The upper stage of GSLV MkIII the next generation and the most powerful launch vehicle of ISRO is powered by a cryogenic engine called CE-20. This engine produces a nominal thrust of 200 kN, but has an operating thrust range between 180 kN to 220 kN and can be set to any fixed values between them.The engine is first of its kind that works in gas generator cycle and indigenously developed. The combustion chamber burns liquid hydrogen and liquid oxygen at 6 MPa with 5.05 engine mixture ratio. The engine has a thrust-to-weight ratio of 34.7 and a specific impulse of 443 seconds in vacuum. ISRO successfully tested the sea level version of the engine for a cumulative duration of about 1900 s spread over ten hot tests which includes flight duration hot test of 635s on April 28, 2015 and endurance hot test for duration of 800 seconds. This engine generates nearly 2 MW power as compared to 1 MW generated by the engine of the earlier Cryogenic Upper Stage (CUS) engine of GSLV. The high thrust cryogenic engine is one of the most powerful cryogenic upper stage engines in the world.

CE-20 engine works on “Gas Generator Cycle” which has flexibility for independent development of each sub-system before the integrated engine test, thus minimising uncertainty in the final developmental phase with reduced development time. The high thrust cryogenic engine is one of the most powerful upper stage cryogenic engines in the world. Starting with injector element development for configuration of injector head, the design, realisation and testing of the major subsystems viz the gas generator, turbo pumps, start-up system and thrust chamber, have been successfully completed in a phased manner before conducting a series of developmental tests in the integrated engine mode. Apart from the major sub-systems, many critical components like the igniter,
control components etc were independently developed and qualified.

The major subsystems of the engine are thrust chamber, gas generator, LOX and LH2 turbo pumps, igniters, thrust & mixture ratio control systems, Start-up system, control components and pyro valves which were are developed indigenously by ISRO. The fifth hardware of CE-20 integrated engine designated as E6 is earmarked for GSLV Mk-III M1-Chandrayaan 2 mission.

The high thrust cryogenic engine is designed and realised by Liquid Propulsion Systems Centre. The engine assembly, integration and testing is carried out by ISRO Propulsion Complex (IPRC) at Mahendragiri. Indian Industries have significantly contributed in the realisation of the cryogenic engine.