Context:

The DRDO has recently achieved a significant milestone in the development of hypersonic missile technology by successfully demonstrating a cutting-edge Active Cooled Scramjet Combustor ground test for 120 seconds for the first time in India.

Key Developments of the Test

Successful Ground Test:

• DRDO conducted a groundbreaking "active cooled scramjet combustor ground test" for 120 seconds, marking a significant achievement in India's hypersonic missile development efforts.
• The test was carried out by the Defence Research and Development Laboratory (DRDL), a DRDO facility in Hyderabad.
• The DRDO's successful scramjet combustor test demonstrated stable combustion and ignition at speeds over 1.5 km per second, an essential requirement for hypersonic flight.

Innovative Flame Stabilization and Ignition Techniques:

• The DRDO-developed scramjet combustor incorporates advanced flame stabilization techniques to maintain continuous ignition even at hypersonic speeds.

Indigenous Scramjet Fuel Development:

• DRDL, in collaboration with industry partners, has developed an indigenous endothermic scramjet fuel that improves cooling and ignition capabilities for the scramjet engine.

Thermal Barrier Coating (TBC) Development:

• DRDO has also developed an advanced ceramic-based Thermal Barrier Coating (TBC) capable of withstanding the extreme temperatures encountered during hypersonic flight (operates beyond the melting point of steel).

Significance of the Test

• Stable combustion, enhanced performance, and advanced thermal management techniques demonstrated in the test position India as a leader in hypersonic missile development.
• The test results pave the way for the development of next-generation hypersonic missiles with superior capabilities. 

Related Previous Developments 

• HSTDV Flight Test: In September 2020, DRDO successfully flight-tested the ‘Hypersonic Technology Demonstrator Vehicle’ (HSTDV), which sustained hypersonic combustion for over 20 seconds at Mach 6 and successfully demonstrated the aerodynamic heat shield separation.

ISRO’s Scramjet Engine:

• The first experimental mission of ISRO’s Scramjet Engine towards the realisation of an Air Breathing Propulsion System was successfully conducted in August 2016 from Satish Dhawan Space Centre SHAR, Sriharikota.
• This test was the maiden short-duration experimental test of ISRO’s Scramjet engine with a hypersonic flight at Mach 6. 
• The Scramjet engine designed by ISRO uses Hydrogen as fuel and Oxygen from the atmospheric air as the oxidiser. 
• With this test, India became the fourth country to demonstrate the flight testing of a scramjet engine. 

About Air Breathing Technology

Today, satellites are launched into orbit by multi-staged satellite launch vehicles that can be used only once (expendable). 

Nearly 70% of the propellant (fuel-oxidiser combination) carried by today’s launch vehicles consists of oxidiser.

Therefore, countries worldwide are developing technology for air-breathing engines to bring down the launch cost. 

Air-breathing engines are propulsion systems that use oxygen from the air to burn fuel. Their work is as follows: - 

• Air-breathing engines take in air from the environment
• The air is compressed and mixed with fuel
• The fuel is ignited, which heats the air
• The hot gases expand and are expelled through a nozzle, creating thrust.

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

1. Ramjet - A ramjet is a form of air-breathing jet engine that operates by subsonic combustion of fuel in a stream of air compressed by the forward speed of the aircraft itself. A ramjet-powered vehicle requires an assisted take-off like a rocket assist to accelerate it to a speed where it begins to produce thrust.

2. Scramjet - A scramjet engine is an improvement over the ramjet engine as it efficiently operates at hypersonic speeds (above 5 Mach) and allows supersonic combustion throughout the flight. Thus, it is known as Supersonic Combustion Ramjet or Scramjet. 

3. 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 combustor modes. 

Advantages of Scramjet Technology

• An air-breathing scramjet engine burns oxygen scooped from the atmosphere as opposed to rocket engines which carry their own oxygen for combustion. This allows them to carry more cargo/payload than equivalent rocket-powered systems. 
• Scramjet engines are lighter than traditional jet engines because they don't have a compressor or turbine. 
• Scramjet engines don't have any moving parts, which makes them simpler and reduces the chance of mechanical failure. 
• Scramjet engines are more fuel-efficient than traditional jet engines.