The Rotating Detonation Engine being developed by Pratt & Whitney has no moving parts, which reduces complexity and costs, and could help enable high-speed, long-range flight with increased efficiency.
Pratt & Whitney announced it has completed a series of tests on its rotating detonation engine (RDE) work with the RTX Technology Research Center. The company says that the test was successful, and the positive results are now spurring additional internal investment to “accelerate a path to an integrated engine and vehicle ground test in the coming years” with the Department of Defense.
“Our testing simulated aggressive assumptions for how and where the rotating detonation engine needs to perform,” said Chris Hugill, senior director of GATORWORKS at Pratt & Whitney. “This testing validated key elements of Pratt & Whitney’s design approach and provides substantiation to continue RTX vehicle and propulsion integration to accelerate future capabilities for our customers.”
RDE is a novel, disruptive engine technology being developed by both DoD and industry for affordable, highly supersonic, mass effect weapons. This technology has no moving parts, compared to conventional engines such as turbofans, so it is less complex, and could help enable high-speed, long-range flight with increased efficiency.
These engines utilize a different thermodynamic cycle with high thermal efficiency and performance, which allows for a small, compact and cost-effective engine. This technology is getting increasingly more attention as the military is looking at better ways to reach highly supersonic and hypersonic speeds.
Pratt & Whitney is not the only engine manufacturer studying this technology. In 2023, General Electric Aerospace announced a successful demonstration of hypersonic dual-mode ramjet (DMRJ) rig which uses rotating detonation combustion (RDC) technology in a supersonic flow stream.
Gambit program
The U.S. Department of Defense has also been actively pursuing RDE development through DARPA’s (Defense Advanced Research Projects Agency) Gambit program, meant to develop RDE as “a new class of propulsion to enable standoff strike of time-critical targets from fourth generation fighters at campaign scale.”
The program, which is now complete, was intended to demonstrate the technology in a full-scale freejet test in two phases, each lasting 18 months. The first one included preliminary design and testing of the combustor and inlet, while the second one included detailed design, fabrication, and testing of the freejet test article.
The project was first announced in July 2022 when DARPA released a notice for a “Proposer’s Day” for industry. In 2023 Raytheon received a contract for the development of Gambit, which was described as “a first-of-its-kind engine development program.” RTX, the parent company of both Raytheon and Pratt & Whitney, said it would become the first company to apply rotating detonation engine technology into an actual test system.
Rotating Detonation Engine
The Rotating Detonation Engine (RDE) is an advanced propulsion concept that has drawn significant attention for its potential to enhance fuel efficiency and thrust while maintaining a compact design. Unlike traditional gas turbine engines, RDEs are mechanically simple, featuring no moving parts, which reduces complexity and may lower manufacturing costs.
Unlike conventional gas turbines or rocket engines that rely on deflagration—a slower, controlled combustion process—RDEs operate on the principle of detonation, a supersonic combustion process that releases energy more efficiently. At the core of an RDE is an annular combustion chamber, where fuel and oxidizer are injected continuously. Once ignited, a self-sustaining detonation wave propagates around this chamber, compressing and igniting the incoming fuel-air mixture. This eliminates the need for additional mechanical compression, as seen in traditional engines.
The key advantage of RDEs is their higher thermodynamic efficiency. Conventional engines lose a significant amount of energy as heat, whereas detonation-based combustion enables a more direct and complete energy conversion. This translates into lower fuel consumption, higher thrust-to-weight ratios, and the potential for simpler, more compact engine designs. Additionally, the reduced engine volume can be leveraged to increase fuel capacity or payload, offering operational advantages.
Despite these benefits, RDEs present engineering challenges. Maintaining a stable detonation wave over extended periods and ensuring uniform fuel distribution within the combustion chamber remain critical hurdles. Additionally, the extreme heat and pressure conditions necessitate advanced materials capable of withstanding such environments.
Major aerospace companies and research institutions are actively developing RDE prototypes, utilizing Computational Fluid Dynamics (CFD) simulations and experimental testing to refine designs and improve stability. As research progresses, RDE technology has the potential to redefine propulsion systems across multiple domains, making it a strong candidate for military aircraft, hypersonic vehicles, and space propulsion systems.
