Isro Successfully Demonstrates Bootstrap Start of CE20 Cryogenic Engine
For future missions, multiple in-flight restarts of the CE20 engine will be required for mission flexibility towards multi-orbit missions.
Nellore: Isro’s CE20 cryogenic engine powering the LVM3 upper stage has qualified for operation at thrust levels ranging from 19 tonnes to 22 tonnes in flight with a single start. The engine thus qualifies for the Gaganyaan missions.
The engine ignition had been initiated under tank head conditions, followed by 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.
Under the existing 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 operation builds steadily without external start-up assistance, is essential.
Isro demonstrated this capability with the bootstrap mode start test on the CE20 Cryogenic engine conducted successfully for 10 seconds under vacuum conditions at the High-Altitude Test (HAT) facility at the Isro Propulsion Complex at Mahendragiri on November 7, 2025.
A multi-element igniter had been employed in both the thrust chamber and gas generator to facilitate bootstrap starting. Following the ignition of the thrust chamber, the gas generator ignited under tank head conditions. The turbopumps started without the use of the start-up system.
Subsequently, ISRO successfully demonstrated the bootstrap mode build-up and steady-state operation of the engine.
With this achievement, ISRO has successfully demonstrated bootstrap mode starting of a gas-generator cycle cryogenic engine without any auxiliary start-up system, perhaps for the first time in the world. This is a significant milestone towards enhancing the restart capability and mission flexibility of future LVM3 flights.
