India is simultaneously pursuing two distinct propulsion paths. On one hand, the country is working towards developing a jet engine capable of powering a fighter aircraft, Times of India reported.

On the other, it is building a new family of compact jet engines designed for cruise missiles and drones. This dual-track approach reflects both the strategic need for indigenous fighter propulsion and the growing importance of small, expendable engines for unmanned systems.

The Defence Research and Development Organisation’s Gas Turbine Research Establishment has announced the successful development of a 350 kg class expendable turbojet engine. Such engines are typically used in cruise missiles, drones, and increasingly in jet-powered loitering munitions.

The United States’ Tomahawk missile, for example, employs a 400 kg class engine producing around 4 kN thrust. India’s Long Range Land Attack Cruise Missile uses a 450 kg class Small Turbofan Engine, placing it in the same category of compact powerplants.

India’s armed forces have already begun integrating these technologies into operational systems. The army has ordered 106 Agniveg jet-powered loitering munitions. These weapons are designed to penetrate deep into enemy territory with a Circular Error Probable of less than five metres.

Being jet-powered, they fly at significantly higher speeds than the Iranian Shahed or Russian Geran drones, making them more effective in contested environments. This capability allows India to strike targets deep inside adversary territory with precision.

The propulsion ecosystem has reached a turning point with the demonstration of a Rotating Detonation Engine in the 5 kN thrust class by private firm D-Propulse. This test, conducted at a certified facility, marks a departure from the sub-scale experiments that have dominated global RDE research.

The ability to sustain a stable supersonic detonation wave with an integrated aerospike nozzle at higher thrust levels places India among a select group of nations with this capability.

Rotating Detonation Engines are notable for their simplicity and efficiency. By eliminating complex turbine blades, they reduce manufacturing costs and enable mass production of attrition-tolerant cruise missiles.

Fuel efficiency gains of 15–25% translate directly into longer ranges or extended loiter times without increasing missile size or weight. This allows aircraft to carry more precision standoff weapons per sortie, enhancing operational effectiveness.

Engines in the 5–10 kN thrust range are ideally suited for tactical missiles carrying warheads of 100–200 kg. Such systems would be smaller, faster, and more cost-effective than current designs.

Looking ahead, RDEs could power supersonic cruise missiles, high-altitude drones, and even replace conventional upper stages in launch vehicles. Combined-cycle drones integrating gas turbines with detonation stages are also a possibility in the longer term.

The proof motor demonstrated by D-Propulse was designed with aerodynamic and geometric constraints of a flight vehicle, showing clear operational intent. The combustor diameter, annular flow channel, injector placement, ignition sequencing, and nozzle geometry were configured to mirror deployable weapon systems. Challenges such as cyclic pressure shocks, heat fluxes, and preventing upstream detonation wave travel were addressed through advanced materials and nozzle engineering.

Despite these achievements, significant hurdles remain. Preventing inlet unstart caused by backpressure is critical, as it can destabilise the propulsion system. The vibro-acoustic profile of detonation engines requires advanced dampening solutions similar to those used in scramjets.

The current demonstration achieved Technology Readiness Level 5, validating the design in a relevant operational environment, but it was still conducted on a static rig with pre-conditioned feeds. Flight conditions will introduce additional complexities such as angle-of-attack distortions and fluctuating pressures.

The decision to move directly to a 5 kN thrust class rather than remain confined to smaller demonstrators reflects confidence in scaling and thermal management. Successfully pairing a pressure-gain combustor with an aerospike nozzle demonstrates mastery over expansion dynamics and flow-field management.

This achievement is unprecedented in the air-breathing RDE domain and positions India alongside the United States, Russia, and China, though much of their work remains classified or confined to lower thrust levels.

Transitioning from test rig to operational deployment will require endurance testing, materials validation, and integration with flight systems. The severe vibro-acoustic loads, thermal stresses, and structural fatigue associated with detonation combustion must be addressed.

Integration into missiles, drones, or launch vehicles will also demand advances in avionics, guidance, and systems engineering. Materials research, coatings, and cooling strategies will be critical to withstand detonation environments.

Indigenous RDE capability strengthens India’s expertise in advanced combustion and opens avenues for new platform designs. Sustained investment, rigorous testing, and collaboration with academia and research institutions will be essential to translate these developments into operational reality.

The demonstration of a 5 kN air-breathing rotating detonation engine marks a historic milestone, signalling India’s entry into an elite club of nations with demonstrated macro-scale capability in detonation propulsion.

Agencies