CE-7.5
The CE-7.5 is an indigenous cryogenic rocket engine developed by the Indian Space Research Organisation (ISRO) under the Cryogenic Upper Stage Project (CUSP) to power the third stage of the Geosynchronous Satellite Launch Vehicle Mark II (GSLV Mk II).[1] It operates on a staged combustion cycle using liquid oxygen (LOX) as the oxidizer and liquid hydrogen (LH2) as the fuel, producing a nominal vacuum thrust of 75 kN with a specific impulse of 454 seconds in vacuum and a burn duration of 814 seconds.[1][2] The engine measures 2.14 meters in length and 1.56 meters in diameter, with a dry mass of 435 kg, enabling the GSLV Mk II to deliver payloads of up to 2,250 kg to geostationary transfer orbit (GTO).[2] Development of the CE-7.5 began in the late 1990s at ISRO's Liquid Propulsion Systems Centre (LPSC) in Valiamala, Thiruvananthapuram, following a technology transfer agreement with Russia's Glavkosmos that provided design specifications based on the RD-56 (KVD-1) engine used in earlier GSLV flights.[1][3] This collaboration allowed ISRO to indigenously manufacture the engine, incorporating modifications to suit GSLV requirements, such as enhanced restart capabilities and improved turbopump efficiency, after international sanctions had previously restricted cryogenic technology access.[3] The project overcame significant challenges, including a failure during the GSLV-D3 mission in 2010 due to ignition issues, before achieving full operational success.[2] The CE-7.5's debut on the GSLV-D5 mission on January 5, 2014, successfully placed the GSAT-14 communications satellite into orbit, demonstrating India's mastery of cryogenic propulsion and reducing dependence on foreign suppliers for upper-stage engines.[2] Since then, it has powered at least 13 GSLV Mk II launches as of 2025, including key missions like the 2016 deployment of the 2,211 kg INSAT-3DR satellite and the 2025 GSLV-F16/NISAR mission.[1][4][5] As ISRO's first operational cryogenic engine, the CE-7.5 remains a cornerstone of India's medium-lift launch capabilities, paving the way for advanced engines like the CE-20.[1]Design Features
Engine Cycle
The CE-7.5 rocket engine utilizes a staged combustion cycle to maximize efficiency in cryogenic propulsion, where a portion of the propellants is combusted in a preburner to drive the turbopumps before the remaining mixture enters the main combustion chamber.[1] This configuration enables higher chamber pressures and better performance compared to open-cycle alternatives, particularly suited for upper-stage applications in vacuum environments.[6] The cycle employs a fuel-rich preburner, which burns liquid hydrogen (LH2) and a limited amount of liquid oxygen (LOX) to generate hot gases that power the turbopump assembly. Propellants flow through low-pressure booster pumps that elevate the inlet pressure for the main turbopump, ensuring stable delivery of LOX as the oxidizer and LH2 as the fuel at a mixture ratio of 5.05:1 (oxidizer-to-fuel by mass); this ratio optimizes combustion completeness and specific impulse in the main chamber.[7] The turbopump is engineered to manage cryogenic fluid properties, incorporating inducer designs that provide sufficient net positive suction head to prevent cavitation during operation at low temperatures.[8] Integration of the preburner with the main chamber involves routing the fuel-rich turbine exhaust directly into the combustion zone, where it mixes with the remaining LOX and LH2 for full combustion, enhancing overall propellant utilization. The CE-7.5, derived from the Russian RD-56 engine, features improvements to the turbopump and startup sequence for reliable ignition in vacuum, following lessons from the 2010 GSLV-D3 mission.Cooling System
The CE-7.5 engine utilizes regenerative cooling to manage the intense thermal loads generated during operation, with liquid hydrogen (LH2) serving as the coolant circulated through integrated channels in the combustion chamber and nozzle walls to absorb and dissipate heat before injection into the combustion zone.[9] This approach leverages the cryogenic properties of LH2 to maintain structural integrity under high-temperature conditions, integrating with the staged combustion cycle to optimize propellant utilization.[1] The combustion chamber is fabricated from high-strength alloys to withstand extreme pressures and temperatures. To address overheating in the nozzle extension during extended burns of up to 814 seconds, the cooling system incorporates channels for the LH2, ensuring uniform heat transfer and preventing thermal hotspots along the extension's length.[1] The overall thermal performance of the system enables the engine to operate reliably at chamber pressures around 58 bar without structural failure or excessive wall temperatures, as demonstrated in qualification tests.[1]Thrust Vector Control
The thrust vector control (TVC) system of the CE-7.5 cryogenic engine utilizes a gimbaling mechanism to enable steering of the engine nozzle during ascent, providing attitude control for the Geosynchronous Satellite Launch Vehicle Mark II (GSLV Mk II) upper stage. This design allows the engine to pivot, directing the thrust vector to adjust the vehicle's pitch and yaw for trajectory corrections.[1] The gimbaling system supports deflection in two orthogonal planes, sufficient to manage the control requirements for the engine's nominal vacuum thrust of 75 kN while maintaining stability in the cryogenic environment.[1]Specifications
Performance Parameters
The CE-7.5 cryogenic engine delivers a nominal vacuum thrust of 75 kN, enabling efficient upper-stage propulsion for geosynchronous satellite launches.[1] This thrust level supports payload capacities up to 2.5 tonnes in geostationary transfer orbit, contributing to the overall performance of the GSLV Mk II launch vehicle.[1] The engine achieves a specific impulse of 454 seconds in vacuum, reflecting its high efficiency in converting propellant energy to thrust through the use of liquid oxygen and liquid hydrogen.[1] This metric underscores the engine's optimized design for vacuum operations, where minimal atmospheric interference allows for maximal exhaust expansion. Operating at a chamber pressure of 58 bar, the CE-7.5 maintains stable combustion within its staged combustion cycle.[1] The engine supports burn times of up to 814 seconds, providing extended operational duration for precise orbit insertion maneuvers.[1] These parameters collectively ensure reliable mission flexibility in upper-stage applications.| Parameter | Value | Conditions |
|---|---|---|
| Vacuum Thrust (Nominal) | 75 kN | Vacuum |
| Specific Impulse | 454 s | Vacuum |
| Chamber Pressure | 58 bar | Nominal |
| Maximum Burn Time | 814 s | Nominal mission |