ISRO to conduct test flight of scramjet propulsion system

Bangalore, Jun 28 (UNI) 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 US Dollars 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 oxidisers 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.

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