The Indian Space Research Organisation (ISRO) has achieved a significant milestone with the successful completion of a critical sea-level hot test for its CE20 Cryogenic Engine.

Conducted at the ISRO Propulsion Complex in Mahendragiri, Tamil Nadu on November 29, 2024, the test featured advanced systems crucial for future space missions, including a restart enabling multi-element igniter and a water injection system to prevent flow separation at the nozzle divergent.

The CE20 engine, which has a nozzle area ratio of 100, was tested under ambient conditions. This test was critical for demonstrating the engine's restart capability, an essential feature for future missions.

A key highlight of the test was the successful performance of the multi-element igniter, a critical component for enabling engine restart in space.

Challenges and Innovations in Testing

Testing cryogenic engines at sea level is particularly challenging due to the engine's high area ratio nozzle, which has an exit pressure of around 50 mbar. One of the major concerns during testing at sea level is flow separation within the nozzle, which can cause vibrations and thermal issues that could lead to mechanical damage.

To address this, ISRO has implemented a novel Nozzle Protection System to mitigate the risks associated with flow separation and make the testing process more efficient and cost-effective. Previously, high-altitude tests at the High-Altitude Test (HAT) facility were required for CE20 flight acceptance, adding complexity and cost.

However, with the new sea-level testing approach and protective systems in place, the testing process has been streamlined, making it more accessible and less complicated.

Demonstrating Complex Cryogenic Engine Restart Capability

Restarting a cryogenic engine is a complex process, especially when dealing with vacuum ignition and the use of a multi-element igniter. ISRO had earlier demonstrated vacuum ignition of the CE20 engine without nozzle closure. In this recent test, the multi-element igniter's performance was thoroughly evaluated, with only the first igniter element activated, while the health of the remaining elements was monitored for further analysis. The test was successful, with both the engine and the facility performing as expected.

The CE20 engine, developed by ISRO's Liquid Propulsion Systems Centre, has proven its reliability by powering the upper stage of the LVM3 launch vehicle in six missions. It has been qualified to operate at a thrust level of 19 tonnes, with recent upgrades qualifying it for the Gaganyaan mission at 20 tonnes and an upgraded thrust level of 22 tonnes for future missions, such as the C32 stage.

These upgrades are crucial for enhancing the payload capability of the LVM3 launch vehicle. Conclusion With this successful test, ISRO continues to push the boundaries of space technology, showcasing innovation in cryogenic engine performance and ensuring readiness for future, more complex missions. The CE20 engine's development is a testament to ISRO's dedication to advancing India's space exploration capabilities, with significant implications for future missions like Gaganyaan and beyond.