Maarg Manthan · Topic 12.20

GSLV Engine Variants and Cryogenic Rocket Technology

Science & Technology › Space Technology and ISRO · Topic 12.20

The Geosynchronous Satellite Launch Vehicle has flown in three major versions that differ mainly in the upper stage. GSLV Mk I used a Russian cryogenic stage, GSLV Mk II uses an indigenous cryogenic upper stage with the CE-7.5 engine of about 73 kilonewtons thrust, and GSLV Mk III, later called LVM3, uses the larger CE-20 engine of about 200 kilonewtons. Cryogenic rocket technology burns liquid hydrogen with liquid oxygen, which must be stored at about minus 253 and minus 183 degrees Celsius, and the engines need turbopumps, insulated tanks and precise control. Semi-cryogenic engines, such as the planned SCE-200, burn refined kerosene with liquid oxygen and provide high thrust from fuel that is easier to store.

5 min read · UPSC Prelims · Science & Technology · Space Technology and ISRO

At a Glance

Mk I Russian cryogenic stage
Mk II CE-7.5, about 73 kN
LVM3 CE-20, about 200 kN
Semi-cryogenic SCE-200 in development
Cryogenic fuels Liquid hydrogen and oxygen
Exam link UPSC Prelims, Science & Technology: Space Technology and ISRO

Where Does It Fit?

This topic follows the earth observation details. It returns to launch technology to compare the versions of the GSLV and the engines inside them, which were built over more than two decades. Previous topic: Earth Observation Systems and INSAT/GSAT/IRS Applications in Detail. Next topic: Multi Application Solar Telescope and Resourcesat-2A.

What Are the Variants of GSLV and Their Engines?

Version	Features
GSLV Mk I (D1 and D2, F01 to F06)	First flight in 2001. The third stage was a Russian cryogenic stage with the KVD-1 engine. Flew until 2010 with a mixed record that included failures
GSLV Mk II	Indigenous Cryogenic Upper Stage (CUS) with CE-7.5 engine. Liquid second stage with Vikas engine and first stage solid core with four liquid strap-ons. Height about 49 m, lift-off mass about 414 tonnes, capacity about 2,500 kg to geosynchronous transfer orbit
GSLV Mk III / LVM3	Solid S200 boosters, liquid L110 core with two Vikas engines, and C25 cryogenic upper stage with CE-20 engine carrying about 25 tonnes of propellant. Capacity about 4,000 kg to geosynchronous transfer orbit and about 8,000 kg to low Earth orbit
CE-7.5	Indigenous cryogenic engine, staged combustion cycle, thrust about 73 kN, flew successfully on GSLV-D5 in January 2014
CE-20	Indigenous cryogenic engine with gas generator cycle and thrust of about 186 to 200 kN, first used on LVM3-D1 in 2017 and for Chandrayaan-3
Vikas	Liquid engine using storable propellants (UH25 and nitrogen tetroxide) in all Indian liquid stages
Semi-cryogenic SCE-200	Engine of about 2,000 kN using liquid oxygen and refined kerosene, planned to upgrade the LVM3 first stage and for future heavy rockets

Why Is Cryogenic Technology Difficult and Useful?

Cold materials: components must keep strength and flexibility at minus 253 degrees Celsius
Insulation: tanks need insulation to keep liquid hydrogen from boiling away
Turbopumps: pumps must spin at tens of thousands of revolutions per minute while handling extremely cold liquids
Ignition: repeated and precise ignition in space is needed for the upper stage
Seals and valves: leaks of hydrogen are dangerous because it is flammable
Gas generator and staged combustion: two main designs of engine cycle, with the second giving higher efficiency
Higher payload: an upper stage with cryogenic engine lifts a much larger payload than one with storable propellant
Reusability: cryogenic upper stages can be restarted, which is useful for placing satellites in precise orbits

What Else Should You Remember?

Tank sizes: LVM3’s C25 stage has about 25 tonnes of propellant, compared with about 12.5 tonnes in the CUS of GSLV Mk II
Specific impulse: cryogenic stages give about 450 seconds against about 280 seconds for solid stages
Hydrogen density: liquid hydrogen is very light, so tanks are large and insulated
Oxygen at minus 183: liquid oxygen is much easier to handle than liquid hydrogen
Cryogenic test facility: engines are tested at the ISRO Propulsion Complex at Mahendragiri in Tamil Nadu
Liquid Propulsion Systems Centre: develops liquid and cryogenic engines
Manufacturers: Indian industry such as Godrej, L&T and HAL make tanks and parts
Failures: GSLV-D3 in April 2010 failed when the indigenous cryogenic stage did not ignite properly, leading to improvements before GSLV-D5 succeeded
Mk III first flight: the experimental flight of GSLV Mk III in December 2014 carried a crew module test with a passive cryogenic stage
Human rating: the human-rated LVM3 will launch Gaganyaan crew
Other cryogenic engines: the RD-0146 of Russia, RL-10 of the US, Vulcain of Europe and LE-5 of Japan
Link: the basics are in Launch Vehicle Technology: PSLV, GSLV and Cryogenic Engines

Why Does It Matter for the Exam?

Engines and thrust: CE-7.5 and CE-20
Versions: Mk I to Mk III
Fuel pairs: cryogenic versus semi-cryogenic
Current affairs link: SCE-200 tests and Gaganyaan rocket
Common errors: mixing Vikas and cryogenic engines, or saying that LVM3 uses CE-7.5

As an analytical point, India’s cryogenic engines took two decades, but now give a base for heavier launchers. The SCE-200 and reusable stages are the next steps toward higher lift and lower cost.

Why Is This Topic Important?

Versions Mk I, II, III
Engines CE-7.5, CE-20
Next Semi-cryogenic

What Came Next?

The next topic covers India’s Multi Application Solar Telescope and the satellite Resourcesat-2A. Next topic: Multi Application Solar Telescope and Resourcesat-2A.

Key People and Terms

CUS Cryogenic upper stage
CE-20 Cryogenic engine for LVM3
Vikas Liquid engine
Gas generator cycle Simpler engine cycle
Staged combustion Higher efficiency cycle
SCE-200 Semi-cryogenic engine

Exam Corner

Points to Remember

CE-7.5: about 73 kN.
CE-20: about 200 kN.
GSLV-D5: January 2014.
GSLV-D3 failure: April 2010.
SCE-200: about 2,000 kN.

Do Not Confuse With

CE-7.5 and CE-20 Smaller GSLV Mk II engine versus LVM3 engine
Cryogenic and semi-cryogenic Hydrogen versus kerosene fuel
GSLV Mk II and Mk III Smaller versus larger rocket

Memory Hook

Seven-and-a-half for Mark Two, twenty for Mark Three; kerosene and oxygen come next.

Mains Angle

Questions ask about versions, engine numbers and difficulty. These points help.

Journey Mk I to LVM3
Difficulty Cold technology
Next Semi-cryogenic

A Question You May Face

An original practice question, not a past paper question.

“Trace the development of India’s cryogenic engines and the variants of GSLV, and discuss their importance for heavy satellite launches.”

How to Answer

Versions Mk I to III.
Engines CE-7.5, CE-20.
Importance Heavy satellites.
Way SCE-200.

GS Relevance

Prelims: GSLV versions, engine names and thrust, cryogenic fuels, semi-cryogenic. GS Paper 3: science and technology, space, indigenisation.

Frequently Asked Questions

What are the versions of GSLV?

GSLV Mk I used a Russian cryogenic upper stage, GSLV Mk II uses an indigenous cryogenic stage with the CE-7.5 engine and carries about 2,500 kilograms to geosynchronous transfer orbit, and GSLV Mk III, now called LVM3, uses the larger CE-20 engine and carries about 4,000 kilograms to that orbit.

What is the thrust of the CE-20 engine?

The CE-20 is India's indigenous cryogenic engine for the upper stage of LVM3, with a thrust of about 200 kilonewtons, burning liquid hydrogen and liquid oxygen. It carries about 25 tonnes of propellant in the C25 stage and was used for Chandrayaan-3, and will be used in the Gaganyaan human spaceflight programme.

What is a semi-cryogenic engine?

A semi-cryogenic engine burns refined kerosene with liquid oxygen, so only the oxidiser is cryogenic. It gives high thrust with fuel that is cheaper and easier to store than liquid hydrogen. ISRO is developing the SCE-200 engine of about 2,000 kilonewtons thrust to power future launch vehicles and upgrade LVM3.

Why did GSLV-D3 fail?

GSLV-D3, launched in April 2010 with the first indigenous cryogenic stage, failed because the fuel booster turbo pump of the cryogenic engine stopped working, so the stage did not ignite as intended. ISRO studied the failure, made design changes and retested, which led to the success of GSLV-D5 in January 2014.

Where are Indian rocket engines tested?

Liquid and cryogenic rocket engines are tested at the ISRO Propulsion Complex at Mahendragiri in Tamil Nadu, which has test stands for the Vikas, cryogenic and semi-cryogenic engines. The Liquid Propulsion Systems Centre, with units at Valiamala in Kerala and Bengaluru, designs and develops these engines.

PYQ Practice — Statement Analysis

1 The CE-7.5 engine powers the upper stage of GSLV Mk II.

True

An indigenous cryogenic engine.

2 LVM3 uses the CE-7.5 cryogenic engine.

False

It uses CE-20.

3 A semi-cryogenic engine uses liquid hydrogen as fuel.