India’s space program has achieved a major milestone with the successful hot test of its indigenous semi-cryogenic engine power head at 175 tonnes of thrust. Conducted on 24 June 2026 at the ISRO Propulsion Complex in Mahendragiri, Tamil Nadu, the test validated nearly 90 per cent of the engine’s designed capacity and placed India firmly on the path to deploying next-generation heavy-lift launch vehicles.

The test involved the Power Head Test Article, which integrates critical systems such as the gas generator, turbo pumps, pre-burner and control mechanisms, but excludes the thrust chamber.

This configuration allowed engineers to validate the integrated operation of the engine’s core systems under near-full-load conditions. The outcome was exactly as predicted, with all parameters performing within expected ranges.

The semi-cryogenic engine uses liquid oxygen as oxidiser and kerosene as fuel, a combination widely regarded as cleaner, more efficient and more economical than conventional liquid propulsion systems. ISRO’s refined kerosene, known as isrosene, reduces toxicity and enhances performance. The successful operation of the main turbopumps, delivering outlet pressures of 400 and 500 bar, further demonstrated the robustness of the design.

This was the eighth hot test in the series, following earlier trials at 94 tonnes and 120 tonnes of thrust. Achieving 175 tonnes, equivalent to 88 per cent of full capacity, has provided sufficient confidence to proceed towards the full-scale hot test at 200 tonnes. Once qualified, the semi-cryogenic propulsion stage, designated SC120 and powered by the 2000 kN-class SE2000 engine, will replace the current L110 liquid core stage of the Launch Vehicle Mark-3.

The upgrade is expected to substantially increase payload capacity, improve launch efficiency and lower mission costs. With the integration of the semi-cryogenic propulsion system and an uprated cryogenic upper stage, ISRO will be able to carry heavier payloads into geosynchronous transfer orbit, boosting capacity from four tonnes to five tonnes. This enhancement will enable more ambitious missions, including deep-space exploration and lunar expeditions.

ISRO Chairman V Narayanan described the test as a major achievement, noting that engineers had successfully demonstrated close to 90 per cent of the engine’s thrust capability without the thrust chamber. He confirmed preparations are underway for the complete engine hot test at the full 200-tonne thrust level.

The chairman also provided an update on the Gaganyaan human spaceflight program. He emphasised that the mission remains technology-intensive, requiring extensive human-rating of the launch vehicle before astronauts can be sent into space. ISRO plans three uncrewed missions before the first crewed flight, with announcements on the mission schedule expected soon.

The timing of this breakthrough is significant, as India’s space program is expanding rapidly across multiple fronts, from satellite launches and planetary exploration to human spaceflight and commercial launch services.

Developing an indigenous semi-cryogenic engine of this class reduces dependence on foreign technologies and strengthens India’s long-term launch capabilities.

Globally, semi-cryogenic propulsion systems are employed by leading space agencies such as NASA and Roscosmos for heavy-lift missions. ISRO’s achievement positions India alongside these advanced players, reinforcing its ambition to emerge as a leading space power.

The next milestone will be the full-scale hot test at 200 tonnes of thrust. If successful, it will mark the transition to a new generation of launch vehicles capable of carrying heavier payloads farther into space, supporting future Moon missions and beyond.

This achievement underscores India’s commitment to self-reliance in advanced propulsion technologies and its determination to expand its role in global space exploration.

Agencies