Not quite Tunguska, but...

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Not quite Tunguska, but...

Postposted on Fri Feb 15, 2013 3:54 am

Still pretty spectacular: apparently a meteor entered the atmosphere and broke up over Russia in the early morning (local time) and the videos are flooding in (Russian dash-cams: not just for combating insurance fraud!)
There are reports the sonic boom blew out some windows resulting in injuries from falling glass.
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Re: Not quite Tunguska, but...

Postposted on Fri Feb 15, 2013 4:10 am

Yea, I've read that on original news sites :P Here are some more photos:
http://lenta.ru/photo/2013/02/15/chelly/#0
Lots of broken windows, some minor injuries, no casualties.

Of course, since it's still trendy to hate on America in Russia, the most famous political "clown" there already blamed teh explosion on "super secret American weapon test":
http://lenta.ru/news/2013/02/15/react/ (Russian article)
:lol:


Edit: this is the best captured video of these meteors:
http://www.youtube.com/watch?v=Kps_CkEEkUo&sns=em
:wink:
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Re: Not quite Tunguska, but...

Postposted on Fri Feb 15, 2013 6:19 am

Very cool vids !! Thanks for sharing.
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Re: Not quite Tunguska, but...

Postposted on Fri Feb 15, 2013 7:25 am

Holy crap! That is amazing! I was expecting a lot of news about DA14 today but I was not expecting this... Related? Probably not but wow... Who would have guessed?
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Re: Not quite Tunguska, but...

Postposted on Fri Feb 15, 2013 8:18 am

Looks like a ~500lb bomb dropped at ground zero.

Makes you wonder how often a meteorite of this magnitude hits the Earth's surface on annual basis?
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Re: Not quite Tunguska, but...

Postposted on Fri Feb 15, 2013 8:29 am

HOLY CRAP DUDE!

I'm assuming this particular rock was completely outside of everybody's radar. LEONEO program definitely needs more funds, and if they set up distributed computing i'd be happy to donate cpu cycles.
Last edited by jihadjoe on Sat Feb 16, 2013 5:22 am, edited 1 time in total.
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Re: Not quite Tunguska, but...

Postposted on Fri Feb 15, 2013 8:46 am

Holy sheet! I wonder if people thought they were being attacked? Any vids on the impacts?
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Re: Not quite Tunguska, but...

Postposted on Fri Feb 15, 2013 9:07 am

jihadjoe wrote:HOLY CRAP DUDE!

I'm assuming this particular rock was completely outside of everybody's radar. LEO definitely needs more funds, and if they set up distributed computing i'd be happy to donate cpu cycles.

When they come in from a random direction at 19 miles per second, you've got no time to find them. Since the size estimate of this rock was around 10 tons, it's the type of rock that will never be detected by any means until it's in the atmosphere.

And no, it has nothing to do with the asteroid that'll be passing inside the Clarke Belt today. Different orbit all together.
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Re: Not quite Tunguska, but...

Postposted on Fri Feb 15, 2013 9:42 am

Captain Ned wrote:When they come in from a random direction at 19 miles per second, you've got no time to find them. Since the size estimate of this rock was around 10 tons, it's the type of rock that will never be detected by any means until it's in the atmosphere.
QFT.

And apparently the largest bomb was only ~500 lbs? That's a lot of mass getting burned and broken off. I can't tell what the "not serious" injuries are that end up totaling 700-800, but I would guess that has more to do with broken glass than getting hit by meteorites and shockwaves.

Spectacular, yes. Deadly, not so much.
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Re: Not quite Tunguska, but...

Postposted on Fri Feb 15, 2013 9:51 am

I think the jury is still out on just how large this one was - but we have spotted pretty small ones coming in the past.
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Re: Not quite Tunguska, but...

Postposted on Fri Feb 15, 2013 9:55 am

tanker27 wrote:Holy sheet! I wonder if people thought they were being attacked?


We're all damned lucky this didn't happen during the Cold War. For instance: http://en.wikipedia.org/wiki/Stanislav_Petrov
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Re: Not quite Tunguska, but...

Postposted on Fri Feb 15, 2013 10:13 am

Wow that's pretty amazing. The video with the meteor streaking across the skies was particular eye-opening.
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Re: Not quite Tunguska, but...

Postposted on Fri Feb 15, 2013 5:12 pm

NASA has now estimated 7,000 tons and a 50-foot diameter, with an explosion equivalent of "hundreds of kilotons". They also say it's the largest since Tunguska.

http://www.jpl.nasa.gov/news/news.php?release=2013-061
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Re: Not quite Tunguska, but...

Postposted on Fri Feb 15, 2013 8:40 pm

Tunguska-sized events are expected about once every 1200 years, yes?
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Re: Not quite Tunguska, but...

Postposted on Fri Feb 15, 2013 10:42 pm

I wish I was fluent in russian
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Re: Not quite Tunguska, but...

Postposted on Fri Feb 15, 2013 11:51 pm

NPR had a great interview with one of the project (I believe) coordinators of the Sentinel Mission. It is a privately funded operation that will be putting a detector in a venus-like orbit around the sun to detect 90% of asteroids 140 meters or greater in size. It will be able to locate a massive amount of objects down to 30 meters.

In the interview the guy said that they have had their first review of the detectors in January, and that the project is on track for a 2017-2018 launch. Their is a lot of good info on the website above :)
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Re: Not quite Tunguska, but...

Postposted on Sat Feb 16, 2013 12:22 am

LaChupacabra wrote:NPR had a great interview with one of the project (I believe) coordinators of the Sentinel Mission. It is a privately funded operation that will be putting a detector in a venus-like orbit around the sun to detect 90% of asteroids 140 meters or greater in size. It will be able to locate a massive amount of objects down to 30 meters.

In the interview the guy said that they have had their first review of the detectors in January, and that the project is on track for a 2017-2018 launch. Their is a lot of good info on the website above :)


... Ok, and if it'll detect an asteroid few miles in diameter, heading straight to Earth, then what? What will be the point of detecting it? Bruce Willis is already too old to do anything :wink:
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Re: Not quite Tunguska, but...

Postposted on Sat Feb 16, 2013 5:25 am

JohnC wrote:... Ok, and if it'll detect an asteroid few miles in diameter, heading straight to Earth, then what? What will be the point of detecting it? Bruce Willis is already too old to do anything :wink:


It lets us know when to do all the YOLO stuff we've been putting off. :D
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Re: Not quite Tunguska, but...

Postposted on Sat Feb 16, 2013 11:48 am

That's some crazy stuff there! :o

OK, so this one was big, but not big enough to cause serious devastation. The damage wasn't any worse than that caused by the sort of natural disasters we regularly see from purely terrestrial causes. What's the gap between the size of object we can detect, and the size of object that would cause unprecedented destruction? Can we narrow that gap to zero at a manageable cost? And if so, should we, unless we are also willing to fund technology to deflect at least the smallest of the potential "killer size" objects?
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Re: Not quite Tunguska, but...

Postposted on Sat Feb 16, 2013 12:34 pm

just brew it! wrote:OK, so this one was big, but not big enough to cause serious devastation.

500 kilotons not big enough? The only reason those dash-cam vids got uploaded and Chelyabinsk is still around is the height of the explosion (30-50 km under current estimates). If that thing holds together into the lower atmosphere and explodes at 10km there would have been serious devastation. Given its velocity (18 km/sec per NASA) and impact angle (15 degrees seems to be the consensus estimate), my rusty trig (and I'm not even going to attempt spherical trig) tells me that 18km/sin 15 degrees = 4.66 km altitude loss per second. That give a range of 4.3 to 8.6 additional seconds of flight time to get to a 10km burst altitude. No, those people got off extremely lucky.

http://www.nasa.gov/mission_pages/aster ... 30215.html
http://en.wikipedia.org/wiki/2013_Russian_meteor_event
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Re: Not quite Tunguska, but...

Postposted on Sat Feb 16, 2013 12:48 pm

That's a little misleading since the 500kt is the total energy released over the entire event.
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Re: Not quite Tunguska, but...

Postposted on Sat Feb 16, 2013 1:02 pm

ChronoReverse wrote:That's a little misleading since the 500kt is the total energy released over the entire event.

OK, say 250kt at 10km. Still a Bad Day.

Unfortunately, none of the web-based blast calculators I can find allow you to set the blast altitude. It takes about 1 PSI overpressure (blast wave) to blow out windows like we saw in the vids. At 5 PSI overpressure, most of those buildings would have been blown down. Since I'm not a weaponeer, I don't know the right math to calculate the change in overpressure caused by a potential reduction in blast altitude.
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Re: Not quite Tunguska, but...

Postposted on Sat Feb 16, 2013 1:06 pm

Captain Ned wrote:
just brew it! wrote:OK, so this one was big, but not big enough to cause serious devastation.

500 kilotons not big enough?

No deaths (as far as we know so far). Damage seems to be limited to blown out windows and the like. I would say it did not cause "serious devastation".
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Re: Not quite Tunguska, but...

Postposted on Sat Feb 16, 2013 1:11 pm

just brew it! wrote:
Captain Ned wrote:
just brew it! wrote:OK, so this one was big, but not big enough to cause serious devastation.

500 kilotons not big enough?

No deaths (as far as we know so far). Damage seems to be limited to blown out windows and the like. I would say it did not cause "serious devastation".

And the point I'm trying to make is that another 5 seconds of flight time and we'd most likely be charting many deaths. We got lucky. This rock had the potential to cause massive damage, and that's all I'm trying to get across.
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Re: Not quite Tunguska, but...

Postposted on Sat Feb 16, 2013 1:18 pm

Ahh, OK. Emphasis on the word "potential". Got it!
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Re: Not quite Tunguska, but...

Postposted on Sat Feb 16, 2013 1:19 pm

Who knows. The air is thicker down low so a different angle could have resulted in an entirely different pattern of breakup. If it had come straight down for instance, it might not have had time to explode at all. Or it could have exploded just at the optimal height for maximum airburst damage.


I couldn't find anything to calculated the explosive overpressure either except this one: http://stardestroyer.net/Resources/Calc ... sions.html

For 0.5MT you get 4.6psi at 5.7km. Air blasts are inverse cube root right? So that would put 12km close to 1psi?
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Re: Not quite Tunguska, but...

Postposted on Sat Feb 16, 2013 1:24 pm

ChronoReverse wrote:I couldn't find anything to calculated the explosive overpressure either except this one: http://stardestroyer.net/Resources/Calc ... sions.html

For 0.5MT you get 4.6psi at 5.7km. Air blasts are inverse cube root right? So that would put 12km close to 1psi?

Just like all of the calculators I googled it assumes optimum burst height, which is defined as the height that produces the greatest area of 10 PSI overpressure. Any potential blast we're talking about here is well above optimum, meaning a smaller 10 PSI area. What I'd really like to be able to model are the 5 PSI curves for varying blast heights in the range of 250-500 kt.
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Re: Not quite Tunguska, but...

Postposted on Sat Feb 16, 2013 1:27 pm

To get an accurate picture wouldn't you also need to account for the fact that an asteroid/meteor doesn't explode the same way TNT does? Or is that already accounted for in the 500 kT estimate?
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Re: Not quite Tunguska, but...

Postposted on Sat Feb 16, 2013 1:32 pm

just brew it! wrote:To get an accurate picture wouldn't you also need to account for the fact that an asteroid/meteor doesn't explode the same way TNT does? Or is that already accounted for in the 500 kT estimate?

My guess is that the 500 kT is simply blast effect comparison. Radiation effects are right out. Blast overpressures shouldn't be too far off, and I'd expect thermal effects to be quite reduced from nuclear effects due to the lack of the multi-million degree fireball. The blast overpressures are what I'm most curious about as they'll be the key damage component for an air-burst rock.

Given the wide area over which windows were broken there was clearly a very large 1 PSI overpressure area. Don't know if there was any way to measure max overpressure directly below the hypocenter through dash-cam or security cam footage. It'll probably get sussed out over the next few weeks as the custodians of big bangs look through all the data they can gather given that they can no longer test big bangs, especially above-ground.
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Re: Not quite Tunguska, but...

Postposted on Sat Feb 16, 2013 1:38 pm

Captain Ned wrote:
ChronoReverse wrote:I couldn't find anything to calculated the explosive overpressure either except this one: http://stardestroyer.net/Resources/Calc ... sions.html

For 0.5MT you get 4.6psi at 5.7km. Air blasts are inverse cube root right? So that would put 12km close to 1psi?

Just like all of the calculators I googled it assumes optimum burst height, which is defined as the height that produces the greatest area of 10 PSI overpressure. Any potential blast we're talking about here is well above optimum, meaning a smaller 10 PSI area. What I'd really like to be able to model are the 5 PSI curves for varying blast heights in the range of 250-500 kt.

Yeah =/

I'm still skeptical that the explosion sound is actually the blastwave of the explosion though. The ranges here are so far off that it seems rather unlikely. For example, in one of the videos with the blast breaking glass, there's about 30 seconds between flash and the boom so that's 10km. But we know the meteor exploded 30km over the earth and this video is from a distance making it even more than 30km.
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