Context

In a quest to launch satellites in predetermined orbits at a low cost, India has crossed a key milestone by successfully conducting a hot test for its scramjet’s engine.

Details:

• ISRO has conducted a hot test for its air-breathing scramjet engine.
  • A hot test system is a 100% production test used to check all the engine operating parameters as they would function in real time.
• The test was conducted at its Propulsion Research Complexat Mahendragiri in the Tirunelveli district of Tamil Nadu.
• The test lasted for 11 seconds.
  

What is a scramjet engine?

• A scramjet engine is an improvement over the ramjet engine.
• India is the fourth country to demonstrate the flight testing of a Scramjet Engine.
• Thus, it is known as Supersonic Combustion Ramjet or Scramjet.
• In scramjet engines, the combustion takes place in supersonic airflow.
• Such engines use oxygen from the atmosphere in the combustion of fuel.

The scramjet advantages:

• Scramjet engine draws oxygen from the atmosphere:
  • It results in significant savings in terms of the weight of the oxidizer that does not have to be carried onboard.
  • These savings directly translate to higher payload capacity, and/or extended flight rangefor the vehicle.
• Vehicles can be cruised in a controlled manner:
  • Scramjets allow for a certain level of on-demand accelerationand deceleration by regulating the fuel burn rate, enabling improved control.
• Difficult to intercept: Enhanced level of manoeuvrability of a scramjet-powered hypersonic vehicle adds to the degree of unpredictability of its flight path, making interception much harder than for a ballistic missile.

The main types of Jet engines based on how air is compressed in the engine are:

• Turbo Jet: Turbo jet engine is an air-breathing jet engine. This is one of the most common types of jet engines. It is still widely used in aeroplanes.
• Ramjet: High-speed forward motion is used to compress the air (no compressor). Fuel is injected into the combustion chamber where it mixes with the hot compressed air and ignites.
  • The average speed of a Ramjet is 3-6 Mach.
  • But the ramjet efficiency starts to drop when the vehicle reaches hypersonic speeds.
  • Missiles and other flight systems designed for supersonic speeds (above Mach 1 and below Mach 5) commonly use a ramjet engine.
• Scramjet: Here also, the high-speed forward motion is used to compress the air (no compressor).
  • It is an improvement over the ramjet engine as it efficiently operates at hypersonic speeds and allows supersonic combustion.
  • Speed is greater than 6 Mach (Six times the speed of Sound).