ISRO plans to conduct test flight of Scramjet

By Staff
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Google Oneindia News

Bangalore, Jun 28: Making a major stride towards future space transportation systems, the Indian Space Research Organisation is planning a test flight of an integrated Scramjet propulsion system in its quest to bring down the launch costs.

The integrated scramjet propulsion system, comprising air intake, combustor and nozzle, would be flight tested using a two stage sounding rocket.

In its ongoing research for supersonic combustion ramjet (SCRAMjet), ISRO had carried out a series of ground tests, realising a stable supersonic combustion for seven seconds with an inlet mach number of six (six times the speed of sound).

In the latest issue of SPACEINDIA of ISRO, Mr J D A Subramanyan, Project Director of Air Breathing Propulsion Project at the Thiruvananthapuram-based Vikram Sarabhai Space Centre, said advanced reusable launch vehicles with airbreathing propulsion would substantially reduce the cost of access to space, which was about 12,000 USD per kg for launch into near earth orbit. The cost could be brought down by reducing the vehicle size and recovering and reusing the hardware.

''More importantly, reducing propellant is imperative for low cost access to space as propellant forms about four fifth of launch vehicle mass at take off,'' he said, adding that it formed 78 per cent of the mass for space shuttles and 86 per cent for indigenous GSLV.

Mr Subramanyan said that by using air breathing propulsion, the need for carrying oxidiser could be minimised, if not eliminated, by drawing oxygen from the air. But since dense air was available only up to about 50 km altitude, the question arose regarding the extent of benefit of using air. However, three fourth of the propellant was consumed by the launch vehicle within this portion of flight, he said, citing the GSLV example which consumed 75 per cent of the propellant before it reached an altitude of 44 km. An air breathing launch vehicle could opt for off vertical trajectory and benefit more by using oxygen from the air.

Spacefaring nations were addressing the issues of air breathing propulsion for a quantum jump in the performance, compared to conventional rocket propulsion. Air breathing propulsion was the only feasible way for powered return flight, necessary for reusable launch vehicle to fly back to base, he added.

Referring to modern aircraft using turbojet air breathing engine for propulsion, Mr Subramanyan said these engines could not operate at flights above mach number of three. Such higher flight speeds could be achieved by RAMJET, which discarded the compressor turbine combination of turbo jets and used simple engine consisting of only air intake, combustion chamber and nozzle.

He said air breathing propulsion for launch vehicles envisaged a combination of propulsion cycles, turbojet engine, RAMJET engine, currently being used by missiles, scramjet engine and rocket engine.

They could either function as separate propulsion systems co-located or as a combined propulsion cycle engine by synergistically integrating them.

A variant, rocket-based combined cyle, which avoided the complex turbojet component where the rocket engine in its air augmented mode was used for low speed flight, was also gaining popularity, he added.

Mr Subramanyan said ISRO had flown a rocket for testing a combined cycle system for low speed regime of up to Mach number of 2.3. ISRO's success was demonstrated by stable supersonic combustion through a series of ground tests for an equivalent flight mach number of seven.

UNI

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