The Indian Space Research Organisation (ISRO) has made significant progress in the development of its semi-cryogenic engine and the associated rocket stage, marking a major milestone in India’s space technology capabilities.

The semi-cryogenic propulsion engine, known as SE2000, is being developed by the Liquid Propulsion Systems Centre (LPSC) and is designed to deliver a high thrust of 2000 kN.

This engine powers the new semi-cryogenic booster stage, designated SC120, which is intended to replace the existing liquid core stage (L110) of the LVM3 launch vehicle, thereby enhancing its payload capability. The semi-cryogenic engine uses a combination of liquid oxygen (LOX) and refined kerosene as propellants.

This choice brings advantages such as higher performance, non-toxic and non-hazardous propellants, and improved payload lift capacity, boosting the LVM3's payload to approximately 5 tonnes in Geosynchronous Transfer Orbit (GTO) compared to the prior 4 tonnes with the older stage.

By the end of 2025, ISRO plans to complete the development of the semi-cryogenic thrust chamber, a crucial component that forms the core of the engine. This thrust chamber is designed to endure the rigorous operating conditions involving extremely high temperatures and oxidizer-rich combustion, supported by advanced materials developed in partnership with Indian industry.

The semi-cryogenic engine uses a complex oxidizer-rich staged combustion cycle with a chamber pressure of around 180 bar and a specific impulse of about 335 seconds, enabling a substantial improvement over the hydrazine-based propulsion system of the previous core stage.

Following the thrust chamber development, ISRO targets the completion of the semi-cryogenic based rocket stage (SC120) by next year, 2026. This stage encapsulates the engine and associated systems, ready to be integrated into the launch vehicle. Several successful hot tests of the engine power head test article (PHTA)—which includes all engine systems except the thrust chamber—have been conducted in 2025, validating critical subsystems such as turbo-pumps, pre-burner, start system, and control components. The third hot test in May 2025 demonstrated stable and controlled performance up to 60% of the rated power, fine-tuning the ignition and start-up sequences.

The culmination of this development trajectory is the planned launch of the LVM3 rocket equipped with the semi-cryogenic booster stage by early 2027. This launch will mark the first flight of the upgraded LVM3 vehicle, showcasing the new semi-cryogenic propulsion technology and its enhanced capabilities.

The integration of the SC120 semi-cryogenic stage is expected to boost payload capability and overall efficiency for heavier satellite launches and complex space missions, positioning India among the few nations with advanced semi-cryogenic propulsion technology.

Thus, ISRO's semi-cryogenic engine program is advancing through key technical milestones: the thrust chamber readiness by the end of 2025, the complete semi-cryogenic rocket stage by 2026, and a full launch demonstration by 2027.

This development represents a transformative leap in Indian rocket propulsion, enabling greater payload capacities and enhancing self-reliance in space launch technologies through the adoption of safer, more efficient, and higher-performance rocket engines and stages.

IDN (With Agency Inputs)