ISRO successfully demonstrated boot-strap mode start test on the CE20 cryogenic engine in the High-Altitude Test (HAT) facility at ISRO Propulsion Complex, Mahendragiri on November 7, 2025.
| Photo Credit: Special Arrangement
The Indian Space Research Organisation (ISRO) has successfully demonstrated the boot-strap mode start test on the CE20 Cryogenic engine which powers the upper stage of the Launch Vehicle Mark -3 (LVM3) rocket.
The test on the CE20 cryogenic engine, which was successfully conducted under vacuum conditions in the High-Altitude Test (HAT) facility at ISRO Propulsion Complex, Mahendragiri on November 7, for a duration of 10 seconds is an important development towards enhancing the restart capability and mission flexibility of future LVM3 flights.
Though 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, and also for the Gaganyaan missions, during nominal operation, the engine ignition is initiated under tank head conditions, followed by the start of turbo pumps 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. 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,” ISRO stated.
During the test, 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 turbo pumps were started without the use of the start-up system. Subsequently, boot-strap mode build-up and steady-state operation of the engine were successfully demonstrated,” ISRO stated.
The space agency said that with this achievement, ISRO has successfully demonstrated boot-strap mode starting of a gas-generator cycle cryogenic engine without any auxiliary start-up system, perhaps for the first time in the world.
Published – November 19, 2025 04:04 pm IST
