Researchers at the University of Central Florida say they have developed an advanced rocket propulsion system once thought to be impossible. Known as a rotating detonation rocket engine, it will allow upper stage rockets for space missions to become lighter, travel farther, and burn more cleanly. The research was published recently in the journal Combustion and Flame.
“The study presents, for the first time, experimental evidence of a safe and functioning hydrogen and oxygen propellant detonation in a rotating detonation rocket engine,” said Kareem Ahmed, an assistant professor in the Department of Mechanical and Aerospace Engineering at UCF who led the research.
The rotating detonations are continuous Mach 5 (five times the speed of sound) explosions that rotate around the inside of a rocket engine made of copper and brass. The explosions are sustained by feeding hydrogen and oxygen propellant into the system at just the right amounts, according to UCF Today.
The system improves rocket engine efficiency so that more power is generated using less fuel than traditional rocket engines. Less fuel means less weight. Less weight means higher payloads or longer range, all with reduced emissions.
While the concept of rotating detonation rocket engines has been around for more than 50 years, the researchers are the first to show the technology can work outside the lab. Their breakthrough is the result of carefully balancing the rate at which hydrogen and oxygen are released into the engine.
“We have to tune the sizes of the jets releasing the propellants to enhance the mixing for a local hydrogen-oxygen mixture,” Ahmed says. “So, when the rotating explosion comes by for this fresh mixture, it’s still sustained. Because if you have your composition mixture slightly off, it will tend to deflagrate, or burn slowly instead of detonating.”
To verify their findings, the team injected a tracer into the hydrogen fuel flow and captured the detonation waves using a high-speed camera. “You need the tracer to actually see that explosion that is happening inside and track its motion,” Ahmed says. “Developing this method to characterize the detonation wave dynamics is another contribution of this article.”
William Hargus, lead of the Air Force Research Laboratory’s Rotating Detonation Rocket Engine Program, is a co-author of the study and began working with Ahmed on the project last summer. “As an advanced propulsion spectroscopist, I recognized some of the unique challenges in the observation of hydrogen-detonation structures. After consulting with Professor Ahmed, we were able to formulate a slightly modified experimental apparatus that significantly increased the relevant signal strength,” he says.
“These research results already are having repercussions across the international research community. Several projects are now re-examining hydrogen detonation combustion within rotating detonation rocket engines because of these results. I am very proud to be associated with this high-quality research,” Hargus added.
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