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Air Breathing Engines

  • 10 Dec 2022
  • 3 min read

Why in News?

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

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

What are Air Breathing Engines?

  • About:
    • An air-breathing engine is an engine that takes in air from its surroundings in order to burn fuel.
    • All practical air breathing engines are internal combustion engines that 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. The air is compressed, mixed with fuel, ignited and expelled as the exhaust gas.
    • Thrust produced by a typical air-breathing engine is about eight times greater than its weight.
      • The thrust results from the expulsion of the working gases from the exhaust nozzle.
  • Types:
    • Ramjet: A ramjet is a form of air-breathing jet engine that uses the vehicle’s forward motion to compress incoming air for combustion without a rotating compressor.
      • Ramjets work most efficiently 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 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 both in subsonic and supersonic combustion modes.
Speed Range Mach Number Velocity in m/s
Subsonic < 0.8 < 274
Transonic 0.8–1.2 274–412
Supersonic 1.2–5 412–1715
Hypersonic 5–10 1715–3430
High-hypersonic 10–25 3430–8507
  • Significance:
    • Air Breathing Engine provides a technological key for low-cost space transportation system.
    • The technology is an important step towards developing reusable launch vehicles.
    • Basically, of the total launch vehicle mass, 86% is propellant mass in the launch vehicle. Out of that propellant, 70% is oxidiser.
      • These engines can reduce nearly 70% of the propellent carried in the vehicles as these systems use atmospheric oxygen, which is available up to a height of 50km from the earth’s surface.

Source: TH

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