In 1958, a team of US researchers proposed a unique concept for a hypersonic engine called the Oblique Detonation Engine (ODE). Nearly seven decades later, China has not only borrowed the idea but also claimed to have made a significant breakthrough with the ODE as it forges ahead of the United States in the hypersonic race.
A state-backed Chinese research team reported a successful ground test of an oblique detonation engine (ODE) chamber using RP-3 aviation kerosene in a peer-reviewed article published in the Chinese-language Journal of Aerospace Power earlier this month. Thus, developing a hypersonic engine that runs on regular jet fuel, as recently reported by the South China Morning Post.
This experiment has been projected as a breakthrough because hypersonic engines, typically the popular scramjet engines, use hydrogen fuel.
This experimentation study was jointly undertaken by researchers from the China Academy of Launch Vehicle Technology (CALT), the nation’s premier institute for aerospace propulsion, and Northwestern Polytechnical University. The results were published in the journal on May 6, 2025.
The researchers stated that the experiment demonstrated the concept’s technological viability for military application by igniting and maintaining stable detonation waves for more than two seconds while replicating flight circumstances at Mach 8 (or eight times the speed of sound) and an altitude of 30 kilometres.
Earlier, a February evaluation of ODE by the China Airborne Missile Academy stated that a ground test lasting more than a second would be necessary to persuade the military to use the technology in combat systems.
The ODE idea, first proposed by University of Michigan researchers under a US Air Force contract in 1958, promises propulsion without moving parts by combining combustion and shock waves.
An excerpt from the NASA Ames Research Center website explains the technological concept: “Wave combustors, which include the Oblique Detonation Wave Engine (ODWE), are attractive propulsion concepts for hypersonic flight. These engines utilize oblique shock or detonation waves to rapidly mix, ignite, and combust the air-fuel mixture in thin zones in the combustion chamber. Benefits of these combustion systems include shorter and lighter engines, which will require less cooling and can provide thrust at higher Mach numbers than conventional scramjets.”
It further adds, “The wave combustor’s ability to operate at lower combustor inlet pressures may allow the vehicle to operate at lower dynamic pressures, which could lessen the heating loads on the airframe.”
In 1978, NASA researchers hypothesised that the ODE might allow sustained hypersonic cruise from Mach 6 to Mach 16. However, the idea was viewed with skepticism because of significant technological obstacles at the time.
Despite that, the project has not been fully abandoned. For instance, in 2021, researchers from the University of Central Florida (UCF) achieved a significant milestone by stabilizing a sustained oblique detonation wave in their High-Enthalpy Hypersonic Reacting Facility (HyperReact).
This prototype demonstrated the ability to maintain a detonation wave in hypersonic flow, potentially enabling aircraft to reach speeds up to Mach 17. The research was later published in the Proceedings of the National Academy of Sciences.
From what we know, the US programs face challenges such as stabilizing detonation waves for extended periods and managing extreme heat and pressure.
The latest Chinese experiment comes as a fierce race to develop hypersonic technology is raging. China has arguably emerged as a hypersonic leader. By 2035, it plans to create a small fleet of crewed hypersonic aircraft that can reach any location on Earth in a matter of hours. It has also developed and fielded multiple hypersonic weapons, including the DF-17, the YJ-21, the DF-27, etc.
Meanwhile, the US continues to trail China in hypersonic technology, which makes Beijing’s use of an original US ODE concept even more intriguing. However, this is not the first time Beijing has overcome technical hurdles associated with an original US concept that failed to take off in America.
In February 2024, Chinese naval researchers said they had overcome technical problems with hypersonic speed ‘smart kinetic energy shells’ fired from an electromagnetic rail gun.
The US Navy first introduced the concept of a ‘dream shell’ in 2012. After being fired from electromagnetic rail guns, the shell would navigate at Mach 5, guided by SatNav signals. The plan was to develop and test-fire the shell within five years, but research was still ongoing in 2017. However, by 2021, the US had “abandoned” the program.
More recently, Chinese state media reported that Chinese scientists have achieved a significant nuclear breakthrough by successfully refueling a thorium-based reactor while it remains operational. Incidentally, the United States developed this technology in the mid-20th century before abandoning it.
What Did Chinese Researchers Achieve With ODE?
In December 2024, the Chinese Academy of Sciences led a team that reported a 50-millisecond kerosene-fueled explosion in a wind tunnel at Mach 9. At the time, critics dismissed this accomplishment as a lab curiosity, citing the extremely brief duration.
These doubts have now been challenged by the CALT’s recent test, which is 40 times longer and features observable, stabilized detonation waves, notes the SCMP report.
Detailing the specifics of the experiment, the report stated that a central fuel injector with four 0.3 mm-diameter (0.01 inch) holes sprayed RP-3 kerosene into a supersonic airstream inside the experimental engine’s combustion chamber. This was followed by a detonation that was initiated by a 20-degree wedge with two 2mm (0.8 inch) bumps.
Yellow afterburning zones and blue-white detonation fronts were visible through optical windows, which are signs of partial fuel mixing. Notably, the engine produced a significant amount of thrust, as evidenced by numerical simulations with a 10-step chemical model that matched pressure spikes at 272 kPa post-detonation, more than ten times the pre-wave pressure.
“The combustion zone remained stable within the 2.2-second effective test window,” wrote the research team led by researcher Yang Yang in the peer-reviewed journal. “The findings prove the technical feasibility of internal-injection liquid-fuelled oblique detonation engines.”
The paper admits some significant limits despite advancements. For example, only 39% of the 90 mm-high flow channel was filled with fuel, leaving the outer areas lean, and wave stability was occasionally disturbed by pressure changes in the exhaust. The group suggested a few solutions, including rebuilding the injector and lengthening the fuel-air mixing channels.
While it would take years before the ODE could help develop a hypersonic airliner that would reduce flight time from Shanghai to San Francisco to an hour, the report states that this technology could be adapted for military applications sooner.
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