Indian startup tests first privately built full-flow staged combustion rocket engine

Indian space startup Agnikul Cosmos has successfully hot-fired EVEREST, the country's first privately developed full-flow staged combustion (FFSC) rocket engine, the company announced. The test was conducted at the Indian Space Research Organisation's (ISRO) propulsion complex at Mahendragiri in Tamil Nadu.

Full-flow staged combustion cycles route all propellant through pre-burners before entering the main combustion chamber, allowing higher chamber pressures and efficiency than conventional open or staged-combustion designs. Globally, only three commercial companies — SpaceX and Stoke Space in the United States and LandSpace in China — have previously demonstrated high-thrust FFSC engines in operation.

The EVEREST engine is designed to power the upper stage of Agnikul's Agnibaan launch vehicle, which targets the small-satellite market with a payload capacity of up to 300 kilograms to low Earth orbit. Agnikul stated that the engine uses liquid oxygen and refined kerosene (RP-1) as propellants and was manufactured using additive manufacturing techniques to reduce part count and lead time.

The hot-fire test validated the engine's ignition sequence, chamber pressure stability, and thrust vector control actuation, according to the company. Agnikul did not disclose the specific thrust level, burn duration, or chamber pressure achieved during this test.

ISRO provided the test infrastructure and safety oversight under the IN-SPACe authorization framework that governs private sector participation in India's space activities. The collaboration marks a continuation of public-private partnership in Indian space propulsion development.

Agnikul previously flew its suborbital technology demonstrator, Agnibaan SOrTeD, in May 2024 using a single-piece 3D-printed semi-cryogenic engine. The EVEREST engine represents a step toward the orbital version of Agnibaan, which the company aims to fly in 2025.

Full-flow staged combustion has historically been pursued by government programs such as the Soviet RD-270 and the U.S. Space Shuttle main engine precursors, but operational use remained rare until SpaceX's Raptor engine flew on Starship. Private-sector adoption of the cycle is seen as a marker of advanced propulsion maturity.

The company has not released independent telemetry data or third-party verification of the test results beyond its own announcement. Further tests, including long-duration burns and flight-qualification campaigns, are expected before the engine flies on an orbital mission.