BENGALURU: Isro Thursday said it successfully conducted a sea-level hot test of its CE20 cryogenic engine at 22-tonne thrust at the Isro Propulsion Complex on March 10.The CE20 engine powers the upper cryogenic stage of the LVM-3 launch vehicle. The latest test was carried out using a nozzle protection system and a multi-element igniter.“Earlier, sea-level tests using the nozzle protection system were conducted at a thrust level of 19 tonnes. The latest trial qualifies sea-level testing of the engine at the higher 22-tonne thrust level. The test lasted 165 seconds,” Isro said.Isro plans to operate future LVM-3 missions with an uprated C32 cryogenic stage delivering 22-tonne thrust from the CE20 engine in order to enhance the rocket’s payload capability. “As a result, the flight acceptance test of the CE20 engine will also need to be conducted at the higher thrust level,” Isro said.The space agency said testing the CE20 engine at sea level poses significant challenges due to the engine’s high area-ratio nozzle, which has an exit pressure of about 50 mbar. A key concern during such tests is flow separation inside the nozzle, which can cause severe vibrations and thermal stress at the separation point and potentially damage the nozzle.According to Isro, the cryogenic engine used in the latest trial has undergone a record 20 successful hot tests. These tests have enabled the demonstration of several technologies using a single engine.“These include ignition using a multi-element igniter, ignition margin demonstration for Gaganyaan mission across a wide range of propellant tank pressures and pre-ignition chamber pressures, and engine qualification for Gaganyaan at 20-tonne thrust level,” Isro added.The tests also demonstrated and qualified operation at 22-tonne thrust, the boot-strap mode start of the CE20 engine without a start-up system to enable in-flight restart, qualification of indigenous turbopump bearings and sensors, and qualification of the nozzle protection system for hot tests of a high area-ratio nozzle at sea level.Isro said the performance of the engine and the test facility remained as expected throughout the test duration.