ScienceHow a Semi Cryogenic Engine works ?

How a Semi Cryogenic Engine works ?

  • “Russia is offering its semi-cryogenic rocket engine technology to India under the `Make-in-India’ programme. The rocket engines could be made in India and used in our rockets,” Sivan said.
  • In a recent statement, Russian state-run space corporation Roscosmos said the two countries will discuss cooperation in the sphere of piloted space flights, satellite navigation and engine technology.

ISRO Chairman

    ISRO Chairman K Sivan

Since the era of Soviet Union, Russia has been helping India in space programs. Space has been one of the key pillar of a historic strategic partnership between India and Russia. Now Russia is offering its Semi-Cryogenic technology to India under the ‘Make-in-India’ programme. ISRO is also working to make its own indigenous Semi Cryogenic engine which is schedule to be developed till 2021. But now if India accept  this offer from Russia, India may develop semi cryogenic engine within a year.

But How a semi cryogenic engine work. To understand the function and use of Semi Cryogenic Engine we first need to understand what is a Cryogenic Engine.

Cryogenic Engine.

Rocket engine needs enormous amount of thrust to escape Earth’s gravitational pull. However the chemicals used for engines are Hydrogen and Oxygen (Hydrogen used as a fuel, while Oxygen as a oxidiser) that produces a good thrust, found in Earth in the form of gas. Carrying hydrogen and oxygen in their gaseous form will require a bigger fuel chamber, which not only increase the size but also weight of the rockets and this will mean undertaking of impossible task to send a launch vehicle into space. So the solution is to use hydrogen and oxygen in their liquid form or in a cryogenic form which is easier to transport, as the volume of propellent decrease. As density increases in liquid form, more thrust can be produce in less burning time. Such engines are called Vryogenic engine.

Cryogenic fuel is used in rockets, spaceship or satellite because ordinary fuel can not be used in space due to the absent of an environment that support combustion. This fuel require storage at a extremely low temperature (-253 degree Celsius) to maintain them in a liquid state.

Semi-Cryogenic Engine.

Unlike a Cryogenic engine, a Semi Cryogenic engine use Refined kerosene instead of liquid hydrogen. The liquid oxygen used as a Oxidiser. That’s the advantage of using a Semi Cryogenic engine as it require Refined Kerosene which is lighter than liquid fuel and can be stored in a normal temperature. Kerosene combines with liquid oxygen provide a higher thrust to the rocket. Refined Kerosene occupies lesser space, making it possible to carry more propellent in a Semi Cryogenic engines fuel compartment. A semi cryogenic engine is more powerful, environment friendly and cost effective as compare to cryogenic engine.


GSLV (Geosynchronous Satellite launch Vehicle) uses a three stage launching system.

  • First Stage:- It is a solid stage which provide lift off to the rocket.
  • Second Stage:- It is a Liquid Stage.
  • Third Stage:- The third stage is the Cryogenic stage. This stage provide  a good amount of thrust so that we can put satellite in a geostationary orbit.

India developed the technology of Cryogenic Engine and to develop it further ISRO require to use a combination of Solid, Semi cryogenic and Cryogenic stage instead of a Combination of Solid, Liquid and Cryogenic stage. That  mean

  • First Stage:- Solid Stage.
  • Second Stage:- Semi Cryogenic Stage.
  • Third Stage:- Cryogenic Stage.

Using a semi cryogenic engine in second stage, GSLV will be able to provide more thrust and carry more weight into the space. India plan to use Semi Cryogenic Engine in GSLV (Geosynchronous Launch Vehicle), ULV (Unified Launch Vehicle) and  RLV (Reusable Launch Vehicle) in future.



Aditya Raj
Writer & Co-founder of InfotOnline.

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