What is a Cryogenic Rocket Engine?

“Cryos” is a Greek word meaning Ice Cold. The Cryogenics is the study of producing extremely low temperatures. Cryogenic rocket engine uses a cryogenic fuel. A cryogenic fuel or oxidizer includes the gases liquefied at a very low temperature. Due to use of liquid gases as propellants, the cryogenic Rocket Engines are also called liquid-propellant rocket engines.

The gases in liquid state occupy less space and provide required mass flow rate more efficiently than using the same in gaseous state.
The CE-20 is the first Indian cryogenic engine (but not indigenous) to feature a gas-generator cycle. It has been developed at Liquid Propulsion Systems Centre (LPSC), in Thiruvananthapuram, Kerala. LPSC is the research centre and rocket engine test facility of ISRO. LPSC has played a leading role in development of liquid propellant stages for PSLV, control systems for SLV-3, ASLV, PSLV and GSLV, satellite propulsion systems including those for INSAT and IRS and production of pressure transducers. India’s indigenous cryogenic upper stage for Geosynchronous Satellite Launch Vehicle (GSLV) which was successfully test fired by ISRO on August 4, 2007, was also developed by LPSC.
CE-7.5 is another cryogenic rocket engine developed by ISRO to power the upper stage of its Geosynchronous Satellite Launch Vehicle.
At present only five countries viz. United States, Russia, France, Japan and China have the cryogenic engine upper stage technology to launch heavier satellites in geostationary orbit. India is the sixth country to design and develop the cryogenic technology.
This GSLV- D3 is advanced version of the GSLV and is a three-stage rocket with solid, liquid and cryogenic stages. GSLV-D3 is to use indigenous cryogenic engine. Our country’s effort at joining the elite club these nations with indigenous cryogenic fuel technology failed on April 15, 2010 when the geo-synchronous satellite launch vehicle (GSLV-D3) carrying the geo-stationary experimental satellite (GSAT-4) ‘deviated’ from its path and mission was declared unsuccessful.