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Meteorite crash in Russia

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Re: Meteorite crash in Russia

#71
post #53

Earlier quoted context omitted.

I don't know about "taking it out" per se but an air defense system designed to hit ballistic missiles in the terminal phase could also hit an inbound meteorite. It is within the performance envelope of those types of systems. That said, against a meteorite it won't do much good since it is an inert mass. It is plausible that the Russians launched an interceptor just to be safe. If it is a meteor, it neither hurts no…

Russians have scientists working on the meteorite problem, but I doubt the military would do a hail Mary launch on this. If anything, they would much rather let it fall intact than risk having it break up and spread damage to a much larger area. But that still assumes they can respond quickly enough or had missiles on standby with weapons that can affect a meteorite (not specifically ballistic reentry capsules, but a…

It does seem silly to intercept. The computers could ascertain that the trajectory was unlikely to have originated on Earth in milliseconds.

Modern terminal guidance systems are all imaging based. Or at least the US ones have been for a couple decades; I imagine the Russians are using something at least vaguely similar.

Basically, the missiles latch onto the target visually and are capable of recognizing their target from the details of its appearance (in an air defense context, not just "an airplane" but "that specific airplane"). It is why, contra Hollywood, modern terminal guidance systems are nigh impossible to spoof. The missile knows what the airplane looks like and can read the tail number off your craft, so as long as it can locate it (even if it temporarily loses sight), it is likely to hit unless the motor runs out of gas. Heat has little to do with it, though the imagers often work in broad spectrum infrared.

Lots of smaller, impacters with kiloton-class impact energies are never discovered or discovered at the very last minute. This looks like a pretty small rock in terms of damage done so it could easily have been missed by sky surveys.

Re: Meteorite crash in Russia

#72

That is an amazing event. I am not sure I buy the meteorite story. Has anyone checked on 2012-DA14 [1] the asteroid that was supposed to cross between the earth and geosync orbit this evening? One conjecture would be it knocked something out of orbit. The air defense stuff is somewhat hard to believe, we don't intercept de-orbiting space junk, much less less hypersonic meteors. Further every missile interceptor that…

This guy https://twitter.com/BadAstronomer/status/302313851511271426 seems pretty sure it's unrelated to 2012DA14. And he has 230K followers on Twitter, so ... shrug

The general idea being that the Earth moves ~100,000km/hr around the sun, and with the asteroid fly-by many hours away, that would mean a pretty wide orbital gap.

Re: Meteorite crash in Russia

#74
post #45

I don't get why everyone seems to be running out of (what appear to be) fairly sturdy concrete buildings and into the street. Sure, a building won't protect you from an incoming meteorite of any size, but being indoors might protect from fragments if an incoming meteor hits something else.

Frankly even in hindsight I would be running out of buildings, not into them. That was one hell of a sonic boom, and do you really want to take the chance of seismic activity following shortly? I would be more concerned about the building falling onto me than the meteorite.

In uncertain circumstances, I think I would almost always prefer not being under concrete.

Re: Meteorite crash in Russia

#75

I can't get over how long it takes for the sonic boom to hit. This video has the meteorite trail on camera for 27 seconds before you hear the boom: http://www.youtube.com/watch?v=Np_mpGYSBSA How fast does something have to be travelling to build up a delay like that?

While it's moving at great speed, it's really about distance that determines the gap with sonic booms. Speed of sound is ~340m/s at sea level, so using that value with a gap of 27 seconds we can assume the boom originated ~9.1km away from the camera(thus it took 27 seconds for the sound to reach the camera). The distance is probably wrong given the speed of sound is different depending on the altitude. The speed had…

And to be clear, there isn't any one "boom" event with a sonic boom. It is an ongoing event for stationary observers, a pressure front that follows the object and is heard when it passes by you.

Re: Meteorite crash in Russia

#77
post #11

>According to unconfirmed reports, the meteorite was intercepted by an air defense unit Anyone else catch this? Is this just a bad translation and they mean to say that an air defense unit tracked the meteorite on radar? I wouldn't think any air defense system would be capable of actually intercepting a meteorite, but perhaps I'm wrong. Still doesn't seem like anything intercepted it from the videos.

It's not impossible, but incredibly implausible. First off there isn't any evidence of an interception in any of the videos. Second, intercepting a hypersonic object with ordinary SAM sites is pretty much not going to happen. The amount of time it would take just to get a radar lock let alone to launch missiles would not leave much time for interception.

Interestingly, Russia does have an active ABM system. The old ABM-treaty allowed both the US and the USSR to have one ABM site active for each country, the US shut theirs down fairly quickly but the Soviets maintained and later upgraded theirs, protecting Moscow, and Russia has kept it. It's a nuclear warhead based system, it would be interesting to see what the hell would have happened if the same event happened over Moscow instead of Chelyabinsk.

Re: Meteorite crash in Russia

#78

Wow, do you know how lucky we all are? Silly little shit like this could easily start WW3. We need complete ICBM disarmament. They can keep their bombs and we can keep ours (for now), but we should restrict delivery systems such that there is a built in lag (bombers taking many minutes or hours to reach their targets), and can be recalled. ICBM's can be launched in a moment, and it is impossible to recall them or dis…

No sane military would introduce such a lag. Furthermore I think your concerns are overblown. After all, something far more "potentially disastrous" happened in 1983 at a high point in Soviet/US tensions, and fortunately the guy in charge of retaliation launching had the common sense to reason a war wouldn't be started with one (or in his case, 5) missiles. http://lesswrong.com/lw/jq/926_is_petrov_day/

Re: Meteorite crash in Russia

#79
So, uh, NASA was expecting this. They were going to have a livestream chat about this? Er, looks like they got the prediction slightly off.

http://www.nasa.gov/mission_pages/asteroids/news/asteroid201...

*For the person who downvoted me, there is supposed to be a near earth flyby tomorrow of an asteroid called 2012 DA14 which will be livestreamed with commentary by NASA here: http://www.ustream.tv/nasajpl2. A reasonable explanation would be that the event today was a chuck or asteroid as part of that expected fly by. The astroid is expected to be 17,000 miles away from Earth.

Re: Meteorite crash in Russia

#80
post #63

Earlier quoted context omitted.

I don't know about "taking it out" per se but an air defense system designed to hit ballistic missiles in the terminal phase could also hit an inbound meteorite. It is within the performance envelope of those types of systems. That said, against a meteorite it won't do much good since it is an inert mass. It is plausible that the Russians launched an interceptor just to be safe. If it is a meteor, it neither hurts no…

Looking at these videos it doesn't look like there has been a defense missile: http://www.youtube.com/watch?v=1wUqmS35REY . Such missiles would leave a visible trail in the atmosphere, wouldn't they?

If you're referring to the beginning, that actually looks like it was the trail left behind by an aircraft much earlier. I live near an airport, so I see these quite often after jets go by. Usually that type of contrail appears after 2-5 minutes after a jet flies by. Far too late to intercept a meteorite which can reach the surface in minutes-seconds.

If you mean the middle, that's most definitely the aftermath of the meteorite itself. You can see this in the other videos.

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