Wednesday, November 02, 2016

A Ballistic Fart

A marksman shoots a Magnum .44 into a block of ballistic gel. In a slow-motion replay, you can see the aftereffects, in which the block has a case of gas, then fiery indigestion, and then farts, through its newly-created "digestive canal." There's a perfectly normal explanation for this. 
Slow motion video capture is a natural companion to just about anything that you’d need ballistic gel for, and good thing — because the video captured what appears to be a diesel effect! The block is hit with a bullet, and as the bullet rapidly expands and dumps its energy into the gel, a cavity expands rapidly. During this process, some of the (oil-based) material in the cavity has been vaporized. After the expanded bullet exits (to the right of the gif above but easier to see in the video below), the cavity in the block begins to collapse. The resulting pressure increase appears to ignite the vaporized material, which explodes with a flash followed by some exhaust.
Read more about the effect and see the original video at Hackaday. (via reddit)


Barbwire said...

There was an article in the paper today about a woman who farted during laser surgery ton her cervix. The laser ignited the gas from the fart and severely burned the woman.

Art S said...

The bubble isn't expanding gas but a vacuum caused by the energy transfer. There is no pressure to rise as it shrinks and no oxygen present to sustain combustion. Sometimes a collapsing cavitation can give off a lot of energy even without a secondary diesel effect. Even water can flash when a cavitation collapses.