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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><div><div><div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Such a grim topic it is, that huge explosion in Beirut.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>When I was in engineering school, we had a compressible flow class where they had us do all these calculations on blast radius, overpressure threshold, shock wave mechanics and so forth. The cold war was still going in those days, so they thought it was a good thing for us to know about.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>My compressible-flow book went into a lotta gory detail on what happens behind a shock wave and how to figure out what it was that exploded based on the velocity of the shock wave (which isn’t the same as a leading-edge sound wave (because the shock wave travels in a compressed medium and sound waves do not (so the shock wave gets to ya first (and hurts a lot worse.))))<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>If we go with a cell-phone frame rate of about 30 per second, and estimate the shock wave was advancing at about 100 meters between frames, that is a shock wave velocity indicating ammonium nitrate, which supports the theory that it was a coupla thousand tons of fertilizer on a parked ship, possibly three thousand tons. Oy vey mercy.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>spike<o:p></o:p></p></div></div></div></div></body></html>