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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
Have you ever used a pressure washer? I own a mid grade entry level one with 3500 psi. You have to be very careful not to spray too hard into a crack or it will rip whatever it is apart. 3500 might not sound like a lot, but square area is deceptive. Say 300 psi gets into the crack, but the crack is 6 inches deep and 12 inches wide that's 21,600 lbs pushing on each side. But it gets worse, the stress has to flow from one side to the other of the crack, around the propagating crack tip. The sides of the crack act as a lever to concentrate the force many times higher if the crack tip is sharp and enough force is used to slightly bend the material. It's similar to fracking, the pressure may be moderate to high but the surface area is very large and it creates a super large force through several different effects that is capable of breaking rock.
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.
Interesting how you imagine tossing around some dimly remembered terms like "boundary layer" invalidates the detailed physics of these researcher's model.
If they had access to your brilliance they would have know the answer without even examining the problem!
This should a Slashdot "law":
"If, with just a few minutes of thought about a scientific topic you have only slight familiarity with, you believe you have identified a fatal error that a team of highly trained professional researchers have failed to detect, you can be certain that you are wrong."
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