India achieved the distinction of successfully launching an indigenously developed hypersonic technology demonstrator vehicle powered by a scramjet engine, which will serve as a critical building block for next-generation hypersonic cruise missiles. India’s Defence Research and Development Organisation (DRDO), which had developed it, described it as a major technological breakthrough. The air-breathing scramjet engine was successfully flight-tested at hypersonic speed within the atmosphere, meeting all technical parameters. The test also paves the way for development of many more critical technologies, materials and hypersonic vehicles. In the next phase, DRDO hopes to develop long-range hypersonic cruise missiles in five to six years.
When a projectile reaches a speed faster than Mach 5; that is, 5 times the speed of sound, it is said to travel at hypersonic speed. As of now, only the US, Russia and China comprise an extremely exclusive hypersonic club with the capability of developing hypersonic missiles. Now, India becomes the fourth member of that exclusive club.
In the Indian test, carried out from the Dr. Abdul Kalam Island off the Odisha coast, on Bay of Bengal, the hypersonic cruise vehicle sustained its scramjet-powered flight path at a velocity of Mach 6 for 22-24 seconds. The parameters of the launch and cruise vehicles were continuously monitored by multiple tracking radars, electro-optical systems and telemetry stations. A ship was also deployed in the Bay of Bengal to monitor the performance during the cruise phase of the hypersonic vehicle. All the performance parameters have indicated a resounding success of the mission.
Although it is a big achievement, India still has to achieve sustained scramjet-powered hypersonic flight for a few minutes, which has been demonstrated by the US, Russia and China. In fact, the three countries are way ahead in the race to develop aerodynamically manoeuvrable hypersonic weapons that can defeat enemy missile defence systems.
The Indian armed forces already have the ramjet-powered BrahMos supersonic cruise missiles, developed jointly with Russia, which fly at a speed of Mach 2.8. A ramjet is a form of air-breathing jet engine that uses the engine’s forward motion to compress incoming air without an axial compressor or a centrifugal compressor. A supersonic combustion ramjet, or scramjet, also relies on high vehicle speed to compress the incoming air forcefully before combustion. Whereas, a ramjet decelerates the air to subsonic velocities before combustion, the airflow in a scramjet remains supersonic throughout.
Ramjets work most efficiently at supersonic speeds around Mach 3 and can operate up to speeds of Mach 6. However, the ramjet efficiency starts to drop when the vehicle reaches hypersonic speeds. On the other hand, a scramjet efficiently operates at hypersonic speeds and allows supersonic combustion.
The complex technology behind the hypersonic test demonstration vehicle also has civilian applications like low-cost launching of small satellites. Today, satellites are launched into orbit by multi-staged satellite launch vehicles that can be used only once and are therefore expensive. Also, their efficiency is low because they can carry only 2-4% of their lift-off mass to orbit. Moreover, nearly 70% of the propellant carried by today’s launch vehicles consists of oxidiser that provides oxygen for combustion. Therefore, the cost of placing a satellite in orbit can be substantially reduced if the next generation launch vehicles use a propulsion system that can utilise the atmospheric oxygen during their flight through the atmosphere. Scramjet-powered launch vehicles can achieve that.
Script: Biman Basu, Sr. Science Commentator