Defence propulsion startup D-Propulse on Tuesday announced the successful demonstration of India's first indigenously developed 5 kN air-breathing Rotating Detonation Engine (RDE) integrated with an aerospike nozzle, marking a milestone in the country's advanced propulsion capabilities.The hot-fire demonstration, conducted at a DRDO test facility, achieved stable 5 kN thrust, validating the technology at Technology Readiness Level (TRL)-5, which indicates validation in a relevant operational environment.Incubated at IIT Madras, the company said the demonstration marks the transition from laboratory-scale validation to an integrated prototype. It is targeting a flight-ready engine by December 2027.Unlike conventional jet engines, Rotating Detonation Engines use pressure-gain combustion, improving thermodynamic efficiency while eliminating moving parts inside the combustor, resulting in a simpler engine architecture. According to D-Propulse, the technology offers 15–25% higher thermodynamic efficiency than conventional air-breathing propulsion systems and can be manufactured through precision machining rather than complex turbine assemblies, reducing production costs and lead times. Watch video here: Saurav Jha, Founder, D-Propulse, said, "This is the first successful demonstration of an indigenous Rotating Detonation Engine at this thrust class in India. Achieving TRL-5 validates the core engine architecture in a relevant operational environment. Our next milestone is to make the engine flight-ready by December 2027." Unlike a laboratory demonstrator, the prototype has been developed as the proof motor for a flight-capable design. D-Propulse is developing the technology for future defence applications, including cruise missiles, target drones and high-speed unmanned aerial vehicles (UAVs). The successful TRL-5 validation marks a key step in strengthening India's indigenous propulsion ecosystem and expanding domestic capabilities in next-generation air-breathing propulsion.