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 experiences 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 someone practicing mechanical engineering, whether they know it or not.
“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 heat energy. Essentially, you get a little explosion,” Marchetta said.
By that logic, the Chinese may have produced some of the world’s earliest mechanical engineers when, between 600 and 900 AD, alchemists mixed potassium nitrate, sulfur and charcoal, creating black powder.
“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, 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.”
For your basic firecrackers like M80s, 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 that chemical reaction, or propulsion, downward. Once fireworks leave the ground, another time-delayed reaction starts. Most of us know that time-delayed reaction as a fuse. 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 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. The container’s importance comes in packaging those explosive chemicals together, directing the initial chemical reaction downward and in creating the final display. If, for instance, you want the firework to explode to the right, you would make the left side of the container weaker.
“One of the things I can control is the shape of the container or the shape of the nozzle that is doing the propulsion,” Marchetta said. “That’s one of the mechanical aspects of it. How do I change the direction of the star, for example? Well, I just make a particular shape so that I direct the flow in a particular way, which creates rotation.”
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 beryllium 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, 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.