GoatGuy • 11 hours ago −

I'm not sure what to believe at this point. Clearly the cabal of enthusiasts on wikipedia have sensationalized the editing of the article ("it was from 15 meters to a few meters in diameter" - since when do we use larger numbers first, except to sensationalize data, assuming the glee-lambs that read shit don't see but the first number?)

Its overpressure wave arrived 127 seconds after air-burst ... more or less. The angle in the sky was about 60 degrees from the horizon in Chelyabinsk, where being the largest center, most of the damage was reported. The cylindrical compression wave travels more or less at the speed of sound, or about 340 meters per second, averaged out at 300 m/s for the rarefied atmosphere. Therefore, absolute distance was 127 × 300 = 38 km. At the 60 degree above-horizon the range was 20 km, and the height was 20√3 = 34 km.

Now, taking the nice online document

http://books.google.com/books?... into account, and applying formulas therein (and no, I'm not going to do all the calcs here... they're complicated!) ... it looks like the structural damage was substantially less than a 1 lb/sq inch (7 kPa) ... a few windows stove in, quite a few broken glass panes, but not universal ... and certainly not much "structural" damage.

Working backward from the equations and tables, where 1 megaton at 2 km height has a 1 lb pressure ring at 22 km (but would have a 1 psi ring at 30 km if burst at 30 km)... it looks like the "yield" was on the order of the quoted 300 kT.

It really all depends on that 127 seconds. I could find no continuous videos that recorded both the streak and the sound of the air-blast. If anyone has access to one, we can get closer.

One powerful meteor though! Its sobering to think that there are 100's of thousands of these objects criss-crossing the Earth's orbit every year, in the range of 1 m³ to 20 m³, and that every year or two on the average, one of them commits to a "direct hit" somewhere on the planet. The spy satellites have been watching them for decades.

At 30 km/s each ton of impactor carries 0.1 kT of kinetic energy. So... if this thing actually did deliver ~300 kT, then it needed an initial mass of ~3,000 T (3 Gg). One can assume that a substantial amount of its kinetic energy went into making the oblique-entry-angle shock wave in the atmosphere. If it had been a more vertical strike, it would have been quite a different situation.

GoatGuy

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danielravennest GoatGuy • 3 hours ago

Infrasound atomic test monitoring stations confirm the 17 meter, 10kT mass, 300 kT energy estimate:

http://www.nasa.gov/mission_pa...

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MTCZ GoatGuy • 11 hours ago

http://youtu.be/gQ6Pa5Pv_io
http://youtu.be/efvP-RRuJuA this one's location is reportedly less than 10km from epicenter

From here

http://forum.nasaspaceflight.c...

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GoatGuy MTCZ • 8 hours ago

Excellent videos - both capture the elapsed time.

The first one "Armeggedon" in Russian - 131 seconds. The second, 140 seconds. The angles (from shadows) again show 60° and 50° respectively, so it is all consistent with absolute height of 33,000 meters, and an explosive energy of roughly 150 kT to 250 kT.

[To readers unsure of what this kind of precision means, in much of science we're pretty happy to get estimates "more or less in the same order of magnitude", or same power of 10. IN this case, 150 kT = 5.18 (log 10 scale) tons of TNT. The earlier estimate of 300 kT would be 5.48 (log 10 scale). As you can see - both are in scale "5", and only modestly far from each other. 6% difference in the "log" domain of power. Nice accuracy.]