ISRO successfully tests semi-cryogenic engine at 175-tonne thrust milestone

ISRO has successfully completed a hot test of its semi-cryogenic engine Power Head Test Article at 175 tonnes of thrust, paving the way for full-capacity testing. The milestone strengthens India's next-generation launch vehicle programme and future deep-space and human spaceflight missions.

Chennai: The Indian Space Research Organisation (ISRO) has successfully completed a crucial hot test of its semi-cryogenic engine power head test article (PHTA) at a thrust level of 175 tonnes, marking a major milestone in the development of India’s next-generation launch vehicle propulsion technology.

The test was conducted at the ISRO Propulsion Complex (IPRC) in Mahendragiri, Tamil Nadu recently. The successful trial is eighth in the series of hot tests conducted using the Power Head Test Article, which incorporates all the major systems of the engine except the thrust chamber.

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The latest test was aimed at studying the engine’s performance during the build-up phase after pre-burner ignition and demonstrating steady-state operation at a significantly higher thrust level.

For the first time, the engine powerhead was operated at 175 tonnes of thrust, representing 88 per cent of its full rated capacity.

Earlier tests had been successfully completed at 94 tonnes (47 per cent thrust) and 120 tonnes (60 per cent thrust). During the latest trial, the engine’s main turbopumps also performed as designed, delivering outlet pressures of 400 and 500 bar.

ISRO said the test progressed exactly as predicted, with all engine parameters remaining within the expected range throughout the firing. The successful demonstration has provided the space agency with the confidence required to proceed towards testing the engine at its full rated thrust of 200 tonnes, bringing the indigenous semi-cryogenic engine programme a significant step closer to completion.

The Semi-Cryogenic Propulsion Stage (SC120), powered by the 2,000-kilonewton-class SE2000 engine, is being developed to replace the existing L110 liquid core stage of the Launch Vehicle Mark-3 (LVM3), India’s heaviest operational launch vehicle.

The upgrade is expected to substantially enhance the rocket’s payload carrying capacity while improving overall performance and operational efficiency. Unlike conventional propulsion systems, the semi-cryogenic engine uses environmentally cleaner and non-toxic propellants—Liquid Oxygen (LOX) and purified kerosene, known as Isrosene.

According to ISRO, integrating the new semi-cryogenic stage with an upgraded cryogenic upper stage will significantly strengthen the LVM3’s capabilities, supporting future high-capacity satellite launches, deep-space exploration missions and India’s expanding human spaceflight programme.