INCOMING!: метеорита в Челябинске, Russian Meteor - February 2013 Options

[volcanopele]

Looks like a small meteoroid decided to spoil 2012 DA14's big day by exploding over Russia...

http://zyalt.livejournal.com/722930.html?nojs=1

[Explorer1]

Depends on one's definition of 'small'! Phil Plait has an early summary/videos: http://www.youtube.com/watch?feature=playe...p;v=rflTN4XAt34
The biggest over a populated area in a long time...

[Fran Ontanaya]

Some info:

http://rt.com/news/meteorite-crash-urals-chelyabinsk-283/

http://rt.com/news/russia-meteor-meteorite...helyabinsk-291/

[nprev]

Clearly a major event. I hope that the reported injuries are mild, and that there are no fatalites.

Caution all to be objective (as all have been thus far) and most of all respectful since there does seem to be a possibility of direct effects on people here, okay?

All that being said: There is no amount of 'wow' I can adequately express. Looking forward to the final analysis of this.

[Explorer1]

Direct hit on factory? http://www.youtube.com/watch?v=DgZ0aA7RUhE

Crews clearing rubble like just another day at work. i know that statistically Russia is the most likely country to get hit since it's got the greatest surface area, but literally a half day before this other rock is a real coincidence.

[machi]

Chelyabinsk's bolid from Meteosat.

[nprev]

Russia is the most likely country to get hit since it's got the greatest surface area, but literally a half day before this other rock is a real coincidence.

And that's in fact what it is precisely. Preliminary reports indicate that the object entered from a completely different azimuth than what would be possible for something associated with that asteroid during the upcoming encounter.

[belleraphon1]

WOW!...

Hope injuries not serious.

Analysis of this should be fascinating.... a mini-Tunguska.


Craig

[dvandorn]

The best of the videos I've seen show the contrail ending well above the ground, suggesting that the impactor disintegrated in the air. I'm wondering whether the bolide actually hit the ground, or whether the damage was caused by an over-pressure wave pushed ahead of it.

-the other Doug

[dilo]

An hour ago, Italian television told about russain military attempt to intercept/destroy the meteorite in flight, through a non-armed missile... I am very skeptical, did someone heared such a story? They showed also an impressive video with a ground explotion near an highway (metoerite fragment hitting ground?)

[machi]

Dilo, today's SAMs cannot hit and destroy such asteroid. Radar has limited range and limited reaction time and even ABM missiles cannot cope with object with speed more than ~7 km/s. It's total nonsense.

[dilo]

Yes, machi, I know and I said I was skeptical! in fact, it seems such rumor was officially denied...

[TheAnt]

The best of the videos I've seen show the contrail ending well above the ground, suggesting that the impactor disintegrated in the air. I'm wondering whether the bolide actually hit the ground, or whether the damage was caused by an over-pressure wave pushed ahead of it.

-the other Doug

Several pieces did hit the ground, images of that factory shown above is only one that might have been a smaller piece.
A somewhat larger impacted near a highway.
And one piece thought to have been larger is said to have ended up in a lake quite far from the city according to my teletext news here.

@dilo: Hard to say, my teletext feed states that there initially were one alert for one possible nuclear strike, but it reads as that alert came after the actual impact so I guess the Italians have elaborated on that fact a bit.

@nprev: The teletext say about 900 wounded, mostly from shattered glass, and a number (no numbers given) hospitalized. But still no mention of any casualties so lets hope there were none.

[Phil Stooke]

The story about intercepting the meteorite is almost certainly a journalist's confusion between the current event and stories about future asteroid deflection missions, which are being discussed in Russia.

Phil

[Mongo]

I am trying to get an estimate of the size of the meteoroid and explosion. Assuming a dense rocky composition with a density around 3 tonnes per cubic metre, I keep getting sizes much larger than the estimate of around 10 tonnes that I have heard. The calculation below results in a mass of around 73,000 tonnes.

The overpressure from the blast wave was sufficient to shatter thousands of windows (and in fact some videos I have watched appear to show that every window in view was smashed) and caused the partial collapse of a zinc factory. This implies that the overpressure was between 1 kPA (shatters many windows) and 5 kPa (partial collapse of some buildings), let's assume that the zinc factory was poorly maintained and the overpressure was 3 kPa.

Early reports give an entry velocity of around 30 km/s.

According to this site, the diameter of a rocky object that produces a 3.1 kPa overpressure at a distance of 30 km from directly under the main explosion (as appears to be roughly the distance from the videos) would be about 36m, producing a 5.26 MT airburst at an altitude of 18.2 km.

Earth Impact Effects Program
Robert Marcus, H. Jay Melosh, and Gareth Collins

Please note: the results below are estimates based on current (limited) understanding of the impact process and come with large uncertainties; they should be used with caution, particularly in the case of peculiar input parameters. All values are given to three significant figures but this does not reflect the precision of the estimate. For more information about the uncertainty associated with our calculations and a full discussion of this program, please refer to this article

Your Inputs:
Distance from Impact: 30.00 km ( = 18.60 miles )
Projectile diameter: 36.00 meters ( = 118.00 feet )
Projectile Density: 3000 kg/m3
Impact Velocity: 30.00 km per second ( = 18.60 miles per second )

Energy:
Energy before atmospheric entry: 3.30 x 10^16 Joules = 7.88 MegaTons TNT
The average interval between impacts of this size somewhere on Earth is 539.1 years

Major Global Changes:
The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the tilt of Earth's axis (< 5 hundreths of a degree).
The impact does not shift the Earth's orbit noticeably.

Atmospheric Entry:
The projectile begins to breakup at an altitude of 63100 meters = 207000 ft
The projectile bursts into a cloud of fragments at an altitude of 18200 meters = 59600 ft
The residual velocity of the projectile fragments after the burst is 17.3 km/s = 10.7 miles/s
The energy of the airburst is 2.20 x 10^16 Joules = 5.26 MegaTons.
No crater is formed, although large fragments may strike the surface.

Air Blast:
The air blast will arrive approximately 1.77 minutes after impact.
Peak Overpressure: 3100 Pa = 0.031 bars = 0.44 psi
Max wind velocity: 7.21 m/s = 16.1 mph
Sound Intensity: 70 dB (Loud as heavy traffic)

edit -- Assuming that the distance from ground zero was 15km instead of 30km, and with an overpressure of 2 kPa, the website gives the following (calculated initial mass 51,000 tonnes):

Your Inputs:
Distance from Impact: 15.00 km ( = 9.32 miles )
Projectile diameter: 32.00 meters ( = 105.00 feet )
Projectile Density: 3000 kg/m3
Impact Velocity: 30.00 km per second ( = 18.60 miles per second )

Energy:
Energy before atmospheric entry: 2.32 x 10^16 Joules = 5.53 MegaTons TNT
The average interval between impacts of this size somewhere on Earth is 410.7 years

Major Global Changes:
The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the tilt of Earth's axis (< 5 hundreths of a degree).
The impact does not shift the Earth's orbit noticeably.

Atmospheric Entry:
The projectile begins to breakup at an altitude of 63100 meters = 207000 ft
The projectile bursts into a cloud of fragments at an altitude of 19900 meters = 65400 ft
The residual velocity of the projectile fragments after the burst is 18.3 km/s = 11.4 miles/s
The energy of the airburst is 1.45 x 10^16 Joules = 3.47 MegaTons.
No crater is formed, although large fragments may strike the surface.

Air Blast:
The air blast will arrive approximately 1.26 minutes after impact.
Peak Overpressure: 2120 Pa = 0.0212 bars = 0.301 psi
Max wind velocity: 4.96 m/s = 11.1 mph
Sound Intensity: 67 dB (Loud as heavy traffic)

another edit -- this is the minimum value that reliably breaks windows, it still results in a calculated airburst energy of 1.9 MT with an initial mass of 31,000 tonnes. I doubt that the airburst was this close to overhead, it appeared closer to the horizon in the videos.

Your Inputs:
Distance from Impact: 10.00 km ( = 6.21 miles )
Projectile diameter: 27.00 meters ( = 88.60 feet )
Projectile Density: 3000 kg/m3
Impact Velocity: 30.00 km per second ( = 18.60 miles per second )

Energy:
Energy before atmospheric entry: 1.39 x 10^16 Joules = 3.32 MegaTons TNT
The average interval between impacts of this size somewhere on Earth is 277.4 years

Major Global Changes:
The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the tilt of Earth's axis (< 5 hundreths of a degree).
The impact does not shift the Earth's orbit noticeably.

Atmospheric Entry:
The projectile begins to breakup at an altitude of 63100 meters = 207000 ft
The projectile bursts into a cloud of fragments at an altitude of 22500 meters = 73700 ft
The residual velocity of the projectile fragments after the burst is 19.6 km/s = 12.2 miles/s
The energy of the airburst is 7.95 x 10^15 Joules = 1.90 MegaTons.
No crater is formed, although large fragments may strike the surface.

Air Blast:
The air blast will arrive approximately 1.24 minutes after impact.
Peak Overpressure: 994 Pa = 0.00994 bars = 0.141 psi
Max wind velocity: 2.33 m/s = 5.22 mph
Sound Intensity: 60 dB (Loud as heavy traffic)

[jasedm]

Wow!!

That's amazing. Inevitable comparisons to Tunguska will be made, but very fortunate this wasn't of that magnitude. Hope all ok

Jase

[ElkGroveDan]

With all those videos there's no doubt an exact and precise trajectory can be computed and I would assume a possible range of orbits extrapolated.

[Gladstoner]

.

[dvandorn]

I can certainly see how there was a pretty big explosion in the air, there is a rather extreme pulse of light and then the contrail sort of vanishes. But -- a 500 megaton explosion only 18 km up, over a populated town, and all we had from that was a bunch of broken glass? I mean, that's more powerful of an explosion than the Tsar Bomba, the largest thermonuclear explosion that has ever been accomplished, and that explosion caused the clouds to move at hundreds of miles an hour away from the blast at distances of 20 to 30 miles. I sure don't see that kind of immense airburst in the videos of the bolide....

-the other Doug


Edit:
oops -- just reviewed the figures, and either I misread the megatonnage the first time through or Mongo adjusted his figures. Still, a 5 MT bomb packs an awfully big punch...

[Gladstoner]

.

[dvandorn]

FYI, NASA TV is running live coverage of the closest approach of DA14 2012 from JPL, with some live feeds from telescopes in Australia, where the asteroid is currently traversing the sky.

-the other Doug

[Mongo]

Apparently, due to Russian laws pertaining to insurance claims, many cars in Russia have dashboard cams (do the Youtube search 'Russia dash cam' ). This means that many more videos of the bolide should be coming out in the days and weeks ahead.

I am waiting for a video that includes both the main flash and the arrival of the shock wave. That would allow us to estimate the distance and height above the ground of the detonation, and hence the minimum energy needed to cause at least 1 kPa of overpressure. I am betting it will be a figure in the low megaton range. A low kiloton-range explosion is already excluded in my opinion. The interval between explosion and shock wave hitting would have been too short, in the 20-30 second range, which I believe is already ruled out from the existing videos.

[dvandorn]

Oh, cool -- the JPL visualizations manager is showing DA14 on Eyes on the Solar System.

-the other Doug

[TheAnt]

Apparently, due to Russian laws pertaining to insurance claims, many cars in Russia have dashboard cams (do the Youtube search 'Russia dash cam' ). This means that many more videos of the bolide should be coming out in the days and weeks ahead.

Yes, this one is a dashcam vid of the event.

[ugordan]

Still, a 5 MT bomb packs an awfully big punch...

Tunguska was in recent years re-estimated to have been around something like that. This clearly had to be less. How much less depends on the actual altitude of the "airburst". At 10 km, a Hiroshima-type burst seems plausible to me. To be in the megaton range, it would have had to be significantly higher up, otherwise I'd expect much more extensive damage below. But these are all just my W.A.G.s...

NASA is estimating this to be around a 15 meter object and they're calling this one the biggest one after Tunguska. Doesn't say what their estimates are based on.

[Mongo]

NASA is estimating this to be around a 15 meter object and they're calling this one the biggest one after Tunguska. Doesn't say what their estimates are based on.

The impact effects website gives the following results for a 15m object with density adjusted to produce a 1 kPa overpressure at a realistic distance given the videos. Total mass would be about 13,000 tonnes for an energy release of 830 KT.

Your Inputs:
Distance from Impact: 15.00 km ( = 9.32 miles )
Projectile diameter: 15.00 meters ( = 49.20 feet )
Projectile Density: 7200 kg/m3
Impact Velocity: 30.00 km per second ( = 18.60 miles per second )

Energy:
Energy before atmospheric entry: 5.73 x 10^15 Joules = 1.37 MegaTons TNT
The average interval between impacts of this size somewhere on Earth is 140.0 years

Major Global Changes:
The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the tilt of Earth's axis (< 5 hundreths of a degree).
The impact does not shift the Earth's orbit noticeably.

Atmospheric Entry:
The projectile begins to breakup at an altitude of 28500 meters = 93400 ft
The projectile bursts into a cloud of fragments at an altitude of 16200 meters = 53100 ft
The residual velocity of the projectile fragments after the burst is 18.8 km/s = 11.7 miles/s
The energy of the airburst is 3.47 x 10^15 Joules = 0.83 MegaTons
Large fragments strike the surface and may create a crater strewn field. A more careful treatment of atmospheric entry is required to accurately estimate the size-frequency distribution of meteoroid fragments and predict the number and size of craters formed.

Air Blast:
The air blast will arrive approximately 1.11 minutes after impact.
Peak Overpressure: 1050 Pa = 0.0105 bars = 0.149 psi
Max wind velocity: 2.47 m/s = 5.52 mph
Sound Intensity: 60 dB (Loud as heavy traffic)

[ugordan]

The interval between explosion and shock wave hitting would have been too short, in the 20-30 second range, which I believe is already ruled out from the existing videos.

This video in particular shows a very long delay between start of filming and shock arrival, but it's obvious from the viewing angle that it's a ways off from the groundtrack so a minimum slant distance (here at least 23 km) is all we can infer. It does also show an unseen building smoking, perhaps it's the collapsed roof of the zinc factory. That amount of damage at that kind of range seems to support a high kiloton range. However, it's dangerous to infer too much from blast effects at these ranges as they start to depend upon meteorological conditions - inversion layers in the atmosphere, etc.

If the burst was at 20-ish km, I personally would place a bet at around 1 MT.

[ugordan]

This just in, via NASASpaceflight.com: a full length video from the flash to the sound. Whopping 2m 21 sec delay! Bolide starts at around 4:30 in the video.

This sucker was big!

[Mongo]

This just in, via NASASpaceflight.com: a full length video from the flash to the sound. Whopping 2m 21 sec delay! Bolide starts at around 4:30 in the video.

This sucker was big!

Holy Cow! Even at that distance, it broke windows! Assuming an overpressure in that video of 0.95 kPA, the overpressure at the distance of the closer videos (with the explosion at about a 45 degree elevation from the horizon) would be about 1.18 kPa, which might be enough to cause the documented damage at the zinc factory, assuming that it was poorly constructed and maintained. So around 1.33 MT at minimum, it could be greater than that.

Actually, if the calculated energy release is correct and the zinc factory was directly under the main part of the explosion, the overpressure would be about 1.37 kPa, making the actual observed damage to the building more plausible, albeit still rather excessive for the calculated overpressure.

Your Inputs:
Distance from Impact: 43.00 km ( = 26.70 miles )
Projectile diameter: 19.00 meters ( = 62.30 feet )
Projectile Density: 6000 kg/m3 (rocky-iron)
Impact Velocity: 30.00 km per second ( = 18.60 miles per second )

Energy:
Energy before atmospheric entry: 9.70 x 10^15 Joules = 2.32 MegaTons TNT
The average interval between impacts of this size somewhere on Earth is 210.0 years

Major Global Changes:
The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the tilt of Earth's axis (< 5 hundreths of a degree).
The impact does not shift the Earth's orbit noticeably.

Atmospheric Entry:
The projectile begins to breakup at an altitude of 37000 meters = 121000 ft
The projectile bursts into a cloud of fragments at an altitude of 18000 meters = 59100 ft
The residual velocity of the projectile fragments after the burst is 19.5 km/s = 12.1 miles/s
The energy of the airburst is 5.58 x 10^15 Joules = 1.33 MegaTons.
Large fragments strike the surface and may create a crater strewn field. A more careful treatment of atmospheric entry is required to accurately estimate the size-frequency distribution of meteoroid fragments and predict the number and size of craters formed.

Air Blast:
The air blast will arrive approximately 2.35 minutes after impact.
Peak Overpressure: 950 Pa = 0.0095 bars = 0.135 psi
Max wind velocity: 2.23 m/s = 4.99 mph
Sound Intensity: 60 dB (Loud as heavy traffic)

[Bill Harris]

It will be interesting to see what the "yield" of this bolide calculates out to be. I don't know how much of an exact correlation between the the yield of an atomic device and this asteroid will be. A bomb is designed to stay smallish and compact as the fission/fusion reaction is taking place and then the fireball can expand at it's own rate. An asteroid is either a rubble pile of coalesced fragments or a highly fractured rock. On atmospheric entry the surface is very hot and ablative while the interior is still deep-space cold, It holds together until the aerodynamic stresses cause it to rupture into many fragments. At that point the surface:volume ratio goes very high and who knows what the dynamics of that is.

At any rate, this was a nice surprise. In the media I've heard the size of the passing asteroid mistakenly listed as "half the size of a football" (not of a football field) and my first thought was "Ha, how ironic, this meteorite was probably half-football sized", but from what I read here, it was somewhat bigger.

We should be able to collect many fragments that made it to ground-- the snow ought to help spotting the impact sites.

--Bill

[Explorer1]

At 19 seconds in TheAnt's video (post 311), is that an actual shockwave visible, or just a reflection from the windshield? It doesn't show up in the other footage, so I'm inclined to the latter.

[helvick]

Why are we assuming that 1kPa is the level that would break glass/windows? All of the references I can find put the breaking glass level at around 5-10kPa overpressure but I assume there are other factors that would vary that in a shock wave scenario.

[Mongo]

Why are we assuming that 1kPa is the level that would break glass/windows? All of the references I can find put the breaking glass level at around 5-10kPa overpressure but I assume there are other factors that would vary that in a shock wave scenario.

I used this paper as a reference:

Table 1. Typical pressure indicators

Typical pressure for glass failure 1 kPa (10 millibar)
Minor damage to house structures 4.8 kPa (48 millibar)
50% destruction of brickwork ofhouse 17 kPa (170 millibar)
Rupture of oil storage tanks 27 kPa (270 millibar)
Severe crushing of cars 34 kPa (340 millibar)
Loaded train box cars completely demolished 62 kPa (620 millibar)
Probably total destruction of buildings 69 kPa (690 millibar)

This discussion has the following overpressures:

Overpressure*
(psig) Expected Damage
0.04 Loud noise (143 db); sonic boom glass failure.
0.15 Typical pressure for glass failure.
0.40 Limited minor structural damage.
0.50-1.0 Windows usually shattered; some window frame damage.
0.70 Minor damage to house structures.
1.0 Partial demolition of houses; made uninhabitable.
1.0-2.0 Corrugated metal panels fail and buckle. Housing wood panels blown in.
1.0-8.0 Range for slight to serious laceration injuries from flying glass and other missiles.
2.0 Partial collapse of walls and roofs of houses.
2.0-3.0 Non-reinforced concrete or cinder block walls shattered.
2.4-12.2 Range for 1-90% eardrum rupture among exposed populations.
2.5 50% destruction of home brickwork.
3.0 Steel frame buildings distorted and pulled away from foundation.
5.0 Wooden utility poles snapped.
5.0-7.0 Nearly complete destruction of houses.
7.0 Loaded train cars overturned.
9.0 Loaded train box cars demolished.
10.0 Probable total building destruction.
14.5-29.0 Range for 1-99% fatalities among exposed populations due to direct blast effects.

Since 1 kPa = 0.145 PSI, the kPa equivalents would be:

0.3 kPa Loud noise (143 db); sonic boom glass failure.
1.0 kPa Typical pressure for glass failure.
3.5-7 kPa Windows usually shattered; some window frame damage.

Some of the videos clearly show the window frames being heavily damaged and even crushed inward, suggesting an impact at the higher end of the overpressure range, but on the other hand the shock wave must also count as a sonic boom, lowering the needed overpressure by a factor of 3.5 or so. My best guess is that the damage normally expected from a 3.5 kPa overpressure is actually due to a 1 kPa sonic boom overpressure.

[machi]

Mongo:
I don't know how it's today, but in earlier times (20th century), lots of Soviet windows frames had very low quality.
Another thing. Blast wave is a wave. So it interferes and it's possible that some windows damage was caused by a local overpressure event, which can be result of superposition of waves.
Because lots of damage on the videos are only local in nature (windows are destructed only in some height over ground), I think that guesses in Mt range are exaggerated.

[Gladstoner]

.

[Mongo]

Russian meteor largest in a century -- Nature

A meteor that exploded over Russia this morning was the largest recorded object to strike the Earth in more than a century, scientists say. Infrasound data collected by a network designed to watch for nuclear weapons testing suggests that today's blast released hundreds of kilotonnes of energy. That would make it far more powerful than the nuclear weapon tested by North Korea just days ago and the largest rock crashing onto the planet since a meteor broke up over Siberia's Tunguska river in 1908.

"It was a very, very powerful event," says Margaret Campbell-Brown, an astronomer at the University of Western Ontario in London, Canada, who has studied data from two infrasound stations near the impact site. Her calculations show that the meteoroid was approximately 15 metres across when it entered the atmosphere, and put its mass at around 7,000 metric tonnes. "That would make it the biggest object recorded to hit the Earth since Tunguska," she says.

Although there are reports of fragments of the meteor, or meteorites, striking the ground, Klinkrad says that he believes the vast majority of damage in the region was caused by shockwaves of the explosion, as the rock broke up in the upper atmosphere. Campbell-Brown says that the infrasound data shows a very shallow angle of approach — a feature that funnelled much of the energy from the blast to the city below. Still, she adds, "It's lucky that there wasn't more damage."

The impact effects website I have been using says that the energy released during the major explosion, with these numbers, would be around 320 KT. Allowing for shock wave interference effects and shoddy Russian window construction, I suppose the observed damage is possible. Needless to say, it's still one heck of an explosion.

edit -- Since I wrote the above, I learned that:

The meteor entered the Earth's atmosphere at a hypersonic speed of at least 54,000 km/h and shattered about 30 to 50 kilometres above the ground, the Russian Academy of Sciences said in a statement.

It released the energy of 300 to 500 kilotons above the Chelyabinsk region, the academy said.

[machi]

Needless to say, it's still one heck of an explosion.

Yes it is.
In fact in terms of released energy it's comparable with strategic MIRV warhead.

[0101Morpheus]

Needless to say the little unexpected meteor that could stole the show from its bigger sibling that was in the news for almost a year. At the rate new footage is coming out it is going to take days to sort through this.

Police have found a crater in Chebarkul Lake. Probably a fragment that survived the explosion. It seems inevitable that they'll retrieve it but that depends how fast it was still going when it hit the water.

There's a photo of the crater on Phil's blog.

http://www.slate.com/blogs/bad_astronomy/2...rozen_lake.html

[PaulH51]

Meanwhile during Sol 187 in the sky above Gale Crater... Another incoming event?

link to image

[nprev]

Who knows? The Tunguska impactor left nary a trace, so it was probably composed largely of volatiles. This thing's composition will be known shortly, and my guess is that it's stony or it would've made a pretty good crater instead of breaking up at altitude.

[dvandorn]

I've been finger-licking the various videos, and I'm struck by the better views of the actual explosion. There is a flash and a rapid expansion of what looks like a spherical fireball, a very slight dimming, and a second much brighter flash in which the fireball expands enormously. As the fireball quickly dissipates, you see what looks like a very thin cloud of dark smoke that outlines a sphere about the size of the first fireball flash, which itself dissipates (or is drawn into the contrail) in less than a second.

The only lasting effect of the fireball was the thickening of the contrail. But the second flash of the double flash definitely generated a huge fireball that dissipated extremely quickly.

I wonder if the fireball was made entirely of gasses or plasma? Or if any fragmental debris in the fireball was actually pulled back into the contrail by the extreme vacuum created in the wake of the impactor?

I admit, I cheated a little bit in studying the fireball -- I found a youtube video that runs the best angles of the bolide's descent in slow motion:

https://www.youtube.com/watch?v=gW6JVG1SP4c

-the other Doug

[Bill Harris]

I don't know how it's today, but in earlier times (20th century), lots of Soviet windows frames had very low quality.

Another thing. Blast wave is a wave. So it interferes and it's possible that some windows damage was caused by a local overpressure event, which can be result of superposition of waves.

In my work as a hydrogeologist I had occasions to dabble in the (mining) blast effects on structures. One suggestion we saw was that in a tightly sealed building the walls (and windows) would flex more than if the building were not well-sealed in response to an overpressure event. It is Winter and even in a rural area urethane foam weatherstripping is available.

Yes, blast waves can be reflected and interfere constructively or destructively. Take a look at Don Davis' famous painting of the Tunguska event-- it shows blast waves reflecting. And the effects of a blast wave from an atomic explosion reflected off the ground are documented-- see Richard Rhodes' books on the making of the atom bomb.

--Bill

[Mongo]

NASA has revised upwards the size of the impactor and explosion:

New information provided by a worldwide network of sensors has allowed scientists to refine their estimates for the size of the object that entered that atmosphere and disintegrated in the skies over Chelyabinsk, Russia, at 7:20:26 p.m. PST, or 10:20:26 p.m. EST on Feb. 14 (3:20:26 UTC on Feb. 15).

The estimated size of the object, prior to entering Earth's atmosphere, has been revised upward from 49 feet (15 meters) to 55 feet (17 meters), and its estimated mass has increased from 7,000 to 10,000 tons. Also, the estimate for energy released during the event has increased by 30 kilotons to nearly 500 kilotons of energy released. These new estimates were generated using new data that had been collected by five additional infrasound stations located around the world – the first recording the event being in Alaska, over 6,500 kilometers away from Chelyabinsk. The infrasound data indicates that the event, from atmospheric entry to the meteor's airborne disintegration took 32.5 seconds. The calculations using the infrasound data were performed by Peter Brown at the University of Western Ontario, Canada.

[walfy]

It's amazing how today's trail resembles fairly well in some respects (thankfully, not all) the artist's visual approximation of the Tunguska event of 1908.



It would be interesting to see today's trail superimposed along a famous mountain chain, or city, to get an idea of its size. I would do it but I don't know how tall it is, or long.

Considering it's 30, 40? kilometers away in the above photo, it's a massive explosion high up there!

[Bill Harris]

Another measure of the energy imparted by this event:

Russian Meteor Shook Ground Like An Earthquake

A meteor explosion in the skies above Russia this morning also walloped the Earth, triggering shaking as strong as an earthquake, the U.S. Geological Survey (USGS) reports.

Today's early morning blast, centered on the Chelyabinsk region, sent massive tremors through the ground, which were recorded on seismic monitoring instruments around the world.

Initial reports pegged the explosion as similar to a magnitude 2.7 shaker, according a seismograph released by the USGS. For comparison, the 1908 Tunguska meteor blast's shock waves, which flattened 80 million trees in Siberia, produced the equivalent of an estimated 5.0 temblor.

http://news.yahoo.com/russian-meteor-shook...dF9BRkM-;_ylv=3

--Bill

[walfy]

According to this source, the main trail, or train, is around 320 km long (200 miles). Here it is superimposed above San Francisco, CA, and a 320 km swath of U.S. coastline, for a perspective.


Another one closer in to the city with a portion of the trail through which the horizon beyond is visible:

[xflare]

If it exploded/disintegrated that high above the ground, I would say people in the region had a VERY lucky escape. The Tunguska bolide is thought to have exploded 6-10km above ground. If this had done the same, I think we would have had a major disaster.

[Mongo]

If it exploded/disintegrated that high above the ground, I would say people in the region had a VERY lucky escape. The Tunguska bolide is thought to have exploded 6-10km above ground. If this had done the same, I think we would have had a major disaster.

From the science blog Dynamics of Cats:

Air has density of about 10^-3, at ground level decreasing approximately exponentially with scale height, and the scale height is of order 10 km. Therefore meteors tend to break up at 10-20 km altitude if they don’t make it to the ground. A 1 m rock needs to sweep a path of over 2 km through the air to stop effectively, a 12 m rock needs about 24 km of air to stop. So a rock that big coming straight down will likely hit the ground.

The Chelyabinsk meteor came in at a shallow angle, and so traversed a column of air long enough to brake it and break it. This is very fortunate, or we’d have had a ground detonation of a few hundred kilotons and likely mass casualties.

Most of the injuries seem to have been from broken glass, consistent with reports of other large explosions.

Glass breaks from overpressure of about 1/4 PSI – and as the bomb damage calculator (below) shows, that overpressure goes out to about 20 km radius (for ground detonations which this was not). Here we had an air detonation (worse) but with the energy spread out over a linear track, not deposited instantaneously at a point (both better and worse).

Hence the damage was consistent along the track and for tens of km either side of it, but nowhere was there a point or line of extreme destruction. A little bit higher energy impact, steeper impact angle, faster speed or bigger rock, and there would have been a zone of severe damage surrounded by an elongated annulus of the moderate damage actually seen, and there would have been many deaths.

[jgoldader]

Any news yet on the type of the impactor? I saw a couple of pictures of very dark bits in the ice around the hole at the lake, but couldn't tell if the darkness was fusion crust or not. Wondering if it was stony or a chondrite, perhaps something exotic like the Tagish Lake meteorite.

There was a bit on RT.com about divers being called in at the lake. But didn't the Tagish Lake meteorite turn out to be more or less water soluble?

Thanks,
Jeff

[ElkGroveDan]

This is a good graphic for those of you who do outreach.

Attached thumbnail(s)

 

[Mongo]

Interesting graphic, although the impactor is shown as far smaller than it actually was, 2m vs 17m.

[Paolo]

back to the other asteroid star of the week, has anybody seen any early result of the radar tracking of 2012 DA14?

[djellison]

As you can see - they're planning to observe it for several days. I'd expect results wouldn't be released until they're finished
http://gssr.jpl.nasa.gov/Calendar/month.php

[Gladstoner]

.

[nprev]

That's a good one!

Been trying to figure out the secondaries as well. They don't really sound like echoes, and the local topography seems pretty flat (although the Urals are nearby). My best guess is that they're the shock waves from fragments after the explosion that are still supersonic.

[Gladstoner]

.

[dvandorn]

I think the first loud report may have been from the explosion itself. The continuing popping sounds were likely sonic booms created by the remaining relatively large pieces of the impactor as they flew on along the trajectory of the original bolide. The fact that the contrail splits into two distinct contrails for the length of it that was left during the fireball phase of the entry (i.e., when the original object exploded) shows that at least two streams of debris came out of the fireball and recombined into a single, more coherent stream after the fireball faded.

Of course, not all of the debris followed the main stream, lots of pieces big enough to cause sonic booms likely flew out in a multitude of different directions, and many to most of them would still be traveling at supersonic speeds.

-the other Doug

[Mongo]

All the videos I have seen that continue past the arrival of the main shockwave include a lengthy string of smaller bangs and thumps, some of them quite large in their own right. It seems clear to me that they are the result of secondary explosions as the main meteoroid fragments into smaller and smaller pieces. Unlike a nuclear explosion, a meteoric explosion is not a single event (unless it actually happens at ground level), but a cascading series of increasingly smaller and more numerous events, happening at varying distances from the listener.

[helvick]

Thunder rumbles aren't generally echoes, just the delayed arrival of the shock wave from points along the strike that are further from you and travelling through fairly chaotic air ( initially at least ).
This should be similar, this thing was hypersonic ( mega sonic?) at 100's of km out, rapidly decelerating to merely supersonic by the time it passed overhead. At 30 km altitude it would have taken about 2 minutes for the shock to reach ground directly beneath the closest point below the main explosion, with earlier shocks gradually catching up, and being increasingly faint over the following minute or two as they caught up. The pops and barrage effect could be just interference along the path but I think its reasonable to assume that there were fragments spalling off and exploding all along the track up to the main fireball providing most of the variation in that recording. The speed of sound is very slow when you are hearing stuff from 30-60 km away, and that looked like a very bumpy ride in to me, even before the main event.

[Gladstoner]

.

[Eyesonmars]

I found it interesting that a number of witnesses mentioned feeling the radiant heat of the fireball. A little bigger and we would have had some objects charred on the ground beneath the fireball. How much bigger ?? Even so, the shock wave would have probably extinguished any fires. Much like what happened at Tunguska.

[nprev]

Do you have any references for the heat perceptions? I would be quite surprised by that given the altitude of the detonation plus slant range(s).

[Bill Harris]

Thunder rumbles aren't generally echoes, just the delayed arrival of the shock wave from points along the strike...

That is what I had concluded and was going to post here. And remember although the contrail looks like it is just up on the ceiling, it is many miles long and every part of it has a different range in miles and therefore arrival times. And when the object disintegrated, there were thousands of fragments released, each making their own shock wave.

And the videos confirm the conceptual model of the object disintegrating. As it entered ( I keep wanting to say "reentry") it was solid and made a compact plasma sheath perhaps 30 meters diameter. The smoke trail is ablated silicates that have condensed. When the object ruptures it immediately creates thousands of fragments ranging size from boulders to dust, each with it's own aerodynamic characteristics and trajectory and the surface:volume ratio increases rapidly and so does the amount of material being ablated. The plasma sheath rapidly expands due to the unconstrained fragments and the increase in the volume of plasma from vaporized silicates and whatever volatiles were entrained in the rock.

Whew. It's mind-boggling.

--Bill

[tasp]

I noticed in the different clips shown the degree of camera saturation varied quite a bit. Some of the slower responding imagers totally whited out, and others seemed to have AGC circuits that tried to follow the illumination level.

I was wondering if any photo analysis has been done yet to determine a decel rate along the path for the rock. It would be interesting to have some idea what it withstood before the fragmenting started.

And maybe decel, heating, and turbulence weren't the only effects on it, maybe it was aerodynamically asymmetrical and the slipstream was starting to spin it up some ?

[Mongo]

Do you have any references for the heat perceptions? I would be quite surprised by that given the altitude of the detonation plus slant range(s).

I don't have links myself, but I do recall reading reports that mentioned that people felt heat coming through the windows. One person mentioned that curiosity over this unusual heat was what attracted them outside before the shockwave hit. If the fireball was indeed as bright as the sun or brighter, as seems to be the case, then the infrared radiation should be roughly in proportion, so I would not be surprised if there was a short burst of heat when the main explosion happened.

[Bill Harris]

Do we have any scale information on the cameras used to photograph the Russian bolide? Do we have any idea of the physical dimensions of the dust trail/debris trail (I don't think it's technically a contrail) I've looked at a lot of photographs and videos and I can't get a handle on how to scale the trail. My TLAR sense tells me that it's huge.

--Bill

[walfy]

...I've looked at a lot of photographs and videos and I can't get a handle on how to scale the trail. My TLAR sense tells me that it's huge.

Check out this page for its scale: http://attivissimo.blogspot.ch/2013/02/rus...-in-google.html
I attempted to scale it here.

For what it's worth, I did a quick extraction of 6 sonic boom soundtracks of the meteor from YouTube to see if I could find some similarity between them, at least in the timing of the biggest booms. But nothing stood out as a clear match between any two of them, except for the initial boom, of course! Maybe if a bit more time were spent some similarities could be extracted. But no similarity in the timing and sequence of the booms stands out between any of them with a quick listening or when looking at first 11 seconds of their waveforms:



Of course, there's some glass shattering or car alarms at the beginning of some of them, but some were taken with minimal background noise with the booms standing out. But no pattern. It sounds really different from each location. When all soundtracks play at once, it's a calamity – for the ears!

Something that does stand out is that recordings made closest to the vapor trail almost sound like gunfire or quick and snappy fireworks booms; more distant ones sounded like thunder, "muffled" but still loud.

[walfy]

ONe more thought for the night: it would be a great study to survey glass breakage under this meteor. I suspect that fewer panes shattered directly below it then to the surrounding immediate vicinity, similar to the trees that still stood under the central blast of Tunguska years ago.

[FordPrefect]

Some interesting photos on this photographers blog, who just happened to be outside to do nature photography:


Link

In that photo and the following, it really looks like there are fireball/explosion-like segments visible inside the train still glowing?


Link

And an air-to-air image of the train. See the colour variation on the nearer (left) part of the train? It changes from brownish to blueish hues, indications of different materials being vaporized during its "melt off" process?


Link

[Paolo]

As you can see - they're planning to observe it for several days.

I had googled that. I was just expecting that, given the media hype, they would be releasing early results in quasi-real time like they did with Toutatis last December

[ugordan]

When the object ruptures it immediately creates thousands of fragments ranging size from boulders to dust, each with it's own aerodynamic characteristics and trajectory and the surface:volume ratio increases rapidly and so does the amount of material being ablated.

This is the explanation I subscribe to as well. Each of those separate fragments would see a significantly different deceleration depending on its ballistic coefficient so the fragment train would quickly spread out in along-track direction, creating all those distinct, subsequent booms.

[Mongo]

For what it's worth, I did a quick extraction of 6 sonic boom soundtracks of the meteor from YouTube to see if I could find some similarity between them, at least in the timing of the biggest booms. But nothing stood out as a clear match between any two of them, except for the initial boom, of course! Maybe if a bit more time were spent some similarities could be extracted. But no similarity in the timing and sequence of the booms stands out between any of them with a quick listening or when looking at first 11 seconds of their waveforms:

This does not surprise me. Each individual explosion would have happened at a different location in the air, and hence would be a different distance from the listener, with the distance to each explosion varying with the listener's location. A given shock wave would change its time of arrival relative to that produced by a different explosion, even changing from being earlier to being later than the second shock wave, depending on the location of the listener. So the sequence of bangs and booms would be different at each location on the ground.

[dvandorn]

...Each of those separate fragments would see a significantly different deceleration depending on its ballistic coefficient so the fragment train would quickly spread out in along-track direction, creating all those distinct, subsequent booms.

Exactly the point I made. The multiple booms were sonic booms created by the fragments of the original impactor after the initial explosion.

-the other Doug

[Bill Harris]

...it really looks like there are fireball/explosion-like segments visible inside the train still glowing?

Yes! I noticed those "redder" areas in the initial videos and attributed them to redder light where the blue had been scattered by very small particles (a "sunset effect"). But later-presented and better quality photos do indeed show that the red is incandescent-- I was not expecting the heat to be retained that long, but it's only a very few seconds after the fireball had passed.

--Bill

[ugordan]

This video shows nicely that incandescence nicely.

[Art Martin]

I've seen a number of videos of a flaming crater in the ground but none of them appear on any reputable news stations. Does anyone know the validity of those videos? I don't want to embed the link here because one would think that it would be a prime feature if valid. The hole in the ice images seem to be taken more seriously.

[Mongo]

Those videos and images of a flaming crater are real, but they have nothing to do with any meteorite impact. Apparently they are of a fire that has been burning mostly underground for years.

[Art Martin]

Those videos and images of a flaming crater are real, but they have nothing to do with any meteorite impact. Apparently they are of a fire that has been burning mostly underground for years.

I suspected as much, that the people posting them saw an opportunity to get noticed by tagging them onto this event. The edges of the crater are too defined. You'd expect that the ground would be more ragged and the debris splayed out around it if it were a strike. How about the ones of the hole in the ice that seem to be a bit more reported?

[Explorer1]

The lake impact is probably authentic, but it might be a while before anything is hauled off the bottom!
Art Martin, I expect any land impact to look kind of like the crater left by the impact in that field in Peru (Carrancas); just a big dirty hole, maybe with water filling up the bottom. Plenty of pictures of that one.

[silylene]

Stefan Geens did a nice job computing the trajectory. Shallow grazer!
cool animated gif of shadows moving as meteor passes to give trajectory calculation

trajectory to impact picture

Geen's trajectory can be displayed in this google earth kmz file.

Geen's estimate is that the meteor passed near Chelyanbinsk at 03:15:00 UTC.

Meanwhile there was a 6.8 earthquake in Syagannakh Russia at 08:17:00 UTC. link. Interestingly, and coincidentally, this earthquake lies close to the trajectory path of the meteor (maybe 15 degrees off the path?). Compare Geen's trajectory to the google earth location of the quake.

The quake was 5 hours later however, which make the quake very likely coincidental and nothing more.

If a second meteor had been following the Chelyabinsk meteor, 5 hours later, and impacted near Syagannakh, that would be amazing. Highly unlikely, but it is an uninhabited region, and maybe there were no public reports (one would have to assume if it happened, this putative hit would have lit up the defense grids of both Russia and the US). Still, it might be worth checking if anything unusual happened near Syagannakh (which looks like lake strewn tundra in Google maps).

quake link
earthquake

[Bill Harris]

I've seen a number of videos of a flaming crater in the ground...

I read about that and it is a well-known burning natural gas methane seep in Russia. After I rolled my eyeballs back down, I looked it up but don't seem to have Bookmarked it. I'll look it up and post more.

How about the ones of the hole in the ice that seem to be a bit more reported?

That seems to be authentic. I've read that divers have been down and have recovered nothing, yet. I'm sure they'll keep looking-- samples of the impactor will help in determining the dynamics of the event.

Stefan Geens did a nice job computing the trajectory

Brilliant job of sleuthing!

You can "see" the descending path in the aircraft photo in FordPrefect's images posted in Msg#356.

--Bill

[Art Martin]

One thing that I've noticed in the cloud the meteor created is that it appears to break up into two pieces early and then those clouds converge into one again as the main explosion occurs which brings up the question, did only one of those pieces explode explaining the remaining fragments that continued to the ground. All I know is the videos are fascinating and those folks were so lucky the thing wasn't just a bit bigger.

[ugordan]

I have a theory about the twin cloud trail. I'm wondering if it was convection that split it in two. When you have a spherical mass of hot air (like a nuclear fireball), convective movement and resulting vacuum effects quickly produce a rotating toroidal cloud. Maybe what we see here is is what happens with a "cylindrical" fireball? It splits into two, like a cross section of a toroidal cloud?

[stevesliva]

The quake was 5 hours later however, which make the quake very likely coincidental and nothing more.

If a second meteor had been following the Chelyabinsk meteor, 5 hours later, and impacted near Syagannakh, that would be amazing. Highly unlikely, but it is an uninhabited region, and maybe there were no public reports (one would have to assume if it happened, this putative hit would have lit up the defense grids of both Russia and the US). Still, it might be worth checking if anything unusual happened near Syagannakh (which looks like lake strewn tundra in Google maps).

The depth of the quake ought to be known-- probably not at the surface-- and those folks reporting magnitude estimates from infrasound sensors would probably not forget to mention a second set of booms 5hrs later.

[ngunn]

I have a theory about the twin cloud trail. I'm wondering if it was convection that split it in two.

Sounds spot on to me. The two halves were too well matched, therefore unlikely to be due to separate objects, so I had already started to wonder if 'double' was 'normal' for these things for some reason. Your explanation fits perfectly.

[Mongo]

The USGS does report a seismic event that originated a few minutes after the fireball happened, directly under the fireball:



Chelyabinsk Meteor Explosion Caused Magnitude 4 Earthquake

(Newsroom America)-- The meteor which exploded above Chelyabinsk in Russia two days ago was measured as a magnitude 4 earthquake, according to the United States Geological Survey (USGS).

USGS said the meteor explosion occurred at approximately 03:20:26 UTC or 9:20:26 am local time.

[Bill Harris]

I read about that and it is a well-known burning natural gas methane seep in Russia. After I rolled my eyeballs back down, I looked it up but don't seem to have Bookmarked it. I'll look it up and post more.

The video that I saw in another site has been removed by the user, but I applied my Google-Fu and found that it is a burning natural gas seep in Derweze (Darvaza) Turkmenistan known as "The Door to Hell". Google "door to hell derweze turkmenistan" for more info than we all need to know...

Wiki link at: http://en.wikipedia.org/wiki/Door_to_Hell which mentions "A short video of the Door to Hell has been circulating on the internet, falsely identified as the impact site for the 2013 Russian meteor event."

--Bill

[walfy]

I don't know if this has been discussed yet, and maybe don't understand this well enough, but the succession of booms heard from the ground might have been in reverse order for most locations where it was heard. Especially directly under the main trail. The meteor came punching into the atmosphere well beyond the speed of sound, so all propagating explosions and shock waves could not keep up with the front of the train. Let's say you were standing directly below that main explosion that remained incendiary for a few seconds. The shock wave from that would hit you first. What about all the other smaller shock waves preceding it? They would then strike your ears in succession, but in reverse order than actual time of origination.

The series of booms heard is the actual sound of the meteor's entry, but played out in reverse! For example, the first explosion of the meteor itself was the highest up there, and so will reach the ground last, since the train is moving much faster than speed of sound.

This illustration comes to mind: Imaging being in a hot air balloon above a lake and spraying a machine gun in a direct line from one shore of the lake to the opposite shore. The waves from the last bullet shot will wash ashore first on that opposite side of lake, followed by the rest of them in reverse order. The first bullet fired will have hit that far shore last.

Maybe there's something completely fundamental I'm overlooking. the idea seems too strange...

[AndyG]

That's the way (and why) nearby lightning strikes rumble on: you hear the closest part of the near-instant flash first, followed by more distant sound "catching up".

Andy

[Bill Harris]

I've been doing some reading and the closest "terrestrial" analog to the dust trail left by the Russian bolide is a nuee ardente (literally, "glowing cloud") pyroclastic flow, at least the lighter airborne fraction and not the ground-hugging surge:

nuee ardente

1) glowing avalanche (lower denser part)
2) Lighter fraction of volcanic gases, ash, and dust which cauliflower upwards.

http://www.volcanolive.com/a.html

A quickie Google link on this is: http://www.google.com/search?q=nuee+ardente

As the meteorite disintegrated and ablated it became, literally, a plasma of vaporized basalt plus volatiles and gasses which immediately started to condense into a basaltic (volcanic) ash with very hot gasses which was quite buoyant and made the observed cauliflower clouds along the trail. Parts of the cauliflower puffs were still incandescent (literally seconds after formation), which sets a range of temperatures. I've been looking at a lot of images of the "nuee ardente" flows but haven't seen any that are still glowing (not a surprise, we're seeing a volcanic eruption late on the game).

This event is going to make for a some great papers at next year's LPSC...

--Bill

[pandaneko]

I have not read all of the previously uploaded contributions, so my apologies, in advance, if I am duplicating similar articles again.

Not this one, of course, but let us say, some of the future incoming bodies like this are rotating in their own frame of reference what do we do then?

People talk about painting these asteroids, or attaching ion engines to them in the hope of deflecting their orbits in the long run. Can we do that when they are rotating around their own axis?

Pandaneko

[AndyG]

Rotation helps for larger asteroids of a rubble-pile, gravitationally-bound, construction. Painting an asteroid black would result in the warmed surface emitting IR to a higher degree during the "dusk" side of rotation compared to the "dawn" side. Given time an orbit could be adjusted.

The problem with smaller objects, such as this Russian one - presuming they're solid rock chunks - is that the rotation rate could well be significantly above that of a gravitationally-bound body, reducing the benefit of paint.

Rotation. Hmmm. Just a thought to Art and ugordan - do the twin trails seen here reflect the equivalent of "tip vortices" generated by the lift of a rotating body?

Andy

[remcook]

Apparently, fragments have now been found http://en.ria.ru/russia/20130217/179531203...Scientists.html

[Bill Harris]

Yep, "fragments found" and now we're going to see the squirrels come out of the woodwork with eBay sales.

"Meteorite rush" begins as Russian scientists find fragments
http://news.yahoo.com/meteorite-rush-begin...dF9BRkM-;_ylv=3

But it is good that (actual) fragments are turning up. It gives an idea of the composition, and therefore the type of asteroid and the structure and a better understanding of the dynamics of the breakup. From the Russian scientists involved, "These are classified as ordinary chondrites, or stony meteorites, with an iron content of about 10 percent..."

I liked this comment:

"I will keep it. Why sell it? I didn't have a rich lifestyle before, so why start now?" a woman in a pink woolen hat and winter jacket, clutching a small black pebble, told state television Rossiya-24.

This is not surprising. When the object disintegrated it didn't completely flash into plasma. No doubt many small fragments were decelerated quickly and fell along the flight path in a ballistic trajectory. I look at the object as being converted into a flying gravel pile-- even if only 1/10 of 1% survived, that is a lot of meteorites!

--Bill

[dvandorn]

There is likely a rather large "strewn field" where fragments of the meteor landed. I wonder if the Discovery Channel is in negotiation to film a segment or two of the series "Meteorite Men" in Siberia?

-the other Doug

[stevesliva]

There is likely a rather large "strewn field" where fragments of the meteor landed. I wonder if the Discovery Channel is in negotiation to film a segment or two of the series "Meteorite Men" in Siberia?

Chelyabinsk isn't in Siberia, though, right? This is too far south to be siberian.

[Explorer1]

The boundaries and definitions are rather fuzzy; in terms of federal districts, its actually part of it. If Siberia is defined as east of the Urals than yes. Scroll down here to see Chelyabinsk listed: http://en.wikipedia.org/wiki/Siberia#Borde...rative_division

[Pertinax]

What kind of confidence is reasonable with the infrasound estimates of the airburst? On a similar note, does anyone have a cold-war era air-burst calculator (such as http://calculating.wordpress.com/2012/05/0...computer-no-1/) to see what effects a 500kT explosion at ~85,000ft would have at various ranges?

Part of my reason for asking is that given the approximations from Collins et al (http://impact.ese.ic.ac.uk/ImpactEffects/effects.pdf), a larger blast seems necessary to produce the observed ground effects (assuming I am not making some bonehead mistake(s), which might not be a safe assumption ).

Using the most recent published numbers, I get:
http://impact.ese.ic.ac.uk/cgi-bin/crater....&tdens=2500

... while the following seems to reproduce the knows better (using http://ogleearth.com/2013/02/reconstructin...gh-school-math/ and http://www.youtube.com/watch?v=gQ6Pa5Pv_io...player_embedded as references):

http://impact.ese.ic.ac.uk/cgi-bin/crater....&tdens=2500


Thoughts?


-- Pertinax

[Mongo]

Thoughts?

One thing I have found is that "distance from impact" in that program means "horizontal ground distance from directly under the explosion". If you enter 0.1 km instead of 44.3 km, the results are much closer to the expected numbers, especially if you use the revised density of 3957 kg/m^3 to give a mass of 10,000t, and a velocity of 32.5 km/s to produce an energy release of 500 kilotons, with an 89s travel time for the shock wave to reach the ground.

[ugordan]

On a similar note, does anyone have a cold-war era air-burst calculator (such as http://calculating.wordpress.com/2012/05/0...computer-no-1/) to see what effects a 500kT explosion at ~85,000ft would have at various ranges?

There's a piece of software that runs in DOS and it uses models based on empirical data, but I don't think it would have produced meaningful overpressure values at those airburst altitudes since the data it was fed was based on much lower airburst data, typical of altitudes a weapon would effectively be used in combat, not 27 km.