Nearly seven decades after American scientists first proposed the concept of an Oblique Detonation Engine (ODE), Chinese researchers have claimed a significant breakthrough in the development of this advanced hypersonic propulsion system. A state-sponsored team from the China Academy of Launch Vehicle Technology (CALT) and Northwestern Polytechnical University successfully conducted a ground-based test of an ODE chamber using RP-3 aviation kerosene, marking a major milestone in the pursuit of next-generation hypersonic engines.
Engine ignition and sustained detonation at Mach 8- Via SCMP/CALT
Published on May 6, 2025, in the Chinese-language Journal of Aerospace Power, the results demonstrate the technical viability of using standard jet fuel in an engine operating under Mach 8 flight conditions at 30 km altitude. This achievement stands in stark contrast to conventional scramjet engines, which require cryogenic hydrogen fuel, a major logistical and engineering hurdle for practical deployment.
Technical Leap in Hypersonic Combustion
The ODE test showcased a stable oblique detonation wave—a supersonic combustion phenomenon where shock waves and combustion processes are coupled to generate thrust without moving parts. Unlike traditional engines, where combustion occurs subsonically or in a scramjet’s turbulent flow, the ODE enables instantaneous fuel-air mixing and ignition along thin, high-pressure detonation fronts. This approach can significantly reduce engine length and mass while enabling efficient propulsion at extreme speeds.
In this latest test, the Chinese research team injected RP-3 fuel through a central injector with four 0.3 mm-diameter ports directly into a supersonic airflow inside the combustion chamber. Ignition was triggered by a 20-degree wedge fitted with two 2 mm surface bumps, creating controlled turbulence and initiating detonation. Optical windows embedded in the engine allowed researchers to observe the blue-white detonation fronts and yellow afterburning zones, visual indicators of partially mixed combustion.
Numerical simulations incorporating a 10-step chemical reaction model confirmed the occurrence of detonation, with pressure spikes recorded at 272 kilopascals—over ten times the inlet pressure—confirming intense combustion and thrust generation. The engine sustained this state for 2.2 seconds, well beyond the 1-second minimum benchmark that the Chinese military had earlier set for operational consideration, according to a February study by the China Airborne Missile Academy.
The ODE concept was originally proposed in 1958 by researchers at the University of Michigan under a U.S. Air Force contract. It aimed to create a hypersonic engine that merged shock waves with combustion, theoretically enabling flight from Mach 6 to Mach 16. However, during the Cold War and beyond, the idea remained mostly theoretical due to unresolved challenges in stabilizing detonation waves, managing thermal loads, and achieving reliable ignition in high-speed, low-pressure environments.
While NASA and U.S. academic institutions such as the University of Central Florida made progress—including a 2021 test that stabilized an oblique detonation wave in a Mach 5+ flow—U.S. efforts have lagged in translating these findings into sustained, practical propulsion systems. Chinese researchers, in contrast, have moved aggressively from laboratory experiments to integrated ground testing.
The recent test is especially notable when compared to an earlier December 2024 experiment by the Chinese Academy of Sciences, which demonstrated a 50-millisecond detonation at Mach 9 using kerosene. At the time, critics dismissed the duration as insignificant. However, the 2.2-second sustained ignition achieved by CALT is a 40-fold improvement, dispelling prior skepticism and positioning China ahead in the race to operationalize this revolutionary engine.
Despite this breakthrough, limitations remain. The combustion zone only occupied 39% of the 90 mm-high flow channel, with outer regions receiving insufficient fuel for efficient mixing. Additionally, pressure fluctuations at the exhaust occasionally disrupted wave stability. Researchers suggested further refinements, including restructuring the fuel injector and extending mixing channels to enhance uniformity.
Nonetheless, the current performance is more than sufficient to explore military applications. Oblique detonation engines offer significant potential for hypersonic cruise missiles, air-launched gliders, and next-gen aerospace vehicles. These engines promise higher efficiency, reduced cooling demands, and greater thrust-to-weight ratios than traditional scramjets, enabling platforms that could travel from Shanghai to San Francisco in under an hour.
China’s long-term plans, reportedly targeting crewed hypersonic aircraft by 2035, underline the strategic importance of this technology. Alongside its hypersonic missile arsenal—which includes systems like the DF-17, YJ-21, and DF-27—this propulsion advance enhances China’s growing dominance in the high-speed flight domain.
The ODE is not the only case where China has revitalized abandoned American technology. In February 2024, Chinese naval engineers announced progress on hypersonic kinetic energy shells—a concept originally proposed by the U.S. Navy in 2012 for use with electromagnetic railguns. While the U.S. dropped the program in 2021, China appears to have successfully solved key guidance and materials challenges.
Similarly, in the nuclear sector, China has recently claimed success in operationally refueling a thorium-based reactor, an experimental concept first tested in the U.S. in the 1950s and later abandoned due to political and technical hurdles.
With its latest ODE test, China has again demonstrated its ability to revive, refine, and surpass American-origin technologies, converting theoretical concepts into tangible strategic capabilities. As the global hypersonic race intensifies, China’s progress underscores both a technical mastery and a long-term commitment that may reshape the balance of aerospace power in the coming decades.
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