http://science.slashdot.org/story/09/06/22/1625254/us-military-blocks-data-on-incoming-meteorshttp://blogs.nature.com/news/2009/07/post_30.htmlhttp://www.nature.com/news/2009/090612/full/459897a.htmlhttp://www.space.com/6927-military-seeks-common-ground-scientists-fireball-data-flap.html
http://www.space.com/19846-russian-meteor-fallout-military-satellites.htmlRussian Meteor Fallout: Military Satellite Data Should Be Sharedby Leonard David, SPACE.com’s Space Insider ColumnistDate: 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>
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.
Quote from: smoliarm on 02/19/2013 11:13 amTo 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.
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.
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 waveSo 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.pdfI hope this helps attain a proper understanding of, and interpretation of, the Chelyabinsk meteor trail and its implications.
Quote from: Robotbeat on 02/19/2013 04:53 pmOr, 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.
Quote from: Blackstar on 02/19/2013 05:08 pmI 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.
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?
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.
... 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...
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...
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.
...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. ...