Firecracker Physics: Exploding Directionality

[wil3]

Hello, this question may not be appropriate for this forum, but I feel that chemistry people are more likely to understand the basic operational characteristics of firecrackers.

Say I have a standard obnoxious firecracker, like the ones that they sell connected in strings for your neighbors to detonate early in the morning. The firecracker is just a bunch of black powder in a cardboard tube, and the tube explodes when the fire reaches it.

My question is how the tube explodes. Is the explosion somewhat omnidirectional, or does it favor the poles of the cardboard tube? By that I mean, if I were trying to pry open a door or something (not that I am, this is just to illustrate), would more force be directed onto the two surfaces if the firecracker was inserted lengthwise or on its end?

 

[Antiphon]

Lengthwise.

Look up shaped charges. Firecrackers aren't that sophisticated but it's still interesting.

Don't try to make one. You get a horrible injury to yourself or someone else. It's not fun.

 

[wil3]

I assure you that I'm not planning on it :P

So by lengthwise you mean with its ends touching the two surfaces? As in, more explosive force comes out of the poles of the cylinder? That makes sense to me, because that's the way the expanding gases are more likely to go, but I thought I should check. Thank you very much.

 

[ChemHopeful]

if you look up at a blown up firecracker (the "blackjack"/on a string type) you will find they split at the middle, leaving the two ends more or less intact

so i don't think you would get more mileage out of one by directing one of its poles at your target

 

[LudusRex]

I would approach this question by first considering the basic principles of explosive materials and their behavior. Explosions are the result of a rapid release of energy, typically from a chemical reaction, which creates a shock wave that propagates outward from the source. In the case of firecrackers, the black powder inside the cardboard tube undergoes a rapid combustion reaction, releasing a large amount of energy in a short period of time.

Based on this understanding, it is likely that the explosion from a firecracker is somewhat omnidirectional, meaning that the force is distributed relatively evenly in all directions. This is because the shock wave from the explosion will travel outward from the source in all directions, rather than being focused on specific areas.

However, there may be some variation in the directionality of the explosion depending on the specific design of the firecracker and the materials used. For example, if the black powder is packed more tightly in one end of the tube, the explosion may be stronger in that direction. Similarly, if the tube is not completely symmetrical, the explosion may be slightly biased towards one side.

In terms of the impact on surfaces, it is likely that the force of the explosion will be greater when the firecracker is inserted lengthwise, as this allows for more surface area to be impacted by the shock wave. However, the difference may not be significant enough to make a noticeable difference in prying open a door.

Overall, the directionality of a firecracker explosion is likely to be somewhat omnidirectional, but there may be some variation depending on the specific design and materials used. It is important to handle all explosive materials with caution and follow proper safety precautions to avoid injury.