Recently, the Defence Research and Development Organisation (DRDO) successfully conducted ground testing of a full-scale, actively cooled, long-duration Scramjet engine as part of India’s Hypersonic Missile Programme. This marks a major milestone in India’s indigenous hypersonic technology capabilities.

What is a Scramjet Engine?

A Scramjet (Supersonic Combustion Ramjet) is an air-breathing engine designed to operate efficiently at hypersonic speeds (Mach 5 and above). Unlike conventional jet engines, scramjets do not use rotating compressors or turbines, relying instead on the vehicle’s high forward speed to compress incoming air.

Key Features of a Scramjet Engine

• Scramjets allow supersonic combustion, where fuel burns while the airflow remains supersonic.

• They are particularly suited for Hypersonic Cruise Missiles (HCMs).

• The engine uses liquid hydrogen as fuel and liquid oxygen as an oxidiser to generate thrust.

• Scramjet engines offer significantly higher fuel efficiency compared to turbojets and ramjets at hypersonic speeds.

• Rocket-assisted take-off is required, as scramjets cannot generate thrust at zero or low speeds.

India’s Achievement in Scramjet Technology

With this successful testing, India has become the fourth country in the world to demonstrate flight-tested scramjet engine technology, underscoring its growing capabilities in advanced defence and aerospace systems.

Working Principle of a Scramjet Engine

Air Intake

The vehicle must already be flying at supersonic speed (Mach 3 or higher) for the scramjet to function.

Air Compression

The extremely high speed of the vehicle compresses the incoming air naturally, without the need for mechanical compressors.

Supersonic Combustion

Hydrogen fuel is injected and ignited, while the airflow remains supersonic, which is the defining feature of a scramjet.

Thrust Generation

The rapid expansion of hot gases produces thrust, following Newton’s Third Law of Motion.

What are Hypersonic Missiles?

Hypersonic missiles are those that travel at speeds greater than Mach 5, which is more than five times the speed of sound (approximately 330 m/s).

Types of Hypersonic Missiles

Hypersonic Glide Vehicles (HGVs)

These missiles are:

• Launched using a rocket booster, similar to ballistic missiles,

• Released at high altitude, and

• Glide unpowered towards the target at hypersonic speeds, making them difficult to intercept.

Hypersonic Cruise Missiles (HCMs)

These missiles:

• Are powered throughout their flight by air-breathing scramjet engines,

• Maintain sustained hypersonic speeds, and

• Offer greater manoeuvrability and precision compared to ballistic missiles.

Strategic Significance of Scramjet Technology

Scramjet engines significantly enhance India’s strategic deterrence by enabling:

• Faster strike capabilities,

• Improved penetration of missile defence systems, and

• Advancement towards self-reliance in critical defence technologies under Atmanirbhar Bharat.

Conclusion

The successful testing of the scramjet engine by DRDO represents a major technological breakthrough for India. It strengthens the country’s position in the global hypersonic race and enhances its long-term defence preparedness through indigenous, cutting-edge propulsion technology.

Scramjet Engine

The Hot Test of the Scramjet Engine was just successfully completed by the Indian Space Research Organization (ISRO).

What is Scramjet Engine?

• A scramjet, also known as a supersonic-combustion ramjet, is a type of ramjet engine where the airflow remains supersonic, or faster than the speed of sound.
• A scramjet lacks a shock cone and instead slows the airflow utilising shockwaves generated by its ignition source.
• As a result, the scramjet can run efficiently at very high speeds.
• Vehicles powered by scramjets are expected to travel at least as fast as Mach 15.

Air Breathing Engines:

• In order to burn fuel, an engine that breathes air from its surroundings is said to be "air-breathing."
• All practical internal combustion engines for air breathing directly heat the air by burning fuel, and the hot gases that are produced are then employed for propulsion through a propelling nozzle.
• Air is continuously pumped via the air-breathing engine. Compressed air is combined with gasoline, ignited, and released as exhaust gas.
• A typical air-breathing engine produces thrust that is around eight times larger than its weight.
• The working gases are ejected from the exhaust nozzle, producing the thrust.

Types:

• Ramjet: Ramjets are a type of air-breathing jet engine that compresses incoming air for combustion without the use of a revolving compressor.
• Scramjet: Compared to ramjet engines, scramjet engines work more effectively at hypersonic speeds and enable supersonic combustion.

Ramjet vs. Scramjet: Differences

• Ramjets with supersonic combustion are known as scramjets. Ordinary ramjets slow the air to subsonic speeds prior to combustion, while a scramjet does not do this.
• Ramjets have a theoretical velocity range of 1 to 6 Mach, while Scramjets have a theoretical range of 12 to 24 Mach.
• Ramjets and scramjets require significant airflow to begin producing thrust; they are unable to do so at zero velocity.
• Ramjets don't have the same particular impulse as scramjets.
• Ramjet has more efficiency and operability due to subsonic combustion than Scramjet, which has a lower efficiency due to supersonic combustion.