Launch Vehicle Technology: PSLV, GSLV and Cryogenic Engines
Science & Technology › Space Technology and ISRO · Topic 12.5
The Polar Satellite Launch Vehicle, PSLV, is the workhorse rocket of India. It has four stages, alternately solid and liquid, and first flew successfully in 1994 after a failed first attempt in 1993. PSLV launched Chandrayaan-1, the Mars Orbiter Mission and Astrosat, and in February 2017 it put 104 satellites into orbit in one flight, a record at that time. The Geosynchronous Satellite Launch Vehicle, GSLV, was built to place heavier satellites into geosynchronous transfer orbit and its upper stage uses a cryogenic engine, which burns liquid hydrogen and liquid oxygen kept at very low temperatures. India flew its first indigenous cryogenic stage successfully in January 2014 on GSLV-D5.
5 min read · UPSC Prelims · Science & Technology · Space Technology and ISRO
At a Glance
- PSLV stages Solid, liquid, solid, liquid
- Record 104 satellites, February 2017
- GSLV upper stage Cryogenic
- First indigenous cryogenic flight GSLV-D5, January 2014
- Cryo fuel Liquid hydrogen and oxygen
- Exam link UPSC Prelims, Science & Technology: Space Technology and ISRO
Where Does It Fit?
This topic follows the account of satellite systems. After knowing what India launches, the macro now explains the launchers that carry the satellites and the cryogenic technology that took long to master. Previous topic: Satellite Systems: INSAT, GSAT, IRS (Remote Sensing). Next topic: Navigation Satellite Systems: GPS, Galileo, GLONASS, NavIC (IRNSS), GAGAN.
What Are the Features of PSLV and GSLV?
| Item | PSLV and GSLV details |
|---|---|
| PSLV stage 1 | Solid propellant (HTPB) core with six strap-on boosters in some versions |
| PSLV stage 2 | Liquid stage using Vikas engine with unsymmetrical dimethylhydrazine and nitrogen tetroxide |
| PSLV stage 3 | Solid rocket motor |
| PSLV stage 4 | Liquid stage with two small engines using monomethylhydrazine and mixed oxides of nitrogen |
| PSLV variants | Standard, Core Alone (PSLV-CA), XL with larger boosters and QL with four boosters |
| GSLV Mk II stages | Solid first stage with four liquid strap-ons, a liquid second stage, and a cryogenic third stage |
| Records and uses | PSLV: Chandrayaan-1, Mangalyaan and many foreign satellites. GSLV: GSAT, NVS and NISAR missions |
What Is Special About Cryogenic Engines?
- Cryogenic propellants: liquid hydrogen at about minus 253 degrees Celsius and liquid oxygen at about minus 183 degrees, kept liquid in insulated tanks
- Why cryogenic: hydrogen and oxygen give a specific impulse of about 450 seconds, much higher than about 280 seconds for solid or storable liquid fuels, so the upper stage lifts more mass
- Technical difficulty: very low temperatures, special materials, turbopumps that run at high speed and precise ignition
- Russian cryogenic stages: the first GSLV flights from 2001 used Russian KVD-1 cryogenic stages
- Technology denial: in the early 1990s the United States objected to a Russian transfer of cryogenic technology under the Missile Technology Control Regime, and India developed its own
- CE-7.5: the first indigenous cryogenic engine of about 73 kilonewtons thrust in the GSLV Mk II upper stage
- CE-20: a larger cryogenic engine of about 200 kilonewtons for the upper stage of LVM3
- GSLV-D5: launched GSAT-14 on 5 January 2014, the first success with an indigenous cryogenic stage, after a failure in 2010
What Else Should You Remember?
- Vikas engine: a liquid engine named after Vikram Sarabhai, used in the second stage of PSLV and the core of GSLV and LVM3. Derived from the French Viking design
- Thrust and mass: PSLV stands about 44 metres high and weighs about 320 tonnes at lift off, and GSLV Mk II about 49 metres and 414 tonnes
- PSLV failures: the first flight in 1993 failed, and later failures include PSLV-C39 in 2017 and PSLV-C61 in May 2025. Check the latest status of the PSLV flight record
- PSLV record flight: PSLV-C37 launched 104 satellites on 15 February 2017, 101 of them foreign
- PSLV-C25: launched the Mars Orbiter Mission in November 2013
- Staged combustion: engines that burn exhaust of a pre-burner in the main chamber to raise efficiency, used in advanced cryogenic engines
- Semi-cryogenic engine: ISRO is developing the SCE-200 using liquid oxygen and refined kerosene, with about 2,000 kilonewtons thrust, to raise LVM3 capacity
- Human rating: crewed rockets need extra reliability and escape systems
- Link with LVM3: CE-20 cryogenic upper stage powers the heavier launcher, as in GSLV Engine Variants and Cryogenic Rocket Technology
- Launch records: an NVS-03 satellite was launched on a GSLV from Sriharikota on 30 October 2026, as reported on 31 October, with a short turnaround between GSLV missions
- Private partners: industry builds many stages and propellant tanks for PSLV and GSLV
- Economic importance: reliable launch capability earns revenue from foreign customers and saves foreign exchange
Why Does It Matter for the Exam?
- PSLV facts: stage fuels and records
- Cryogenic: fuels, temperature, GSLV-D5
- Engines: Vikas, CE-7.5, CE-20
- Current affairs link: launch failures and records
- Common errors: saying that PSLV has a cryogenic stage or that GSLV-D5 used Russian engines
As an analytical point, mastering cryogenic engines gave India independence in launching heavy satellites. Reliable launch and a steady rate of flights are now the measure of success.
Why Is This Topic Important?
- PSLV Stages and records
- Cryogenic Fuel and difficulty
- History Technology denial
What Came Next?
The next topic covers navigation satellite systems of the world and India. Next topic: Navigation Satellite Systems: GPS, Galileo, GLONASS, NavIC (IRNSS), GAGAN.
Key People and Terms
- Cryogenic Very low temperature
- Specific impulse Fuel efficiency of engine
- Strap-on Booster attached to core
- Turbopump Pump driven by turbine
- HTPB Solid fuel binder
- MTCR Missile Technology Control Regime
Exam Corner
Points to Remember
- PSLV has four stages, alternate solid and liquid.
- 104 satellites on 15 February 2017.
- GSLV-D5: January 2014.
- Liquid hydrogen: about minus 253 degrees.
- PSLV has no cryogenic stage.
Do Not Confuse With
- Cryogenic and semi-cryogenic Hydrogen and oxygen versus kerosene and oxygen
- Vikas and CE-20 Storable liquid engine versus cryogenic engine
- GSLV Mk II and LVM3 Smaller versus larger cryogenic vehicle
Memory Hook
Solid, liquid, solid, liquid goes PSLV; GSLV climbs with hydrogen cold as ice.
Mains Angle
Questions ask for stages, fuels and technology facts. These points help.
- Importance Self-reliance
- Challenge Cryogenic technology
- Way Reliability and frequency
A Question You May Face
An original practice question, not a past paper question.
“Discuss the significance of the Polar Satellite Launch Vehicle and indigenous cryogenic technology for India’s space programme.”
How to Answer
- PSLV Workhorse and records.
- Cryogenic Difficulty and success.
- Impact Heavy satellites.
- Way Reliability.
GS Relevance
Frequently Asked Questions
What are the stages of the PSLV?
The Polar Satellite Launch Vehicle has four stages that are alternately solid and liquid. The first and third stages use solid propellant, while the second and fourth use liquid propellant. Some versions add strap-on boosters to the first stage. It has no cryogenic stage, because it is designed for low Earth and sun-synchronous orbits.
What is a cryogenic engine?
A cryogenic engine is a rocket engine that burns propellants kept at extremely low temperatures, usually liquid hydrogen at about minus 253 degrees Celsius with liquid oxygen at about minus 183 degrees. It gives higher efficiency than other chemical fuels, so cryogenic stages are used in upper stages to lift heavier satellites to geostationary transfer orbit.
When did India first launch with an indigenous cryogenic engine?
India first flew an indigenous cryogenic upper stage successfully on 5 January 2014 on GSLV-D5, which placed the GSAT-14 satellite in orbit. An earlier attempt in April 2010 had failed. Before that, India had used Russian cryogenic stages on its first GSLV flights since 2001.
Why did India need to develop its own cryogenic technology?
In the early 1990s the United States objected to a transfer of cryogenic engine technology from Russia to India under the Missile Technology Control Regime, so only a few stages were supplied. This pushed ISRO to develop the technology on its own, leading to the CE-7.5 and CE-20 engines.
What was special about PSLV-C37?
PSLV-C37 launched on 15 February 2017 with 104 satellites in a single flight, which was a world record at that time. Of these, 101 were foreign nanosatellites, mostly from the United States, and the main payload was India's Cartosat-2D. It showed ISRO's strength in commercial small satellite launches.
PYQ Practice — Statement Analysis
1 The PSLV has a cryogenic upper stage.
It has solid and liquid stages only.
2 GSLV-D5 flew with an indigenous cryogenic stage in 2014.
Placing GSAT-14 in orbit.
3 PSLV-C37 launched 104 satellites in one flight.
In February 2017.
4 Liquid hydrogen is stored at about minus 253 degrees Celsius.
Which is why it is called cryogenic.
Past Mains Questions on This Topic
This topic comes under Space Technology and ISRO. UPSC Mains questions asked on the matching syllabus topic, year-wise with marks:
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