India successfully flight-tested the indigenously-developed hypersonic technology demonstration vehicle (HSTDV) from APJ Abdul Kalam launch complex at Wheeler Island, off the coast of Odisha on September 7.

The HSTDV, based on hypersonic propulsion technologies and developed by the Defence Research and Development Organisation (DRDO), will help India develop futuristic space assets like long-range missile systems and aerial platforms. Only a very few countries like the US, Russia and China have such a capability.

The maiden test was conducted on June 12, 2019. However, it did not provide expected results.

With the testflight on September 7, the defence ministry said all the performance parameters have indicated a resounding success of the mission.

What are the features of HSTDV?

The HSTDV is capable of powering missiles to attain a speed of around Mach 6 or six times the speed of sound. It can move up to an altitude of 32.5 km in 20 seconds.

The HSTDV operates on a scramjet engine, as against the ramjet engine which is used on most missiles. The ramjet engines operate at supersonic speeds of up to Mach 3.

Besides its utility for long-range cruise missiles of the future, the dual-use technology will have multiple civilian applications also. 

It can be used for launching satellites at low cost. 

Highlights of the test flight

The hypersonic cruise vehicle was launched using a proven rocket motor, which took it to an altitude of 30 kilometres where the aerodynamic heat shields were separated.

The cruise vehicle separated from the launch vehicle and the air intake opened as planned. The hypersonic combustion sustained and the cruise vehicle continued on its desired flight path at a velocity of six times the speed of sound.

The critical events like fuel injection and auto ignition of scramjet demonstrated technological maturity and that the scramjet engine performed in a textbook manner.

The parameters of launch and cruise vehicle, including the scramjet engine, were monitored by multiple tracking radars, electro-optical systems and telemetry stations.

The scramjet engine worked at high dynamic pressure and very high temperature. A ship was also deployed in the Bay of Bengal to monitor the performance during the cruise phase of hypersonic vehicle.

With the successful test, many critical technologies such as aerodynamic configuration for hypersonic manoeuvres, use of scramjet propulsion for ignition and sustained combustion at hypersonic were proven and validated.

What is scramjet?

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. Fuel is injected in the combustion chamber where it mixes with the hot compressed air and ignites. 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.

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 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. 

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.

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