---
title: "Cryogenic Upper Stage (CUS): ISRO Explained | Model Diplomat"
description: "A Cryogenic Upper Stage (CUS) uses liquid hydrogen and oxygen for efficient thrust, crucial for high-performance satellite launches like GTO missions."
url: "https://modeldiplomat.com/learn/glossary/cryogenic-upper-stage"
---

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Model Diplomat Research Team · Last reviewed June 22, 2026

TL;DR

- A cryogenic upper stage is a rocket stage that burns liquid hydrogen and liquid oxygen stored at extremely low temperatures to deliver high-efficiency thrust during the final phase of ascent.
- Why is liquid hydrogen and oxygen preferred for upper stages despite the handling difficulty?
- How does ISRO's CE-7.5 engine differ from the CE-20?
- What is the difference between a cryogenic and a semi-cryogenic stage?
- Why was India's cryogenic programme delayed in the 1990s?

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

A cryogenic upper stage is a rocket stage that burns liquid hydrogen and liquid oxygen stored at extremely low temperatures to deliver high-efficiency thrust during the final phase of ascent.

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ISRO's GSLV-D5 mission on 5 January 2014, launched from Sriharikota, was the first flight to successfully use a fully indigenous CE-7.5 cryogenic upper stage, ending India's dependence on imported cryogenic technology.

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