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or even practicing physicists? specializing in explosive/collision physics or hyper-velocity energy exchanges?

question: This is a personal interest question and has nothing to do with gaining access to BASE jumping sites in central Colorado. promise.


In a hyper-velocity collision of 10km/sec or more, IE the recent accidental satellite collision over Siberia, what form does resulting material (assuming mostly metal) take if the collision was a 100% cross section collision?

I have heard theories that there was no momentum exchange, but I do not buy it. some have claimed that the conducting material would become plasma before the inertial energy could be conducted. but that does not make sense as the energy needed to turn material to plasma is insane.

I understand that the propagated forces travel through an object at its 'speed of sound', and even with hardened alloys it is well below 15km/sec. so, because these objects collided with relative velocity of ~12km/sec, what would the resulting debris be?

If they had Velcro, they would just stick to each other and drop straight down to Earth.

I don't know how debris would look like, but in my high school years, I made up a problem for a physics report which was very similar: two satellites collide on orbit and perfectly cancel their momentum. The resulting explosion is perfectly symmetrical, all debris move at the same speed (lower than escape speed). What would happen next?

This problem has an interesting solution. Because all debris initially have exactly the same total energy (their potential energy is the same since they're at the same point in gravity field, and kinetic energy is the same as their speed is the same), and because the length of the semi-major axis is determined only by total energy (see, for example, this), and the orbital period is determined only by the length of semi-major axis, it follows that all debris will have exactly the same orbital period. Say, 2 hours.

So, 2 hours after the explosion, the debris will come back from all directions simultaneously (except for those that fell to Earth, there will be kind of a "black hole" on one side), and produce an IMPLOSION of equal strength, which will then explode again. Kind of a "miniature" Big Bang, repeating itself over and over again...

Beautiful, eh?

another simpler less word problem question that made me think of this satellite question;


'sound' [being physical waves cycling or singular through a media] travels at the 'speed of sound', right? and this speed is different for every different form of media that can support physical waves. simple examples being water and air, through air about 330m/sec, through seawater about 1500m/sec. these wave speeds are dependent on density.

my question is, in an explosion, (IE something similar to an underwater nuclear explosion like BAKER tests) does the increasing density of the water increase the speed of sound? it MUST in that area with the compressed mass/increased density, but does that effect the wound speed relative to an outside observer in the blast front?

i know this is weird. but i have been reading a ton of old US gov PDF files on nukes instead of doing school, and I was just wondering if anyone could explain that to me.

I suspect you're looking for an engineer rather than a physicist, and at any rate I'm a quantum guy. But I'll offer up that in high-velocity impacts here on earth (say, in the kinetic-energy weapons that are being developed), my understanding is that the projectile is vaporized on impact (and, presumably, some of the target).

The speed of sound is really only appropriate to the regime in which the motion is linear (ie, displacements are small or at least gradual), which clearly isn't the case here. Once you get atoms really close together, they're considerably less hesitant to transmit energy at closer to the speed of light.

In the event of a head-on collision between two solid metal spheres in space, I'd expect a two-lobed (8-shaped) plume of largely-vaporized metal. On the other hand, the folks studying the growing problem of very small space junk seem to believe that in real collisions, lots of smaller space junk (rather than vapour) is produced.