Tunguska blast simulation by Sandia lab

3D simulation of a 5 megaton explosion that is initiated (asteroid breaking up due to aerodynamic stress and becoming a super-hot fireball) 12 km above the surface, for an asteroid entering at an angle of 35 degrees above the horizontal. Box dimensions are 40 km wide, 20 km high. Colors indicate speed. The hot fireball does not reach the surface, but descends to an altitude of 5 km before buoyantly rising.
At ground zero, the blast wave comes from directly above, consistent with observations of standing trees at the Tunguska epicenter. Moving away from ground zero, the outward component of blast wind speed quickly picks up and levels all trees radially from zero point. Note how the direct and reflected shockwaves reinforce near the ground (brighter area at the lower left indicating shock strengthening). This phenomenon is known as the Mach stem and further adds to the destruction caused by an airburst.

Category:

Science & Technology

Tags:

• tunguska
• asteroid
• blast
• sandia
• simulation
• supercomputer

[2Nyce4dagame]

umm whats that bubble at the bottom

[ugowar]

@2Nyce4dagame Shockwave being reflected off the ground. That's what leveled all the trees away from ground zero except for a small region directly below.

[FatalFist]

@ugowar There's still downforce from the wave though. It wouldn't happen. It'd have crushed the trees in the center down.

[ugowar]

@FatalFist Correct, that's why the trees near ground zero have their branches ripped off, but the main stem (which stands vertical) remains standing. Notice I said the trees far from GZ were leveled, I didn't say the ones near were left *intact*.

Farther out, the direct and reflected shockwaves form the so-called Mach stem that sweeps basically radially outward so nothing is left standing.

[hyperthreaded]

Was that in real time?

[ugowar]

I can't say, the first segment definitely looks speeded up to me, the second part where I slowed it down to 1/2 simulation speed looks like it might be closer to real time, judging by how fast the shockwave moves. It still looks a bit too fast, though.

[stanisbell]

Would this, or another asteroid like it, cause an EMP you reckon? Read NYT bestseller, "One Second After" for the possible after effects of an EMP generated by a nuke detonated above the atmosphere over a major metropolis. Interesting.

[albedoshader]

@ugowar: I think the speed of the animation is constant. The air density rises exponentially the nearer the asteroid is to the ground, so the breakup dissipates a lot of kinetic energy very fast.

[ActiveStorage]

what material did u use for the simulation? and what's the scale of it? would be better if there was actual gradation in kilometers or miles around the image. That way it becomes clear when and where the heating starts and how far the shock wave spreads etc.

[joshig1983]

That's surprising. I didn't hear of this event before. The wikipedia article on it has some interesting first hand reports from people that were nearby. That's really amazing and a bit scary.