ISRO has achieved a major milestone in its semi-cryogenic engine development program by successfully conducting the first hot test of the Engine Power Head Test Article (PHTA) on March 28, 2025, at the ISRO Propulsion Complex in Mahendragiri, Tamil Nadu. This engine is a key component of the SE2000 semi-cryogenic engine, which will replace the L110 liquid core stage in the LVM3 rocket, enhancing its payload capacity from 4 tons to 5 tons in Geosynchronous Transfer Orbit (GTO). reported Simon Mansfield of Space Daily, a Australia based space news portal.. 

The SE2000 semi-cryogenic engine represents a significant leap in India's rocket propulsion technology, combining advanced engineering with strategic partnerships. Its core components include a thrust chamber for combustion, turbo pumps for propellant delivery, a pre-burner for turbine drive gases, an ignition system for controlled start-up, and precision control mechanisms.

The engine employs an oxidizer-rich staged combustion cycle - a complex design where excess liquid oxygen is partially burned in the pre-burner to drive turbines before full combustion in the main chamber. This enables exceptional performance with combustion chamber pressures reaching 180 bar and propellant feed systems handling up to 600 bar pressures.

Constructed using specialised alloys and composites resistant to extreme temperatures and corrosive oxidizer-rich gases, the engine achieves a specific impulse of 335 seconds while using non-toxic LOX/kerosene propellants. Notably, both the engine components and the space-grade kerosene are manufactured through collaborations with Indian aerospace industries, demonstrating growing domestic capability in advanced propulsion systems.

To validate this technological marvel, ISRO established the Semi-Cryogenic Integrated Engine Test (SIET) facility at Mahendragiri, inaugurated in February 2024.

This ₹1,800 crore complex features:

High-pressure propellant storage systems handling 2600 kN thrust requirements
A PLC-based control system with 2,500+ monitoring parameters
Indigenous data acquisition systems capturing 1,000 samples/second
Automated safety protocols for handling 300+ ton propellant loads

The facility's capabilities were proven during the March 28, 2025 hot test, where the Power Head Test Article demonstrated stable ignition and 2.5-second operation - a crucial milestone before full-engine integration. When operational, this engine will boost LVM3's GTO payload capacity from 4 to 5 tons while reducing launch costs through reusable design elements. Its success positions India among only four nations mastering high-thrust oxidizer-rich staged combustion technology.

ISRO has been conducting validation tests for its semi-cryogenic engine development using intermediate setups like the Power Head Test Article (PHTA), which incorporates all engine systems except the thrust chamber. These tests aim to assess the integrated functioning of critical subsystems, including turbo pumps, pre-burners, start-up systems, and control units. Before assembly into the PHTA, these subsystems undergo thorough qualification. A recent 2.5-second hot fire test successfully demonstrated ignition and smooth transition into bootstrap mode operation, confirming the reliability of the integrated systems.

To refine the ignition sequence for PHTA, ISRO developed a separate test unit called the Pre-burner Ignition Test Article (PITA). Testing with PITA enabled engineers to optimize the start-up procedure, ensuring seamless engine ignition during subsequent tests. The results from the March 28 test validated the ignition process and provided critical insights into operational performance.

This test validated the integrated performance of critical subsystems such as the pre-burner, turbo pumps, start system, and control components during a brief 2.5-second firing. The smooth ignition and operation demonstrated during the test marked a major breakthrough in ISRO's efforts to develop a high-thrust semi-cryogenic engine with a thrust capacity of 2000 kN.

Following this success, ISRO plans to conduct additional tests on the PHTA to fine-tune performance parameters before completing the fully integrated engine, advancing India's space exploration ambitions.

These efforts are part of ISRO's broader goal to develop a 2000 kN thrust semi-cryogenic engine powered by a Liquid Oxygen (LOX)-Kerosene propellant combination for future launch vehicle booster stages.

SD Report