Author Topic: Meteor Strikes Chelyabinsk, Russia  (Read 140705 times)

Offline JimO

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Re: Meteor Strikes Chelyabinsk, Russia
« Reply #380 on: 02/19/2013 12:26 PM »
I posted this on a different discussion board but some readers here needed to see it, to:
-------

There are some fundamentally wrong assumptions about meteors being used here as the basis for some wild time-wasting speculations.

Mainly this: claiming that the 'trail' was the result of material from the object. Or 'smoke'. Or dust, or condensation.

Actually, although occasionally tinged with combustion products, the main white trail of fireball meteors actually  is ionized atmospheric constituents. Torn-apart oxygen and nitrogen molecules, ionized by the extreme heat of the compressive shock wave

So naturally the trail can wax and wane and vanish purely as a function of the quickly varying speed and area of the entering object.

Nothing better illustrates this than the space shuttle, which left magnificent trails across the night skies of Texas on many entries to Florida landings in the 1980s and 1990s, and of course, sadly, over East Texas on February 1, 2003. With my family, I observed more than half a dozen such overflights with my own eyes.

And it left these trails without losing ANY material, NO chemical or dust or smoke coming off. JUST tearing apart the atmosphere as it passed, leaving a white trail that gradually dissipated over a period of minutes as the atoms rejoined into N2 and O2 molecules.

JUST LIKE over Chelyabinsk.

See a compilation of eyewitness descriptions of such a space shuttle entry, here:
http://www.jamesoberg.com/96mar-sts72_entry.pdf

I hope this helps attain a proper understanding of, and interpretation of, the Chelyabinsk meteor trail and its implications.

Offline kevin-rf

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Re: Meteor Strikes Chelyabinsk, Russia
« Reply #381 on: 02/19/2013 12:43 PM »
Honestly, we are talking about multiple different threats.

NEO's over 1km >95% identified, mitigation possible without nukes.
NEO's over 100m 5% identified, better search (IR space based, ect) needed, mitigation possible on known objects without nukes, objects identified late... pucker factor.

NEO's < 100m, while we tract asteroids down to 5 meters, they are outside of what we can reliably detect years in advance. They usually don't make it to the ground, but the airburst is such that the higher up it occurs the better off we are. I really wonder if hitting it with something like an ICBM mid course interceptor could be used to crack it so it breaks up at a higher altitude. We have to assume late detection, so we would have to repoint the search radars to point upwards and have a very short chain for firing. If we detect a rock moving 30 km a sec at an altitude of 600 km, you only have 20 seconds to get the interceptor on location (not possible). You need detection that gives you some time measured in multiple minutes. An hours notice requires you looking out beyond GSO with very big radars.

Personally I think a multi-pronged approach is needed.

Large object (>100m) dedicated IR search and multi-year mitigation technology.
Small objects (5m - 50m) late detection with giant radars that don't exist and attempt to crack them so they break up higher through the use of an interceptor.
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Offline ChileVerde

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Re: Meteor Strikes Chelyabinsk, Russia
« Reply #382 on: 02/19/2013 02:04 PM »

Quote
http://science.slashdot.org/story/09/06/22/1625254/us-military-blocks-data-on-incoming-meteors
http://blogs.nature.com/news/2009/07/post_30.html
http://www.nature.com/news/2009/090612/full/459897a.html
http://www.space.com/6927-military-seeks-common-ground-scientists-fireball-data-flap.html

Current news about this:

Quote
http://www.space.com/19846-russian-meteor-fallout-military-satellites.html

Russian Meteor Fallout: Military Satellite Data Should Be Shared
by Leonard David, SPACE.com’s Space Insider Columnist
Date: 18 February 2013 Time: 09:03 AM ET

 Piecing together the true nature of the meteor that detonated over Russia would benefit by observations likely gleaned by U.S. military spacecraft.

But for several years, that data has been stamped classified and not made available to the scientific community that study near-Earth objects (NEOs) and any potential hazard to Earth from these celestial interlopers.

In the wake of the Russian meteor explosion, there is a renewed call to make data gathered by both space systems and ground networks speedily available to scientists.

<considerable snip>
"I can’t tell you which asteroid, but there will be one in 2025," Bolden asserted.

Offline R7

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Re: Meteor Strikes Chelyabinsk, Russia
« Reply #383 on: 02/19/2013 02:27 PM »
To shatter 15-meter H-chondtrity body into 1000 pieces - the classic Russian RPG-29 would be quite enough. For a guy like DA14 (50 to 100 m in diameter) - a light American armor-piercing bomb (like what they used at Midway) is sufficient.
NO nukes, all you need is 500 lbs of TNT and Lieutenant Commander McClusky.

Corollary: you don't need explosives at all, just an impactor (hollow point, not AP ;) ). Kg of TNT = ~4.2MJ, kg of anything at 20km/s = 200MJ.
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Offline smoliarm

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Re: Meteor Strikes Chelyabinsk, Russia
« Reply #384 on: 02/19/2013 04:18 PM »
To shatter 15-meter H-chondtrity body into 1000 pieces - the classic Russian RPG-29 would be quite enough. For a guy like DA14 (50 to 100 m in diameter) - a light American armor-piercing bomb (like what they used at Midway) is sufficient.
NO nukes, all you need is 500 lbs of TNT and Lieutenant Commander McClusky.

Corollary: you don't need explosives at all, just an impactor (hollow point, not AP ;) ). Kg of TNT = ~4.2MJ, kg of anything at 20km/s = 200MJ.

Nice idea, especially if most of these 20km/s come from asteroid itself.
BTW, "hollow point" will work with chondrites, they are ~ 85% of all meteorites, but it won't work with iron meteorites - they are about 10%. Here we would need AP, perhaps depleted uranium tip ;)
But the remaining 5% - basaltic achondrites - they are basalts indeed, dense and robust. For them you need HE bunker-buster ammunition.

Offline Robotbeat

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Re: Meteor Strikes Chelyabinsk, Russia
« Reply #385 on: 02/19/2013 04:53 PM »
Or, how about a counter-orbiting impactor, giving a relative velocity of 60km/s, far beyond chemical explosives. Could be accelerated slowly using very high-Isp ion thrusters, then kept in an heliocentric orbit ready to be commanded to intercept. (You'd need several of these so you could intercept within a month of command.)
« Last Edit: 02/19/2013 04:54 PM by Robotbeat »
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Offline Blackstar

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Re: Meteor Strikes Chelyabinsk, Russia
« Reply #386 on: 02/19/2013 05:08 PM »
Or, how about a counter-orbiting impactor, giving a relative velocity of 60km/s, far beyond chemical explosives. Could be accelerated slowly using very high-Isp ion thrusters, then kept in an heliocentric orbit ready to be commanded to intercept. (You'd need several of these so you could intercept within a month of command.)

I know that it's fun to speculate wildly, but there are some sources you could read out there about this. I've worked with the PI on the Deep Impact mission and he said that impacting that comet, which was 100 km wide, at 10 km/s, was very difficult to do. So trying to hit something even smaller at six times the relative velocity might be a little harder.

Offline jgoldader

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Re: Meteor Strikes Chelyabinsk, Russia
« Reply #387 on: 02/19/2013 05:10 PM »
It's unfortunate that Shoemaker-Levy/9 didn't really focus the necessary amount of attention on the danger of impacts.  One would think that 1000-km mushroom clouds would make even Congress pay attention! 

But asteroid-hunting isn't sexy enough.  It has to compete with every other interest group in astronomy for funding.  Frankly, it does us no good at all if NASA's planned WFIRST telescope discovers the secrets of dark energy a week before we go extinct from a modern-day K/T event.

The really scary asteroids are ones which, like 2012 DA14, spend almost all their time interior to Earth's orbit.  These are best found with a space-based telescope that can peer between the orbits of Earth and Venus.  As of now, we have no such telescope.  The B612 Sentinel telescope is on the right track, but it's not cheap; time to prioritize.

Jeff
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Offline JimO

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Re: Meteor Strikes Chelyabinsk, Russia
« Reply #388 on: 02/19/2013 05:16 PM »
I know that it's fun to speculate wildly, but there are some sources you could read out there about this. I've worked with the PI on the Deep Impact mission and he said that impacting that comet, which was 100 km wide, at 10 km/s, was very difficult to do. So trying to hit something even smaller at six times the relative velocity might be a little harder. 

I want to stronlgy underscore Blackstar's skepticism here,  based on a fundamental principle of flight control.

As range to impact decreases, knowledge of 'relative state' improves and uncertainty shrinks.

But with shorter and shorter flight segments to impact, the time for control actions to MOVE the aim point decreases, and so the net result of steering thrusting gets smaller and smaller.

For all control modes I've seen proposed for moving asteroids, in the terminal phase the uncertainty ellipse shrinks so quickly that the steering capability location ellipse no longer overlaps the aim point and there no longer is enough force to push the aim point back inside the location ellipse before fly-past.

I tried to tell Carl Sagan this, that his fear of a madman hijacking an asteroid defense system and deliberately impacting Earth, was a fantasy. A system that is designed to push one large uncertainty ellipse -- the aiM point -- safely OUTSIDE another huge uncertainty ellipse -- the Earth location -- is easy to design and control. The opposite is NOT.

« Last Edit: 02/19/2013 07:55 PM by JimO »

Offline smoliarm

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Re: Meteor Strikes Chelyabinsk, Russia
« Reply #389 on: 02/19/2013 05:42 PM »
I posted this on a different discussion board but some readers here needed to see it, to:
-------

There are some fundamentally wrong assumptions about meteors being used here as the basis for some wild time-wasting speculations.

Mainly this: claiming that the 'trail' was the result of material from the object. Or 'smoke'. Or dust, or condensation.

Actually, although occasionally tinged with combustion products, the main white trail of fireball meteors actually  is ionized atmospheric constituents. Torn-apart oxygen and nitrogen molecules, ionized by the extreme heat of the compressive shock wave

So naturally the trail can wax and wane and vanish purely as a function of the quickly varying speed and area of the entering object.

Nothing better illustrates this than the space shuttle, which left magnificent trails across the night skies of Texas on many entries to Florida landings in the 1980s and 1990s, and of course, sadly, over East Texas on February 1, 2003. With my family, I observed more than half a dozen such overflights with my own eyes.

And it left these trails without losing ANY material, NO chemical or dust or smoke coming off. JUST tearing apart the atmosphere as it passed, leaving a white trail that gradually dissipated over a period of minutes as the atoms rejoined into N2 and O2 molecules.

JUST LIKE over Chelyabinsk.

See a compilation of eyewitness descriptions of such a space shuttle entry, here:
http://www.jamesoberg.com/96mar-sts72_entry.pdf

I hope this helps attain a proper understanding of, and interpretation of, the Chelyabinsk meteor trail and its implications.


Jim, you are not exactly right.
What you say about Space Shuttle trail is 100% true. The same applies to the part of meteorite trail BEFORE the bright glow begins. After that it is a different story.
Main constituents of this type of meteorite are silica, olivine, troilite (FeS), and iron-nickel metal. At plasma temperatures they all are volatile, as volatile as water ice is at 500 °C. This is why it all ends in explosion.
The bright glow marks the beginning of ablation, at this point contrail has some part of true smoke in it, the smoke proportion goes up as meteor goes down :)
Now exciting part, the explosion - iron, nickel, sulfur, and silica vaporized at say 6000 °K and compressed to hell-knows-what-pressure -- expand rapidly. Pressure drops -> temperature drops -> everything condenses to solid -> VACUUM. This creates very peculiar and violent shock wave, and leaves behind a cloud of tiny particles of amorphous iron, nickel, sulfur, and silica. The first three substances are pyrophorus, they react with oxygen on contact releasing even more energy. And that's what they do when the air mixes into this newly formed cloud.
This is what we see on the second photo.
The photographer got lucky - he managed to make a shot right before the main flash (first frame),
and one more, few seconds later - the second frame. On this one you can see red glow, marked with blue arrow. That's exactly it:
2Fe + O2 = 2FeO (plus a lot of heat)
The third frame was made hours later, and the author noted that the upper part of the trail disappeared fairly soon while the lower part stayed for the whole day.

The original photos page:
http://marateaman.livejournal.com/27649.html

Offline AJW

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Re: Meteor Strikes Chelyabinsk, Russia
« Reply #390 on: 02/19/2013 07:21 PM »
It would seem that increased study of transient lunar phenomena would provide great insight into the actual size and regularity of impacts here on Earth.  Ocean strikes can leave little record, and nature can hide a Tunguska event in less than a century. Twenty years after Tanguska, in 1927, locals still did not want to discuss the event because they believed that they had been visited and cursed by an angry god.

http://science.nasa.gov/science-news/science-at-nasa/2008/30jun_tunguska/

The report by Canterbury monks in 1178 is worth reading as it describes a series of a dozen surface explosions on the moon as well as ejecta and is reminiscent of the hits by the fragments of Shoemaker-Levy 9. 

"There was a bright new moon, and as usual in that phase its horns were tilted toward the east; and suddenly the upper horn split in two. From the midpoint of this division a flaming torch sprang up, spewing out, over a considerable distance, fire, hot coals, and sparks. Meanwhile the body of the moon which was below writhed, as it were, in anxiety, and, to put it in the words of those who reported it to me and saw it with their own eyes, the moon throbbed like a wounded snake. Afterwards it resumed its proper state. This phenomenon was repeated a dozen times or more, the flame assuming various twisting shapes at random and then returning to normal. Then after these transformations the moon from horn to horn, that is along its whole length, took on a blackish appearance."

Increased study of TLP can start today and could give us a far more accurate view of the frequency, size, and the actual risks involved.

Offline Robotbeat

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Re: Meteor Strikes Chelyabinsk, Russia
« Reply #391 on: 02/19/2013 07:28 PM »
Or, how about a counter-orbiting impactor, giving a relative velocity of 60km/s, far beyond chemical explosives. Could be accelerated slowly using very high-Isp ion thrusters, then kept in an heliocentric orbit ready to be commanded to intercept. (You'd need several of these so you could intercept within a month of command.)

I know that it's fun to speculate wildly, but there are some sources you could read out there about this. I've worked with the PI on the Deep Impact mission and he said that impacting that comet, which was 100 km wide, at 10 km/s, was very difficult to do. So trying to hit something even smaller at six times the relative velocity might be a little harder.
Indeed, this wouldn't be a near-term capability and it'd be expensive. Sorry for letting the speculation go rampant.

I do want to read the report you linked to, by the way. Thanks for it.
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Offline Robotbeat

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Re: Meteor Strikes Chelyabinsk, Russia
« Reply #392 on: 02/19/2013 07:42 PM »
I know that it's fun to speculate wildly, but there are some sources you could read out there about this. I've worked with the PI on the Deep Impact mission and he said that impacting that comet, which was 100 km wide, at 10 km/s, was very difficult to do. So trying to hit something even smaller at six times the relative velocity might be a little harder. 

I want to stronlgy underscore Blackstar's skepticism here,  based on a fundamental principle of flight control.

As range to impact decreases, knowledge of 'relative state' improves and uncertainty shrinks.

But with shorter and shorter flight segments to impact, the time for control actions to MOVE the aim point decreases, and so the net result of steering thrusting gets smaller and smaller.

For all control modes I've seen proposed for moving asteroids, in the terminal phase the uncertainty ellipse shrinks so quickly that the steering capability location ellipse no longer overlaps the aim point and there no longer is enough force to push the aim point back inside the location ellipse before fly-past.

I tried to tell Carl Sagan this, that his fear of a madman hijacking an asteroid defense system and deliberately impacting Earth, was a fantasy. A system that is designed to push one large uncertainty ellipse -- the air point -- safely OUTSIDE another huge uncertainty ellipse -- the Earth location -- is easy to design and control. The opposite is NOT.


Oh, I certainly believe you. This is a similar problem to anti-ballistic-missile defense except at a greater scale.

But I consider this a slightly less fundamental problem (than the fundamental energy and momentum constraints) since the uncertainty ellipse can be attacked using better remote sensing, reducing divert thrust requirements. I still agree it makes aiming an asteroid /towards/ the Earth (especially a specific part of Earth) more difficult. Given the choice, gravity tractor should be chosen whenever it is viable since it is a more precise method and can direct the asteroid carefully as to avoid any secondary keyholes.

In every single scenario, the situation is improved remarkably with having better remote sensing. Knowing the position, composition, structure, velocity, mass, rotation, etc. of a potentially hazardous object as early as possible and as accurate as possible is incredibly important and knowing much sooner and more accurately can reduce your deflection requirements by orders of magnitude (importantly, if you can deflect the object before it makes a close pass of a large gravity well, you have an enormous lever arm, reducing your divert requirements by perhaps 4 or 5 orders of magnitude). Thus, at LEAST a comparable amount of money should be spent on improving remote sensing and recon as should be spent on any deflection capability.
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Offline JimO

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Re: Meteor Strikes Chelyabinsk, Russia
« Reply #393 on: 02/19/2013 08:00 PM »
Quote from: smoliarm Jim, you are not exactly right. [/quote

Many's the time I have been 'not exactly right', but THIS time, i was plain wrong, as several friends advised me. This feels better.

 Thanks, let's follow this to a better understanding of recovery of particles,m as well as swabs off of clean surfaces. Could somebody shovel up several square yards of snow, melt it down, and expect to find recoverable particulates?

Offline Targeteer

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Re: Meteor Strikes Chelyabinsk, Russia
« Reply #394 on: 02/19/2013 11:43 PM »
NBC nightly news just ran a story detailing why so many Russians have those dash cams.

Video of a tank crossing a highway and a car being hit by a tire from a crashed aircraft were interesting...
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Offline indaco1

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Re: Meteor Strikes Chelyabinsk, Russia
« Reply #395 on: 02/20/2013 01:07 AM »
Just how much would the entry angle have had to change for us to now be marking a dark day in world history? 

I understand that such a meteor will not reach the ground, independent of the entry angle.


I'm not certain the parameters I used, but just to have an idea I used the calculator at http://impact.ese.ic.ac.uk/ImpactEffects/


tetha=7°    burst at 30km
http://impact.ese.ic.ac.uk/cgi-bin/crater.cgi?dist=5&distanceUnits=1&diam=17&diameterUnits=1&pdens=5000&pdens_select=0&vel=17&velocityUnits=1&theta=7&wdepth=&wdepthUnits=1&tdens=2500

tetha=90°  burst at 11.9 km so it still it will not touch the ground.
http://impact.ese.ic.ac.uk/cgi-bin/crater.cgi?dist=5&distanceUnits=1&diam=17&diameterUnits=1&pdens=5000&pdens_select=0&vel=17&velocityUnits=1&theta=90&wdepth=&wdepthUnits=1&tdens=2500

If some parameter of the shock wave was inversely proportional to square of distance (I don't know),  at a distance of 10km it could be about 10 times more than at 30km. I repeat this is a guess, I really don't know if the physics of shock waves works this way.

Furthermore at 90° I suppose energy release will be much more rapid and "explosive", generating a more destructive shock wave regardless the distance.

Not nice a thing like this over a million people city like Chelyabinsk.
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Offline Robotbeat

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Re: Meteor Strikes Chelyabinsk, Russia
« Reply #396 on: 02/20/2013 03:32 AM »
Also, thicker air at 11km would transport the shock wave much better.
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Offline R7

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Re: Meteor Strikes Chelyabinsk, Russia
« Reply #397 on: 02/20/2013 12:35 PM »
Did Deep Impact have some kind of active autonomous terminal guidance or was it done from Earth? Just wondering what could be done to address the targeting problem of specialized asteroid kill vehicle.
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Offline JohnFornaro

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Re: Meteor Strikes Chelyabinsk, Russia
« Reply #398 on: 02/20/2013 02:18 PM »
... There was a nice article in Sky and Telescope about the Tunguska event explaining how they “explode” at altitude and devastate wide area with the shock wave...

So... it was the shock wave which flattened all those trees shown in the few fotos of the impact zone?

Remember that the shock wave from Mount St. Helens flattened a huge forest when it erupted.

As range to impact decreases, knowledge of 'relative state' improves and uncertainty shrinks.

But with shorter and shorter flight segments to impact, the time for control actions to MOVE the aim point decreases, and so the net result of steering thrusting gets smaller and smaller.... yada yada...

Which proves that nobody "allowed" this event to happen.  But one thing that is clear is that any protection system hinges upon accurate knowledge of asteroid trajectories.

If it is thought that a tiny "gravity tractor" can displace an orbit, then it must be acknowledged that each asteroid out there is a gravity tractor itself. Each individual orbit is subject to so many perturbrations that it seems virtually impossible to make accurate predictions, particularly which city would be hit at which angle.

Since it takes one "unknown unknown" to fly in at some random orbit, the best laid plans of mice and asteroid predictors are hard to state with any certainty.  One prediction that one will hit NYC at 9:00 AM on Thursday, prompting a timely evacuation, will doom any further hunting, should the prediction prove to be false.

The report by Canterbury monks in 1178 is worth reading as it describes a series of a dozen surface explosions on the moon as well as ejecta and is reminiscent of the hits by the fragments of Shoemaker-Levy 9.

Fascinating report.  Is it now known where this hit took place?  Would it have left a visible "new" scar?  Somebody ask Paul Spudis.
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Offline Robotbeat

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Re: Meteor Strikes Chelyabinsk, Russia
« Reply #399 on: 02/20/2013 02:20 PM »
...

If it is thought that a tiny "gravity tractor" can displace an orbit, then it must be acknowledged that each asteroid out there is a gravity tractor itself. ...
Inverse square law.
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