.
Isn't it much more likely to be induced by the coefficient of expansion of the material concerned? If you take a meteorite and then flash-heat the outer surface very, very, very quickly - like for example by slamming it into an atmosphere at several thousand kph - then the outer layer will become very, very hot very quickly - and start to expand. The interior, meanwhile, simply won't have had time to warm up and thus will remain space-cold... As the outer layer warms, it expands. This would easily be enough to cause cracks in the material [think of the way that you can split a rock by pouring water into a crack and then waiting for the water to freeze...].
It's been a while since I studied CFD [computational fluid dynamics - which is the science that would show how atmospheric gases would "flow" around an meteorite as it entered the atmosphere - but I think it's fair to say that a "boundary layer" would form that might in fact make it ridiculously difficult for "high pressure air" to be "forced" into tiny cracks in the surface.
So... very interesting theory, but I think we might find that things like the irregular shape and density of the material [which causes non-uniform stress on the material] coupled with very high speed heating, might be significant factors too...
No, it really won't.
We already have a good understanding of how to drop something from orbit and have it hit the ground intact. At most, this study just confirms that cracked rocks aren't the best choice for that task, which we already knew.
Campfire rocks explode because of water that has made its way inside the rock, not because of forced gas penetration. Couple the forced gas penetration with the friction heating and you get something much more powerful.
Do asteroids or comets have "tails' outside of the atmosphere in the vacuum of space -- ie, plumes of particulates given off? Are they "burning"?
Or is this just what happens when they cross into an atmosphere and experience friction?
I guess maybe I could see solar heating causing them to erode, but at the same time is there enough solar heating much outside Earth's orbital distance?
How soon until small meteorites become target practice for new weapon systems I wonder.
Not soon at all; in fact, never. A meteorite is a meteor that has hit the earth, rendering it unsuitable for target practice.
duh.
A meteor arriving with several times the Earth's escape velocity is not interacting with the atmosphere that you know; it it interacting with the plasma that is formed by compression in front of it. The streaks left by the sub-milimeter particles of a Leonid meteor shower are plasmas with a measured temperature of 4,000+ deg C; the plasma at the head of the meteor would be much hotter than that.
So it is not cold air that is forced into the crevices of a meteor; it is very hot plasma. The pressure this exerts on the internal structure of the meteor is not countered by similar pressures on the back and sides of the object. Most meteors and bollides will burst apart.
Except that if you'd read the article you'd know that internal fracturing caused by steam is not the phenomenon they are talking about at all here. Even very dry meteors can explode for the reasons they describe.
I'm sure people intuitively understood for many years this idea that high speed, high pressure air can cause objects to break up catastrophically when it enters a hole in the object's surface (that's what destroyed the Columbia after all), but I think a lot of the emphasis was placed on temperature (just like your exploding rocks int the fire). Only now they've determined that just the air pressure effect itself can be powerful enough to cause a large ball of rock to explode. I'm sure hot plasma just adds to the effect.
when I read the headline I thought, because of friction from the atmosphere.
And are willing to die to destroy us.
Damping absorbs vibrations. Dampening is caused by moisture.
Are you always a cunt or is it just when you have anonymity?
The un-self-aware irony in this is priceless.
Second class citizen of the New Gilded Age
You should get in an argument with other posters here who declare that this conclusion is obviously impossible.
The arrogance of the lazy boy 'scientist'.
Second class citizen of the New Gilded Age