Rotating detonation engines (RDEs) have roots in the 1950s. Early pioneers such as Arthur Nicholls at the University of Michigan studied whether spinning detonation waves in a ring of fuel injectors could produce propulsion. These initial experiments were difficult to sustain, and U.S. interest waned by the 1960s. However, research reports suggest Soviet scientists continued working on RDEs and achieved the first sustained detonation operation. After decades of dormancy, RDE interest revived in the 2000s. For example, the U.S. Air Force Research Laboratory began publishing on working RDE designs in the mid-2000s. By the 2010s, agencies and industry worldwide re-explored RDEs: the U.S. Navy’s research laboratory (NRL) even projected that RDEs might cut turbine fuel use by about 25 %, sparking new funding and experiments. In short, today’s RDE work builds on old ideas but with modern materials and computing, promising a new era of detonation-driven engines.
How RDEs Work
An RDE burns fuel very differently from a conventional engine. Fuel and oxidiser are continuously injected into an annular (ring-shaped) combustion chamber. Instead of a steady subsonic flame front (deflagration), the mixture is ignited by a supersonic detonation wave. This shockwave explodes through the propellants, compressing and burning them almost instantaneously. The detonation front races around the ring (often several times the speed of sound) in a continuous loop. Each pass ignites fresh mixture and forces hot gases out the nozzle, producing thrust. In effect the engine “bangs” the fuel rather than burns it, capturing more of its energy. Crucially, an RDE has no moving parts, the pressure spike from the detonation itself opens and closes the fuel-injection ports on each cycle. This mechanical simplicity can reduce engine weight and cost.
NASA engineers have demonstrated a full-scale RDE burning continuously for minutes. In their tests at Marshall Space Flight Center, the engine ran for 251 seconds straight at about 5,800 pounds of thrust. (The blue-white flame in the image shows the spinning detonation in the chamber.) Because detonations raise the pressure inside the engine (“pressure gain”), RDEs can generate more power from the same amount of fuel than a conventional engine. In short, an RDE is a compact, high-energy engine: it delivers high thrust while using fuel more efficiently than traditional combustion.
Credits: NASA
Current Research and Breakthroughs
Research on RDEs has accelerated in recent years. NASA has led many of the rocket-engine tests. In 2022 a 3D‑printed RDRE (rotating detonation rocket engine) at Marshall achieved about 4,000 pounds of thrust for roughly one minute. In late 2023 the same engine (using novel copper-alloy hardware) ran for 251 seconds at 5,800 pounds of thrust, a record burn. These tests proved RDEs can run continuously under realistic conditions. NASA reports that the 3D‑printed combustor withstood the “extreme heat and pressure” of detonation waves. (By comparison, most previous detonative engine tests lasted only a few seconds.) NASA is now planning larger RDREs (10,000 pounds class) for future space missions. Marshall engineers are also working with other groups (including NASA’s Glenn Center and the startup Venus Aerospace) to scale and integrate RDE technology.
Other organisations have made strides too. In the US defense sector, Pratt & Whitney (part of RTX Corp.) has completed a series of high-thrust RDE tests. This work is part of DARPA’s Gambit hypersonic missile programme; Pratt’s RDE unit is being designed to propel a future Mach‑5 weapon. General Electric’s aerospace division has demonstrated an RDE inside a dual-mode ramjet test rig. In 2023 they ran a supersonic air stream (about Mach 2.5) through a turbine plus RDE-equipped combustor, an experiment aimed at enabling sustained Mach 5 flight. On the academic side, Purdue University’s propulsion lab has built liquid-propellant RDEs (for example, burning liquid oxygen and RP-1 kerosene), and the University of Central Florida has tested small hydrogen-oxygen RDEs and novel “oblique detonation” concepts.
International teams are active as well. In space propulsion, Japan’s aerospace agency (JAXA) to flew an ethanol–nitrous RDE on a sounding rocket in 2024. (Earlier tests used methane–oxygen RDEs in space stages.) In 2021 Poland’s Institute of Aviation fired a rocket with a rotating detonation motor in a 3.2-second flight. In China, research institutes have demonstrated hybrid engines combining continuous RDEs with oblique detonation scramjets for hypersonic flight. Notably, in mid-2025 the US company Venus Aerospace achieved the first-ever flight of a full-sized RDE in America. Its rocket-powered test drone reached hypersonic speeds, proving the concept in flight. These efforts show RDEs are moving rapidly from lab curiosities to testable hardware.
Below is a list of institutions and their specific area of focus in RDE research
- NASA (Marshall & Glenn, USA): Full-scale RDRE rocket tests (4,000 – 5,800) pounds of thrust, multi-minute burns) for lunar and spacecraft propulsion.
- Venus Aerospace (USA): Hypersonic aircraft propulsion; conducted first U.S. flight test of an RDRE in 2025 for a Mach 4 passenger vehicle.
- Pratt & Whitney (RTX, USA): High-speed defense propulsion; completed RDE tests for DARPA’s Gambit hypersonic missile program.GE Aerospace (USA): Supersonic and hypersonic propulsion; demonstrated a Mach 2.5 dual-mode ramjet with integrated RDE.
- U.S. Air Force Research Lab (AFRL): Conducts core RDE research, including liquid-propellant detonations and multi-lab test coordination.
- U.S. Department of Energy (DOE) / DOE-funded labs (USA): Developing hydrogen-fueled RDEs for power generation and retrofitting gas turbines (e.g., Rolls-Royce systems).
- JAXA (Japan): Conducts spaceflight RDE experiments; launched methane–oxygen RDE rockets (2021) and also launched ethanol–nitrous RDE flights in 2024.
- Purdue University (USA): Builds experimental RDEs using liquid propellants, such as LOX/RP-1 combinations (tested in 2016).
- Beijing Power Machinery Institute (China): Researching hypersonic propulsion using combined continuous RDE and oblique detonation modules.
Applications in Aerospace and Beyond
RDEs offer potential benefits in many areas. In rocket propulsion, their high efficiency and compact size make them attractive for launchers and landers. NASA envisions RDE-powered engines for lunar/Mars landers or upper stages, since an RDE’s compact combustion can save weight. Indeed, experts predict RDE rockets could enable “lighter, more powerful” propulsion systems for deep-space missions. In hypersonic flight, RDEs are a frontrunner. They could power Mach 5+ missiles and aircraft, as defence agencies are already pursuing. RDEs can even act as air-breathing engines (ramjets/scramjets) when breathing oxygen in the atmosphere. For example, the NASA-Venus demonstrator is aimed at an aircraft cruising at Mach 4 without rocket boosters.
RDEs also have energy-sector applications. Because they raise pressure with each burn, RDEs could improve the efficiency of gas turbines and jet engines. U.S. DOE and gas-turbine makers are funding RDE projects to retrofit power plants: one study notes that even a few percent gain in thermal efficiency could significantly cut emissions. The U.S. Navy is interested in replacing parts of its ship turbines with RDE combustors to save fuel. In commercial aviation, a long-term possibility is supersonic airliners. Some analysts even mention future high-speed passenger aircraft (e.g. transcontinental Mach 3–4 flights) could use detonation-based engines.
Challenges and Commercialisation
Despite their promise, RDEs face major hurdles before mass deployment. Wave stability and control is a critical issue. Keeping a detonation wave running smoothly around the ring for long periods is hard, the engine must prevent the wave from blowing out or oscillating unpredictably. Designing fuel injectors that feed propellants in the right phase is complex. Combustor conditions are also extreme: continuous detonations create very high temperatures and pressures. This demands advanced materials and cooling systems. (NASA’s tests already required special copper alloys and cooling channels to survive the detonation environment) If materials fail, the engine can burn through in seconds.
Other challenges include throttling and control of thrust on demand, and managing the intense noise/vibrations from shock waves. Unlike a standard engine that throttles smoothly, an RDE’s power level is governed by the physics of detonation, which must be tamed. In short, engineers must learn to “embrace the instability”, controlling it rather than letting it destroy the cycle. Finally, practical issues like integrating an RDE into an airframe or spacecraft, certifying it for safe flight, and ensuring reliability over many cycles will need to be solved.
In summary, rotating detonation engines bring the reward of potentially much higher efficiency in a simple, compact package. If researchers can overcome the above obstacles, RDEs could redefine propulsion for rockets, jets and power generators in the coming decades.
Sources
- Rotating Detonation Engine: The Old Is New Again – Michigan Engineering News
https://news.engin.umich.edu/2017/03/rotating-detonation-engine-the-old-is-new-again/ - Navy Researchers Look to Rotating Detonation Engines to Power the Future – U.S. Naval Research Laboratory
https://www.nrl.navy.mil/Media/News/Article/2565333/navy-researchers-look-to-rotating-detonation-engines-to-power-the-future/ - ‘Ring of Fire’ Rocket Engines Put a New Spin on Spaceflight – Scientific American
https://www.scientificamerican.com/article/ring-of-fire-rocket-engines-put-a-new-spin-on-spaceflight/ - Avoiding the 7 Minutes of Terror: The Next Generation of Space Technology to Head to Mars – COSMOS (JAXA/ISAS)
https://cosmos.isas.jaxa.jp/avoiding-the-7-minutes-of-terror-the-next-generation-of-space-technology-to-head-to-mars - Pratt & Whitney Successfully Tests Rotating Detonation Engine – The Aviationist
https://theaviationist.com/2025/03/05/pratt-whitney-rotating-detonation-engine/ - NASA’s 3D-printed Rotating Detonation Rocket Engine Test a Success – NASA
https://www.nasa.gov/centers-and-facilities/marshall/nasas-3d-printed-rotating-detonation-rocket-engine-test-a-success/ - NASA Validates Revolutionary Propulsion Design for Deep Space Missions – NASA
https://www.nasa.gov/centers-and-facilities/marshall/nasa-validates-revolutionary-propulsion-design-for-deep-space-missions/ - Rotating Detonation Engines at the Forefront of Pressure Gain Combustion – Aerospace America
https://aerospaceamerica.aiaa.org/year-in-review/rotating-detonation-engines-at-the-forefront-of-pressure-gain-combustion/ - Advancements Continue in Rotating Detonation Engines – Aerospace America
https://aerospaceamerica.aiaa.org/year-in-review/advancements-continue-in-rotating-detonation-engines/ - Venus Aerospace Tests Rotating Detonation Rocket Engine – Aerospace Testing International
https://www.aerospacetestinginternational.com/news/venus-aerospace-tests-rotating-detonation-rocket-engine.html
