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

[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