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ISRO Successfully Test Fires Scramjet Engine
Aug 29, 2016

On August 28, The Indian Space Research Organisation (ISRO) conducted a 5-minute flight to test a scramjet engine, which takes atmospheric oxygen to burn engine fuel, developed at the Satish Dhawan Space Centre (SDSC), Sriharikota.

  • The engine will eventually be used to power its Reusable Launch Vehicle (RLV) at hypersonic speed.
  • During the experiment in SDSC, the scramjet engine, affixed to a two-stage RH-560 sounding rocket developed in the 1970s, was ignited at an altitude of 20 km and allowed to burn fuel for five seconds before the rocket falls into the Bay of Bengal.
  • The engine successfully test-fired its futuristic scramjet rocket engine using oxygen from the atmosphere that could cut the cost of the launches several fold and help in ISRO’s bid to design advanced air breathing engines.
  • The mission is a modest yet important milestone in ISRO’s bid to design and develop advanced air breathing engines, including ones for its future space transport system.
  • After a smooth countdown of 12 hours, the solid rocket-booster Advanced Technology Vehicle (ATV) carrying the scramjet engines lifted off at 6 a.m. and ending a 300 second-flight, touched down in the Bay of Bengal, about 320 km from Sriharikota.
  • The important flight events—burn out of booster rocket stage, ignition of second stage solid rocket, functioning of scramjet engines for 5 seconds followed by burn out of the second stage—took place exactly as planned.
  • The vehicle was successfully tracked during its flight from the ground stations at Sriharikota.
  • It is the maiden short duration experimental test of Scramjet engine with a hypersonic flight at Mach 6, and the ATV, an advanced sounding rocket carrying the engines engines, weighed 3277 kg at lift-off.
  • With this flight, critical technologies such as ignition of air breathing engines at supersonic speed, holding the flame at supersonic speed, air intake mechanism and fuel injection systems have been successfully demonstrated.
  • Scramjet engine designed by ISRO uses hydrogen as fuel and the oxygen from the atmospheric air as the oxidiser. Usually rocket engines carry both fuel and oxidiser on board for combustion, but these newly developed engines with air-breathing propulsion system will use oxygen from the atmosphere thereby reducing the lift-off mass of the vehicle.
  • It will also help in bring down launch costs substantially.
  • ATV is a two-stage spin stabilised launcher with identical solid motors (based on Rohini RH560 sounding rocket) as the first as well as the second stage (booster and sustainer).
  • The twin scramjet engines were mounted on the back of the second stage. Once the second stage reached the desired conditions for engine start-up, necessary actions were initiated to ignite the Scramjet engines and they functioned for about 5 seconds.
  • This ATV flight operations were based on a pre-programmed sequence. The ignition of the engine, the building up of pressure and the duration for which the engine can sustain the flame was tested and monitored

While many countries like Japan, China, Russia and Europe are in the initial or testing phase of supersonic combustor technology, NASA demonstrated scramjet propulsion in 2004. ISRO had previously carried out a ground test of a scramjet engine in 2006.

Advantages of Scramjet Engine?

  • It  does not have to carry its own oxygen, rather Scramjet picks oxygen from the atmosphere.
  • Since, there are no rotating parts it is easier to manufacture than a jet engine.
  • Scramjet has a higher specific impulse (change in momentum per unit of propellant expelled) than a conventional engine. Specific impulse is a way to describe the efficiency of rocket and jet engines. It represents the impulse (change in momentum) per unit amount of propellant used and its units are in seconds. Scramjets have specific impulse of 1,000 to 4,000 seconds, whereas rockets have about 450 seconds. The higher the specific impulse the greater the push generated by the same amount of fuel
  • Since a scramjet carries no oxidizer tanks, it can be much lighter, faster, and ultimately cheaper than conventional rocket technology.
  • Its only exhaust is water, released from combining hydrogen, the fuel, with oxygen, the oxidizer, and it needn't discard massive empty tanks as conventional rocket do.

How does Scramjet Engine Works?

Unlike a typical jet engine, such as a turbojet, a scramjet does not use rotating, fan-like components to compress the air; rather, the achievable speed of the aircraft moving through the atmosphere causes the air to compress within the nozzle. In fact, no moving parts are needed in a scramjet, which greatly simplifies both the design and operation of the engine. In comparison, typical turbojet engines require inlet fans, multiple stages of rotating compressor fans, and multiple rotating turbine stages, all of which add weight, complexity, and a greater number of failure points to the engine. It is this simplicity that allows scramjets to operate at such high velocities, as the conditions encountered in hypersonic flight severely hamper the operation of conventional turbo machinery.Scramjet engines do not decelerate the flow of incoming air to subsonic velocities. A scramjet combustor is supersonic: the inlet decelerates the flow to a lower Mach number for combustion, after which it is accelerated to an even higher Mach number through the nozzle. By limiting the amount of deceleration, temperatures within the engine are kept at a tolerable level, from both a material and combustive standpoint. Even so, current scramjet technology requires the use of high-energy fuels and active cooling schemes to maintain sustained operation, often using hydrogen and regenerative cooling, a cooling technique used in space rockets.

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