ISRO Conducts Full Nozzle Cryogenic Engine (CE-20) Test Outside Vacuum Chamber to Prepare for Inflight Re-Ignition

By R Anil Kumar

• Preparing for inflight re-ignition, full nozzle cryogenic engine (CE20) undergoes test outside vacuum chamber

• This test was done with multi element ignitor and water injection system at nozzle divergent to prevent flow separation

• Performance of a multi-element igniter that is required for engine restart capability was also demonstrated during this test

Bengaluru, December 11. ISRO has successfully carried out the sea level hot test of its CE20 Cryogenic Engine featuring a nozzle area ratio of 100 at ISRO Propulsion Complex, Mahendragiri, Tamil Nadu on November 29, 2024. Performance of a multi-element igniter that is required for engine restart capability was also demonstrated during this test.

Testing the CE20 engine at sea level poses considerable challenges, primarily due to the high area ratio nozzle which has an exit pressure of approximately 50 mbar. The 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.

In order to mitigate this issue, the flight acceptance tests for CE20 engines are currently being performed at the High-Altitude Test (HAT) facility, thereby adding complexity to the acceptance testing procedure.

To reduce the complexity related to the testing at HAT, a sea level test utilizing an innovative Nozzle Protection System was devised that has paved the way for a cost-effective and less complex procedure for acceptance testing of the cryogenic engines.

Restart of a cryogenic engine is a complex process. Major challenges are vacuum ignition without nozzle closure and use of multi-element igniter.

ISRO has demonstrated vacuum ignition of CE20 engine without nozzle closure in earlier ground tests. In this test, the multi-element igniter performance was also evaluated, wherein, only the first element was activated, while the health of the other two elements were monitored.

During this test, both the engine and facility performance were normal, and the required engine performance parameters were achieved as anticipated.

The indigenous CE20 cryogenic engine developed by the Liquid Propulsion Systems Centre of ISRO is powering the upper stage of the LVM3 launch vehicle and has been qualified to operate at a thrust level of 19 tonnes.

This engine has successfully powered the upper stage of six LVM3 missions so far. Recently, the engine was qualified for the Gaganyaan mission with a thrust level of 20 tonnes and also to an uprated thrust level of 22 tonnes for the future C32 stage, towards enhancing the payload capability of LVM3 launch vehicle.