Scramjet Engine

Background

• Oxygen is as essential for the process of combustion as it is for the sustenance of life. Therefore a rocket, during its launch, needs to combine a combustion fuel with liquid oxygen to create the thrust needed for the take-off and flight.
• However, if the need for liquid oxygen is taken away (by producing air-breathing technology), the spacecraft can be much lighter, hence cheaper to launch.
• While conventional rocket engines need to carry both fuel and oxidizer on board for combustion to produce thrust, air-breathing rocket systems, on the other hand, uses the atmospheric oxygen from their surroundings and burn it with the stored on- board fuel.

 Ramjet, Scramjet and Dual Mode Ramjet (DMRJ) are the three concepts of air breathing engines which are being developed by various space agencies.

 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 around Mach 3 (three times the speed of sound) and can operate up to speeds of Mach 6. However, the ramjet efficiency starts to drop when the vehicle reaches hypersonic speeds.

 A dual mode ramjet (DMRJ) is a type of jet engine where a ramjet transforms into scramjet over Mach 4-8 range, which means it can efficiently operate both in subsonic and Supersonic combustor modes.

Scramjet engine

1. A scramjet engine is an improvement over the ramjet engine as it efficiently operates at hypersonic speeds and allows supersonic combustion. Thus it is known as Supersonic Combustion Ramjet, or Scramjet.

2. Scramjet engines obtain oxygen from the atmosphere by compressing the incoming air before combustion at hypersonic speed. It uses hydrogen as fuel and the oxygen from the atmospheric air as the oxidizer.

3. When the rocket reaches a height of 11 km, the scramjet engines would start breathing air directly from the atmosphere.

4. Scramjets are highly inefficient at low speeds. Their efficiency increases at supersonic speeds.

Significance

1. The spacecraft can be smaller or carry more payloads, making it a commercially viable option.

2. Scramjet technology effectively cuts down the cost of launching rockets by reducing its weight by more than half.

3. The engine, when fully developed, will eventually be used in Reusable Launch Vehicles or RLV’s.

4. India has become the fourth country to successfully test the scramjet engine after United States, Russia and the European Space Agency. ISRO carried out successful testing of scramjet engine from the Satish Dhawan Space Centre, Sriharikota. ISRO’s Advanced Technology Vehicle (ATV), which is an advanced sounding rocket, was the solid rocket booster used for this recent test of Scramjet engines at supersonic conditions. The space agency’s ATV rocket was able to fly at Mach 6 (six times the speed of sound) speeds.
   

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