India has issued a Notice to Airmen (NOTAM) for a possible launch of an experimental flight of India's new indigenously developed Hypersonic Test Demonstrator Vehicle (HSTDV) in the Bay of Bengal for the period between 28th and 29th June 2021 reported as per a tweet by @detresfa_. This is in addition to the NOTAM issued a couple of days back between for period between 23rd to 25th June 2021 speculated for the impending launch of  Nirbhay subsonic cruise missile.

Earlier, India on 7th Sept 2020 had successfully flight tested the locally hypersonic technology demonstrator vehicle (HSTDV) that is expected to power futuristic long-range missile systems and aerial platforms, officials said. The HSTDV, based on hypersonic propulsion technologies, has been developed by the Defence Research and Development Organisation (DRDO), they said.

People aware of the development said this test means that the DRDO will have the capacity to develop a hypersonic missile with scramjet engine in next five years, which will have the capacity to travel at more than two kilometres per second.

The hypersonic cruise vehicle was launched using a proven solid 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, which is nearly two kilometres per second, for more than 20 seconds. The critical events, like fuel injection and auto ignition of scramjet demonstrated technological maturity. The scramjet engine performed in a text book manner. At hypersonic speeds, the system has to handle very high fluctuating temperatures, as well as air speed, and thus, development of the material is one of the main challenges, among other complex technologies.

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