Air Breathing Engines

Topic- Space Technology [GS Paper-3]

Context- Recently, the Indian Space Research Organisation (ISRO) successfully conducted the hot test of Scramjet Engine, a type of Air Breathing Engine.

Key Highlights 

• India is the fourth country in the world to demonstrate the flight testing of a Scramjet Engine.

Air Breathing Engines

• An air-breathing engine is an engine which takes in air from its surroundings in order to burn fuel.
• All practical air breathing engines are internal combustion engines which directly heat the air by burning fuel, with the resultant hot gases used for propulsion via a propulsive nozzle.
• A continuous stream of air flows through the air-breathing engine. Then the air is compressed, mixed with fuel, ignited and expelled as the exhaust gas.
• Thrust produced by a typical air-breathing engine is around eight times greater than its weight.
• The thrust results from the expulsion of the working gases from the exhaust nozzle.

Types of Breathing Engines 

• Ramjet
  • A ramjet is a form of air-breathing jet engine which uses the vehicle’s forward motion to compress incoming air for combustion without a rotating compressor.
  • Ramjets work most effectively at supersonic speeds but they are not efficient at hypersonic speeds.
• Scramjet
  • A scramjet engine is an improvement over the ramjet engine as it efficiently operates at hypersonic speeds and also allows supersonic combustion.
• Dual Mode Ramjet (DMRJ) 
  • A dual mode ramjet (DMRJ) is a type of jet engine where a ramjet transforms into a scramjet over Mach 4-8 range, which means it can efficiently operate in subsonic as well as in  supersonic combustion modes.

Significance

• The Air Breathing Engine provides a technological key for low-cost space transportation systems.
• The technology is a significant step towards developing reusable launch vehicles.
• Generally, of the total launch vehicle mass, 86% is propellant mass in the launch vehicle. Out of that propellant, 70% is oxidiser.
• These engines are able to reduce nearly 70% of the propellant carried in the vehicles as these systems use atmospheric oxygen, which is available up to a height of 50km from the earth’s surface.

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