Some 1,400 years after their invention in ancient China, fireworks continue to evolve. As the nation approaches Independence Day, rocket scientist Dan Erwin, chair of astronautical engineering at the USC Viterbi School of Engineering, gives his take to USC’s Diane Krieger on the technology behind pyrotechnics.
The biggest change: computers
When we were kids, you would see a bunch of guys running around setting off fuses during a fireworks show. You don’t see that anymore. You see a guy sitting at a computer. Fireworks don’t have fuses anymore. They are fired with electronic matches, which means they can be under the accurate timing control of a computer.
An electronic match, or e-match, is a piece of incendiary material that burns very hot, attached to an electrical wire. When enough current is passed through the wire, it heats and ignites the incendiary material, which then ignites anything around it. Our rocket lab uses e-matches to fire rockets.
Dress rehearsals for fireworks shows
Now you can simulate in advance what the whole fireworks show is going to look like. The same software used to set up group firings of the fireworks shells can be used to create a simulation. It’s pretty easy in computer graphics to simulate the traces of a bunch of glowing particles. If you have a whole assembly of them, generating a simulated movie is as simple as taking a movie of a single firework and superimposing a whole bunch of them at the right time and locations.
Fireworks of the future
I think there’s a lot more room for discovery. As the price of extremely small electronic sensor packages comes down, it would be possible to put individual location sensors on pieces of fireworks. The same kinds of advances that are leading to tiny simulated insects could lead to intelligent swarms of pieces of fireworks with collective sustained behaviors.
You hear a lot about large unmanned vehicles that do strikes in Afghanistan. On the other extreme, scientists are coming up with bird-sized or even insect-sized flying vehicles. It would be a lot of work and very expensive, but there is no reason you couldn’t use them as components of fireworks.
The intersection between rockets and fireworks
They have a fair amount of underlying knowledge in common, but the requirements for a rocket engine are a little different than the requirements for fireworks. Rocket fuel burns too fast and too hot. It wouldn’t glow, and any glow it had would be white. All the color would wash away. You want the firework to burn slower and cooler.
Fireworks come in two main varieties: firecrackers, prized for their boom, and sparklers, prized for their brilliance.
Firecrackers are made by packing either black powder (gunpowder) or flash powder in a tight paper tube, which is then lit with a fuse.
Sparklers are made by coating wire with a mixture of a fuel (such as black powder), an oxidizer (such as potassium nitrate), iron or steel powder and a binder (such as sugar or starch).
Fireworks also frequently contain aluminum, iron, steel, zinc or magnesium dust to create sparks. The metal flakes heat to incandescence; at a high enough temperature, they burn. Chemicals such as calcium, sodium, barium, lithium and potassium can be added to produce certain colors.
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