“Detonation engines use very fast combustion,” said Jiro Kasahara, professor at Nagoya University. “The combustion wave travels around in a circle, at supersonic speeds. If rocket engines used this technology, they could be made smaller, simpler, and more efficient.”

While RDEs have been theorized for decades, characterizing them in the real world has been challenging. The speed of an RDE combustion wave is about 2 kilometers per second – about Mach 6, or 4400 miles per hour – rotating in about a six-inch diameter circle. “Until recently, that was too fast to visualize,” said Kasahara. “But now we have high-speed video cameras, and high-resolution computational fluid dynamics, and we can now analyze these waves.”

That’s what brought Kasahara and his team to Purdue University. “Many researchers around the world are working on different aspects of RDEs,” said Terry Meyer, professor of mechanical engineering. “Professor Kasahara’s focus is on space-based propulsion; others are focused on energy generation. My team’s focus is on detailed measurement, characterization, and visualization.”

Both Kasahara and Meyer can lay claim to milestones in RDE development. In July 2021, Kasahara’s team launched an RDE engine on top of a sounding rocket. At 160 kilometers above the earth, they successfully fired the engine for six seconds. It was the first RDE engine ever ignited in space.

In July 2021, Jiro Kasahara's team became the first to successfully ignite an RDE engine in space. Kasahara was eager to bring his engine to Purdue to characterize its combustion waves. (Photo courtesy Nagoya University/JAXA)

Purdue hosts the largest academic propulsion lab in the world, Zucrow Labs. Their facilities include test cells with laser imaging systems, allowing researchers to see RDE combustion waves like never before. “We use laser-induced fluorescence, which allows us to see combustion waves at more than a million frames per second,” said Meyer. “This is about twenty times faster than anyone else has demonstrated.”

That’s why Kasahara was so eager to bring his engine to Purdue to characterize its combustion. “They have state-of-the-art optical research technology,” said Kasahara. “Their campus is huge, and they have very nice propulsion laboratory setups. It’s just fantastic here.”

In addition to Kasahara and three of his students, Purdue collaborators included Guillermo Paniagua, professor of mechanical engineering; James Braun, research assistant professor; and Venkat Athmanathan, research scientist at Zucrow Labs.

“We have a long collaboration with Professor Paniagua and Professor Meyer,” said Kasahara. “When we get together, it’s really fantastic. If we were all working separately, it would take 20 years to develop these technologies. But through collaboration, we can merge our efforts and make it happen much faster.”

As far as the end goal of RDE research, Kasahara is aiming high. “It’s my object – and I think Professor Paniagua and Professor Meyer also – to completely change aerospace technology,” he said. “RDEs are a game changer, and that’s really our final target. Collaborating with Purdue University makes it possible.”

Nagoya University's rotating detonation engine (RDE) sits on a test rig at Purdue University's Zucrow Labs. The collaborators include (left to right) Venkat Athmanathan, James Braun, Guillermo Paniagua, Jiro Kasahara, and Terry Meyer.

Writer: Jared Pike, jaredpike@purdue.edu, 765-496-0374

Sources: Terry Meyer, trmeyer@purdue.edu

Guillermo Paniagua, gpaniagua@purdue.edu

Jiro Kasahara, kasahara@nuae.nagoya-u.ac.jp

James Braun, braun26@purdue.edu

Venkat Athmanathan, vathmana@purdue.edu