ISRO plans to restart cryogenic stage in flight for mission advantages-Chairman V Narayanan

By R Anil Kumar

• The Chairman also said there were no glitches as reported in the media in ISRO’s first Space Docking Experiment (SpaDeX) mission.

Bengaluru, February 9. A day after ISRO successfully carried out the ignition trial of the indigenous CE20 cryogenic engine, its Chairman and Secretary of Department of Space V Narayanan on Saturday, February 8, said that the test would be advantageous to missions.

The Chairman also said there were no glitches as reported in the media in ISRO’s first Space Docking Experiment (SpaDeX) mission.

“We want to restart the cryogenic stage in the flight for mission advantages. So, we recently carried out a test towards that,” Narayanan said on the sidelines of the 15th Biennial Edition of Aero India International Seminar 2025, held in Bengaluru.

On February 7, ISRO successfully carried out the ignition trial of the indigenous CE20 cryogenic engine powering the upper stage of LVM3, with a multi-element igniter under vacuum conditions, which simulates the engine ignition in the vacuum condition of space. This test was carried out in the High-Altitude Test Facility at ISRO Propulsion Complex in Mahendragiri, Tamil Nadu.

According to an ISRO release, during this test, the ignition of the engine Thrust Chamber was carried out with a multi-element igniter in vacuum, under the tank pressure conditions that are expected to prevail at the time of restarting the cryogenic engine in flight.

The performance of the engine and the facility during the test was normal and as expected, it added.

On reports in the media on glitches in the SpaDeX mission, Narayanan said, “No glitches, right now it is docked. We are going step by step. We are studying and then we are planning to do a lot of experiments.”

On January 16, the space agency successfully performed the docking of satellites as part of the Space Docking Experiment (SpaDeX) and it also announced that post docking, control of two satellites as a single object was successful. In this mission, NVS-02 navigation satellite was successfully injected into the intended Geosynchronous Transfer Orbit.

But on February 2, ISRO issued an update stating that the orbit raising operations towards positioning the satellite to the designated orbital slot could not be carried out as the valves for admitting the oxidizer to fire the thrusters for orbit raising did not open.

The ISRO chairman was the chief guest at Aero India International Seminar 2025. This year, the international conference on military airworthiness explored the topic ‘futuristic aerospace technologies: challenges in design validation’.

Preparing for inflight re-ignition – Vacuum ignition trial of Cryogenic engine with Multi-element Igniter conducted successfully

On February 7, 2025, ISRO successfully carried out the ignition trial of the indigenous CE20 cryogenic engine powering the upper stage of LVM3, with a Multi-element igniter under vacuum conditions, which simulates the engine ignition in the vacuum condition of space. This test was carried out in the High Altitude Test Facility at ISRO Propulsion Complex, Mahendragiri, Tamil Nadu. During this test, the ignition of the engine Thrust Chamber was carried out with a multi-element igniter in vacuum, under the tank pressure conditions that are expected to prevail at the time of restarting the cryogenic engine in flight.The performance of the engine and the facility during the test was normal and as expected.

Restarting a cryogenic engine is inherently complex and as part of the studies related to the restart operation, ISRO is exploring the initiation of turbopumps in bootstrap mode rather than the stored gas system. In this approach, both the thrust chamber and gas generator are expected to re-ignite under tank head conditions. ISRO has outlined a series of tests aimed at engine starts in bootstrap mode towards enhancing the capability for multiple cryogenic engine restarts during flight.

Previously, the engine ignition trial using multi-element igniter was carried out under ground conditions outside the vacuum chamber. The engine isalready qualified to operate for thrust levels ranging from 19t to 22t in flight with single start and is qualified for Gaganyaan mission. The engine was developed by Liquid Propulsion Systems Centre of ISRO.