Cryogenic Rocket Engine

A cryogenic rocket engine is a rocket engine that uses a cryogenic fuel or oxidizer, that is, its fuel or oxidizers (or both) are gases liquefied and stored at very low temperatures. Due to use of liquid gases as propellants, the cryogenic Rocket Engines are also called liquid-propellant rocket engines.
The engine uses cryogenic propellants i.e., Liquid Hydrogen at -265° С as fuel and Liquid O2 at -240° С as oxidizer.
The major components of a cryogenic rocket engine are the combustion chamber (thrust chamber), pyrotechnic initiator, fuel injector, fuel cryopumps, oxidizer cryopumps, gas turbine, cryo valves, regulators, the fuel tanks, and rocket engine nozzle. In terms of feeding propellants to the combustion chamber, cryogenic rocket engines (or, generally, all liquid-propellant engines) are either pressure-fed or pump-fed, and pump-fed engines work in either a gas-generator cycle, a staged-combustion cycle, or an expander cycle.


• High Energy per unit mass: Propellants like oxygen and hydrogen in liquid form give very high amounts of energy per unit mass due to which the amount of fuel to be carried aboard the rockets decreases.
• Clean Fuels: Hydrogen and oxygen are extremely clean fuels. When they combine, they give out only water. This water is thrown out of the nozzle in form of very hot vapor. Thus the rocket is nothing but a high burning steam engine.
• Cryogenic rocket engines are much efficient than solid propellant based engines. They can deliver more thrust for a given mass of propellant.
• The cryogenics are also essential requirements for the manned space flight ISRO’s is planning to launch in the near future. The lower weight of the cryogenic propellants makes it possible to carry additional payloads to longer distance. Only the US, Russia, China, France and Japan have had this technology so far.


• The fuel tanks tend to be bulky and require heavy insulation to store the propellant. Their high fuel efficiency, however, outweighs this disadvantage.
• Despite non-toxic tendencies, cryogenic fuels are denser than air. As such, they can lead to asphyxiation.

Practice question:

Which of the following ISRO centres and their locations are correctly matched?
1. Liquid Propulsion Systems Centre – Vishakapatnam
2. Indian Institute of Remote Sensing - Dehradun
3. Satish Dhawan Space Centre – Sriharikota
4. National Remote Sensing Centre - Hyderabad


a) 1, 3 and 4

b) 2, 3 and 4

c) 1, 2 and 3

d) All

Ans: b
Exp: The Liquid Propulsion Systems Centre is a research and development centre functioning under Indian Space Research Organisation. It has two units located at Valiamala, in Thiruvananthapuram of Kerala, and Bengaluru of Karnataka. LPSC is augmented by ISRO Propulsion Complex at Mahendragiriof Tamil Nadu.