---
title: "Cryogenic Engine: ISRO & GS3 Explained | Model Diplomat"
description: "A cryogenic engine burns liquid hydrogen and liquid oxygen at sub-zero temperatures for high efficiency. Key to ISRO's GSLV and a recurring UPSC GS3 topic."
url: "https://modeldiplomat.com/learn/glossary/cryogenic-engine"
---

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Model Diplomat Research Team · Last reviewed June 22, 2026

TL;DR

- A cryogenic engine is a rocket propulsion system that burns liquefied gases stored at extremely low temperatures, most commonly liquid hydrogen and liquid oxygen, to achieve high exhaust velocity.
- Why are cryogenic engines more efficient than solid or storable liquid engines?
- Why did India have to develop cryogenic technology indigenously?
- How does a cryogenic engine differ from a semi-cryogenic engine?
- What is 'methalox' and why is it gaining attention over hydrogen?

[Civil Service & Diplomatic Exams](https://modeldiplomat.com/learn/civil-services/glossary)Updated June 22, 2026

A cryogenic engine is a rocket propulsion system that burns liquefied gases stored at extremely low temperatures, most commonly liquid hydrogen and liquid oxygen, to achieve high exhaust velocity.

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ISRO's indigenously developed CE-7.5 cryogenic engine first powered the upper stage of the GSLV-D5 mission to a successful flight on 5 January 2014, ending years of dependence on imported cryogenic technology.

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