ISRO on Thursday said it has successfully conducted a sea level hot test of its cryogenic engine (CE20) at 22 tonne thrust using nozzle protection system and multi-element igniter at its Propulsion Complex at Mahendragiri in Tamil Nadu.

Earlier, the sea level tests utilising the nozzle protection system were being carried out at a 19-tonne thrust level.

The CE20 cryogenic engine powers the upper cryogenic stage of the Launch Vehicle Mark-3 (LVM3).

"In order to enhance the payload capability of the LVM3 vehicle, future missions of LVM3 are planned to be operated with an uprated C32 stage with 22 tonne thrust for the CE20 engine. In view of this, the flight acceptance test of the CE20 engine also needs to be conducted at 22 tonne thrust level," ISRO said in a post on its website.

"Therefore, the present test (on March 10) qualified the sea-level testing of the engine with a test duration of 165 seconds at 22t thrust level using the Nozzle Protection System (NPS). The performance of the engine as well as the test facility was as expected during the entire test duration," it said.

Noting that testing the CE20 engine at sea-level possess considerable challenges primarily due to the high area ratio nozzle, which has an exit pressure of ~50 mbar (millibar), the space agency said, "Main concern during testing at sea-level include flow separation inside the nozzle, which leads to severe vibrations and thermal problems at the flow separation plane leading to possible mechanical damage of the nozzle."

"The Cryogenic engine utilized for this test has undergone a record maximum number of hot tests (20 Nos) successfully, that has enabled the demonstration of several key technologies using a single engine, such as engine ignition using multi element igniter, ignition margin demonstration for Gaganyaan over a wide range of propellants tank pressure and pre-ignition chamber pressure, engine qualification for Gaganyaan at 20 tonne thrust level....." it added.