Long Beach

Fuel Rewards: Exploring Properties of Solid Rocket Propellants




For Dr. Joseph Kalman and his students, the pursuit of knowledge is a mission to better understand energetic materials—the hot-burning stuff of solid rocket propellants, explosives and pyrotechnics. 

Dr. Kalman, an assistant professor of mechanical and aerospace engineering at Cal State Long Beach, is leading the establishment of an on-campus Solid Propulsion and Combustion (SPC) Laboratory. There, he and other researchers study the physical and chemical properties of solid propellants—or to put things more simply—what happens inside the rocket motor during the moments after ignition. 

Kalman comes from the Naval Air Warfare Center Weapons Division at China Lake in California’s Mojave Desert. His current appointment allows him to introduce students to the world of propulsion engineering. 

The SPC lab enables researchers to take a close look at what happens at the micro-level when energetic materials ignite, blazing to temperatures that he said can approach 3,000 degrees Kelvin, which is close to 5,000 degrees Fahrenheit. 

The Office of Naval Research provided a grant of nearly $400,000 to help the lab acquire equipment, so Kalman has the lab fully equipped with such features as: 

  • CO2 laser, a device that also is used to cut or weld metal, for controlled ignitions. 

  • Resonant acoustic mixer, an increasingly popular device in the propellants industry that uses sound to mix thick, batter-like propellant ingredients use. 

  • ​High-speed camera and optical devices to record, at minute resolutions and very high speeds, which help researchers understand how propellants react in a flame front and flame combustion process. 

“It is crucial to have this lab on campus,” Kalman said. “If it is not on campus, our aerospace engineering students, and others, will not benefit from this equipment. We are in a hotbed of the aerospace and propulsion industry, and having students exposed to this work and equipment, with hands-on experiences, will give them a leg up from their peers at other schools.” 

Alumnus Alek Nilsen, along with graduate student Christian Rodriguez and others, has worked with Kalman designing a slab burner to study how hot air interacts with solid fuel. Students are excited about the lab’s research possibilities. 

One of their objectives is to better understand the functioning of a ramjet, a variant of an airbreathing jet engine.  ​​This kind of propulsion system allows a flying missile to channel surrounding environmental air into a combustion chamber. Missiles incorporating ramjets can have greater thrust and, thus, longer ranges than their more traditional counterparts, Kalman said. 

The typical method of producing solid rocket propellants is similar to baking a cake, he noted. Here, however, the main ingredients are an oxidizer (needed to begin/sustain combustion), metal particles (for energy density) and a rubbery polymer binding agent that holds everything together. The ingredients are mixed together and molded into the shape of a rocket engine. 

That’s a basic description of the process, but part of the mission for the new laboratory is to explore the potential for more sophisticated fuel or propellant geometries. David Ramirez, an undergraduate student, is researching the science of 3D-printed rocket propellants at the lab. 

A missile powered by 3D-printed solid propellant, for example, could be designed to accelerate rapidly after being fired before slowing to a cruising speed and accelerating again before striking its target, Kalman said.

If such a fuel is employed to power a rocket with a human passenger, the propellant could be designed to slow to a more comfortable rate of acceleration after escaping the earth’s gravity, Nilsen said. ​​