ISRO successfully conducted the eighth hot test of its Semi-Cryogenic Engine Power Head Test Article (PHTA) at a thrust level of 175 tonnes on June 24, 2026, at the ISRO Propulsion Complex (IPRC) in Mahendragiri, Tamil Nadu. The test achieved 88% of the engine’s full rated capacity and demonstrated the stable operation of critical subsystems including main turbopumps that delivered outlet pressures of 400 and 500 bar. This milestone brings India closer to deploying an indigenous semi-cryogenic propulsion stage that will significantly boost the payload capacity of the country’s heaviest operational rocket, the LVM3.
What Is the Semi-Cryogenic Engine?
A semi-cryogenic engine is a rocket propulsion system that uses Liquid Oxygen (LOX) as the oxidizer and purified kerosene as the fuel. The term “semi-cryogenic” refers to the fact that only LOX is stored at cryogenic temperatures (minus 183 degrees Celsius), while the kerosene remains at normal temperatures. This makes the engine simpler to handle and more cost-effective compared to fully cryogenic engines that use liquid hydrogen at minus 253 degrees Celsius.
ISRO’s SE2000 engine (formerly designated SCE-2000) works on an oxidizer-rich staged combustion cycle. In this cycle, a portion of the fuel is burned with most of the oxidizer in a pre-burner, and the resulting hot gases drive the turbopumps before being injected into the main combustion chamber. This design delivers higher efficiency than open-cycle gas generator engines. The engine generates 2,000 kilonewtons (kN) of thrust, equivalent to about 200 tonnes force, with a chamber pressure of 180 bar and a specific impulse of 335 seconds.
ISRO has developed a specialized grade of kerosene called Isrosene for this engine. The combination of LOX and Isrosene is non-toxic and environmentally cleaner than the hypergolic fuels currently used in the L110 core stage. ISRO is among a handful of space agencies worldwide with the capability to develop semi-cryogenic engines of this class.
The SE2000 Engine and the SC120 Stage
The SE2000 engine will power the Semi-Cryogenic Propulsion Stage (SC120). The SC120 stage carries approximately 120 tonnes of propellant and is designed to fit within the same dimensional envelope as the existing L110 stage, with a diameter of 4 metres and a height of 17.31 metres. The stage is being developed by the Liquid Propulsion Systems Centre (LPSC) of ISRO.
| Specification | SE2000 / SC120 Stage |
|---|---|
| Thrust | 2,000 kN (200 tonnes) |
| Propellants | LOX and Isrosene (purified kerosene) |
| Propellant Loading | 120 tonnes |
| Burn Duration | 190 seconds |
| Stage Diameter | 4 metres |
| Stage Height | 17.31 metres |
| Engine Cycle | Oxidizer-rich staged combustion |
| Chamber Pressure | 180 bar |
The SC120 stage is being developed to replace the current L110 core stage of the LVM3 (Launch Vehicle Mark 3), which is India’s most powerful operational rocket. The L110 stage uses two Vikas engines that burn a toxic hypergolic mixture of UDMH (unsymmetrical dimethylhydrazine) and nitrogen tetroxide (N2O4), generating a total thrust of about 1,600 kN. The switch to the SC120 stage will increase the LVM3’s payload capacity from 4 tonnes to 5 tonnes in Geosynchronous Transfer Orbit (GTO), representing a 25% improvement. The integration of the semi-cryogenic stage with an uprated cryogenic upper stage (C25) is part of ISRO’s broader roadmap to enhance the vehicle’s overall capability.
Why This Test Marks a Turning Point
This was the eighth hot test in a series using the Power Head Test Article (PHTA), which includes all engine systems except the thrust chamber. The PHTA configuration allows engineers to validate the complex propellant feed system, turbomachinery, pre-burner, and control components before integrating the thrust chamber for full-engine tests. The test campaign began in May 2023 at the newly commissioned Semi-cryogenic Integrated Engine and Stage Test facility (SIET) at IPRC.
The progression of thrust levels across the test series shows steady advancement toward the engine’s full design capacity:
| Test Phase | Thrust Level | Percentage of Full Capacity |
|---|---|---|
| Initial Tests | 94 tonnes | 47% |
| Intermediate Tests | 120 tonnes | 60% |
| Latest Test (June 24, 2026) | 175 tonnes | 88% |
The successful demonstration at 175 tonnes proved that the engine’s main turbopumps can sustain stable operation at high outlet pressures of 400 and 500 bar. All engine parameters remained within expected values throughout the test. ISRO Chairman V. Narayanan described the outcome as a major achievement and milestone for the agency’s propulsion programme. The results provide sufficient confidence to proceed toward demonstrating the engine powerhead at its full thrust of 200 tonnes (100% capacity).
Unlike the PHTA, the fully integrated engine includes the thrust chamber, where combustion gases are expanded through a nozzle to produce the final thrust. Testing the power head separately is a standard practice in rocket engine development, as it reduces risk by validating the core subsystems incrementally.
What Comes Next
With the confidence gained from this test, ISRO will now move toward demonstrating the engine powerhead at its full rated thrust of 200 tonnes (100% capacity). The agency also plans to conduct a fully integrated hot test of the complete SE2000 engine, including the thrust chamber, by the end of 2026.
Once the engine is fully qualified, the SC120 stage will be integrated into the LVM3 vehicle in place of the L110 core stage. The first flight of the upgraded LVM3 with the semi-cryogenic booster stage is expected by early 2027. This launch will mark the debut of India’s first operational semi-cryogenic propulsion system on a flight vehicle.
The semi-cryogenic propulsion system will also serve as the foundational technology for ISRO’s future Next Generation Launch Vehicle (NGLV), which is being designed for heavier payloads and reusability. The cleaner, non-toxic propellants also align with global environmental standards for launch operations.
The Semi-cryogenic Integrated Engine and Stage Test facility (SIET) at IPRC, which was dedicated to the nation in February 2024, is capable of testing engines up to 2,600 kN of thrust. The facility stands 51 metres tall and can conduct hot tests for durations of up to 375 seconds. With twin test bays, it allows parallel development of both the engine and the stage, accelerating the qualification timeline.
Key Takeaways
- ISRO conducted the eighth hot test of the Semi-Cryogenic Engine Power Head Test Article at 175 tonnes thrust (88% of full capacity) on June 24, 2026 at the ISRO Propulsion Complex (IPRC), Mahendragiri, Tamil Nadu.
- The SE2000 engine generates 2,000 kN of thrust using LOX and Isrosene in an oxidizer-rich staged combustion cycle with a chamber pressure of 180 bar.
- The engine will power the SC120 stage, which replaces the L110 core stage on the LVM3, increasing payload capacity from 4 tonnes to 5 tonnes in GTO (a 25% improvement).
- The Liquid Propulsion Systems Centre (LPSC) is developing the engine, while testing is carried out at IPRC. IPRC was originally established in 1982 as LPSC Mahendragiri and was elevated to an independent centre on February 1, 2014.
- Earlier PHTA tests were conducted at 94 tonnes (47%) and 120 tonnes (60%) thrust levels. The next step is a full 200 tonne (100%) demonstration, followed by an integrated engine hot test by end of 2026.
- The first flight of the upgraded LVM3 with the semi-cryogenic booster stage is targeted for early 2027, paving the way for heavier satellite launches, deep space missions, and India’s human spaceflight programme.
