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  • A fully contained explosion

    Just wondering if this has been done, and what the results were. I'm imagining a sphere of some size, with only a small cavity at the center of it. Explosive is contained in this cavity, and the sphere does not yield when the explosive is set off. What happens?
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    It depends on how big the container is and what it's filled with. A fire cracker in an aluminum milk box (lined with styrofoam) with my little brother on top to seal it. There was noise but no visible movement of the box lid and he did not (as we wished) achieve low earth orbit either.

    There was enough space for the gasses to dissipate the heat and shrink back down without harming the box.

    Dan
    At the end of the project, there is a profound difference between spare parts and left over parts.

    Location: SF East Bay.

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    • #3
      Originally posted by darryl View Post
      Just wondering if this has been done, and what the results were. I'm imagining a sphere of some size, with only a small cavity at the center of it. Explosive is contained in this cavity, and the sphere does not yield when the explosive is set off. What happens?
      The energy of the explosion is dissipated as heat.

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      • #4
        Depends on what kind of energetic materials we are talking about. For high velocity HE-s I can not really fathom a known container material that shall not yield to some degree once it goes off. But in theory if nothing yields then the gaseous reaction products (CO, CO2, H2, N2, etc.) shall remain in the closed cavity under pressure and excess energy is released as heat and to a small degree as sound through the container material.

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        • #5
          I mean, isnt that just what an air compressor tank already does? Yeah, yeah, theres no explosion, but it contains the pressurized byproducts. Given that an explosion is just what happens when something is rapidly converted to higher volume of something else, if the container didnt yield youd just be left with a container full of higher pressure, and probably a bit hotter.

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          • #6
            https://www.youtube.com/watch?v=u9_bqafUJfA

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            • #7
              You say that the sphere doesn't yield, which is fine. You'd probably hear the explosion as the sphere would no doubt transmit the shock wave.

              Inside, the cavity would experience high temperature and high pressure. The heat would dissipate into the sphere and pressure would drop. You'd end up with a warmer sphere than you started with and only slightly more pressure in the cavity (resulting from the final temperature difference). The final temperature could be calculated from the energy released by the explosion, the specific heat capacity and mass of the sphere and any heat lost from the surface of the sphere to the atmosphere.

              Ian
              All of the gear, no idea...

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              • #8
                I seem to recall that propellants and explosives are characterized using a device that does exactly what you are visualizing. It's a closed and sealed container that has a very small amount of the material to be tested sealed in it. The stuff is detonated and the rise in temperature and pressure is measured and used to calculate the energy released and the speed at which the release happens.

                Google "closed bomb test" for more authoritative reading.

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                • #9
                  This happens in an internal combustion engine millions of times. You will get heat and pressure along with sound.
                  www.thecogwheel.net

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                  • #10
                    The phrase which was used here for devices to do such testing was " Bomb Calorimeter" If I remember correctly they were heavily built Stainless steel containers with temperature and pressure sensors in which very small amounts of material to be tested were burnt or exploded. It is so long ago that details are foggy. Regards David Powell.

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                    • #11
                      Originally posted by enginuity View Post
                      This happens in an internal combustion engine millions of times. You will get heat and pressure along with sound.
                      Ha ! This is what I first thought of.
                      Basic physical sciences question.
                      Not sure why the mystery.

                      -D
                      DZER

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                      • #12
                        It's been done with nuclear detonations - Project Salmon and Project Sterling

                        https://www.youtube.com/watch?v=7Ib9fo3Ne8k

                        http://mshistorynow.mdah.state.ms.us...in-mississippi
                        Last edited by wierdscience; 03-12-2020, 09:52 AM.
                        I just need one more tool,just one!

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                        • #13
                          https://www.energy.gov/nnsa/articles...labs-contained

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                          • #14
                            Originally posted by Doozer View Post

                            Ha ! This is what I first thought of.
                            Basic physical sciences question.
                            Not sure why the mystery.

                            -D
                            Because what normally happens in an IC engine not an explosion.
                            When it does happen is when you experience pinging or "pinking" and hole a piston.
                            Engines function with a propagated wave front.
                            Len

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                            • #15
                              Originally posted by enginuity View Post
                              This happens in an internal combustion engine millions of times. You will get heat and pressure along with sound.
                              What happens in an internal combustion engine is actually a controlled burn, or what could be referred to as deflagration. When the fuel explodes uncontrollably it is referred to as detonation and is a very harmful phenomena.
                              An internal combustion engine can experience flame front propagation speeds anywhere from several meters per second all the way to several thousand feet per second, at which point the flame front propagation speed is clearly in the detonation spectrum. Normally it would be in the hundreds of feet per second category depending on a multitude of factors that are beyond the scope of a short post here.

                              As an example of a very fast burn(explosion, detonation), I remember once reading that det cord burns at the rate of about 10,000 meters per second, or about 32,000 fps!

                              This point however does beg the question, at what point does a fast burn become an explosion?
                              This is science after all and should not be subjective. Inquiring minds want to know.
                              Home, down in the valley behind the Red Angus
                              Bad Decisions Make Good Stories​

                              Location: British Columbia

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