Context: The Defence Research and Development Organisation (DRDO) recently successfully flight tested the Hypersonic Technology Demonstrator Vehicle (HSTDV) – an unmanned scramjet vehicle with a capability to travel at six times the speed of sound, making India the fourth country in the world after the US, China and Russia to develop such technology. 


  • The test was conducted using the Agni missile. A solid rocket motor of Agni missile was used to take to an altitude of 30 kilometers where the cruise vehicle separated from the launch vehicle and the air intake opened as planned. 
  • (Just for understanding!) On the D-day, a launch vehicle, which was derived from Agni 1 missile, rose from its launch pad in Odisha, carrying the HSTDV. 
  • The Agni 1 booster climbed to a height of 30 km in 12 seconds at a speed of Mach 5.6. 
  • When the launch vehicle reached an altitude of 30 km, the air intake ducts in the scramjet engine opened just before the launch vehicle separated smoothly. 
  • At 30 km altitude, the cruise vehicle’s nose cone split in two and fell off. Besides, the heat shield covering the cruiser was jettisoned. All these events took place in micro seconds.
  • Air from the atmosphere was then rammed into the scramjet engine’s combustion chamber at a supersonic speed. 
  • The air mixed with the atomised fuel, the fuel was ignited and the scramjet engine revved into action. 
  • The HSTDV flew for the next 20 seconds at a hypersonic speed of Mach six and fell 40 km away in the Bay of Bengal. The mission was a success.

Indigenous technology

  • The centrepiece of the HSTDV was the indigenously developed air-breathing scramjet engine, which formed the HSTDV’s propulsion system. If the mission’s aim was to prove this scramjet engine in flight, it was achieved.
  • In a scramjet engine, air from the atmosphere is rammed into the engine’s combustion chamber at a supersonic speed of more than Mach two. 
  • In the chamber, the air mixes with the fuel to ignite a supersonic combustion but the cruiser’s flight will be at a hypersonic speed of Mach six to seven. So, it is called supersonic combustion ramjet or Scramjet.


  • This successful test will pave the way for missiles that can travel at six times the speed of sound. 
  • Apart from being used as a vehicle for hypersonic and long-range cruise missiles, the HSTDV is a dual-use technology that will have multiple civilian applications, including the launch of small satellites at low cost. 
  • Mastering the air-breathing scramjet technology will lead to the development of hypersonic missiles, faster civilian air transportation and facilities for putting satellites into orbit at a low cost.

The hypersonic vehicle and its scramjet engine

  • The scramjets are a variant of a category of jet engines called the air breathing engines. 
  • The ability of engines to handle airflows of speeds in multiples of speed of sound, gives it a capability of operating at those speeds.
  • Hypersonic speeds are those which are five times or more than the speed of sound (Mach 5 or more). 

Hypersonic nuclear missiles

  • Hypersonic missiles travel at speeds faster than 3,800 miles per hour or 6,115 km per hour, much faster than other ballistic and cruise missiles. 
  • They can deliver conventional or nuclear payloads within minutes.
  • They are highly manoeuvrable and do not follow a predictable arc as they travel.
  • They are said to combine the speed of ballistic missiles with the manoeuvring capabilities of cruise missiles. 
  • The speed makes them hard to track compared to traditional missile tech.
  • In March this year, the United States announced it had successfully tested an unarmed prototype of a hypersonic missile.