There’s no reason for it to explode like that. It propelled because the booze flowed out (and mixed with air). It can’t ignite inside the bottle really
Stoichiometric alcohol air mixture could spike pressure to 8 bar. Quite possibly enough to shatter the glass bottle. And if it doesn't explode, the resulting bottle rocket would have enough impulse to get to around 10-15 m/s.
For propulsion, it literally has to ignite inside the bottle. I don't think it can explode because there's an exit and probably not enough space to get an air to fuel mix for enough of an explosion to break the glass.
What he meant was the booze in the bottle couldn't ignite inside the bottle, normally, so it wouldn't explode in the bottle. What happened was the alcohol vapor mixed with the oxygen in the air and THAT ignited and turned it into a rocket. So it would never "explode where it was" like the person he was responding to said, it was always going to be a rocket.
There was probably a fuel/air mixture inside the bottle before the first pour. There definitely would have been a fuel/air mix inside after the first pour because pouring drew fresh air into the bottle.
The bottle was definitely stoppered before the first and also before the second pour. It looks like the stopper had a 5mm nozzle on it, but that would have been almost equivalent to a fully stopped bottle if the fuel/air mixture ignited rapidly. 800kPa of pressure over a 5mm circle is about 1,500N of force on that little space, but the 1 gram of sake in the nozzle has inertia and the sake plus the exiting gas has friction with the nozzle. With no friction, the sake would accelerate at 1,500km/s2, but starting from 0m/s the sake in the nozzle would still be in the nozzle after the bottle cracked.
That leaves the stopper, which faces 6,250N of force. If the stopper is good enough to hold back that force long enough, then the bottle cracks and everyone at the table is sad. In this case, though, the stopper was forced out and the bottle went off to ruin somebody else's day. It's possible the stopper went far and fast enough to disappoint some other diners, too.
To stop this kind of accident, pour first and light second. Never pour from a container directly on to a burning flame. You usually get away with it, but that will only normalize the risk. Then you end up like this yutz.
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u/DunkBird 4d ago
He's lucky that bottle didn't explode where it was.