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The hypersonic air-breathing scramjet technology was successfully demonstrated by the Defence Research and Development Organisation (DRDO)

HSTDV

• • It is an unmanned  scramjet demonstration aircraft that can travel at hypersonic speed   (Mach 6).
  • It uses hypersonic air-breathing scramjet technology.
• Hypersonic speeds are those which are five times or more than the speed of sound. 
• India became the fourth country to have demonstrated this technology after the USA, Russia and China
• Due to its high speed, most radars will be unable to detect it. It will also be able to penetrate most missile defence systems.
• It can be used to launch satellites at low cost & as a carrier vehicle for long range cruise missiles

Scramjet Engine

• • Air-breathing engines use oxygen from the atmosphere in the combustion of fuel. They include the turbojet, turboprop, ramjet, and pulse-jet.
  • Ramjet: 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. Ramjets work most efficiently at supersonic speeds but they are not efficient at hypersonic speeds.
• Vehicles that fly at supersonic speeds are flying faster than the speed of sound.
• Scramjet: A scramjet engine is an improvement over the ramjet engine as it efficiently operates at hypersonic speeds and allows supersonic combustion.

Reference:

1. https://www.thehindu.com/news/national/drdo-successfully-tests-hypersonic-technology-demonstrator-vehicle/article32541422.ece