The mechanical engineering behind fireworks
June 29, 2026
Fireworks will light up the sky this Fourth of July and the city will be aglow with the products of mechanical engineering.
Many people’s experience with fireworks will never go beyond lighting a fuse and staring in awe as it explodes high above them, but behind every jaw-dropping display is engineering and chemistry, with mechanical engineering contributing to areas such as propulsion, packaging, combustion, and flight stability.
“You’ve got to understand mechanical engineering is very broad. It’s one of the broadest of the engineering disciplines. When people think about mechanical engineering, their minds often go to gears and mechanisms. But underneath mechanical, there are many overlaps and subdisciplines. Aerospace engineering, for instance, has a huge overlap with mechanical engineering. It’s almost like a subdiscipline,” said Dr. Jeff Marchetta, professor and undergraduate coordinator at the Herff College of Engineering’s Department of Mechanical Engineering.
Marchetta teaches courses such as thermodynamics and aerospace propulsion at the University of Memphis. But, in layman’s terms, he’s an expert in making things go boom.
“To start off with something that I think people are familiar with, I like to think about a rocket. You know what makes a rocket go? It involves a chemical reaction, which we call combustion. You have a fuel. You have oxygen and you get a controlled combustion process that produces high-pressure gases for thrust,” Marchetta said.
The engineering principles behind modern fireworks can be traced back to ancient China, where alchemists first created black powder by combining potassium nitrate, sulfur, and charcoal between the seventh and ninth centuries.
“Carbon is really the thing that is the fuel, just like when I burn wood in a fireplace, what’s really burning there is the carbon in the wood,” Marchetta said. “And then the potassium nitrate, which has oxygen. What ingredients do I need to create a fire? I need fuel and I need oxygen. And then the last part is sulfur. What it does is it’s actually also a fuel, so you can react it with oxygen as well and it will release energy, but its primary purpose in the black powder formula is to lower the ignition temperature and improve the combustion characteristics of black powder.”
For traditional firecrackers, that’s about as far in the process as you need to go. But to make the firework fly high into the sky, you need to direct the high pressure gases produced from the chemical reaction, downward through a nozzle, producing upward thrust.". Once fireworks leave the ground, a time-delay fuse, ignited during launch, burns while the shell ascends before igniting the burst charge. A longer fuse means fireworks take longer to explode and have a chance to fly higher before they do.
“If it has an ending where it’s going to go ‘Pop,’ that’s got to be a second reaction,” Marchetta said. “The fuse itself has properties so that you can light one end of it and the fuse shortens and shortens and shortens as it burns until it gets to the charge, to the black powder.”
Of course, there has to a container, or shell, to carry the fuse and chemical reaction to the point of explosion. It could be made out of thin paper; even cardboard would do. It just needs to be strong enough to survive the initial propulsion. Shells are designed to burst symmetrically. Directional effects come from star placement, burst design, spin, angled launch, or specialized effects.
But a great fireworks display is nothing without the pretty colors. For that, we need certain elements.
“It turns out when we apply heat to different elements, like sodium or calcium, they emit different colors,” Marchetta said. “Anybody who ever took high school chemistry probably did a flame test where they took copper wire and put it over a Bunsen burner. You could see that it would produce a greenish-blue flame. When you get into the chemistry of it, it basically deals with the excitation of electrons. So, these elements, which are packaged as metal salts, when they’re heated, give off light in different colors and in different wavelengths.”
When you understand the mechanical engineering behind fireworks, it sounds simple enough. But Marchetta emphasized that, even if you have a background in combustion, it’s better to leave the light show to the professionals.
“There’s a lot of danger involved because these explosives are very energetic,” Marchetta said. “You can have a lot of physical injuries if they’re not handled properly and one ignites. As I mentioned, adding sulfur lowers the ignition point. That means that it doesn’t take as much heat to cause these things to go, ‘Boom!’ So, there are hazards that come along with working with fireworks. You have to be careful because people can get seriously injured dealing with explosives.”
So, enjoy a professional fireworks show this Fourth of July, but keep in mind the engineering that made the dazzling display possible.