The Indian Space Research Organization (ISRO) has achieved an important success. The much-anticipated C20 cryogenic rocket engine has successfully passed testing. Now, this engine will soon make an important contribution to the country’s future missions. ISRO successfully completed sea-level thermal testing of the CE20 cryogenic engine with a nozzle area ratio of 100 on November 29, 2024 at the ISRO Propulsion Complex in Mahendragiri, Tamil Nadu. The test also demonstrated the multi-element igniter required for engine restart capability.
Sea level testing risky
Testing the CE20 engine at sea level presented significant challenges, mainly due to the high-pressure ratio nozzle outlet pressure of approximately 50 mbar. The main issue during sea level testing was flow separation inside the nozzle, which resulted in severe vibration and thermal problems at the base of the flow separation, which could lead to mechanical damage to the nozzle. To alleviate this problem, flight testing of the CE20 engine is currently taking place at the High Altitude Test (HAT) facility, which adds complexity to the durability testing process.
To reduce the complexity of HAT testing, subsea testing using a nozzle protection system was designed to provide a cost-effective and less complex process for acceptance testing of cryogenic engines.
Restarting an engine is a difficult task
Restarting a cold engine is a complex process. The main challenges are vacuum ignition without nozzle closure and the use of multi-element igniters. ISRO had previously demonstrated in ground tests that the CE20 engine can perform vacuum ignition without closing the nozzle. Now, in this test, the performance of a multi-element igniter was also evaluated, in which only the first element is activated while the condition of the other two elements is monitored.
Performance parameters achieved by the engine
During this test, the engine and functional performance were normal and the performance parameters were met. The indigenous CE20 cryogenic engine manufactured by ISRO’s Liquid Propulsion Systems Center powers the upper stage of the LVM3 launch vehicle and is capable of operating at a thrust level of 19 tons. To date, the engine has successfully powered the upper stages of six LVM3 missions. Recently, the engine was qualified for the Gaganyaan mission with a thrust of 20 tons, and has also been qualified for a future C32-stage thrust increase to 22 tons, making it the first launch vehicle that will increase payload capacity.
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