A rotating detonation engine is a kind of propulsion system that has been theorized about and researched for years, but this design only existed on paper and in prototypes. This year, a team of engineers at RTX built and tested one at scale. This propulsion system is unique because it requires no moving parts, and is lighter and more powerful than traditional engines. This test was a major victory for the RTX team, and they achieved it, in part, thanks to the use of additive manufacturing and other advanced technologies.
Rotating detonation engines have an enclosed, ring-shaped chamber where combustion occurs. When in flight, fast-moving air is drawn into the chamber, and a precise mixture of fuel is injected. This injection ignites a flame-like detonation wave that moves around the ring for as long as fuel is injected. This energy is then converted into thrust, which propels the vehicle forward.
Rotating detonation engines are lighter and more powerful than traditional engines.
RTX tested its rotating detonation engine at the RTX Technology Research Center (RTRC) in Connecticut, where the engineers had access to specialized facilities for testing. This includes the Center’s Jet Burner Test Stand, one of a few in the United States, that is capable of reaching the airflow rates, temperatures, and pressures to emulate high-speed flight.
Pratt & Whitney, an original engine manufacturer, had been designing and testing at the RTRC for over a decade. Then, they received a contract from the Air Force Research Laboratory to work with the RTRC and Raytheon to develop a rotating detonation engine for effectors. It’s this contract that led to the most recent development and performance testing.
“We’ve taken this technology out of the academic setting and into application,” said Chris Hugill, who leads Pratt & Whitney’s GATORWORKS development team. He also explained that getting support from the U.S. government, along with internal investment, is critical. “Our latest test results exceeded expectations, and they make a compelling case for further investment as we move toward full system ground testing and then vehicle flight test.”
Advantages of the Rotating Detonation Engine
These compact engines make space for additional fuel, sensors, and payload, making them useful for the military. Additionally, they are efficient and power-dense. By augmenting the range they can fly, it enables reaching targets at greater distances. Furthermore, the simple design requires few parts and promises cost-effective production.
However, creating these rotating detonation engines is no easy feat. Steven Burd, Pratt & Whitney’s chief engineer for Advanced Military Engines, explained, “It sounds simple, but getting the physics to work is not. When you really try to make the design do what you want it to do consistently with the right fuels and over the right operational conditions, that’s the challenge.”
The ring-shaped chamber allows air to be drawn in and injected with fuel, igniting and propelling the vessel.
One of the primary challenges was perfecting fuel injection, which had to be mixed and introduced in a precise, repeatable manner. In addition to that challenge, the team had to design and fabricate parts for the new system. This is where additive manufacturing comes in. RTX did not disclose what type of AM technology was used, but shared that the team used advanced techniques, including AM, to craft durable test articles with unusual specifications. They also used advanced physics-based modeling to guide their design, with each test providing data to feed into the model.
Beata Maynard, an associate director in Advanced Military Engines at Pratt & Whitney, explained that after about a year of development and performance testing, the team is focused on advancing their design and manufacturing. Then, they will integrate the engine into a ground vehicle for testing. As they continue to validate models with new data, the team will go forth using additive manufacturing, not only for test articles, but for engine production itself.
“The government is looking for missiles that go faster and fly farther,” Maynard said. “Combining Pratt & Whitney propulsion technology with a Raytheon vehicle could result in a weapons system that addresses warfighters’ immediate needs.” To learn more about the rotating detonation engine, click HERE.
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*All Photo Credits: RTX