ISRO Successfully Tests Boot-Strap Start of CE20 Cryogenic Engine for Future Multi-Orbit Missions
The 10-second high-altitude test at Mahendragiri marks a major step toward enabling multiple in-flight restarts of the LVM3 upper-stage engine, boosting mission flexibility and payload efficiency for upcoming deep-space and human-spaceflight missions.
The Indian space agency today said it has successfully demonstrated the boot-strap mode starting of the CE20 cryogenic engine, a major step towards enhancing the restart capability and mission flexibility of future LVM3 flights.
The Indian Space Research Organisation (ISRO) said boot-strap mode means starting the gas-generator cycle cryogenic engine without any auxiliary start-up system.
According to ISRO, the CE20 cryogenic engine, powering the LVM3 upper stage, is already qualified for operation at thrust levels ranging from 19 to 22 tonnes in flight with a single start.
The engine has also been qualified for the Gaganyaan missions.
During nominal operation, the engine ignition is initiated under tank head conditions, followed by the start of turbopumps using a stored gas start-up system.
For future missions, multiple in-flight restarts of the CE20 engine will be required for mission flexibility towards multi-orbit missions, ISRO said.
However, with the present configuration, each restart demands an additional start-up gas bottle and associated systems, leading to a reduction in vehicle payload capability.
Hence, achieving boot-strap mode start - where the engine builds up to steady operation without external start-up assistance - is essential.
In this regard, a boot-strap mode start test on the CE20 cryogenic engine was successfully conducted under vacuum conditions in the High-Altitude Test (HAT) facility at ISRO Propulsion Complex, Mahendragiri in Tamil Nadu on 7th November 2025, for a duration of 10 seconds.
A multi-element igniter was employed in both the thrust chamber and gas generator to facilitate boot-strap starting.
In this test, following the ignition of the thrust chamber, the gas generator was ignited under tank head conditions, and the turbopumps were started without the use of the start-up system.
Subsequently, the boot-strap mode build-up and steady-state operation of the engine were successfully demonstrated, ISRO said.