Description

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Context

ISRO successfully conducted a sea level hot test of its CE20 cryogenic engine at the ISRO Propulsion Complex in Mahendragiri, Tamil Nadu.

Highlights of the Sea Level Test

A Nozzle Protection System was employed to mitigate challenges associated with testing the CE20 engine at sea level. This approach reduces reliance on the High-Altitude Test (HAT) facility making testing more cost-effective and less complex.

The high area ratio nozzle (with an exit pressure of approximately 50 mbar) is prone to flow separation at sea level. Flow separation can cause severe vibrations, thermal problems and potential mechanical damage to the nozzle.

Significance of the Test

The Nozzle Protection System reduces the complexity and costs associated with testing at HAT facilities.

The engine has been qualified for thrust levels of:

19 tonnes(used in six LVM3 missions to date).
20 tonnesfor the Gaganyaan mission.
22 tonnesfor the C32 stage enabling enhanced payload capability for future launches.

The CE20 engine powers the upper stage of LVM3 (GSLV Mk III), India’s most powerful rocket which is central to:

Gaganyaan, India’s human spaceflight program.
Heavier payload launches and interplanetary missions.

CE-20 Cryogenic Engine

The CE-20 cryogenic engine is an indigenous cryogenic rocket engine developed by the Indian Space Research Organisation (ISRO). It is a pivotal component of India's GSLV Mk III also known as LVM-3 used for launching heavy payloads into geostationary orbits.

Cryogenic Technology

Cryogenic technology involves the use of extremely low temperatures typically below -150°C to liquefy gases such as oxygen and hydrogen for use as rocket propellants.

These propellants provide higher specific impulse making cryogenic engines more efficient compared to semi-cryogenic or solid rocket engines.

ISRO initiated the development of the CE-20 engine as part of its efforts to achieve self-reliance in cryogenic technology. It succeeded the Russian-supplied KVD-1 engine used in earlier GSLV launches.

The CE-20 engine was developed indigenously at ISRO's Liquid Propulsion Systems Centre (LPSC).

Specifications of the CE-20 Engine

Parameter	Details
Propellants	Liquid Oxygen (LOX) and Liquid Hydrogen (LH2)
Thrust	200 kN (kilonewtons)
Specific Impulse	442 seconds (in vacuum)
Combustion Cycle	Gas Generator Cycle. The engine burns a small amount of fuel in a separate gas generator to drive turbines which power the fuel and oxidizer pumps.
Burn Time	Approximately 640 seconds
Engine Mass	587 kg
Cooling System	Regenerative Cooling. Liquid hydrogen flows through channels in the nozzle to absorb heat preventing overheating and increasing efficiency.

Significance

Powers the GSLV Mk III India's most powerful rocket capable of lifting up to 4,000 kg into geostationary orbit and 10,000 kg into low Earth orbit (LEO).

The engine has played a crucial role in missions like Chandrayaan-2 and is set to support Gaganyaan India’s first crewed space mission.

Major Achievements

Maiden Flight: Successfully used in the GSLV Mk III-D1 mission in December 2014.

Chandrayaan-2: Enabled the launch of the lunar mission in July 2019 demonstrating its efficiency and reliability.

Commercial Launches: Strengthened ISRO’s position in launching foreign satellites under Antrix Corporation, ISRO’s commercial arm.

Global Comparison

Country	Engine	Thrust	Specific Impulse	Propellant
India	CE-20	200 kN	442 seconds	LOX + LH2
USA	RL10 (ULA)	110-160 kN	464 seconds	LOX + LH2
Russia	RD-0120	1,962 kN	455 seconds	LOX + LH2
Europe	Vinci (Ariane)	180 kN	465 seconds	LOX + LH2
China	YF-77	500 kN	430 seconds	LOX + LH2

Types of Rocket Engines

Type	Sub-Types	Working Principle	Advantages	Disadvantages	Applications
Chemical Rocket Engines	Solid Propellant Engines Liquid Propellant Engines Hybrid Propellant Engines	Converts chemical energy of propellants into high-pressure and high-temperature gases, expelled through a nozzle.	High thrust-to-weight ratio Well-established technology	Limited specific impulse Requires large amounts of propellant	Launch vehicles Missiles Spacecraft maneuvers
Electric Rocket Engines	Ion Thrusters Hall Effect Thrusters Arcjet Engines	Uses electric energy to accelerate ions or plasma to produce thrust.	High specific impulse Efficient in space	Low thrust Requires continuous power supply	Satellite station-keeping Deep-space missions
Nuclear Rocket Engines	Nuclear Thermal Rockets Nuclear Electric Rockets	Uses nuclear reactions (fission or fusion) to generate heat, which propels a working fluid.	Extremely high specific impulse Potential for long-term missions	Complex and expensive Concerns over radiation safety	Deep-space exploration Manned missions to Mars
Thermal Rocket Engines	Solar Thermal Rockets Microwave Thermal Rockets	Uses external heat sources (like solar or microwave energy) to heat a working fluid, which expands to produce thrust.	Eliminates need for onboard oxidizer Reduces propellant mass	Limited by external heat availability Low thrust compared to chemical engines	Orbital transfers Space tugs
Hybrid Rocket Engines	Combines solid and liquid propellants	Combustion occurs with solid fuel and a liquid oxidizer, enabling better control.	Simpler than liquid engines Higher performance than solid engines	Limited thrust variation Combustion complexity	Suborbital launches Experimental missions
Cold Gas Thrusters	Uses compressed inert gas for propulsion	Expels gas stored at high pressure through a nozzle to generate thrust.	Simple design Reliable	Very low thrust Inefficient for large payloads	Attitude control of satellites Small spacecraft
Aerospike Engines	Linear or toroidal aerospike nozzles	Adjusts thrust vector and pressure dynamically based on atmospheric density.	High efficiency at varying altitudes Reduced mass	Complex cooling system Requires advanced materials	Reusable launch vehicles Advanced spacecraft designs
Ramjet and Scramjet Engines	Air-breathing engines for hypersonic speeds	Uses atmospheric air as oxidizer; fuel is combusted in the airflow.	No onboard oxidizer needed Lightweight for high-speed applications	Cannot operate at low speeds Requires advanced materials for thermal protection	Hypersonic missiles High-speed aircraft
Plasma Rocket Engines	VASIMR (Variable Specific Impulse Magnetoplasma Rocket)	Ionizes gas into plasma and uses electromagnetic fields to accelerate it.	High specific impulse Can vary thrust and efficiency	High energy consumption Requires advanced cooling systems	Long-term space missions Interplanetary travel

Performance Metrics

Specific Impulse indicates efficiency measured in seconds. Electric engines have higher specific impulse than chemical engines but produce lower thrust.

Thrust-to-Weight Ratio: Chemical engines provide high thrust for takeoff while electric and plasma engines are suitable for space applications requiring prolonged thrust.

Sources:

HINDU

PRACTICE QUESTION

Q.Consider the following statements about rocket engines:

Solid rocket engines are simpler in design and can be stored for long durations.
Liquid rocket engines can be throttled, stopped and restarted.
Hybrid rocket engines use a combination of liquid fuel and a solid oxidizer.

Which of the above statements is/are correct?
a) 1 and 2 only
b) 2 and 3 only
c) 1 and 3 only
d) 1, 2, and 3

Answer: d)

Explanation:

Statement 1 is correct. Solid rocket engines are simpler, cost-effective and can remain in storage for extended periods without degradation.

Statement 2 is correct. Liquid rocket engines offer better control over thrust and can be throttled, stopped or restarted.

Statement 3 is correct. Hybrid rocket engines use solid fuel and liquid oxidizers combining benefits of both solid and liquid engines.